Optimal output transitions for dual-stage systems: Disk drive example

The minimum-energy output-transition problem for dual-stage systems is solved in this article. The objective is to find optimal feedforward inputs, that change the system output from an initial value y at time t(i) to a final value y at time t(f) during a specified output-transition time-interval [t(i), t(f)]. The main contribution of this article is the solution of the optimal output-transition problem for systems with actuator redundancy (dual-stage systems). Additionally, we show that the use of pre- and post-actuation inputs, outside the output-transition time-interval, can lead to substantial reduction of the output-transition cost. In particular, the method is applied to a dual-stage disk drive model and simulation results are presented. The results show that the output-transition cost (input-energy) can be reduced by 97% with the use of pre- and post-actuation inputs when compared to standard methods that do not use such pre- and post-actuation.