An electronic system designed for controlled hydraulic movement is a synchronized lifting system. The pressure and extension of some cylinders are transmitted back to a central computer control system in this electronically managed system. This control system automatically opens and closes directional control valves as needed to keep the load level within a predetermined and precise tolerance. As a result, the system will correct for minor fluctuations in pump output or cylinder size. A synchronized lifting system is commonly used for bridge raising or repositioning, heavy equipment lifting and lowering structure leveling, and structural testing.
Individual cylinders can be controlled manually for set-up purposes, as well as fully synchronized lifting and lowering. Monitoring and data logging is displayed on the touch screen display, and full safety features are standard.
A multipoint lifting solution on a structure with uneven load distribution is provided by a split flow pump, such as the Hi-Force HSP family. The pump lifts the load by providing nominally equal oil flow to each output, sufficient for many applications. However, slight differences in the lift are accentuated when there is an unequal load distribution or the cylinder stroke required is exceptionally long, which might result in an uneven lift in some situations.
While the HSP family of pumps includes a control hand pendant that allows for independent changes to each cylinder as needed throughout the raise, a synchronous lifting system may be the better alternative if greater accuracy is required. Hi-Force offers various HSP split flow pumps throughout its network, but synchronized lifting systems are individually created by the design and engineering team to fit each application.
FPT’s synchronous lifting technology was employed during the lifting and lowering phases to lift a bridge with a precision of 1 mm. In the realm of road infrastructure and construction, routine and emergency maintenance of roads, highways, bridges, viaducts, railways, and undergrounds are required, necessitating the use of lifting equipment.
The Synchronous Lifting System makes synchronous lifting and jacking truly computerized. This system prioritizes precision with tolerances as tight as 0.04″ between the leading and lagging cylinders. Up to 24 lifting points may be controlled, data can be stored and recorded, and the system can be used with regular single or double-acting cylinders. For positioning and weighing, stroke and load-controlled movement are used. For maximum safety, load and stroke alarms are installed. Hydraulic pump and controls integrated to 10,000 psi.
Synchronous Lifting Technical Requirements
The actual project of lifting and removing the old bridge and erecting the new bridge serves as the backdrop for this paper. The demand for precision control of the lifting device is significant, necessitating exact control of the lifting speed and displacement and ensuring that multipoint synchronization faults are kept within a safe range. The bridge’s force study is performed using finite element software. When the displacement deviation during the lifting operation of an ancient bridge demolition is less than 5 mm, the bridge structure will not crack in principle and will meet the demolition requirement.
Because the new bridge is an integral steel structure, the acceptable deformation range is significant when it is assembled as a whole, and it can also meet installation and construction criteria. As a result, the displacement deviation must be controlled to within 5 mm, posing substantial technological challenges for designing an electrohydraulic control system. When the displacement deviation reaches or exceeds the allowable amount, the control system will instantly sound an alarm and shut down the hydraulic system to protect the bridge body, investigate and determine the cause, and resume lifting operations once all issues have been resolved.
Experiment on Synchronous Lifting System Debugging
The new control strategy for this synchronous lifting system is investigated using mathematical modeling and simulation tools, some controller control parameters are set, and the control strategy’s progress is validated. On the other hand, the simulation model cannot adequately reflect the actual operation. Therefore, field testing and debugging are required to evaluate further whether the scheme’s effect is optimum.
The design can be referenced via mathematical modeling and simulation. The synchronous lifting debugging experiment is carried out to verify the rationality of the design after the design scheme is determined and accomplished, as well as the assembly and manufacture of the entire vehicle. The lifting experiment is carried out after the examination.
In the experiment, the real-time displacement signals of each hydraulic cylinder can be acquired. After the experiment, the synchronization error curves under partial load and no partial load are obtained. Therefore, it can be seen that the displacement deviation is less than 5 mm, which meets the bridge synchronized lifting criterion.
The entire system is managed electronically where the extension or the pressure of many cylinders are sent back to the control system of the central computers. This system will automatically open and close the control valves that are directional as needed to safekeep the levels of loads within the specific tolerances.
Results
A single-channel mathematical model of the lifting system is constructed. The transfer function between the displacement of the hydraulic cylinder and proportional reversing valve is obtained, with the goal of the multicylinder synchronous lifting of the big prefabricated bridge. The control strategy for “master-slave” synchronization is chosen and designed. Using the MATLAB software, the synchronization effect is validated. The fuzzy PID control is implemented in the model, and the simulation model’s settings are tweaked to achieve the best results. The simulation results show that the fuzzy PID control and the “master-slave” control methods are successful. And the test results demonstrate that after employing this technique in multicylinder synchronous lifting, great synchronous accuracy under big loads and huge unbalance loads can be achieved.
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