Study On Traction Control For In-wheel-motor Electric City Bus

In short, the distributed driven electric vehicles exhibit a main direction of automotivetechnology for future vehicles, for its simple structure and rapid and precise independentcontrol of the output torque of each wheel. This paper focus on the study of traction controlstrategy for multiaxial in-wheel-motor electric city bus. The main research contents andresults of this paper are as follows:1. Based on vehicle dynamic modeling method, a four degree of freedom of electriccity bus has been established via MATLAB/Simulink, including the driven system model,vehicle body model, tire model and driver model. The platform has laid a foundation forcontrol strategy research.2. To calculate the driver’s demanding torque, the driver’s intention has been studied.Firstly, an adaptive closed loop start control strategy with PI control, based on the motorspeed control has been proposed. In addition, two different accelerator pedal analyticmethods have been proposed. One is single parameter analysis, with the opening ofaccelerator pedal as the input. It has three model, including the general model, dynamicmodel and economic model. The other is the double parameters analysis, with theconsideration of the accelerator pedal opening and changing rate. And the fuzzy controlwas used to calculate the driver’s demanding torque. The simulation results show that thismethod has a faster response to the pedal opening change and the ability to calculate thedriver’s demanding torque more precisely.3. A hierarchical traction control strategy has been proposed. The upper layer is theoptimal torque distribution based on the motor operating efficiency for general longitudinalcase. The torque distribution coefficient matrix has been got by offline optimizationsolution. The simulation results show that this method can effectively improve the economyof vehicle. The lower layer is anti-slip control strategy based on slide model control for theemergency situation. It only starts operating when the slip rate of wheel is exceeding thestable region, in order to improve the vehicle safety and stability. And the simulation resultsshow that the wheel slip could be keep at the optimal value.4. To certify the validity of the proposed control strategy, the hardware in loopsimulations based on dSPACE have been carried, including the experimental research ofaccelerator pedal analytical method and traction control strategy. The experimental resultsshow that the double parameters analysis method have a good response to the change of pedal opening and the optimal torque distribution strategy and anti-slip control strategy canimprove the economy and safety of the vehicle, which is practical and feasible.