Issues, concerns, and initial implementation results for space based telerobotic control

Telerobotic control for space based assembly and servicing tasks presents many problems in system design. Traditional force reflection teleoperation schemes are not well suited to this application, and the approaches to compliance control via computer algorithms have yet to see significant testing and comparison. These observations are discussed in detail, as well as the concerns they raise for imminent design and testing of space robotic systems. As an example of the detailed technical work yet to be done before such systems can be specified, a particular approach to providing manipulator compliance is examined experimentally and through modeling and analysis. This yields some initial insight into the limitations and design trade-offs for this class of manipulator control schemes. Implications of this investigation for space based telerobots are discussed in detail

Modelado de sensores piezoresistivos y uso de una interfaz basada en guantes de datos para el control de impedancia de manipuladores robóticos

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Departamento de Arquitectura de Computadores y Automática, leída el 21-02-2014Sección Deptal. de Arquitectura de Computadores y Automática (Físicas)Fac. de Ciencias FísicasTRUEunpu

Implementation of robotic force control with position accommodation

As the need for robotic manipulation in fields such as manufacturing and telerobotics increases, so does the need for effective methods of controlling the interaction forces between the manipulators and their environment. Position Accommodation (PA) is a form of robotic force control where the nominal path of the manipulator is modified in response to forces and torques sensed at the tool-tip of the manipulator. The response is tailored such that the manipulator emulates a mechanical impedance to its environment. PA falls under the category of position-based robotic force control, and may be viewed as a form of Impedance Control. The practical implementations are explored of PA into an 18 degree-of-freedom robotic testbed consisting of two PUMA 560 arms mounted on two 3 DOF positioning platforms. Single and dual-arm architectures for PA are presented along with some experimental results. Characteristics of position-based force control are discussed, along with some of the limitations of PA

Space flight manipulator technologies and requirements for the NASA Flight Telerobotic Servicer (FTS)

NASA Headquarters' Office of Advanced Concepts and Technology (OACT) joined efforts with Johnson Space Center's (JSC) Automation and Robotics Division and Langley Research Center's (LaRC) Information Systems Division to capture the technologies developed during the cancelled NASA Flight Telerobotic Servicer (FTS) program planned for use on Space Station Freedom. The recent FTS technology capture effort completed the build and testing of one flight qualifiable FTS manipulator, deliverable to JSC's Automation & Robotics Division for environmental testing. The many robotic technologies developed to meet the 30 year space environment design requirements are discussed in this paper. The manipulator properties were to allow positioning control to one thousandths of an inch, with zero actuator backlash over a temperature range of -50 to +95 C, and were to include impedance control and inertial decoupling. Safety and reliability requirements are discussed that were developed to allow a thirty year life in space with minimum maintenance. The system had to meet the safety requirements for hazardous payloads for operation in the shuttle payload bay during demonstration test flights prior to station use. A brief description is contained on an orbiter based robotic experiment and operational application using the dexterous FTS manipulator operating on the end of the shuttle remote manipulator systems (SRMS) from ground control

Computer-Aided Bilateral Teleoperation of Manipulators

Haptic bilateral teleoperation is often a challenging and mentally demanding job for the operators of robot control systems. It is especially difficult in cases such as the remote maintenance of the ITER divertor region. The difficulty of the ITER divertor maintenance hails from a multitude of reasons: the residual radiation level of the ITER reactor during a shutdown is too high for any human access, the maintenance tunnels of the divertor are confined, the operators have to operate heavy loads in delicate tasks, and only a limited number of radiation tolerant cameras are available for providing video feedback. In addition, most of the maintenance work cannot be automated because of the dynamic nature and complexity of the tasks. Haptic shared control systems can be used for reducing the amount of mental and physical workload perceived by the operators of remote maintenance systems. To reduce the workload, a haptic shared control system assists the operators by generating virtual forces based on the virtual models of the teleoperation environment and sensor data from the slave manipulator. The generated assistance forces are laid over the force feedback signals from the teleoperation environment. The assisting forces can e.g. guide the operators along optimal paths and prevent collisions in the teleoperation environment. In addition to the reduction of the operator workload, teleoperation tasks also become faster and safer with haptic shared control. This thesis investigates the implementation techniques and theory of haptic bilateral teleoperation and shared control systems. Based on the theoretical analysis, an experimental haptic shared control system, called the Computer Assisted Teleoperation (CAT) was developed. The intention of CAT is to assist the remote handling (RH) system operators of the Divertor Test Platform 2 (DTP2) in ITER remote maintenance research. The effectiveness of CAT is evaluated in a teleoperation experiment performed with a 6 DOF Water Hydraulic MANipulator (WHMAN) developed for the ITER divertor maintenance. The results of the experiment gives directive indication that the CAT system improves the execution times of a bilateral teleoperation task and simultaneously reduces the workload perceived by the operators of the system

Robot Impedance Control and Passivity Analysis with Inner Torque and Velocity Feedback Loops

Impedance control is a well-established technique to control interaction forces in robotics. However, real implementations of impedance control with an inner loop may suffer from several limitations. Although common practice in designing nested control systems is to maximize the bandwidth of the inner loop to improve tracking performance, it may not be the most suitable approach when a certain range of impedance parameters has to be rendered. In particular, it turns out that the viable range of stable stiffness and damping values can be strongly affected by the bandwidth of the inner control loops (e.g. a torque loop) as well as by the filtering and sampling frequency. This paper provides an extensive analysis on how these aspects influence the stability region of impedance parameters as well as the passivity of the system. This will be supported by both simulations and experimental data. Moreover, a methodology for designing joint impedance controllers based on an inner torque loop and a positive velocity feedback loop will be presented. The goal of the velocity feedback is to increase (given the constraints to preserve stability) the bandwidth of the torque loop without the need of a complex controller.Comment: 14 pages in Control Theory and Technology (2016