Modeling and compensation of pivot friction in a drive actuator

With the trend towards smaller form factor disk drives and higher recording densities, frictional effects on the head positioning servo system is receiving increased attention. In this paper, a time-domain stick-slip friction model is proposed for representing the pivot friction. Experimental measurements are made to validate and characterize the model parameters. A discrete-time disturbance observer is incorporated into the conventional state feedback controller to compensate for pivot friction. The track following algorithm is then merged with the proximate time optimal servo (PTOS) algorithm for track seeking. Simulations and analysis are performed in MATLAB and results compared with normal state feedback controllers to show how the proposed control structure can improve friction compensation.