Second-order sliding mode control of an innovative engine cooling system

In this paper, a robust nonlinear control approach based on a simplified control-oriented model of an engine cooling system for vehicles is presented. An electrically driven radiator fan is considered as a control input. Based on the system description, a second-order sliding mode control is proposed to track desired trajectories of the engine outlet temperature. The second-order sliding mode control provides a smooth control action and reduces the chattering phenomenon with the introduction of a first-order time derivative of the sliding manifold. A gain-scheduled modified Utkin sliding mode observer, which uses both an output error feedback and a switching term, is employed to estimate unknown heat flows within the system. The estimated heat flows are used in the control design in order to compensate the disturbances acting on the system. An experimental analysis highlights the effectiveness of the second-order sliding mode control in combination with a sliding mode based observer design.