Performance Enhancement for Rotational Systems Tracking Position-Dependent Periodic Signals

This article first presents an extended state observer (ESO)-based spatial repetitive control (SRC) method that improves the tracking performance for position-dependent time-varying periodic reference signals for a multidisturbance rotational system. First, a spatially modified repetitive controller (SMRC) is constructed, which includes a spatial internal model of a time-varying periodic reference signal. Second, using the differential flatness property and the known model information of the rotational system, an ESO is constructed to estimate and compensate for the combined effect of the multiple temporal disturbances. Third, a digital implementation method for the SMRC is developed, which ensures the synchronization of the SMRC and the temporal ESO-based control through a regular fixed-time sampling. The stability analysis of the system and the design of the SMRC and the ESO are given in detail. Finally, comparative experiments on a variable-speed rotational system demonstrate that our method outperforms ESO-based control methods and other SRC methods.