Coordination of engine and transmission using hybrid control methodologies

Automotive powertrain systems represent an important class of practical hybrid systems which are characterized by the following features: (1) the systems are inherently hybrid, i.e., hybrid control is not merely a choice. This is exemplified by transmission gear positions (discrete) and engine throttle control (analog); (2) system dynamics are highly nonlinear and contain parametric errors and structural uncertainties. In the paper, a hybrid control design approach is used to develop control strategies for coordination of automotive engine and transmission systems. The main goal is to achieve driving performance, fuel economy, and robustness, with emission as a constraint. The design procedure follows closely the main ideas of the method introduced in Wang et al. (1997). The method employs performance indices in guiding both analog and discrete control actions such that robust stability and performance of closed-loop hybrid systems are maintained in the presence of modeling errors, disturbances, and structural uncertainties. The method is further modified to accommodate practical constraints, including actuator saturations, gear shifting limitations, and real-time computation requirements.