Force-reflecting Hand Controller Research Articles

Design and Prototyping of a Force-Reflecting Hand-Controller for Ultrasound Imaging

This paper presents detailed design, analysis, prototyping, and testing of a novel force-reflecting hand-controller allowing physicians to control a robotic wrist and perform ultrasound examinations on patients in remote locations. The proposed device is a four degree-of-freedom mechanism with a fixed center-of-motion and uses symmetric parallel mechanisms. All movements of the device are kinematically decoupled, i.e., the hand-controller has independent drive systems for each standard ultrasound motion. A technique has been adapted to statically balance the weight of the device over its entire workspace using a single tension spring. The prototype of the device has been constructed and evaluated for ultrasound imaging of kidney and spleen. Maximum and accuracy of the output force are analytically determined and performance of the device in terms of static balancing, static-friction break-away force, and maximum achievable impedances are experimentally evaluated.

Force reflection for ground control of Space robots

Ideas for improving continuous teleoperation and operator performance despite time delays using force-reflecting hand controllers. They have been tested on the Japanese Engineering Test Satellite-7 (ETS-7). Predictive display and predictive simulation are used.

Control of Kinesthetic Haptic Interfaces in VR Applications

Cartesian control algorithms are presented for six degree of freedom (6-DOF) force-reflecting hand-controllers (FRHCs) used for simultaneous operator position/orientation (or rate) commands to a virtual reality (VR) system and virtual force/moment kinesthetic reflection to the operator. The commands and kinesthetic feedback are transferred in Cartesian space. The task force/moment (wrench) dominates while features are provided to reduce operator loading: virtual payload and FRHC gravity compensation, input channels to easily separate 6-DOF inputs with one hand, constant-force return-to-center, and FRHC damping to improve relative stability. In experimental implementation, the "VR system" was a real remotely located teleoperated robotic system with real sensed task wrenches. Experimental results show that the algorithms are effective for reduced contact wrenches and increased telepresence quality in practical tasks. The methods in this paper are suitable for kinesthetic haptic display in virtual environments.

Applications of intelligent telerobotic control

The telerobotics laboratory at Lawrence Livermore National Laboratory is a facility for developing and testing new concepts in robotics controls. Research and development is being conducted in computer vision; adaptive control; software architectures for real-time, intelligent control; artificial neural networks; fuzzy logic controllers; telepresence; and path planning and collision avoidance. The equipment in the telerobotics laboratory includes a six degree of freedom articulating robot arm with controller, gripper and force and torque sensor, a 3D CAD workstation with software to model the work cell environment and simulate the robot dynamics; a six degree of freedom forceball for operator input to the telerobotics controller and the robot simulation; and a computer with a real-time operating system. Soon to be added are a 3D viewing system and a force reflecting hand controller. This paper describes one of the research and development efforts currently in progress on this program.

Performance evaluation of a six-axis generalized force-reflecting teleoperator

Recent work in real-time distributed computation and control has culminated in a prototype force-reflecting telemanipulation system having dissimilar master (cable-driven force-reflecting hand controller) and slave (PUMA 560 robot with custom controller), extremely high sampling rate (1000 Hz), and low loop computation delay (5 ms). In a series of experiments with this system and five trained test operators covering more than 100 h of teleoperation, performance in a series of generic and application-driven tasks with and without force feedback was measured, and with control shared between teleoperation and local sensor referenced control. Measurements defining task performance include 100-Hz recording of six-axis force-torque information, task completion time, and visual observation of predefined task errors. It is shown that all performance measures improved as capability was added along a spectrum of capabilities ranging from pure position control through force-reflecting teleoperation and shared control. Performance was maximal for the barehanded operator.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Flight Telerobotic Servicer: Teleoperations in Microgravity

The Flight Telerobotic Servicer (FTS) is a dual-arm robot which will perform operations in space through manual teleoperation or autonomous control. The FTS is being designed and built by Martin Marietta Astronautics Group for NASA and will be used for aiding astronauts in assembling, servicing, maintaining, and inspecting Space Station Freedom (SSF). Robots will be an important part of SSF operations in order to limit hazardous astronaut EVA time. Some typical tasks the FTS is being designed to perform include installation/removal of structural truss elements, changeout of modular electronics packages, mate/demate of connectors, and performance of inspection tasks. FTS control stations will be located on board both the Shuttle and SSF. These workstations consist of controls/displays, video from telerobot cameras, force reflecting hand controllers, and operator restraints. Special problems which have been encountered by the ongoing human factors effort include the design of a restraint system to accommodate 5th to 95th percentile astronauts, maximizing hand controller operational envelopes in limited space, noncongruent operator, display, and teleoperation coordinate systems, and design of a human-computer interface which minimizes the amount of time the operator must release hand controllers to perform other workstation functions. Test flights for FTS have been planned for 1991 and 1993 and will allow evaluation of such issues as the biomechanics of a restrained operator using force reflecting hand controllers in microgravity, assessing effects on operator performance of various control modes, use of different translational, rotational, and force reflection gains, degrees of shared control (active compliance), and operator fatigue.

Bilateral control of teleoperators with time delay

A control law for teleoperators is presented which overcomes the instability caused by time delay. By using passivity and scattering theory, a criterion is developed which shows why existing bilateral control systems are unstable for certain environments, and why the proposed bilateral control law is stable for any environment and any time delay. The control law has been implemented on a single-axis force-reflecting hand controller, and preliminary results are shown. To keep the presentation clear, a single-degree-of-freedom (DOF) linear time-invariant (LTI) teleoperator system is discussed. Nevertheless, results can be extended, without loss of generality, to an n-DOF nonlinear teleoperation system. >

Human Operator Control of a Bilateral Teleoperator in Part-Simulation of Zero Gravity

An experimental investigation has been undertaken at the Jet Propulsion Laboratory to address issues associated with manual control of a teleoperated manipulator operated in an earth orbital environment (e.g., the Shuttle Remote Manipulator System (RMS)). Manual control of a teleoperator and the effect of microgravity on the operator's performance were examined using a force-reflecting hand controller (FRHC) and a gravity compensation system to simulate the effect of microgravity on the operator's arm. The kinematic and dynamic characteristics of the operator's arm and hand play a fundamental role in bilateral (backdriven) teleoperator control. Two control experiments were performed in this study: (a) verification of a linear damped harmonic oscillator model of human neuromotor control in trajectory formation and stability in standard one gravity (lg) operation, and (b) force tracking along simulated planes of resistance subject to unit pulse disturbance in simulated zero g operation. The results of the experiments verified the utility of the neuromotor model in teleoperator control performance and confirmed the existence of disturbance of human manual control performance associated with the micro-gravity condition. The results illustrate that compensatory techniques to return performance to a level commensurate with, or superior to, standard one gravity operation could be derived. These techniques are based on the human control model, and instituted through FRHC control parameter adjustment.