Increased disturbance rejection for hard disk drives by using accelerometers

The direct adaptive control scheme presented in this paper uses an accelero meter signal to improve the external disturbance rejection capability of tr ack-following servos in hard disk drives. The adaptive controller acts as a n add-on compensator to an existing fixed compensator. The accelerometer is mounted on the base casting of the disk drive in order to obtain a measure of the disturbance. This acceleration measurement is fed forward by the ad aptive controller. The objective of the scheme is to minimize the variance of the position-error signal in the presence of external disturbances. The proposed adaptive control scheme was implemented on a TMS320C40 digital sig nal processing board and was tested on a commercially available 2.5 in. dis k drive. The disk drive was subjected to a number of different external vib rations tests. Experimental results display attenuations up to 30 dB and im provements of 89% in the variance.