Contact Operations Using an Instrumented Compliant Wrist

Teleprogramming was developed as a solution to problems of teleoperation systems with significant time delays [5]. In teleprogramming, the human operator interacts in real time with a graphical model of the remote site, which provides for real time visual and force feedback. The master system automatically generates symbolic commands based on the motions of the master arm and the manipulator/model interactions, given predefined criteria of what types of motions are to be expected. These commands are then sent via a communication link, which may delay the signals, to the remote site. Based upon a remote world model, predefined and possibly refined as more information is obtained, the slave carries out commanded operations in the remote world and decides whether each step has been executed correctly. Contact operations involve the remote site manipulator interacting with the environment, including planned collisions, and motion with contact with the environment. A hybrid position/force control scheme using a instrumented compliant wrist has been demonstrated to be very effective for these types of operations. In particular, switching between position and force modes (when contacting a surface, for example) does not present problems for the system. A brief introduction of teleprogramming and contact operations is presented, including a model of sliding motions and early experimental results. Problems with these early experiments are presented, and solutions discussed. The criteria for an object to slide rather than tip over are presented, relating to the geometry of the object and the applied forces. Finally, methods are presented to match the experimental results to a simple model, to help the remote manipulator to quickly and robustly sense collisions

Teleprogramming: Remote Site Research Issues: (Dissertation Proposal)

This document proposes the development of the remote site workcell for teleoperation with significant communication delays (on the order of one to 20 seconds). In these situations, direct teleoperation becomes difficult to impossible due to the delays in visual and force feedback. Teleprogramming has been developed in order to overcome this problem. In teleprogramming, the human operator interacts in real time with a graphical model of the remote site, which provides for real time visual and force feedback. The master arm and the manipulator/model interactions, given predefined criteria of what types of motions are to be expected. These commands are then sent via a communication link, which may delay the signals, to the remote site. Based upon a remote world model, predefined and possibly refined as more information is obtained, the slave carries out commanded operations in the remote world and decides whether each step has been executed correctly. The remote site receives commands sent via the delayed communication link. These commands must be parsed and translated into the local robot control language, which includes insertion of dynamic parameters that are not generated by the master system. The commands are then executed by the hybrid position/force controller, and the resulting motions monitored for errors. This proposal addresses the following remote site issues: low level manipulator control using an instrumented compliant wrist for sensory feedback, higher level command execution implementing dynamic parameters, and remote manipulator tool usage and control

Model Based Teleoperation to Eliminate Feedback Delay NSF Grant BCS89-01352 - 3rd Report

We are conducting research in the area of teleoperation with feedback delay. Significant delays occur when performing space teleoperation from the earth as well as in subsea teleoperation where the operator is typically on a surface vessel and communication is via acoustic links. These delays make teleoperation extremely difficult and lead to very low operator productivity. We have combined computer graphics with manipulator programming to provide a solution to the delay problem. A teleoperator master arm is interfaced to a graphical simulation of the remote environment. Synthetic fixtures are used to guide the operators motions and to provide kinesthetic feedback. The operator\u27s actions are monitored and used to generate symbolic motion commands for transmission to, and execution by, the remote slave robot. While much of a task proceeds error free, when an error does occur, the slave system transmits data back to the master environment where the operator can then experience the motion of the slave manipulator in actual task execution. We have also provided for the use of tools such as an impact wrench and a winch at the slave site. In all cases the tools are unencumbered by sensors; the slave uses a compliant instrumented wrist to monitor tool operation in terms of resulting motions and reaction forces

Model Based Teleoperation to Eliminate Feedback Delay NSF Grant BCS89-01352 Second Report

We are conducting research in the area of teleoperation with feedback delay. Delay occurs with earth-based teleoperation in space and with surface-based teleoperation with untethered submersibles when acoustic communication links are involved. The delay in obtaining position and force feedback from remote slave arms makes teleoperation extremely difficult leading to very low productivity. We have combined computer graphics with manipulator programming to provide a solution to the problem. A teleoperator master arm is interfaced to a graphics based simulator of the remote environment. The system is then coupled with a robot manipulator at the remote, delayed site. The operator\u27s actions are monitored to provide both kinesthetic and visual feedback and to generate symbolic motion commands to the remote slave. The slave robot then executes these symbolic commands delayed in time. While much of a task proceeds error free, when an error does occur, the slave system transmits data back to the master environment which is then reset to the error state from which the operator continues the task

Wide Bandwidth, Distributed, Digital Teleoperation

Teleoperation means to perform a task at a distance. The task is performed by a manipulator located at a remote site, controlled by the master manipulator located in the control room. The loop between the master and the slave manipulator is closed by the human operator. The dexterity and manipulability of the overall system has to be high such that the actions can be easily carried out by the operator. A visual display provides the operator a view of the slave arm and the task environment, kinesthetic feedback provides a sense of physically performing the task. Kinesthetic feedback is direct feedback to the operator, while visual, audio, and other feedback are indirect in nature. The displays generated from the video data are very useful even when the quality of the image is degraded. Changes in the camera position and orientation can cause severe strain on the operator when interpreting the viewed image. The corrections are applied to the position and force transformations to reduce the strain on the operator. The position and force data are communicated over a communication channel from one station to the other. The use of communication channel basically not designed for real time processes can introduce significant delays leading to operator induced instability of the teleoperator system. In the presence of such delays the force reflection as a non-reactive feedback can help in maintaining the stability of the system. The forces encountered by the slave manipulator is transformed into audio range signals. The audio signal to the operator is a reflection of force in a non-reactive manner. Advances in high speed networks with increased bandwidth and decreased error rates provide an opportunity to implement teleoperator systems for long distance and distributed teleoperation. A single operator from a control station can interact physically with a system situated anywhere in the world and perform the tasks as though he or she was present at the remote site. A step by step implementation procedure of a direct teleoperator system with communication between master and slave stations through a computer network is described. The corrections to the transforms to nullify the effect of change in viewing parameters are discussed. The experimental results showing the effectiveness of the change in camera orientations and the comparison of active force reflection to the non-reactive force reflection in the form of auditory signal is presented

Robotic Exploration of Surfaces With a Compliant Wrist Sensor

This paper presents some results of an ongoing research project to investigate the components and modules that are necessary to equip a robot with exploratory capabilities. Of particular interest is the recovery of certain material properties from a surface, given minimal a priori information, with the intent to use this information to enable a robot to stand and walk stably on a surface that is unknown and unconstrained. To this end, exploratory procedures (ep\u27s) have been designed and implemented to recover penetrability, material hardness and surface roughness by exploring the surface using a compliant wrist sensor. A six degree-of-freedom compliant wrist sensor, which combines passive compliance and active sensing, has been developed to provide the necessary flexibility for force and contact control, as well as to provide accurate position control. This paper describes the compliant wrist and sensing mechanism design along with a hybrid control algorithm that utilizes the sensed information from the wrist to adjust the apparent stiffness of the end-effector as desired

A Robotic System for Learning Visually-Driven Grasp Planning (Dissertation Proposal)

We use findings in machine learning, developmental psychology, and neurophysiology to guide a robotic learning system\u27s level of representation both for actions and for percepts. Visually-driven grasping is chosen as the experimental task since it has general applicability and it has been extensively researched from several perspectives. An implementation of a robotic system with a gripper, compliant instrumented wrist, arm and vision is used to test these ideas. Several sensorimotor primitives (vision segmentation and manipulatory reflexes) are implemented in this system and may be thought of as the innate perceptual and motor abilities of the system. Applying empirical learning techniques to real situations brings up such important issues as observation sparsity in high-dimensional spaces, arbitrary underlying functional forms of the reinforcement distribution and robustness to noise in exemplars. The well-established technique of non-parametric projection pursuit regression (PPR) is used to accomplish reinforcement learning by searching for projections of high-dimensional data sets that capture task invariants. We also pursue the following problem: how can we use human expertise and insight into grasping to train a system to select both appropriate hand preshapes and approaches for a wide variety of objects, and then have it verify and refine its skills through trial and error. To accomplish this learning we propose a new class of Density Adaptive reinforcement learning algorithms. These algorithms use statistical tests to identify possibly interesting regions of the attribute space in which the dynamics of the task change. They automatically concentrate the building of high resolution descriptions of the reinforcement in those areas, and build low resolution representations in regions that are either not populated in the given task or are highly uniform in outcome. Additionally, the use of any learning process generally implies failures along the way. Therefore, the mechanics of the untrained robotic system must be able to tolerate mistakes during learning and not damage itself. We address this by the use of an instrumented, compliant robot wrist that controls impact forces