The Design And Commissioning Of Synchronous Control System For Hydraulic Lifting Platform

The development of the city is improving the constructing of urban high buildings, the lagging form of scaffold is replaced by core wall. The steel platform is the basic frame of the core wall, which serves as the working and the storage framework. The appearance of steel platform is metal mesh and it guarantees the working safety. In order to realize the steady movement of platform which needs to climb higher with floors increase, borrowing domestic and overseas experience, this thesis designs a synchronous control system for hydraulic lifting platform.At the aspect of whole control, the system adopts “decentralized control, centralized management”, that is “one master station and four slaver stations”. This way could not only reduce the loss of transportation of long hydraulic tube, but also make the platform lift the load evenly. The operators supervise by the upper machine and four stations are responsible for execution of hydraulic items and acquisition of analog signals. The slaver station could be operated either by hand separately or run by the command of the master station. The upper machine and the main controller connect the slaver station by Profinet, which offers an interface to monitor and execute.As for the hydraulic synchronization, the system uses the principle of “the equal synchronization” macroscopically and “the master-slaver synchronization” microscopically. In order to achieve synchronization within the set value, the paper uses a new way of “extreme value” in place of “mean value”. According to the feedback of stroke sensors, the program calculates the proper stroke reference in different processes of cylinders movements. The tolerance is defined as the difference of current stroke value and stroke reference. According to PD adjust principle, the stroke tolerance will be converted to valve-on time. Synchronization is achieved by switching on and off the electrical valve driven by solid-state relays which are controlled by PWM of PLC. Because of the flexibility of steel platform, the pressure of cylinders should be considered to guarantee every cylinder runs within norm load. That is, the control must comprise double closed-loop control of stroke and pressure.In the software structure, different functions are divided into modular parts. The communication parts are realized in the master station, while the slaver station is responsible for all executions.Manipulators use upper machine for monitoring operation. It greatly lowers the threshold for users by friendly interface, perfect alarm system and real-time data storages.The on-site construction indicates the system reduces the safety problems on one hand and improves the efficiency and shortens the construction period on the other hand, which is done on the premise of precision and reacting speed. The project gains a good result in practice as expected.