Optimal Output Transitions for Dual-Stage Systems

This paper solves the minimum-energy output-transition problem for dual-stage systems, such as dual-stage disk-drives, where the second actuator can be used to increase the bandwidth and precision of conventional single-actuator systems. The objective is to find optimal inputs that change the system output from an initial value to a final value during a specified output-transition time interval. The paper shows that, for dual-stage systems, inputs applied outside the output-transition time interval (i.e., pre- and postactuation) can substantially reduce the required input energy. For an experimental dual-stage system, results are presented to show that the input energy can be reduced by 65% with the use of pre- and postactuation inputs when compared to standard methods that do not use such pre- and postactuation.