Dynamic Analysis And Simulation For Direction Shift System Of Concrete Pump With S Tube

Concrete delivery pump plays a more and more important role in modern construction engineering. The directional shift system of the pump must complete S tube's shift operation in very short time, which may cause hydraulic shocking and cylinder bumping at the same time during the operation. The hydraulic impact not only results in noises and vibration but also reduces the equipment's life time. The cylinder bumping tends to generate iron chippings mixed with the hydraulic oil, which may seriously damage the components of hydraulic system and even cause the trouble of hydraulic system. To avoid the hydraulic impact, the pressure of the hydraulic cushion can't be too high; and to avoid the cylinder bumping, the speed of piston needs to be controlled within the proper scope as the piston reaches the bottom of the cylinder. To meet above requirements, the parameters of directional shift system must be scientifically determined, which requires to establish the analysis model of the dynamic characteristic for the directional shift system and then analyze the model in theory.The oscillatory mechanism of the concrete delivery pump is a slider- crank mechanism composed of piston, cylinder block and the oscillatory rod that is linked with the S tube together. The dynamic characteristic of directional shift system in the concrete delivery pump depends upon the dynamic characteristic of the oscillatory mechanism and that of the hydraulic transmission system . This article has deeply analyzed the load of the shift system and cushion characteristic in cylinder with different structures. In this article, the dynamic characteristic analysis model of the oscillatory mechanism is established through the Lagrange equation, while that of the hydraulic system through power bond graph. Then the two models are combined to be one for the whole directional shift system through their power ports and the whole model is simulated with the software: MATLAB/Simulink. As result, the curve of the speed of the piston changing with time and that of the hydraulic cushion pressure obtained from the simulation mostly reflect the dynamic characteristic of the whole system. Based on the model, it is simulated, the directional shift system of a concrete delivery pump manufactured by a factory, to acquire it's dynamic characteristics. The directional shift system is simulated again after improving the cushion structure of the shift cylinder in the system based on the previous simulation result. A better dynamic characteristic is acquired for the improved directional shift system. The simulation results show: (1) There existed contradiction between avoiding of the piston bumping and overcoming the hydraulic impact in cylinder in which the clearance is simply used as the cushion structure. It is at the coast of increasing the shift time and the hydraulic cushion pressure to reduce the bumping speed of piston. The higher cushion pressure will result in new vibration and damage of the system while longer shift time may result in the leakage of concrete mixture and drop in productivity. So both of these factors should be given careful attention when selecting the parameters of the cushion structure. (2) The cushion length's influence on system's dynamic characteristic is affected by the cushion clearance. A small cushion clearance with a adequate cushion length can apparently reduce the piston's bumping speed, while it can't more apparently reduce the piston's bumping speed with longer cushion length but extend the shift time. The clearance be bigger, the cushion length should be longer, and the clearance be smaller, the cushion length should be shorter. Reducing the cushion clearance can obviously reduce the piston's bumping speed but heighten the peak value of hydraulic cushion pressure at the same time. So the relationship between the length and clearance of the cushioning structure should be considered synthetically and carefully: when the piston shocking become the primary problem in the direction shift system, the cushion clearance shou...