RRO compensation of HDD based on RPTC method with re-learning scheme for discreate track recording media

This paper presents an improvement method of repetitive controller based on perfect tracking control (PTC) in order to reject variable repeatable runout (RRO) of hard disk drive. Authors´ group proposed the repetitive PTC (RPTC) with switching mechanism. RPTC is constructed by using periodic signal generator (PSG) and PTC. The PSG works to make feedforward signal from the periodic disturbance and the PTC generates control input to cancel the periodic error in steady-state. However, we have not considered the difference of RRO between tracks. This paper proposes a re-learning scheme considering correlation of adjacent tracks. Finally, the advantages of RPTC using proposed scheme are demonstrated through simulations and experimens with HDD equipment with discrete track recording media (DTR).