Energy-optimal control of an automotive air conditioning system for ancillary load reduction

The air conditioning system is currently the largest ancillary load in passenger cars, with a significant impact on fuel economy and CO₂emissions. Considerable energy savings could be attained by simply adopting a supervisory energy management algorithm that operates the A/C system to reduce power consumption of the compressor, while maintaining the cabin comfort requirements. This chapter proposes a model-based approach to the design of a supervisory energy management strategy for automotive air conditioning systems. Starting from an energy-based model of the A/C system that captures the complex dynamics of the refrigerant in the heat exchangers and the compressor power consumption, a constrainedmulti-objective optimal control problem is formulated to jointly account for fuel consumption, cabin comfort, and system durability. The trade-off between fuel economy, performance, and durability is analyzed by performing a Pareto analysis of a family of solutions generated using dynamic programming.A forward-looking optimal compressor clutch policy is then obtained by developing an original formulation of the Pontryagin’s minimum principle for hybrid dynamical systems. The simulation results demonstrate that the proposed control strategy allows for fuel economy improvement while retaining system performance and driver comfort.