Direct teaching and automatic program generation for the hybrid control of robot manipulators

Abstract

A methodology for the automatic generation. of robot programs for hybrid position/force control is presented. While hybrid control allows a robot to perform skillful manipulations, its programing is more complex and intricate than simple position control schemes. In hybrid control, control modes must be designated to individual C-frame axes, in such a way that the robot motion conform to geometrical or natural constraints. Both position and force reference inputs must be provided as artifical constraints. This is difficult , since it requires the interpretation of a given task and the translation into a set of commands used in the hybrid position/force control. In this paper, an efficient method is developed to eliminate manual programming and task interpretation/translation. The operator teaches a given task by "teaching-by-showing", in which the operator contacts the robot end effector to the environment, and accommodates the contact force. During the operator's motion, the force applied by the operator as well as the position of the end effector are measured, The acquired motion data are then processed and interpreted so that necessary information to generate robot programs is obtained. The choice of control modes as well as reference inputs to the robot controller are derived from the motion data. Then the result is translated into a robot program. First, the principle of this method is described. The algorithm to interpret motion data is then developed for a simple palletizing job. The method is implemented on a force-controlled direct-drive arm using a personal computer.