Active Yaw Control

Basic Description

Active Yaw Control is a dynamic stability control system that sustains longitudinal acceleration and improves lateral stability by controlling torque-bias between the rear wheels. Active yaw control increases cornering and traction performance using a computer controlled rear differential. The torque-bias is controlled to transfer the most amount of torque to the wheel with the highest amount of traction potential. The torque difference between the rear wheels generates a yawing moment in the proper direction and corrects the yaw-dynamics of the vehicle in motion. The result is a stable vehicle with improved handling performance and increased cornering capability.

The torque variation is controlled by the ECU and is applied to the wheels through several mechanical components in the differential. The three major components in the computer controlled differential are the clutch mechanisms, the main differential, and the speed increasing/reducing gear train. The clutches are utilized to control the amount of torque being transferred through the increasing/decreasing gear train, and determine the amount of torque applied to each of the two wheels. The torque-bias is a function of clutch pressure and the amount of clutch pressure is determined by the processor in the ECU and actuated using hydraulic or electromagnetic components.

The active yaw control strategy is based on the relative wheel speeds. The optimum wheel speed difference is determined by the ECU in order to maintain the steering wheel position.

If a vehicle with active yaw control is entering a corner and understeer occurs, torque from the inside wheel will be transferred to the outside wheel. This torque difference will produce a yawing motion in the direction of the steer and reduce understeer. The wheel speed difference is then sustained until a new path of curvature or dynamic condition is introduced. An inverse torque transfer can also be delivered to the wheels to reduce oversteer and consequently keep the vehicle on its intended path of curvature.

Sensors

Wheel speed, accelerometer, steering wheelposition, throttle position, yaw rate

Actuators

Hydraulic modulator, electromagnetic solenoids (for clutch actuation)

Data Communications

Control Unit Communication: Typically Control Area Network (CAN) Bus System

Manufacturers

Mitsubishi Motors

For More Information

[1] Development of Super Active Yaw Control, Mitsubishi Motors

[2] All Wheel Control, Mitsubishi Motors

[3] Dynamic Modeling of Torque-Biasing Devices for Vehicle Yaw Control, SAE Technical Paper

[4] What is Active Yaw Control, LancerRegister.com