Active vibration control system of fast feed system based on PMAC controller

Active vibration control of the feed support system based on Stewart platform is essential for successfully constructing a Five-hundred-meter Aperture Spherical Telescope (FAST). A flexible control scheme based on RtLinux is proposed and verified in this paper. Considering the weight, volume and precision requirements of the control system, a server-client system is designed, together with a PMAC motion controller to control the servo system. A differential prediction algorithm is applied to the system. Timer interrupt signal is generated by PMAC through PCI bus to the computer. Control algorithm is evoked every RtLinux’s ISR (Interrupt Service Routine), during which sampling and forecasting calculation are accomplished and the result is written into Dual-Ported RAM (DPRAM) on PMAC. PMAC, then, reads the data from DPRAM and carries out the interpolation and outputs the analog signals generated by PID control algorithm achieved by hardware itself to the servo motor. In this process, the accuracy of the system is guaranteed by the realtime property of RtLinux’s interrupt handler and PMAC’s powerful motion control functions. Meanwhile, the open architecture of PMAC for user written servo algorithms also offers a convenient software and hardware interface for the improvement of the control algorithm in the future.