Research On Differential Steering Performance Of Four-wheel Independent Drive Electric Vehicle

The current environrental pollution problem has received widespread attention and the environment has continued to deteriorate.According to statistics,the pollution of automobile exhaust has a great impact on environmental pollution,The replacement of traditional internal combustion engine vehicles by new energy vehicles has become a future development trend.Since the power system of electric vehicles has better advantages than the power system of internal combustion engines,and the layout of power systems is diversified,the independent driving technology of in-wheel motors has become a new research in the research of drive systems due to the good characteristics of independent driving technology of in-wheel motors.The hot spot also gave birth to a form of steering characterized by differential steering.Based on this,this paper takes the four-wheel independent driving electric vehicle of the research group as the research object,focusing on the research of four-wheel differential steering performance.The electric vehicle studied in this paper provides the driving torque directly to the wheel by the in-wheel motor.The steering form of the electric vehicle differs from the conventional steering form in that the steering system only has a trapezoidal steering mechanism to restrict the deflection of the inner and outer wheels,and there is no external steering wheel.Or the steering drive motor provides steering power,relying solely on the characteristics that the in-wheel motor can independently control,and relies on the wheel speed difference of the inner and outer wheels to realize steering under the constraint of the trapezoidal steering mechanism to complete the steering action.In order to reveal the motion law of trapezoidal mechanism during differential steering,this paper firstly studies the kinematics and dynamics of the mechanism,establishes its mathematical model,and explains the principle of differential steering from the kinematics of trapezoidal steering mechanism.Then,the vehicle kinematics and dynamics mathematical model is established for the whole vehicle differential steering process.The control variables are determined according to the differential steering process and the governing equation is established.In order to ensure that the wheels are steered as far as possible according to Ackermann steering theory during differential steering,the novel error of steering centering and Ackermann steering instantaneous center during differential steering is the objective function for four-wheel independent drive electric vehicle.The front and rear trapezoidal mechanisms of the prototype were optimized and analyzed.The optimal solution domain was determined by the fitting method.The existence of the optimal solution domain was verified by numerical simulation method.The optimal solution domain was selected and the trapezoidal steering was selected.The length of the rod matching of the physical matching of the mechanism is compared with the results of previous published papers,indicating the correctness of the method.According to the layout form of the electric vehicle,the corresponding control strategy of the whole vehicle was studied.Finally,the test platform was debugged according to the experimental test conditions of the prototype,and the corresponding experimental test plan was developed according to the existing test conditions.The prototype was tested from the aspects of wheel speed performance,vehicle braking performance,straight running performance and differential steering performance.The experimental test site test was carried out,and the differential steering motion law of the four-wheel independent drive electric vehicle in the presence of the body steering mechanism was obtained.This kind of steering mode simplifies the steering mechanism,provides a better solution for the space arrangement of the vehicle,and improves the space utilization of the vehicle.At the same time,this form of steering enriches the types of current steering forms.Therefore,the research on such problems has theoretical value for enriching the steering form of unmanned vehicles and provides engineering practical significance for the control application of unmanned vehicles.