Modeling and output feedback control of automotive air conditioning system

• Validation on experimental data from test vehicle at both steady state and driving cycle.
• Design an output feedback controller using H–infinity synthesis technique.
• Apply singular perturbation method to reduce model and controller orders.
• Test controllers on nonlinear A/C model.

This paper presents an application of robust control theory to an automotive Air Conditioning (A/C) system. A control-oriented model built using moving-boundary method is validated against experimental data collected on a vehicle chassis dynamometer, at constant engine speeds as well as on driving cycles. Next, an H∞ controller is synthesized by formulating an optimization problem whose solution requires appropriate weighting functions selection. Singular perturbation method is utilized to remove states associated with fast dynamics in both model and controller. Both full-order and reduced-order H∞ controllers are verified by simulation results obtained using the nonlinear A/C system model. It is demonstrated that the designed controller is capable of tracking the reference output trajectories while rejecting disturbances introduced on the boundary conditions of the heat exchangers. Furthermore, a preliminary study is performed to reveal the opportunity of designing a gain-scheduled H∞ controller for global output tracking.