Abstract
The hybridization of the conventional thermal vehicles nowadays constitutes a paramount importance for car manufacturers, facing the challenge of minimizing the consumption of the road transport. Although hybrid power train technologies did not converge towards a single solution, series/parallel power trains with a power-split electromechanical transmission prove to be the most promising hybrid technology. In fact, these power trains show maximum power train overall efficiency and maximum fuel reduction in almost all driving conditions compared to the conventional and other hybrid power trains.
This paper addresses the model and design of one of the most effective HEV power train: case study of the 2nd generation Toyota Prius. It presents the simulation work of the overall operation of the Toyota Hybrid System (THS-II) of the Prius, and explores not only its power-split eCVT innovative transmission system, but also its overall supervision controller of the mechanical and electrical systems. The kinematic and dynamic behaviors of the THS-II power train are explained based on the power-split aspect of its transmission through a planetary gear train. Then, the possible regular driving functionalities that result from its eCVT operation and the energy flow within its power train are outlined. A feed-forward model of the studied power train is next proposed, supervised by a rule-based engineering intuition controller. The model encloses the modeling of the vehicle dynamics, the power train dynamics and its associated overall governing matrix of its series/parallel operations, the power train components and their relative ECUs, in addition to the overall vehicle ECU and the battery ECU. A PID feedback controller emulating the driver behavior is used. It generates the acceleration and braking commands in order to enable the forward-facing simulation.
The model is then calibrated and validated with road test measurements realized on a MY06 Prius in Ile-de-France, in terms of the power train performance and energy consumption, taking into consideration the effect of the auxiliary consumption and the driver’s attitude.
Keywords: Hybrid power train, power-split eCVT, rule-based control strategy, Toyota Hybrid System, driver’s attitude, auxiliary consumption, dynamic forward-facing model.