Abstract:

With a charge-sustaining PHEV (Parallel Hybrid Electric Vehicle)as the research subject,a system target function with minimum global fuel consumption in the whole driving cycle is set up based on the mathematical models related to the vehicle and its powertrain.The corresponding mechanical and battery constraint functions are also established.Then,the constrained minimum problem is transformed into an unconstrained minimum one,which is solved by using the Lagrange multiplier method,with a global optimization control strategy being obtained.Moreover,a vehicle simulation model is built up based on Matlab/Simulink to verify the proposed strategy in sever-al typical driving cycles.The simulated results are finally compared with those obtained by the instantaneous optimization control strategy.It is then concluded that the proposed strategy is valid and can help save fuel.

Key words: Parallel Hybrid Electric Vehicle, global optimization, control strategy, Lagrange multiplier method