BG Motor-Magnetic Encoders VS Optical Encoders

NEWS    |    Aug 17, 2021

In recent years, magnetic encoders have gradually become the mainstream encoders in industrial applications.

From a technical point of view, Chinese domestic manufacturers have achieved a comprehensive breakthrough. The magnetic encoder has now developed to 19 bits, reaching the highest level in the industry. It has the advantages of vibration resistance, oil stain resistance, and dust resistance. It has been verified by the mass market and is stable and reliable. In terms of photoelectric encoders, the research and development strategy adopted is the same as that of magnetic encoders, that is, they are made shorter. The 25-bit optical encoder achieves a resolution of 0.038 arc seconds and an accuracy of less than 10 arc seconds. It has the characteristics of high resolution, small speed fluctuations, low speed stability, and high positioning accuracy.


The main difference between optical knitting and magnetic knitting lies in the accuracy. 

The accuracy of optical knitting is better than that of magnetic knitting. Even the current highest 19-bit magnetic knitting can still not meet the accuracy requirements of the industry in some applications. For example, high-precision, high-speed and high-tech industries such as metal engraving and fast die-cutting with track requirements.


At present, some important components such as chips, key magnets and magnetic heads in the encoder still rely on imports. 

This is the main breakthrough goal of the domestic encoder manufacturers in the next stage. Under such circumstances, when an enterprise reaches mass production capacity, its main competitive point is concentrated on the improvement of product technology. For example, in the accuracy design of magnetic and optical knitting, a correction technology is adopted. By adding a correction amount in each certain interval, the cumulative accuracy is corrected, thereby greatly improving the reliability and stability of the product.


In the pursuit of optical knitting design craftsmanship, we have also put a lot of effort into it. 

The main application of optical knitting lies in technical engraving, which requires relatively high power consumption. Nowadays, battery-free multi-turns are being developed to solve the problem of battery energy consumption. For the installation of the motor, a split installation method is adopted for the installation of 100 flanges or less, and a labyrinth-type bearing oil baffle structure is designed. The grease evaporates and automatically returns to the bearing to avoid polluting the code disc and affecting the accuracy; for the motor with 100 flanges or more, It adopts the cross-shaft installation method to absorb shock and buffer, isolate high temperature, prevent movement, prevent oil pollution, and has a high-reliability process guarantee. Of course, many problems were encountered during the development process. For example, the cross shaft has been developed for nearly one and a half to two years, and it has probably solved more than one hundred problems. It looks very simple, but it is quite complicated. Although several domestic companies have the technical strength for mass production of optical knitting, the pursuit of excellence in optical knitting technology is still the next direction to work hard.


In addition, advanced encoder algorithm technology can also effectively improve the overall servo drive performance. 

At present, the development level of drives in China is quite good, but often when motors, encoders and drives are matched and applied, it will affect the overall drive performance. For example, in the past, the performance of magnetic encoders was not enough when they were just starting to develop, which led to greater efforts in the development of drives to improve the overall drive performance. In fact, as long as the number of encoder bits is increased, the drive effect will be better. good. Moreover, on 25-bit optical knitting, a single-stage NS magnetic ring is used to solve the multi-turn problem; the simple pattern of a single track is used to achieve miniaturization while ensuring reliability; after the overall technology is adopted, the performance of the servo system will be greatly improved . We also often discuss that starting from the overall automation solution, the problem will be solved faster, rather than relying on a certain drive or a certain product to solve the problem.


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