Minimum delay PID control of interpolated joint trajectories of robot manipulators

The digital implementation of an optimal PID (proportional integral derivative) controller of linearly interpolated joint trajectories is presented. The controller obtains optimal performance by reformulating the PID control law to minimize the time delay between the position transducer reading and the application of the corrective torque. Compared with the PID controller that is computed in a straightforward fashion, this formulation reduces the time delay by a factor of three. The superior performance of the proposed minimum-delay PID (MD PID) is demonstrated by experiments on a robot manipulator. Other practical issues associated with a digital PID control of joint trajectories of a robot manipulator, such as integer overflow and compensation for dynamics and joint-friction, are discussed