Magnetic Encoder Research Articles

Hall Sensor Magnetic Encoder Design based on Fault Detection Algorithm

Hall Sensor Magnetic Encoder Design based on Fault Detection Algorithm

Research on Closed-loop Control of Step Motor Based on Magnetic Encoder

Stepper motor is an actuator for converting electric pulse signal into angular displacement, which is characterized by no cumulative error, low mature price and good stability, which is widely used in various industrial environments. However, its disadvantage is also very obvious, that is, can only open loop control, the motor can only passively rotate according to the signal and cannot effectively feedback control.If closed-loop control is required, servo motors with higher price and larger volume are required. In order to solve this problem, this paper refits the stepping motor with the help of the characteristics of the magnetic encoder, so as to realize the closed-loop control of the stepping motor.

Research on The Accuracy Improvement Method of Angle Encoder based on Kalman Filter

In order to improve the accuracy of the magnetic encoder, this paper analyzes the noise characteristics in output signal of magnetic Angle encoder in the real environment, a magnetic encoder based on Kalman Filter (KF) is proposed to solve the problem of random noise which affects the precision of magnetic encoder. The state equation based on the circular motion model is established, and the real-time voltage values of the two output signals are obtained under constant speed rotation of the motor, the angle errors calculated by the voltage signals before and after KF are compared and analyzed. The results show that the scheme can effectively reduce the random noise and improve the Angle accuracy by more than 50% at constant rotation speed. It is proved that the scheme is feasible in industry.

Magnetization System for Spindle Axial Thermal Elongation Measurements

Due to friction between components, significant amount of wasted energy is inevitably generated inside a rotary machine during operation. Such wasted energy is commonly in the form of thermal energy that is transferred to machine components through heat conduction, causing the components to expand in geometry. The amount of change also directly affects the machine’s processing accuracy. The study presented in this article aims to use a magnetic encoder and a magnetoresistive (MR) sensor to build a measurement system that can be directly embedded into a high-speed motor to monitor thermal elongation of the motor’s rotating shaft in axial direction. CoMnP is used as magnetic coating on which novel magnetic polarity patterns are magnetized incrementally along the shaft’s axis by utilizing permanent magnet. The proposed system discussed herein this article is designed to determine proper installation specifications and to examine the assembly tolerance, including the pitch, yaw, row, and flying height errors of the MR in a rotating machine. The results demonstrate that the measurement system senses with a 2 kHz sampling rate can real-time monitor the shaft’s thermal elongation while it rotates with high speed from 1000 to 24 000 r/min. Moreover, compared with a commercial product, the measurement system is found to be feasible to provide accurate the shaft’s thermal elongation values with satisfactory accuracy error.

Дослідження методів стабілізації відео та будови гіростабілізованих підвісів відеокамер для безпілотних літальних пристроїв

The goal of this paper was to research the construction of gyro-stabilized video camera suspensions for drones used for mechanical video stabilization during video monitoring or aerial exploration. The quality of the image received from the drone depends on the quality of the video stabilization, and therefore the amount of useful information received. There are two main groups of video stabilization methods: optical-mechanical and digital stabilization. In order to maximize the quality of the image from the video camera of the unmanned aerial vehicle and to minimize the effects of camera shake, it is necessary to first perform mechanical-optical video stabilization, and then, if necessary, supplement it with digital stabilization. Only digital stabilization without mechano-optical is performed only for the purpose of making the drone cheaper. Optical-mechanical stabilization is usually based on gyroscope readings. In this work, comparative research of the following methods of mechanical stabilization of video from drones was conducted: based on 3-axis and 2-axis gyro-stabilized suspensions with one microcontroller and based on gyro-stabilized suspensions with encoders and several microcontrollers. Mechanical stabilization, in addition to leveling the position of the camera when maneuvering the drone, allows you to turn the camera to a convenient viewing angle for the operator of a drone. 2-axis and 3-axis suspensions with one microcontroller have become the most popular because of their convenience and practicality. 1-axis suspensions or rigidly fixed cameras are used less often. Rigidly fixed cameras are used as course guides for orientation in space by the operator of a drone. That is, such a camera makes it possible to understand the deviation of the drone from the horizon and to adjust the command to the operator for correct flight. Rigid cameras are also used on drones for drone racing competitions. A modular system based on magnetic encoders and several microcontrollers is just beginning to develop, but such a system has a number of advantages, although it is more complicated and expensive. The system provides high accuracy and reliability of stabilization. Each module of the system performs its task. In this way, the resources of microcontrollers are distributed. But its main feature is maintaining the position of the axis rotors relative to the encoder readings. This makes it possible to react very precisely to dynamic actions on the system during active maneuvering of the drone.

Computational Reduction in Look-up Table for Eccentric Magnetic Absolute Encoder

Computational Reduction in Look-up Table for Eccentric Magnetic Absolute Encoder

A Proposal for Reducing the Number of Sensors in a Magnetic Force Differential Type Magnetic Encoder

A Proposal for Reducing the Number of Sensors in a Magnetic Force Differential Type Magnetic Encoder

Health Indicators to Estimate Health of Magnetic Wheel Encoder

Performance of several vehicle safety features, such as anti-lock brake system (ABS), traction control system (TCS) and electronic stability control (ESC) rely on the quality of wheel speed signal. One potential failure mode for the wheel speed encoders is gradual deposition of foreign paramagnetic debris on the surface of the encoder. This results in reduced strength of the magnetic field, and impacts the quality of the wheel speed signal. Noisy wheel speed signal jeopardizes performance of safety critical features, affecting safety, stability, drivability, and negatively impacts customer’s experience.
 In this paper, several faulty encoders with various levels of faults have been used in data collection in a test bench. A prognostics methodology is proposed to evaluate the magnetic wheel encoder’s health. This method leverages time domain and frequency domain-based health indicators to monitor the deterioration in wheel encoder. Time domain-based health indicators include VDA (Verband der Automobilindustrie) signals that are generated by advanced wheel speed sensors, and an enveloping filter of the wheel speed signal’s noise. Frequency domain-based health indicator include root mean square amplitude of average order spectrum of wheel speed noise. The performance of individual/combination of these health indicators are compared to assess the separation between healthy encoder and degraded encoders. Results indicate that it is possible to monitor the degradation process due to magnetic debris accumulation, using the proposed method.

Research on Angle Subdivision Method of Multi-Pole Magnetic Encoder Based on Pole Number Quotient Remainder

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°).

High precision zero-friction magnetic dendrometer

Increasing agricultural demand for freshwater in the face of a changing climate requires improved irrigation management to maximize resource efficiency. Soil water deficits can significantly reduce plant growth and development, directly impacting crop quantity and quality. Dendrometers are a plant-based tool that have shown potential to improve irrigation management in high-value woody perennial crops (e.g., trees and vines). A dendrometer continuously measures small fluctuations in stem diameter; this has been directly correlated to water stress measurements using traditional methods. While plant-based measures of water deficits are considered to be the best measures of water stress, current dendrometer methods are imprecise due to mechanical hysteresis and thermal expansion. The high-precision dendrometer created at the OPEnS Lab alleviates these key failure points using zero-thermal expansion carbon fiber, zero friction via a spring tensioning approach, and a linear magnetic encoder. In-lab tests and field deployments have validated device measurements and the execution of these pivotal qualities. Mass deployment of these automated dendrometers has the potential to provide a continuous record of water stress, providing valuable decision support for irrigation management.

Neural network compensation method for improving detection accuracy of rotor position from magnetic encoder

With the advantages of low cost, small size and high resolution, the magnetic encoder is suitable for permanent magnet synchronous motor. However, due to the installation accuracy and the motor vibration, the rotor position error from magnetic encoder can seriously impact the performance of the motor. Therefore, it is necessary to reduce the detection error of the rotor position from the encoder. In this letter, a new rotor position detection method is proposed based on neural network. The characteristic of the position error from magnetic encoder is analysed, and the backpropagation neural network is presented to obtain the error compensation function. On the basis of the compensation function, the rotor position error can be corrected and thus the precise rotor position can be detected. The experimental results show that not only the rotor position error but also the related total harmonic distortion of the phase current and the torque ripple can be reduced effectively.

Improving the Angular Velocity Measured with a Low-Cost Magnetic Rotary Encoder Attached to a Brushed DC Motor by Compensating Magnet and Hall-Effect Sensor Misalignments.

This paper proposes a method to improve the angular velocity measured by a low-cost magnetic rotary encoder attached to a brushed direct current (DC) motor. The low-cost magnetic rotary encoder used in brushed DC motors use to have a small magnetic ring attached to the rotational axis and one or more fixed Hall-effect sensors next to the magnet. Then, the Hall-effect sensors provide digital pulses with a duration and frequency proportional to the angular rotational velocity of the shaft of the encoder. The drawback of this mass produced rotary encoder is that any structural misalignment between the rotating magnetic field and the Hall-effect sensors produces asymmetric pulses that reduces the precision of the estimation of the angular velocity. The hypothesis of this paper is that the information provided by this low-cost magnetic rotary encoder can be processed and improved in order to obtain an accurate and precise estimation of the angular rotational velocity. The methodology proposed has been validated in four compact motorizations obtaining a reduction in the ripple of the estimation of the angular rotational velocity of: 4.93%, 59.43%, 76.49%, and 86.75%. This improvement has the advantage that it does not add time delays and does not increases the overall cost of the rotary encoder. These results showed the real dimension of this structural misalignment problem and the great improvement in precision that can be achieved.

Modern Displacement Measuring Systems Used in Geotechnical Laboratories: Advantages and Disadvantages.

The paper presents the contemporary displacement measurement systems used in geotechnical laboratories during the determination of soil precise mechanical parameters, e.g., the shear modules G: initial and in the range of small and very small strains. In the laboratory, researchers use standard sensors for measuring deformation, pressure, and force as well as modern measuring systems such as linear variable differential transformers (LVDT), proximity transducers (PT), magnetic encoder sensors with fiber Bragg grating (FBG), or methods based on laser or X-ray measurement. None of the measurements are universal and their use depends on the type of soil (cohesive, non-cohesive), its condition (loose or dense, stiff or very soft), and its characteristic properties (e.g., organic soil, swelling soil). This study points out the interesting equipment solutions and presents the guidelines for selecting appropriate methods of deformation measurement.

Double Dynamic Multi-Window Interval Prediction Angle Segmentation Method for Multi-Pole Magnetic Encoder

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 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">16</sup> to 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sup> .

A New Kind of Absolute Magnetic Encoder.

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.

Implementation of Embedded Magnetic Encoder for Rotor Position Detection Based on Arbitrary Phase-Shift Phase-Lock Loop

Rotor position is essential in control of permanent magnet synchronous motors (PMSMs). In terms of resolution, structural complexity, occupied volume, anti-interference ability, environmental adaptability, and cost, embedded magnetic encoder based on linear Halls owns strong competitiveness. When linear Hall sensors are selectively installed at stator slot openings in extremely compact scenario, signal phase-shift asymmetry between two or three Hall sensors is inevitable. Conventionally, prefilter synchronous reference frame-phase-locked loops exhibit excellent phase-lock ability at fixed frequency (50/60Hz), but become ill when frequency changes especially at zero frequency. In this article, a novel transformation matrix is derived to map the asymmetric phase-shift signals onto two-phase stationary coordinate system. Then, an arbitrary phase shift-phase-locked loop is formed by replacing <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Clark</i> transformation with the proposed transformation matrix, which can accurately extract rotor position and speed information in a simple and effective way, avoiding the utilization of complex notch filter. Simulations in continuous domain based on MATLAB and experiments in discrete domain based on an 18-slot/20-pole prototyped PMSM both confirm the effectiveness of the proposed method.

An autonomous positioning method for fire robots with multi-source sensors

The present technology, based on laser and visual SLAM navigation and positioning, does not apply to the event of a fire in a room where there is a large amount of smoke, for its increasingly obvious defects. In addition, traditional track deduction technology based on photoelectric encoder has accumulated error, and noise disturbance exists in the INS inertial navigation measurement technology, and the UWB positioning technology is vulnerable to NLOS disturbance caused by site occlusion. To solve the problem of accurate positioning of Autonomous Mobile fire-fighting robot in smoke scenes, the system design is optimized by adopting the following methods: using IMU-assisted residual chi-square criterion to detect whether there is NLOS in UWB, introducing IMU instantaneous compensation positioning data and adopting Chan algorithm fitting of the second multiplication to ensure the stability and accuracy of UWB data; meanwhile, a tight combination model of navigation and positioning is designed: via the improved Kalman filter algorithm, fused with the magnetic encoder track estimation pose, UWB absolute and IMU heading angle pose to realize the accurate positioning of the fire robot in the smoke scene. Finally, the fusion simulation model and algorithm are verified by MATLAB, as it shows, the method has an average positioning accuracy of 98.63% in the X-axis direction, 99.52% in the Y-axis direction, and 97.24% in the heading angle, which solves the inherent physical defects of a single positioning sensor and serves as a reliable and accurate solution for indoor robot positioning.

Verification of the Usefulness of Eccentric Structure in the Magnetic Encoders Using a Multipole Magnet

Verification of the Usefulness of Eccentric Structure in the Magnetic Encoders Using a Multipole Magnet

Effects of assembly errors on axial positioning accuracy for rotating machinery with magnetoresistance-based magnetic encoders

Effects of assembly errors on axial positioning accuracy for rotating machinery with magnetoresistance-based magnetic encoders

A Linear Compensation Method for Improving the Accuracy of an Absolute Multipolar Magnetic Encoder

This paper proposes a linear compensator algorithm to improve the performance of an absolute multipolar magnetic encoder (AMPME). An AMPME is an absolute magnetic rotary encoder that uses a multipolar magnet (MPM) to increase the resolution. The resolution can be dramatically increased in proportion to the number of poles in the MPM. However, various hardware problems that occur during the encoder manufacturing process degrade the AMPME performance. Also, harmonic components occur in the raw data due to various problems, such as the resistance error of the analog circuit, magnetic field overlap between the magnets, position error between the sensor and magnet, and pole-pitch difference. In particular, during the magnetization process of the MPM, the pole-pitch difference becomes a problem when the sizes of each pole are not uniform. This problem causes harmonic components that reduce the absolute position accuracy. To solve these problems, this paper proposes a linear compensation method. The proposed linear compensator consists of two parts. The first part is the enhanced ratiometric linearization for phase calculation and calibration. The second is the phase compensator for removing the phase difference via the pole-pitch difference of the MPM. The linear compensator improves various parameters by precomputing the offset, amplitude, and phase corrections. After compensating for sinusoidal signals, the linear compensator applies appropriate parameters at the appropriate times. This method is faster, easier to set up, and more accurate than the conventional method. Furthermore, this method is experimentally verified against the existing harmonic rejection method. Experimental results are provided to verify the effectiveness of the proposed method.