The Control Strategy for 4WD Hybrid Vehicle Based on Wavelet Transform

In this paper, in order to avoid the frequent switching of engine operating points and improve the fuel economy during driving, this paper proposes a control strategy for the 4-wheel drive (4WD) hybrid vehicle based on wavelet transform. First of all, the system configuration and the original control strategy of the 4WD hybrid vehicle were introduced and analyzed, which summarized the shortcomings of this control strategy. Then, based on the analyze of the original control strategy, the wavelet transform was used to overcome its weaknesses. By taking advantage over the superiority of the wavelet transform method in multi signal disposition, the demand power of vehicle was decomposed into the stable drive power and the instantaneous response power, which were distributed to engine and electric motor respectively. This process was carried out under different driving modes. The proposed control strategy not only ensured the dynamic property, but avoided the frequent switching of engine operating points by making the most of the fast-transient response of electric motor. Last but not least, in MATLAB/Simulink environment, the vehicle model and the control strategy model were built. Compared with the original control strategy, the simulation results showed that the proposed control strategy could reduce the range of engine operating points and make them more concentrated, which could effectively improve the working condition of engine. As a result, the proposed strategy improved the fuel economy, which verified the effectiveness of the control strategy based on wavelet transform.