Servo loop gain identification and compensation in hard disk head-positioning servo

The servo loop gain in the track-following servo depends on head flying height, length of magnetic fringing field, and magnetic flux density of actuator. The loop gain variation should be suppressed for uniform servo performance over all track locations. In this paper, we present a new approach to the identification and compensation of servo loop gain. The identification algorithm is based on sinusoidal excitation and measuring open loop frequency response. The experimental results show that loop gain variations can be reduced significantly by applying our identification algorithm.