| During the lifting process of large hydraulic boom tower crane,frequent switching of working conditions will produce the lifting dynamic load,resulting in structural vibration.While affecting the working stability of the lifting mechanism,it will also cause the fatigue damage of the tower crane structure and form the hydraulic shock to destroy the hydraulic element seals,these will reduce the effective working life of the whole machine.Therefore,it is necessary to study the dynamic characteristics of the transition process of complex hydraulicmechanical systems of full hydraulic large tower crane.At present,studying the working characteristics of large equipment by simulation is an important means to for large equipment to carry out technical digestion and improve the design.In this paper,the lifting mechanism of a certain type of domestic closed hydraulic system driven by the boom tower crane is taken as the research object,and the influencing factors of the dynamic characteristics of the lifting mechanism are analyzed by means of integrated hydraulic-mechanical simulation.First,AMESim software is used to build the integrated simulation model of hydraulic boom tower machine,and set simulation conditions.The simulation experiment verifies the correctness of the modeling and analyzes the dynamic process of the hoisting mechanism at the same time.Then,the transfer function is used to determine the factors influencing the dynamic characteristics of the hoisting mechanism,including the initial tension of the hoisting rope,the rigidity of the wire rope and the speed regulation mode of the hydraulic system.Based on this,the influence factors are simulated and analyzed under given conditions by means of the mechanical-liquid integration model.The simulation results show that:(1)The initial tension of the wire rope has a significant effect on reducing the maximum dynamic load and peak pressure generated in the process of lifting the load off the ground.Compared with the control group without the initial tension,the maximum dynamic load decreases by 92.6%,and the peak pressure decreases by 19.4%.(2)The stiffness of the hoisting wire rope is selected within the scope of the specification.The ratio of the maximum stiffness to the minimum stiffness is 2.33,and the difference between the maximum dynamic load and the maximum peak value of the hydraulic system is only 5.2% and 4.3% respectively.(3)Under the same load condition,the steady-state working pressure of the hoisting pulley unit is increased by 46% compared with the double-rate hydraulic system;(4)Under the same load condition,variable pump speed regulation is adopted compared with variable motor speed regulation,and the steady-state working pressure is reduced by nearly 50%.Draw a conclusion from this:(1)When the load is off the ground,the vibration of the system can be effectively reduced by means of slowly winding up and accumulating the wire rope tension.(2)The selection of steel wire rope stiffness within the specified range has no obvious influence on the additional inertial force in the hoisting process,and can be selected with the lowest cost principle.(3)Under the premise of satisfying the speed requirement,variable pump should be selected to adjust the speed,which can effectively reduce the heating of the closed system.the machine-liquid integration simulation More attention is paid to the influence of the coupling relationship between machine and liquid on the dynamic characteristics of the lifting mechanism.Compared with the traditional research method that divides the hoisting mechanism into two subsystems,mechanical and hydraulic.The machine-liquid integration simulation is adopted to pay more attention to the influence of the coupling relationship between machine and liquid on the dynamic characteristics of the hoisting mechanism,and the simulation results are more in line with the reality.This method provides a theoretical basis for the improvement of the technical digestion,structure and hydraulic system of the tower crane,and is of referential significance to the research of other high-power mechano-hydraulic integrated systems. |
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