Yaw Stability Control Of In-wheel Motor Vehicle

The control of vehicle yaw stability is a critical part of the vehicle active safety technique. It can help to avoid understeering and oversteering in steering course and improve the safety during driving process. Different with the traditional ones, in-wheel-motor driving vehicles have the features that driving torque and braking torque of the four wheels are continuously adjustable. This makes the yaw stability control strategy and method confront technological revolution, creating numerous control problems. Given this, this paper studies on the yaw stability control of in-wheel-motor driving vehicle and provide a new control method.First, this paper studies on the dynamic modeling of in-wheel motor vehicle,according to which the vehicle dynamic characteristics is analyzed and yaw stability controller is desigend. The vehicle sideslip angle and yaw rate, as they can express the vehicle yaw motion dynamics feature, are regarded as the model state variables. Ingnoring the influence of wind resistance and wheel rolling resistance, a 2-degree-of-freedom vehicle dynamics model including lateral and yaw motion is founded. Comparing with the vehicle model of ve DYNA, a highprecision vehicle dynamics software, it is verified that the founded model is relatively accurate to characterize vehicle yaw dynamics.Then, to design the yaw stability controller for in-wheel motor vehicle. In consideration of the hierarchy control strategy, a two-layer structure controller is designed. The upper controller is to make the sideslip angle and yaw rate follow the desired state. The additional steering angle and direct yaw torque are the control input. A model predictive control with terminal constraints method is presented to design the vehicle yaw stability controller. The lower controller is responsible for distrbuting the direct yaw torque among the wheels,implementing the vehicle yaw stability control.Last, based on the high-precision vehicle dynamics software—ve DYNA,simulations with various conditions is conducted. The simulation results show that the controller this paper proposed can ensure the vehicle yaw stability in steering process.