Vehicle steering system, vehicle including the same and method for turning wheel of vehicle

A vehicle steering system comprising:

• a steering wheel;
• steering angle detection means for detecting a steering angle of the steering wheel;
• steering angular speed calculation means for calculating a steering angular speed of the steering wheel;
• vehicle speed detection means for detecting a vehicle speed;
• target rudder angle finding means for finding a target rudder angle which is based on the steering angle, the steering angular speed and the vehicle speed;
• and
• actuator means for turning at least one wheel of the vehicle in accordance with the target rudder angle,
• wherein the target rudder angle is a sum of a proportional term in proportion to the steering angle and a differential term in proportion to the steering angular speed, and
• wherein modifying means modifies a value of the differential term smaller when the steering angular speed is negative comparing to a value of the differential term with a positive angular speed.

A vehicle comprising:

• a wheel;
• a steering wheel;
• a steering angle detector for detecting a steering angle of the steering wheel;
• a steering angular speed calculator for calculating a steering angular speed of the steering wheel;
• a vehicle speed detector for detecting a vehicle speed;
• a target rudder angle finding device for finding a target rudder angle which is based on the steering angle, the steering angular speed, and the vehicle speed;
• and
• an actuator for turning at least one wheel of the vehicle in accordance with the target rudder angle;
• wherein the target rudder angle is a sum of a proportional term in proportion to the steering angle and a differential term in proportion to the steering angular speed, and
• wherein a modifying device modifies the differential term smaller when the steering angular speed is negative comparing to a value of the differential term with a positive angular speed.

A method for turning at least one wheel of a vehicle comprising:

• detecting a steering angle of a steering wheel of the vehicle;
• calculating a steering angular speed of the steering wheel;
• detecting a vehicle speed;
• finding a target rudder angle which is based on the steering angle, the steering angular speed, and the vehicle speed;
• modifying a value of the differential term smaller when the steering angular speed is negative comparing to a value of the differential term with positive angular speed;
• and
• turning at least one wheel of the vehicle in accordance with the target rudder angle,
• wherein the target rudder angle is a sum of a proportional term in proportion to the steering angle and a differential term in proportion to the steering angular speed.