On Yaw Stability Control for Electric Vehicle with In-Wheel Motors
The electric vehicle (EV) is now becoming an important tool to help solve the increasingly severe energy and environmental problems as it has low noise and little emission. As for electric vehicle with in-wheel motors (IEV), it has a simple and compact structure and each of its electric motors could be controlled independently and accurately because the multiple motors are mounted directly within the wheels.
Even though the IEV has some exclusive advantages ordinary EV doesn’t have, there exist some problems to be solved when it comes to yaw stability control of the vehicle. For example, the nonlinear characteristics and various constraints should be well addressed; the controller structure should be simplified; and finally, the constrained optimal control problem should be solved.
The proposed research mainly includes the following four parts.
A. Research on Vehicle Dynamics Modelling
To estimate vehicle sideslip angle, design yaw stability controller and test the performance of the controller, vehicle dynamics should be modelled.
B. Estimation of Sideslip Angle
Considering its important role in yaw stability control and the fact that it can’t be measured directly by sensors, the method to estimate sideslip angle should be studied. Also, the nonlinear characteristics of the IEV may be taken into consideration while estimating sideslip angle. Finally, the method to design a nonlinear observer for sideslip angle estimation could be studied with signals regarding vehicle velocity, acceleration, and yaw rate from multiple sensors.
C. Research on Yaw Stability Control
Due to the advantages in handling nonlinear system and various constraints, the method for yaw stability control with the use of MPC should be studied. Also, while designing the yaw stability controller, constraints regarding output torque, responding speed of the motors and “Friction Ellipse” of the tires and cost function regarding stability, utilization of tire forces and energy efficiency should be taken into consideration.
D. Simulation and Experiment
The yaw stability controller, vehicle dynamics models and co-simulation could be developed and conducted using MATLAB/Simulink and Dymola. Also, the yaw stability controller could be tested on an experimental vehicle, for example the KTH RCV. Then comparison could be made between simulation and experiment to optimize the control system and dynamics model.