Performance Analysis And Key Technology On Capacitor-based Micro-force Measurement System

With the development of modern science and technology, the measurement of tiny force value has been widely used in the areas of micro and nano scale processing and manufacturing, the observation of microscopic friction phenomenon, the analysis of the liquid surface tension, the precise control in the field of aerospace and various industrial fields. Studied by more and more scholars and experts, nowadays, the method has become an important research topic. Due to the imperfect micro force measuring system, the characteristics play a relative lag role. It is crucial to establish design method of power transmission system and the measurement of micro force sensor on the micro force value measurement standard. In this dissertation, we conduct the comprehensive research of micro force measuring system by using the capacitance weighing power transmission system with micro force as the carrier. To improve micro force power transmission system, the structure of the sensor design and error compensation as well as other three systems, we carry various research and exploration on theory design and technological innovation. The main tasks and contributions of the dissertation are as followings:(1) The performance of the analysis method of micro force measurement system has been studied. After analyzing the working principle, We build a general index system for the micro force measuring system. In terms of precision, range, repeatability and stability, we analyze how the factors influence the system performance. The conflict analysis and resolution in TRIZ theory is introduced to find the key factors affecting the system performance. this paper constructs the system function model and make a detailed analysis of the existing conflicts and primary cause. Based on this method, The mapping model for micro force measuring system performance is constructed, the system performance is mapped to force organization, sensors and error compensation.(2) To solve the problems of the coupled displacement and partial load resistance, we design the double parallel flexible steering mechanism, and analyze mechanical properties. In order to evaluate its performance, we conduct the stiffness analysis to verify its stability. Based on the equivalent of a cantilever beam, we put forward a method to evaluate the resistance ability to lateral partial load and lateral load. After using, we establish the multi-objective optimization model according to the analysis result of the double parallel flexible mechanism, discuss the solution method, contrast the optimized structure and original structure, and verify the superiority of the design in this dissertation.(3) In order to ensure the accuracy of the original capacitive sensors and improve the range of conflicts, we design the double plate change from the capacitive sensor to ensure the accuracy under the condition of double range. We analyze the mechanical performance of the guiding stiffness and torsional stiffness, and discuss the effects of structural parameters on the performance. The multi-objective optimization model is established for optimizing the performance after verifying the design results of finite element analysis. For circuit and control section, this dissertation introduces the double plate of the capacitive sensor signal control and the transformation process.The circuit is designed based on single chip microcomputer control, and the corresponding experiment is designed to verify results.(4) The coupling error compensation method is studied for the micro force measuring system through the experiments. We have measured the error change of the force measuring system under different temperatures. In order to compensate more effectively, we discuss the coupling error separation method according to the principle of error, separate it into the load error and thermal error, and establish the mathematical model of comprehensive error. On this basis, this dissertation proposes a simple error compensation principle and expounds the corresponding error compensation strategies for short time and long time load respectively. The error compensation module is designed by single-chip microcomputer, and the micro force measuring system is verified in terms of accuracy, stability and repeatability through the experiments.