New Planetary Rovers for Long Range Mars Science and Sample Return
There are significant international efforts underway to place mobile robots (rovers) on the surface of Mars.
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There are significant international efforts underway to place mobile robots (rovers) on the surface of Mars.
The Mars Science Laboratory Robotic Arm (RA) is a key component for achieving the primary scientific goals of the mission. The RA supports sample acquisition by precisely positioning a scoop above loose regolith or accurately preloading a percussive drill on Martian rocks or rover-mounted organic check materials. It assists sample processing by orienting a sample processing unit called CHIMRA through a series of gravity-relative orientations and sample delivery by positioning the sample portion door above an instrument inlet or the observation tray. In addition the RA facilitates contact science by accurately positioning the dust removal tool, Alpha Particle X-Ray Spectrometer (APXS) and the Mars Hand Lens Imager (MAHLI) relative to surface targets. In order to fulfill these seemingly disparate science objectives the RA must satisfy a variety of accuracy and performance requirements. This paper describes the necessary arm requirement specification and the test campaign to demonstrate these requirements were satisfied.
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Over the past several decades, NASA Langley Research Center (LaRC) has developed a suite of hardware and software capabilities for robotic in-space assembly. Specific robots include the Lightweight Surface Manipulation System (LSMS), Tendon-Actuated Lightweight In-Space Manipulator (TALISMAN), NASA Intelligent Jigging and Assembly Robot (NINJAR), Strut Assembly, Manufacturing, Utility & Robotic Aid (SAMURAI), and most recently the Assemblers modular robots. Alongside the hardware, software tools such as the Autonomous Entity Operations Network (AEON) and the Baseline Environment for Autonomous Modeling (BEAM) have been developed to enable communication and simulation respectively. These tools have supported foundational research in single and multi-agent control, sensing and perception, trajectory generation, task allocation, and human-machine teaming. This talk will provide a broad overview of these capabilities and go into detail on recent developments made by the Assemblers project to create modular, reconfigurable robots for autonomous in-space assembly.
A study of the interaction between the orbiter primary reaction control system (PRCS) and the remote manipulator system (RMS) with a loaded arm is documented. This analysis was performed with the Payload Deployment and Retrieval Systems Simulation (PDRSS) program with the passive arm bending option. The passive-arm model simulates the arm as massless elastic links with locked joints. The study was divided into two parts. The first part was the evaluation of the response of the arm to step inputs (i.e. constant jet torques) about each of the orbiter body axes. The second part of the study was the evaluation of the response of the arm to minimum impulse primary RCS jet firings with both single pulse and pulse train inputs.
Robots are playing an increasing role in space exploration and in-space servicing. Robotic arms are good for performing in-space tasks such as modular assembly. The SPIDER arm (SPace Infrastructure Dexterous Robot) of the OSAM-1 mission represents an example of a system that can perform modular antenna assembly tasks in environmental conditions that would be dangerous for astronauts. One of the WVRTC activities is to perform independent verification and validation of the SPIDER assembly operations. Space robotic systems adopting large manipulators such as the SPIDER arm are complex to test and verify under normal 1-G conditions. Our work involves proof-of-principle testing of a hardware-inthe-loop (HIL) simulator operating in 1-g conditions, which replicates the motion of the space robot end-effector under the same geometric, kinematic and dynamic conditions, and in response to externally applied forces from its space environment. In particular, our software simulates in real-time the robot dynamics inclusive of flexibility, an important aspect in case of a long robotic arms operating in 0-G conditions. For example, the same oscillatory motions of the space manipulator’s end-effector can be mimicked on ground through our industrial manipulator, allowing us to test the feasibility of complex operation such as assembling modular components.
To study space applications of telerobotics, Goddard Space Flight Center (NASA) has recently built a testbed composed mainly of a pair of redundant slave arms having seven degrees of freedom and a master hand controller system. The mathematical developments required for the computerized simulation study and motion control of the slave arms are presented. The slave arm forward kinematic transformation is presented which is derived using the D-H notation and is then reduced to its most simplified form suitable for real-time control applications. The vector cross product method is then applied to obtain the slave arm Jacobian matrix. Using the developed forward kinematic transformation and quaternions representation of the slave arm end-effector orientation, computer simulation is conducted to evaluate the efficiency of the Jacobian in converting joint velocities into Cartesian velocities and to investigate the accuracy of the Jacobian pseudo-inverse for various sampling times. In addition, the equivalence between Cartesian velocities and quaternion is also verified using computer simulation. The motion control of the slave arm is examined. Three control schemes, the joint-space adaptive control scheme, the Cartesian adaptive control scheme, and the hybrid position/force control scheme are proposed for controlling the motion of the slave arm end-effector. Development of the Cartesian adaptive control scheme is presented and some preliminary results of the remaining control schemes are presented and discussed.
Existing tendon-driven fingers have applied force control through independent tension controllers on each tendon, i.e. in the tendon-space. The coupled kinematics of the tendons, however, cause such controllers to exhibit a transient coupling in their response. This problem can be resolved by alternatively framing the controllers in the joint-space of the manipulator. This work presents a joint-space torque control law that demonstrates both a decoupled and significantly faster response than an equivalent tendon-space formulation. The law also demonstrates greater speed and robustness than comparable PI controllers. In addition, a tension distribution algorithm is presented here to allocate forces from the joints to the tendons. It allocates the tensions so that they satisfy both an upper and lower bound, and it does so without requiring linear programming or open-ended iterations. The control law and tension distribution algorithm are implemented on the robotic hand of Robonaut-2.
This report describes a preliminary investigation of the use of perturbed visual feedback during the performance of simulated space-based remote manipulation tasks. The primary objective of this NASA evaluation was to determine to what extent operators exhibit adaptive strategies which allow them to perform these specific types of remote manipulation tasks more efficiently while exposed to perturbed visual feedback. A secondary objective of this evaluation was to establish a set of preliminary guidelines for enhancing remote manipulation performance and reducing the adverse effects. These objectives were accomplished by studying the remote manipulator performance of test subjects exposed to various perturbed camera-viewing conditions while performing a simulated space-based remote manipulation task. Statistical analysis of performance and subjective data revealed that remote manipulation performance was adversely affected by the use of perturbed visual feedback and performance tended to improve with successive trials in most perturbed viewing conditions.
The performance capability was assessed of operators performing simulated space tasks using manipulator systems which had compliance and force feedback varied. Two manipulators were used, the E-2 electromechanical man-equivalent (force, reach, etc.) master-slave system and a modified CAM 1400 hydraulic master-slave with 100 lbs force capability at reaches of 24 ft. The CAM 1400 was further modified to operate without its normal force feedback. Several experiments and simulations were performed. The first two involved the E-2 absorbing the energy of a moving mass and secondly, guiding a mass thru a maze. Thus, both work and self paced tasks were studied as servo compliance was varied. Three simulations were run with the E-2 mounted on the CAM 1400 to evaluate the concept of a dexterous manipulator as an end effector of a boom-manipulator. Finally, the CAM 1400 performed a maze test and also simulated the capture of a large mass as the servo compliance was varied and with force feedback included and removed.
The concept, design, and features are described of a lightweight, high strength, modular robot manipulator being developed for space and commercial applications. The manipulator has seven fully active degrees of freedom and is fully operational in 1 G. Each of the seven joints incorporates a unique drivetrain design which provides zero backlash operation, is insensitive to wear, and is single fault tolerant to motor or servo amplifier failure. Feedback sensors provide position, velocity, torque, and motor winding temperature information at each joint. This sensing system is also designed to be single fault tolerant. The manipulator consists of five modules (not including gripper). These modules join via simple quick-disconnect couplings and self-mating connectors which allow rapid assembly and/or disassembly for reconfiguration, transport, or servicing. The manipulator is a completely enclosed assembly, with no exposed components or wires. Although the initial prototype will not be space qualified, the design is well suited to meeting space requirements. The control system provides dexterous motion by controlling the endpoint location and arm pose simultaneously. Potential applications are discussed.
Resolved motion rate control is currently one of the most frequently used methods of manipulator control. It is currently used in the Space Shuttle remote manipulator system (RMS) and in prosthetic devices. Position control is predominately used in locating the end-effector of an industrial manipulator along a path with prescribed timing. In industrial applications, resolved motion rate control is inappropriate since position error accumulates. This is due to velocity being the control variable. In some applications this property is an advantage rather than a disadvantage. It may be more important for motion to end as soon as the input command is removed rather than reduce the position error to zero. Local position control is a new concept for manipulator control which retains the important properties of resolved motion rate control, but reduces the drift. Local position control can be considered to be a generalization of resolved position and resolved rate control. It places both control schemes on a common mathematical basis.
The Latching End Effector (LEE) forms part of the Space Station Remote Manipulator System (SSRMS) for which Spar Aerospace Ltd, Space Systems Division is the prime contractor. The design, testing and performance evaluation of the Latching End Effector mechanisms is the subject of this paper focusing on: (1) ambient, thermal and vibration testing; (2) snare/rigidize performance testing and interaction during payload acquisition; and (3) latch/umbilical test results and performance.
New opportunities for the application of telerobotic systems to enhance human intelligence and dexterity in the hazardous environment of space are presented by the National Aeronautics and Space Administration (NASA) Space Station Program. Because of the need for significant increases in extravehicular activity and the potential increase in hazards associated with space programs, emphasis is being heightened on telerobotic systems research and development. The Automation Technology Branch at NASA Langley Research Center currently is sponsoring the Laboratory Telerobotic Manipulator (LTM) program at Oak Ridge National Laboratory to develop and demonstrate ground-based telerobotic manipulator system hardware for research and demonstrations aimed at future NASA applications. The LTM incorporates traction drives, modularity, redundant kinematics, and state-of-the-art hierarchical control techniques to form a basis for merging the diverse technological domains of robust, high-dexterity teleoperations and autonomous robotic operation into common hardware to further NASA's research.
Dexterous manipulation of a robot hand requires the use of multiple sensors integrated into the mechanical hand under distributed microcomputer control. Where space applications such as construction, assembly, servicing and repair tasks are desired of smart robot arms and robot hands, several critical drives influence the design, engineering and integration of such an electromechanical hand. This paper describes a smart robot hand developed at the Jet Propulsion Laboratory for experimental use and evaluation with the Protoflight Manipulator Arm (PFMA) at the Marshall Space Flight Center (MSFC).
Application and requirements for remote manipulator systems for future space missions were investigated. A manipulator evaluation program was established to study the effects of various systems parameters on operator performance of tasks necessary for remotely manned missions. The program and laboratory facilities are described. Evaluation criteria and philosophy are discussed.
Enabling technology needs and other requirements to support space industrialization include: large space structures; fabrication and joining processes; single stage to orbit and heavy lift launch vehicles; nuclear and solar space power systems; robotics, manipulators, and teleoperators; biotechnology in space; artificial gravity; the utilization of lunar materials for construction; and the extraction of oxygen and metals from lunar resources. New initiatives (FY 1978) directly supportive or partly related to space industrialization are listed.