Nonlinear analysis of a HEV power/drive-train dynamic performance and control

Abstract

Hybrid electric vehicles (HEVs) offer significant improvements on the car travelling autonomy, since they combine an internal combustion engine (ICE) with a pure electric traction. As HEVs become more complicated electromechanical systems, their good performance and response under the driver decisions, the road conditions and the requirement of optimal operation of the main traction devices, constitute a challenging engineering issue. The design of suitable controllers should satisfy all the aforementioned tasks but without any possibility for abnormal or unstable situations which may be dangerous or unsecure for the car passengers. In this paper, since the HEV system is clearly complex and nonlinear, a rigorous analysis is developed in which the nonlinear model of the complete system is considered. Suitable cascaded-mode controllers are applied on the aforementioned models and the whole system is analyzed in detail by using Lyapunov-based methods. The proposed design approach and analysis provide as simple as possible cascaded mode PI control schemes, with the critical controller gains effectively tuned in regions that guarantee asymptotic system stability. Evaluations via standard route conditions fully verify the theoretical results.