Digital PLL-based adaptive repetitive control

The repetitive control achieves zero steady state error by reducing it in iterations based on the error observed in pervious iterations. However, the repetitive control requires that an integer number of samples of the input periodic signal are taken and this could be a problem when the reference period is changing and the sampling rate is fixed. The digital PLL-based adaptive repetitive control is proposed in this paper, where the sampling rate is locked to the reference period so that an integer number of samples per period are maintained at all times