Agustin, R.M. et al.

Anszperger, J. et al.

Bedrossian, N.S. et al.

Bernstein, J. et al.

Borenstein, J.T. et al.

Chaudhry, A.I. et al.

Elwell, J.

Hall, W.D. et al.

Kourepenis, A.

Kwan, A. et al.

Nazarenko, A.I. et al.

Oh, J. et. al.

Schwartz, G. et al.

Shenai, S. et al.

Sitomer, J. et al.

Stoll, J.C. et al.

Vytal, J.J.

Weinberg, M.S.

Agustin, R.M.; Mangoubi, R.S.; Hain, R.M.; Adams, N.J.

Robust Failure Detection for Reentry Vehicle Attitude Control Systems

Journal of Guidance Control and Dynamics, Vol. 22, No. 6, Nov-Dec, 1999, pp. 839-845. (Draper Report no. P-3624-REV-B)

Abstract: This paper presents a robust failure detection methodology for the attitude control system of reusable launch vehicles (RLVs). In particular, we consider the problem of estimating the thrust from multiple jets firing from an RLV reaction control system (RCS), as well as the related problem of distinguishing between failures in the RCS and the aerosurfaces. For accurately known vehicle and sensor models, the Kalman filter provides the optimal estimate for the jet thrust in the least-squares sense. During reentry, however, plant model uncertainties are a major problem for such a filter, as the vehicle's aerodynamics vary widely with rapidly changing Mach number, making gain scheduling impractical. Consequently, the Kalman filter's performance degrades. Even if the Mach number were known accurately, rapid gain scheduling may not be desirable or even possible, because of the large data storage requirements it entails. Transient, robust H-infinity or game-theoretic filters are proposed for next-generation RLVs, and a prototype design is demonstrated for the Space Shuttle Orbiter's attitude determination system. Simulation results demonstrate that the robust filters can be insensitive to plant model uncertainties over a much wider range of Mach numbers than a traditional Kalman filter, while remaining sensitive to failures in the aerosurfaces and the RCS jets.

Subjects: ROBUST FAILURE DETECTION AND ISOLATION (RFDI), ATTITUDE CONTROL SYSTEMS, REUSABLE LAUNCH VEHICLES, REACTION CONTROL SYSTEMS (RCS), KALMAN FILTERING, ORBITER SPACECRAFT, FAILURE ANALYSIS, REENTRY VEHICLES, ROBUSTNESS (MATHEMATICS), COMPUTER SIMULATION

Anderson, J.M.; Parry, J.R.; Prestero, M.G.

Vorticity Control Propulsion and Maneuvering: an Enabler of Unique Asymmetric UUV Missions

Submarine Technology Symposium. Held at Johns Hopkins University (JHU), MD, 05/11/1999 to 05/13/1999. Sponsored by: JHU Applied Physics Laboratory (APL). (Draper Report no. P-3727)

Abstract: Analysis and experiments by M. Triantafyllou and others at the Massachusetts Institute of Technology (MIT) and elsewhere indicated that vorticity control (VC)-based propulsion and maneuvering concepts (employing fish-like motions to move man-made vehicles) offer the potential for high propulsion efficiency, exceptional maneuvering capability, and improved stealth for unmanned undersea vehicle warfare missions. Subsequent development at Draper Laboratory of a prototype vehicle using VC propulsion and maneuvering has reached the point of demonstrating the feasibility of this method of propulsion and has given initial confirmation of the potential for improved propulsion efficiency and maneuverability. In particular, experiments have shown the ability to operate continuously in a circle one-vehicle length in diameter and the ability to turn in three-quarters of a body length or less. Screw propellers and jet pumps are proven underwater vehicle propulsion methods. These, combined with lifting surfaces and thrusters, provide traditional maneuvering capabilities. They have, however, severe performance limitations when looked at over the range of potentially required speed capability and maneuverability for a number of future missions. The strength of VC propulsion and maneuvering lies in exactly these areas of weakness: operations in surf and very shallow water zones or in high current gradients, demanding the ability to exert virtually instantaneous high maneuvering forces in any direction. Such capabilities will enable in-shore surveillance, reconnaissance, and other covert missions that cannot now be accomplished, and expand the reach of submarines into areas that make them a truly asymmetric threat.

Subjects: VORTICITY CONTROL UNMANNED UNDERSEA VEHICLE (VCUUV), ASYMMETRY, VORTICITY CONTROL PROPULSION, MANEUVERABILITY

Anderson, J.M.; Kerrebrock, P.A.

The Vorticity Control Unmanned Undersea Vehicle (VCUUV) Performance Results

International Symposium on Unmanned Untethered Submersible Technology. 11th. Held in Durham, NH, 08/23/1999 to 08/25/1999. Sponsored by: AUSI. (Draper Report no. P-3747)

Abstract: The Vorticity Control Unmanned Undersea Vehicle (VCUUV) at Draper Laboratory is the first mission-scale, autonomous underwater vehicle that uses vorticity control propulsion and maneuvering. The VCUUV is a self-contained free-swimming research vehicle, that follows the morphology and swimming motion of a yellowfin tuna. A rigid pressure hull comprises the forward half of the vehicle, which houses batteries, electronics, ballast, and a hydraulic power unit. The aft section is a freely-flooded articulated robot tail that is terminated with a lunate caudal fin. Utilizing tail kinematic data from the MIT Robotuna, the VCUUV has demonstrated stable steady swimming up to 2.4 kn and aggressive maneuvering trajectories with turning rates up to 75 deg/s. This paper summarizes the vehicle integration, field experiments, and performance results of this novel vehicle propulsion study.

Subjects: VORTICITY CONTROL UNMANNED UNDERSEA VEHICLE (VCUUV), AUTONOMOUS UNDERWATER VEHICLES, UNDERWATER PROPULSION

Anszperger, J.; Silver, L.; Satlow, F.; Hermanson, J.

Testing Environment for the GPS Space and Control Segments

Joint Services Data Exchange (JSDE). Held in Norfolk, VA, 11/15/1999 to 11/19/1999. (Draper Report no. P-3784)

Abstract: The GPS satellite constellation is controlled by ground-based facilities collectively known as the Operational Control Segment (OCS) (Figure 1). The OCS includes a central Master Control Station (MCS) located at Schriever APB, CO, a backup MCS (BUMCS) located in Gaithersburg, MD, and a number of geographically dispersed Ground Antennas (GAs) and Monitor Stations (MSs), also known as ground stations or remote sites. This paper describes the Telecommunication Simulator Test Station (TSTS), a relatively new facility located at Cape Canaveral Air Station (CCAS), Florida. The purpose of the TSTS is to provide a high-fidelity testing environment for new GPS satellite and OCS software releases, a facility for checkout of production satellites prior to launch, and testbeds for GA and MS hardware releases.

Subjects: GLOBAL POSITIONING SYSTEM (GPS), TELECOMMUNICATION SIMULATOR TEST STATION (TSTS)

Barton, G.H.; Tragesser, S.G.

Autonomous Intact Abort System for the X-34

Atmospheric Flight Mechanics. Held in Portland, OR, 08/09/1999-08/11/1999. Sponsored by: AIAA. (Draper Report no. P-3759)

Abstract: Autonomous algorithms are developed that provide trajectory guidance for horizontally landing vehicles such as the X-34 under a variety of abort conditions. The nominal guidance system of the X-34 is incapable of directing the vehicle to a safe landing for many possible situations in which trajectory is far away from nominal conditions (as in the case of an engine failure). To minimize the risk of losing the vehicle, the autonomous intact abort system considers multiple landing sites and redesigns certain guidance inputs in order to adapt to the new conditions presented by the abort. The abort system design is demonstrated in a high-fidelity simulation to prove the feasibility of the concept for various engine-out scenarios. These abort algorithms are being incorporated into the X-34 vehicle to flight test this new technology as a part of the Future-X Pathfinder Flight Demonstration Program.

Subject: X-34, ALGORITHMS, ABORT GUIDANCE, TRAJECTORY CONTROL

Barton, G.H.; Tragesser, S.G.

Autolanding Trajectory Design for the X-34

Atmospheric Flight Mechanics. Held in Portland, OR, 08/09/1999 to 08/11/99Sponsored by: AIAA. (Draper Report no. P-3758)

Abstract: An Autolanding I-load Program (ALIP) is developed to design unpowered autolanding trajectories for the X-34 Mach 8 vehicle. The trajectory comprises geometric flight segments that are based on the Shuttle approach and landing design (steep glideslope, circular flare, and exponential flare to shallow glideslope). Enforcing physical constraints such as loads, vertical descent rate, continuity, and smoothness reduces the design problem to a two-point boundary value problem with conditions on the initial and final dynamic pressure. Finding a solution required the development of trajectory simulation techniques that constrained the flight profile to a prescribed geometry. The design methodology can be extended beyond the autolanding flight regime by repeating the series of geometric segments and solving multiple two-point boundary values problems (one for each series). The techniques described in this paper facilitate the rapid design of reference trajectories.

Subject: X-34, TRAJECTORIES, AUTOLANDING I-LOAD PROGRAM (ALIP), TRAJECTORY SIMULATION

Bedrossian, N.S.; McCants, E.

Space Station Attitude Control during Payload Operations

Astrodynamics Specialist Conference. Held in Anchorage, AK, 08/16/1999 to 08/19/1999, pp. 1083-1094. Sponsored by: AAS/AIAA. (Draper Report no. P-3778)

Abstract: Evaluating the feasibility of planned robotic operations requires an analysis methodology and tools that can quickly assess proposed attitude control strategies. In this paper, an efficient approach to model the attitude dynamics of the Space Station during payload motion is presented. This formulation was then used to develop momentum optimal attitude command trajectories for the Space Station control moment gyroscope (CMG) attitude hold controller for use during robotic payload operations. This methodology was applied to a realistic Space Station assembly operation and compared with other alternatives. The results indicate that the optimized attitude command trajectory results in the smallest peak CMG momentum cost.

Subjects: INTERNATIONAL SPACE STATION (ISS), ATTITUDE CONTROL, SPACE STATION PAYLOADS, REMOTE MANIPULATOR SYSTEM (RMS), CONTROL MOMENT GYROSCOPES (CMG)

Bernstein, J.; Bottari, J.; Kirkos, G.

Advanced MEMS Ferroelectric Ultrasound 2D Arrays

IEEE Ultrasonics Symposium, 10/17/1999 to 10/21/1999 Sponsored by: IEEE. (Draper Report no. P-3769)

Abstract: This paper discusses the design of advanced micromachined ferroelectric ultrasound transducers for use at 3 MHz. 16 x 16 arrays of resonant monomorph sensors have been constructed with sol-gel lead zirconate titanate (PZT) as the active ferroelectric layer deposited on insulating layers of ZrO2 and SiO2. A novel in-plane polarization of the PZT is used to maximize sensitivity, while trading off reduced output capacitance to match the CMOS buffer electronics. This results in about 30 dB-improved sensitivity compared with conventional polarizing across the thickness of the PZT layer. Fluid-filled through wafer holes are used as an acoustic matching network to achieve resonance at both 1 and 3 MHz. A lumped element equivalent circuit model will be presented, as well as finite-element analysis showing frequency response and resonant gain. Performance predictions for projector efficiency and receive response are given. Test results are presented, including transmit response, receive sensitivity, and frequency response.

Subjects: MICROELECTROMECHANICAL SYSTEM (MEMS), FERROELECTRIC DEVICES, ULTRASOUND IMAGES

Bernstein, J.J.; Xu, B.M.; Ye, Y.H.; Cross, L.E.; Miller, R.

Dielectric Hysteresis from Transverse Electric Fields in Lead Zirconate Titanate Thin Films

Applied Physics Letters, Vol. 74, No. 23, 06/07/1999, pp. 3549-3551. (Draper Report no. P-3717)

Abstract: Excellent symmetric dielectric hysteresis is observed from lead zirconate titanate (PZT) thin films using transverse electric fields driven by interdigitated surface electrodes. The 1-micron-thick PZT films with a Zr/Ti ratio of 52/48 are prepared on ZrO2 buffered, 4-in-diameter silicon wafers with a thermally grown SiO2 layer. Both the ZrO2 buffer layer and PZT film are deposited by using a similar sol-gel processing. Remnant polarization of about 20 micro-C/cm2 with coercive field less than 40 kV/cm is obtained as measured using a triangle wave at 50 Hz. Thicker films are being developed, and retention for the transversely polarized state is currently under study. One of the objectives of this study is to develop a large array of d33-driven unimorph-sensing elements for a high-resolution acoustic imaging system.

Subjects: LEAD ZIRCONATE TITANATE (PZT), THIN FILMS, HYSTERESIS, ELECTRIC FIELDS, ACOUSTIC IMAGING

Bernstein, J.; Miller, R.; Kelley, W.; Ward, P.

Low-Noise MEMS Vibration Sensor for Geophysical Applications

Journal of Microelectromechanical Systems, Vol. 8, No. 4, 12/1999, pp. 433-438. (Draper Report no. P-3648-REV-A)

Abstract: The need exists for high-sensitivity, low-noise vibration sensors for various applications such as geophysical data collection, tracking vehicles, intrusion detectors, and underwater pressure gradient detection. In general, these sensors differ from classical accelerometers in that they require no dc response, but must have a very low noise floor over a required bandwidth. Theory indicates a capacitive micromachined silicon vibration sensor can have a noise floor on the order of 100 ng/ over a 1-kHz bandwidth while reducing size and weight tenfold compared with existing magnetic geophones. With early prototypes, we have demonstrated a Brownian-limited noise floor at 1.0 g/, orders of magnitude more sensitive than surface micromachined devices such as the industry standard ADXL05.

Subjects: CAPACITIVE SENSORS, SEMICONDUCTORS, GEOPHYSICAL FACTORS, MICROSENSORS, NOISE, SILICON, VIBRATION MEASUREMENT, BROWNIAN NOISE

Boccuzzi, R.; Brown, T.; Cook, B.; Dodds, L.; Kochocki, J.; LeBlanc, M.; Robillard, M.; Stadelmann, E.; Stewart, W.; O'Brien, W.; Hudson, P.; Bracewell, T.; Farmer, K.; Gaborno, N.; Kono, K.; Vassar, E.

A Simulation-Based Test and Evaluation Capability

Institute of Navigation National Technical Meeting. Held in San Diego, CA, 01/25/1999 to 01/27/1999, pp. 567-562.  (Draper Report no. P-3699)

Abstract: SiBaTEC, a Simulation-Based Test and Evaluation Capability, provides a user with the ability to perform real-time hardware-in-the-loop (HIL) simulations. For a system under investigation, SiBaTEC permits design verification, testing of potential components, and subsystem modifications before commitment to a prototype, and testing of modified prototypes in simulation. Furthermore, SiBaTEC provides a means of performing system surveillance through repeatable monitoring and margin testing of hardware and embedded software and hypothesis testing of potential aging and wear-out phenomena. SiBaTEC accomplishes these activities by means of a real-time simulation host supported by a network-based suite of tools, and custom input/output (I/O) capabilities. This paper describes these capabilities of SiBaTEC as well as the current system integration testing on a MK6 guidance system.

Subjects: SIMULATION-BASED TEST AND EVALUATION CAPABILITY (SIBaTEC), HARDWARE IN THE LOOP (HIL), MODELS (SIMULATIONS), DESIGN ENGINEERING, PROTOTYPES, TESTING AND EVALUATION, TRIDENT MK6

Boelitz, F.W.

Kistler Launch Assist Platform (LAP) Return Burn Control

Guidance, Navigation, and Control Conference. Held in Portland, OR, 08/09/1999 to 08/11/1999, pp.1289-1299. Sponsored by: AIAA. (Draper Report no. P-3740)

Abstract: The thrust vector control (TVC) design for the Return Burn segment of the Kistler K-1 Launch Assist Platform (LAP) is presented. The design features a two-mode controller that initially provides state-dependent preignition orientation of the rocket engine, and upon ignition, rapid orientation of the vehicle x-axis back toward the launch zone. Following this pitch reversal, the controller seamlessly switches to a second mode that features integral control with acceleration direction estimation. This second mode provides the fine pointing required by guidance to ballistically loft the LAP back to the launch zone. Control gains for the design are precomputed prior to launch through an automated design procedure that searches over a broad family of gains. The automated design tool simultaneously applies frequency domain and time domain constraints, which results in a controller that achieves stable response with adequate margin and minimal settling time.

Subjects: THRUST VECTOR CONTROL SYSTEMS, KISTLER K-1 VEHICLE, LAUNCH
ASSIST PLATFORM (LAP)

Borenstein, J.T.; Gerrish, N.D.; Currie, M.T.; Fitzgerald, E.A.

New Ultrahard Etch-Stop Layer for High-Precision Micromachining

Proceedings of the 1999 12th IEEE International Conference on Microelectromechanical Systems (MEMS) Orlando, FL, 01/17/99 to 01/21/99, pp. 205-210. (Draper Report no. P-3679)

Abstract: In this work, we describe a high-precision fabrication method for silicon micromachining based on a newly developed epitaxial etch stop. This etch stop, composed of a silicon-germanium ally with no boron doping, outperforms traditional boron-doped etch stops in several important and fundamental ways. Etch selectivities in a variety of standard etchants compare favorably with those obtained using high-concentration boron diffused and epitaxial layers. Microstructural analysis of the new etch-stop layer demonstrates a significant reduction in defect density relative to boron-doped counterparts. Tuning-fork gyroscopes built with the new etch-stop show build dimensions comparable to those fabricated with conventional methods. We propose a band structure model for the etch-stop mechanism that mimics the hole-injection phenomenon often invoked for boron doping, and conclude with a brief discussion of the advantages of this new fabrication technology.

Subjects: MICROELECTROMECHANICAL SYSTEM (MEMS), MICROMACHINING, ETCHING, SILICON, ALLOYS, GERMANIUM, ETCH BEHAVIOR, GYROSCOPES

Cantwell, R.H., Ventresca, R.

GPS Continuous Track on a Spinning Vehicle with Multiple Patch Antenna

International Technical Meeting of the Satellite Division of the Institute of Navigation (ION GPS). Held in Nashville, TN, 09/14/1999 to 09/17/1999, Sponsored by: ION (Draper Report no. P-3721)

Abstract: The objective is to use multiple patch antennas to allow visibility to the GPS satellite vehicles for continuous tracking on a spinning platform without going through the acquisition process. Our methodology is to use patch antennas mounted to allow overlapped visibility coverage of the GPS satellite vehicles. An inertial measurement unit (IMU) is used to determine the attitude and position or coverage of each antenna. Ephemeris is
collected from each visible satellite. Using the GPS receiver's position and the positions of the GPS satellite vehicles (SVs), the receiver determines which satellites are in the field of view (FOV) of each antenna. The overlapped coverage allows an SV to be acquired and tracked on two antennas. At this time, we do a direct track handover from the receiver channel whose antenna will be going out of view to another receiver channel using the antenna that has come into view. This eliminates interruption in signal tracking and thereby results in continuous, accurate navigation solutions. This technique has been demonstrated successfully on multiple spinning vehicles.

Subjects: ANTENNAS SPINNING (MOTION), INERTIAL MEASUREMENT UNIT (IMU), SATELLITE VEHICLES (SV), GLOBAL POSITIONING SYSTEM (GPS)

Cefola, P.J.; Nazarenko, A.I.; Yurasov, V.

Refinement of Satellite Ballistic Factors for the Estimation of Atmosphere Density Variations and Improved LEO Orbit Prediction

Space Flight Mechanics Meeting. Held in Breckenridge, CO, 02/07/1999 to 02/10/1999. Sponsored by: AAS/AIAA. (Draper Report no. P-3713)

Abstract: In an earlier work, Prof. Nazarenko discussed an atomosphere density tracking process that operates in parallel to the orbit determination process. This atmosphere density tracking process employs ballistic coefficient data observed over short arcs from multiple satellites. The process includes: (1) a procedure for constructing the density variations that operates on a 2- or 3-h grid, (2) a procedure for estimating the true ballistic coefficients of the employed satellites that operates on a 28- or 56-day interval (1 or 2 monthly solar cycles), and (3) procedure for forecasting the atmosphere density at future times. This paper focuses on the improvement of the algorithm for estimating the true ballistic coefficient of the employed satellites. The main aspect of this improvement consists of applying, for updating the ballistic factors of nonstandard satellites, a linear function of altitude to model the systematic errors. Numerical testing based on simulated data has been undertaken to verify the correctness of the algorithm. The products of the study include a proposal to work with the real data. The possibility of complex utilization of data from both NORAD and the Russian Space Surveillance System is discussed.

Subjects: LOW EARTH ORBIT (LEO), PREDICTIONS, DENSITY MEASUREMENT, BALLISTICS

Chaudhry, A.I.; Thele, J.D.; Kang, D.S.

High-Velocity Teleoperated Rover

Aerospace Defense Sensing Simulation and Controls (AeroSense). 13th. Held in Orlando, FL, 04/05/1999 to 04/09/1999. Sponsored by: SPIE. (Draper Report no. P-3719) 

Abstract: The High-Velocity Teleoperated rover (HVTR) is motivated by a goal to exceed human physical speed with small ground vehicles for operations in an urban environment. A typical small (man-packable) ground vehicle's speed tops out at 1-2 m/s (2-4 mph). Limited speed is attributed to real-time sensing and processing of the external environment. Low speed makes traversing multiple city blocks taxing on the patience of a human operator. Traversing around a block may take 10-20 min. Even with operator assistance, using video does not significantly increase the speed. This is due to the low perspective of the camera view and camera vibration in outdoor setting.

Subjects: HIGH-VELOCITY TELEOPERATED ROVER (HVTR), MICROROVER, UNMANNED VEHICLES, EXPLOSIVE ORDINANCE DISPOSAL (EOD)

Connelly, J.; Kourepenis, A.; Larsen, D.; Marinis, T.F.

Inertial MEMS Development for Space

International Conference on Integrated Micronanotechnology for Space Applications. 2nd. Held in Pasadena, CA, 04/11/1999 to 04/15/1999. (Draper Report no. P-3726)

Abstract: Micromachined silicon inertial sensors offer revolutionary improvements in cost, size, and reliability for guidance, navigation, and control. Inertial sensors represent an important segment of an emerging microelectromechanical systems (MEMS) technology, which combines semiconductor materials and processing to create integrated mechanical and electrical systems. Batch manufacturing techniques produce thousands of virtually identical MEMS devices, each a few square millimeters in size, enabling enabling inertial systems at a fraction of the cost, size, and power of any previous technology. Development of MEMS inertial instruments is driven by the high-volume, commercial market that targets modest performance applications at prices below $20 per axis. However, Draper Laboratory has developed higher-performance, multi-axis systems using commercial processes to ensure availability and affordability for lower-volume military and space applications. The performance of these new MEMS inertial systems is quickly approaching bias stability of 1 deg/h and scale-factor stability of 100 ppm over -40°C to +85°C. Radiation testing is now underway to evaluate response to predicted space environments. Future MEMS inertial systems will reflect a radical departure from the ways they have been conceived, fabricated, and tested in the past. New inertial devices have been incorporated enabling multi-axis measurement in a planar array and development is underway on a new wafer-scale process integrating sensors and application-specific integrated circuits (ASICs) to create complete systems on a chip. These higher performances, lower power, inertial microsystems will be ideally suited for many spaces applications. This paper addresses Draper's inertial MEMS designs, fabrication methods, instrument and performance progression, and development activities related to space applications. Space radiation issues for MEMS are discussed, expected environments are identified, and radiation testing of MEMS instruments is described. In addition, MEMS packaging development toward high-level multi-axis system integration is reviewed.

Subjects: MICROELECTROMECHANICAL SYSTEM (MEMS); INERTIAL SENSORS; GUIDANCE, NAVIGATION, AND CONTROL (GN&C); APPLICATION-SPECIFIC INTEGRATED CIRCUITS (ASIC)

Cunningham, B.T.; Regan, R.; Clapp, C.; Hildebrant, E.; Weinberg, M.; Williams, J.

Miniature Silicon Electronic Biological Assay Chip and Applications for Rapid Battlefield Diagnostics

Battlefield Biomedical Technologies. Held in Orlando, FL, 04/06/1999, pp. 26-34. Sponsored by: SPIE.

Aerospace Defense Sensing Simulation and Controls (AeroSense). 13th. Held in Orlando, FL, 04/05/1999 to 04/09/1999. Sponsored by: SPIE. (Draper Report no. P-3718)

Abstract: Assessing the medical condition of battlefield personnel requires the development of rapid, portable biological diagnostic assays for a wide variety of antigens and enzymes. Ideally, such a assay would be inexpensive, small, and require no added reagents while maintaining the sensitivity and accuracy of laboratory-based assays. In this work, a Microelectromechanical System (MEMS)-based biological assay sensor is presented that is expected to meet the above requirements. The sensor is a thin silicon membrane resonator (SMR) that registers a decrease in resonant frequency when mass is absorbed onto its surface. By coating the sensor surface with a monolayer of antibody, for example, we have detected the corresponding antigen with a detection resolution of 0.25 ng/ml in phosphate buffer solution. Micromachining techniques are being used to integrate many (64 elements on the first test chip) identical SMR sensors into a single silicon chip, which would be capable of simultaneously performing a wide variety of biomedical assays. The sensors require only a small printed circuit board and 8-V power supply to operate and provide a readout. This presentation will describe the operation of the SMR sensor, the fabrication of the sensor array, and initial test results using commercially-available animal immunoglobulins in laboratory-prepared test solutions.

Subjects: MICROELECTROMECHANICAL SYSTEM (MEMS), BIOSENSORS, IMMUNOASSAYS, BIOCHIPS, BATTLEFIELDS

Draim, J.E.; Cefola, P.; Proulx, R.; Larsen, D.; Granholm, G.R.

Elliptical Sun-Synchronous Orbits with Line of Apsides Lying In or Near the Equatorial Plane

Astrodynamics Specialist Conference. Held in Anchorage, AK, 8/16/1999 to 8/19/1999, pp. 183-205. Sponsored by: AAS/AIAA. (Draper Report no. P-3755)

Abstract: This paper explores the characteristics of retrograde, sun-synchronous elliptic orbits with line of apsides lying in or near the equatorial plane. Coverage plots for a five-satellite ring showing the number of satellites in view and elevation angle data versus latitude and local time are presented. Stability of the orbit is discussed. Also analyzed is the effect of the trapped radiation field environment (Van Allen Belts) on these orbits, as well as the exposure to damage by natural and man-made debris. A major advantage seen for these orbits is that they can be used to provide augmented earth coverage for a selected latitudinal zone and a selected time of day (for all longitudes). This feature should prove useful for nongeostationary satellite communications systems where increased capacity is needed during daytime peak-traffic hours in heavily populated latitude bands.

Subjects: ELLIPSO SATELLITES, SUN-SYNCHRONOUS ORBITS, APSIDES, EQUATORIAL ORBITS, ELLIPTICAL ORBITS

D'Souza, C.; Bogner, A.J.; Brand, T.; Tsukui, J.; Koyama, H.; Nakamura, T.

An Evaluation of the GPS Relative Navigation System for ETS-VII and HTV

AAS Guidance and Control Conference. 22nd. Held in Breckenridge, CO, 02/03/1999 to 02/07/1999. Sponsored by: AAS. (Draper Report no.P-3711)

Abstract: The Global Positioning Satellite (GPS) system is increasingly being used for spacecraft navigation. Not only is GPS being used in the traditional role of absolute navigation, but it is also playing a role in relative navigation, particularly for spacecraft rendezvous. Two such instances in which relative GPS navigation is playing a key role in spacecraft rendezvous are the Engineering Test Satellite 7 (ETS-VII) and the HII Transfer Vehicle (HTV). ETS-VII is a test satellite developed by the National Space Development Agency of Japan (NASDA) and is designed to test the performance of a relative GPS system. HTV is the Japanese resupply vehicle for the International Space Station (ISS) and is being developed by NASDA. As currently envisioned for HTV, the ISS will send its GPS measurement information over a radio frequency (RF) link to HTV, which will simultaneously take GPS measurements to the same satellites. The HTV will difference the GPS measurements in a filter to provide highly accurate relative position and velocity information. NASDA has selected relative GPS navigation to be used for the rendezvous from approximately 23 km from the ISS to 500 m, after which a laser sensor will be used to position the visiting vehicle for grappling by an ISS arm. The Charles Stark Draper Laboratory has evaluated the GPS relative navigation system for both ETS-VII and HTV. This paper will describe the testing methodology of the GPS relative navigation system that was used to confirm the tests carried out by Mitsubishi Electric Corporation (MELCO) under contract to NASDA. The testing methodology used by Draper involved the use of an RF satellite signal simulator. In addition to providing a description of the filter architecture, MELSO also provided the trajectory data to drive the satellite signal simulator. A Northern Telecommunications (NorTel) Satellite Signal Simulator (SSS) used the target and chaser vehicle trajectory information to create the RF signal that a GPS receiver would expect to experience along the trajectory. Measurement data, including pseudorange and delta range measurements were recorded from the GPS receiver, with each trajectory being run separately. The recorded data from the two trajectories were then processed in a filter. Proper merging of the measurement data in the relative navigation filter involved the synchronization of data from the two receivers. Only those measurements that were from common satellites were used in the filter. The measurement data from the target and the chaser GPS receiver were time-tagged with slightly different times. Therefore, in order to difference the measurements, they had to be brought to a common time. This was performed using linear interpolation, with the target measurement being the reference time. The filter was an 8-state linearized Kalman filter. The states included the three relative position states, three relative velocity states, a relative clock bias state, and a relative clock drift state. The position and velocity states were expressed in the Hill frame, which is a curvilinear, rotating frame. The filter dynamics for the position and velocity were described by the well-known Hill-Clohessy-Wiltshire equations. An evaluation was also performed as to whether using the position and velocity for the target and the chaser for the propagation would improve the navigation results and it was found to improve the results. However, the Hill-Clohessy-Wiltshire equations, which yield a closed-form state transition matrix (STM), were still used in the propagation of the covariance matrix. With the use of numerical integration for the state equations and the state transition matrix for the propagation of the covariance matrix, excellent filter performance was obtained. The relative position accuracy was better than 0.4 m and the relative velocity accuracy was better than 6 cm/s. During coasting periods of the trajectory, the velocity accuracy was better than 1 cm/s.

Subjects: GLOBAL POSITIONING SYSTEM (GPS); GUIDANCE, NAVIGATION, AND CONTROL (GN&C); SPACECRAFT MOTION; RECEIVERS

Elwell, J.

Inertial Navigation for the Urban Warrior

Digitization of the Battlespace. 4th. Held in Orlando, FL, 04/07/1999 to 04/08/1999, pp. 196-204. Sponsored by: SPIE.(Draper Report no. P-3716)

Abstract: Individual soldier geolocation in situations such as urban warfare where loss of Global Positioning System (GPS) track can impact mission success has become a critical problem. Concepts such as RF "time difference of arrival" and "dead reckoning" techniques have not demonstrated their ability to support navigation reliably inside buildings on their own. Inertial navigation is the only technology that operates independent of external assets. The advent of micromechanical inertial sensor technology has resulted in low-cost, very small, low-power navigation systems capable of fitting in a soldier's boot. A miniature navigator consisting of three micromechanical gyroscope and accelerometer packages, including supporting application-specific integrated circuit chips, and capable of operating in support of such a mission has been developed. However, because of accelerometer and gyroscope drift, navigating inertially over long time periods, using even the most precise and most expensive inertial sensors available today, remains close to impossible. Inertial augmentation techniques are therefore required, and the concept of personal inertial navigation systems aided by zero velocity updating of the accelerometers with each footfall has been examined and shown to be sufficient to determine the location of an individual soldier accurately within a large building complex after hours of operation. In addition to the accelerometer, updates of the gyro via zero attitude rate techniques also enhance position accuracy, as well as provide an attitude reference in support of soldier-carried targeting sensors.

Subjects: URBAN WARFARE, GLOBAL POSITIONING SYSTEM (GPS), INERTIAL NAVIGATION, MINIATURIZATION

Flueckiger, K.; Dowdle, J.

A High Antijam INS GPs Navigator

Association of Old Crows. Held in Adelphi, MD, 04/07/1999 to 04/08/1999. Sponsored by: NAVWAR. (Draper Report No. P-3728)

Abstract: Traditionally, integrated inertial and Global Positioning System (GPS) sensing has been used to provide accurate high-bandwidth navigation solutions. Algorithms designed to integrate these sensors have not used the full sensor data available in a centralized manner. The so-called loosely-coupled integration approach assumes that GPS provides a (low-bandwidth) Position, Velocity, and Time (PVT) solution to the navigation algorithm. Traditionally, tight integration approaches demand that GPS provide pseudorange and delta-range measurements. In contrast, the Deep Integration Algorithm, introduced here, uses raw in-phase and quadrature (I and Q) components from the GPS receiver's correlator outputs. By using this full information from the receiver hardware, analysis and hardware results indicate that the Deep Integration Algorithm will improve GPS jamming immunity significantly. A preliminary implementation of the Deep Integration Algorithm for a single SV has been embedded successfully within a commercial-off-the-shelf C/A receiver. Results indicate that the receiver loss-of-lock threshold can be extended by approximately 15 to 20 dB in a sustained jamming environment. Results from two dynamic scenarios are presented here: (1) a velocity step along the SV line-of-sight, and (2) a tactical munition scenario. Both scenarios are presented under a variety of jamming environments. The results are extrapolated to predict the performance of the Deep Integration Algorithm, with full multi-SV tracking capability, using P(Y)-code receiver hardware. This analysis is consistent with performance predictions based on (software-only) simulation.

Subjects: INERTIAL NAVIGATION SYSTEMS (INS), GLOBAL POSITIONING SYSTEM (GPS), ANTIJAMMING, MILITARY APPLICATIONS, COMMERCIAL APPLICATIONS

Fuhry, D.

Adaptive Atmospheric Reentry Guidance for the Kistler K-1 Orbital Vehicle

Guidance, Navigation, and Control Conference. Held in Portland, OR, 08/09/1999 to 08/11/1999, pp. 1275-1288. Sponsored by: AIAA. (Draper Report no. P-3738)

Abstract: The Kistler K-1 is designed to be a fully-reusable, two-stage launch vehicle for economical delivery of small satellite payloads to low earth orbit. Greatest efficiency and hence lowest cost are achieved by flyback of both vehicle stages to the near vicinity of the launch site. After deploying the payload and performing necessary phasing maneuvers, the second-stage Orbital Vehicle (OV) performs a deorbit burn to achieve the desired trajectory conditions at atmospheric entry. After entering the atmospheric, the OV is steered aerodynamically until reaching the deployment point for a stabilization parachute. Subsequently, drogue and main parachutes complete deceleration of the vehicle for landing on airbags. This paper presents the design of an atmospheric guidance algorithm for bank-to-turn steering of the OV prior to deployment of the stabilization parachute. Reentry guidance targets a desired geographic position for deployment of the drogue parachute. The algorithm employs a numerical predictor/corrector technique to compute the bank angle and the start time of a single bank reversal required to null the predicted target position miss. Aerodynamic loads and heating are limited implicitly by selection of deorbit target conditions for reentry trajectory shaping. Results obtained using the Draper Laboratory K-1 Integrated Vehicle Simulation illustrates guidance performance under nominal and dispersed conditions.

Subjects: KISTLER K-1 VEHICLE, REUSABLE LAUNCH VEHICLES, ALGORITHMS, STEERING, REENTRY GUIDANCE

Granholm, G.R.; Proulz, R.J.; Cefola, P.J.

Orbit Determination for Medium Altitude Orbits Using GPS Receivers and Ground-Based Tracking

Astrodynamics Specialist Conference. Held in Anchorage, AK, 08/16/1999 to 08/19/1999, pp. 401-420. Sponsored by: AAS/AIAA. (Draper Report no. 3760)

Abstract: The past few years have seen a proliferation of nontraditional medium or high-altitude constellations designed for use in communications. A constellation considered for use in the Ellipso system features 10 satellites in highly elliptical sun-synchronous frozen line of apsides (SSFLA) orbits. These orbits pose unique challenges to the orbit determination process, including high eccentricity, tesseral resonance, critical inclination, and sensitivity to solar radiation pressure. This paper will compare the effectiveness of GPS-based tracking with ground-based tracking in terms of accuracy of differential correction (DC) solutions. A "Truth" orbit will be simulated using a high-precision Cowell numerical integrator. This orbit is then used to create simulated GPS pseudoranges and ground-based Doppler range and range-rate measurements. The GPS constellation is modeled and propagated using analytic J2-only equations expressed in equinoctial elements. To improve speed and performance, the GPS simulation is coded using a message-passing interface (MPI) parallel implementation. The pseudoranges and range/range-rate observations are used in a least-square DC process to solve for state parameters, solar radiation and drag coefficients, and ground station biases. Differences between the touch and fit/predict orbits are analyzed numerically and graphically. Cases are run for both atmospherically quiet and perturbed epochs and with atmospheric and gravitational mismodeling. It is found that the accuracy of the solution is strongly affected by atmospheric conditions. Both methods yield similar solutions, but the dc process scan requires more ground-based observations than GPS pseudoranges. Overall, both tracking methods are shown to be viable for these types of orbits.

Subjects: ORBIT DETERMINATION, ORBITAL ALTITUDE, GPS RECEIVER INTERFACE PROCESSOR (GRIPS), GROUND-BASED SURVEILLANCE AND TRACKING SYSTEM (GSTS), ELLIPSO SATELLITES, APSIDES

Guinon, W.; Setterlund, R.H.; Phillips, R.

Reducing the Power Requirements of an Interferometric GPS Receiver for Spacecraft Attitude Determination

Vision 2010: Present and Future: National Technical Meeting. Held in San Diego, CA, 01/25/1999 to 01/27/1999, pp. 561-573. Sponsored by: ION. (Draper Report no. P-3706)

Abstract: The ongoing development of micromechanical inertial systems that require very little power suggests the concomitant development of a low-power GPS receiver. The combination of such an interferometric receiver with inertial instruments would fill the need for a low-cost, lightweight, low-power attitude determination system for use in small, low-cost satellites with modest accuracy requirements (0.1 to 0.5 deg.). Power consumption by the GPS receiver can be reduced by turning off the RF front end, the frequency synthesizer, the reference oscillator and the digitizer for brief intervals of time while using the inertial system to maintain adequate attitude knowledge and to simplify obtaining subsequent IGPS attitude updates without time-consuming integer ambiguity resolution. This study looks at the implications of this strategy on the details of the receiver operation and design, including reacquisition, and the trade between pre- and post-detection integration, as well as power consumption. The accuracy of such a system as a function of the interval between GPS measurements was assessed. Depending on this interval and on other parameters such as inertial measurement unit (IMU) quality, antenna baseline, etc., system power consumption on the order of 1 W or less can be achieved. Accuracies in the 0.1- to 0.5-deg regime are readily achievable. Volume, weight, and power projections are based on existing technology and hardware, leading to a system concept for a spacecraft attitude determination that could be of enormous benefit for small satellites.

Subjects: GLOBAL POSITIONING SYSTEM (GPS), RECEIVERS, SPACECRAFT, ATTITUDE DETERMINATION, POWER REQUIREMENTS

Hall, W.D.; Odoni, A.R.

A New Airport Capacity Allocation Method and Its Simulation Through Optimization

Date: 9/28/1999. (Draper Report no. P-3764)

Abstract: This paper describes the Arrival-Departure Capacity Allocation Method (ADCAM), a new approach to airport capacity allocation that accounts for airport arrival capacity, departure capacity, and the interactions between arrivals and departures. ADCAM provides the users of the Air Transportation System with additional flexibility during periods when airport capacity is insufficient to serve demand without delay, and it improves the ability of the airlines and air traffic management to predict and manage the outcome of such situations. Implementation of new procedures in the air transportation system is an expensive endeavor. This expense must be justified by tangible benefits, which can be difficult to determine analytically before the procedure change has been implemented. Indeed, even after a procedural change, it is extremely difficult to assess its impact because of the lack of controlled experimental conditions. The benefit of the arrival-departure capacity allocation method is assessed here through simulation. A unique feature of the simulation is that optimization is used to model the response of an airline to air traffic flow management. The simulation is able to assess not only traditional measures of system performance such as airport throughput and passenger-minutes of delay, it also measures the value to the airlines of their realized plans. Using the simulation, one can compare the airlines' optimal solutions under ADCAM to those under the current method of allocating airport capacity, answering the question: "How much better could the airlines operate under ADCAM?" The simulation results suggest that operations under ADCAM would be more predictable than they are today, that the airlines could save considerable amounts of money, that airline service would improve, that fuel would be saved and hazardous emissions reduced.

Subjects: AIRPORT CAPACITY, ARRIVAL-DEPARTURE CAPACITY ALLOCATION METHOD (ADCAM), OPTIMIZATION, MODELS (SIMULATIONS)

Hammett, R.

Fault-Tolerant I/O Networks Applied to Ship Control

Ship Control Systems Symposium. 12th. Held in The Hague, Netherlands, 10/19/1999 to 10/21/1999. Sponsored by: SCS. (Draper Report no. P-3741)

Abstract: Future ships will require sophisticated onboard control systems to control machinery, automate tasks, optimize subsystem performance, and simplify maintenance. These controls will exploit the availability of inexpensive computer processing, will use many sensors and actuation devices, and will provide for completely integrated and coordinated control of all subsystems. The crew's increased reliance on these automated functions makes it essential that they provide dependable operation despite equipment failure or battle damage, e.g., they must be fault tolerant and damage survivable. An example of such a system is the U.S. Navy Seawolf submarine ship control. But the redundant sensors and actuation system used on Seawolf, with their associated electronics and wiring, must be made more compact and affordable for the approach to find widespread use on future ships. This paper describes how the use of data buses, intelligent sensors, and fault-masking actuation electronics can be used to construct input/output (I/O) networks that provide flexibility and growth, and that are highly dependable, affordable, and easily installed. These I/O networks can make widespread use of fault- and damage-tolerant systems practical. The use of I/O networks complements other efforts to make greater use of electrical actuation aboard ships. This paper explores the requirements for such systems and examines some of the technology trade-off that must be made, such as network media type (i.e., optical fiber, wired, or wireless), power distribution to network electronics, network topology (ring or bus), network size vs. speed, distributed vs. centralized I/O processing, and cross connections between I/O channels. The paper concludes by describing a concept for a fault-tolerant network I/O system and discussing the steps needed to develop such systems for future ships.

Subjects: FAULT-TOLERANT PROCESSORS, INPUT/OUTPUT PROCESSING, SHIP CONTROL SYSTEMS, SEAWOLF SHIP CONTROL SYSTEM

Hammett, R.C.

Ultrareliable Real-Time Control Systems-Future Trends

IEEE Aerospace and Electronic Systems Magazine, Vol.14, No. 8, 08/1999, pp. 31-6. (Draper Report No. CSDL-99-008-REV-A)

Abstract: Today's aircraft use ultrareliable real-time controls for demanding functions such as Fly-By-Wire (FBW) flight control. Future aircraft, spacecraft, and other vehicles will require greater use of these types of controls for functions that currently are allowed to fail, fail to degraded operation, or require human intervention in response to failure. Fully automated and autonomous functions will require ultrareliable control. But ultrareliable systems are very expensive to design and require large amounts of onboard equipment. This paper will discuss how the use of low-cost sensors with digital outputs, digitally commanded fault-tolerant actuation devices, and interconnecting networks of low-cost data buses offer the promise of more affordable ultrareliable systems. Specific technologies and concepts to be discussed include low-cost automotive and industrial data buses, "smart" actuation devices with integral fault masking capabilities, management of redundant sensors, and the fault detection and diagnosis of the data network. The advantages of integrating the control and distribution of electrical power with the control system will be illustrated. The design, installation, and upgrade flexibility benefits provided by an all-digital and shared network approach will be presented. The economic benefits of systems that can operate following failure and without immediate repair will be reviewed. The inherent ability of these redundant systems to provide effective built-in test and self-diagnostics capabilities will be described. The challenges associated with developing ultrareliable software for these systems and the difficulties associated with exhaustive verification testing will be presented as will additional development hurdles that must be overcome.

Subjects: AVIONICS, CONTROL SYSTEMS, REAL-TIME SYSTEMS, FAULT-TOLERANT COMPUTERS, SENSORS, ACTUATORS, COMPUTER SOFTWARE, SELF-TESTS, COST-EFFECTIVENESS, ULTRARELIABLE REAL-TIME SYSTEMS

Hattis, P.; Bailey, R.

Overview of the Kistler K-1 Guidance & Control System

Guidance, Navigation, and Control Conference. Held in Portland, OR, 08/09/1999 to 08/11/1999, pp. 1247-1254. Sponsored by: AIAA. (Draper Report no. P-3735)

Abstract: Draper Laboratory, under contract to Kistler Aerospace Corporation, is developing the complete flight guidance and control software for the K-1 launch vehicle. The K-1 is a fully reusable two-stage vehicle. The entire K-1 flight is performed autonomously except for one uplink of expected landing site winds before landing. The Launch Assist Platform (LAP) first stage flies a nearly open-loop three NK-33 engine boost phase, and subsequently reignites the center engine after staging to enable return to the launch site in a controlled coasting flight. The Orbital Vehicle (OV) second stage uses a single NK-43 engine to fly a fully closed-loop ascent to orbit. The LAP trajectory is designed to trade return propellant requirements against OV ascent performance impacts. Orbital maneuvers that are computed onboard the OV are used to circularize its orbit, deploy the payload, rephase the OV orbit for landing after 24 h, and then deorbit the vehicle. The OV reentry is flown with control thrusters used to bank the vehicle as directed by a predictor-corrector guidance law. Landing of both stages is done with a parachute descent and airbag touchdown, with return trajectories biased to provide correction of expected parachute wind drift effects during descent.

Subjects: KISTLER K-1 VEHICLE, GUIDANCE AND CONTROL, LAUNCH VEHICLES, LAUNCH ASSIST PLATFORM (LAP), ORBITAL VEHICLES

Henderson, T.; Dennehy, N.

Attitude Control and Energy Storage (ACES) Flywheel Demonstration Testbed

Space Power Workshop. 17th. Held in Long Beach, CA, 04/19/1999 to 04/21/1999. (Draper Report no. P-3730)

Subjects: FLYWHEELS, ATTITUDE CONTROL AND ENERGY STORAGE (ACES), ROTORS, TESTBEDS

Houston, K.M.; Hillman, R.E.; Kobler, J.B.; Meltzner, G.S.

Development of Sound Source Components for a New Electrolarynx Speech Prosthesis

International Conference on Acoustics, Speech, and Signal Processing (ICASSP). 24th. Held in Phoenix, AZ, 03/15/1999 to 03/19/1999. Sponsored by: IEEE. (Draper Report no. P-3690)

Abstract: For many individuals who lose their voices due to laryngeal cancer or trauma, the only option for speech is to use an electrolarynx (EL), which is a battery-powered vibrator that is held to the throat. Current devices produce speech that is very machine-like in sound with low levels of loudness and intelligibility that also draws undesired attention to the user. A project at Draper Laboratory, the Mass. Eye and Ear Infirmary, and MIT aims to develop a much improved EL called the Electrolarynx Communication System (ELCS), which is a DSP-based device consisting of a sound source, control, and speech enhancement subsystems or modules. This paper introduces the ELCS and discusses developments to date in the sound source module. Specific topics include the design of a new linear EL transducer and investigations into glottal waveform synthesis that should result in much more nature speech output.

Subjects: SPEECH PROCESSING, SYNTHETIC SPEECH, PROSTHESIS, ELECTROLARYNX, COMMUNICATION SYSTEMS, SPEECH ARTICULATION

Kirkos, G.; Bernstein, J.J.; Miller, R.; Finberg, S.; Houston, K.; Xu, B.; Ye, Y.; Cross, L.E.

Design of Micromachined PZT-on-Silicon 3-MHz Ultrasound Transducer Arrays (Abstract Only)

U.S. Navy Workshop on Acoustic Transduction Materials and Devices, 1999. (Draper Report no. P-3715)

Abstract: The DARPA-funded Sonoelectronics program is developing a hand-held underwater 3-D camera for high-resolution imaging through murky water. Draper is teamed with Lockheed Martin IRIS and Stanford University to create the sonar system. Potential commercial applications include medical ultrasound, fish identification, and nondestructive testing (NDT). This talk will discuss the design of micromachined ultrasound transducers for use at 3 MHz. A monomorph structure is constructed on resonant diaphragms, with sol-gel lead zirconate titanate (PZT) as the active ferroelectric layer deposited on insulating layers of ZrO2, SiO2, and undoped polysilicon. A novel in-plane polarization of the PZT is used to maximize sensitivity, while trading off output capacitance to match the CMOS buffer electronics. This results in 30-dB improved sensitivity compared with conventional polarizing across the thickness of the PZT. Fluid-filled through wafer holes (etched using deep inductively coupled plasma (ICP) etching) are used as an acoustic matching network to achieve resonance at both 1 and 3 MHz. A lumped-element equivalent circuit model will be presented, as well as finite-element analysis showing frequency response and resonant gain. Performance predictions for projector efficiency are based on FEA analysis, while receive sensitivity is derived from transmit response using reciprocity relations. Arrays of 16 x 16 elements are being fabricated currently. In Phase 2, 32 x 64 element arrays will be tiled into 128 x 128 retina arrays. Predicted receive sensitivity is -207 dB ref. 1 V/mPa at 3 MHz, while transmit response is predicted to be 115 dB ref. 1 mPa/V @ 1 m.

Subjects: ULTRASOUND IMAGES, LEAD ZIRCONATE TITANATE (PZT), TRANSDUCERS

Kogan, R.G.; Desai, M.; Pien, H.; Grimson, E.

Model-Based Visualization of Ultrasound Images

Battlefield Biomedical Technologies. Held in Orlando, FL, 04/06/1999, pp. 84-92. Sponsored by: SPIE.(Draper Report no. P-3725)

Abstract: Ultrasound imaging is the most pervasive, cost-effective, portable, high-resolution, and non-ionizing modality of diagnostic imaging available. The use of ultrasounds, however, has been hampered by the noise properties and poor contrast inherent in such imagery. A novel processing system is currently being developed that overcomes some of these disadvantages by producing a high-quality rendering of the anatomical structure of interest. In particular, a normal anatomical atlas is used as the starting point; this atlas is produced from either CT or MR imagery. As the ultrasound probe is moved along the body, image registration techniques, as well as external instrumentation that monitors the position and attitude of the ultrasound probe, are used to provide a continuous mapping between the ultrasound observations and the atlas. As discrepancies between the atlas and the observed anatomy occur, the atlas is deformed to reflect actual observations. Operated in this mode, the system displays the deformed high-resolution atlas to the user, providing a high-contrast, low-noise rendering of the patient's anatomy. In scenarios such as battlefield critical care, where large, immobile CT or MR scanners are not feasible, deformation of a high-quality atlas to match real-time ultrasound imagery can provide for much improved assessment and treatment possibilities.

Subjects: ULTRASOUND IMAGES, ANATOMY, IMAGE PROCESSING, IMAGE REGISTRATION

Kourepenis, A.

Low-Cost MEMS Inertial Systems for GPS Antijam Applications

Date: 4/8/1999. (Draper Report no. P-3729)

Abstract: Microelectromechanical Systems (MEMS) technologies have the enormous potential to enable the realization of low-cost inertial systems for a myriad of both commercial and military applications. With the large volume needs of the commercial market seeking inertial systems for automotive, camcorder, toys, and other applications, an economical base for the low-cost manufacture of these technologies will be established. These same capabilities can be leveraged to realize low-cost inertial systems critical to the development and deployment of weapons platforms at costs unable to be matched in other technologies. Current applications being demonstrated with MEMS inertial technologies include competent munitions, autonomous vehicles, robotics, and personal navigation. Many of these applications use MEMS-based Inertial Navigation System/Global Positioning Systems (INS/GPS) to enable precise guidance, navigation, and control functions at power, volume, and g-survivability levels unattainable by other means. The current performance of these devices is in the 10- to 100-deg/h range and offers marginal improvement in the antijam (A/J) capability of GPS receivers. Improvements in inertial performance, combined with innovative techniques for coupling the inertial and GPS Systems, will result in excellent rejection of intentional and unintentional GPS interference at low cost. This presentation details the state-of-the-art in MEMS technologies, highlighting current levels of performance and future initiatives that will result in small, low-cost inertial systems that perform at levels in the 0.01- to 0.1-deg/h regime. Operating principles and performance current levels of Draper Laboratory's MEMS technologies will be presented, and various applications and demonstrations will be described. Initiatives and roadmaps to higher levels of performance and the applicability to INS/GPS high A/J will be provided.

Subjects: MICROELECTROMECHANICAL SYSTEM (MEMS), LOW COST, GLOBAL POSITIONING SYSTEM (GPS)

Kumar, K.; Lee, T.; Petrovich, A.; Watts, M.; Dennis, R.

High-Performance 18-GHz Microwave Readout Flexured Mass Accelerometer

Navigational Technology for the 21st Century: Institute of Navigation Annual Meeting. 55th. Held in Cambridge, MA, 06/28/1999 to 06/30/1999, pp. 475-483. (Draper Report no. P-3707)

Abstract: A 108 dynamic range flexured mass accelerometer (FMA) utilizing microwave cavities and readout electronics operating at 18 GHz has been shown to be capable of achieving 1-micro-g bias stability with ±0.01°C temperature control. Developments previously reported for the device operating at 10 GHz (0.1) were implemented.

The flexure cartridge designed to eliminate anelastic and hysteretic effects during device static or tumble testing was incorporated into the 18-GHz device. Two device configurations were fabricated and tested for resolution, drift stability, and tumble bias repeatability in a 1-g field. One was constructed entirely from Superinvar, save for the ceramic flexure cartridge, while the other, which also used a similar ceramic flexure cartridge, was of a hybrid construction employing Superinvar microwave cavities and a ceramic Zerodur housing. Two breadboard configurations of low-noise 18-GHz electronics were designed, built, and tested successfully to support these evaluations. The best results achieved included the following: resolution,. 0.35 micro-g; drift stability with a rigid insert substituted for the flexured proof mass, <8 micro-g rms over 2 h; drift stability with the flexured proof mass in a 1-g field, 11.9 micro-g rms over 2 h; and 1-g tumble bias repeatability over 5 cycles in 10 min, 2.64 micro-g rms, measured for a single cavity, with no common-mode compensation.

Subjects: FLEXURED MASS ACCELEROMETER (FMA), SUPERINVAR, ZERODU

Kwan, A; Bedrossian, N.S.; Jang, J.W.; Grigoriadis, K.

Reducing Conservatism of Analytic Transient Response Bounds via Shaping Filters

Astrodynamics Specialist Conference. Held in Anchorage, AK, 8/16/1999 to 8/19/1999, pp. 623-632. Sponsored by: AAS/AIAA. (Draper Report no. P-3777)

Abstract: Recent results show that the peak transient response of a linear system to bounded energy inputs can be computed using the energy-to-peak gain of the system. However, an analytically-computed peak response bound can be conservative for a class of bounded energy signals, specifically pulse trains generated from jet firings, encountered in space vehicles. In this paper, shaping filters are proposed as a methodology to reduce the conservatism of peak response analytic bounds. This methodology was applied to a realistic Space Station assembly operation subject to jet firings. The results indicate that shaping filters indeed reduce the predicted peak response bounds.

Subjects: INTERNATIONAL SPACE STATION (ISS), REMOTE MANIPULATOR SYSTEM (RMS), SHAPING FILTERS, ATTITUDE CONTROL, PULSE TRAINS, JET FIRINGS

McConley, M.W.; Oh J.H.; Jamoom, M.B.; Feron, E.

Solving Control Allocation Problems Using Semi-Definite Programming

Journal of Guidance Control and Dynamics, Vol. 22, No. 3, 05/1999 to 06/1999, pp. 494-497. (Draper Report no. P-3751-REV-A)

Abstract: We consider the control surface allocation problem in the case when the surface allocation is limited to be a linear mapping from moment space to control space. We show that an approach to that problem based on ellipsoid volume maximization can be recast easily as a convex optimization problem. This method is applied to a numerical model of the F-18 HARV and has been compared with other approaches. The convex nature of the optimization problem under consideration makes it possible to incorporate the proposed procedure in a real-time aircraft control allocation reconfiguration in the event of damaged control surfaces. The byproducts of the optimization procedure (especially the resulting ellipsoids) may be used in other proposed surface allocation procedures as well.

Subjects: CONSTRAINED SIGNALS, LINEAR SYSTEMS, ACTUATORS, ALLOCATIONS, CONTROL SYSTEMS, AIRCRAFT CONTROL, MATHEMATICAL PROGRAMMING, OPTIMIZATION

McGovern, L.K.; Feron, E.

Closed-Loop Stability of Systems Driven by Real-Time, Dynamic Optimization Algorithms

IEEE Conference on Decision and Control. 38th. Held in Phoenix, AZ, 12/07/1999 to 12/10/1999. Sponsored by: IEEE. (Draper Report no. P-3754)

Abstract: The receding horizon control (RHC) scheme uses on-line optimization to find a finite-horizon control input to a constrained dynamic system. This paper examines the relationship between the optimization algorithm and the closed-loop dynamic system in RHC. Past research on RHC has assumed that the optimization algorithm provides an optimal solution in a fixed time interval. Since RHC typically employs quadratic programming, which is usually solved only approximately, this presupposition is not valid. Instead of making the traditional optimality assumption, this paper supposed that the provided solutions are only suboptimal. A sufficient condition is derived for closed-loop stability given control sequences, which are optimal with tolerance. Also, a bound is derived for the number of computations to find an optimal solution from a warm start using an interior-point method. As long as this number of computations can be carried out in less than the time step of the dynamic system, the closed-loop is guaranteed to be stable.

Subjects: RECEDING HORIZON CONTROL (RHC) OPTIMIZATION ALGORITHMS CLOSED-LOOP SYSTEMS

Miller, R.; Eiceman, G.A.; Nazarov, E.

A Micromachined Field Asymmetric-Ion Mobility Spectrometer (FA-IMS)

International Conference on Ion Mobility Spectrometry. 8th. Held in Buxton, Derbyshire, UK, 08/08/1999 to 08/12/1999 (Draper Report no. P-3744).

Abstract: The possibility of creating mobility spectrometers with dimensions under a few centimeters has been considered a next step in reducing the size and cost of ion mobility spectrometry (IMS) analyzers (1-3). This would be plausible if the drift tube design could be simplified over traditional configurations and if fabrication methods were amenable to mass production. One drift tube design, which is simplified without ion shutters or voltage dividers and offers extremely high sensitivity, is the asymmetric field analyzer (4-6) or FA-IMS. The FA-IMS has ion behavior rooted in mobility phenomena, although the details of ion motion are under active investigation. This mobility analyzer offers novelty in ion behavior, which is a secondary consideration and was selected for the simplicity of a planar micromachined construction. Another factor was the potential for improved detection limits over conventional analyzers. A planar micromachined field asymmetric-mobility drift tube has been crafted and partly characterized; results of these studies will be described along with certain performance features. The micromachined spectrometer drift tube is ~2.5 x 2.5 x 0.2 cm3 and is equipped with a 10.6 eV (lamda = 116.5 nm) photodischarge lamp as the ion source. The flow rate of drift gas is 2 1 min-1 of scrubbed air. Results from parametric studies with organic vapors of environmental, medical, or security interests are being used to evaluate the performance of the drift tube. Any compromises in spectral characteristics from reduction is size are still being assessed, but do not appear to be significant. These include detection limits, signal-to-noise, effect of moisture, and resolution of ions. Ion identities were confirmed by interfacing the analyzer to a tandem mass spectrometer.

Subjects: SPECTROMETERS, ION MOBILITY

Nazarenko, A.I.; Cefola, P.; Proulx, R.J.; Yurasov, V.

Neutral Atmosphere Density Monitoring Based on Space Surveillance System Orbital Data

Astrodynamics Specialist Conference. Held in Anchorage, AK, 08/16/1999 to 08/19/1999, pp. 1257-1291. Sponsored by: AAS/AIAA. (Draper Report no. P-3761)

Abstract: One approach for increasing the accuracy of satellite orbit determination and prediction for LEO satellites is the organization of an upper atmosphere monitoring function. This would be the analog of a weather service in the lower atmosphere. Monitoring of the upper atmosphere based on the use of the available satellite atmospheric drag data (ballistic factors) on all catalogued LEO satellites offers a low-cost approach to this capability. These data are operationally updated in the Space Surveillance System (SSS) as a result of regular satellite observations. It is concluded that there are actual possibilities for operational monitoring of the global atmospheric density variations at altitudes ranging from 200 up to 600 km. The elaboration of a plan for a real data test of the upper atmospheric monitoring concept is discussed.

Subjects: SPACE SURVEILLANCE SYSTEMS, MONITORING SYSTEMS, UPPER ATMOSPHERE, ORBIT DETERMINATION

Oh, J.; Jamoom, M.B.; McConley, M.W.; Feron, E.

Solving Control Allocation Problems Using Semi-Definite Programming

Journal of Guidance, Control, and Dynamics, Vol. 22, No. 3, May-June 1999, pp. 494-497. (Draper Report no. P-3751)

Abstract: We consider the control surface allocation problem in the case when the surface allocation is limited to be a linear mapping from moment space to control space. We show that an approach to that problem based on ellipsoid volume maximization can be easily recast as a convex optimization problem. This method is applied to a numerical model of the F-18 HARV and has been compared with other approaches. The convex nature of the optimization problem under consideration makes it possible to incorporate the proposed procedure in a real-time aircraft control allocation reconfiguration in the event of damaged control surfaces. The byproducts of the optimization procedure (especially the resulting ellipsoids) may be used in other proposed surface allocation procedures as well.

Subjects: CONSTRAINED SIGNALS, LINEAR SYSTEMS, ACTUATORS, ALLOCATIONS, CONTROL SYSTEMS, AIRCRAFT CONTROL, MATHEMATICAL PROGRAMMING, OPTIMIZATION

Persson, B.A.

Control of the Kistler K-1 First-Stage Reorientation Prior to Entry

Guidance, Navigation, and Control Conference. Held in Portland, OR, 08/09/1999 to 08/11/1999, pp. 1300-1309. Sponsored by: AIAA.(Draper Report no. P-3736).

Abstract: The control design for the Kistler K-1 first-stage reorientation maneuver is presented. The reorientation maneuver follows the main engine burn that places the first stage on a trajectory to return it to the landing site. The design takes advantage of the available aerodynamic moment to accelerate the first stage in the direction of the desired orientation for entry. The maneuver takes place near the apex of the first-stage return trajectory, a region of low dynamic pressure. Small Attitude Control System (ACS) thrusters are used to stabilize the vehicle during the maneuver. The maneuver must therefore, complete prior to reentry. This paper also presents a method for incorporating this time constraint into the design.

Subjects: KISTLER K-1 VEHICLE, SPACECRAFT REORIENTATION, ATTITUDE CONTROL SYSTEMS

Proulx, R.J.; Smith, J.E.; Cefola, P.J.; Draim, J.E.

Optimal Station-Keeping Strategies Via Parallel Genetic Algorithms

Space Flight Mechanics Meeting. Held in Breckenridge, CO, 02/07/1999 to 02/10/1999. Sponsored by: AAS/AIAA. (Draper Report no. P-3710).

Abstract: In an effort to overcome the limitations of more traditional methods, this paper investigates the use of genetic algorithms in generating nongreedy, global, near-optimal, station-keeping strategies. The orbit of an Ellipso™ Borealis satellite is constrained and the minimum-fuel optimal burn strategy is developed such that the orbit is maintained within the specified constraints over the entire time period of interest. The resulting fuel costs are shown to be lower than costs estimated via previous methods, specifically previous primer vector strategies. Operational and computational limitations of this method are also described.

Subjects: ELLIPSO SATELLITES, GENETIC ALGORITHMS, ORBITS

Sacramone, A.; Desai, M.

Real-Time Detection of Undersea Mines. A Complete Screening and Acoustic Fusion Processing System

Aerospace Defense Sensing Simulation and Controls (AeroSense). 13th. Held in Orlando, FL. 04/05/1999 to 04/09/1999. Sponsored by: SPIE.

Detection and Remediation Technologies for Mines and Minelike Targets. 4th. Held in Orlando, FL. 04/05/1999 to 04/09/1999, pp. 615-625. Sponsored by: SPIE. (Draper Report no. P-3714)

Abstract: A complete mine detection/classification (D/C) system has been specified and implemented, which runs in real-time, and has been exercised on the latest available dual-frequency side-scan sonar acoustic image sets. The complete D/C system comprises a collection of algorithms that has been developed and evolved at Draper over the past decade. The detection process consists of image normalization, enhancement, segmentation (blob formation), and feature extraction algorithms. The enhancement algorithm is a variant of a Markov Random field-based anomaly screener developed in FY 94. The features that were extracted were those derived in FY 93. A distance constrained matching algorithm, which was developed in FY 95, is used to generate a list of high- and low-frequency (HF and LF) fused tokens. The classification process involves the evaluation of a hierarchy of three multilayer perceptron neural networks: HF, LF, and HF/LF fused. Research performed in FY 95 also concentrated on the development of several variants of information fusion with hierarchical neural network. The "discriminant-combining" variant of fusion was selected as part of this D/C system. In addition, a classification post-processing and decision node statistic modification step, which was developed in FY 96, was included. This paper will describe the algorithms that were implemented. However, the emphasis will be on the performance results of processing the latest available side-scan imagery, comparison of single sensor vs. dual-frequency sensor result, and the issues that were encountered while exercising the D/C system on the new data set.

Subjects: UNDERSEA MINES, MINE DETECTION, SCREENING, REAL-TIME OPERATION, ACOUSTIC IMAGING, ALGORITHMS, NEURAL NETWORKS

Scholten, J.R.; Burnes, J.R. III; Gels, R.G.; McKenna, J.F.; Rosenberg, S.C.; Rosenstrach, P.A.

The Smart Intrusion Sensor Alarm

DSP World ICSPAT. Held in Orlando, FL, 11/1/1999 to 11/4/1999. (Draper Report no. P-3745)

Abstract: The Smart Intrusion Sensor Alarm (SISA) is a small (10 cm) battery-powered device with a miniature geophone and microphone sensor, flexible DSP-based signal processing, and a short-range radio transmitter. Advanced processing and packaging technologies are used to minimize size and maximize capability. Prototypes have been fabricated and field-tested to detect motorized vehicles and footsteps and to trigger a remote camera. The SISA will operate outdoors unattended for over two weeks.

Subjects: SMART INTRUSION SENSOR ALARM (SISA), DIGITAL SIGNAL PROCESSING, RADIO TRANSMISSION CAMERAS

Schwartz, G.; Richter, D.

A Concept for a Survivable Ship Control Computer

Ship Control Systems Symposium. 12th. Held in The Hague, Netherlands, 10/19/1999 to 10/21/1999. Sponsored by: SCS. (Draper Report no. P-3749)

Abstract: A surface ship can withstand considerable physical damage, but if the ship's control system does not also survive, the ship might still fail to complete its mission, or worse. This is in contrast to an aircraft fly-by-wire control system, where a small amount of damage may well cause loss of the vehicle, and the survivability of the control system is less of an issue. Fault-tolerant computers for real-time applications have typically followed the aircraft model without survivability as a goal. For example, the Ship Control Computer for the Seawolf attack submarine, SSN-21, was designed to be highly fault tolerant, but the redundant computing channels are connected via dedicated communication links and all are located in a single, relatively confined ship space. Even minor damage in that space could cause the loss of all processing channels. Furthermore, regaining capability would require a considerable repair effort. A concept is presented for a control system computer that will survive damage as well as tolerate faults. The concept has been pursued as an Independent Research and Development project at Draper Laboratory. The concept takes advantage of the redundant paths intrinsic to a mesh network. The computer's redundant computing channels communicate with each other using a connection-oriented protocol over a mesh network, which is automatically reconfigured by the surviving channels after damage has occurred. Thus, a channel cut off by damage to the network could be reconnected instantly, without the delay and expense of installing new cable. In the event of widespread damage, a channel could be plugged into the network in an undamaged part of the ship. The network technology being employed for this project is Asynchronous Transfer Mode, but the concept could be realized with other technologies. It is envisioned that when a fully developed computer is transitioned for shipboard deployment, the redundant computer channels will be nodes on the ship's data network infrastructure.

Subjects: SHIP CONTROL SYSTEMS, SURVIVABILITY, FAULT TOLERANCE, DAMAGE TOLERANCE, ASYNCHRONOUS TRANSFER MODE (ATM)

Shenai, S.; Howard, P.

Sensitivity Nulling of Inertial Guidance Systems Through Application of Linear Algebra on Rotation Groups

Date: 8/7/1999. (Draper Report no. P-3820)

Abstract: A rocket's flight path is maintained by a class of devices known collectively as an inertial guidance system. Due to unavoidable mechanical flaws, an error in the rocket's velocity, and thus position, is produced. A method exists to keep the error caused by these mechanical faults from accumulating. However, this paper finds a method for eliminating existing accumulated error.

Subjects: FLIGHT PATHS, INERTIAL GUIDANCE SYSTEMS, ERROR CORRECTION

Sitomer, J.; Connelly, J.; Kourepenis, A.

Micromechanical Inertial Guidance, Navigation, and Control Systems in Gun-Launched Projectiles

Atmospheric Flight Mechanics. Held in Portland, OR, 08/09/1999 to 08/11/99. Sponsored by: AIAA. (Draper Report No. 3757)

Abstract: Micromechanical technology applied to inertial instruments opens up many new applications where cost, size, and power are important. One very important application is the guidance, navigation, and control of gun-launched projectiles. In order to be affordable, these systems must cost less than $2,000, have very low power requirements, and eventually fit into a standard NATO Fuze of 9 in3, including all fuzing and safe and arming functions. Since 1997 when Draper demonstrated the first successful launch from a Navy 5-in projectile, many new applications have been identified and are being pursued. Draper is currently ready to flight test a micromechanical inertial measurement unit (MMIMU)/GPS in spinning 5-in projectile with the system despun in the nose-mounted fuze assembly This paper will describe the application of this technology to Navy and Army projectiles, both spin-stabilized an nonspinning. Some of the projectiles described will be the Navy's Extended-Range Guided Munition (ERGM) Demo, the Army's Precision Guided Mortar Munition (PGMM) 120-mm projectile, and standard NATO fuze applications to spin-stabilized projectiles such as existing 5 in, 155 mm, and 120 mm, etc.

Subjects: INERTIAL GUIDANCE SYSTEMS, MICROMECHANICAL DEVICES, CONTROL SYSTEMS, GUN-FIRED PROJECTILES, GLOBAL POSITIONING SYSTEM (GPS), INERTIAL MEASUREMENT UNIT (IMU), EXTENDED-RANGE GUIDED MUNITIONS (ERGM), PRECISION GUIDED MORTAR MUNITION (PGMM)

Smith, J.; Proulx, R.J.; Cefola, P.; Draim, J.E.

An Operational Approach for Generating Near-Optimal Station-Keeping Strategies via Parallel Genetic Algorithms

Astrodynamics Specialist Conference. Held in Anchorage, AK, 08/16/99 to 08/19/99, pp. 1349-1369. Sponsored by: AAS/AIAA. (Draper Report no. P-3756).

Abstract: Extending on the results of the authors' previous parallel genetic algorithm optimization approach, this study investigates ways in which the parallel genetic algorithm can be used as the basis for an operational station-keeping system. Specifically, an orbit is defined and parallel genetic algorithms are applied in such a manner that the orbit is maintained within a given set of tolerances. However, unlike the previous study that focuses only on maintaining the orbit within the state constraints, this study focuses on ways to maintain near-optimality in the station-keeping maneuvers, while also maintaining the operational characteristics of repeatability, speed of convergence, and ease of implementation. Finally, the use of this operational station-keeping algorithm as a planning tool is discussed.

Subjects: STATION-KEEPING, PARALLEL GENETIC ALGORITHMS, OPTIMALITY THEORY, ELLIPSO SATELLITES, DRAPER SEMIANALYTIC SATELLITE THEORY (DSST)

Soltz, J.A.; D'Souza, C.; Brand, T.J.; Tsukui, J.; Koyama, H.; Nakamura, T.

An Evaluation of the GPS Relative Navigation System for HTV Using a Functional Simulator

AIAA ISS Service Vehicle Conference. Held in Houston, TX, 04/25/1999 to 04/28/1999. (Draper Report no. P-3732).

Subjects: RELATIVE GLOBAL POSITIONING SYSTEMS (RGPS), SPACECRAFT RENDEZVOUS, INTERNATIONAL SPACE STATION (ISS), SIMULATORS, KALMAN FILTERING

Staugler, A.; Shepperd, S.W.

Autonomous On-Orbit Targeting and Guidance for a Reusable Launch Vehicle

Guidance, Navigation, and Control Conference. Held in Portland, OR, 08/09/1999 to 08/11/1999, pp.1255-1265. Sponsored by: AIAA. (Draper Report no. P-3737)

Abstract: Kistler Aerospace is currently developing a two-stage reusable launch vehicle to place payloads in circular low-Earth orbit. This vehicle is unique in that both stages return to the vicinity of the launch site and land on parachutes and airbags. Draper Laboratory has developed the guidance and targeting algorithms for the on-orbit phase of the Kistler mission. This phase consists of five burns, for each of which targeting supplies desired terminal conditions by directing the thrust vector during the burn. Targeting is driven by two primary requirements. First, the vehicle maneuver capability on entry is limited. Targeting accuracy is essential for landing in a small zone near the launch site. Second, unlike almost all previous programs, the Kistler vehicle will not communicate with the ground while on orbit, so targeting must be completely autonomous. Guidance draws heavily on algorithm designs from the Space Shuttle, but a new guidance mode developed specifically for the Kistler mission to provide an accurate orbital period for phasing is described.

Subjects: KISTLER K-1 VEHICLE; REUSABLE LAUNCH VEHICLES; ALGORITHMS; GUIDANCE, NAVIGATION, AND CONTROL (GN&C)

Stoll, J.C.; Smith, Russell D.

Revisiting the Multigimbal Dynamics Problem

Journal of Guidance, Control, and Dynamics, 9/1999. (Draper Report no. P-3703)

Subjects: CONTROL SIMULATION, GIMBAL SYSTEMS, DYNAMIC SYSTEMS, EASY5, RUNGE-KUTTA METHOD

Tetewsky, A.; Lozow, J.B.; Flueckiger, K.W.

Determining Specifications for an External GPS Reference Oscillator

International Technical Meeting of the Satellite Division of the Institute of Navigation (ION GPS). Held in Nashville, TN, 9/14/1999 to 9/17/1999, pp. 289-300. Sponsored by: ION.(Draper Report no. P-3722)

Abstract: There are many test and development situations in which a GPS receiver is operated with an external frequency reference that is phase locked to a GPS simulator or to a second receiver. Although one might intuitively predict that receiver performance could be enhanced by using a high-quality commercial frequency source, the application of this source can actually degrade performance as evidenced by reduced signal-to-noise ratio (SNR) measurements, increased bit detection errors, and related operational failures. The cause of this degradation may be the frequency synthesizer that converts the reference frequency to the unique master frequency required by a specific receiver. These degradations are generally the result of residual high-frequency phase noise introduced by tunable frequency synthesizers. In this paper, we quantitatively model the effects that reference frequency phase noise has on the receiver's master timing chain, specifically, L-band to baseband down-conversion errors and user clock errors. These timing chain errors then impact GPS receiver phase tracking, bit detection, and SNR estimation. Although a GPS receiver can compensate for "low-frequency" noises by calculating the oscillator's bias and drift rate, it cannot compensate for excess high-frequency phase noise. Using the anlaysis presented here, we can then understand why high-frequency side-band performance or small time difference Allan variance performance typical of a high-quality reference standard is needed, and why care is needed in selecting a general-purpose synthesizer. Measurements with a MITEL/Plessy GPS Builder-2 kit and P(Y) commercial-off-the-shelf (COTS) receiver driven by an external oscillator will be presented to illustrate the analysis. The main contributions of this work are to: (1) derive the industry rule-of-thumb of maintaining -80 to -100 dBc sidebands over the GPS front-end bandwidth and the oscillator's bandwidth fh, (2) understand how the upper bandwidth of the oscillator noise spectrum, fh, enters into the problem, and (3) translate oscillator specifications in Allan variance and other domains into the sideband domain that many circuit designers seem to prefer.

Subjects: OSCILLATORS, GLOBAL POSITIONING SYSTEM (GPS), GLOBAL POSITIONING SYSTEM RECEIVER, SIGNAL-TO-NOISE RATIO (POG, SNR), ALLAN VARIANCE

Tetewsky, A.K.; Lozow, J.B.

The Effects of Ground-Planes on Rotating GPS Antennas

Navigational Technology for the 21st Century: Institute of Navigation Annual Meeting. 55th. Held in Cambridge, MA, 06/28/1999 to 06/30/1999. (Draper Report no. P-3709)

Abstract: Time-varying changes in the orientation of a single GPS antenna with respect to the circularly polarized GPS signals in space can produce carrier phase modulation. However, popular GPS references and software tools do not include these terms and typically show only the contribution of translational terms to the GPS group delay and carrier phase measurements. With the emerging real-time kinematic (RTK) differential positioning and attitude fix algorithms requiring centimeter-level accuracy, coupled with arrays of antennas that are not constrained to be coplanar, orientation effects must be modeled. This paper presents a general theory of the phase effects introduced by changing antenna orientation and extends previous work by allowing ground plane effects to be modeled. Although computer models will ultimately be needed in order to account for ground-plane effects, by working with some simplified coordinate frames and motion models, additional factoring of the polarization functions into a pure orientation term plus a small residual spin modulation function yields valuable insights into the physics and interpretation of the polarization terms. A brief review of the phase wrapup problem and the original derivation based on the Hertzian (infinitesimal) dipole approximation without a ground-plane is presented. Next, directivity patterns for a small micropatch antenna with ground planes are evaluated, and the phase wrapup and spin modulation polarization effects are calculated. Because the directivity pattern holds only for the upper half-space, care must be used when calculating element responses to exclude contributions from beneath the ground plane. Due to this additional complexity, only the results for the antenna's boresight aligned with the spin axis will be covered. Although the technique is general, other geometries introduce significant amounts of algebra, and results are not yet available. The impact that the polarization phase has on raw (pseudorange and carrier phase) measurements, navigation fixes, and general receiver operation are also discussed.

Subjects: GLOBAL POSITIONING SYSTEM (GPS), ANTENNAS, KINEMATICS, REAL-TIME SYSTEMS, DIPOLES

Tetewsky, A.K.; Youngberg, J.W.

A Users' Perspective on the Continuing Evolution of GPS Simulators

Navigational Technology for the 21st Century: Institute of Navigation Annual Meeting. 55th. Held in Cambridge, MA, 06/28/1999 to 06/30/1999, pp. 581-596. (Draper Report no. P-3712)

Abstract: A GPS simulator is a valuable piece of test equipment. For the receiver developer, it provides a controllable signal source. For the integrator, it places a receiver (and often other navigation sensors) on a movable host platform. For the analyst, it produces an environment to enable studying the operational performance of a system. Over the last decade, we have seen developers' and testers' expectations of simulator capability and technical performance increase in parallel with the evolution and maturing of end-user missions. This paper identifies the trends we have seen and projects their implications on future simulator hardware and software.

Subjects: GLOBAL POSITIONING SYSTEM (GPS), SIMULATION

Toomey, K.; Seman, A.

Enabling Technologies for Cost-Effective Shipboard Situational Awareness - Reduced Ships-Crew by Virtual Presence (RSVP) - 1999 Advance Technology Demonstration (ATD)

Ship Control Systems Symposium. 12th. Held in The Hague, Netherlands, 10/19/1999 to 10/21/1999. Sponsored by: SCS. (Draper Report no. P-3748)

Abstract: Current U.S. Navy technology development thrusts and ship designs are being driven by pressures to reduce the costs of acquisition and ownership (life-cycle costs). As identified in the 1995 NRAC Study on "Life-Cycle Cost Reduction" and reiterated in a 1996 NRAC Summer Study on "Damage Control and Maintenance for Reduced Manning," a majority of the total cost of ownership of a ship is operation and support costs. Of these costs, manning is identified as the predominant cost driver. As stated in the 1995 NRAC study, reducing manning is not straightforward and "impacts the complex relationship of manpower requirements for operating, maintaining, supporting, fighting, and saving the ship. A rational approach to reducing manning requires a systems engineering approach with in-fleet demonstrations of proof of principle." To address this problem, the Navy is pursuing changes in doctrine and the insertion of cutting-edge technology aboard selected commissioned ships. Technology insertion will include advanced sensors, wireless networking, distributed monitoring, processing, and advanced reasoning capabilities. Current systems such as the Damage Control System (DCS), automated Machinery Control System (MCS), and the Integrated Condition Assessment System (ICAS) provide some level of this capability. However, the full level of automated monitoring and situational awareness/assessment required to safely reduce manning does not exist in these systems today. Reliable, accurate, and timely automated ship system assessment and awareness is required to support ship operation in a reduced crew environment. The Office of Naval Research-funded RSVP approach and demonstrated technologies capture the life-cycle cost reduction objectives and will form the basis of a ship-wide systems approach capable of providing situational awareness of ship's systems and compartments necessary for ship operation in a reduced manning environment. This paper will explore the necessary system architecture trade-offs of capability, cost, power consumption, reliability, and commercialization associated with the elements of the RSVP approach.

Subjects: SHIPBOARD TESTS, REDUCED SHIPS-CREW BY VIRTUAL PRESENCE (RSVP), ADVANCED TECHNOLOGY DEMONSTRATION (ATD)

Vytal, J.J.

Shipboard EMI/EMC Test Report for the Reduced Ships-Crew by Virtual Presence (RSVP) Advanced Technology Demonstration (ATD)

Date: 7/1999. (Draper Report no. CSDL-2000-009)

Abstract: Electromagnetic interference/electromagnetic compatibility (EMI/EMC) testing was conducted on board the USS Normandy (CG-60), a Ticonderoga Class Aegis Cruiser in early April of 1999. The tests were made to determine a typical electromagnetic operating environment for the RSVP radio frequency (RF) communications system and to perform propagation measurements in the proposed 2.4-GHz ISM band. The scope of the testing included measurements of the electromagnetic environment from 10 kHz to 3 GHz in three different spaces aboard the ship, and 2.4-GHz propagation measurements in those spaces. The spaces chosen were Main Engine Room 2, Auxiliary Machinery Room 1, and Engineering Crew Quarters. Of particular interest for the EMI measurements was the band at 2.4 GHz and those surrounding 100 MHz and 10.7 MHz, the proposed first and second intermediate frequencies (IFs) for the RSVP receiver. While the testing revealed no serious problems, it must be remembered that these measurements are only a snapshot in time aboard a single ship. Testing onboard different ships may reveal significantly different results.

Subjects: REDUCED-SHIPS CREW BY VIRTUAL PRESENCE (RSVP), WIRELESS COMMUNICATIONS, RADIO PROPAGATION

Weinberg, M.S.

Working Equations for Piezoelectric Actuators and Sensors

Journal of Microelectromechanical Systems, Vol. 8, No. 4, 12/1999, pp. 529-533. (Draper Report no. P-3668)

Abstract: A new solution to the force, displacements, and charges developed in piezoelectric beams is derived. Differing from previous solutions, this development determines the neutral axis where the bending strains are zero and results in a closed-form solution (without matrix inversion). With the closed form, simplifications become evident that increase understanding and facilitate calculations. These equations are than expanded to account for axial, built-in strains in the beam. A design example where axial forces exerted by the piezoelectric layer are important is presented.

Subjects: PIEZOELECTRIC ACTUATORS, LEAD ZIRCONATE TITANATE (PZT), BENDING

Zimpfer, D.J.

On-Orbit Flight Control Design for Kistler K-1 Reusable Launch Vehicle

Guidance, Navigation, and Control Conference. Held in Portland, OR, 08/09/1999 to 08/11/1999, pp. 1266-1274. Sponsored by: AIAA.(Draper Report no. P-3739)

Abstract: This paper describes the on-orbit control design for the Kistler K-1 Reusable Launch Vehicle Orbiting Vehicle (OV) stage. To meet the K-1 design goals, the control must provide fully autonomous operation with minimal preflight reconfiguration. The on-orbit guidance, navigation, and control targets, guides, and controls the vehicle to and from orbit, maintains orientation to adequately deploy payloads, separates from the payloads to avoid collision, and provides spin-stabilization prior to long periods of orbital "sleep" operations. For control, the OV relies on a gimbaled Orbital Maneuvering System (OMS) and cold-gas thrusters. The flight control algorithms are derived from the U.S. Space Shuttle and Russian Mir Space Station Control algorithms. This paper overviews the on-orbit mission operations for the K-1 vehicle, presents the control algorithms developed and summarizes predicted on-orbit control performance.

Subjects: ON-ORBIT NAVIGATION, FLIGHT CONTROL SYSTEMS (FCS), KISTLER K-1 VEHICLE, REUSABLE LAUNCH VEHICLES, ORBITAL MANEUVERING SYSTEM (OMS)