Optimal control design for hard disk drive servosystems

The authors present an optimal robust controller design for hard disk drive (HDD) actuator servosystems using direct parameter optimisation taking into account stability restrictions. First, the HDD actuator model is augmented with a state observer. A bound of the stable feedback gain is then calculated by solving a Riccati equation considering the plant parameter uncertainties. To improve the system transient and steady-state performance, the control parameters are selected inside the feedback gain bound using the random neighbourhood search method. Both simulation and implementation results show that an improved digital controller can be obtained for the uncertain HDD plant.