Antal K. Bejczy

A new telerobotic application: remote laparoscopic surgery using satellites and optical fiber networks for data exchange

This article describes the significance in human, scientific, and technical terms of the first experiment in telerobotic surgery carried out between the NASA Jet Propulsion Laboratory in Pasadena, California, and the Telerobotics Laboratory of the Politecnico di Milano on 7 July 1993. An Italian robot in the Telerobotics Laboratory was remotely controlled by an Italian surgeon in the United States. The robots task was to perform a surgical operation on a model containing a pigs organs, involving execution of a biopsy, aspi ration of organic material, and two incisions in preparation of laparoscopy. Transmission was effected by means of a double satellite link, with three transceiver stations: one in Italy, one close to New York, and one in Pasadena, and two geostation ary satellites, the first over the Atlantic and the second over the United States. The route length of the signals was 150,000 km in each direction, and the two centers are 10,000 km apart.

Effect of hand-based sensors on manipulator control performance

Abstract Manipulator task categories and motion phases require various hand-based information systems to meet the control performance requirements. The effect of proximity, tactile and force/torque sensors on the performane of remote manipulator control is discussed. An overview is presented on various experimental hand-based information systems which provide the manipulator controller some non-visual “awareness” of the task environment. The rest of the paper describes and evaluates various control experiments performed at JPL using hand-mounted proximity sensors to guide and control hand motion near solid objects.

Task definition, decoupling and redundancy resolution by nonlinear feedback in multi-robot object handling

The problem of rigid object handling by multiple robot arms is investigated. The primary goal is to make the object exhibit a prescribed behavior while in contact with a fully known environment. Point contacts are assumed between the object and the arms. The aspect of task definition to achieve decoupling and linearizing control laws is discussed. Control laws are first formulated at the object level to provide decoupled force and position servo loops. It is then used to form control laws for the individual arms. Redundancies exist at the object and arm levels. The object level redundancy is used to achieve secondary goals in object handling. The arm level redundancies are the zero dynamics and can be controlled by redundant inputs. Full use of the available inputs are used to control the system as a whole. Numerical simulations for a dual-arm situation illustrate the validity of the approach.<<ETX>>

Experimental evaluation of the nonlinear feedback robot controller

The trajectory tracking performance of the nonlinear feedback controller based on differential geometric control theory was experimentally studied. The performance is compared to three other methods: independent joint proportional-derivative (PD) control, independent joint PD control with feedforward torque computations, and the computed torque method. In the nonlinear feedback controller, servo is in the task space. In the other three methods servo is in the joint space. Path planning is in the task space. Circular and straight line paths are considered. A sampling frequency of 200 Hz is used. The effect of sampling frequency on tracking error is studied for the nonlinear feedback control scheme. The performance of these methods was tested on a PUMA 560 arm. The trajectory tracking performance of the robot arm under the nonlinear feedback controller is comparable to that of the computed torque control schemes.<<ETX>>

Advanced operator interface design with preview/predictive displays for ground-controlled space telerobotic servicing

Recent advances in real-time 3-D graphics and graphical user interface (GUI) technologies enable development of advanced operator interfaces for telerobotic systems. In particular, we have employed preview/predictive displays with calibrated graphics overlay and X/Motif- based GUIs for efficient and reliable ground-controlled space telerobotic servicing under communication time delay. High fidelity preview/predictive displays have been achieved by an operator-interactive camera calibration and object localization technique that enables reliable matching of simulated 3-D graphics models with the remote site task environment. The developed graphical operator interface supporting telerobotic operations with high-fidelity preview/predictive displays have been successfully utilized in demonstrating a ground- simulated ORU (Orbital Replacement Unit) changeout remote servicing task by remotely operating a robot arm at NASA Goddard Space Flight Center from the Jet Propulsion Laboratory under a varying time delay of up to several seconds. The positioning alignment accuracy achieved by this technique with four camera views was about +/- 5 mm for a tool insertion in the servicing task.

Telerobotics surgery in a transatlantic experiment: application in laparoscopy

This paper describes the significance in human, scientific, and technical terms of the first experiment of robotic telesurgery effected between the Telerobotics Laboratory of the Politecnico di Milano and the Jet Propulsion Laboratory, NASA, in Pasadena California, on 7 July 1993. An Italian surgeon controlled from the U.S. A. an Italian robot in the Telerobotics Laboratory in such a way that the robot performed a biopsy, on a model containing the organs of a pig, carrying out an aspiration of organic material and two incisions for the commencement of the surgical operation of laparoscopy. Transmission was effected by means of a double satellite link with three stations -- one in Italy, one in New York and one in Pasadena -- and two geostationary satellites, the first over the Atlantic and the second over the United States.

Motion space analysis of an object handled by two robot arms

The kinematic capabilities of two cooperating robot arms are studied by investigating the geometric motion space of an object handled by these two robot arms. An understanding of these capabilities is a prerequisite for the motion planning of two-arm cooperation. The motion space and the geometric motion space analysis problem are defined. These definitions are derived from those of the robot workspace analysis. The geometric constraints on the motion space are identified, and a motion space analysis procedure is developed. This procedure was applied to the case of two cooperating PUMA 560 robot arms and the motion space of a long object handled by them was computed with pregiven constraints on its orientations.<<ETX>>

Nonlinear feedback method of robot control: a preliminary experimental study

The nonlinear feedback method of robot control has been experimentally implemented on two PUMA 560 robot arms. The feasibility of the proposed controller, which is already known to be viable, is stressed. The servomechanism operates in task space, and the nonlinear feedback takes care of the necessary transformations to compute the necessary joint currents. A discussion is presented of the implementation with details of the experiments performed. The performance of the controller is encouraging but was limited to 100 Hz sampling frequency and to derived velocity information at the time of the experimentation. The setup of the lab, the software aspects, results, and the control hardware architecture that has recently been implemented are discussed.<<ETX>>

Control of robots with discrete nonlinear model: theory and experimentation

The discrete time theory that feedback linearizes and output decouples the coupled nonlinear dynamics of the PUMA 560 robot arm is systematically developed. The effect of sampling on the performance of the arm has been studied and shown through experiments. Certain restrictions that are necessary on the sampling time of the system are shown. The results obtained have been experimentally verified. Since a number of researchers have addressed the problem of loss of feedback linearizability under sampling, it was important to develop theories and obtain results in discrete time that take into consideration the effects due to sampling. This problem is addressed.<<ETX>>

Control of robot manipulators for handling and assembly in space

Abstract Long-range NASA planning includes construction and erection of large systems in space requiring automatic handling equipment, teleoperators, or robots under supervisory control. This paper investigates and explores some of the requirements for the control of teleoperated and autonomous space manipulators. The critical technology development areas are identified and discussed in the context of the developments at the Jet Propulsion Laboratory (JPL), and other places.