New Encoder Based on Grating Eddy-Current with Differential Structure

doi:10.1007/s12204-023-2665-0

Abstract

Abstract: In response to the shortcomings of the common encoders in the industry, of which the photoelectric encoders have a poor anti-interference ability in harsh industrial environments with water, oil, dust, or strong vibrations and the magnetic encoders are too sensitive to magnetic field density, this paper designs a new differential encoder based on the grating eddy-current measurement principle, abbreviated as differential grating eddy-current encoder (DGECE). The grating eddy-current of DGECE consists of a circular array of trapezoidal reflection conductors and 16 trapezoidal coils with a special structure to form a differential relationship, which are respectively located on the code plate and the readout plate designed by a printed circuit board. The differential structure of DGECE corrects the common mode interference and the amplitude distortion due to the assembly to some extent, possesses a certain anti-interference capability, and greatly simplifies the regularization algorithm of the original data. By means of the corresponding readout circuit and demodulation algorithm, the DGECE can convert the periodic impedance variation of 16 coils into an angular output within the 360◦ cycle. Due to its simple manufacturing process and certain interference immunity, DGECE is easy to be integrated and mass-produced as well as applicable in the industrial spindles, especially in robot joints. This paper presents the measurement principle, implementation methods, and results of the experiment of the DGECE. The experimental results show that the accuracy of the DGECE can reach 0.237% and the measurement standard deviation can reach ±0.14 ◦ within 360 ◦ cycle.

Key words: encoder, grating eddy-current, differential structure, angle measurement

摘要： 光电编码器在水、油、灰尘或强烈振动等恶劣工业环境中抗干扰能力差，而磁编码器对磁场强度过于敏感。针对这些缺点，本文设计了一种基于涡流栅测量原理的新型差动结构编码器，简称为差动式涡流栅编码器（DGECE）。DGECE的涡流栅由梯形反射导体组成的圆阵列和16个具有特殊结构的梯形线圈构成差动关系，分别位于由印刷电路板设计的编码盘和读数盘上。DGECE的差动结构在一定程度上修正了共模干扰和由于安装误差产生的幅值失真，具备一定的抗干扰能力，并大大简化了原始数据的正则化算法。通过相应的读出电路和解调算法，DGECE可将16个线圈的周期性阻抗变化转换为360°全量程内的角度输出。由于DGECE的制造工艺简单且具有一定的抗干扰性，因此易于集成和批量生产，并可广泛应用于工业主轴，尤其是机器人关节。本文介绍了DGECE的测量原理、实现方法和实验结果。实验结果表明：DGECE的精度可达0.237%，360°周期内的测量标准偏差可达±0.14°。

关键词: 编码器，涡流栅，差动结构，角度测量

CLC Number:

P204

Zhang Zaiyi, Lv Na, Tao Wei, Zhao Hui. New Encoder Based on Grating Eddy-Current with Differential Structure[J]. J Shanghai Jiaotong Univ Sci, 2025, 30(2): 337-351.

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