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At least 865 records · Page 48

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NASA NTRS1990

An adaptive inverse kinematics algorithm for robot manipulators

An adaptive algorithm for solving the inverse kinematics problem for robot manipulators is presented. The algorithm is derived using model reference adaptive control (MRAC) theory and is computationally efficient for online applications. The scheme requires no a priori knowledge of the kinematics of the robot if Cartesian end-effector sensing is available, and it requires knowledge of only the forward kinematics if joint position sensing is used. Computer simulation results are given for the redundant seven-DOF robotics research arm, demonstrating that the proposed algorithm yields accurate joint angle trajectories for a given end-effector position/orientation trajectory.

Colbaugh, R.↗

NASA NTRS1990

Implementing real-time robotic systems using CHIMERA II

A description is given of the CHIMERA II programming environment and operating system, which was developed for implementing real-time robotic systems. Sensor-based robotic systems contain both general- and special-purpose hardware, and thus the development of applications tends to be a time-consuming task. The CHIMERA II environment is designed to reduce the development time by providing a convenient software interface between the hardware and the user. CHIMERA II supports flexible hardware configurations which are based on one or more VME-backplanes. All communication across multiple processors is transparent to the user through an extensive set of interprocessor communication primitives. CHIMERA II also provides a high-performance real-time kernel which supports both deadline and highest-priority-first scheduling. The flexibility of CHIMERA II allows hierarchical models for robot control, such as NASREM, to be implemented with minimal programming time and effort.

Stewart, David B.↗

NASA NTRS1990

Task decomposition for multilimbed robots to work in the reachable-but-unorientable space

Multilimbed industrial robots that have at least one arm and two or more legs are suggested for enlarging robot workspace in industrial automation. To plan the motion of a multilimbed robot, the arm-leg motion-coordination problem is raised and task decomposition is proposed to solve the problem; that is, a given task described by the destination position and orientation of the end-effector is decomposed into subtasks for arm manipulation and for leg locomotion, respectively. The former is defined as the end-effector position and orientation with respect to the legged main body, and the latter as the main-body position and orientation in the world coordinates. Three approaches are proposed for the task decomposition. The approaches are further evaluated in terms of energy consumption, from which an optimal approach can be selected.

Su, Chao↗

NASA NTRS1992

In Situ Robotic Inspection Of Welds

Automated system reduces delays in inspection and rework. System reduces inspection-and-rework delay from days to hours. Path of inspection sensors taken directly from welding path saving time in programming for inspection. Inspection data stored so not lost as inspection equipment turned off. Same robot welding workpiece used to inspect it. In preparation, welding tool mounted on end effector of robot replaced with eddy-current or ultrasonic sensor. Robot recalls welding path from memory and retraces it, recording sensor output as it proceeds.

Van Wyk, Lisa M.↗

NASA NTRS1992

Hand/Eye Coordination For Fine Robotic Motion

Fine motions of robotic manipulator controlled with help of visual feedback by new method reducing position errors by order of magnitude. Robotic vision subsystem includes five cameras: three stationary ones providing wide-angle views of workspace and two mounted on wrist of auxiliary robot arm. Stereoscopic cameras on arm give close-up views of object and end effector. Cameras measure errors between commanded and actual positions and/or provide data for mapping between visual and manipulator-joint-angle coordinates.

Lokshin, Anatole M.↗

NASA NTRS1992

Analyzing Robotic Kinematics Via Computed Simulations

Computing system assists in evaluation of kinematics of conceptual robot. Displays positions and motions of robotic manipulator within work cell. Also displays interactions between robotic manipulator and other objects. Results of simulation displayed on graphical computer workstation. System includes both off-the-shelf software originally developed for automotive industry and specially developed software. Simulation system also used to design human-equivalent hand, to model optical train in infrared system, and to develop graphical interface for teleoperator simulation system.

Carnahan, Timothy M.↗

NASA NTRS1991

Composite video and graphics display for multiple camera viewing system in robotics and teleoperation

A system for real-time video image display for robotics or remote-vehicle teleoperation is described that has at least one robot arm or remotely operated vehicle controlled by an operator through hand-controllers, and one or more television cameras and optional lighting element. The system has at least one television monitor for display of a television image from a selected camera and the ability to select one of the cameras for image display. Graphics are generated with icons of cameras and lighting elements for display surrounding the television image to provide the operator information on: the location and orientation of each camera and lighting element; the region of illumination of each lighting element; the viewed region and range of focus of each camera; which camera is currently selected for image display for each monitor; and when the controller coordinate for said robot arms or remotely operated vehicles have been transformed to correspond to coordinates of a selected or nonselected camera.

Diner, Daniel B.↗

NASA NTRS1991

RoMPS concept review automatic control of space robot, volume 2

Topics related to robot operated materials processing in space (RoMPS) are presented in view graph form and include: (1) system concept; (2) Hitchhiker Interface Requirements; (3) robot axis control concepts; (4) Autonomous Experiment Management System; (5) Zymate Robot Controller; (6) Southwest SC-4 Computer; (7) oven control housekeeping data; and (8) power distribution.

Dobbs, M. E.↗

NASA NTRS1991

The walking robot project

A walking robot was designed, analyzed, and tested as an intelligent, mobile, and a terrain adaptive system. The robot's design was an application of existing technologies. The design of the six legs modified and combines well understood mechanisms and was optimized for performance, flexibility, and simplicity. The body design incorporated two tripods for walking stability and ease of turning. The electrical hardware design used modularity and distributed processing to drive the motors. The software design used feedback to coordinate the system and simple keystrokes to give commands. The walking machine can be easily adapted to hostile environments such as high radiation zones and alien terrain. The primary goal of the leg design was to create a leg capable of supporting a robot's body and electrical hardware while walking or performing desired tasks, namely those required for planetary exploration. The leg designers intent was to study the maximum amount of flexibility and maneuverability achievable by the simplest and lightest leg design. The main constraints for the leg design were leg kinematics, ease of assembly, degrees of freedom, number of motors, overall size, and weight.

Williams, P.↗

NASA NTRS1992

Robust tuning of robot control systems

The computed torque control problem is examined for a robot arm with flexible, geared, joint drive systems which are typical in many industrial robots. The standard computed torque algorithm is not directly applicable to this class of manipulators because of the dynamics introduced by the joint drive system. The proposed approach to computed torque control combines a computed torque algorithm with torque controller at each joint. Three such control schemes are proposed. The first scheme uses the joint torque control system currently implemented on the robot arm and a novel form of the computed torque algorithm. The other two use the standard computed torque algorithm and a novel model following torque control system based on model following techniques. Standard tasks and performance indices are used to evaluate the performance of the controllers. Both numerical simulations and experiments are used in evaluation. The study shows that all three proposed systems lead to improved tracking performance over a conventional PD controller.

Minis, I.↗

NASA NTRS1991

High Reliability Robot Friendly ORU Interface

Presented here is a robot friendly coupling device for an orbital replacement unit (ORU). The invention will provide a coupling that is detached and attached remotely by a robot. The design of the coupling must allow for slight misalignments, over-torque protection, and precision placement. This is accomplished by means of a triangular interface comprising three components. A base plate assembly is located on an attachment surface, such as a satellite. The base plate assembly has a cup member, a slotted member, and a post member. The ORU that the robot attaches to the base plate assembly has an ORU plate assembly with two cone members and a post member which mate to the base plate assembly. As the two plates approach one another, one cone member of the ORU plate assembly has to be placed accurately enough to fall into the cup member of the base plate assembly. The cup member forces alignment until a second cone falls into a slotted member which provides final alignment. A single bolt is used to attach the two plates. Two deflecting plates are attached to the backs of the plates. When pressure is applied to the center of the deflecting plates, the force is distributed preventing the ORU and base plates from deflecting. This accounts for precision in the placement of the article. The novelty is believed to reside in using deflecting plates in conjunction with kinematic mounts to provide distributed forces to the two members.

Voellmer, George M.↗

NASA NTRS1992

Development of a truss joint for robotic assembly of space structures

This report presents the results of a detailed study of mechanical fasteners which were designed to facilitate robotic assembly of structures. Design requirements for robotic structural assembly were developed, taking into account structural properties and overall system design, and four candidate fasteners were designed to meet them. These fasteners were built and evaluated in the laboratory, and the Hammer-Head joint was chosen as superior overall. It had a high reliability of fastening under misalignments of 2.54 mm (0.1 in) and 3 deg, the highest end fixity (2.18), the simplest end effector, an integral capture guide, good visual verification, and the lightest weight (782 g, 1.72 lb). The study found that a good design should incorporate chamfers sliding on chamfers, cylinders sliding on chamfers, and hard surface finishes on sliding surfaces. The study also comments on robot flexibility, sag, hysteresis, thermal expansion, and friction which were observed during the testing.

Parma, George F.↗

NASA NTRS1992

Robust adaptive kinematic control of redundant robots

The paper presents a general method for the resolution of redundancy that combines the Jacobian pseudoinverse and augmentation approaches. A direct adaptive control scheme is developed to generate joint angle trajectories for achieving desired end-effector motion as well as additional user defined tasks. The scheme ensures arbitrarily small errors between the desired and the actual motion of the manipulator. Explicit bounds on the errors are established that are directly related to the mismatch between actual and estimated pseudoinverse Jacobian matrix, motion velocity and the controller gain. It is shown that the scheme is tolerant of the mismatch and consequently only infrequent pseudoinverse computations are needed during a typical robot motion. As a result, the scheme is computationally fast, and can be implemented for real-time control of redundant robots. A method is incorporated to cope with the robot singularities allowing the manipulator to get very close or even pass through a singularity while maintaining a good tracking performance and acceptable joint velocities. Computer simulations and experimental results are provided in support of the theoretical developments.

Tarokh, M.↗

NASA NTRS1991

Human exploration and settlement of Mars - The roles of humans and robots

The scientific objectives and strategies for human settlement on Mars are examined in the context of the Space Exploration Initiative (SEI). An integrated strategy for humans and robots in the exploration and settlement of Mars is examined. Such an effort would feature robotic, telerobotic, and human-supervised robotic phases.

Duke, Michael B.↗

NASA NTRS1991

Status of robotic mission studies for the Space Exploration Initiative - 1991

Results of studies of robotic missions to the moon and Mars planned under the U.S. Space Exploration Initiative are summarized. First, an overall strategy for small robotic missions to accomplish the information gathering required by human missions is reviewed, and the principal robotic mission requirements are discussed. The discussion covers the following studies: the Lunar Observer, the Mars Environmental Survey mission, Mars Sample Return missions using microtechnology, and payloads.

Bourke, Roger D.↗

NASA NTRS1990

Experiments in teleoperator and autonomous control of space robotic vehicles

A research program and strategy are described which include fundamental teleoperation issues and autonomous-control issues of sensing and navigation for satellite robots. The program consists of developing interfaces for visual operation and studying the consequences of interface designs as well as developing navigation and control technologies based on visual interaction. A space-robot-vehicle simulator is under development for use in virtual-environment teleoperation experiments and neutral-buoyancy investigations. These technologies can be utilized in a study of visual interfaces to address tradeoffs between head-tracking and manual remote cameras, panel-mounted and helmet-mounted displays, and stereoscopic and monoscopic display systems. The present program can provide significant data for the development of control experiments for autonomously controlled satellite robots.

Alexander, Harold L.↗

NASA NTRS1991

Adaptive Cartesian coordinate control of space based robot manipulators

A Cartesian coordinate robot controller is presented for use when the mass properties of a load are unknown. The mass, center of mass, and moments of inertia of the end-effector are assumed unknown. All other inertial properties of the robot are assumed known. This knowledge of the parameters allows the control of the end-effector in a way similar to the use of reaction wheels to control the orientation of a satellite. This is the primary result of the controller. The basic method of the controller is similar to that used for terrestrial-based robot manipulators. The controller is demonstrated using a new simulation algorithm which is based on Hamilton's form of the equations of motion.

Walker, Michael W.↗

NASA NTRS1992

Control of robot dynamics using acceleration control

Acceleration control of robotic devices can provide improvements to many space-based operations using flexible manipulators and to ground-based operations requiring better precision and efficiency than current industrial robots can provide. This paper reports on a preliminary study of acceleration measurement on robotic motion during parabolic flights on the NASA KC-135 and a parallel study of accelerations with and without gravity arising from computer simulated motions using TREETOPS software.

Workman, G. L.↗