Study On The Synchronous Lift System For Footbridge

The general footbridge has height restrictions, which cause large objects can't pass through successfully and this take some inconvenience to transportation. In order to solve this problem, raisable footbridge can be put to use. When large objects can't pass through successfully, Hydraulic Lift System will be used to lift footbridge synchronously, and footbridge will be put down after large objects pass through successfully. Using raisable footbridge can reduce much traffic disruption time, which is of great significance for transportation.The thesis dedicated to the design and research on Synchronous Lift System of this footbridge. Two adjustable pressure circuits were used to enhance the system efficiency, and balanced circuit adopting Hydraulic Control One-way Valve and One-way Restrictive Valve was also used after compare all kinds of balanced circuit comprehensively. Considering two kinds of Synchronous Lift Control System, it's easy to decide to choose "Synchronous Control System Base on Displacement Sensor" which fit for this system, then work flow diagram and hardware of system was designed and the type of some key elements was decided. After making an acquaintance on problem when symmetric valve control asymmetric hydraulic cylinder, asymmetric valve was used to control asymmetric hydraulic cylinder. Then thesis dedicated to model on whole hydraulic control system, and make an analysis on static and dynamic characteristics of system. Analysis shows that correcting unit should be set up to meet the expected static and dynamic characteristics of system.The massive work was done on correcting system in PID controller and making a simulation and simulation result shows that system has a fast dynamic response and high stability after correction. Comparison on kinds of controller shows that Fuzzy-PID Two-mode Controller is a comparatively perfect controller and this controller has a fast dynamic response and powerful ability to resist disturbance and time-lag, but has no overstrike. So Fuzzy-PID Two-mode Controller was used on deviation rectification circuit.In the end, simulation on Synchronous Lift Control System was done based on AMESim and Simulink and simulation result shows that Control System meets the demand.