Automatic P/PI speed control for industry servo drives using on-line spectrum analysis of torque command

Conventional proportional/proportional-integral (P/PI) speed controller of today's servo drives should be manually tuned the controller switching set-point by trial and errors, which may translate the drive system down-time and loss of productivity. The adjustable drive performance is heavily dependent on quality of the expert knowledge and becomes inadequate in applications where the operating conditions change in a wide range, i.e., tracking command, acceleration/deceleration time, and load disturbances. In this paper, the demands on simple controls/setup are discussed for industry servo drives. Analyzing the frequency content of motor torque command, P/PI control mode switching is automatically performed with some prior knowledge of the mechanical dynamics. The dynamic performance of the proposed scheme assures a desired tracking response curve with minimal oscillation and settling time over the whole operating conditions. For comprehensive comparison of traditional P/PI control scheme, extensive test is carried out on actual servo system.