Simulation And Experimental Verification Of The Operating Characteristics Of Displacement Sensors For Valves

To achieve accurate control of the orifice flow,the spool displacement must be accurately measured in real time for orifice independent control type high flow hydraulic valves.Therefore,the design of compact displacement sensors with small size and high accuracy is the basis for achieving these goals.This paper focuses on the main performance indicators of the steadystate performance of the LVDT(Linear Variable Differential Transformer)type displacement transducer for valves and optimizes the internal structure of the transducer by simulation.A high-precision compact displacement transducer is designed,and the test results show that the main performance indexes meet the design requirements.The main research contents of this thesis are as follows:The operating principle of LVDT type displacement transducer and its equivalent circuit are analyzed to obtain the mathematical model of displacement transducer and analyze the influence of each structural parameter of the transducer on the electromagnetic performance.At the same time,the equivalent modeling method of the LVDT type displacement transducer is analyzed.Based on the electromagnetic mechanism of the three-section LVDT type displacement sensor,finite element simulation model and mathematical model are established,and the electromagnetic field numerical simulation software Maxwell is applied to simulate the electric-magnetic field coupling of the working process of the displacement sensor.In order to improve the performance of the displacement transducer,three LVDT structure optimization methods are adopted:the conventional flat solenoidal excitation coil of the displacement transducer is designed as a segmented outer stepped solenoidal coil structure to improve the coil coupling effect and optimize the nonlinear error of the LVDT;the conventional smooth cylindrical skeleton structure is designed as an inner stepped skeleton,which enables the excitation coil to maintain the inner stepped distribution and at the same time,ensures that the outer solenoidal coil of the displacement transducer has a high degree of coupling.The traditional smooth cylindrical skeleton structure is designed as an internal stepped shape skeleton,which ensures the multi-turn layout of the outer surface of the solenoid coils in the plane of dense winding,and improves the uniformity of the working magnetic field in the end area of the sensor;the traditional lamellar end cover symmetrically distributed at the end of the displacement sensor is optimized into a "combined ring-cap" permeable end cover structure with built-in ring and external lamellas,which can optimize the spatial flux distribution of the LVDT.This can optimize the spatial flux distribution of the LVDT,especially reduce the leakage flux effect at the end of the LVDT,and achieve the purpose of magnetic field compensation at the end.All the above solutions can compensate the working magnetic field of the displacement transducer,and then optimize the nonlinear error,sensitivity and stroke length ratio of the LVDT type displacement transducer.After post-processing analysis of the simulation results,it is found that the above three structures can improve the short linear stroke,poor linearity and small structural stroke to body length ratio of the conventional LVDT type displacement transducer.Finally,the prototype of the studied LVDT structure was processed and tested,and after post-processing analysis of the test results,it was found that the simulation results were basically consistent with the test results.