Automotive engine control and hybrid systems: Challenges and opportunities

The design of engine control systems has been traditionally carried out usi ng a mix of heuristic techniques validated by simulation and prototyping us ing approximate average-value models. However, the ever increasing demands on passengers comfort, safety, emissions, and fuel consumption imposed by c ar manufacturers and regulations call for more robust techniques and the us e of cycle-accurate models. We argue that these models must be hybrid becau se of the combination of time-domain and event-based behaviors. In this pap er, we present a hybrid model of the engine in which both continuous and di screte time-domain as well as event-based phenomena are modeled in a separa te but integrated manner. Based on this model, we formalize the specificati on of the overall engine control by defining a number of hybrid control pro blems. To cope with the difficulties arising in the design of hybrid contro llers, a design methodology is proposed. This methodology consists of a rel axation of the hybrid problem by simplifying some of its components to obta in a solvable problem, and then deriving a solution to the original control problem by appropriately modifying the control law so obtained to take int o consideration the original specifications and models. The effectiveness o f this approach is illustrated on three challenging problems: fast force-tr ansient control, cutoff control, and idle speed control.