Stability improvement for engine idle-speed control by variable structure control

To improve the responsiveness of engine speed control to disturbances, robust controls were investigated by simulation. The intake air control system of a gasoline ensure is a typical nonlinear system, and the disturbances and parameter perturbations are generally regarded as being the unstable factors with regard to engine control. In this paper, a mean-value engine model (MVEM) with disturbances and parameter perturbations is investigated using sliding mode control (SMC), which is a forms of variable structure control, with a view to addressing instability in the idle speed control process. The simulation results confirmed that, compared with a conventional PI (proportional-integral) controller, the stability of the idle speed for an engine that is being subjected to disturbances, parameter variations and background noise is greatly improved by the application of SMC.