Research On Driving Force Distribution And Anti-slip Control Of Four-wheel Drive Electric Vehicle

As the main platform for future traffic travel,electric vehicles are receiving more and more attention worldwide,and their zero-emission characteristics are in line with the general trend of green cleanliness of energy use.Different from the traditional centralized-drive electric vehicle,with the unique configuration distributed drive electric vehicle not only has the characteristics of precise controllable torque and fast response of the electric vehicle,but also has more control freedom and can achieve torque control at single round level.These previous characteristics have made the dynamic control become a research hotspot in recent years.This paper takes a in-wheel motor four-wheel drive electric vehicle as the research object,makes full use of its advantages in driving control,and studies the technology of the driving force distribution and driving anti-slip,exploring more possibilities based on traditional dynamic control.First of all,this paper expounds development of distributed drive electric vehicles and the current research situation of the driving force control.According to the configuration characteristics of the in-wheel motor four-wheel drive electric vehicle,the dynamic model architecture was determined.Based on the traditional car model,the dynamic simulation of the vehicle body model matched with the actual vehicle parameter was completed in the CarSim environment and the driver model were built under the Simulink to establish the foundation for the subsequent simulation and verification of stratedy.Secondly,this paper studies the driving force distribution strategy under normal conditions.In this paper,the improvement of steering maneuverability is the main content of driving force distribution.And The driving force distribution strategy aiming at improving steady-state and transient-state response of the yaw rate is determined.The front-rear axle distribution of the driving force mainly affects the steady-state response of the yaw rate,so it is studied as the m ain distribution method to improve the steady-state response of the yaw rate.The yaw rate transient response process is regarded as a second-order system and the natural frequency and damping ratio are adjusted to design the ideal target.And the direct yaw m oment is formed by the differential torque of the left and right motors to improve dynamic performance of the yaw rate.Then,this paper studies the anti-slip strategy.The key to influencing the ef fect of driving anti-slip control is th e identification of the optimal slip ratio of the road surface.This paper uses the relationship between the optimal slip ratio and the maximum utilization of the adhesion coef ficient to estim ate the op timal slip ratio and uses the fuzzy logic inference to correct it.Based on this,PI control and feedforward compensation were carried out.At the same time,PI control parameters are self-tuned to adapt to different types of road surface with fuzzy control principle.Since the s lippage of the wheels af fects the dynamic performance and stability of the en tire vehicle,the drive torque according to different slip conditions is compensated for in real tim e.Finally,this paper proposes a layered dynam ics control architecture and realizes th e integrated control of driving force distribution and driving anti-slip.The excessively large yaw moments decided under the low adhesion road surface can easily cause the car to slide.Then based on th e friction ellipse p rinciple the distribution of yaw moment is optimized considering the tire attachment ability.Finally,this paper carried out off-line simulation and actual vehicle test to verify the effectiveness of the driving force distributi on and anti-slip strategy.Off-line simulation verified the good control effect of the proposed control strategy.Because of the limitation of test conditions,the actual vehicl e test is m ainly used to ve rify the distribution of the differential torque of the left and right motors.And the test results prove that the differential torque improving the steering dynamic response has a very good practical application effect.