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Comparison of static characteristics of electro-hydraulic amplifiers with proportional and servo control
Engineering Education # 07, July 2013
DOI: 10.7463/0713.0579738
The authors consider results of experimental studies of static characteristics of amplifiers with proportional and servo valve control. A comparison of characteristics that were recorded in a specially created complex allows to evaluate the accuracy of an amplifier with a proportional valve control and determine the impact of hydrodynamic forces applied to the spool on these characteristics. Experimental results prove flow characteristics and dependence of hydrodynamic forces on displacement of the spool; these results were obtained with the use of a computer model of a hydraulic amplifier. It was shown that if the spool has profiled surface, static characteristics of amplifiers with a proportional and servo valve control become approximately the same due to the balance of hydrodynamic forces. Thus, the authors established a possibility of application of simpler amplifiers with less power consumption and with a proportional valve control instead of a servo one. This statement is important for designing hydraulic drives.
Computer study and calculation of hydrodynamic loads on the valve
Engineering Education # 10, October 2012
DOI: 10.7463/1112.0491484
The authors provide results of computer studies and calculations of hydrodynamic forces influencing the valve. With the use of FEM they determined pressure distribution on the surface of the valve which had the diameter of 6 mm in cavities 1 and 2. Moreover, the authors obtained distribution of axial hydrodynamic forces influencing the valve in the cavity 1 and cavity 2 with the valve shift to a maximum value of 0.6 mm; and they build graphs to compare the values of the hydrodynamic forces calculated by FEM and analytical method. The calculation results are confirmed by experimental data previously published by other authors. With the help of the developed methods the authors determined the effect of changing the temperature of the working fluid (oil) in the range from -40 ° C to +50 ° C of hydrodynamic forces.
Balancing hydrodynamic forces by shaping valve’s surface
Engineering Education # 11, November 2012
DOI: 10.7463/1112.0491497
A method of reducing power required for electromechanical converter by balancing hydrodynamic forces acting on the control valve was considered. To calculate these forces, the finite element method was used; it allows one to determine the shape of the valve’s surface, which provides minimal values of hydrodynamic forces. In addition, graphs were plotted in order to compare the values of hydrodynamic forces obtained with the finite element method for unshaped and shaped spools, for two types of spool-type valve (supply of liquid in the center and along the edges of the valve). Using the finite element method, the distribution of pressure over the surface of the valve having the diameter of 6 mm, in the gap and the cavity of the spool-type valve was performed. Results of computer shaping of the valve and investigation of the influence of manufacturing precision of the valve on balancing hydrodynamic forces are given in the article.
 
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