The electric vehicle (EV) is the most exciting object to apply "advanced motion control" technique. As an EV is driven by electric motors, it has the following three remarkable advantages: 1) motor torque generation is fast and accurate; 2) motors can be installed in two or four wheels; and 3) motor torque can be known precisely. These advantages enable us to easily realize: 1) high performance antilock braking system and traction control system with minor feedback control at each wheel; 2) chassis motion control like direct yaw control; and 3) estimation of road surface condition. "UOT Electric March II" is our novel experimental EV with four in-wheel motors. This EV is made for intensive study of advanced motion control of an EV.

Future vehicle driven by electricity and Control-research on four-wheel-motored "UOT electric march II"

We study methods of motion control for an electric vehicle (EV) with four independently driven in-wheel motors. First, we propose and simulate a novel robust dynamic yaw-moment control (DYC). DYC is a vehicle attitude control method that generates yaw from torque differences between the right and left wheels. The results of simulations, however, identify a problem with instability on slippery, low /spl mu/ roads. To solve this problem, a new skid detection method is proposed that will be a part of traction control system (TCS) for each drive wheel. The experimental results show that this method can detect a skidding wheel, without any information on chassis velocity. Therefore, this method will be of great help during cornering or braking in a TCS. These methods will be integrated and tested in our new experimental EV.

Motion control in an electric vehicle with four independently driven in-wheel motors

The most distinct advantage of the electric vehicle is its quick and precise torque generation. However, most electric vehicles developed to date have not yet utilized this feature. In this paper, two novel traction control techniques of an electric vehicle using this advantage are proposed. One is the model-following control and the other is the optimal slip ratio control. The basic effectiveness of the proposed methods is demonstrated by real experiments using the DC-motor-driven test vehicle "UOT (University of Tokyo) Electric March".

Traction control of electric vehicle: basic experimental results using the test EV "UOT electric march"

This study proposes a control system to improve vehicle handling and stability under severe driving conditions by actively controlling the front steering angle and the distribution of braking forces on four tires. With the application of a model-matching control technique, this proposed control system makes the performance of the actual vehicle model follow that of an ideal vehicle model with consideration of nonlinearity of tire characteristics. Finally, this paper investigates the effectiveness of control system during the following conditions: braked cornering, lane change and side wind disturbance.

Study on integrated control of active front steer angle and direct yaw moment

SUMMARY In this paper chassis controls for vehicle handling and active safety have been reviewed. In particular, we have observed the effectiveness and limit of 4WS and DYC. It is pointed out that DYC is more effective in vehicle motion with larger side-slip and/or higher lateral acceleration and taking the nonlinearity of tire and vehicle dynamics into consideration is essential for introducing the control law for the chassis controls and their integration/coordination. We wish to emphasize that there is a need to further propose control laws based on deeper observation and understanding on the tire and vehicle dynamics.

Advanced chassis control systems for vehicle handling and active safety

Enhancing the performance of vehicles under some critical driving situations where the tires may work within strong nonlinear areas has been a difficult task assigned to automotive researchers for decades. Although some control systems have been proposed, there is still much room left for improvement. This study introduces an integrated control system providing high performance within tires' strong nonlinear areas with an adaptivity to the changing road and other conditions, by optimally controlling the front and rear steering angles and the yaw moment, based on the information of system parameters identification. The proposed system is verified by computer simulations to be effective in both enhancing the dynamic stability margin and reducing the driver's steering burden.

Integrated control of four-wheel-steer and yaw moment to improve dynamic stability margin

This study discusses a vehicle path tracking strategy using a virtual point ahead of the vehicle to trace the desired path. Although the vehicle center of gravity can also be employed for the tracking, it is impossible to design the yaw control independently from the controlled lateral motion. By contrast, the yaw motion, as well as the lateral motion, can be controlled to obtain its own desired performance when the virtual point is used for the tracking, although this applies with certain reservations. Additionally, employing the virtual point also secures good robust stability and disturbance suppression performance of the control system.

Study on automatic path tracking using virtual point regulator

This paper proposes a new method to improve the handling and stability of electric vehicles by controlling the yaw moment generated by driving/braking forces. Yaw moment is controlled by the feedforward compensation of steering angle (and steering velocity) to minimize the side slip angle at the vehicle center of gravity. To realize this kind of yaw moment control, the right and left driving/braking forces should be controlled independently. Theoretical analysis and computer simulation are carried out to show the effectiveness of this control system. The results show that the handling and stability are improved significantly compared to those of the conventional two-wheel-steering vehicles, and that a 4WS-equivalent vehicle performance is obtained. This control effectiveness is also verified by experimental results using a downsized vehicle model on a moving belt tester.

https://www.jstage.jst.go.jp/article/ieejias1987/116/3/116_3_279/_pdf

Motion Control of Electric Vehicles by Distribution Control of Traction Forces

This paper presents a new control method by an adaptive front steering system. Two types of model reference adaptive steering systems are proposed in this paper : one type puts emphasis on yaw rate of the vehicle which a driver perceives dominantly under ordinary driving conditions : and another one puts emphasis on lateral acceleration of the vehicle which a driver perceives dominantly under critical driving conditions, such as obstacle avoidance. The parameters of the vehicle are treated as unknown and are identified by the least square method with a time variant forgeting factor. The control method used in this paper is a pole assignment type adaptive self-tuning control method. Simulation results show that the running safety is improved significantly and that the driver burden is decreased under critical driving conditions.

Vehicle Motion Control by Adaptive Front Steering System.

This paper proposes a new method to improve the handling and stability of vehicles by controlling the yaw moment generated by driving/braking forces. Yaw moment is controlled by the feedforward compensation of steering angle (and steering velocity) to minimize the side slip angle at the vehicle center of gravity. To realize this kind of yaw moment control, the right and left driving/braking forces should be controlled independently. Theoretical analysis and computer simulation are carried out to show the effectiveness of this control system. The results show that the handling and stability are improved significantly compared to those of the conventional two-wheel-steering vehicles, and that a 4WS-equivalent vehicle performance is obtained. This control effectiveness is also verified by experimental results using a downsized vehicle model on a moving belt tester.

Yuqing Wang

Papers

Integrated control of four-wheel-steer and yaw moment to improve dynamic stability margin

Study on automatic path tracking using virtual point regulator

Motion Control of Electric Vehicles by Distribution Control of Traction Forces

Vehicle Motion Control by Adaptive Front Steering System.

Motion Control of Front-Wheel-Steering Vehicles by Yaw Moment Compensation. Comparison with 4WS Performance.