Transputers at Work: Real-Time Distributed Robot Control

An advanced robot control system joining a GMF A-500 industrial arm with a network of Inmos Transputers is described in the context of the developing field of robotics. The robot system is used to experimentally compare conventional linear control algorithm performance with both the advanced “computer torque” inverse dynamics control algorithm and a recently developed “adaptive computed torque” algorithm

Robot control in a message passing environment: theoretical questions and preliminary experiments

The performance of real-time distributed control systems is shown to depend critically on both communication and computation costs. A taxonomy for distributed system performance measurement is introduced. A roughly accurate method of performance prediction for simple systems is presented. Experimental results demonstrate the effects of communication protocols on real-world system performance

Automatic assembly planning and control via potential functions

An approach to the problem of automated assembly planning and control using artificial potential functions is described. A simple class of tasks, 2D sphere assemblies, is examined. A constructive theory for the planning and control of this class of tasks is presented. Computer simulations demonstrate that the approach may provide surprisingly good performance

Preliminary Experiments in Real Time Distributed Robot Control

We investigate the computational needs of advanced real-time robot control. First, sampling rate issues in the control of nonlinear systems are discussed. Second, a representative nonlinear robot control algorithm using an explicit robot dynamical model is derived. Some typical terms of the exact equations are given for two industrial robot arms. Third, we define some performance criteria of interest in realtime control. Finally, we compare a variety of implementations of the above control algorithm on a network of INMOS Transputers

Preliminary Experiments in Robot Juggling: Transputer Based Real-Time Motion Control

In a continuing program of research in robotic control of intermittent dynamical tasks, we have constructed a three degree of freedom robot capable of “juggling” a ball freely in the earth’s gravitational field. This work is a direct extension of that previously reported in [5, 1, 4, 3, 2, 7]. The system consists of four major sections, all of which have been implemented on a network of twelve transputers

Comparative Experiments with a New Adaptive Controller for Robot Arms

This paper presents a new model-based adaptive controller and proof of its global asymptotic stability with respect to the standard rigid-body model of robot-arm dynamics. Experimental data from a study of one new and several established globally asymptotically stable adaptive controllers on two very different robot arms 1) demonstrate the superior tracking performance afforded by the model-based algorithms over conventional PD control, 2) demonstrate and compare the superior performance of adaptive model-based algorithms over their nonadaptive counterparts, 3) reconcile several previous contrasting empirical studies, and 4) examine contexts that compromise their advantage

Comparative experiments with a new adaptive controller for robot arms

This paper presents a new adaptive controller and proof of its global asymptotic stability with respect to the standard rigid body model of robot arm dynamics. Experimental data from a study of this and other globally asymptotically stable adaptive controllers on two very different robot arms (i) reconciles several previous contrasting empirical studies (ii) demonstrates and compares their superior tracking performance (iii) examines contexts which com promise their advantage

Advances in Decentralized Single-Beacon Acoustic Navigation for Underwater Vehicles: Theory and Simulation

This paper reports the theory and implementation of a decentralized navigation system that enables simultaneous single-beacon navigation of multiple underwater vehicles. In single-beacon navigation, each vehicle uses ranges from a single, moving reference beacon in addition to its own inertial navigation sensors to perform absolute localization and navigation. In this implementation the vehicles perform simultaneous communication and navigation using underwater acoustic modems, encoding and decoding data within the acoustic broadcast. Vehicles calculate range from the time of flight of asynchronous acoustic broadcasts from the reference beacon. Synchronous clocks on the reference beacon and the vehicles enable the measurement of one-way travel-times, whereby the time of launch of the acoustic signal at the reference beacon is encoded in the acoustic broadcast and the time of arrival of the broadcast is measured by each vehicle. The decentralized navigation algorithm, running independently on each vehicle, is implemented using the information form of the extended Kalman filter and has been previously shown to yield results that are identical to a centralized Kalman filter at the instant of each range measurement. We summarize herein the architecture and design of the acoustic communications (Acomms) system consisting of an underwater acoustic modem, synchronous clock, and the software necessary to run them, and salient results from the validation of the decentralized information filter using a simulated data set.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/86057/1/swebster-4.pd

Recent Advances in Synchronous-Clock One-Way-Travel-Time Acoustic Navigation

This paper reports recent results in the development and deployment of a synchronous-clock acoustic navigation system suitable for the simultaneous navigation of multiple underwater vehicles. The goal of this work is to enable the task of navigating multiple autonomous underwater vehicles (AUVs) over length scales of 0(100 km), while maintaining error tolerances commensurate with conventional long-baseline transponder-based navigation systems (0(1 m)), but without the requisite need for deploying, calibrating, and recovering seafloor anchored acoustic transponders. Our navigation system is comprised of an acoustic modem-based communication/navigation system that allows for onboard navigational data to be broadcast as a data packet by a source node, and for all passively receiving nodes to be able to decode the data packet to obtain a one-way travel time pseudo-range measurement and ephemeris data. We present field results for a two-node configuration consisting of a surface ship acting as a global navigation aid to a Doppler-aided AUV.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/86042/1/reustice-26.pd