Streamlining real-time controller design: From performance specifications to end-to-end timing constraints

This paper presents a control theoretic approach to optimizing end-to-end timing constraints subject to the performance requirements and the schedulability constraint of a real-time control system. The control performance is specified in terms of control output responses such as steady state error maximum overshoot, settling time, and rise time; and the end-to-end timing constraints include loop processing periods and input-to-output latency. Our approach includes a generic real-time controller model on which our analysis is performed, and a heuristic optimization algorithm which derives end-to-end timing constraints. We apply the approach to the design of an embedded real-time controller and validate it through an experimental study using simulation. Our approach contributes to both the control and real-time areas: (1) it allows control engineers to take into consideration the effect of scheduling latency and sampling periods at the early stage of system design; and (2) it makes it possible to streamline the design of real-time control systems, since temporal requirements are derived in an automatic manner. Our approach can be effectively used with the period calibration method as its front-end.