This segment of the program is dedicated to the development of component technologies which have been determined to be of potential benefit in addressing multiple needs of the known robotics requirements. These elements of the program are typically long lead-time items, which may take many years to fully develop and bring to an appropriate level of readiness. However, if successfully completed, these elements typically have the potential of significantly improving or even revolutionizing the state-of-the-art in space telerobotics technology. This portion of the current program includes such elements as fundamentally new robotic joint designs, exoskeleton systems, microtelerobots, and widely-applicable proximity sensor technology. The long term goal of this effort is to develop a series of component technologies which can then be incorporated into larger robot assemblies and full application systems. This effort is phased such that technology components "spin-off" from the component development level to the next level on a regular basis. It is anticipated that this area will continue throughout the life of the program, producing an increasingly-beneficial series of fundamental technologies.
Real Time Learning
Controllers For Enhanced Autonomy
Micro-Electro-Mechanical
System Commutated Miniature Drive Actuators
Low Mass, Compact, Muscle
Actuators
Computer Vision Assisted
Calibrated Synthetic Viewing
Modular Space Robotics
Multiple Interacting
Robots
Control Architectures
Space Operations
The primary objective of this joint NASA/NSF program is to evaluate and further develop new technology enabling free-flying and free-floating space robotic systems to maintain accurate, high performance operation despite large uncertainty about the physical characteristics of the robot and its payload, or about the structure of the environment in which they interact. This will be accomplished by using a new class of adaptive nonlinear control algorithms which use neural network and nonparametric wavelet estimation techniques to significantly extend conventional adaptive solutions for uncertain robotic systems. The specific top-level goals for this program include:
Development of a complete, provably effective
methodology for using real-time neuro-wavelet modeling techniques to allow
spacecraft and space robots to autonomously maintain peak performance in
all operating modes and space environments.
Demonstration and quantification of the performance
of the new technology on simulated space operations using prototype spacecraft
and space robots operating in neutral buoyancy.
Improvement of neutral buoyancy simulation of
space operation by using the new controllers to offset the poorly modeled
hydrodynamic forces which hinder accurate correlation of space telerobotic
operations with terrestrial simulations.
Approach:
Reliable, high performance control of free-flying and free-floating space robots presents challenges well beyond those encountered in more traditional space vehicles. The complexity of these devices, and the necessity of ensuring accurate operation across their entire operating range, requires addressing directly the inherently coupled, nonlinear nature of the dynamics of these systems. Fortunately, due largely to previous efforts in the NASA telerobotic community, the general structure of the coupled dynamics of these systems is by now well understood, as is the structure of exact nonlinear control laws which will permit precise tracking of any user-specified trajectory for the manipulator and its mobile base without excessive control authority.
As model-based algorithms, however, these controllers can be sensitive to the exact mass properties of the manipulator, its payload, and its mobile base; errors in the estimates of these parameters may produce degraded operational performance. Moreover, even in fixed-based robotics, there may be additional, more complex, sources of dynamic uncertainty, especially when the physical source of this uncertainty is itself variable or poorly modeled, such as friction. Space and planetary robots, which by design are operated in hostile and potentially unknown environments, inherently contain a high percentage of this kind of poorly modeled dynamic uncertainty. Finally, damage to the system may cause substantial, unpredictable changes to the structure of the dynamic response of the robot or spacecraft which cannot be accommodated by standard automatic control techniques.
In order to increase the reliability and autonomy of space robots, it is thus desirable to explore control algorithms capable of accommodating these kinds of relatively unstructured (and unexpected) dynamic uncertainty. By appropriately merging new techniques from artificial intelligence and nonparametric estimation with both the adaptive nonlinear controllers used in fixed- base robotics and recently developed algorithms for adaptive attitude control, a new class of algorithms has been developed which provide space robots with just such enhanced adaptive capability. These new algorithms provide an unprecedented level of autonomy, capable of automatically reconfiguring themselves to eliminate the effects of each of the uncertainty sources discussed above, and possess the same theoretical guarantees of accuracy and robust stability as the standard adaptive robotic controllers.
One drawback of these new controllers is the well known ``curse of dimensionality'' of approximation theory, producing computational requirements which would be impractical to implement for a typical seven degree of freedom manipulator on a six degree of freedom mobile spacecraft base given currrent microprocessor technology. An important aspect of this task is thus also to explore techniques for eliminating this defect by incorporating techniques from multivariate wavelet analysis and nonparametric estimation theory to adaptively vary the amount of computation performed, attempting to simultaneously achieve high performance with minimum controller complexity. Although significantly more sophisticated than previous (fixed structure) neurocontrol designs, formal analysis shows that these new designs provide the same theoretical guarantees of stability and effectiveness as conventional algorithms, and can additionally provide at least an order of magnitude reduction in the required computations.
While this new technology has been proven effective, both mathematically and in detailed simulation studies, its true potential can only be evaluated through comprehensive testing on actual free-flying robotic systems. The major thrust of this task is thus to implement these new adaptive control algorithms on existing robots at the Space Systems Laboratory (SSL), and to determine precisely the performance which can be gained as compared to more traditional, nonadaptive approaches. By studying the impact of uncertainty on current robot control algorithms, and by evaluating the ability of the new controllers to adaptively maintain nominal performance, this task will explicitly quantify the benefits of the new technology for NASA.
A successful demonstration of these new control techniques will potentially enable a new generation of "smart" spacecraft and robots, which can easily recover from partial failures and accommodate unexpected changes in their operating environments. The high degree of reliable onboard intelligence afforded by the new controllers will be instrumental in creating the extremely robust, autonomous spacecraft envisioned for the 21st century. Somewhat more conservatively, the technology described can also be used in a passive mode, identifying unexpected changes in the behavior of the system and providing an updated dynamic model to ground personnel for evaluation and further action.
The overall approach for this task is thus to collect data quantifying the ``real-world'' potential of these new adaptive control techniques. This will be accomplished by implementing the new controllers in software on existing SSL robots, specifically MPOD and Ranger/NBV (Neutral Buoyancy Vehicle). Through experiments conducted in the SSL's Neutral Buoyancy Research Facility, MPOD will be used to evaluate adaptive attitude and positioning control, while Ranger/NBV will be used to demonstrate adaptive free-floating manipulator joint control as well as adaptive free-flying coordinated control.
During FY97, implementation of the new controllers will begin on both vehicles, and data collection will begin quantifying the performance on baseline rendezvous and satellite servicing tasks. These data will be compared with the performance of current baseline control laws on the same tasks, contrasting both the accuracy, computational complexity, operator workload, and efficiency (required control authority) of the different approaches. Simulation results suggest that order of magnitude improvements over previous control technology is possible for the first two metrics, and a factor of two improvement is possible for the second two metrics; the experiments will attempt to verify this performance with the existing SSL robotic systems.
Milestones:
June 97 MPOD/Ranger demonstrates new adaptive attitude
controllers. Demonstration of adaptive joint control for Ranger's manipulators.
Jan 98 Ranger demonstrates adaptive free-floating
control.
June 98 MPOD and Ranger/NBV demonstrate adaptive
coordinated 6DOF position and attitude control
Jan 99 Ranger/NBV demonstrates adaptive coordinated
control of base and manipulators.
June 99 MPOD demonstrates adaptive autonomous docking.
Additional Participants:
The National Science Foundation (Robotics and Machine Intelligence Program;
Dr. Howard Moraff, Director) is cooperating with NASA to fund this proposal.
NSF is particularly interested in the theoretical aspects of the program,
and to this end is providing approximately 1/3 of the project budget for
its three year duration.
Points of Contact:
Rob Sanner
University Of Maryland
Space Systems Laboratory
Dept of Aerospace Engineering
College Park, MD
301-405-1928
rmsanner@eng.umd.edu
The objectives of this task are to develop miniature, low mass, highly efficient and compact DC brushless motors that have collocated commutation devices that replace the drive electronics and that are capable of reliable operation at liquid nitrogen temperatures. A further goal is to develop the technology that would allow these motors to operate under the added stress of high duty cycle, long duration applications. Applications abound for difficult aerospace and commercial uses. Specific uses for which the R&D will be tailored is the Exploration of Small Bodies systems under development in the Exploration of Small Bodies activity.
Motors specified for use in mechanisms that are required to perform for long life and high duty cycle under environmentally adverse conditions are usually specified to be brushless motors. This is because brush life is an inherent limitation on the motor. Vacuum or partial vacuum operation of brush motors reduces their life even further, sometimes drastically due to the effects of wear, heat transfer and under some situations, plasma arcing and chemical changes. DC brushless motors, in addition to the elimination of the high wear element component, also operate at lower temperatures since the active windings are in the stator which provides an improved thermal path for dissipation of thermal losses.
Brushless motors, however, require commutation electronics. These electronic drivers include a sensor (commonly a hall effect device), signal conditioning electronics and amplifiers. These components are sensitive to environmental changes, especially temperature and EMC/EMI and are commonly remotely located requiring the many conductors to the motor. They also do not scale easily with the size of the actuator as it is miniaturized.
This proposal will develop a miniature Micro-Electro-Mechanical-System (MEMS) machined device that will replace the commutation electronics with a set of H-Bridges that will serve both to sense rotor position and switch the current between windings. The device will be integrated into a flight development unit actuator in the first year as a proof-of-concept. The actuator will be driven and data collected on the performance.
Mission Applicability:
The Drill and Sampling Systems under development by the Exploration of Small Bodies task will require small motors for the drilling mechanism and the thrust device and for the winches which will secure the lander to the surface. It will be extremely important to maintain the integrity of volitales in the samples that are taken and thus low temperature, reliable actuators to drive the sampling equipment are needed. These mechanisms could be used on the Champollion mission currently under development by NASA Code S.
In addition, numerous applications exist on Rover development programs. These include the motors for the wheels and steering mechanisms as well as those that could be used in the manipulators and various on-board sampling instruments.
This technology has great potential for miniaturizing the motor drive electronics in future small, lightweight spacecraft such as the Discovery and New Millennium Missions. It has potentially wide-ranging use in every conceivable application where DC motors are employed both commercially and in the aerospace industry.
Technical Approach:
The major deliverable for FY '97 will be a brassboard demonstration proving that a MEMS commutation device can be successfully developed and retrofitted to an existing DC brushless motor. This will serve as a pathfinder to the more comprehensive task in FY '98 which, should it be fully funded, will allow the development of a miniature motor system that includes a specially wound motor design that takes advantage of the salient features of the MEMS device, including the capability for "3 phase on" commutation, and full integration of the new device. This motor will be designed to directly meet the requirements of the Exploration of Small Bodies activity.
Focus and Directions:
During Fiscal Year 1997, a micro-H-bridge will be designed and fabricated using MEMS technology. The monolithic switch assembly will be connected to an external zener diode array that provides current flyback capability to the switches. The switch assembly will be capable of switching current through a brushless DC motor in the proper sequence to provide continuous rotation. At the heart of the micro-H-bridge are four current carrying switches. For the target application, each switch will be able to pass 0.5 amperes with minimal voltage drop.
To produce a switch with the proposed current carrying capabilities, extensive device testing and characterization will be conducted. Functional tests, life tests and thermal/vacuum tests will be conducted at the component level. This includes current/voltage load, closing time, break time, bounce characteristics, breakdown voltage, and the effect of inductive voltage loading. The Zener diodes in the H-bridge circuit are present to help reduce and dissipate the currents that cause these voltages. To test the lifetime of the fabricated switches, continuous switching at 1400 Hz will be conducted. Initially, resistive load voltages and currents will be varied from 1 to 50 volts and 0.01 to 1.0 amps respectively. The on-resistance and bounce characteristics will be monitored throughout the life of the switch until failure.
The devices will be integrated into an off-the-shelf DC motor and performance will be characterized by dynamometer testing.
During FY 1998, a motor will be designed that has the correct output torque and speed characteristics to meet the requirements of the Exploration of Small Bodies activity. These motors will be integrated in the third quarter into the drill and winch systems being developed by that task. The motor will be designed and wound to provides access for 3-phase on mode commutation. This will maximize the energy density (energy over volume) for the motor as well as improve efficiency by about 22%. Conventional DC brushless technology does not use this architecture because of the inherent cost of the switching electronics and associated hall effect binary latches, components that will no longer be necessary to include with this new technology. The micro H-Bridge will be designed to incorporate the Zener flyback diodes directly onto the substrate, further miniaturizing the assembly.
In addition to the tests described above, the motors will be run through a complete suite of qualification tests to validate their performance for flight.
In both Phase I and II, design, fabrication and testing of the H-Bridge at the component level will take place in the CalTech MEMS facility. Motor design, device integration and testing will take place at JPL and at AEI.
Major Milestones:
FY 1997
Brassboard Motor Selection and Modeling - Q2
Brassboard Switch Design and Analysis - Q2
Fabrication - Q2
Functional Testing - Q2
Brassboard H-Bridge System Design and Analysis
- Q3
Fabrication - Q3
Functional Testing - Q3
Motor Integration Hardware Design & Fabrication
- Q4
Functional Testing - Q4
Phase I Report Issued - Q4
FY 1998
Motor Design and Analysis - Q1
Motor Fabrication - Q1
H-Bridge System Design and Analysis - Q1
Fabrication - Q2
Integration and Functional Testing - Q3
Environmental Testing - Q3
Life Testing - Q4
Phase II Report Issued - Q4
Point of Contact:
Gerald W. Lilienthal
Jet Propulsion Laboratory
Pasadena, CA 91109
818 354-9082
Gerald.W.Lilienthal@jpl.nasa.gov
The objective of this task is to develop low-mass, compact, low-cost, and low-power-consuming electroactive polymer (EAP) muscle-actuators for space applications as effective alternative to electroceramics. The development of actuators with such characteristics is required for collection and manipulation of surface samples from a rover or directly from a lander. The near term objective is to develop muscles that provide 15% larger actuation force than the FY'96 developed muscle. Also, develop a demonstration 2 DoF arm with a grip end-effector that is driven by an EAP muscle actuator. This development of effective EAP muscle actuators will enable new technologies of end-effectors and manipulators and potentially support shape control of inflatable technology.
Actuation devices are used for many space applications, including release mechanisms, antenna and instrument deployment, positioning devices, aperture opening and closing devices, real-time compensation for thermal expansion in space structures, etc. Increasingly, there are requirements to reduce the size, mass, and power of actuation devices, and to reduce the cost to NASA. Electroceramics (piezoelectric and electrostrictive) offer effective, compact, actuation materials to replace electromagnetic motors. They are used to articulate spacecraft components (e.g. WF/PC II) and to perform various actuation tasks. A wide variety of EAC materials are incorporated into motors, translators and manipulators. In contrast to electroceramics, EAPs are emerging as new actuation materials with capabilities that cannot be matched by the striction-limited and rigid ceramics. EAP materials are lighter and their potential striction capability can be as high as two orders of magnitude more than EAC materials. To take advantage of these polymers' resilience and the ability to engineer their properties to meet NASA articulation requirements, we are developing effective muscle-actuators that are driven by EAP materials. The mass producability of polymers and the fact that electrostrictive materials do not require poling (in contrast to piezoelectric materials) helps produce EAPs at low cost. EAP materials can be easily formed in any desired shape and can be used to build MEMS-type mechanisms (actuators and sensors). They can be designed to emulate the operation of muscles and they have unique characteristics of low density as well as high toughness, electrostrictive strain constant and inherent vibration dampening.
NASA missions planned from 1998 and beyond are considering the use of miniature robotic devices that can potentially employ EAP technology (Mars Exploration and sample collection programs, the New Millennium and others). The goal of this LoMMAs Task is to establish alternative actuation-enabling technology for missions that place tight restrictions on mass, size, power, and cost.
Technical Approach:
This task is led by Dr. Yoseph Bar-Cohen, JPL, and is performed by a team that consists of JPL, LaRC, and the University of New Mexico (UNM). This team uses an interdisciplinary approach to develop low mass, compact, and low power muscle-actuators that are driven by efficient EAP materials. The use of ion-exchange platinum membrane composites and electrostatically driven polymers are investigated for use as low mass muscle actuators to achieve useful levels of displacement and force actuation in telerobotic devices and systems. This effort will demonstrate the capabilities of EAPs and their applicability to muscle-drive mechanisms for futuristic NASA applications in end-effectors and manipulation devices.
EAP materials are developed and method of fabrication, electroding and characterization are being established. Further, efforts are being made to take advantage of the developed actuator to produce mechanisms of manipulation that employ these EAP materials in such devices as end-effector grip actuator and a manipulator arm. The development of the EAP materials and EAP-actuators is done by JPL and LaRC, whereas the materials characterization, actuation mechanism analysis and development, and muscle-actuator demonstration are done by JPL and UNM. Compact muscle actuators that employ EAP materials are being developed to harness the high displacement at low power, mass, and size capabilities of these materials. This phase is conducted in parallel to the development of the EAP material; as the material is improved it will be incorporated into the design of the muscle-actuator. To allow effective design of the muscle, electro-mechanical analysis is being made and the prediction of the actuator components performance will be corroborated. Several muscle-actuator configurations are being considered to select an effective actuation mechanism for EAP materials.
The implementation of the most effective EAP material into a muscle actuator will be conducted in an iterative manner. Muscle configurations and EAP actuators are fabricated and tested to determine their performance envelope and to define requirements for the EAP material. The capability of the muscle actuators in terms of mass, power, size and actuation capability will be determined and compared to reported data for EAC actuators. As a goal for the drive capability of a breadboard EAP muscle, it will be designed to have at least 30% lower mass, 20% lower volume, and 20% lower power requirements, compared to an equivalent Inchworm (Burleigh Instruments) linear actuator that is driven by piezoceramics. The Inchworm was chosen as a baseline because it is the only EAC driven actuator that has been space qualified and is in operation for more than 20 years (Telsat series of 6 Hughes satellites developed under a contract from GSFC in the 70s).
To demonstrate the performance of EAP muscle-actuators we will design and fabricate an end-effector simulating the operation of a hand and a miniature manipulator arm that supports and articulates this end-effector. The demonstrator hand will be designed to represent a mechanism that is determined to be relevant to a flight experiment. Such a demonstrator can form a basis for applications to sample collection tasks, ultra-dexterous and versatile end-effectors, micro-manipulators, miniature platforms, inflatable structures, and deployment devices.
The demonstrator device will be subjected to a series of electrical, mechanical, and thermal tests to determine the performance envelope of the muscle-actuator, and to form a baseline comparison with conventional EAC mechanisms. Because the density of polymers is only about 30% to 50% of the density of electroceramics, the EAP-muscles driven demonstrator is expected to be significantly lighter than can be made with EAC actuators. Further, their capability to produce a strong striction offers an actuation mechanism with large displacements. The load carrying capability of the demonstrator will depend on the success of the efforts to deliver force-actuation and it would require overcoming the limitation of polymers, in terms of stiffness. The potential use of multi-fiber in the construction of muscle-actuators will provide higher stiffness while assuring its resilience and actuation redundancy, i.e., high operation reliability and toughness.
Major Milestones:
FY 1997:
End-effector fingers made of encapsulated ionomer
with enhanced force actuation - Q2
Dual-sided comb-electrode muscle actuator - Q3
Multi-finger end-effector using EAP muscle - Q3
2-DoF EAP driven manipulator - Q4
FY 1998:
Modeling ion-exchange membrane platinum composite
EAP - Q1
Demonstrate muscle action in a robotic operation
- Q4
FY 1999:
Servo-control and miniature EAP drive electronics
- Q3
Low temperature operational EAP muscle - Q4
FY 2000:
Demonstrate multi-DoF dexterous robotic arm - Q2
Integrate EAP-driven dexterous multi-DoF arm into
a sample manipulation testbed - Q4
Point of Contact:
Yoseph Bar-Cohen
Jet Propulsion Laboratory
Pasadena, CA 91109
818-354-2610
Yoseph.Bar-Cohen@jpl.nasa.gov
The objectives of this task are to 1) develop, enhance, and evaluate the computer vision assisted calibrated synthetic viewing (CSV) technology, 2) resolve visual occlusion and limited viewing with harsh space lighting environment, 3) demonstrate reliable ORU (orbital replacement unit) insertion with high precision (1/4") alignment for ISS (International Space Station) onboard and ground control, and 4) transfer CSV technology to JSC ARMSS (Automated Robotic Maintenance for Space Station) testbed for technology assessment and demonstration to the Space Station Program.
Calibrated Synthetic Viewing (CSV) provides the operator with calibrated graphic overlays on actual camera video images. Three-dimensional graphic models are intermittently updated through virtual reality (VR) calibration, that determines the camera calibration parameters and object locations semi-automatically by using model-based edge matching computer vision algorithms. The algorithms utilize the known geometric object models and their salient edges, and do not specifically require arrays of accurately positioned vision targets. This CSV technology has successfully demonstrated an orbital replacement unit (ORU) insertion task within a 1/4 inch alignment precision using two camera views.
This CSV technology with on-going technological enhancements is expected to be very useful for International Space Station (ISS) robotics, in particular, in the ORU insertion operation requiring high precision alignment under limited ISS camera viewing conditions. ISS robotics people have shown interest in this CSV technology for potential incorporation into both on-board and ground-controlled ISS telerobotic servicing.
Approach:
JPL earlier developed an "operator-interactive" or manual virtual reality (VR) calibration that enables reliable and accurate matching of a graphically simulated virtual environment in 3-D geometry and perspective with actual camera views. In this initial "operator-interactive" VR calibration, however, operator enters 3-D graphic object model points and their corresponding 2-D image points manually. As the object moves, the operator must repeat the tedious data entry for object localization quite a few times to achieve high precision alignment. In order to reduce the manual data entry time, in this task, we develop and enhance the computer vision assisted semi-automatic VR calibration by utilizing advanced computer vision algorithms effectively.
Edge matching based vision algorithms are used in our implementation, since edges are easier to detect and more reliable than corner points. Three main components for edge matching algorithms are 1) weighted average local edge detector, 2) weighted least-squares for the edge-based camera calibration and object localization, and 3) robust matching to remove outliers.
The two key elements of the CSV technology enabling high precision alignment are 1) simultaneous update and 2) semi-automatic intermittent model update. The 20-variable least-squares simultaneous update algorithm updates both the camera and the object models simultaneously for given two camera views of two mating objects. This simultaneous update reduces initial camera calibration errors, and is thus essential to achieve high-precision alignment. The simultaneous update is usually performed only when the camera parameters such as camera pose and zoom are changed. After the simultaneous update, semi-automatic intermittent model updates are performed at the intermediate poses (via points) along the path for insertion, refining the ORU model pose through edge matching based object localization. The relative alignment precision increases progressively as the ORU gets closer to the receptacle.
Milestones:
The level 1 milestone for FY'97 is to demonstrate an RPCM (remote power controller module)-like ORU insertion into an RPCM receptacle array under harsh space lighting conditions, and deliver the enhanced CSV technology to the JSC ARMSS (Automated Robotic Maintenance for Space Station) testbed for technology assessment and demonstration to the Space Station Program.
Add a point matching operator interface for easier,
faster initial operator data entry - Q2
effective strategy to cope with harsh space lighting
conditions - Q3
robust edge matching against false matches using
a sequence of previous images - Q3
Demonstrate RPCM-like ORU insertion with an ORU/receptacle
array under harsh space lighting conditions, and deliver the enhanced CSV
technology to JSC (level 1 milestone) - Q4
Perform experiments with quantitative error analysis,
and document the results - Q4
Point of Contact:
Won Soo Kim
Jet Propulsion Laboratory
Pasadena, CA 91109
(818) 354-5047
kim@telerobotics.jpl.nasa.gov
The University of Texas at Austin, in concert with the Robotics Division at JSC and funding support by the telerobotics program at NASA headquarters has undertaken a long term effort to establish advanced component and system technology for space robotics with emphasis on fault tolerance (Butler et al.; Tesar '89; Tesar et al.). The goal is to develop and test technology applicable to all future missions of NASA (lunar base, Mars exploration, planetary surveillance, space station, etc.). This technology would be in balance with the astronaut sharing tasks based on performance, cost, and availability issues. In order to reduce costs, the system would be made up of a finite number of modules (both hardware and software) proven by extensive testing in space. This set of modules would be constantly under technical development so that "tech mods" would be feasible at any time. Also, the repair and logistics function (warehousing of spares in space) would be based on these modules to further reduce costs. This architecture would allow the specification of a robot configuration "on demand" reducing the threat of obsolescence and freeing the mission planner to aggressively use advanced (yet proven) technology.
Technical Plan
Overall, the program at the University of Texas at Austin is concentrating on two levels: the actuator as the driver of the system (equivalent to the computer chip as the driver of computers) and at the system performance level (equivalent to the operating system in personal computers). The objective is to make these two technologies standards for the field of intelligent machines and robotics. This universality is what has created the value in personal computers and increased performance at lower costs. In addition, the program is laying the foundation of a revolutionary approach to control the complex, coupled and highly nonlinear structures involved, to show the continuum from task performance, condition based maintenance, to fault tolerance, all of which depend on a computationally based model reference compared to a sensor identified model. This continuum now becomes unified because of the availability as a commodity of a low cost system controller of several gigaflops.
The following is an overview of the structure of the program at the University of Texas at Austin.
1. Actuator Technology - Present actuator technology is largely unchanged since 1965 except for the utilization of rare earth motors and improved electronic controllers. The goal is to aggressively develop component technology which can be integrated in a carefully designed class of seven standard actuator modules made up of advanced motors, brakes, gear drives, clutches, sensors, electronic controllers, etc., which would not only provide fault tolerance but dramatically improved performance and reliability of space mechanisms (all moving structures such as deployed solar panels, antennae, rovers, robotics, etc.) and to do so at significantly reduced weight. It is now proposed to embed ten sensors to measure all physical functions in the actuator, develop a criteria based model of the module, use data fusion in expanded electronic hardware to maximize performance (and provide condition based maintenance), to extensively vacuum and flight test these modules, and to reduce costs because of standardization while allowing tech mods to occur within the standard.
2. Modular Architecture - A true modular architecture (in the same form as has proven useful for computer systems) can not only reduce life cycle costs (repair, tech mods, logistics spares planning, etc.) but can dramatically increase performance while unfettering the designer to more freely and quickly develop actual operating systems to satisfy future space missions. It is proposed to assemble and reconfigure a broad population of systems from a very small collection of proven and optimized modules produced at lower costs.
3. Task Performance - Long duration space missions suggest an enormous range of physical tasks of great complexity (i.e., numerous specialized tools are now planned as end-effectors for SPDM on ISS). This complexity can be met only by a criteria based decision control structure based on accurate system parameters (using careful metrology) and hundreds of performance criteria. It is proposed to automatically select and prioritize these criteria to provide maximum performance for any given tool selected by the astronaut in EVA (or by ground based control). This step would dramatically reduce the on-line burden on the astronaut and allow them to provide high level oversight in the same way a pilot does in a fighter aircraft.
4. Dual Arm Operations - Due to the lack of frictional stability generated by gravity forces, all parts must be under control at all times to prevent "dropping." This means that either special fixtures (the bane of data based control in manufacturing) must be employed or dual arms must perform the relative motion tasks (force fit assembly, control of ungainly objects that may be easily damaged, removal of insulation wrappings, bending to fit, etc.) that are sure to occur on long duration missions. No real time operation of a dual arm system capable of these tasks exists today. For two manipulators of 7 DOF each, this requires a level of control (precision force and position of 14 inputs to control six relative outputs) far beyond any standard approaches (PID, fuzzy logic, sliding mode control, adaptive control, etc.).
5. Condition Based Maintenance - Having established a model reference control structure comparing actual with predicted performance, it becomes feasible to monitor the system over time to determine when basic maintenance (replacement of actuator components, sensors, controllers, etc.) should be performed and to provide an archival record of that performance. This should improve the system's reliability, reduce the cost of operation, prevent unexpected failures and provide lessons learned for the operator and the designer of future components, as well as, to the mission planner for module selection to make up systems for other tasks.
6. Fault Tolerance - Fault tolerance is virtually non-existent in present robotics development for space. A full architecture for fault tolerance involves four levels (alternate physical pathways) of mechanical structure to avoid faults. The UT Austin program strongly recommends a 10 DOF manipulator system (level III) made up of dual actuators (level I). This level of choice (20 actuator inputs to control six outputs) can only be achieved by a criteria based decision making structure based on performance indices composed of hundreds of physical criteria (which demands an extremely high computational capacity). Such superior system controller technology (several gigaflops) is emerging as a commodity (at reasonable cost) in the near term. Hence, fault tolerance is not only feasible but it can only be achieved through a comparative analysis between an accurate and complete analytical model reference and a sensor based actual model of the system. This makes Fault Detection and Isolation (FDI) possible. No other method of control does.
7. Man-Machine Interface - Because of the extraordinary value associated with the time of the astronaut, the interface between man and machine is being recognized as a key resource to maximize overall performance and to train (skill) the system's operator. Very complex operations (dual arms, disturbance rejection, unstructured tasks, precision assembly at small scales, multiple slaves, obstacle avoidance, etc.) require an exceptional level of dexterity and task performance. This is best achieved by setting operational priorities (selection of criteria, performance indices, threshold levels for fault identification, etc.) by human intervention. It is completely feasible to automatically set these priorities by either defining the task (ORU changeout) or picking up the active tool specifically designed for a given task. Specially designed actuators, human augmentation software, fault tolerance, etc., must be built into future manual controllers to maximize the task performance of an increasingly complex slave manipulator technology.
Specific Space Applications
The need to increase performance of space robot systems, better augment the astronaut in EVA, improve the availability of the robot system and still reduce costs, calls for a full architectural initiative for the modular structure (reduced cost), configuration management (best performance) and fault tolerance (fail operational) of space robot systems. The primary goal is to assist the human operator in managing the extraordinary complexity of the deployed resources (say 20 DOF of the dual arm SPDM attached to the RMS end-effector) by providing guidance on the best kinematic configuration to supply enhanced performance against an array of physical tasks. The secondary goal is to ensure that all required operational functions are met even under one or more faults so that repair and maintenance can be deferred until the system can be taken off the critical path of the mission. To do so requires a revolutionary technology envisioned in this proposal representing independent layers of actuator resources which can be arranged in a broad spectrum of configurations to either maximize task performance or to tolerate a failure by automatically reconfiguring around the fault without significantly reducing the system's performance for a short period. These goals must be achieved without having redundant resources dormant (until called for due to a fault). Hence, all resources will be used at all times to maximize performance. Performance will be degraded (by some marginal degree) only under a fault.
The Robotics Research Corporation has produced a sophisticated modular manipulator of high smoothness and resolution which is widely used in NASA laboratories as a demonstrator. The ARMSS facility at JSC is made up of two 7 DOF RRC arms on two separate precision 2 DOF pedestals to make up a valuable demonstrator of the technology for space station operations. A 17 DOF system (two 7 DOF arms and a 3 DOF torso by RRC) has been made available by Grumman Corporation to the University of Texas at Austin. Both of these systems will be used to integrate and evaluate much of the technology described in this program plan. The goal is to test the most advanced control software for performance, condition based maintenance and fault tolerance in real time (say 10 milli-sec.) and to do so with improved operator intervention.
Based on a new software architecture (OSCAR) developed at the University of Texas at Austin, it now becomes feasible to embed all SPDM system parameters (mass, compliance, actuator controllers, etc.) in this generalized software to predict task performance of SPDM for a wide range of physical tasks using a given set of end-effector tools. It is recommended that these simulations be demonstrated at the University of Texas at Austin, but also in the ARMSS facility at JSC. Specific attention would be given to configuration management (what criteria to match which tools, where to locate the base of SPDM for best task performance, which actuators to use, which overall positions provide best stiffness, load capacity, etc., and what to do if one or more actuator, sensor, tool, etc., partially or totally fails). Scenarios could be studied to become the basis for astronaut training where stress tests would accelerate emergency response to unusual operating conditions (which will occur).
Also, JSC is deeply involved in the development of a small scale dual arm system with dexterous end-effectors called Robonaut (much smaller than SPDM and perhaps 50% the size of Ranger) which is to directly duplicate (or exceed) the capability of the astronaut in EVA and be a direct partner of the astronaut (an EVA assistant). Larry Li, JSC program monitor for the University of Texas at Austin, has asked that we support the design effort of Robonaut by working with JSC personnel on the following:
1. Dual Arm plus Tail control: configuration management for best load distribution, best body/arm/hand pose for a given task, self-motion of system attached at three points, back drivability, etc.
2. Small, high torque electric actuators for Robonaut.
3. Teleoperator performance study, enhanced man-machine interface, shared and supervisory control, etc.
These suggestions take advantage of many of the strengths that has been developed at the University of Texas at Austin under NASA funding. We will endeavor to meet these suggestions as well as possible under our present limited funding.
Major Milestones:
FY 1997:
Architectural study of new actuator module
for space operations - Q3
Study of new gear surface technology for new actuator
module - Q4
Complete design of fault-tolerant clutch - Q3
First level demonstration obstacle avoidance -
Q3
Complete report on redesign of electronic actuator
controller - Q1
First level development of criteria fusion for
fault-tolerant redundant manipulators - Q3
Operational test of criteria fusion for fault-tolerant
redundant manipulators - Q4
FY 1998:
Preliminary redesign of new actuator module for
space operations - Q2
Implement and evaluate new fault detection and
isolation algorithms - Q3
Object-oriented software architecture for decision
and control with fault tolerance. - Q4
Complete second generation obstacle avoidance algorithms
- Q3
Preliminary study of intelligent and failure responsive
architectures - Q2
Preliminary design of intelligent and failure responsive
architecture at the actuator level - Q3
Implementation of intelligent and failure responsive
architecture at the actuator level FY98, Q4
Point of Contact:
Del Tesar
University Of Texas At Austin
Department Of Mechnical Engineering
Austin, TX 78712
(512) 471-3039
tesar@mex.cc.utexas.edu
TASK 1: Demonstration of Physically-Based Planning and Control for Rovers
MIT's past work has developed a planning method for robotic systems, such as might be used for planetary exploration. The method (Action Module Methodology - AMM) is based on automated assembly of action modules using a physically-based hierarchical search approach. During FY 97/98, the approach will be applied to rover configurations with the objective of allowing them to use fully their mobility capabilities in physically challenging environments. Ideally, this would permit rovers to achieve a more aggressive behavior with reduced risk. This work will include experimental demonstrations. Specific objectives are:
1. Complete fundamental studies of the rapid planning procedure based on the hierarchical action modules methodology, (AMM), including fundamental studies of its Genetic Algorithm component. (December 1997)
2. Build a simulation of a rover, the JPL Light Survivable Rover (LSR) performing representative missions, including those with physically challenging terrain, such VL-2 or cliff-terrains. This work will include the development of physical models and simulations of the LSR in a planetary environment. (January 1998)
3. Integrate the above simulation with the MIT AMM software to study the effectiveness of AMM planning as applied to the various rover tasks. Refine and simplify physically-based rover action modules for possible on-board implementation. The effectiveness of AMM based planning will be evaluated and demonstrated in a laboratory environment at MIT. (March 1998)
4. Design and perform an experimental demonstration on a JPL experimental rover, with the assistance of the JPL staff. (June 1998)
TASK 2: Preliminary Design Studies of Re-Configurable Planetary Robotic Systems
In close coordination with JPL, the work will explore the development of design methodologies that will allow planetary rovers to physically adapt themselves so as to be appropriate for the terrain and situation they face (self repair, self re-planning, trap recovery, physical adaptability). The investigation will draw from the previous and current MIT work on physically-based modular designs. Specific objectives are:
1. Study, identify and document performance and technological requirements for re-configurable rovers, and determine new useful mission capabilities that can be enabled with such rovers that cannot be achieved with more traditional rover designs. (January 1998)
2. Investigate and document the means to achieve re-configurable systems, including new hardware configurations and subsystem concepts. (March 1998)
3. Perform fundamental studies of re-configurable rovers, using simple tests and physics-based design rules to achieve the rover reconfiguration; conduct and document a comparative evaluation of anticipated vs achieved enablements. (June 1998)
TASK 3: High Precision Control & Physics-Based Planning Methods for the Manipulation of Highly Irregular Objects.
1. Lightweight space manipulators require drives with high gear-ratio transmissions, which can result in high joint friction that can seriously degrade system performance. Further, problems associated with lubricant outgassing in space can exacerbate this problem. In this task, MIT will investigate and document the extension of its very high-precision BAST control methodology to tasks requiring contact with a relatively stiff environment. (January 1998)
2. An example will be investigated and the results documented of the problem of packing of rock samples into a return container, as might be used for a Mars sample return mission. In this task, the fundamental issues of this problem will be explored. Physics-based planning algorithms that can be easily implemented on small computers for on-board implementation will be investigated and tested in a laboratory environment. (May 1998)
Steve Dubowsky
Massachusetts Institute of Technology
Cambridge, MA 02139
(617) 253-2144
dubowsky@mit.edu
Multiple Interacting RobotsThe Aerospace Robotics Laboratory (ARL) at Stanford University is pursuing five fields of research that are either funded by or relate to the NASA TRIWG program, as discussed below. Each section discusses the specific level of TRIWG funding both for student support and for experiment-specific equipment. TRIWG funding also provides a portion of the support for the lab-wide infrastructure (about 20% of the FY '97 TRIWG money supports about 40% of the infrastructure costs). Infrastructure includes maintenance of the engineering workstation computer network, one half-time mechanical designer, one electronics technician, one half-time ARL administrator, and various office supplies/copy services etc.
HUMAN TASK-LEVEL CONTROL OF FREE-FLYING SPACE ROBOT SYSTEMS
This research area is dedicated to the development of experimental Free-Flying Space Robots that can be directed by a human at an intuitive, task level to perform typical space operations. There are three two-armed prototype space robot vehicles, one free-flying camera platform, and one passive GPS target vehicle employed for experimentation. There are two major focus areas of these experiments. The first area is concerned with the development of the Object-Based Task-Level Control architecture including optimizing the use of human perception capabilities and integrating new real-time computer planning algorithms that enable sophisticated semi-autonomous missions. The second is concerned with multiple robot cooperation for assembly, formation flight, and long-baseline interferometry. The fundamental issues include sensing, control, and inter-vehicle communication for tasks such as the AERCam mission, the New Millennium program, and cooperative inspection and assembly for the International Space Station using a fixed-base manipulator and free-flying robots.
Focus and Directions:
FY 96
Human perception in unfamiliar environments: Identify, track, and manipulate objects about which the robot has no prior knowledge, drawing upon the human operator's perceptive power to direct cogent object modeling through simple visual interaction. This capability will enable robots to effectively operate and manipulate objects in unfamiliar environments, while the human directs, at a high level, tasks to be performed with the object. In column 3 of Table 1a, the performance of the new experimental system operating in an environment where object information is deficient is compared directly to that of the same hardware platform performing identical tasks with objects whose characteristics are already known exactly a priori (as shown in column 1 of table Ia). Such metrics as object capture success rate, and absolute positioning accuracy are quantified for operation in the more challenging environment where no prior knowledge of object characteristics is present.
Real-time task planning in a dynamic environment: Maneuver a Free-Flying robot quickly and efficiently through a dynamically changing obstacle field. In particular, intercept and capture a target object that is moving through the obstacle field along a path that is not known beforehand, an may have changed after pursuit was underway. This experiment has demonstrated ongoing real-time task planning: the capability to perform, update, and improve sophisticated optimal trajectory generation in real-time on a robotic system moving through a changing environment. The Free-Flying robot will be able to react to unforeseen changes in the world around it, including impulsive disturbances to the moving target itself, while always flying in a time- and fuel-efficient manner.
FY 97
Space-vehicle formation flying control: Formulate and compare control strategies for multi-vehicle autonomous formation flying. Demonstrate for the case of a three-vehicle formation using the two-armed free-flying space robots. Use overhead vision as the initial sensor and add GPS and possibly laser sensor systems. This research is motivated by two future NASA New Millennium missions: E0-1 for Earth orbit formation flying and the new millennium interferometer for deep space optical interferometry. An integral component of this research will be to identify metrics for comparing formation flight control performance.
External Work Systems: Build free-flying camera platform (similar to AERCam) capable of supporting small CCD cameras. Demonstrate the ability to control the camera platform relative to a two-armed free-flying space robot throughout a capture task and provide real-time video of the task execution.
HIGH-PERFORMANCE CONTROL OF VERY FLEXIBLE MANIPULATORS IN SPACE
This area of the research pursues general advances in automatic control theory, each accompanied by a proof of concept demonstration, that can be applied to greatly improve the control of a variety of robotic and other very flexible dynamic systems such as the RMS and its successors. This research is primarily conducted on three hardware platforms: a Single-Link Flexible Manipulator with complex dynamic payloads, a Two-Link Flexible Manipulator that carries a fast Mini-manipulator, and prototype Space Station Manipulation system consisting of a large macro-manipulator, dynamically similar to the RMS, that carries two cooperating mini-manipulators similar to the DRS. There are three major thrusts of this research: Adaptive Control of Manipulators with Complex Dynamic Payloads, End-Point Impedance Control for a multiple-link Flexible Manipulator carrying a Fast Mini-Manipulator, and a Prototype Space Manufacturing Workcell used to study the control and operations issues associated with the Space Station Remote Manipulator System (SSRMS) and Dextrous Robotic System (DRS).
Focus and Directions:
FY 96
Unknown dynamic payload: Demonstrate ability to achieve high-performance control of flexible structures with unknown, multiple-D.O.F. dynamic payloads. An example application is the shuttle RMS manipulating a satellite that contains fuel or has flexible appendages such as large antennas or solar arrays.
To obtain precise end-point control of flexible structures, an accurate dynamic model of the total system must be available. However, an unknown dynamic payload results in an unknown total system model, which degrades the closed-loop performance achievable by a fixed controller.
The result of this research will be an on-line adaptation that identifies the total system model and modifies the control system accordingly. Specifically, this adaptation is expected to lead to a precise, robust control (see metrics table IIa) and a closed-loop bandwidth which is a factor of three greater than that achievable through conventional control methods (i.e. collocated control).
Contact with a static environment using a Macro/Mini-Manipulator with Structural Flexibility: Use a flexible macro-manipulator carrying a fast mini-manipulator to demonstrate stable contact with an object in the environment and regulation of the contact force between the tip of the manipulator and the object. This work is intended to resolve several fundamental control issues that are of concern to attached servicer robots currently under development.
This research will demonstrate force control bandwidth at least a factor of 4 greater than current collocated control methods, and will demonstrate for the first time ever impedance control at the tip of a flexible manipulator carrying a fast mini-manipulator.
FY 97
Unknown, multiple degree-of-freedom, dynamic payloads: Demonstrate ability to achieve high-performance control of flexible structures with unknown multiple degrees-of-freedom dynamic payloads. An example application is the Space Shuttle's RMS manipulating the Hubble Space Telescope which contains (potentially sloshing) fuel and has flexible appendages such as solar arrays.
Although the current means of controlling the RMS does remain stable in the presence of unknown dynamic payload modes, very little active damping is applied to these modes. Consequently, when these modes become excited, operation must be suspended until the natural damping has reduced the excitation to an acceptable level. The goal of this research is to develop an adaptive controller capable of self-tuning in response to unknown dynamic payloads. As compared to the conventional technique of control on the RMS, the resulting controller will achieve an order of magnitude improvement in time to damp the dynamic modes.
In addition, this research extends the capabilities of traditional on-line adaptive controllers in two ways: 1.improved system identification by exploiting known subsystem information to reduce greatly the number of unknown parameters required in describing the total system; 2.integration of errors in system identification results into the control design process to ensure closed-loop robustness where uncertainty is high.
Compared to traditional adaptive controllers, these advances are expected to lead to at least a factor of two increase in speed of convergence of the on-line adaptation.
Contact with a dynamic environment using a Macro/Mini-Manipulator with Structural Flexibility: Using a flexible macro-manipulator carrying a fast mini-manipulator, demonstrate contact with an object that is free to move in the environment. Additionally, use the same hardware system to contact and stop the translation of an object moving in the environment, simulating the rendezvous and capture of a satellite by the RMS carrying a fast mini-manipulator. The contact force must remain within a specified tolerance at all times.
This research will demonstrate new capabilities not currently possible with operational NASA robotic systems. The rendezvous and capture of a moving satellite, similar to the Intelsat VI rescue mission, requires not only position control, but high-quality Impedance Control. Impedance Control uses a linear combination of position, velocity, and force as a performance index for the compensator. Manipulators controlled with Impedance Control are capable of moving smoothly from contact to non-contact conditions, and are the key to implementing assembly primitives.
This year the research will build on the increased force-control performance demonstrated in FY96 to show the ability to rendezvous and capture a moving object: a task not previously possible.
Prototype space assembly workcell: This system will be used to study the control and operations issues associated with the Space Station Remote Manipulator System (SSRMS) and Dextrous Robotic System (DRS). The focus of this work is to study the issues associated with development and human task-level control of a Robotic Workcell in Space. This research area will build on the theory demonstrated by free-flying robot to free-flying robot assembly and extend it to the case of robots with different capabilities: One fixed-base and one or more free-flying robots. The dynamics and control of the combination--encompassing new planning, remote operation, user interface, and control issues--will be the technical focus of the research.
The first year's work will focus on evolving the macro/mini-manipulator hardware system from its current configuration, used to study planning issues, to a configuration suitable for examining manipulation issues. A new, more capable, mini-manipulator must be designed and fabricated, and the macro-manipulator modified to support the new mini-manipulator. Initial control experiments will be completed in FY 97.
CONTROL OF REDUNDANT, 3D, SEVEN DEGREE-OF-FREEDOM MANIPULATOR
This focus area of research concentrates on extending object-based task-level control to redundant, 3D robots. This effort is a collaboration between ARL researchers and researchers from the Intelligent Mechanisms Group (IMG) at NASA Ames Research Center. Many different algorithms exist to resolve motion redundancy based on kinematic constraints such as object avoidance, joint limits and joint-singularity avoidance. There are several 'dynamic' algorithms that minimize kinetic energy, joint forces, and acceleration profiles. However, these approaches disregard the task when constraining the internal motion of the robot. What would be desired is to decouple the task-control specification and the internal robot control into two independent problems. Thus, the end user can begin by specifying things like control bandwidth of the task, compliant and non-compliant directions of motion, etc. The robot will then configure itself and its motion to meet these dynamic constraints which were developed independent of the robot. The results of this project are applicable to many programs, specifically to control of the manipulator mounted on the Marskahod robot, the Ranger robotic system, and to the Space Station DRS. It is anticipated that this testbed will become the basis for the joint ARL/Ames project to develop autonomous control for the DRS.
Focus and Directions:
FY 97
Demonstrate improved task performance as a result of the new redundancy management scheme. This will be demonstrated by comparing current state-of-the-art solutions with the new algorithms. Specific comparisons that will be made: task bandwidth in the entire workspace, time to complete given tasks, and stability of system as manipulator moves through singularity. All of the performance measure will be made on the experimental system consisting of the Robotics Research Arm.
Build multi-use end-effector for the Robotics Research manipulator. This will be used for force contact tasks that will help to quantify performance of new algorithms.
CONTROL OF FREE-SWIMMING UNDERWATER ROBOTIC SYSTEMS
This research area is dedicated to the development of free-swimming underwater vehicle/arm robot systems that can be directed at an intuitive, task level to perform typical ocean science operations. It is a full 3D implementation of TLC in a free-swimming robot. This research effort is a cooperative venture with the Monterey Bay Aquarium Research Institute (MBARI) of Moss Landing, California, and involves development of a highly autonomous, unmanned, untethered, and one- or two-armed vehicle. OTTER, the first vehicle of its class, was launched in 1994 by the ARL/MBARI team. Specific research initiatives include three-dimensional visual servoing and mosaicking, fully-coordinated arm-vehicle control, and underwater object acquisition. A project is planned between researchers at NASA Ames Research Center, MBARI, and ARL to demonstrate virtual-reality control of the free-swimming underwater robot in an environment where there will be large time delays between operator and robot. This research is relevant to NASA's Space objectives in two ways. First, the underwater environment provides an ideal environment for demonstrating vision sensing and vehicle control in 3 Dimensions. Second, the underwater environment provides the first experience with telescience at a distance. These experiences will enable scientists to understand the potential of robotic exploration of distant planets.
Focus and Directions:
FY 96
Demonstrate high-level autonomy with automatic retrieval of underwater objects by the OTTER underwater test vehicle.
Demonstrated ocean-floor station keeping on the MBARI's operational Remotely Operated Vehicle (ROV), Ventana, using a novel real-time vision sensor. Make this technology available for Ventana operations on a daily basis.
FY 97
Demonstrate with the OTTER underwater test vehicle the real-time creation of video mosaics along an unconstrained vehicle path in six degrees of freedom.
Demonstrate the use of vision as a global position sensor in real underwater vehicle control systems.
Demonstrate coordinated maneuverability of the OTTER vehicle with multiple-degree-of-freedom manipulators.
Demonstrate, in an operational environment, constrained mosaicking of the ocean floor on the Ventana ROV using the real-time vision sensor. Make this technology available for Ventana operations on a daily basis.
TASK-LEVEL CONTROL OF AN UNMANNED HELICOPTER
This research area is dedicated to the development of semi-autonomous unmanned helicopter systems. The research focuses on the combined use of Differential Carrier Phase GPS and computer vision techniques. A semi-autonomous vehicle controlled by a combination of vision and GPS sensing will demonstrate all of the fundamentals necessary for the AERCAM program. The GPS capabilities will then be extended to demonstrate precision formation flying of two or more vehicles, providing a basis for multiple spacecraft coordinated science missions such as those proposed by the New Millennium Program.
Focus and Directions:
FY 95
Demonstrated -- at a National Contest, which we won, stable autonomous hover and navigation of model helicopter using differential carrier phase GPS as the only sensor for both position and attitude sensing and control.
FY 96
Demonstrate stable autonomous control and navigation of a model helicopter using a sensing system integrating both differential carrier phase GPS and real-time computer vision.
Demonstrate the ability to track an object moving on the ground using the vision system developed by ARL researchers for the ARL/MBARI underwater robotics program.
FY 97
Demonstrate autonomous mapping of environment using a combination of GPS and vision sensor information. This combination of sensors will enable the system to follow task-level commands such as "hover over this spot" and "track that object."
Demonstrate GPS as a system identification tool for helicopters.
Demonstrate Endpoint control of a slung load under a helicopter, using on-board vision as the primary sensor.
Point of Contact:
Robert Cannon
Stanford University
Aeronautics & Astronautics Department
Stanfod University, CA 94305
(415) 723-3602
cannon@sun-valley.stanford.edu
Space OperationsTechnology development programs must balance the "push" from the technologists with the technology "pull" from the operations side. Some fields (space propulsion, for example) have no problems balancing these two forces: it is very clear exactly what the utility is of an additional second of specific impulse in any existing or future transportation system. Space robotics, on the other hand, is unfamiliar enough to the operations community that the "pull" tends to be both weak and erroneous. For example, in an era when the only operational space robot is the Shuttle Remote Manipulator system, the operations community tends to only look for robots that are very similar to the RMS. [This finally explains SPDM! - ed. comment] This "pull" tends to ignore technologies with much greater potential for positively impacting future operations. At the same time, it is important for the technologists to be continually reminded that the reseach is focused at improving space operations, rather than just pushing the state of the art. For this reason, it is critically important that a research community such as Space Telerobotics must have an evaluation and demonstration function, so that advanced technologies may be quickly and inexpensively showcased to the operations community, and new technologies tested in realistic simulation conditions to compare their performance directly against existing capabilities. For EVA Robotics, this activity is encompassed within the Space Operations research program at the University of Maryland Space System Laboratory.
Based at the University of Maryland Neutral Buoyancy Research Facility, this research topic encompasses the development of advanced technologies for space telerobotics and for ground-based simulations, and the incorporation of these technologies into integrated telerobotic systems for neutral buoyancy simulation of space operations. In the underwater environment, which provides one of the best long-term unrestricted simulations of microgravity available, complete telerobotic systems are tested, both alone and in cooperative activites with human subjects, on realistic end-to-end space tasks such as servicing, assembly and maintenance. Results from these simulations are compared with existing operational capabilities (often extravehicular activity, or EVA) to better understand the capabilities and limitations of the telerobotic systems. These integrated systems are easily modified to incorporate new technologies, and are inexpensive enough to be retired and replaced when new technologies have outmoded the basic unit.
Approach:
The Space Operations task consists of two basic elements: development of advanced technologies and development and evaluation of integrated systems concepts. These areas are further described in the following sections.
Development of Advanced Technologies: In a real way, this title is all-encompassing of the entire NASA research program. In actuality, advanced technology development under the Space Operations topic is restricted to a few particular areas of SSL expertise, such as advanced servo-level control, human-in-the-loop control, and advanced instrumentation systems for human factors research and for underwater simulation. These technologies are developed in theory and benchtop proof-of-concept systems; they are then ported onto the neutral buoyancy vehicles for understanding their impact on system performance in realistic tasks and environments. As part of this research area, advanced instrumentation, navigation, and flight control systems are under development to increase the fidelity of the neutral buoyancy environment, and to actively overcome inaccuracies in the simulation medium, such as the effects of hydrodynamic drag. This section of the Space Operations topic also includes a significant effort in space human factors, both to understand human capabilities as the ultimate comparison metric for robotics, as well as to better understand the design of human interfaces for telerobotic control, both ground-based and in microgravity.
Development and Evaluation of Integrated Systems Concepts: This segment of the research topic deals with the development and testing of integrated telerobotic systems. Rather than studying manipulation by stacking blocks on a laboratory bench, this research topic addresses specifics of how to perform realistic tasks, such as changing out Hubble Space Telescope components, in a simulated weightless environment (neutral buoyancy). This approach provides a sharp focus for the technology research, as well as providing valuable lessons on what it takes to bring disparate technologies (manipulators, mobility systems, control interfaces, software architectures) together into a functional system to perform operational tasks. In some cases, the proof-of-concept systems developed in this task (SCAMP, Ranger preliminary designs) have led to focused research topics designed above. In other cases, results from system testing have demonstrated significant limitations to the concept, and the test vehicle was quickly retired or recycled into a subsequent development effort. Another unique feature of this research section is a significant focus on human-robotic cooperation. Results from the past decade of research has unequivocally indicated that the most productive system for performing space operations is a mixture of on-site humans and telerobots, each performing the tasks to which they are best suited. One of the most important future research topics to be explored under Space Operations is the further investigation of cooperative roles between humans and machines in future space activities.
Focus and Directions:
FY94 Collect data base on advanced telerobotic
operations using neutral buoyancy; develop an advanced work site simulation
for quantifying performance of integrated telerobotic operations; test EVA/telerobotic
cooperative tasks at NASA Marshall Neutral Buoyancy Simulator
FY95 Operate existing telerobotic systems
to collect data base on advanced telerobotic operations in neutral buoyancy;
develop an advanced work site simulation for integrated telerobotic operations;
test EVA/telerobotic cooperative tasks at NASA Marshall Neutral Buoyancy
Simulator
FY96 Utilize Ranger technology for rapid
prototyping and operations testing of advances concepts for telerobotic
and EVA/telerobotic space operations
FY97 Use results from Ranger flight experiment
and Ranger NBV to develop extensive data base on telerobotic performance
in space operations tasks
Major Milestones:
FY 1997:
Development and testing of a neutral buoyancy
flight control system with full six-axis compensation for hydrodynamic effects
Publication (via the World Wide Web and
CD-ROM) of the first version of a hypertext-based data base on human and
telerobotic performance in space operations tasks
Lab-based demonstration of advanced technologies
for robotic augmentation of specific body joints of EVA subjects
Continued testing of Ranger NBV to quantify
effects of human-telerobot cooperation in space operations tasks
FY 1998:
Development of a prototype system for virtual
reality simulation of EVA operations including neutral buoyancy simulation
of microgravity
Advanced technology testing for creating
a Ranger-class servicing vehicle at 1/3 the current size and 20% the current
mass
Release of version 2.0 of the hypertext
data base on space operations experience
Testing of microgravity work site design
parameters based on an underwater force reflecting hand controller
Point of Contact:
Dave Akin
University Of Maryland
Space Systems Laboratory
Dept of Aerospace Engineering
College Park, MD
(301) 405-1138
dakin@ssl.umd.edu
with any comments, criticisms
or corrections for this page.