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PARAMETER IDENTIFICATION FOR A ROBOTIC MANIPULATOR ARM

IP.com Disclosure Number: IPCOM000128823D
Original Publication Date: 1985-Dec-31
Included in the Prior Art Database: 2005-Sep-19
Document File: 10 page(s) / 32K

Publishing Venue

Software Patent Institute

Related People

D.W. BREWER: AUTHOR [+4]

Abstract

This paper describes the development of a nonlinear dynamic model for large oscillations of a robotic manipulator arm about a single joint. Optimization routines are formulated and implemented for the identification of electrical and physical parameters from dynamic data taken from an industrial robot arm. Special attention is given to the role of sensitivity in the formulation of robust models of this motion. The importance of actuator effects in the reduction of sensitivity is established and used to develop an electro-mechanical model of the manipulator system. Research was supported by the National Aeronuatics and Space Administration under NASA Contract No. NAS1-17070 while the authors were in residence at ICASE, NASA Langley Research Center, Hampton, VA 23665-5225.

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THIS DOCUMENT IS AN APPROXIMATE REPRESENTATION OF THE ORIGINAL.

PARAMETER IDENTIFICATION FOR A ROBOTIC MANIPULATOR ARM

D. W. Brewer Institute for Computer Applications in Science and Engineering and J. S. Gibson University of California, Los Angeles

Abstract

This paper describes the development of a nonlinear dynamic model for large oscillations of a robotic manipulator arm about a single joint. Optimization routines are formulated and implemented for the identification of electrical and physical parameters from dynamic data taken from an industrial robot arm. Special attention is given to the role of sensitivity in the formulation of robust models of this motion. The importance of actuator effects in the reduction of sensitivity is established and used to develop an electro-mechanical model of the manipulator system.

Research was supported by the National Aeronuatics and Space Administration under NASA Contract No. NAS1-17070 while the authors were in residence at ICASE, NASA Langley Research Center, Hampton, VA 23665-5225.

1. Introduction

The purpose of this research is to develop and investigate methods for identifying parameters in a dynamic model of a robotic manipulator. Identification routines of this type are important in the construction of control algorithms for manipulator systems [4]. Because the parameter identification must be based on input and output data from an assembled manipulator, which acts under gravity and has possibly complicated joint friction, the dynamic model is a nonlinear differential equation, which must be solved numerically.

The approach used to date is to employ a nonlinear search routine to minimize a quadratic fit-to- data criterion formed using the experimental data and the solution to the model equation. This method has been applied to a Unimation 600 Puma arm, with data obtained by F. W. Harrison in the Intelligent Systems Robotics Laboratory at the NASA Langley Research Center.

Section 2 describes the mathematical model of the manipulator arm and the parameters to be identified. Section 3 describes the parameter identification scheme and the computer algorithms used. In Section 4, the experiment is discussed in more detail, along with some preliminary data reduction and analysis of the relationship between angular velocity and torque. Section 5 presents an analysis of the sensitivity of the manipulator arm model to perturbations of uncertain parameters and initial conditions. We also discuss a method for reducing this sensitivity which in this application corresponds to the inclusion of a back electromotive force in the arm model. In Section 6 we discuss the results of the parameter estimation routines for several models of robot arm friction.

2. Manipulator Model

National Aeronautics and Space Administration Page 1 Dec 31, 1985

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PARAMETER IDENTIFICATION FOR A ROBOTIC MANIPULATOR ARM

To minimize the number of unknown parameters in each set of data, each experiment was performed...