Trajectory Planning of Semiconductor Wafer Transfer Robot Arm Driven by Stepping Motors Using Genetic Algorithm and Experiments

摘要

In this paper, the trajectory planning method of a semiconductor wafer transfer three-joint robot arm driven with stepping motors by use of the genetic algorithm is proposed, and the experimental results are demonstrated to confirm the usefulness of the present trajectory planning method. The whole trajectory consists of three trajectory portions; a straight line trajectory portion to take out the semiconductor wafer, a curved line trajectory portion under PTP action, and a straight line trajectory portion to set the semiconductor wafer. In the trajectory planning, the three trajectory portions are expressed by polynomials, and, by using the continuous conditions concerning joint angles, joint angular velocities and joint angular accelerations, the whole trajectory is described by a chromosome consisting of five genes. Then, the fitness function of the genetic algorithm for the quasi minimum time control under the constraint condition that the stepping motor torques should not exceed pull-out torques is defined, and the trajectory planning algorithm is constructed. Furthermore, the numerical calculations have been carried out, and it is confirmed that the trajectory planning can be successfully executed. Additionally, from the experimental results, it is ascertained that the trajectory tracking control of the trajectory of the semiconductor wafer transfer robot can be exactly implemented.