Nonlinear Control of a Vapor Compression Cycle Based on a Partial IOL

This paper presents an innovative model-based control approach of a vapor compression cycle, which relies on a partial input-output linearisation (IOL) for a nonlinear feedback control of the evaporator outlet enthalpy. First, the test rig and the corresponding control-oriented system model are presented. For the inner control loop, the IOL is derived and used for the design of a nonlinear feedback control. Moreover, different extensions are discussed, among them an integral error feedback by means of the heat transfer value and a nonlinear stabilizing feedback control. For the control of the coolant outlet temperature in the outer loop, a PI-controller in combination with an inversion-based feedforward control is employed. The partial IOL-control is tested separately, and the effects of the adaptations are compared in experiments on the test rig. Here, the integral feedback by means of the heat-transfer value improves the control performance significantly, whereas the nonlinear stabilizing feedback contributes to a reduction of the necessary control effort. The overall control approach is validated experimentally on the test rig. Especially the partial IOL-control in the inner loop provides very promising results.