Preferable movement of a multi-joint robot arm using genetic algorithm

To control the position and movement of an end-effector on the tip of a multi-joint robot arm is known to include a kind of redundant problem. Although the end-effector is set its position by each angle of the joints, the angle of each joint cannot be uniquely determined by the position of the end-effector. Each of infinite number of different sets of joint angles usually represents the same position of the end-effector. This paper describes how to control the angle of each joint to move its end-effector from a starting point to an ending point on an X-Y plane preferably. We first separate standpoints into two to define the preferable movement; 1) the standpoint of the end-effector, and 2) the standpoint of the joints. Then, we define multiple objective functions from each standpoint Finally, we formulate the problem into a multi-purpose programming problem. We apply a genetic algorithm to solve this problem and obtain satisfied solutions, which have a smooth movement of the end-effector and less rotation of the joints. This paper is suggestive that the approach described here can easily be extended to a problem with a multi-joint robot arm in a three-dimensional space, and also to a problem with obstacles between starting and ending points.