Research On Four-wheel Independent Drive Electric Vehicle Handing Stability Control

Four wheel electric vehicle mass is light, mechanical transmission loss is low, the driving characteristics of flexibility, has gradually become one of the hot research topics.At present, research on basic control of four wheel electric vehicle has been more and more perfect, but the study on handling stability of less, especially changes in road conditions and vehicle stability control in interference conditions rarely involved, so the handling stability has gradually become one of the four wheel vehicle wheel electric vehicle key problems. This paper is mainly to solve the four wheel electric vehicle in the change of vehicle parameters and operating conditions, as well as the vehicle in case of interference control stability problem. Innovations of this paper are as follows:1. In order to solve the problem of the vehicle parameters and friction coefficient in the case of unknown control stability problem, this paper proposes a control strategy of yaw rate and sideslip angle based on adaptive control. Based on the analysis of the yaw rate and sideslip angle drive electric vehicle handling stability for the four round. In order to make the vehicle to adapt to different road friction coefficient, a linear model of four wheel electric vehicle yaw rate adaptive controller is designed based on the vehicle itself; in view of the drift of parameters design of side slip angle, yaw rate based on the dynamic adjustment strategy, realizes the control of yaw rate and side slip angle of the four round wheel electric vehicle changes under different conditions and its parameters,improves the vehicle handling and stability.2. To first basis points, to further study the vehicle accelerating and safety. On the one hand, taking into account the four wheel electric vehicle handling and stability performance and speed, this paper proposes an improved vector control strategy based on the variable integral. The algorithm parameter is easy to control, fast response speed,speed curve is rising fast and no overshoot, driving electric vehicle dynamic performance of the system meet the requirements, but also meet the requirements of electric vehicle acceleration performance. On the other hand, taking into account the four wheel electric vehicle handling stability and safety of the electric car, ramp starts as an example, this paper describes the design of a long Berg hill start strategy based on state observer, the vehicle before the Dragon Berg state observer for the ramp angle estimation, in order to ensure the vehicle starting and the requirement of the maximumoutput torque to meet the impact of the initial.3. The four wheels four wheel electric vehicle with independent drive mode, so the torque distribution problem, will ensure that the total torque of vehicle handling stability through reasonable distribution to four wheels. While the average distribution of the two in parallel in different conditions and the effect of fault situation is not ideal, so this paper designs a kind of vehicle stability as the goal of the optimal torque distribution strategy. Firstly, according to the motor fault control strategy, determined to participate in the tire force; and then the driver’s desired torque, driver’s desired yaw torque and wheel lateral force of gravity as constraint condition; finally the strategy according to the motion state of the electric vehicle, the weight coefficient to determine the wheel longitudinal tire force and lateral tire forces, combined with constraints four wheel electric vehicles to electric vehicles that the optimal torque distribution strategy of vehicle stability control, provide the expected value for in wheel motor drive system.4. Considering the interference of four wheel electric vehicle handling stability,this article from the following three aspects of the disturbance was studied as an example. First, considering the random network delay will result in the vehicle control deviation, and even to control the divergence problem, in order to guarantee the network delay under the condition of random interference control stability, the random delay interference in vehicle network design a control strategy of random disturbance robust control based on H. The main research work of this strategy is: use Taylor method to establish the vehicle model with random time delay, robust controller design of H, using the LMI optimization design method, to calculate control law. To ensure the network with random disturbance, the car still can be in accordance with the requirements of the normal completion of specified conditions, improve the handling and stability of four wheel electric vehicle. Second, taking into account the electric drive system of the vehicle will cause harmonic output torque and rotational speed pulse problem, in order to guarantee the harmonic interference conditions of handling and stability, this paper proposes a harmonic suppression method based on low pass filter. The strategy of using harmonic injection method for harmonic suppression, the main influence on the motor five harmonic and seven harmonic respectively low-pass filter design, the control voltage is calculated on the control voltage is superposed to the fundamental wave, so as to achieve the suppression of the five and seven harmonics of the objective. Third,considering the effect of disturbance on vehicle handling stability, according to theelectric load torque disturbance problem in the design of a controller based on the inverse torque disturbance. This strategy will cause the changes of parameters and external interference model of the actual object and the nominal model output differences were equivalent to the control input, and the equivalent amount of interference, is introduced in the control of the compensation, can suppress the disturbance completely. Three kinds of interference suppression algorithm is designed to ensure the normal operation of the electric vehicle in the interference condition,improve the handling and stability.Based on the above research work, this paper designed four wheel electric vehicle handling and stability control system, and combined with simulation in Matlab/Simulink, the handling stability control system is designed in this paper can ensure the vehicle handling and stability are good in different conditions of traffic and interference conditions.