A novel mid-ranging approach for idle speed control of a hybrid electric powertrain

In this paper the problem of idle speed control for the powertrain of a hybrid electric vehicle is investigated. On the one hand, the proposed control structure ensures control of the powertrain's idle speed, by using the electric motor as a secondary actuator besides the combustion engine. On the other hand, it enables the use of the electric motor as a generator by appropriate load level shifting. The coordination of the two actuators is provided by a novel control structure, which is based on the idea of mid-ranging control. Based on a nonlinear system description, a suitable design model is derived, capturing the fundamental properties of the powertrain. The nonlinear dynamic behavior of the intake manifold pressure is handled via an inversion-based linearization. The controller design itself is based upon a frequency shaped LQG design, which allows for explicit consideration of the powertrain's oscillatory behavior, which is due to a dual mass flywheel. Time delays, which occur in both the plant input and output channels, are encountered by extending the LQG Kalman filter with a predictor. Finally, measurements from a passenger car are presented to validate the performance of the new controller structure.