Research On Magnetic Encoder For High-precision Servo System

Magnetic encoder is a new angular displacement sensor which is based onmagnetic sensor to detect angular. It has many advantages to compare withoptical encoder and rotary transformer, such as high reliability, low requirementto service environment, good anti-seismic performance, high revolving speed,simple structure, easy assembly, smaller volume and lower cost with the sameparameters. In recent years, AC servo motor industry has developed rapidlywhich shares large part of encoder market. In the case of ensuring performance,the cost of encoder become more and more sensitive as main component of servosystem. Due to the excellent performance and high cost performance of magneticencoder, it will replace other encoders in the field of industrial control industryand other fields. As a result, magnetic encoder has huge potential fordevelopment. Magnetic encoder is divided into the traditional reluctance typeand hall type. The former has complex structure, high-cost components and theoutput of angle is incremental. While the latter has simple structure and low cost,so it has been the mainstream development direction of magnetic encoder.Based on previous research, this paper studies a multi-pole hall-typemagnetic encoder to achieve high resolution angle detection with a low lost,which is used in high-precision servo system. No matter to industrial controlfield or to military aerospace and other special occasions, it has certain researchvalue. Firstly, this article analyses the advantages and disadvantages of singlemagnetic pole and multi-pole encoder, on the basis of this proposes the overallscheme of compound framework. This means the use of the angle calculated bysingle-pole encoder is to recognize the range of multi-pole encoder, thencombined with the angle in the range of multi-magnetic-pole to output absoluteangle. In this way, it can improve the resolution of encoder. Under the overallframework, it designed the structure for the generation of magnetic signal,modeling and simulation of the space magnetic field generated by magnetic steelto determine the optimum sensing area and air gap. Also, it developed the signalprocessing card for magnetic encoder and completed the debugging. Ultimatelythe experimental data show that the developed multi-pole compound encoder hasreached the index of high resolution and the output angle obtains goodlinearization accuracy after linearization process. So it can meet the applicationrequirements of high precision servo system. Due to the simulation exists error,using hall sensor to test the actual signal of the magnetic induction generating portion. To adjust the hall actual installation location and sensing distancethrough the contrast experiment,that is also determined hall sensor model. Todesign the original angle acquisition program and build a data acquisition system.To collect the static and dynamic original angle solver that is to analysis theparameters of the combined multi-pole encoder.Finally, the result of commissioning and experiments shows that the overallscheme of combined multi-pole magnetic encoder is feasible. Increasing thenumber of magnet pole pair can produce good original angle signal quality andenhance the resolution ratio，effectively. All that meet the requirements of theencoder.