Dynamic sliding mode control of an innovative engine cooling system

In this paper, a robust nonlinear control approach based on a control-oriented model of an engine cooling system for vehicles is presented. The angular velocity of an electrically driven radiator fan is considered as the control input to adjust the cooling heat flow corresponding to a desired engine cooling performance. For smooth control actions and an avoidance of chattering, a dynamic sliding mode control is presented to track the desired trajectories of the engine outlet temperature. For the estimation of unmeasured heat flows, a gain-scheduled version of a modified Utkin sliding mode observer is employed, which uses both an output error feedback and a switching term for the stabilisation of the observer error. The estimated heat flows are used in the control design to compensate for the disturbances acting on the system. Experiments on a dedicated test rig highlight the effectiveness of the robust observer-based control strategy during the normal vehicle operation as well as a start/stop scenario.