Design of discrete controllers for continuous systems using hybrid Chi

Abstract. Controllers of continuous systems are usually discrete, because of the sampling required by computer implementations. The controlled physical systems are often nonlinear. It is therefore important that tools and languages for control system design provide adequate support for dealing with these phenomena. The χ language, presented in this paper, provides such support. It is suited to specification and simulation of control systems of a continuoustime, discrete-event or discrete-time nature. Such control systems may range from stand-alone controllers to interacting plant-wide control systems. The language integrates a small number of orthogonal continuous-time and discrete-event concepts. The continuous-time part of χ is based on differential algebraic equations; the discrete-event part is based on a CSP-like concurrent programming language. A case study is presented of a tank level control system. Several control strategies are modelled, including a PI controller with anti-windup