Purpose: To eliminate the angle deviation of magnetic encoder, this paper aims to propose a compensation method based on permanent magnet synchronous motor (PMSM) sensorless control. The paper also describes the experiments performed to verify the validity of this proposed method. Design/methodology/approach: The proposed method uses PMSM sensorless control method to get high precision virtual angle value, and then get the deviation value between virtual position and magnetic angle which is used as compensation table. Oversampling linear interpolation tabulation method has been proposed to eliminate the noise signals. Finally, a magnetic encoder with precision (repeatability) 0.09° and unidirectional motion precision 0.03 is realized. The control system with an encoder running at 14,000 and 0.01 r/min showing high motion resolution is also realized. Findings: Higher value of current in PMSM leads to a magnetic encoder with higher precision. When using oversampling linear interpolation to tabulate the compensation table, it is understood that more oversampling does not lead to a better result. Finally, validated by experiments, using eight intervals to calculate the mean value of angle deviation leads to the best result. Practical implications: The angle deviation compensation method proposed in this paper has a great practical implication and a good commercial application. The method proposed in this paper could be effectively used to self-correct the magnetic encoder using arctangent method and also correct any rotary encoder sensor. Originality/value: This paper originally proposes an adaptive correction method for a rotary encoder based on PMSM sensorless control. To eliminate the noise signals in an angle compensation table, over-sampling linear interpolation tabulation method has been proposed which also guarantees the precision of the compensation table.

To solve the problem of difficulty in the accurate judgment of the zero-crossing position of multi-pole angle value in multi-pole magnetic encoder and then the angle value jumps, this article proposes an angle subdivision method for multi-pole magnetic encoder based on pole number quotient remainder. Firstly, the multi-loop angle data of the magnetic encoder are collected and sorted, and 16 fuzzy multi-pole angle zero-crossing boundaries are obtained. According to the boundary, 32 boundary range values are obtained. The remainder and quotient are calculated according to the boundary range value and are used as the judgment basis of pole pair of the current multi-pole angle value. When the remainder number is 0, the current quotient value can be directly used as the pole number. If the remainder number is not 0, it is necessary to judge the pole number according to the specific range of multi-pole angle values. This method effectively solves the problem of multi-pole number judgment error caused by angle noise of magnetic encoder, and effectively improves the resolution of the magnetic encoder. Experiments show that the multi-pole magnetic encoder with the proposed method can effectively suppress the angle jump caused by the calculation error. Finally, the accuracy of the multi-pole magnetic encoder proposed in this article can reach 11 bits (±0.165°).

In this paper, a simple end face type magnetic encoder has been designed. This paper analyzed the negative effect caused by the calculation method based on the arctangent arithmetic. In addition, the negative effects caused by mechanical installation are illustrated in this paper. In order to solve these problems, a angle error compensation tabulation method has been proposed, and cross-intervals linear interpolation method has been presented to eliminate the noise signal in angle compensation table. The validity of the method proposed in this paper has been verified by experimental and simulation results. The precision of this kind of magnetic encoder could reach 0.02°.

In this paper, a magnetic encoder consisting of single-pole magnetic steel and multi-pole magnetic steel has been proposed. In order to solve the problem of multi-pole angle jump point caused by signal noise, a dynamic multi-window angle pole number prediction algorithms has been put forward, which eliminates the error of angle pole number judgment and improves the resolution effectively. In order to improve the precision of angle value after subdivision, over-sampling linear interpolation tabulation method has been proposed. The method which is put forward in this paper is able to enhance the precision of multi-pole angle value and eliminate the jump points in subdivision process. The resolution of the magnetic encoder obtained by this method could be improved, and it is well applied in motor control. At last, the accuracy of the magnetic encoder is ±40LSB (0.014°) and the resolution increased from 216 to 220.