Apparatus and method for controlling vehicle rear wheel steering

An apparatus for controlling rear wheel steering of a vehicle, the apparatus comprising:

• a sensor to detect a front wheel steering angle, a current yaw rate, and a vehicle speed;
• a rear-wheel drive module configured to steer rear wheels of the vehicle based on a rear wheel steering angle;
• and
• a processor connected to the sensor and to control the rear-wheel drive module,
• wherein the processor
• receives the front wheel steering angle, current yaw rate, and vehicle speed from the sensor,
• calculates a steering angle acceleration based on the front wheel steering angle,
• calculates a target yaw rate based on the steering angle acceleration, front wheel steering angle, and vehicle speed,
• calculates the rear wheel steering angle to adjust the current yaw rate to the target yaw rate, and
• controls the rear-wheel drive module based on the rear wheel steering angle to control the rear wheel steering of the vehicle;
• wherein the processor varies a rear wheel gear ratio based on the steering angle acceleration, changes the rear wheel gear ratio to an opposite direction when the steering angle acceleration is greater than or equal to a set value, and changes the rear wheel gear ratio to neutral or to a same direction when the steering angle acceleration is not greater than or equal to the set value.

A method for controlling vehicle rear wheel steering of a vehicle, the method comprising:

• calculating, by a processor, a steering angle acceleration based on a current steering angle of the vehicle;
• calculating, by the processor, a target yaw rate based on the steering angle acceleration, a front wheel steering angle, and a vehicle speed;
• and
• performing, by the processor, rear wheel steering control such that a yaw rate of the vehicle converges to the target yaw rate;
• wherein, in calculating the target yaw rate, the processor varies a gear ratio to have oversteer gradient characteristics when the steering angle acceleration is greater than or equal to a set value and varies the gear ratio to have understeer gradient characteristics when the steering angle acceleration is below the set value, thereby calculating the target yaw rate.