Lapping control of Hard Disk Drive Heads (II): Control

Using numerical modeling as a tool, the pressure dynamics of bar lapping is identified. The process model is constructed based on the pressure dynamics and the Preston model. A controller is then designed using a trajectory following formulation. Simulation of the controller designed as such shows that it is robust to parameter uncertainties. This controller is implemented on a Seagate lapping system. Experiment results show that the proposed method is less sensitive to the quality of the preparation processes. However, the gains should be appropriately adjusted for optimal performance. With good preparation processes and appropriate gains, performance of die two methods are statistically comparable. Otherwise, the proposed method performs better. The proposed method is inferior to the existing method only when its gains are improperly adjusted.