Model Predictive Control of Engine Speed During Vehicle Deceleration

We consider the speed control of a spark ignition engine during vehicle deceleration. When the torque converter bypass clutch is open, the engine speed needs to be kept close to the turbine speed to guarantee responsiveness of the vehicle for subsequent accelerations. However, to maintain vehicle drivability, undesired crossing between engine speed and turbine speed must not occur, despite the presence of significant torque disturbances. Hence, the engine speed during vehicle decelerations needs to be precisely controlled by feedback control, which has to coordinate airflow and spark timing and enforce several constraints including engine stall avoidance, combustion stability, and actuator limits. We develop a model predictive controller that manipulates airflow and spark to track the reference signal for engine speed while enforcing constraints, and synthesize it in the form of a feedback law. The controller is evaluated in simulations and in a vehicle, and it is shown to achieve a responsive and consistent deceleration and the potential for reducing fuel consumption.