Motion Coordination Based on Multiple Performance Criteria with a Hyper-Redundant Serial Robot Example

Richard Hooper Delbert Tesar
The University of Texas at Austin
Department of Mechanical Engineering
Robotics Research Group
Austin, Texas 78712-1100

Abstract
This paper describes a method of redundancy resolution that combines closed-form inverse kinematics with multicriteria optimization to form a method able to coordinate the motion of a hyper-redundant serial robot at deterministic speeds greater than 100 cycles per second on a personal computer. The work includes a listing of over 30 task-based performance criteria derived from physical models of the robot and presents explicit formulations for several of them. It discusses a motion coordination method that explicitly generates motion options, evaluates them, and then ranks them. The highest-ranking option becomes the next motion command for the robot's servo controllers. Finally, the paper presents a simulation of motion coordination for a hyper-redundant serial robot with 21 Degrees Of Freedom (DOF).

Introduction
A redundant robot is an extremely complex system with coupled and noli-linear kinematics and dynamics involving issues of speed, dexterity, precision, force transmission, and disturbance rejection. This paper represents the position that no single performance criterion suffices to coordinate the motion for these robots.

Multiple performance criteria form the basis for motion coordination in this work. These criteria emphasize task-based performance measures derived from the physical description of the manipulator. The origins of these criteria are from foundation activity in high speed mechanisms for production machinery (Benedict and Tesar. 1978). There, the issues of precision and modeling of complex non-linear structures forced the development of a geometric understanding for mechanical structures and how to represent them with efficient analytical tools. Thomas and Tesar (1982) showed that the concept of kinematic influence coefficients (used in systems with 1 DOF) were effective in spatial manipulator structures with N DOF..

While most roboticists must intuitively agree that multiple criteria assess the true performance of a robot, incorporating these criteria in a real-time motion coordination method is a challenging pursuit. This paper describes a method that combines closed-form reverse position analysis, local exploration, and a multicriteria decision making process. The closed-form reverse position analysis satisfies the placement constraints on the robot's End-Effector (EEF). The local exploration generates a set of configuration options. The decision making process uses the performance criteria to evaluate the options and choose one as next set-point command for the robot's servo controllers.

R. Hooper, D. Tesar. “Motion Coordination Based on Multiple Performance Criteria with a Hyper-Redundant Serial Robot Example.” Proceedings of the 1995 IEEE International Symposium on Intelligent Control, 27-29 Aug. 1995, Pages: 133 – 138.