Designing Dynamic Temporal Controls for Critical Systems

Abstract

Traditional control systems have been designed to exercise control at regularly spaced time instants. When a discrete version of the system dynamics is used, a constant sampling interval is assumed and a new control value is calculated and exercised at each time instant. In this paper, we propose a new control scheme, {\it dynamic temporal control}, in which we not only calculate the control value but also dynamically decide the time instants when the new control computations have to be calculated. Taking a discrete, linear, time-invariant system, and a cost function which reflects a cost for computation of the control values, as an example, we show the feasibility of using this scheme. We implement the dynamic temporal control scheme in a rigid body satellite control example and demonstrate the significant reduction in cost. The scheme proposed here can be implemented using real-time operating system, such as {\em Maruti}, which schedules activities along the time axis. The reduced computations for control permit the use of the same processor for higher level functions resulting in a significant improvement in the performance of the overall system. (Also cross-referenced as UMIACS-TR-97-51)