Research On Methods And Key Technologies Of Self-calibration And Error Correction For Time Grating Angular Displacement Sensors

Time grating angular displacement sensor is a novel sensor developed based on the theory of time-space transformation. It begins to stride toward the development direction of industrialization in recent years. Now though the technology of ultra-precision ruling in spatial domain is avoided by time grating in the process of machining, a high-precision reference basis, a sensor which is depended on ultra-precision ruling in spatial domain, is still needed in the process of testing and calibrating of time grating. And with further improving accuracy of time grating, it is hard to find a higher precision reference basis to calibrate time grating. So the problem of reference basis has to be solved. Furthermore, under the terrible operating environment, time grating and other same type sensors have a common problem:how to keep the measuring accuracy for a long time when parameters of machinery and electric changes. These two problems mentioned above motivate the research on self-calibration and auto-correction of error of time grating angular displacement sensors in this paper.At present a few researches were done on self-calibration of angular displacement sensors and among these researches, circle closure or converted it to a const angle was often taken as a reference basis to realize self-calibration or mutual calibration of sensors. Using two sets of reading heads or two divided circles, structures of these sensors with self-calibration were complicated and using conditions were required very harsh, thus they seldom can be industrialization produced. High precision angular displacement sensors by self-calibration were usually used in laboratory. Typical ones of these sensors are ultra-precision angle-measuring devices owned by National Metrology Institute of Japan (NMIJ) and Physikalisch-Technische Bundesanstalt (PTB) respectively. They realized high precision measurement by self-calibration.In this paper, theoretical analysis and mathematical modeling methods are taken to study on self-calibration and error self-correction according to error features of time grating angular displacement sensors and parasitic type time grating. The work is based on investigation enough and further analysis on self-calibration methods of angular displacement sensors at home and abroad. The aim of the research is realizing the technology of self-calibration and error correction to use large-scale application in industrialized production of time grating, especially in large and complex production and research fields. By far completed major studies and creative works are as follow:(1). Based on analyzing and summarizing self-calibration methods of displacement angular sensors at home and abroard and based on error coordinates transformation (ECT) self-calibration method applicating in time grating early research, a novel self-calibration method called fixed angle shift (FAS) applicating in time grating was put forward according to error features of time grating and parasitic type time grating. In addition theoretical derivation and mathematical modeling were made to this method.(2). A dynimatic error self-correction method for parasitic type time grating called minimum infinitesimal interpolation (MⅡ) was put forward and error correction model was established. Furthermore, harmonic error correction for time grating of angular displacement sensors and minimum infinitesimal interpolation error correction for parasitic type time grating were automatically made.(3). It was designed self-calibration structures, circuits and electrical system for time grating angular displacement sensors and parasitic type time gratings in this paper.(4). It was designed experiment systems and Programmes. A large amount of experimental researches have been made, and detail experimental data have been given. Its results are as follow:①Experiments were done for static self-calibration and harmonic error self-correction for time grating angular displacement sensors. The accuracy of static self-calibration is1" and of error correction is2.3" by comparision experiments after two times self-calibration and self-correction.②Experiments were done for static and dynamic self-calibration and minimum infinitesimal interpolation error self-correction for parasitic type time gratings. The accuracy of static self-calibration is21" and of error correction is28" by comparision experiments. The accuracy of dynamitic self-calibration is6.2" and of error correction with minimum infinitesimal interpolation method is13.2" by comparision experiments.(5). Anylisis was made respectively for aforementioned various results, and error sources of various parts were given. Furthermore, quantitative analysis is also given in the paper. In conclusion, base on further analysis on principles and error features for time grating angular displacement sensors and parasitic type time gratings in the paper, self-calibration and error self-correction methods were discussed and corresponding error modeles were erected. Furthermore, analysis on self-calibration and error correction were made based on a large amount of experiments.theoretical basis and implement methods can be provided for further research for future works.