Operational Use of EPOS to Increase the Science Value of EO-1 Observation Data

Direct Trajectory Optimization and Costate Estimation via an Orthogonal Collocation Method

Direct Trajectory Optimization and Costate Estimation via an Orthogonal Collocation Method

Natural Sources of Antiparticles in the Solar System and the Feasibility of Extraction for High Delta-V Space Propulsion

Micromachined Silicon Plates for Sensing Molecular Interactions

Minimum Energy Path Planning for Ad Hoc Networks

Desai, M.N. et al.

Model-Based Variational Smoothing and Segmentation for Diffusion Tensor Imaging in the Brain

Robust Constrained Nongaussian FMRI Detection

Engineering MEMS Resonators with Low Thermoelastic Damping

Process Latitude of Deep-Ultraviolet Conformable Contact Photolithography

Framework for Autonomy

MEMS Inertial Technology. A Short Course

Optimal Reconfiguration of a Tetrahedral Formation Via a Gauss Pseudospectral Method

Parameterized Approach to the Design of Lunar Lander Attitude Controllers

Package Design for a Miniaturized Capacitive-Based Chemical Sensor

MEMS Technologies and Applications

Novel Technology for Rapid Species-Specific Detection of Bacillus Spores

Two-Dimensional Alignment of Differential Mobility Spectrometer Data

Actuator Allocation Algorithm Using Interior Linear Programming

Complementary Roll/Yaw Attitude Controller for Three-Axis Authority Momentum Spacecraft

Alternative Approach to Testing Embedded Real-Time Software

Biomimetic Sensory Abstraction Using Hierarchical Quilted Self-Organizing Maps

Putnam, Z.R. et al.

Improving Lunar Return Entry Footprints Using Enhanced Skip Trajectory Guidance

Risk-Aware Mixed-Initiative Dynamic Replanning (RMDR) Program Update

Legged Robot Motion with Explicit Stability Constraints: Theory and Application

Photonic Crystal Fiber IFOGs

Large-Strain Finite-Element Formulation for Biological Tissues with Application to Mitral Valve Leaflet Tissue Mechanics

On The Constitutive Models for Heart Valve Leaflet Mechanics

Error Sources in In-Plane Silicon Tuning-Fork MEMS Gyroscopes

Tilt Determination in MEMS Inertial Vestibular Prosthesis

Abramson, M.R.; Carter, D.W.; Collins, B.K.; Kolitz, S.E.; Miller, J.V.; Scheidler, P.J.; Strauss, C.M.

Operational Use of EPOS to Increase the Science Value of EO-1 Observation Data

6th Earth Science Technology Conference (ESTC), Baltimore, MD, 6/26/2006-6/29/2006. Sponsored by: NASA's Earth-Sun Systems Technology Office (ESTO) (Draper Report no. P-4451)

Abstract: We have demonstrated, in an operational setting, that technology in Draper's Earth Phenomena Observing System (EPOS) can improve the overall quality of remote sensing data products by increasing the likelihood that scenes scheduled for imaging will be high-quality scenes. We download, process and store cloud data generated by the Air Force Weather Agency's (AFWA) Stochastic Cloud Forecast Model (SCFM) and World-Wide Merged Cloud Analysis (WWMCA). The cloud cover data are used in EPOS to aid the tasking of the Hyperion instrument on EO-1, with the objective to increase the science value of the observation data. The SCFM global cloud cover data include forecasts provided every 6 hours for 3-hour periods up to 84 hours in the future. The WWMCA data are an hourly report of the current global cloud cover, based on data from nine geostationary and polar-orbiting spacecraft. We developed a methodology to fuse spatially and temporally correlated SCFM and WWMCA data and implemented a way to use these fused data to significantly increase the likelihood of EO-1 taking high-quality scenes (with total cloud cover less than or equal to 20%). Visualization methods were developed and implemented that enable human-machine collaborative decision-making.

Subjects: EARTH PHENOMENA OBSERVING SYSTEM (EPOS), EARTH OBSERVING MISSION (EO-1), STOCHASTIC CLOUD FORECAST MODEL (SCFM), WORLD-WIDE MERGED CLOUD ANALYSIS (WWMCA), HUMAN-MACHINE INTERACTIONS

Benson, D.A.; Huntington, G.T.; Thorvaldsen, T.P.; Rao, Anil V.

Direct Trajectory Optimization and Costate Estimation via an Orthogonal Collocation Method

Journal of Guidance, Control, and Dynamics , AIAA, Vol. 29, No. 6, 11/2006-12/2006, pp. 1435-1440 (Draper Report no. P-4400)

Subjects: GAUSS PSEUDOSPECTRAL METHOD, NONLINEAR PROBLEMS, OPTIMAL CONTROL, NONLINEAR PROGRAMMING

Benson, D.A.; Huntington, G.T.; Thorvaldsen, T.P.; Rao, A.V.

Direct Trajectory Optimization and Costate Estimation via an Orthogonal Collocation Method

Guidance, Navigation, and Control Conference and Exhibit, Keystone, CO, 8/21/2006-8/24/2006. Sponsored by: AIAA. (Draper Report no. P-4400-REV-1)

Abstract: A pseudospectral method, called the Gauss pseudospectral method, for solving nonlinear optimal control problems is presented. In the method presented here, an orthogonal collocation of the dynamics is performed at the Legendre-Gauss points. This form of orthogonal collocation leads a nonlinear programming problem (NLP) whose Karush-Kuhn-Tucker (KKT) multipliers can be mapped to the costates of the continuous-time optimal control problem. In particular, the Legendre-Gauss collocation leads to a costate mapping at the boundary points. The method is demonstrated on an example problem where it is shown that highly accurate costates are obtained. The results presented in this paper show that the Gauss pseudospectral method is a viable approach for direct trajectory optimization and costate estimation.

Subjects: GAUSS PSEUDOSPECTRAL METHOD, NONLINEAR PROBLEMS, OPTIMAL CONTROL, NONLINEAR PROGRAMMING

Bettinger, C.J.; Orrick, B.; Misra, A.; Langer, R.; Borenstein, J.T.

Microfabrication of Poly (Glycerol-Sebacate) for Contact Guidance Applications

Biomaterials , Elsevier, Vol. 27, No. 12, 4/2006, pp. 2558-2565 (Draper Report no. P-4408)

Abstract: Controlling cell orientation and morphology through topographical patterning is a phenomenon that is applicable to a wide variety of medical applications such as implants and tissue engineering scaffolds. Previous work in this field, termed contact guidance, has demonstrated the application of this cellular response on a wide variety of material substrates such as silicon, quartz, glass, and poly(di-methylsiloxane), typically using ridge-groove geometries with sharp feature edges. One limitation of these studies in terms of biomedical applications is the choice of material. Therefore, demonstrating contact guidance and topography in a biodegradable material platform is a promising strategy for controlling cellular arrangements in tissue engineering scaffolds. This study investigates several strategies to advance contact guidance strategies and technology to more practical applications. Flexible biodegradable substrates with rounded features were fabricated by replica-molding poly( glycerol-sebacate) on sucrose-coated microfabricated silicon. Bovine aortic endothelial cells were cultured on substrates with microstructures between 2 and 5 mm in wavelength and with constant feature depth of 0.45 mm. Cells cultured on substrates with smaller pitches exhibited a substantially higher frequency of cell alignment and smaller circularity index. This work documents the first known use of using a flexible, biodegradable substrate with rounded features for use in contact guidance applications. The replica-molding technique described here is a general process that can be used to fabricate topographically patterned substrates with rounded features for many biomaterials. Furthermore, these results may lead to further elucidation of the mechanism of cell alignment and contact guidance on microfabricated substrates.

Subjects: TISSUE ENGINEERING, SCAFFOLDS, MICROFABRICATION, CONTACT GUIDANCE, BIODEGRADABLE SUBSTRATES

Bickford, J.; Schmitt, W.M.; Spjeldvik, W.N.; Gusev, A.; Pugacheva, G.I.; Martin, I.

Natural Sources of Antiparticles in the Solar System and the Feasibility of Extraction for High Delta-V Space Propulsion

New Trends in Astrodynamics and Applications, III., Princeton, NJ, 8/16/2006-8/18/2006. Sponsored by: American Institute of Physics (AIP). (Draper Report no. P-4460)

Abstract: Antiparticles have a mass-based energy density nearly 10 orders of magnitude greater than the best chemical propellants. This attribute, particularly with antiprotons, enables exciting new approaches to spacecraft propulsion and design. However, these advantages have not been realized due to the inherent limitations associated with the artificial production and storage of the antiparticles. In comparison, antiparticles are produced and trapped naturally in the space environment due to the interaction of high-energy galactic cosmic rays (GCR) with residual matter in the interstellar medium and around solar system bodies. We assess the stable and transient antiparticle content of these sources and subsequently consider their capture and application to high delta-v space propulsion. The magnetosphere surrounding a planet offers a unique environment for the generation and trapping of antiprotons. Using Earth's magnetic field as an example, we have considered the various source mechanisms that are applicable to a planetary magnetosphere, the confinement duration versus transport processes, and the antiparticle loss mechanisms. We have estimated the trapped population of antiprotons magnetically confined following production in the atmosphere due to nuclear interactions between high-energy cosmic rays and constituents of the residual planetary atmosphere. We present results of the estimated particle fluxes due to pair production of antiprotons in the exosphere, the decay of albedo antineutrons generated in the atmosphere, and focusing the transient GCR antiprotons by the magnetic field of the planet. We discuss relevant scaling parameters and extend the terrestrial results to the Jovian planets and other solar system objects to estimate the total supply of antiprotons surrounding these bodies. The expediency of utilizing an electromagnetic scoop to extract antiparticles for practical use is subsequently considered. A large-scale magnetic field generated by a spacecraft can be used as a funnel to direct charged antiparticles toward a trap. We discuss and explore the fundamental performance limits of such a device and estimate the total antiproton collection rate for a given flux level. Based on predicted fluxes, it is potentially feasible to extract tens to hundreds of micrograms of antiprotons from the natural environment over the course of a year. Near the throat of the collection device, the particle can be transferred to closed field lines where it is stably trapped in the mini-magnetosphere that is formed in the space surrounding the exterior of the vehicle. Following capture and trapping, the particles can be used as a fuel for propelling spacecraft to high velocities.

Subjects: RADIATION BELTS, MAGNETIC CONFINEMENT, RADIATION PROCESSES, SPACE PROPULSION

Carlen, E.T.; Weinberg, M.S.; Dube, C.E; Zapata, A.M.; Borenstein, J.T.

Micromachined Silicon Plates for Sensing Molecular Interactions

Applied Physics Letters, AIP , Vol. 89, No. 17, 10/23/2006 (Draper Report no. P-4452)

Abstract: A micromachined surface stress sensor based on a thin suspended crystalline silicon circular plate measures differential surface stress changes associated with vapor phase chemisorption of an alkanethiol self-assembled monolayer. The isolated face of the suspended silicon plate serves as the sensing surface treated with a receptor layer sensitive to a target molecule, in this case Au(111). Chemisorption of an alkanethiol on the gold coated silicon surfaces results in plate bending. Plate displacements, measured with a phase scanning interferometer, indicate a differential surface stress change for (see full-text).

Subjects: SURFACE STRESS, MEASUREMENTS, SENSORS

Chen, D.; Lin, P.J. 

Minimum Energy Path Planning for Ad Hoc Networks 

Wireless Communications and Networking Conference (WCNC), Las Vegas, NV, 04/03/2006 - 04/06/2006. Sponsored by: IEEE (Draper Report no. P-4395 ) 

Abstract: We introduce the minimum energy path planning (MEPP) problem of finding a path for a mobile node traveling from a source to a destination while communicating with at least one node from a set of stationary nodes in such a way that minimizes the transmission energy used in communication. We characterize this problem and introduce the discretized graph algorithm that finds an approximate path by discretizing the problem space to form a graph and performing a shortest path search from source to destination. We find algorithm parameters that allow energy-efficient paths to be found in a suitable time. Finally, we discuss how this algorithm can be extended to facilitate other considerations in the problem. 

Subjects: AD HOC NETWORKS, COMMUNICATION ENERGY, MOBILE NODES, ENERGY PATHS

Desai, M.N.; Kennedy, D.N.; Mangoubi, R.S.; Shah, J.; Karl, C.; Worth, A.; Makris, N.; Pien, H.

Model-Based Variational Smoothing and Segmentation for Diffusion Tensor Imaging in the Brain

Neuroinformatics , Vol. 4, No. 3, 2006, pp. 217-234 (Draper Report no. P-4409)

Abstract: This article applies a unified approach to variational smoothing and segmentation to brain diffusion tensor image data along user-selected attributes derived from the tensor, with the aim of extracting detailed brain structure information. The application of this framework simultaneously segments and denoises to produce edges and smoothed regions within the white matter of the brain that are relatively homogeneous with respect to the diffusion tensor attributes of choice. This approach enables the visualization of a smoothed, scale invariant representation of the tensor data field in a variety of diverse forms. In addition to known attributes such as fractional anisotropy, these representations include selected directional tensor components and additionally associated continuous valued edge fields that might be used for further segmentations. A comparison is presented of the results of three different data model selections with respect to their ability to resolve white matter structure. The resulting images are integrated to provide better perspective of the model properties (edges, smoothed image, and so forth) and their relationship to the underlying brain anatomy. The improvement in brain image quality is illustrated both qualitatively and quantitatively, and the robust performance of the algorithm in the presence of added noise is shown. Smoothing occurs without loss of edge features because of the simultaneous segmentation aspect of the variational approach, and the output enables better delineation of tensors representative of local and long-range association, projection, and commissural fiber systems.

Subjects: MAGNETIC RESONANCE IMAGING (MRI), TENSOR DATA, BRAIN

Desai, M.N.; Mangoubi, R.S.; Kennedy, D.

Robust Constrained Nongaussian FMRI Detection

International Symposium on Biomedical Imaging from Nano to Macro, 2006, Arlington, VA 04/06/2006 - 04/09/2006. Sponsored by: IEEE (Draper Report no. P-4405)

Abstract: For functional magnetic resonance imaging (fMRI) detection, it is desirable to have sensitive detectors for enhanced performance in a low signal-to-noise ratio (SNR) environment. This sensitivity, usually captured through learning associated models, comes at the price of increased false alarms. In this paper, we address the issue of robustness to false alarm while maintaining sensitivity by providing the analytical framework for incorporating prior information in the form of constraints in Gaussian and non-Gaussian settings. We show that the impact on the decision statistic of incorporating constraints is simply captured through a simple modification of the unconstrained detector's statistic. The computational burden of the constrained and unconstrained detectors are thus similar. The performance of the new constrained detector is shown on fMRI data to provide superior performance when compared with the conventional constant false alarm (CFAR) detector.

Subjects: FMRI, DETECTORS, NON-GAUSSIAN, ROBUST

Duwel, A.E.; Chandler, R.N.; Kenny, T.W.; Varghese, M.

Engineering MEMS Resonators with Low Thermoelastic Damping

Journal of Microelectromechanical Systems , IEEE. Vol. 15, No. 6. 12/2006, pp. 1437-1445. (Draper Report no. P-4358)

Abstract: This paper presents two approaches to analyzing and calculating thermoelastic damping in micromechanical resonators. The first approach solves the fully coupled thermomechanical equations that capture the physics of thermoelastic damping in both two and three dimensions for arbitrary structures. The second approach uses the eigenvalues and eigenvectors of the uncoupled thermal and mechanical dynamics equations to calculate damping. We demonstrate the use of the latter approach to identify the thermal modes that contribute most to damping and present an example that illustrates how this information may be used to design devices with higher quality factors. Both approaches are numerically implemented using a finite-element solver (Comsol Multiphysics). We calculate damping in typical micromechanical resonator structures using Comsol Multiphysics, and compare the results with experimental data reported in literature for these devices.

Subjects: MICROELECTROMECHANICAL SYSTEMS (MEMS), THERMOELASTIC DAMPING, RESONATORS

Fucetola, C.; Carter, D.J.

Process Latitude of Deep-Ultraviolet Conformable Contact Photolithography

50th International Conference on Electron, Ion, and Photon Beam Technology and Nanofabrication, Baltimore, MD, 5/30/2006 - 6/2/2006 (Draper Report no. P-4415)

Subjects: PHOTOLITHOGRAPHY, ULTRAVIOLET

Fuhrman, L.R.

Future of Lunar Landing Systems

29th Rocky Mountain Guidance and Control Conference, Breckenridge, CO, 02/04/2006-02/08/2006. Sponsored by: AAS (Draper Report no. P-4413)

Abstract: The 2004 introduction of NASA's Vision for Space Exploration has set the stage for an intensive new era of Lunar exploration. These Lunar exploration missions will not simply be a modern-day repeat of the Apollo experience; the mission objectives pose significant new challenges to the space system designer. In particular, the keen interest in long-duration crewed missions to the Lunar South Pole region will have major impacts on the landing vehicle design. This paper will provide an overview of the Lunar mission objectives and the guidance, navigation, and control system implications of achieving those objectives. In particular, we will discuss the need to develop precision landing capability (10 m ­ 100 m), real-time on-board hazard detection and avoidance, and the ability for "anywhere, anytime" access to the moon's surface. A possible incremental technology demonstration approach utilizing robotic precursor missions to establish safe and precise Lunar landing capability will also be discussed.

Subjects: LUNAR LANDING, LUNAR EXPLORATION, GUIDANCE NAVIGATION AND CONTROL (GN&C)

Gustafson, D.E.; Elwell Jr., J.M.; Soltz, J.A.

Innovative Indoor Geolocation Using RF Multipath Diversity

Position Location and Navigation Symposium (PLANS), San Diego, CA. 4/25/2006-4/27/2006. Sponsored by IEEE and Institute of Navigation (ION) (Draper Report no. P-4421)

Abstract: A new concept is presented for indoor geolocation in multipath environments where direct paths are sometimes undetectable. In contrast to previous statistically-based approaches, the multipath delays are modeled using a geometry-based argument. Assuming a series of specular reflections off planar surfaces, the model contains a maximum of three unknown multipath parameters per path that may be estimated when geolocation accuracy is sufficiently high. If some of the direct paths subsequently become undetectable, it is possible under certain conditions to maintain geolocation accuracy using only the indirect path length measurements. The new concept is illustrated via simulation using a relatively simple representative scenario. Performance is compared with a traditional method that uses only direct path measurements, indicating the potential for significantly improved indoor geolocation accuracy in environments dominated by multipath. Since the estimated multipath parameters are geometry-dependent, this approach allows the possibility of building up indoor map information as the geolocation process commences.

Subjects: GEOLOCATION, MULTIPATH ENVIRONMENTS, RADIO FREQUENCY (RF)

Harjes, D.I.; Clark, H.A.

Novel Optical Biosensor Arrays for Toxicity Screening in Drug Discovery

57th Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy (PITTCON, Orlando, FL, 03/12/2006-03/17/2006. (Draper Report no. P-4374)

Abstract: Inhibition of HERG channels can lead to Long QT syndrome, a potentially fatal heart arrhythmia. For FDA approval, all novel drugs must be screened for HERG inhibition, regardless of the therapeutic target of the drug. Currently, the most reliable and commonly used methods for HERG screening, such as patch clamp techniques, tend to be slow and expensive. Our new sensor system uses a series of modified optical sensors (optodes) to monitor ion currents in cells during HERG screening, specifically extracellular sodium and potassium and intracellular calcium. Extracellular measurements are performed using large thin-film optodes positioned in the extracellular matrix. Intracellular sensors consist of small nanosphere optodes that can be loaded into the cytoplasm. For high-throughput applications, this sensor array can be used with 96 or 12 well plates in any standard fluorescent plate reader. This makes the system amenable to many existing high-throughput screening infrastructures. Each individual extracellular optode consists of an ultra-thin plasticized PVC membrane containing fluorescent and ion-selective compounds. Current sensors can accurately measure sodium and potassium levels outside cells with recorded response times less than 20 ms. Very high signal-to-noise ratios (400:1) are possible, depending on the measuring optics. To be effective, the sensors have been tuned to achieve optimal sensitivity at extracellular biological ion levels; however, they still maintain a detection range from 500 nM to 500 mM. Even at high potassium levels (4 mM), the optodes remain sensitive enough to detect changes as low as 100 nM. Similar sensitivities are also achievable with sodium optodes. Both optodes are fully reversible, which is essential for action potential measurements. With their fast response time and high sensitivity, the sensors can accurately map the ion flux characteristics of cells. Experiments with cardiac myocytes have shown the measurement of an action potential using a potassium optode. These data can be linked directly to cardiac arrhythmia. This sensor system has the potential for high-throughput screening, while also providing detailed information regarding ion channel activity. By improving screening rate and information content, this sensor system will save money and prevent the approval of possibly toxic compounds.

Subjects: DRUG DELIVERY, TOXICITY, OPTICAL SENSORS, OPTODES, BIOSENSORS

Heinrich, N.; Case, A.; Stein, R.L.; Clark, H.A.

Optical Sensors for the Monitoring of Enzymatic Reaction for Drug Screening in Neurodegenerative Disease

57th Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy (PITTCON), Orlando, FL, 03/12/2006-03/17/2006 (Draper Report no. P-4375)

Abstract: Transglutaminase has been identified as a potentially important enzyme in neurodegenerative diseases such as Huntington's disease or Alzheimer's. Current assays typically monitor enzyme products or secondary reactions to determine activity. Transglutaminase catalyzes acyl transfer reactions from glutamine to peptides. This reaction also produces ammonium. We have developed a fluorescence-based assay using a polymer optode to monitor ammonium production. This assay requires no secondary reaction and is highly specific for ammonium. Also, because of the nature of the polymer, there is no interference from components of the reaction or buffer. The use of fluorescence allows for real-time measurements in a high-throughput assay. Ammonium-selective optodes were created using plasticized PVC and mounted in the bottom of a 96-well plate. Optodes were tuned to achieve a response time in the millisecond range and a detection limit of micromolar levels. The transglutaminase catalyzed reaction of Z-gln-gly with hydroxylamine serving as the acceptor was monitored over 2 hours. The reaction showed substrate, Z-gln-gly, dependence and continued for over 2 hours. Controls, no added enzyme, showed very little change throughout the experiment. Unlike previous methods for screening for transglutaminase inhibition (coupled enzymatic absorbance assays), the sensors are easily calibrated and show considerably less variability. A substrate dependence of enzyme activity was shown. Because all the ratios rose to similar values upon addition of excess ammonium at the end of the experiment, it can be determined that monitoring ammonium production is substrate-dependent and not optode or diffusion-dependent. We will show a small-scale screen of novel drugs targeted for neurodegenerative disease. This experiment will determine efficacy and concentration dependence of each drug tested. Using a 96-well plate allows for continuous monitoring of enzyme activity in a high-throughput fashion. Because the assay is based on fluorescence, the data can be easily calibrated and presented in an ideal fashion. This assay provides accurate, reproducible measurements of enzyme activity.

Subjects: NEURODEGENERATIVE DISEASE, OPTICAL SENSORS, TRANSGLUTAMINASE, ENZYMES, OPTODES, DRUG SCREENING

Hildebrant, R.

Framework for Autonomy

Optics East, International Symposium, Boston, MA. 10/1/2006-10/4/2006. Sponsored by: SPIE (Draper Report no. P-4459)

Abstract: The development of autonomous planning and control system software often results in a custom design concept and software specific to a particular control application. This paper describes a software framework for orchestrating the planning and execution of autonomous activities of an unmanned vehicle, or a group of cooperating vehicles, that can apply to a wide range of autonomy applications. The framework supports an arbitrary span of autonomous capability, ranging from simple low-level tasking, requiring much human intervention, to higher level mission-oriented tasking, requiring much less. The approach integrates the four basic functions of all intelligent devises or agents (plan development, plan monitoring, plan diagnosing, and plan execution), with the mathematical discipline of hierarchical planning and control. The result is a domain-independent software framework, to which domain-dependent modules for planning, monitoring, and diagnosing are easily added. This framework for autonomy, combined with the requisite logic for vehicle control, can then be deployed to realize the desired level of autonomous vehicle operation.

Subjects: AUTONOMOUS PLANNING, UNMANNED VEHICLES (UV), REFERENCE MODEL ARCHITECTURE

Hopkins III, R.E.

MEMS Inertial Technology. A Short Course

Position Location and Navigation Symposium (PLANS), San Diego, CA. 4/25/2006 - 4/27/2006. Sponsored by: IEEE/Institute of Navigation (ION) (Draper Report no. P-4442)

Joint Navigation Conference (JNC). Las Vegas, NV, 5/01/2006 - 5/4/2006. Sponsored by: Joint Service Data Exchange (JSDE)

Abstract: This course is useful for people who would like to develop a basic understanding of inertial MEMS technology. It covers a variety of MEMS sensors and their operational characteristics as currently being developed in industry and universities. Developments in MEMS INS/GPS, as well as current and future applications of MEMS inertial systems, will be described.

Subjects: MICROELECTROMECHANICAL SYSTEMS (MEMS), INERTIAL TECHNOLOGY, INERTIAL SENSORS

Huntington, G.T.; Rao, A.V.

Optimal Reconfiguration of a Tetrahedral Formation Via a Gauss Pseudospectral Method

Advances in the Astronautical Sciences, AAS, Vol. 123, Part II, 2006, pp. 1337-1358, Astrodynamics Specialist Conference, Lake Tahoe, CA, 8/7/2005-8/11/2005. Sponsored by: AAS/AIAA. (Draper Report no. P-4331)

Abstract: This paper addresses the problem of determining a minimum-fuel maneuver sequence to reconfigure a tetrahedral formation. The objective of this work is to develop a single-orbit, minimum-fuel reconfiguration strategy such that, after reconfiguration, the four spacecraft are able to return to an acceptable tetrahedral configuration in a region of interest near apogee for a period of 3 weeks without any required propulsive maneuvers. In the design considered here, an acceptable tetrahedron is obtained by satisfying several constraints on the shape and size of the tetrahedron. The optimal reconfiguration problem is posed as a nonlinear optimal control problem and is solved via direct trajectory optimization using a method called the Gauss pseudospectral method. The results obtained in his study provide insight into the structure of the optimal mission design and demonstrate the generality, computational efficiency, and accuracy of the Gauss pseudospectral method.

Subjects: SPACECRAFT FORMATIONS, GAUSS PSEUDOSPECTRAL METHOD, FORMATION FLYING, OPTIMAL CONTROL

Johnson, M.C.

Parameterized Approach to the Design of Lunar Lander Attitude Controllers

Guidance, Navigation, and Control Conference, Keystone, CO, 8/21/2006-8/24/2006. Sponsored by: AIAA (Draper Report No. P-4467)

Abstract: The next generation of crewed lunar landings will include a huge leap forward in technology and capability, with much larger vehicles than those used on Apollo combined with precision requirements 2 or 3 orders of magnitude tighter. A parameterized approach to attitude control system design has been developed for this lunar landing application. The approach makes “first- order” assessment of the impact of various vehicle characteristics available for initial system-level design trades. It also provides the ability to quickly perform preliminary attitude control design and analysis as vehicle and requirements definitions evolve. Results have been generated by “turning the crank” on a representative large-scale manned lunar lander. However, the process developed here could also be applied to a small robotic vehicle. The approach summarized here includes generation of a vehicle model, synthesis of attitude controllers, and preliminary design verification. The vehicle model is general enough to encompass a large range of surveyed vehicles, but is specific enough to capture important characteristics using a small number of parameters. For example, mass property variations resulting from propellant depletion are modeled, as are various implementation details surrounding the use of a gimbaled main engine and Reaction Control System (RCS) jets. Simple, generalized, but effective RCS and Thrust Vector Control (TVC) algorithms are employed, and procedures are codified to design and analyze these controllers for stability and performance. The generalized models have also been implemented in a closed-loop 6-degree-of-freedom (6-DOF) simulation so that it can be verified that the resulting design provides an adequately crisp response to attitude commands generated by a guidance algorithm during a lunar landing trajectory. A potential instability during terminal descent was identified during application of the design process developed here to the representative lunar lander. This instability can arise due to initial “back-swing” of the main engine inherent in the response of TVC to attitude commands. A design solution to this is suggested and demonstrated using the closed-loop 6-DOF simulation.

Subjects: LUNAR LANDING, CREW EXPLORATION VEHICLES (CEV), ATTITUDE CONTROL SYSTEMS, SYSTEM DESIGN

Key, R.; Kahn, A.C., Deutsch, O.L. 

Midcourse Phase Inventory Management with Uncertain Threats 

Missile Defense Conference & Exhibit, Washington, DC, 03/20/2006 - 03/24/2006. Sponsored by: AIAA (Draper Report no. P-4386)

Khademhossini, A.; Langer, R.; Borenstein, J.T.; Vacanti, J.P. 

Microscale Technologies for Tissue Engineering and Biology 

Proceedings of the National Academy of Sciences of the USA, Vol. 103, No. 8, 02/2006 (Draper Report no. P-4404) 

Abstract: Microscale technologies are emerging as powerful tools for tissue engineering and biological studies. In this review, we present an overview of these technologies in various tissue engineering applications, such as for fabricating 3D microfabricated scaffolds, as templates for cell aggregate formation, or for fabricating materials in a spatially regulated manner. In addition, we give examples of the use of microscale technologies for controlling the cellular microenvironment in vitro and for performing high-throughput assays. The use of microfluidics, surface patterning, and patterned cocultures in regulating various aspects of cellular microenvironment is discussed, as well as the application of these technologies in directing cell fate and elucidating the underlying biology. Throughout this review, we will use specific examples where available and will provide trends and future directions in the field. 

Subjects: TISSUE ENGINEERING; MICROELECTROMECHANICAL SYSTEM (MEMS); MICROSCALE

Kondoleon, C.A.; Marinis, T.F.

Package Design for a Miniaturized Capacitive-Based Chemical Sensor

39 th International Symposium on Microelectronics, San Diego, CA, 10/8/2006-10/12/2006. Sponsored by: International Microelectronics and Packaging Society (IMAPS) (Draper Report no. P-4456)

Abstract: An affinity-based mechanical sensor being developed at Draper Laboratory measures the amount of stress induced at the sensor's surface as a result of the molecular interactions of an affinity complex immobilized on the surface. The signal measured is a capacitance change between a fixed plate and a second plate that is free to deflect. The deflecting plate is a diaphragm modified with a chemically-selective coating that binds to a target analyte. Binding of the target analyte to the selective coating generates stress at the sensor's surface causing the diaphragm to deflect, thus changing the gap spacing between the two plates, and generating the signal that can be used for biosensing. An electronics test board was developed to generate the two carrier frequencies for exciting the sensors. To use this setup, a package was required for integrating the sensor die into the test board. There are several design challenges associated with packaging this type of device. The sensor die must be enclosed for mechanical protection, while minimizing the path length the analytes must travel to the diaphragm from the reservoir. The electrical connections to the sensor must be kept as short as possible to minimize parasitic capacitance and must be isolated from direct contact with the gas stream being evaluated. Finally, the sensor die must be mechanically isolated from the package such that thermally induced strains of the diaphragm sense element are minimized. These design challenges were met by bonding the sensor die within a leadless ceramic chip carrier (LCC), using a laser-machined Kapton film gasket. The die was bonded face down on the Kapton film so that the four diaphragms on the die were aligned with an opening in the film. The dimensions of this cutout allowed the diaphragms to be fully exposed, while providing sufficient support around the die's perimeter. The bottom side of this Kapton gasket was bonded to the floor of the carrier, which was partially cut away to provide vapor access to the diaphragms. Wire bonds were used to make electrical connections between the sensor and chip carrier. The packaged sensor was mounted in a socket on a circuit board, both of which had cutouts to allow vapor access to the sensor. This die attachment design eliminated problems with die stress and sensor stability that were previously encountered by bonding the sensor directly into the chip carrier with various adhesives. The B-staged adhesive on the Kapton film also minimized contamination of the diaphragms that occurred with the use of dispensed adhesives.

Subjects: MECHANICAL SENSORS, STRESS ANALYSIS, SENSOR DIE

Kourepenis, A.S.; Barbour, N.M.; Hopkins III, R.E.; Serna, F.J.; Varghese, M.

MEMS Technologies and Applications

International Test and Evaluation Association (ITEA) Annual Technology Review Conference, Cambridge, MA, 8/8/2006-8/10/2006. Sponsored by: ITEA (Draper Report No. P-4468)

Subjects: INERTIAL NAVIGATION, MICROELECTROMECHANICAL SYSTEMS (MEMS)

Krebs, M.D.; Tingley, R.D.; Zeskind, J.E.; Holmboe, M.E.; Kang, J.J.; Davis, C.E.

Alignment of Gas Chromatography-Mass Spectrometry Data by Landmark Selection from Complex Chemical Mixtures 

Chemometrics and Intelligent Laboratory Systems , Vol. 81, No. 1, 1/2006, pp. 74-81 (Draper Report no. P-4250 REV-1) 

Abstract: Analyzing the response of analytical sensors to complex chemical mixtures is difficult, as signals may overlap and may vary between experiments. The analysis and comparison of data files depends on their repeatability, and misaligned signals will not be directly comparable. We present a method for aligning chromatographic data by the selection of landmarks, the matching of these landmarks across chromatograms, the calculation of a functional approximation describing the amount of shift of the landmarks between files using cubic spline interpolation, and the subsequent shifting of the data by the application of this functional approximation so that the two files are aligned. We demonstrate the effect of this alignment on subsequent principal component analysis. 

Subjects: ANALYTICAL SENSOR, LANDMARKS, CHROMATOGRAMS

Krebs, M.D.; Mansfield, B.; Yip, P.; Cohen, S.; Sonenshein, A.L.; Hitt, B.A..; Davis, C.E.

Novel Technology for Rapid Species-Specific Detection of Bacillus Spores

Biomolecular Engineering , Vol. 23, 2/2006, pp. 119-127 (Draper Report no. P-4294-REV-A)

Abstract: There is an urgent need for a small, inexpensive sensor that can rapidly detect bio-warfare agents with high specificity. Bacillus anthracis , the causative agent of anthrax, would be a perilous disease-causing organism in the event of a release. Currently, most anthrax detection research is based on nucleic acid detection, immunoassays, and mass spectrometry, with few detection levels reported below 105 spores. Here, we show the ability to distinguish Bacillus spores to a level approaching 103 spores, below the reported median infectious dose of B. anthracis , using pyrolysis-micromachined differential mobility spectrometry and novel pattern recognition algorithms that combine lead cluster mapping with genetic algorithms.

Subjects: SENSORS, BACILLUS ANTHRAX, BIOLOGICAL WARFARE, DIFFERENTIAL MOBILITY SPECTROMETRY (DMS), GENETIC ALGORITHMS, ADAPTIVE PATTERN RECOGNITION

Krebs, M.D.; Kang, J.J.; Cohen, S.; Lozow, J.B.; Tingley, R.D.; Davis, C.E.

Two-Dimensional Alignment of Differential Mobility Spectrometer Data

Sensors and Actuators B – Chemical , Vol. 119, No. 2, 12/2006, pp. 475-482 (Draper Report no. P-4297-REV-A)

Abstract: Alignment of data is critical for analysis involving the comparison of multiple files. Analytical sensor data resulting from complex chemical mixtures can often be misaligned due to time-varying biases resulting from mechanical instrument variability. In addition to the necessity for time alignment, data from the micromachined differential mobility spectrometer (DMS) may be slightly shifted when comparing various data sets due to the effect of heat and flow variations on the compensation voltage (Vc). Thus, the data in this dimension can also benefit from alignment. We present here a method for the alignment of both dimensions (scans and Vc) of pyrolysis-DMS data using a single file as reference. The Vc dimension is first aligned with respect to the reference file; this is a rigid shift and no interpolation is performed. This is an advantage as the Vc dimension has physical meaning and should not be altered by interpolation. The time (or scans) dimension is then aligned with respect to the reference by identifying common landmarks and interpolating according to a piecewise linear function calculated based on the amount of shift between the two files. The effect of a slight change in flow in the Vc dimension is examined using the nitrogen reactant ion peaks as a standard signal. This method is useful for further data processing in which multiple files are to be directly compared, and it could also be useful for two-dimensional alignment of data from other sensor modalities.

Subjects: DIFFERENTIAL MOBILITY SPECTROMETRY (DMS), PYROLYSIS, DATA ALIGNMENT

Landis, D.L.; Thorvaldsen, T.P.; Fink, B.J.; Sherman, P.G.; Holmes, S.M.

Deep Integration Estimator for Urban Ground Navigation

Position Location and Navigation Symposium (PLANS), San Diego, CA, 4/25/2006 - 4/27/2006. Sponsored by: IEEE/Institute of Navigation (ION) (Draper Report no. P-4438)

Abstract: The objective of the Personal Navigator System (PNS) is to construct a wearable navigation system that provides accurate position over extended missions in a deprived Global Positioning System (GPS) environment. The prototype multisensor navigator included a set of micromechanical inertial sensors, a three-axis miniature radar, a selective availability antispoofing module (SAASM) GPS receiver, and a barometric altimeter. Real-time embedded software sampled sensor data, controlled GPS receiver tracking loops, and hosted a multisensor optimal estimator whose output position was transmitted via wireless link to a high-resolution personal data accessory (PDA) tracking display. The fully packaged system was field tested in Cambridge, Massachusetts under realistic, GPS-stressed conditions. This paper focuses on the Deep Integration (DI) algorithm design used for the optimal estimation of both position and receiver tracking control. The algorithm was tailored here for intermittent GPS visibility on the ground and in outdoor-indoor-outdoor maneuvers. DI has been used previously for missile guidance, navigation, and control with clear sky view. The PNS required an optimal estimator that combined the nonlinear GPS/inertial DI algorithm with measurements from other sensors. The mission duration here was much longer, and the satellite environment over the ground track was highly variable compared with earlier DI applications. This required the development of strategies for dropping satellites from track after long blockage times and for taking control of newly visible satellites under DI tracking. Here, the advantage of DI tracking is the ability to extract GPS pseudorange information almost instantly if a satellite reappears momentarily from a blockage. This paper reviews the DI approach with stress on the receiver correlator power measurements, nonlinear filter equations, and the calculation of numerically-controlled oscillator (NCO) commands. Specific problems encountered, such as clock error recalculation and numerical issues, are mentioned. Urban canyon performance data demonstrating accurate navigation under sparse GPS availability are also described.

Subjects: PERSONAL NAVIGATION SYSTEM (PNS), GLOBAL POSITIONING SYSTEM (GPS), DEEP INTEGRATION (DI), ALGORITHMS

Lim, S.Y.; Miotto, P.

Actuator Allocation Algorithm Using Interior Linear Programming

Guidance, Navigation, and Control Conference 2006, Keystone, CO, 8/21/2006-8/24/2006. Sponsored by: AIAA (Draper Report No. P-4410)

Abstract: This paper proposes a new algorithm for actuator allocation problems, e.g., reaction wheel torque distribution and jet selection logic. The algorithm is based on an interior-point linear programming (LP) algorithm. Compared with the simplex LP algorithm, the interior-point LP algorithm exhibits several advantages at the cost of reasonably increased computation. They encompass greater robustness to uncertainty in actuator models, smoother actuation command over time, and greater flexibility in incorporating nonlinear operations such as quantization. These advantages stem from the fact that the interior algorithm searches for a suboptimal solution among the interior points of a feasible set and not among the extreme points or corner points of the feasible set as in the simplex algorithm. The proposed approach has been applied to the problem of reaction wheel torque distribution for the attitude control of an autonomous rendezvous and docking (ARD) robotic spacecraft and demonstrated to yield more effective solutions for the actuator allocation problem than a simplex LP approach.

Subjects: ACTUATORS, ATTITUDE CONTROL, REACTION WHEELS, ALGORITHMS, LINEAR PROGRAMMING, AUTONOMOUS RENDEZVOUS AND DOCKING SYSTEMS

Lim, S.Y.

Complementary Roll/Yaw Attitude Controller for Three-Axis Authority Momentum Spacecraft

Guidance, Navigation, and Control Conference, 2006, Keystone, CO, 8/21/2006-8/24/2006. Sponsored by: AIAA (Draper Report No. P-4422)

Abstract: This paper proposes a new attitude controller for Earth-pointing spacecraft that is equipped with a three-axis momentum control device and two-axis attitude sensor such as the infrared Earth sensor. The key technical challenge is to control coupled roll and yaw attitude with only the roll attitude measurement. There exist flight-proven controllers such as the Terasaki controller and the Whecon gyrocompassing coupling yaw damper. However, applying the complementary filtering technique, the paper derives a new roll/ yaw controller that can outperform each individual heritage controller. In particular, the complementary filtering technique is to interweave the heritage controllers in the frequency domain in a way that the heritage controllers complement each other. As a result, the proposed controller can significantly improve both the transient and steady-state performance of a roll/ yaw attitude controller, without additional complexity in guidance, navigation, and control (GNC) hardware/software design and the extra cost in GNC systems. The proposed controller could be used as a primary cheap roll/yaw controller for Earth or planet-pointing spacecraft with infrared two-axis sensors and a backup one during three-axis star tracker sensor blockout or failure.

Subjects: ATTITUDE CONTROL, SPACECRAFT, AUTHORITY MOMENTUM

Marinis, T.F.; Soucy, J.W.; Hanson, D.S.; Pryputniewicz, R.J.; Marinis, R.T.; Klempner, A.R.

Isolation of MEMS Devices from Package Stresses by Use of Compliant Metal Interposers

56th Electronic Components and Technology Conference (ECTC), San Diego, CA, 5/30/2006 - 6/2/2006. Sponsored by: IEEE, Components, Packaging, and Manufacturing Technology (CPMT) Society (Draper Report no. P-4426)

Abstract: Many classes of MEMS devices, such as those with resonant structures, capacitive readouts, and diaphragm elements, are sensitive to stresses that are exerted by their surrounding package structure. Such stresses can arise as a result of changes in temperature, ambient pressure, or relative humidity. We have demonstrated a dramatic reduction in scale factor bias over temperature for a tuning-fork gyroscope by mounting it on an interposer structure within a conventional ceramic chip carrier. Holographic interferometry measurements confirmed that the deformation imposed on a sensor die directly brazed to the package was more than 5 times that of die mounted with an interposer. We have developed several configurations of metal interposer structures for mounting MEMS inertial sensors in standard ceramic chip carrier packages. The interposers are made by first precision chemically etching preforms in metal foil. These preforms are then electroplated with a wire-bondable surface finish of gold over nickel. Next, they are excised from the multi-up foil panel and formed to hold the sensor within the package. The interposers are configured with either three or four tabs for holding the MEMS sensors. Gold bumps are applied to these tabs, and then the sensors are attached with thermocompression bonding. This assembly is attached to the ceramic package by thermocompression bonding to gold bumps on lands of the wirebond shelf. Wirebonds are made to the I/O pads of the sensor to complete its installation.

Subjects: TUNING FORK GYROSCOPES, MICROELECTROMECHANICAL SYSTEM (MEMS), INERTIAL SENSORS, TEMPERATURE, COMPLIANT METAL INTERPOSERS, PACKAGING

Mather, R.A.; Matlis, J.

Alternative Approach to Testing Embedded Real-Time Software

America's Virtual Product Development (VPD) Conference: Evolution to Enterprise Simulation, Huntington Beach, CA. 7/17/2006-7/19/2006. Sponsored by: MSC Software (Draper Report No. P-4424)

Abstract: One of the major challenges facing the engineering community is integrating embedded software controller(s) into a complex electromechanical system. In the early phase of design, this problem is typically addressed with prototype software running on breadboards in an open-loop environment. This leaves a limited number of software developers waiting for available hardware that is also evolving through the hardware design process. Later in the design process, software engineers are provided a closed-loop testing environment using real-time hardware in the loop. Many functional integration issues are discovered at this time and may be intermittent and difficult to repeat. Second, the software debug environment will introduce some level of intrusion that may cause system behavior to diverge from the behavior of the system without the debug environment. A simulation of software execution behavior can be provided virtually by using Instruction Set Simulators (ISS) of the target processor. The Simulation Department at Draper Laboratory has invested several years of development into a simulation framework that can combine continuous time domain simulation and event-driven simulation of digital electronics and Instruction Set Simulators. This framework provides software developers with a non-real-time simulation environment to execute target code running closed loop on a dynamic system created from purely behavioral truth models. The advantages of this virtual system methodology are: it is easily deployed and scalable to a large software development community geographically dispersed, provides software development environment earlier, provides a stable and repeatable software debug environment, software debug capability without any intrusion, and a reasonable ratio of simulated real-time to wall clock time when compared with other purely virtual solutions. The challenges we have recognized and addressed are not unique to Draper Laboratory. Draper will present this methodology, current results, and suggest a vision for the future. In the long term, Draper would like to see companies like MSC provide integrated solutions using commercial-off-the-shelf (COTS) software products like the ISS.

Subjects: SOFTWARE TESTING, EMBEDDED SOFTWARE CONTROLLERS, ELECTROMECHANICAL SYSTEMS, INSTRUCTION SET SIMULATORS (ISS)

Miller, J.W.; Lommel, P.H.

Biomimetic Sensory Abstraction Using Hierarchical Quilted Self-Organizing Maps

Intelligent Robots and Computer Vision XXIV: Algorithms, Techniques, and Active Vision, Boston, MA, 10/1/2006-10/4/2006. Sponsored by: SPIE (Draper Report no. P-4458)

Abstract: We present an approach for abstracting invariant classifications of spatiotemporal patterns presented in a high-dimensionality input stream and apply an early proof-of-concept to shift and scale invariant shape recognition. A model called Hierarchical Quilted Self-Organizing Map (HQSOM) is developed using recurrent self-organizing maps (RSOM) arranged in a pyramidal hierarchy, attempting to mimic the parallel/hierarchical pattern of isocortical processing in the brain. The results of experiments are presented in which the algorithm learns to classify multiple shapes, invariant to shift and scale transformations, in a very small (pixel) field of view.

Subjects: SELF-ORGANIZING MAPS (SOM), PATTERN RECOGNITION, ROBOT VISION, UNSUPERVISED LEARNING, COGNITIVE LEARNING, IMAGE INTERPRETATION, COMPUTATIONAL NEUROSCIENCE, BIOMIMETICS

Putnam, Z.R.; Braun, R.D.; Bairstow, S.H.; Barton, G.H.

Improving Lunar Return Entry Footprints Using Enhanced Skip Trajectory Guidance

Space 2006 Conference, San Jose, CA. 9/19/2006-9/21/2006. Sponsored by: AIAA (Draper Report no. P-4473)

Abstract: The impending development of NASA's Crew Exploration Vehicle (CEV) will require a new entry guidance algorithm that provides sufficient performance to meet all requirements. This study examined the effects on entry footprints of enhancing the skip trajectory entry guidance used in the Apollo program. The skip trajectory entry guidance was modified to include a numerical predictor-corrector phase during the atmospheric skip portion of the entry trajectory. A four degree-of-freedom simulation was used to determine the footprint of the entry vehicle for the baseline Apollo entry guidance and predictor-corrector enhanced guidance with both steep and shallow lofting at several lunar return entry conditions. The results show that the predictor-corrector guidance modification significantly improves the entry footprint of the CEV for the lunar return mission. The performance provided by the enhanced algorithm is likely to meet the entry range requirements for the CEV.

Subjects: CREW EXPLORATION VEHICLES (CEV), ENTRY GUIDANCE, ALGORITHMS , SKIP ENTRY TRAJECTORIES, APOLLO GUIDANCE SYSTEMS

Ricard, M.J.; Nervegna, M.F.

Risk-Aware Mixed-Initiative Dynamic Replanning (RMDR) Program Update

Unmanned Systems North America, Orlando, FL, 8/29/2006-8/31/2006. Sponsored by: Association for Unmanned Vehicle Systems International (AUVSI) (Draper Report no. P-4471)

Abstract: Future naval missions may be executed by multiple, heterogeneous teams of unmanned air, surface, and undersea vehicles. To accomplish these missions with limited manning, the team must autonomously plan and replan cooperative activities associated with the team mission objectives, Rules of Engagement, and operating constraints, taking into account limited and intermittent communications. The team's operator must interact with the team as an entity as well as with individual vehicles within the team. Further, given the limited manning available on ships, it is important to have a common human interface for mission management of heterogeneous unmanned systems. As part of ONR's Intelligent Autonomy program, Draper Laboratory is developing the Risk-aware Mixed-initiative Dynamic Replanning (RMDR) system to deliver such capability. The coastal reconnaissance and monitoring mission, a complex scenario that exercises many of the capabilities being developed, is used for demonstration purposes. Operators provide team-tasking (pre-mission and replanning) inputs, approve generated plans, monitor the mission, retask the team, and provide in-stride target identification. Inputs include: 1) time constraints, 2) risk values for regions (maximum allowable time on the surface, no-go regions, minimum reserves, time-out rules, etc.), and 3) additional activity-specific tasking. For a reconnaissance activity, these include regions of interest, target classes to detect, and the value of gathering information (detection or identification) on the target classes. RMDR is a 4-year effort composed of seven demonstrations, the first six of which are in simulation and the final an in-water demonstration. This paper will present an overview of the RMDR system, results of the first four demonstrations, and plans for future demonstrations.

Subjects: UNMANNED VEHICLES (UV), RISK-AWARE MIXED-INITIATIVE DYNAMIC REPLANNING PROGRAM (RMDR), AUTONOMOUS PLANNING

Rzepniewski, A.K.; Andrews, G.L.

Legged Robot Motion with Explicit Stability Constraints: Theory and Application

Unmanned Systems North America, Orlando, FL., 8/29/2006-8/31/2006. Sponsored by: Association for Unmanned Vehicle Systems International (AUVSI) (Draper Report no. P-4469)

Abstract: Legged robots are known to have mobility advantages over wheeled and tracked ground robots. However, the stability necessary for successful traversal of difficult terrain is rarely explicitly considered when designing motion algorithms. Commonly, stability is a byproduct of walking routines. Learned gaits may be stable over the terrain on which the robot is trained, or stability may be ignored due to the robot configuration, e.g., six-legged robots that can walk in an alternating-tripod gait. The lack of explicit consideration of such an important factor can lead to task failure if the robot is placed in a new or stability-difficult situation, such as traversal of a steep slope or exposure to a sudden external stimulus. In this paper, an angle-based algorithm for real-time optimization of stability is applied to a four-legged robot, the Sony AIBO® . The experimental results show a significant advantage to having this autostabilizing routine. Next, the stability algorithm is integrated with a walk controller to dynamically alter walking gaits to adjust to difficult terrain. This ensures that gaits learned on flat terrain are not applied directly when traversing undulating or steeply-sloped ground. Again, the autostabilizing routine is shown to significantly increase the mobility of the legged robot.

Subjects: LEGGED ROBOT, STABILITY CONSTRAINTS, MOTION PLANNING

Sawyer, W.D.; Prince, M.S

Silicon on Insulator Inertial MEMS Device Processing

MOEMS-MEMS Micro & Nanofabrication, Photonics West, San Jose, CA, 01/21/2006 - 01/26/2006. Sponsored by: SPIE. (Draper Report no. P-4372)

Abstract: During the 1980s and 1990s, the methods used to manufacture inertial MEMS devices could be divided into two groups: bulk and surface micromachining. Institutions that developed high-precision inertial MEMS devices usually employed bulk micromachining processes. This was done to fabricate devices with large proof masses and stiff beams that result in a high scale factor, as well as high drive and sense frequencies. New processes have been developed that are based on silicon-on-insulator (SOI) wafers. These processes combine the advantages of bulk and surface micromachining while enabling the etching of thick proof masses. This paper illustrates the manufacturing and performance advantages of an SOI inertial MEMS process.

Subjects: MICROELECTROMECHANICAL SYSTEM (MEMS); SILICON-ON-INSULATOR TECHNOLOGY; SEMICONDUCTOR DEVICES

Tawney, J.; Hakimi, F.; Willig, R.L.; Alonzo, J.; Bise, R.T.; DiMarcello, F.; Monberg, E.M.; Stockert, T.; Trevor, D.J.

Photonic Crystal Fiber IFOGs

18th International Conference on Optical Fiber Sensors, Cancun, Mexico, 10/23/2006-10/27/2006. Sponsored by: Optical Society of America (OSA) (Draper Report no. P-4444)

Abstract: We have built and tested an interferometric fiber-optic gyroscope made with photonic crystal fiber. This paper reports the test results and examines the advantages of photonic crystal fiber for this type of gyroscope.

Subjects: INTERFEROMETRIC FIBER-OPTIC GYROSCOPES (IFOG), PHOTONIC CRYSTAL FIBERS

Weinberg, E.J.; Kaazempur-Mofrad, M.R.

Large-Strain Finite-Element Formulation for Biological Tissues with Application to Mitral Valve Leaflet Tissue Mechanics

Journal of Biomechanics , Vol. 39, No. 8, 2006, pp. 1557-1561 (Draper Report no. P-4289)

Abstract: This paper presents a finite-element formulation suitable for large- strain modeling of biological tissues and uses this formulation to implement an accurate finite-element model for mitral valve leaflet tissue. First, an experimentally derived strain energy function is obtained from literature. This function is implemented in finite elements using the mixed pressure-displacement formulation. A modification is made to aid in maintaining positive definiteness of the stiffness matrix at low strains. The numerical implementation is shown to be accurate in representing the analytical model of material behavior. The mixed formulation is useful for modeling soft biological tissues in general, and the model presented here is applicable to finite-element simulation of mitral valve mechanics.

Subjects: TISSUE ENGINEERING, MITRAL VALVE, FINITE-ELEMENT FORMULATION

Weinberg, E.J.; Kaazempur-Mofrad, M.R.

On The Constitutive Models for Heart Valve Leaflet Mechanics

Cardiovascular Engineering: an International Journal, Vol. 5, No. 2, March 2005, pp. 37-43 (Draper Report no. P-4288)

Abstract: Large-strain constitutive modeling of biological tissues has grown enormously as a field in the past decade. This paper investigates the viability of the existing models for describing heart valve leaflet mechanics. The properties of the leaflet tissue are discussed, and a variety of constitutive models are addressed. Models based on continuum and unit cell approaches are highlighted as being suited to leaflet modeling.

Subjects: HEART VALVE, TISSUE ENGINEERI