Adaptive-Q with LQG stabilizing feedback and real time computation for disk drive servo control

A method of stabilizing feedback control, known as adaptive-Q control is applied to a LQG disk drive control system to improve its disturbance rejection property. This approach follows the well known result that all stabilizing controllers for a plant can be synthesized by conveniently parametrized augmentations to a nominal controller. The augmentation is parametrized by an arbitrary stable filter Q which is adapted online. The Q filter is restricted to a FIR stable filter which minimizes the H/sub 2 /norm of the transfer function from the disturbance to the track following error. Simulations and experimental results show a 15% improvement in the achievable TMR (track misregistration). The Q filter is adapted using a recursive least squares numerically stable adaptive array algorithm. Two algorithms based on inverse QR factorization are considered for implementation. The computation issues involved in updating the Q filter every servo cycle are discussed.