A disk file servo control system with fast reduction of repeatable head position error

摘要

n improvement to a disk file servo control system removes repeatable error from the read write head position error signal (PES) during track following. The disk file includes a microprocessor 60 and associated memory devices 62,64. A table of values of a sine function having a frequency equal to the disk rotational frequency is stored in a memory device. The microprocessor 60 receives each sample of PES from the servo control system and values from the sine function table in the memory device and computes a group of tap weights, each tap weight being a function of the PES sample, the value of a sine or cosine function with a frequency at one of the harmonics of the disk rotational frequency, a learning ratefac- tor and the corresponding value of the tap weight for the previous PES sample. For each PES sample, the tap weights in a group are added to generate a repeatable error correction signal Uc which is summed with the control signal U to the head actuator, thereby generating a modified control signal Um which causes the head to follow the true track centerline. The repeatable error components are thus removed from the PES.