Bridge cranes (also known as cranes or overhead cranes) are the main equipment for lifting and transportation in large factories. The crane has a large volume and when they operate at a certain speed on the track, the frequent collision accidents is inevitable, especially the collision between the overhead cranes in same span will cause greater losses to personal safety and equipment safety. In order to solve the collision problem, the reliable collision avoidance system is necessary for cranes. The main crane collision prevention methods at present are mechanical type, infrared photoelectric sensor, laser distance sensor, ultrasound and microwave technology, more details as following:

1.  Mechanical type: The mechanism is simple and the cost is low, but during installation and commissioning, it is not convenient due to the vibration problem of the protruding angle steel. Moreover, the vibration of the angle steel is large, and there are problems with the reliability of the work.

2.  Ultrasound and microwave: The cost of ultrasonic anti-collision devices is relatively low, but the ultrasonic scattering angle is large (>20 °), the positioning accuracy is poor, and is greatly affected by the weather. Open air and rainy days may lead to system malfunction. Microwave systems have complex structures and high costs. Rain, dust, and fog greatly absorb them, resulting in poor reliability

3.  Infrared photoelectric sensor:  Special anti-collision method using diagonal positioning, simple structure, convenient installation, high positioning accuracy, good anti-interference performance, but relatively close detection distance.

4.  Laser ranging sensor:  Multifunctional laser anti-collision device. Through laser ranging, the anti-collision device is characterized by long detection distance, good anti-interference performance, high measurement accuracy, and the ability to set a safe distance at any location. Its simple structure is convenient for production and installation, and is suitable for wide promotion in the field of bridge cranes.