Minimum ratio-locked profile times for robot trajectories

Abstract

A graphical representation of admissible profile times for robot trajectories is presented from a kinematic perspective. Profie times are defied to be the acceleration time, slew time, and deceleration time for robot end effector motions. Given initial and f i a l robot end effector locations, identical profile times are computed for all the joints in the manipulator, where each joint has merent acceleration and velocity limits. Ratio-locked profile times occur when the robot motion is joint coordinated with all of the joints moving in a proportional manner relative to each other.The ability to have ratio-locked profie times results in smooth, well behaved end effector motions that are path invariant at different robot speeds. A dosed form solution to compute the minimum ratio-locked profile times for robot trajectories is presented for the case when the acceleration limit for each joint is equal to its deceleration limit. The solution is straightforward and may be used to compute the profile times in real time. The algorithm is implemented in the HAL robot control system at HP Labs for controlling robots in a manufacturing environment.