Design & Research Of Large Range And High Precision Bidirectional Displacement Measurement Device With Walking Pattern

With the hydraulic and pneumatic systems used in the large-stroke high-precision equipment more widely, the requirement of measurement accuracy is getting higher and higher for the output shaft displacement of large-stroke hydro-cylinder/air-cylinder. Displacement sensor is the key for high-precision displacement measurement of large-stroke hydro-cylinder/air-cylinder. But with more and more large-scale hydro-cylinder/air-cylinder, the requirement of measurement accuracy higher and higher and the motion more and more complicated, displacement sensors are becoming increasingly difficult to meet the measurement requirements due to subjective and objective reasons. Firstly, the displacement sensor based on the research status at China and overseas has been studied. Then, for large triaxial sample instrument object, this paper describes problems faced by the current large displacement sensor to achieve high accuracy displacement detecting for output axis of it. In addition, according to the characteristics of large triaxial instrument, this paper designs a device that can achieve high accuracy bidirectional displacement detection for the output shaft of large-stroke hydro-cylinder/air-cylinder. Three aspects of simulation, test and error compensation have been studied in this paper. The content of research mainly includes the following several aspects:Firstly, there is a detailed analysis and sorting for the research of displacement sensor status at China and overseas in recent years. This paper makes generalization and summary to the characteristics of commonly used large stroke displacement sensor. Then, taking large triaxial sample instrument for object, this paper describes problems faced by the current large displacement sensor to achieve high accuracy displacement detecting for output axis of it and proposes a solution to solve it. There is a detailed design about structure, micro-controller circuit and so on based the solution.Secondly, a control scheme that can achieve high precision measurement for the large range bidirectional output shaft based on the hardware design of the measuring device has been proposed, that is studied to test the synchronous measuring ability of the measuring device and the detecting ability of the moving baffle in different moving conditions based on the measuring devices Simulink model. It can draw a conclusion that this control scheme can achieve high accuracy displacement detecting for large range bidirectional output axis.In addition, in order to further study performance of measuring device, the measurement device is used to detect displacement of the beam whose movement can be cortrolled. By controlling the beam in different speed and different motion state, the paper further study on performance of the measuring device. By analyzing the test results, it can come to a conclusion that the measuring device is showed higher measuring accuracy no matter the beam is one-way motion, variable motion or turning motion.At last, in order to further enhance the measuring accuracy of measurement device, the measurement error that caused by the deformation of mechanical structure of the measuring device is studied. The reset spring on the guide bar is the main source causing the deformation of mechanical structure. Experimental research was made on relationship between different amount of compression, different positions of the guide rail and measurement error that caused by the deformation of mechanical structure of the measuring device. According to the research, the error compensation formula is build, that can compensate the measurement error that caused by reset spring under different amount of compression, at different positions of the guide rail.