Predictive joint motion limiting in robotic applications

Abstract

Summary Three joint space algorithms slow the Cartesian path motion when it appears that joint motion is approaching a joint, speed, or acceleration limit. All three algorithms use quadratic curve fitting to predict where the joint motion is heading, followed by a prediction as to how much time would elapse until a limit is reached. If a joint motion limit is encountered in the time-to-stop the Cartesian motion, these algorithms reduce the Cartesian speed using pulsed speed settings so that the robot or machine tool will have the necessary time to come to a complete stop. The joint space velocity and acceleration control algorithms set the override Cartesian speed to either full or some reduced speed, several times a second. This allows the joints to reach, but not exceed, their maximum velocity and accelerations limit, while remaining within the physical joint limits.