Research of Light Vehicle’s Electronic Stability Programs and Semi-Active Suspension Comprehensive Control

Abstract

With the development of science and technology, active safety of vehicles is receiving more and more attention. Currently, active safety products that have already been developed and applied to vehicles include ABS (Anti- lock Brake System), ASR (Acceleration Slip Regulation), TCS (Traction Control System), and ESP (Electronic Stability Program), etc. The application of semi-active suspense can control changes of vehicle's gestures while turning and braking, and also achieve good frequency response both in cross pendulum and side pour. If the ESP and semi-active suspension can be combined during the process of design, it can not only better improve vehicles' operation stability and comfort of riding, but also reduce the decline of dynamic performance caused by the excessive participation of ESP in vehicles. This paper will analyze the coupling relations between ESP as well as semi-active suspension and the vehicles' yaw control and gesture control during the process of turning in detail, propose ESP-SAS comprehensive control method based on linear assignment weights, and establish simulation model of integrated control unit. When the vehicle is driving, if the vehicle's driving path is inconsistent with the driver's desired track, the ESP system will begin to work and change the vehicle's movement intervention of the brake pressure or adjusting engine torque. If the actual motion of the car at the radius of the curve radius is less than the driver's desired trajectory, namely, car over steer characteristics, ESP systems will be long queues at the front of the car and exert a braking force. One hand brake on car produces a roll aligning torque; on the other hand brake force increase will make the wheel lateral force decrease, and thus produces a roll aligning torque. In the presence of both yaw aligning torques, the car will be back to the driver's desired path. When cars are understeering, ESP has two intervention methods. The first is to apply a braking force at the rear inner wheel in the car, making the car a yaw movement increased, and make the car return the driver's desired track; the other method is to reduce the engine output torque, the driving force will also be reduced accordingly, and the vehicle decelerates. This is bound to cause axle load transfer. The normal force in the front axis will be increased, the normal force in the rear axis will be decreased; and the yawing force in the corresponding front axis will be increased, and the yawing force in the rear axle will be reduced. As a result, the yawing motion of vehicle is increased, making the actual motion state of vehicle get closer to the driver's desired value, and improve the directional stability and active safety of vehicle