Consideration of Effective Chassis Control in Electric Vehicle 2018-01-5035

In this study, we focus on “camber angle control” and “derivative steering assistance” using “steer-by-wire” as maneuverability and stability improvement techniques that are appropriate for the electric vehicle (EV) era. Movements that produce a negative camber angle generate camber thrust, and vehicle motion performance improvements extend from the fact that the tire side force is increased by the camber thrust effect. In our experimental vehicle, a proportional steering angle system was used to create negative camber angle control via an electromagnetic actuator that allowed us to confirm improvements to both the effectiveness and stability of steering control in restricted cornering areas. More specifically, we determined that it is possible to improve critical cornering performance by executing ground negative camber angle control in proportion to the steering angle. Steer-by-wire refers to an electrical steering technique that allows the steering angle of the entire vehicle to be controlled independently of the front wheel steering angle, thereby providing a high level of steering system control freedom. When derivative steering assistance control is applied, the phase of the front wheel steering angle advances faster in proportion to the steering angle velocity change than would normally occur based on the driver’s steering actions, which can improve ease of operation and maneuvering stability. In an experimental vehicle equipped with derivative steering assistance via a steer-by-wire system, the steer effectiveness was improved because the phase of the front wheel steering angle advanced due to the derivative steering assist, thereby improving the vehicle responsiveness.