Active vibration control of a PZT actuated suspension in hard disk drives

This paper presents the design and testing results of active vibration control for a PZT actuated suspension. One PZT strip on the suspension is used as a vibration sensor, and the other as an actuator. A state space model for the PZT actuated suspension was established based on curve-fitted transfer functions, and a feedback damping controller was designed, using the H_∞ controller design method to minimize the peak magnitude of the closed loop transfer function frequency response. An experimental verification of the control scheme was performed. In the experiment, the r.m.s. value of off-track motion due to air-flow excited suspension vibration in the 4-16 kHz range was reduced from 6.0 nm to 3.5 nm for 7200 r.p.m. spindle rotation speed (42% reduction), and from 9.8 nm to 5.9 nm for 10K r.p.m. spindle rotation speed (40% reduction).