Bias Compensation for Fast Servo Track Writer Seek Control

This paper presents fast servo track writer seek control for unknown bias compensation and minimum resonance excitation. An add-on type discrete-time disturbance observer is also employed to obtain uniform settling performance in the presence of disturbance. To prevent a chattering effect due to the unstable zero dynamics of servo track writer, we propose a new disturbance observer dynamics. A two-degree-of-freedom control is used with the reference profile design based on the frequency shaped final-state control and compensation of phase mismatching. We analyze the experimental results of the servo track writer for fast seeking and settling. The proposed control scheme is validated by experimental results showing improvements in seeking and settling performance.