Modeling method for position control of full digital AC servo systems

A new method for modeling full digital AC servo motors in discrete pulse control was proposed. The position pulse control mode and its expression of the full digital AC servo system were analyzed, and in speed PI control the transfer functions of the AC servo system and the system lag pulse were derived. A comparison of responses of pulse series during different periods and forms of the AC servo system in the simulation and experiment shows that the speed error caused by the system lag pulse is mainly proportional to the acceleration of the input pulse, and as inflexion in speed curve (acceleration jump) occurs the speed error jumps with its amplitude proportional to the jerk. To avoid large jump in speed error and realize high precision motion control, the continuous change of acceleration must be guaranteed in the speed control process. And the compute speed errors well coincide with the experimental results despite of the input signal forms, which verifies the correctness of the presented modeling method.