Time-Optimal Control With Pre/Post Actuation for Dual-Stage Systems

This paper considers the output transition problem, to change the output position, from an initial value to a final value, for dual-stage positioning systems. The main contribution of this paper is to show that the use of pre- and post-actuation input (applied outside the transition interval without changing the output) can reduce the transition time beyond the standard bang-bang-type inputs from the optimal state-transition approach. Moreover, the paper shows that, without pre- and post-actuation, the minimum transition time cannot be lower than the rigid-body, transition time with only the main actuator if the second actuator cannot apply external forces. An example, motivated by the disk-drive application, is used to illustrate the advantages of using: 1) pre- and post-actuation and 2) the second actuator in dual-stage positioning system.