Trajectory tracking performance of modal space decoupled controller for six Degree of Freedom parallel mechanism (6 DOF pm)

The paper presented the trajectory performance of the Modal Space Decoupled Controller (MSDC) and the conventional joint space controller. Phase retarding and amplitude fading were chosen to evaluate how well the modal space decoupling controller can follow a trajectory. The responses of sinusoidal inputs along six directions surge, sway, heave, roll, pitch, and yaw were given. The result indicates that the modal space decoupling controller has better tracking performance when compared to conventional PID controller. For the conventional joint space controller (CJS), the phase retarding for the linear and angular motions motion attains maximum value at 40.90º and 23.98º respectively. The maximum phase retarding is at 22.84º in linear motions and 0.975º in angular motions for the modal space decoupling controller. The amplitude of the conventional controller fades at 0.54dB in linear motions and 0.47dB in angular motions, while for the modal space decoupling controller, the amplitude fades at 0.1696dB in linear motions and 0.082dB in angular motions. Subjecting the two controllers to the tracking of a desired circular combined motion of surge and sway, the predefined circular trajectory was well tracked much more by the proposed MSDC than the CJS.