An electronic stability control (ESC) algorithm is proposed for a four in-wheel motor independent-drive electric vehicle (4MIDEV) utilizing motor driving and regenerative braking torque distribution control to improve vehicle stability. A stability judgment controller, an upper level controller, and a torque distribution algorithm are designed for the ESC system. The stability judgment controller is designed to generate the desired yaw rate and sideslip angle for vehicle stability, and the control mode, which is normal driving mode or ESC mode, is set according to the driver inputs and measurement signal inputs. The upper level controller consists of a speed tracking controller, a yaw moment controller, and four wheel-slip controllers to calculate the desired value of traction force, the desired value of yaw moment, and the four respective net torque inputs of the four in-wheel motors. The torque distribution algorithm is designed to generate each motor driving torque or regenerative braking torque input for each wheel. An average torque distribution strategy, a tire-dynamic-load-based torque distribution strategy, and a minimum-objective-function-based optimal torque distribution strategy are used separately in the torque distribution algorithm to control the motor driving torque or regenerative braking torque for vehicle stability enhancement. The proposed ESC algorithm was implemented and evaluated in a CarSim vehicle model and a MATLAB/Simulink control model. The three proposed torque distribution strategies can be used to regulate the vehicle to perform the following tasks: “single lane change,” “double lane change,” and “snake lane change.” The simulation studies show that the yaw rate error root mean square [RMS $(\gamma-\gamma_\mathrm{-des})$ ] decreased, on average, by 75 percent using the proposed optimal torque distribution algorithm compared with that without using stability control.

Electronic Stability Control Based on Motor Driving and Braking Torque Distribution for a Four In-Wheel Motor Drive Electric Vehicle

MPC-based yaw stability control in in-wheel-motored EV via active front steering and motor torque distribution

In this paper, an optimal torque distribution approach is proposed for electric vehicle equipped with four independent wheel motors to improve vehicle handling and stability performance. A novel objective function is formulated which works in a multifunctional way by considering the interference among different performance indices: forces and moment errors at the centre of gravity of the vehicle, actuator control efforts and tyre workload usage. To adapt different driving conditions, a weighting factors tuning scheme is designed to adjust the relative weight of each performance in the objective function. The effectiveness of the proposed optimal torque distribution is evaluated by simulations with CarSim and Matlab/Simulink. The simulation results under different driving scenarios indicate that the proposed control strategy can effectively improve the vehicle handling and stability even in slippery road conditions.

An optimal torque distribution control strategy for four-independent wheel drive electric vehicles

Vibration mitigation for in-wheel switched reluctance motor driven electric vehicle with dynamic vibration absorbing structures

The longitudinal collision avoidance controller can avoid or mitigate vehicle collision accidents effectively via auto brake, and it is one of the key technologies of autonomous vehicles. Moreover, the vehicle lateral stability is very crucial in emergency scenarios. Due to complex traffic conditions and various road frictions, emergency brake may cause a vehicle to lose its lateral stability. Therefore, this paper proposes a lateral-stability-coordinated collision avoidance control system (LSCACS) based on the model predictive control (MPC). First, the proposed LSCACS decides which control mode to be implemented based on vehicle dynamics states, including a normal driving mode, a full auto brake mode, and a brake and stability mode. The MPC is used in the upper controller to calculate the desired deceleration and additional yaw moment. The lower controller calculates the desired tire forces of four wheels and realizes them by certain wheel cylinder hydraulic pressures. The LSCACS is validated by hardware-in-the-loop (HIL) tests, and the results show LSCACS’s effectiveness and great performance of the collision avoidance and lateral stability.

Longitudinal Collision Avoidance and Lateral Stability Adaptive Control System Based on MPC of Autonomous Vehicles

This paper focuses on the vehicle dynamic control system for a four in-wheel motor drive electric vehicle, aiming at improving vehicle stability under critical driving conditions. The vehicle dynamics controller is composed of three modules, i.e. motion following control, control allocation and vehicle state estimation. Considering the strong nonlinearity of the tyres under critical driving conditions, the yaw motion of the vehicle is regulated by gain scheduling control based on the linear quadratic regulator theory. The feed-forward and feedback gains of the controller are updated in real-time by online estimation of the tyre cornering stiffness, so as to ensure the control robustness against environmental disturbances as well as parameter uncertainty. The control allocation module allocates the calculated generalised force requirements to each in-wheel motor based on quadratic programming theory while taking the tyre longitudinal/lateral force coupling characteristic into consideration. Simulations under a variety of driving conditions are carried out to verify the control algorithm. Simulation results indicate that the proposed vehicle stability controller can effectively stabilise the vehicle motion under critical driving conditions.

Vehicle dynamics control of four in-wheel motor drive electric vehicle using gain scheduling based on tyre cornering stiffness estimation

In this paper, a motion follow controller for a 4-wheel-drive electric vehicle based on one track non-linear vehicle model and variable structure control (VSC) theory was designed. Combining the controller with optimal control allocation algorithm which takes into account of longitudinal/lateral force couple characteristic for tire under critical situation, we designed the vehicle stability control system. By using veDYNA, the double lane change simulation was carried out to verify the validity of control method. The results of simulation show the proposed control method could stabilize vehicle well under critical situation. The reference model plays an important role at stabilizing vehicle attitude, but inevitably alters the steering characteristic, which brings certain conservative. Actual control allocation could match the general requirement well by taking into account of tire force characteristic.

Nonlinear vehicle dynamics control for EV with 4 in-wheel motors

Exploiting the structural merit that electric motors can be controlled precisely in speed und torque, this paper investigates the use of Torque Vectoring Control (TVC) for improving handling of electric vehicles. The strategy consists of two control levels. The upper level controller layer achieves reference yaw rate tracking, by using the 2-DOF planar bicycle model with a linear tire model to calculate the desired yaw rate. Then with sliding mode control law the desired yaw moment is determined. The lower control level determines control inputs for four driving motors by means of optimum traction distribution. Simulations are carried out by using the co-simulation of vehicle dynamics software CarSim and Simulink to verify the effectiveness of this control system and the effects of parameter variations (friction coefficient and throttle).

Torque Vectoring Control for Handling Improvement of 4WD EV

The torque vibration derived from in-wheel-motor transmitted to body frame through suspension system without the absorption of mechanical transmission parts, then excited every body panel to shape the vehicle interior noise, which influenced the quality of the vehicle NVH. This paper aims to build an accurate suspension system simulation model to analyze the influence of suspension parts parameters to system vibration transmission property. Basis on a novel empirical model of rubber bushing, a multi-rigid suspension model and a multi-flexible suspension model had been established respectively. The vibration characteristics of two models were simulated, furthermore the swept-sine exciting vertical force signal on wheel contact point were input on the simulation models to find the difference between rigid and flexible model. The simulation results show that: the multi-flexible model can reflect the vibration characteristics of the suspension system more accurately in the high frequency range and so is it more applicable to the simulation analysis of vibration characteristics of in-wheel-motor electric vehicle suspension system.

Analysis of Vibration Characteristics Basing on a Multi-Rigid Suspension Model and a Multi-Flexible Suspension Model

Wheel hub bearings are weak parts in wheel driving system because of its bad condition of loads. This paper has selected two typical extreme working conditions for vehicle, namely braking with turning and driving with turning, and analyzed loads of wheel hub bearings. The design parameters of wheel hub bearings are analyzed separately, with the purpose of finding the key parameters in them, which influenced the force of bearing, and finally these important parameters for structural design have been optimized, the force of wheel hub bearings has been decreased by 45%.

Lu Xiong

Papers

Vehicle dynamics control of four in-wheel motor drive electric vehicle using gain scheduling based on tyre cornering stiffness estimation

Nonlinear vehicle dynamics control for EV with 4 in-wheel motors

Torque Vectoring Control for Handling Improvement of 4WD EV

Analysis of Vibration Characteristics Basing on a Multi-Rigid Suspension Model and a Multi-Flexible Suspension Model

Load Analysis of Wheel Hub Bearing in Wheel Driving System with Exterior Rotor Motor