New Method for Sensorless Measurement of Hard Disk Drives Imbalance

At present, hard disk drives (HDDs) are balanced using external balancing machine after all the components of the HDD are assembled. Therefore, company´s throughput is limited by a number of available balancing machines. Besides, an imbalance is measured only once after assembly, and for this reason, there is no possibility to measure if there is any change in imbalance of the HDD during its operation. New method proposed in this paper makes use of the existing head attached to the rotary actuator and position error signal written on the recording media to measure the value of imbalance of the HDD without the need of a balancing machine or any other additional sensors or components. Furthermore, the method enables to monitor and measure any possible changes in imbalance during the life span of the HDD. The proposed method is also attractive to be used in servo-pack writers where the imbalance has to be measured every time a new set of disks is loaded into the writer. Experimental results prove that the method is effective for the measurement of the imbalance of the HDD