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°).
Magnetic encoders are widely used in aerospace technology, robot joints, machine tool turntables, and other equipment applications. Interval misjudgment is a problem that occurs during synthesis of ...multiple interval angles because of the effects of the working environment and the encoder's power supply. This paper proposes an approximate arctangent algorithm based on a combination of table lookup and interpolation to improve the speed at which the arctangent solution is calculated. Finally, a unique angle interval translation decoding method is proposed that can implement mechanical angle synthesis for split magnetic encoders. The algorithm's performance is then confirmed experimentally.
Magnetic encoder, at present, seems widely employed in real-time feedback and dynamic monitoring of servo control systems with closed-loop design. In order to settle the issue that jump points of ...angle value occur possibly as the multipole magnetic encoder crosses the adjacent magnetic poles, the suppression method of jump points based on fuzzy logic (FL) is adopted to realize angle subdivision. Aiming at judging angle values in the fuzzy region, the upper and lower windows for pole number discrimination are established, of which an appropriate window width is screen out by ant colony optimization (ACO). The compensation table is completed by angle error compensation algorithm of dynamic interval division, which is solidified in the microcontroller unit (MCU), eliminating the high-frequency noise of the error table. Finally, the angle value of magnetic encoder is corrected by the lookup table method. The results show that the misjudgment of angle value caused by jump points as the multipole magnetic steel at zero crossing is capable of being suppressed effectively by the proposed method. The resolution and accuracy can reach 0.111° and 0.180°, respectively.
In this paper we outline newly-developed control algorithms, designed to achieve high-precision feedback for a motor control system using a magnetic encoder. The magnetic encoder, combing single-pole ...and multi-pole magnetic steels, was adopted to extend the resolution of the magnetic encoder. First, with a view to settling the issue of the jump points of the multi-pole angle value at the convergence of two adjacent magnetic poles, the angle segmentation method, which uses the window filter discrimination method, is employed to determine the actual angle value. The appropriate filter window width is selected via the improved particle swarm optimization (IPSO) algorithm, and an expanded resolution is achieved. Second, a compensation table is completed via a linear compensation algorithm based on virtual cutting to enhance the accuracy of the combined magnetic encoder. On this basis, a linear difference algorithm is used to achieve deviation correction of the angle. Finally, the jump points can be restrained effectively via the angle segmentation method. The resolution reaches 0.05°, and the accuracy is 0.045°.
In this article, 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 article 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 ±40 LSB (0.014°) and the resolution increased from 2 16 to 2 20 .
To fulfill the requirement of fields such as robotics, aviation, and special machining, motors with quill shafts or outer rotors have been used. For these special motors, the photoelectric encoder's ...volume is normally too big and easy to be polluted by oil or dust; magnetic encoder normally has poor accuracy, and alnico piece may not provide enough magnetic field coverage area. The aim of this essay is to find a new structure of magnetic encoder to improve the precision and magnetic field coverage area. By using two multi-pole alnico rings with a different number of pole pairs to provide a magnetic field, the coverage area could be improved. The position differences between two alnicos pole positions are used to calculate absolute angle value, so the accuracy of the encoder could be absolute and no less than that of a combined magnetic encoder with the same number of pole pairs. A special algorithm is proposed for decoding. This new kind of magnetic encoder could be used on special motors with quill shafts or outer rotors. Its volume and weight are less than the photoelectric encoder and have better performance on antipollution. The alnico ring is easy to modify to suit the structure of the motor.
Purpose
Most of the linear encoders are based on optics. The accuracy and reliability of these encoders are greatly reduced in polluted and noisy environments. Moreover, these encoders have a complex ...structure and large sensor volume and are thus not suited to small application scenarios and do not have universality. This paper aims to present a new absolute magnetic linear encoder, which has a simple structure, small size and wide application range.
Design/methodology/approach
The effect of swing error is analyzed for the sensor structural arrangement. A double-threshold interval algorithm is then proposed to synthesize multiple interval electrical angles into absolute angles and convert them into actual displacement distances.
Findings
The final linear encoder measurement range is 15.57 mm, and the resolution reaches ± 2 µm. The effectiveness of the algorithm is demonstrated experimentally.
Originality/value
The linear encoder has good robustness, and high measurement accuracy, which is suitable for industrial production. The linear encoder has been mass-produced and used in an electric power-assisted braking system.
The accuracy and operational stability of a turntable system can be reduced by the backlash problem that occurs in the reducer's gear transmission system. To solve this problem, this work proposes a ...scheme in which two motors are used to eliminate the effects of backlash through a linearization process. By calculating and outputting two independent torques synchronously from the two servo motors to the system output shaft's gears, a nonlinear system with backlash can be transformed into a linear system without backlash, thus making the resulting system easy to control. Experiments verify that the system will remain stable after the movement of the output shaft stops.
In a permanent magnet synchronous motor (PMSM) control system, usually, the phase voltage instruction is limited independently to prevent a three-phase pulse width modulation (PWM) wave from ...overflowing. This method decreases the efficiency of the bus voltage and causes voltage vector direction errors. To solve these problems, we propose a harmonic injection sinusoidal pulse-width modulation (SPWM). This method uses harmonic injected sinusoidal PWM to improve the utilisation ratio of the bus voltage, and consequently improve system performance. In this paper, we analyse the problem in terms of potential difference. The simulation results show that the proposed method can increase the utilisation ratio of the bus voltage up to 15.4%, and the voltage vector mode obtained with the proposed algorithm is larger than that obtained with the conventional one. The method with harmonic injection consequently improves current response, without affecting voltage vector accuracy. The experiment results validate the proposed method.
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