Study Of The Key Technologies For Temperature Measurement And Control In Large-Scale Metrology

With the development of scientific technology becoming more and more furious, it is highly expected on the geometric size measurement precision of large-scale object. Measurement precision has close correlation with temperature. The temperature sensitivity of measuring-instrument and the temperature field of measured area have impact on scale-measuring system's precision. The disequilibrium of temperature field affects geometric size of measured object and measuring instrument, which brings a series of physical changes and will affect measuring precision of whole system. Currently, domestic and foreign experts have done lots of research and made great achievements in temperature measuring and control field whatever theoretically and practically. However, due to the complexity of large scale space's temperature field distribution and thermal characters of its objects, the effect on precise scale measurement is still not perfect. Moreover, there is no perfect method on precise temperature control in such large space. Therefore, the achievement of this subject is very meaningful to improve temperature measuring and control capability, which will furthermore improve geometric size measurement precision of large scale object.Based on the principle of error compensation for heat distortion, correction for heat distortion of large-scale metrology and correction for wavelength of interferometry are studied. The results show that error compensation for heat distortion is an effective way to inhibit temperature error for large-scale metrology.Considering that thermal balance time produced by self-heating effect of platinum resistance is far less than circuit balancing time, a high precision platinum resistance temperature measuring method based on pulse current exciting is developed, which applied a pulse width adjustment method based on heat transfer theory and pulse current exciting, and then obtained a precise transforming circuit with minimum self heating error. Then a small size automated precise measuring control instrument JMCW-1 is designed. For sensor's self heat effect and non-linear error, improved descriptive model is adopted by platinum resistance on measuring and calibration with software non-linear calibration. Distributed temperature measuring and control system is designed, with which implemented multiple point temperature sampling, analysis.With the establishment of precision temperature controlling space, developed a new method of staged temperature control in discrete area and built corresponding temperature measuring control system. With fuzzy cluster analysis, studied controlled space and distribution of measured points, obtained best temperature control and measured points. In addition, based on the analysis of dynamic and static control model, studied control method combining with partitioned, stepped and segmented control, put forward a control strategy combining with artificial intelligent sampling and PID control, and erased coupling effects among areas by adopting neural decoupling method.In order to make data evaluation on developed precision temperature measuring control system JMCW-1, made comparison tests in ice water mixture and constant temperature oven using standard platinum resistance. Test results indicate: JMCW-1 can at least achieve measuring precision of 0.05℃during the range of 0℃to 40℃. To evaluate instrument's temperature control effect, tests on large scale measured objects and its temperature control space were made. After analysis on tested results, it indicates that adopted new control method helps system achieve great temperature stability and anti-interference capability.Thermal expansion coefficient of large-scale component is a key factor that affecting the precision of dimension measurement. Based on principle of measurement chain compensation, a laser interferometry based on vacuum light path as optical frame has been put forward, and it adopts simultaneous temperature control, with which high accuracy integrated thermal expansion coefficient of large-scale component are obtained. In addition, deeply analyzed all kinds of error factors and studied thermal performance of temperature-sensitive optical elements in double-frequency laser interferometry, calculated and analyzed temperature coefficients in different situation, which ensures high precision of thermal expansion coefficient measurement.