Piezoelectric ceramics are widely used in the automobiles. A simple piezo-ceramic actuator is installed in the brake piston of the car to apply a "jitter" frequency to the support plate of the internal brake shackle, effectively suppressing the vibrations that generate sharp noise, thereby enabling temperature and humidity changes and braking systems.Piezoelectric ceramics convert positive and negative piezoelectric effects between electric energy and mechanical energy. When the electric signal is applied to piezoelectric ceramics, which generated mechanical vibration and emitted ultrasonic waves. When ultrasonic waves encounter obstacles during air transmission,immediately they are reflected back, when is applied to piezoelectric ceramics, there will be an electrical signal output, and then through the data processing of difference ranging,to calculate the distance between the vehicle and the obstacle and alarm when dangerous collision. It can accurately detect the tiny obstacles in the tail of the car and the blind spot of the driver's perspective, and it is quite practical.