Design And Study On Variable Frequency And Speed Adjusting Control System In Crane

With the application of modern control theory, new control strategies appear continually. The development of the microprocessor and microelectronics lead to the increasing maturing of the variable frequency control systems. This thesis studies the application of the variable frequency technique to cranes, and applies this technique to the latest 40 ton Dragon Gate derrick that was designed and produced in ZHENG ZHOU Railroad Machine Factory. Through the practical application for one year, it is proved that this technique is feasible and the newly designed derrick has good performance.First of all, this thesis discusses the burden characteristics of Dragon Gate derricks, speed adjusting methods and the features of variable frequency control systems. Then the structures and principles of the Programmable Logic Controller (PLC) and inverters are introduced. Thirdly, the features and problems of main speed adjusting methods currently applied in cranes are analyzed and summarized in detail. The analysis and comparison with the variable frequency and speed adjusting are made, and the control parameters and the advantages of the variable frequency and speed adjusting are given. Fourthly, the analysis and research on the design of various control parameters are realized, and such control parameters are given. Using such techniques as variable frequency, PLC and touch-screen control, the smooth speed adjusting is accomplished with the help of the development of software and hardware as well as the design of various control parameters. According to the changes of lifting weights, this smooth speed adjusting switches lifting work speed and walking speed of big and small vehicles automatically. The lifting machine can switch different work speed of empty hook, host hook and assistant hook automatically in terms of the load sizes. Therefore former two sets of host and assistant lifting machines can be replaced by one lifting machine. Because this replacement saves a set of lifting machine inside the small vehicle, the weight of the small vehicle is reduced, the carrying capacity of the steel structure is improved, and also the maintaining space inside the small vehicle is increased. The speed adjusting system in our newly designed and produced 40 ton Dragon Gate derrickwith full variable frequency has the function of modifying such technical parameters as lifting speed and speed-up and down time at any moment, ensuring that the derrick works in the optimal state, the loads position precisely in the air or landing, leading to the goods safety and high loading efficiency. The lifting machine and walking machines of big and small vehicles operate smoothly, and braking impact is small. The zero-location control of each machine is realized via the software, the performance of the derrick is improved, the malfunction is reduced and the security of loading operation is enhanced. At the same time, using inverters in varying frequency and speed adjusting has obvious energy-saving effect comparing to traditional series-resistance speed adjusting, and increases the power factor and work efficiency of the system greatly.