An indoor gantry crane is a bridge-type crane in which the bridge is supported on the ground track by legs on both sides. Structurally, it consists of a mast, a trolley operating mechanism, a lifting trolley and electrical parts. Some gantry cranes only have outriggers on one side, and the other side is supported on the factory building or trestle, which is called a semi-gantry crane. The gantry crane is composed of the upper bridge frame (including main beam and end beam), outriggers, lower beam and other parts. In order to expand the operating range of the crane, the main beam can extend beyond the outriggers to one or both sides to form a cantilever. A lifting trolley with a boom can also be used to expand the crane's operating range through the pitching and rotation of the boom. Gantry cranes can be classified according to the structure of the door frame, the form of the main beam, the structure of the main beam, and the form of use.

Gantry cranes are widely used in various industries of the national economy such as metallurgy, electric power, ports, logistics, machinery manufacturing and marine engineering. They are important process equipment for industrial production and are related to the safety of people's lives and the safety of national economic operations. and social stability are important components of public security in all countries. The development momentum of my country's hoisting machinery industry is strong. As of the end of 2017, the number of hoisting machinery in my country reached 2.2375 million units. According to the "Notice of the State Administration for Market Regulation on the Safety Status of National Special Equipment in 2017", the accident rate and fatality rate of cranes in my country rank first among the eight categories of special equipment. Therefore, there is an urgent need for an effective means to ensure the safety of in-service cranes. Safe and reliable operation of machinery.