The Research On Linear Variable Differential Transformer With High Linearity For Electrohydraulic Valves

In this paper, the LVDT’s FEM for hydraulic valves is built. Using the electromagnetic software Ansoft Maxwell makes some simulations for LVDT’s electromagnetic properties. A new structure of LVDT is put forward, which can efficiently improve the linearity, linear stroke and the stroke length ratio of LVDT. In this paper, the experiment system of LVDT is also built up to test the product of a certain company. The results indicate the simulate results is very coincide to test results.The main content of this thesis:In chapter 1, the history of electro-hydraulic proportional control technology and LVDT are introduced. The main feature, domestic and international applications, development trend and present research of LVDT are expounded. The main research significance and contents are summarized.In chapter 2, the working principle, equivalent circuit, static and dynamic characteristics are introduced. The mathematic model of LVDT is built up. By the mathematic model the relation of all the parameters is figured out. In this chapter, the method of equivalently build up the FEM of LVDT is researched. And build up a reasonable FEM.In chapter 3, the steady electromagnetic of LVDT is simulated by the Ansoft Maxwell. For the defect of the present LVDT’s performance, a new structure is put forward, which adds two exactly the same magnetic rings and they are symmetry about primary winding. So this new structure efficiently improved the linearity, linear stroke and stroke length ratio of LVDT. In addition, in this chapter, the Workbench is used to analyze the steady structure of the LVDT pressure tube in high pressure environment.In chapter 4, the transient electromagnetic field of LVDT unimproved and improved are simulated by using the Ansoft Maxwell. The soft magnetic material is introduced and the effect to LVDT’s characteristic with different magnetic material is analyzed. In the final, the test system is built up and the product is tested. The results indicated the simulate results is very coincide to test results. So the conclusion of simulation is the true reflection to product’s practical characteristics.In the end, some conclusions and achievements about this thesis are summarized, and the future research proposals are suggested.