Workspace Boundary Avoidance in Robot Teaching by Demonstration Using Fuzzy Impedance Control

Abstract

The present paper investigates an intuitive way of robot path planning, called robot teaching by demonstration. In this method, an operator holds the robot end-effector and moves it through a number of positions and orientations in order to teach it a desired task. The presented control architecture applies impedance control in such a way that the end-effector follows the operator's hand with desired dynamic properties. The operator often teaches the robot in the middle of the robot workspace. Then, this leads to lose a lot of accessible space. Workspace boundary is specified where a joint meets its end or a singularity happens. In this paper, a method is proposed to warn the operator before the end-effector faces the boundary of the workspace which results in using the robot workspace efficiently. It is achieved by means of two fuzzy controllers which smoothly increase the damping parameter of the impedance controller when the robot is closing on to a joint limit or a singularity. The increase of damping parameter dissipates the kinetic energy that is imposed by the operator to move the end-effector toward workspace boundary. The proposed method is applied on an industrial grade SCARA type robot. Experimental results show the effectiveness of the proposed method in a clear way.