Jian Hua Li

Stability control of 4WD electric vehicle with in-wheel-motors based on sliding mode control

Direct yaw moment control can maintain the vehicle stability in critical situation. For four-wheel independently driven (4WD) electric vehicle with in-wheel motors (IWMs), direct yaw moment control (DYC) can be easily achieved. A fairly accurate calculation of the required yaw moment can improve vehicle stability. A novel sliding mode control (SMC) technique is employed for the motion control so as to track the desired vehicle motion, which is it for different working circumstances compared to the well-used traditional DYC. Through the weighted least square algorithm, the lower controller is used to determine the torque properly allocated to each wheel according to the desired yaw moment. Several actuator constraints are considered in the control strategy. In addition, a nonlinear tire model is utilized to improve the accuracy of tire lateral force estimation. Then, simulations are carried out and the values of vehicle states are compared. The simulation results show that the control system proposed can effectively improve the handling stability of the vehicle.

Research on Vehicle Electronic Stability Control Method

Electronic stability control system (ESC) is one of the advanced active safety technology for modern vehicles. The active yaw-moment control (AYC) is one of the most important parts of ESC to enhance vehicle active safety. The control method with combination of logic threshold and PID method is brought out. The PID parameters are generated by logic threshold method through the controller adjusting parameters. The wheel brake torque to keep vehicle stable is calculated by PD controller. The self-correcting threshold of PD control algorithm has the merit of decreasing calculation processes and increasing computation speed. The results of simulation show that the proposed algorithm can be used to control the vehicle more stably under various conditions.

Study of direct yaw moment control for IEV to improve handling and stability control

Direct yaw moment becomes an external input to in-wheel-motors (IWMs) electric vehicles (IEVs) besides steering angle usually as the only input to traditional vehicles. To improve the handling and stability of IEVs, a good knowledge of the effect brought by direct yaw moment is necessary. First, in this paper, reference model based on 2 DOF bicycle model is built for the control strategy. Second, vehicle model is built, and DYC based on sliding mode algorithm is proposed by using model based control method to evaluate the impact on the vehicle behavior. Then, simulations on different maneuvers are carried out and the values of vehicle states are compared especially in wheel steering angles and axle sideslip angles. Finally, conclusions are given.

Study of Modeling and Simulation on Driving Force Power Steering for Electric Vehicle with In-Wheel-Motor-Drive

The most significant feature of EV with In-Wheel-Motor is that, the torque of each wheel can be controlled independently. [. When EVs turn, controlling torque of steering wheel independently can generate torque difference around the kingpin to reduce the drivers steering force and improve the steering Portability [. At first, the theory and structure of Driving Force Power Steering (DFPS) are discussed and a vehicle dynamic model is built with AMESim software. Based on the control strategy and algorithm a control model is built using Matlab/Simulink. At last, a simulation is performed. The results show that the DFPS system can provide steering power and assist steering efficiently.

Intelligent Velocity Control Strategy for Electric Vehicles

In conventional vehicles, the control of vehicle speed is achieved by changing the engine load through adjusting the acceleration pedal. However, in electric vehicles, this is achieved by controlling the target motor torque obtained from the look-up table in accordance with the position of acceleration pedal. This method is an open-loop control, with which the engine brake cannot be implemented during downhill trips. In this paper, a closed-loop control of vehicle speed for electric vehicles is proposed. The target vehicle speed is set by the acceleration pedal. The controller collects the real vehicle speed, whereas the PID controller, according to the error of the real and target vehicle speed, adjusts the motor torque in real time to realize the closed-loop speed control. Under such controlling, the motor torque can be changed correspondingly with the resistance, thus makes the driving performance of electric vehicles more identical to that of conventional vehicles.

Controll algorithm of combination with logic gate and PID control for vehicle electronic stability control

the electronic stability control system is one of most advanced active safety technology for modern vehicles. It enhances vehicle active safety effectively. The control algorithm of combination with logic gate and PID control is brought out. The PID parameters are produced by logic gate control and the wheel brake torque to keep vehicle stabilization is outputted by PID method. The method possess of the merit of decreasing computation process and increasing computation speed. Simulation results show that the proposed control algorithm can be used to control the vehicle more stably under various conditions.

Design of a Novel Nonlinear Observer to Estimate Sideslip Angle and Tire Forces for Distributed Electric Vehicle

For four-wheel independently driven (4WD) distributed electric vehicle (DEV), vehicle dynamics control systems such as direct yaw moment control (DYC) can be easily achieved. Accurate estimation of vehicle state variables and uncertain parameters can improve the robustness of vehicle dynamics control system. Various sensors are generally equipped to the acquisition of the vehicle dynamics. For both technical and economic reasons, some fundamental vehicle parameters, such as the sideslip angle and tire-road forces, can hardly be obtained through sensors directly. Therefore, this paper presented a state observer to estimate these variables based on Unscented Kalman Filter (UKF). To improve the accuracy of UKF, measurement noise covariance is also self-adaptive regulated. In addition, a nonlinear dynamics tire model is utilized to improve the accuracy of tire lateral force estimation. The simulation and experiment results show that the proposed observer can provide the precision values of the vehicle state.

The Control Strategy of Yaw Moment for Rear Electric Motor Drive Vehicle

With the maturing of in-wheel motor technology, Control on vehicle longitudinal and lateral stability have a rapid development, vehicle with in-wheel motor have also made considerable progress. The paper conducts a study on control strategy of electric vehicle with two in-wheel motors mounted on rear wheels. Yaw moment adopt target following algorithm based on two degrees of model of monorail and study the allocation of torque on two driving wheels. The study indicates that ESP control strategy in which yaw moment of left and right wheel is different and the way of allocating torque based on utilization adhesion can improve vehicle handling ability.

The Timing Control Research for the Motor in Wheel

For the permanent magnet synchronous motor used in electric vehicle wheel, in order to obtain high torque at low speed, a lot of pole pairs are designed in the structure. So the electrical angle will rotate too fast, and the commutation delay will appear apparently at high speed. The commutation process of permanent magnet synchronous motor is analyzed and the timing control according to rotate speed is deduced. A motor simulation model is built to verify the control strategy. The result shows that the strategy can effectively improve high speed performance of motor.

The Variable PWM Frequency Control Research for the Motor in Wheel

According to the characteristics that the motor in wheel is insensitivity of torque ripple, the impact of reducing PWM frequency on motor control is studied, and the phenomenon that the PWM frequency is limited by the lag angle of motor commutation. Then a variable PWM frequency control strategy according to rotate speed is proposed. Based on Simulink, the motor control model is built and the control strategy is verified by simulation. The result shows that the variable PWM frequency control significantly improves the performance of motor at low speed, with little toque ripple increased.