Replacing a PID controller by a lat-lead compensator for a robot-a frequency-response approach

Because of their simplicity, PD (Proportional-derivative) or PID (proportional-integral-derivative) controllers are widely used with various robot control strategies. For dynamic control of robots, this algorithm can be shown to lead to unsatisfactory tradeoffs between static accuracy, system stability, and insensitivity to disturbances. These tradeoffs become more serious as the sampling rate decreases. By deriving a more realistic discrete-time system model and using frequency-response analysis, a lag-lead compensator is designed and implemented. Both theoretical analysis and real tests are given for the comparisons of the PD or PID controller and the lag-lead compensator. Replacing PD or PID controllers by lag-lead compensators results in a small increase of offline design and tuning effort and online computational load, but the improvements in robot performance are significant