No abstract

Adopting in-wheel motor drive can improve vehicle dynamics control functions, which is the most ideal drive mode of unmanned ground vehicle. However, with the increase of the heavy unspring-mass vibration energy while the vehicle running on uneven road, the ride comfort will be seriously deteriorated. To solve the problem and save energy, the ride comfort control based on regenerative suspensions is adopted. By analyzing the vibration performance, the adverse effects of the vehicle equipped in-wheel motors with passive suspensions are revealed. Then, the dynamics model of the regenerative suspension is built. Based on the suspension power recovery, the multi-state optimal control strategy for improving the ride comfort is designed. Finally, comparing the simulation results of regenerative suspensions with the test results of passive suspensions, when the vehicle mass ratio decreases from 8:1 to 4:1, the body acceleration and the root mean square value of tire dynamic load increase by 28.1% and 31.6%, correspondingly. With the control method, the body acceleration is decreased by 23% and reaches the level of conventional vehicles. Furthermore, part of the vehicle vibration energy can be recovered and the vehicle driving range can be extended.

To solve the security control problem of two in-wheel motors front-drive electric vehicles with single motor failure, an electromechanical composite brake control method based on the normal working motor and the electromechanical brake systems is proposed. First, the electromechanical brake system model is established and the brake characteristics is verified by bench test. Then, based on the electric vehicle model and the in-wheel motors model that has been verified by a vehicle test, the instability mechanism of the vehicle with single motor failure is analyzed. Next, taking the yaw rate and the side-slip angle as the state variables, an in-loop controller based on model predictive control theory is designed; taking the yaw angle as the state variable, an outer-loop controller based on fuzzy proportional integral derivative control theory is designed. Finally, the expected stability control is achieved by the distribution of four-wheel brake torque. According to the research, compared with the simple drive motor torque following and motor regenerative brake control, the electromechanical composite brake control can enable the vehicle to offset the effects of instability torque more quickly, so that the vehicle can follow the expected motion trajectory basically and improve the vehicle stability.