ESP system is actually an extension of ABS (Anti-lock Braking System) and ASR (Anti-skid Driving Wheel System), which can be said to be the highest form of anti-skid device for automobiles at present. It is mainly composed of control assembly, steering sensor (monitoring the steering angle of the steering wheel), wheel sensor (monitoring the rotating speed of each wheel), sideslip sensor (monitoring the rotation state of the car body around the longitudinal axis), lateral acceleration sensor (monitoring the centrifugal force when the car turns) and so on. The control unit judges the driving state of the vehicle through the signals of these sensors, and then sends out control instructions.