Implementation of repetitive controller for rejection of position-based periodic disturbances

Time-varying periodic motions have appeared in many industrial processes, such as cam-follower systems, in that the control system has to operate at a periodic variable velocity specified in terms of the angular position-domain. This paper employs a repetitive control for rejecting the time-varying periodic disturbances, and presents an implementation technique based on angular position which can generate a fixed number of cycles in real-time. This control technique can accommodate the period variation in a time-varying periodic signal such that variable samples per period for synchronization can be achieved by the regular fixed-time sampling rate. A technique using position information to manipulate the delayed data and an interpolation scheme to properly access data in the buffer memory is proposed. An anti-vibration control system with time-varying periodic disturbances is studied to illustrate control performance. The experimental results are given to illustrate that time-varying repetitive control can effectively eliminate steady-state errors within a few cycles.