Study On Time Grating Displacement Sensor Based On Precise Confine Method Of Time-varying Magnetic Field

With the development of automation and intelligentization in manufacturing field, more and more closed-loop control systems are being used. As the displacement sensor is the key component of a closed-loop control system, its performance has much influence on the control loop of the system. In order to work in harsh environments, some systems usually need to employ displacement sensors working on time-varying magnetic field as position-feedback devices, because these sensors have high reliablity and interference rejection. Time-varying magnetic field is the coupling field of these sensors, and its propagation paths and distribution areas are confined respectively by magnetic material and coils, so the precision is affected by the magnetic confine methods. Confine methods which are used in current displacement sensors working on time-varying magnetic field neither make good use of the guiding effect of magnetic material and the flexibility of coils, nor exploit precise co-work of magnetic material and coils. As a result, the fabrication requirement, such as processing and assembling requirement, is high if the sensor is expected to make high-precision measurement, and thus the fabrication cost is high. In view of the development of sensors working on time-varying magnetic field, the research on precise confine methods and new time grating displacement sensors based on those confine methods was carried out. The work and achievements presented in this paper are summarized as follows:① Intensive research on confine methods of planar magnetic field has been done with the analysis of confine methods frequently used in current displacement sensors based on time-varying magnetic field, and then precise confine methods of magnetic field are presented. These methods fully utilize not only the guiding effect of magnetic material and the flexibility of coils, but also the co-work of them.② According to the precise confine methods presented in this paper and the principle of time grating, coils and magnetic frames of time grating displacement sensors are firstly designed as planar structures. Then several entirely new angular and linear displacement sensor structures are presented for angular and linear displacement measurement. Not only can new sensor structures fully utilize the confine abilities of magnetic frames and coils, but also can avoid the jump problem of magnetic paths in current time grating displacement sensors with the structure of “tooth and slot on double faces”.③ According to the research on absolute displacement measurement methods with the union of “precise sensor + precise sensor” and the online calibration method presented in the NSFC project named “Research on Self-examination and-calibration Method Based on Error Transformation of Time Grating Angular Displacement Sensor”, multi-function displacement sensors were researched and an angular displacement sensor structure and a linear displacement sensor structure which can make absolute displacement measurement and online self-calibration were developed.④ Proof work of new time grating displacement sensors was carried out by simulaton in order to verify the feasibility of pricise confine methods and new sensor structures. 3D models of all new time grating displacement sensors were built and simulated in computer software. Simulation results show precise relations in quality between the displacement to be measured and outputs of new sensors.Simulation work now only has indicated that pricise confine methods have better performance that those used in current time grating displacement sensors, but also shows that new sensor structures are feasible.⑤ Experimental work of new time grating displacement sensors was carried out in order to examine the actual performance of precise confine methods and new sensor prototypes. Based on 3D models of a new time grating angular displacement sensor and a new time grating linear displacement sensor, two kinds of sensor prototypes were designed and the electrical system for the prototypes were developed. The performances of the prototypes were examined in the platforms for precise angular and linear displacement measurement. Experimental results indicate that pricesie confine methods work better than those used in current time grating displacement sensors, and that new sensor prototypes have high precision, though the processing of their magnetic frames and coils is simple and manufacture requirement is low. In the range of 0??~?360?, the accuracy of angular displacement measurement is better than ?2.2?; in the range of 0mm?~?208mm, the accuracy of angular displacement measurement is better than ?3.4?m.⑥ The calibration method based on look-up-table was firstly used in time grating displacement sensor for the error reduction of new sensor prototypes. This method can solve the calibration problem of complex error and needs little calculation time. As a result, the use of this calibration method not only improved the precision of new sensor prototypes, but also is valuable to the following research on high-speed dynamic measurement of time grating displacement sensor.⑦ To meet the requirement in planar coil of new time grating displacement sensors, PCB(Printed Circuit Board) coil was firstly used in the design of time grating sensor. Compared with traditional coil, PCB coil has many advantages such as high precision, high uniformity, low cost, suitability for mass manufacture, etc., so the application of PCB coil is helpful to balance the precsion and cost of displacement sensors based on time-varying magnetic field.To summarize, by the analysis about the advantages and disadvantages of current confine methods of time-varying magnetic field, pricise confine methods were presented; Based on these precise confine methods and the principle of time grating, several entirely new structures of time grating displacement sensor were developed; Two kinds of sensor prototypes were designed, according to new sensor structure, and then experimental results show that new sensor structures are low cost but have high precision. Therefore, the research of this paper starts a new a way for the development of time grating displacement sensor, and the achievements may help meet more requirement in products.