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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

An 8-DOF dual-arm system for advanced teleoperation performance experiments

This paper describes the electro-mechanical and control features of an 8-DOF manipulator manufactured by AAI Corporation and installed at the Jet Propulsion Lab. (JPL) in a dual-arm setting. The 8-DOF arm incorporates a variety of features not found in other lab or industrial manipulators. Some of the unique features are: 8-DOF revolute configuration with no lateral offsets at joint axes; 1 to 5 payload to weight ratio with 20 kg (44 lb) payload at a 1.75 m (68.5 in.) reach; joint position measurement with dual relative encoders and potentiometer; infinite roll of joint 8 with electrical and fiber optic slip rings; internal fiber optic link of 'smart' end effectors; four-axis wrist; graphite epoxy links; high link and joint stiffness; use of an upgraded JPL Universal Motor Controller (UMC) capable of driving up to 16 joints. The 8-DOF arm is equipped with a 'smart' end effector which incorporates a 6-DOF forcemoment sensor at the end effector base and grasp force sensors at the base of the parallel jaws. The 8-DOF arm is interfaced to a 6 DOF force reflecting hand controller. The same system is duplicated for and installed at NASA-Langley.

Bejczy, Antal K.↗
DOE OSTI2024

Modular DC circuit breaker with integrated energy storage for future DC networks

A T-breaker is an all-in-one solution for dc microgrid fault protection, power flow control, and power quality improvement. A T-breaker features a modular multilevel “T” structure with integrated energy storage devices. The two horizontal arms of the T-breaker realize fault current breaking, load voltage compensation, and power flow control; and the vertical arm of the T-breaker realizes shunt compensation. The configuration provides excellent voltage scalability and relaxes the requirements on the switching signal synchronization during fault transients. The local energy storage in sub-modules eases the fault energy dissipation requirement placed on the traditionally-adopted surge arrestors. The modular multilevel structure also offers immense control flexibility for all types of targeted functions of the provided T-breaker.

Wang, Jin↗
NASA NTRS1995

Human-like Compliance for Dexterous Robot Hands

This paper describes the Active Electromechanical Compliance (AEC) system that was developed for the Jau-JPL anthropomorphic robot. The AEC system imitates the functionality of the human muscle's secondary function, which is to control the joint's stiffness: AEC is implemented through servo controlling the joint drive train's stiffness. The control strategy, controlling compliant joints in teleoperation, is described. It enables automatic hybrid position and force control through utilizing sensory feedback from joint and compliance sensors. This compliant control strategy is adaptable for autonomous robot control as well. Active compliance enables dual arm manipulations, human-like soft grasping by the robot hand, and opens the way to many new robotics applications.

Compliant Control↗
NASA NTRS1993

Space Station/Orbiter berthing dynamics during an assembly flight

A large-angle, multi-body, dynamic modeling capability was developed to help validate numerical simulations of the dynamic motion and control forces which occur while berthing Space Station Freedom to the Shuttle Orbiter during early assembly flights. The paper describes the dynamics and control of the station, the attached Shuttle Remote Manipulator System, and the Orbiter during a maneuver from a gravity-gradient attitude to a torque equilibrium attitude using the station reaction control jets. The influence of the elastic behavior of the station and of the remote manipulator system on the attitude control of the station/Orbiter system during the maneuver is investigated. The flexibility of the station and the arm had only a minor influence on the attitude control of the system during the maneuver.

Cooper, Paul A.↗
NASA NTRS1989

Impedance hand controllers for increasing efficiency in teleoperations

An impedance hand controller with direct force feedback is examined as an alternative to bilateral force reflection in teleoperations involving force contact. Experimentation revealed an operator preference for direct force feedback which provided a better feel of contact with the environment. The advantages of variable arm impedance were also made clear in tracking tests where subjects preferred the larger hand controller inertias made possible by the acceleration feedback loop in the master arm. The ability to decouple the hand controller impedance from the slave arm dynamics is expected to be even more significant when the inertial properties of various payloads in the slave arm are considered.

Carignan, Craig↗
NASA NTRS1989

Impedance hand controllers for increasing efficiency in teleoperations

An impedance hand controller with direct force feedback is examined as an alternative to bilateral force reflection in teleoperations involving force contact. Experimentation revealed an operator preference for direct force feedback which provided a better feel of contact with the environment. The advantages of variable arm impedance were also made clear in tracking tests where subjects preferred the larger hand controller inertias made possible by the acceleration feedback loop in the master arm. The ability to decouple the hand controller impedance from the slave arm dynamics is expected to be even more significant when the inertial properties of various payloads in the slave arm are considered.

Carignan, C.↗
NASA NTRS1989

Configuration control of redundant manipulators - Theory and implementation

A simple approach for controlling the manipulator configuration over the entire motion is presented, based on augmentation of the manipulator forward kinematics. User-defined kinematic functions and the end-effector Cartesian coordinates are combined to form a set of task-related configuration variables as generalized coordinates for the manipulator. A task-based adaptive scheme is then utilized to control the configuration variables and achieve tracking of the desired reference trajectories. This achieves the desired end-effector motion while utilizing redundancy to achieve any additional task. Simulation results for a direct-drive two-link arm are given to illustrate the proposed control scheme. The scheme has also been implemented for real-time control of three links of a PUMA 560 industrial robot. The simulation and experimental results validate the configuration control scheme and demonstrate its capabilities for performing various realistic tasks.

Seraji, Homayoun↗
NASA NTRS2002

Thermal Nondestructive Evaluation Report: Inspection of the Refurbished Manipulator Arm System in the Manipulator Development Facility at Johnson Space Center 10-12 January 2001

On 4 December 2002, a failure of the Refurbished Manipulator Arm System (RMAS) occurred in the Manipulator Development Facility (MDF) at Johnson Space Center. When the Test Director commanded a should pitch maneuver to lift the arm from its payload bay pedestal, the yaw controls failed. This, coupled with a gravitational forces (due to the angle of the shoulder joint with respect to vertical), resulted in uncontrolled arm motion. The shoulder yaw joint moved approximately 20 degrees, causing the extended arm to strike and severely damage the port side MDF catwalk handrails. The arm motion stopped after impact with the handrails. On 10-12 January 2001, inspections were performed on the port face of the lower and upper arms of the RMAS using a infrared thermography developed at Langley Research Center. This paper presents the results of those nondestructive inspections and provides a complete description of the anomalies found and their locations.

Cramer, K. Elliott↗
NASA NTRS1995

Unified Approach To Control Of Motions Of Mobile Robots

Improved computationally efficient scheme developed for on-line coordinated control of both manipulation and mobility of robots that include manipulator arms mounted on mobile bases. Present scheme similar to one described in "Coordinated Control of Mobile Robotic Manipulators" (NPO-19109). Both schemes based on configuration-control formalism. Present one incorporates explicit distinction between holonomic and nonholonomic constraints. Several other prior articles in NASA Tech Briefs discussed aspects of configuration-control formalism. These include "Increasing the Dexterity of Redundant Robots" (NPO-17801), "Redundant Robot Can Avoid Obstacles" (NPO-17852), "Configuration-Control Scheme Copes with Singularities" (NPO-18556), "More Uses for Configuration Control of Robots" (NPO-18607/NPO-18608).

Seraji, Homayoun↗
NASA NTRS1977

Control of free-flying space robot manipulator systems

To accelerate the development of multi-armed, free-flying satellite manipulators, a fixed-base cooperative manipulation facility is being developed. The work performed on multiple arm cooperation on a free-flying robot is summarized. Research is also summarized on global navigation and control of free-flying space robots. The Locomotion Enhancement via Arm Pushoff (LEAP) approach is described and progress to date is presented.

Cannon, Robert H., Jr.↗
NASA NTRS1976

Shuttle remote manipulator system workstation - Man-machine engineering

A major subsystem aboard the Shuttle Orbiter, the Remote Manipulator System (RMS) provides the capability to deploy and retrieve free-flying satellites, support attached payload operations, and aid in crewmember rescue from a disabled vehicle should the requirement arise. The Remote Manipulator System consists of 15.3-m (50 ft) articulated booms, end effectors, operator workstation, and closed circuit video, power and control subsystems. The manipulator booms (or arms) and end effectors are located in the Orbiter payload bay and operated from inside the cabin by one crewmember. This paper is primarily concerned with the design and development of the RMS operator's workstation, the man-machine engineering features and interfaces, and man-in-the-loop simulations and testing results obtained to date by the National Aeronautics and Space Administration (NASA).

Brown, J. W.↗
NASA NTRS1980

Design of a modular digital computer system

A Central Control Element (CCE) module which controls the Automatically Reconfigurable Modular System (ARMS) and allows both redundant processing and multi-computing in the same computer with real time mode switching, is discussed. The same hardware is used for either reliability enhancement, speed enhancement, or for a combination of both.

Source record↗
NASA NTRS1980

The direct observation of unidirectional solidification as a function of gravity level

A saturated solution of NH4 Cl-H2O was solidified unidirectionally on earth at 1 g and in a suborbital rocket at 0.001 g. In the 1 g experiment, extensive fluid flow was apparent, creating plumes which carry numerous crystallites vertically above the interface in a manner associated with freckling in castings. During growth the interface grew into the liquid at the same rate as the individual dendrites. When solidified in low g, the interface grew at a slower rate than the individual dendrites. No plumes of liquid carrying crystals were seen, but several crystals did appear and grow ahead of the interface. Growth rates, dendrite morphologies and preferred crystallographic orientations are compared for the two experiment conditions. Results indicate that solidification in low gravity produces more uniform dendrite arm spacings, and tends to be controlled by diffusion and crystallographic orientation.

Johnston, M. H.↗
NASA NTRS1987

High speed precision motion strategies for lightweight structures

Work during the recording period proceeded along the lines of the proposal, i.e., three aspects of high speed motion planning and control of flexible structures were explored: fine motion control, gross motion planning and control, and automation using light weight arms. In addition, modeling the large manipulator arm to be used in experiments and theory has lead to some contributions in that area. These aspects are reported below. Conference, workshop and journal submissions, and presentations related to this work were seven in number, and are listed. Copies of written papers and abstracts are included.

Book, Wayne J.↗
NASA NTRS1986

System architecture for the telerobotic work system

The functional and performance requirements and design concepts for a telerobotic work system (TWS) being considered as an adjunct to the Shuttle Remote Manipulator System and other applications are described. The multiple-armed free-flyer would be controlled by an operator in the Orbiter cabin and would perform remote sensing and manipulative tasks that EVA crew otherwise carry out. The TWS could also perform hazardous tasks, construction operations, and be an asset to the Space Station. Alternative system architectures are described, including the man-machine interface, the types of manipulators and their stowage, and the controls and backup systems. Potential terrestrial applications of the TWS concept, augmented with AI capabilities, are discussed.

Jenkins, Lyle M.↗
NASA NTRS1988

Robot trajectory tracking with self-tuning predicted control

A controller that combines self-tuning prediction and control is proposed for robot trajectory tracking. The controller has two feedback loops: one is used to minimize the prediction error, and the other is designed to make the system output track the set point input. Because the velocity and position along the desired trajectory are given and the future output of the system is predictable, a feedforward loop can be designed for robot trajectory tracking with self-tuning predicted control (STPC). Parameters are estimated online to account for the model uncertainty and the time-varying property of the system. The authors describe the principle of STPC, analyze the system performance, and discuss the simplification of the robot dynamic equations. To demonstrate its utility and power, the controller is simulated for a Stanford arm.

Cui, Xianzhong↗