Research On Energy Saving Of Four-wheel Drive Battery Electric Vehicle Based On The Road Alignment

Energy conservation and environmental protection are the eternal themes of the development of the times.Intelligent networking and electrification have brought new opportunities for the development of automobile energy conservation and environmental protection.Using ramp and curve information to plan an economical car displacement speed curve can effectively improve the car’s driving range.This puts forward new requirements for the driving range of electric vehicles,and the nature of energy-saving technologies for electric vehicles has become increasingly prominent.Four-wheel-drive pure electric vehicles have better dynamics and higher degrees of freedom,which have been widely adopted.Here,energy-saving technology research is carried out for the reformed Dongfeng E70 vehicle.The power consumption model includes two modules:mechanical response characteristics and efficiency characteristics.The modeling of the battery parameter model is completed,which can accurately reflect the electric energy consumption of the car as the evaluation basis for the subsequent algorithm.The establishment of the previous model of the entire car is completed in the Carsim software,and the previous model established previously is connected to it.On the basis of the built model,dynamic programming algorithm and model predictive control algorithm are respectively used here for economical speed planning and control.The linear dynamics equations of the car are established in the time domain and the space domain.The time domain equation is used in the working conditions of the curve,taking into account the curvature of the curve and the superelevation information,and establishing the constraint conditions of the safe vehicle speed.It is very convenient to join the constraints of dynamic programming algorithms and model predictive control algorithms.This meso-level energy-saving technology is the basis for subsequent harmonic distribution research.In order to improve the efficiency of the electric drive system,a universal inverter distribution strategy for four-wheel-drive pure electric vehicles is proposed.This strategy is based on the above-mentioned speed planning.Under the total expected torque given by the planning algorithm,the distribution strategy is optimized to consider the large torque and offset range of the front and rear permanent magnet synchronous motors and inverters.Using the 6th power function to fit the corresponding asynchronous and power loss values under the instantaneous transition in the motor mapping,the total power loss function of the front and rear wheels is established and the optimal distribution coefficient is obtained.It can reflect the characteristics of braking energy recovery.The results show that when the required power decreases,the maximum efficiency can be obtained by switching to the two-wheel drive mode.When the power is required to be transmitted,it is more efficient to use the front and rear wheels to distribute evenly.Finally,a variety of simulation conditions of ramps and curves are established in the Carsim software to evaluate the energy-saving effect of the energy-saving technology proposed in this paper under different driving scenarios.The results show that the comprehensive optimal optimization of the dynamic programming algorithm is about 10.91%,and the comprehensive optimization of the model predictive control algorithm is about 9.25%on the slope of about 10%.In a curve,different curvatures will lead to different optimization results,and the optimization effect of general curvature conversion is more obvious.Compared with the average distribution algorithm,the efficiency-based efficiency distribution algorithm can bring about 4.29%additional energy-saving effect.