Abstract : This paper introduces the speed regulation principle of PIC controller and frequency converter. It explains the application of PIC controller and frequency converter technology on the MQ530 gantry crane, and analyzes the effect of using a PLC controller to control the frequency converter speed regulation, namely, convenient continuous control within the speed regulation range. This results in smooth operation of each mechanism, low mechanical impact, extended service life of the gantry crane, and reduced failure rate. Keywords : PIC controller, frequency converter, gantry crane application. The two gantry cranes originally built at Pier 8 of Yangzi Transportation Co., Ltd. were constructed in the early stages of the plant's construction, mainly responsible for the loading and unloading of solid materials for Yangzi Petrochemical Company. With the expansion and renovation of Yangzi Petrochemical Company and the establishment of Yangzi Petrochemical-BASF Co., Ltd., the usage frequency of the two gantry cranes has increased, consistently operating at full and even overload. As the service life has lengthened, the failure rate of the two gantry cranes has begun to rise. Frequent overcurrent has caused the main contactor contacts to burn out and stick together, resulting in phase loss or short circuit faults. At the same time, the original gantry crane electrical control used a large number of relays and contactors, resulting in a complex electrical structure, difficult maintenance, and high failure rate. The use of series-connected resistors in the motor rotor for stepped speed regulation results in extremely unstable operation of the gantry crane, high energy consumption (because energy is consumed by the series-connected resistors), and low efficiency. Therefore, the new gantry crane (MQ53o) adopts advanced and stable stepless frequency conversion speed regulation technology. [b]1 PLC Controller and Frequency Converter Speed ​​Regulation Principle 1.1 PLC Controller[/b] PLC is short for Programmable Controller, a digital electronic system designed and manufactured specifically for industrial applications. It has abundant input and output interfaces and strong driving capabilities. When a PLC is put into operation, its working process is generally divided into three stages: input sampling, user program execution, and output refresh. Completing these three stages is called one scan cycle. During the entire operation, the PLC CPU repeatedly executes the three stages at a certain scan speed, as shown in Figure 1. [b][align=center]For more details, please click: Application of PLC Controller and Frequency Converter Technology in Gantry Cranes[/align][/b]