Modeling for drivability and drivability improving control of HEV

A hybrid electric vehicle has more than one energy source and switching between the two sources leads to significant drivability problem. Drivability is used to describe the comfort of driving a vehicle under a wide variety of operating conditions like tip-in, tip-out, and gear shifting. Vehicle drivability is one of the keystones of product quality and is refined aggressively to achieve product differentiation and market position. Specific aspects of drivability problems can be improved using modern control techniques. In this paper, a generic model of the driveline of a plug-in hybrid vehicle is developed. Drivability evaluation indices have been developed and were used for evaluating the drivability performance. Analysis and measurements of the actual components of this vehicle followed by parameter identification based on experimental data are used to obtain a validated version of the driveline model. A comparison of the driveline under consideration with changes in critical parameters is presented to demonstrate the effect of these parameters on drivability. The paper then focuses on improving the tip-in and tip-out drivability problem by proposing a control architecture consisting of an input shaping feedforward control filter and a feedback controller around an inner disturbance observer loop. The proposed controller is tested in both simulations and in experimental road tests and is shown to improve the drive quality of the vehicle significantly.