engleski

Hybrid Theory Based Time-Optimal Control of an Electronic Throttle

Electronic throttle is a DC motor driven valve that regulates air inflow into the engine's combustion system. The goal of the throttle control system is twofold: to achieve fast and accurate valve plate angle reference tracking, and to preserve outwearing of the throttle by constraining physical variables to their normal-operation domains. These high quality control demands are hard to accomplish since the plant is burdened with a strong nonlinear effects of friction and limp-home nonlinearity. For the purpose of controller synthesis first a discrete-time piecewise affine model of the throttle was developed and then a time-optimal model predictive control problem was solved. We propose a procedure to model friction in a discrete-time piecewise affine form that is suitable for simulation and control. The optimal controller action computation can be restated as a mixed-integer program. However, due to the small sampling time, solving such a program on-line (in a receding horizon fashion) is very prohibitive. In this paper we use recent theoretical results that enable off-line pre-computation of the optimal control law in the form of a look-up table. The technique employs invariant set computation and reachability analysis using multi-parametric programming. Finally, we compare experimental results of our approach with the performance of a tuned PID controller coupled with a feedforward compensation of the nonlinearities. We achieve more than two times faster transients while preserving the quality regarding the absence of an overshoot and static accuracy within the measurement resolution.

constrained time-optimal control; piecewise affine model; friction; unscented Kalman filter; electronic throttle

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