Magnetic Position Sensor Research Articles

AC/DC Magnetic Field Sensing Based on a Piezoelectric Polymer and a Fully Printed Planar Spiral Coil.

Additive manufacturing (AM) is emerging as an eco-friendly method for minimizing waste, as the demand for responsive materials in IoT and Industry 4.0 is on the rise. Magnetoactive composites, which are manufactured through AM, facilitate nonintrusive remote sensing and actuation. Printed magnetoelectric composites are an innovative method that utilizes the synergies between magnetic and electric properties. The study of magnetoelectric effects, including the recently validated piezoinductive effect, demonstrates the generation of electric voltage through external AC and DC magnetic fields. This shift in magnetic sensors, utilizing piezoinductive effect of the piezoelectric polymer poly(vinylidene fluoride), PVDF, eliminates the need for magnetic fillers in printed devices, aligning with sustainability principles, essential for the deployment of IoT and Industry 4.0. The achieved sensitivity surpasses other studies by 100 times, showcasing linear outputs for both applied AC and DC magnetic fields. Additionally, the sensor capitalizes on the linear phase shift of the generated signal with an applied DC magnetic field, an unprecedented effect. Thus, this work introduces a remarkable magnetoactive device with a sensitivity of ST = 95.1 ± 0.9 μV Oe-1 mT-1, a significantly improved performance compared to magnetoelectric devices using polymer composites. As a functional proof of concept of the developed system, a magnetic position sensor has been demonstrated.

Single-Track Magnetic Tape Absolute Position Sensor with Self-Adaptivity.

In this study, we demonstrate a single-track magnetic code tape-based absolute position sensor system. Unlike traditional dual-track systems, our method simplifies manufacturing and avoids crosstalk between tracks, offering higher tolerance to alignment errors. The sensing system employs an array of magnetic field sensing elements that recognize the bit sequence encoded on the tape. This approach allows for accurate position determination even when the number of sensing elements is fewer than the number of bits covered, and without the need for specific spacing between sensing elements and bit length. We demonstrate the system's ability to learn and adapt to various magnetic code patterns, including those that are irregular or have been altered. Our method can identify and localize the sensed magnetic field pattern directly within a self-learned magnetic field map, providing robust performance in diverse conditions. This self-adaptive capability enhances operational safety and reliability, as the system can continue functioning even when the magnetic tape is misaligned or has undergone changes.

Dynamic Resonant-Inductive Wireless Power Transfer System for Automated Guided Vehicles with Reduced Number of Position Sensors

This paper deals with the position detection of automated guided vehicles (AGVs) in dynamic resonant-inductive wireless power transfer (WPT) systems. A position detection is necessary to activate the correct transmitting coil. One of the simplest and most effective approaches for a position detection method is to use optical or magnetic position sensors for each coil. However, due to needing a high number of sensors, this technique is relatively expensive. Therefore, an AGV position detection technique based on a reduced number of optical or magnetic sensors (by a factor of two) is proposed. The proposed detection technique was verified experimentally by using a scaled-down prototype of the dynamic WPT system. The proposed approach can be easily implemented by uploading a specific program code to a microcontroller. The microcontroller with the code developed by us was used for processing data from AGV position detection sensors, activating a suitable transmitting coil and controlling an inverter of the dynamic WPT system. As shown by the experiments, due to the proposed approach for the position detection of AGVs and activation of transmitting coils, the number of the position detection sensors is reduced by a factor of two, leading to reductions in the overall cost and level of complexity of the dynamic WPT system without degrading its performance.

Angular Position Sensor Based on Anisotropic Magnetoresistive and Anomalous Nernst Effect

Magnetic position sensors have extensive applications in various industrial sectors and consumer products. However, measuring angles in the full range of 0–360° in a wide field range using a single magnetic sensor remains a challenge. Here, we propose a magnetic position sensor based on a single Wheatstone bridge structure made from a single ferromagnetic layer. By measuring the anisotropic magnetoresistance (AMR) signals from the bridge and two sets of anomalous Nernst effect (ANE) signals from the transverse ports on two perpendicular Wheatstone bridge arms concurrently, we show that it is possible to achieve 0–360° angle detection using a single bridge sensor. The combined use of AMR and ANE signals allows a mean angle error in the range of 0.51–1.05° within a field range of 100 Oe–10,000 Oe to be achieved.

Development of real-time navigation system for laparoscopic hepatectomy using magnetic micro sensor

Background We report a new real-time navigation system for laparoscopic hepatectomy (LH), which resembles a car navigation system. Material and methods Virtual three-dimensional liver and body images were reconstructed using the “New-VES” system, which worked as roadmap during surgery. Several points of the patient’s body were registered in virtual images using a magnetic position sensor (MPS). A magnetic transmitter, corresponding to an artificial satellite, was placed about 40 cm above the patient’s body. Another MPS, corresponding to a GPS antenna, was fixed on the handling part of the laparoscope. Fiducial registration error (FRE, an error between real and virtual lengths) was utilized to evaluate the accuracy of this system. Results Twenty-one patients underwent LH with this system. Mean FRE of the initial five patients was 17.7 mm. Mean FRE of eight patients in whom MDCT was taken using radiological markers for registration of body parts as first improvement, was reduced to 10.2 mm (p = .014). As second improvement, a new MPS as an intraoperative body position sensor was fixed on the right-sided chest wall for automatic correction of postural gap. The preoperative and postoperative mean FREs of 8 patients with both improvements were 11.1 mm and 10.1 mm (p = .250). Conclusions Our system may provide a promising option that virtually guides LH.

Radioulnar Instability and Ulnar Stump Stabilization in Distal Radio Ulnar Joint Arthritis: A Cadaver Study.

Salvage procedures for distal radioulnar joint (DRUJ) arthritis, like the Darrach or Sauvé-Kapandji (S-K) procedures, often result in extensor tendon ruptures at the ulnar stump. Radioulnar instability is considered the underlying cause and stump stabilization techniques are employed. This study investigated radioulnar instability, extensor tendon irritation, and the effectiveness of stump stabilization techniques following salvage procedures. Six upper limbs from three cadavers were used. Forearm rotation was measured using magnetic position sensors to assess radial movement. The Darrach procedure was performed on two limbs, comparing radial motion ranges for different ulnar osteotomy positions. The risk of tendon rupture was assessed with applied weight. The S-K procedure was performed on four limbs, evaluating stump stabilization techniques and radial movement distance underweight. Proximal osteotomy positions increased radial motion range. Extensor tendon irritation occurred when the load was applied to the volar and ulnar sides, particularly with a pronated forearm. Stump stabilization techniques did not significantly contribute to ulnar stump stabilization. Proximal ulnar osteotomy positions in DRUJ salvage procedures led to increased radioulnar instability and potential complications. Load application on the volar and ulnar sides, especially in a pronated forearm, increased the risk of tendon rupture. Stump stabilization techniques showed limited utility in stabilizing the ulnar stump or reducing complications. These findings can inform strategies for minimizing complications in DRUJ salvage procedures.

Development of a method for measuring spleen stiffness by transient elastography using a new device and ultrasound-fusion method.

Hepatic venous pressure gradient (HVPG) is the gold standard index for evaluating portal hypertension; however, measuring HVPG is invasive. Although transient elastography (TE) is the most common procedure for evaluating organ stiffness, accurate measurement of spleen stiffness (SS) is difficult. We developed a device to demonstrate the diagnostic precision of TE and suggest this technique as a valuable new method to measure SS. Of 292 consecutive patients enrolled in this single-centre, translational, cross-sectional study from June through September in 2019, 200 underwent SS measurement (SSM) using an M probe (training set, n = 130; inspection set, n = 70). We performed TE with B-mode imaging using an ultrasound-fusion method, printed new devices with a three-dimensional printer, and attached the magnetic position sensor to the convex and M probes. We evaluated the diagnostic precision of TE to evaluate the risk of esophagogastric varices (EGVs). The median spleen volume was 245 mL (range, 64-1,720 mL), and it took 2 minutes to acquire a B-mode image using the ultrasound-fusion method. The median success rates of TE were 83.3% and 57.6% in patients with and without the new device, respectively (p<0.001); it was 76.9% and 35.0% in patients with and without splenomegaly (<100 mL), respectively (p<0.001). In the prediction of EGVs, the areas under the receiver operating characteristic curve were 0.921 and 0.858 in patients with and without the new device, respectively (p = 0.043). When the new device was attached, the positive and negative likelihood ratios were 3.44 and 0.11, respectively. The cut-off value of SSM was 46.0 kPa. Data that were similar between the validation and training sets were obtained. The SS can be precisely measured using this new device with TE and ultrasound-fusion method. Similarly, we can estimate the bleeding risk due to EGV using this method.

Development and Improvement of Real-Time Navigation System for Laparoscopic Hepatectomy

Introduction: We are going to try development of real-time navigation system for laparoscopic hepatectomy, which resembles a car navigation system. We report our real-time navigation system and surgical procedure. Methods: Virtual images are reconstructed using “New-VES” system developed by Nagoya University Graduate School of Information Science. These images correspond to maps of car navigation system. Some of patient's body parts are registered in virtual images using a magnetic position sensor. Patient's body after registration corresponds to The Earth. A transmitter for magnetic position sensor, which corresponds to an artificial satellite, is placed about 30cm above patient's body. A micro magnetic sensor, which corresponds to GPS antenna, fixes on the handling part of laparoscope.Fiducial registration error (FRE) is utilized to evaluate accuracy of real-time navigation system. Results: We performed laparoscopic hepatectomy using this system in 21 patients. Mean FRE of initial 5 patients was 17.7mm. First improvement was that MDCT were taken using radiological markers for registration of body parts. Mean FRE of the 8 patients who utilized first improvement was 10.2mm and decreased (p = 0.014). Second improvement was that a micro magnetic sensor as an intraoperative body position sensor was fixed on the right-sided chest wall and meant that pre- and post- operative FRE was similar due to an intraoperatively automatic correction of gap of body position. Preoperative and postoperative mean FRE of the 8 patients who utilized second improvement were 11.1mm and 10.1mm (p = 0.250). Conclusions: Our real-time navigation system can assist laparoscopic hepatectomy.

Inductive Position and Speed Sensors.

Magnetic position and speed sensors are rugged and durable. While DC magnetic sensors use permanent magnets as a field source and usually have only mm or cm range, inductive sensors use electromagnetic induction and they may work up to a distance of 20 m. Eddy current inductive sensors equipped with magnetoresistive sensors instead of inductive coils can operate at low frequencies, allowing detection through a conductive wall. In this paper, we make an overview of existing systems and we present new results in eddy current velocity and position measurements. We also present several types of inductive position sensors developed in our laboratories for industrial applications in pneumatic and hydraulic cylinders, underground drilling, large mining machines, and for detecting ferromagnetic objects on conveyors. While the most precise inductive position sensors have a resolution of 10 nm and linearity of 0.2%, precision requirements on the industrial sensors which we develop are less demanding, but they should have large working distance and large resistance to environmental conditions and interference.

Real-time sensor fault detection in Tokamak using different machine learning algorithms

The “Tokamak” is a device that facilitates nuclear fusion between Deuterium and Tritium. Multiple arrays of magnetic sensors are used to detect the plasma position inside a Tokamak. This paper presents the application of different machine learning (ML) based fault detection techniques for the identification and classification of faults that happen in typical magnetic position sensors. The performances of these machine learning based fault detection algorithms are evaluated for two scenarios as follows. Firstly, during the “Self-Test” mode, i.e., before the start-up of the plasma discharge, with known current waveforms in the external coils. Secondly, by using the simulated plasma discharge waveforms. Their performances are compared in terms of computational complexities and latency in view of deciding the best fault detection algorithm. The machine learning techniques are implemented in real-time on the Xilinx Kintex-7 and Xilinx Zync-7 series FPGA. From the obtained comparison results, it is observed that out of the six machine learning approaches, namely Multi-Layer Perceptron (MLP) neural network, K-Nearest Neighbor (KNN), Support Vector Classifier (SVC), Gaussian Naive Bayes (GNB), Decision Tree (DT) and Random Forest classifier (RF) employed for Tokamak sensor fault detection, the Random Forest Classifier based approach was found to be the best in terms of speed and accuracy.

Simulating metallic contamination in permanent magnets used in magnetic sensors

PurposeThe purpose of this paper is to provide a model for simulating contamination by ferromagnetic particles in sensors that use permanent magnets. This topic is especially important for automotive applications, where magnetic sensors are extensively used and where metallic particles are present, particularly because of friction between mechanical parts. The aim of the model is to predict the particle accumulation and its effect on the sensor performance.Design/methodology/approachMagnetostatic moment method is used to calculate particles' magnetization and magnetic field. Magnetic saturation is included and Newton–Raphson method is used to solve the non-linear system. Magnetic force on particles is calculated as a gradient of energy. Dynamic simulation provides the positions of agglomerated particles.FindingsA simulation of magnetic park lock sensor shows a significant impact of ferromagnetic particles on sensor's accuracy. Moreover, gains on computational time because of model optimizations are reported.Research limitations/implicationsOnly magnetic force and gravity are taken into account for particle dynamics. Mechanical forces such as friction and particle interactions might be considered in future works.Practical implicationsThis paper provides the possibility to evaluate and improve magnetic sensor design with respect to particles contamination.Originality/valueThe paper presents a novel simulation tool developed to answer the growing need for reliable and fast prediction of magnetic position sensors’ degradation in the presence of metallic particles.

Design of Linear Magnetic Position Sensor Used in Permanent Magnet Linear Machine With Consideration of Manufacturing Tolerances

This paper proposes the design of a linear magnetic position sensor (LMPS) to detect the mover position of the permanent magnet linear synchronous machines (PMLSMs). The working principle of the LMPS is based on the well-known Hall-Effect. The Hall-Effect-based design of LMPS is considered because it provides a low cost and relatively harsh environment susceptible alternative for the position detection for long track PMLSM system. The initial design was performed using 3D-finite element analysis and genetic algorithm-based deterministic optimization. Based on the initial model, four LMPS were manufactured and tested under the output constraint of peak flux density > 0.1T and total harmonic distortion < 3%. From the test results, it is concluded that the manufactured LMPS suffered significant deviation in output compared to the simulation model. These anomalies arise because of the manufacturing tolerances. To further improve the design and manufacturing process of the LMPS considering the effect of tolerance, a reliability-based robust design optimization (RBRDO) of the LMPS is proposed. The results of RBRDO confirms its usefulness for the design process of the LMPS in terms of undesired design non-compliance cost and great robustness without sacrificing the accuracy of the output signal.

Fully Integrated Magnetic Position Sensor

Fully Integrated Magnetic Position Sensor

Magnetic angular position sensor enabled by spin-orbit torque

We propose a simple scheme for magnetic angular position sensor based on current-induced spin-orbit torque effect. A full range detection of 360° is realized with a pair of Hall crosses made of heavy metal/ferromagnet heterostructures. The current axes of the two Hall crosses are aligned orthogonal to each other, such that when both devices are subject to a rotational in-plane magnetic field, the differential Hall voltage due to current pulses of opposite polarity exhibits a sine and cosine angular dependence on the field direction, respectively. The field rotational angle is then calculated from the sine and cosine output signals via the arctan2 function. A linear correspondence between the calculated and actual field angle is obtained in the field range of 500–2000 Oe, with an average angle error of 0.38°–0.65°.

Laparoscopic ultrasound manipulator with a spring-based elastic mechanism.

Image guidance is a key technology that can improve the outcome of laparoscopic surgery. However, due to the large deformation caused by digestive organs, a computer-aided navigation system based on preoperative imaging data cannot indicate the correct target position of the lesion (e.g., liver tumors and vessels invisible from the organ surface). To overcome this issue, we developed a laparoscopic ultrasound manipulator with two motorized degrees of freedom at the tip, allowing for the performance of a dexterous ultrasound scan in a confined laparoscopic surgical area. The developed manipulator consists of a compact and elastic structure using springs, enabling a safe ultrasound scan and avoiding excess force on the inspected organs. The manipulator is a handheld device equipped with four buttons at the handle, which the surgeon directly grasps to send a motion command to the tip structure. The developed prototype realizes two motorized degree-of-freedom motion at the tip. The size of prototype is 15.0mm in diameter that is usable in conventional laparoscopy. The tip of the manipulator was carefully designed by considering the kinematic model and the results of the finite element analysis. To assess the prototype, accuracy and rigidity were measured by using a motion processing microscope. The accuracy test showed that the proposed device has a fairly accurate characteristic as a handheld device. This was supposedly caused by the nature of compliant mechanism, which does not have mechanical play in motion. In addition, the intrinsic elastic structure (approximately 2.0N/mm in most of the range of motion) allowed the ultrasound probe to adequately fit on the curved organ surface without extra effort of manipulation during the inspection. In the in vivo experiment, the yaw motion was found to be effective for investigating the vascular network because the manipulator allows the probe to be rotated while maintaining the same position. The mechanical evaluation and in vivo test results showed high feasibility of the prototype. We are currently working on further mechanical improvement for commercialization and development of a real-time navigation system that can perform three-dimensional reconstruction of ultrasonographic images by implementing a magnetic position sensor at the tip of the manipulator.

Non-magnetic thin films for magnetic field position sensor

Herein, for the first time, anisotropic magnetotransport phenomenon in amorphous carbon (a-C) thin films has been examined on the basis of Brysksin – Klein (B-K) model. The sign of magnetoresistance turns negative at (θ, ϕ)=(0°, 90°) to positive at (θ, ϕ)=(90°, 90°) where θ and ϕ are the angle between applied magnetic field and normal to the plane and the angle between applied magnetic field and current, respectively. The sign of magnetoresistance of a-C thin films varies continuously at θ=0–360° and ϕ=0–90°, suggesting good potential for the position sensing of large magnetic field.

1B14 食事動作の異常検出に関する基礎的検討

In recent years, people with swallowing disorders (dysphagia) have increased because of an aging population. More than 5,000 people die of asphyxiation each year after consuming solid foods in Japan. This study was conducted to develop an abnormal detection algorithm for a meal, especially the universal choking sign (hands crossed over the throat). In this study, magnetic position and orientation sensors were attached to three anatomical landmarks on the upper body of subjects and were used to measure human motion during a meal. Support vector machine was used for simulated choking sign detection Experimental results demonstrated that the proposed method detected simulated choking signs during a meal with accuracy of 93.7±4.1 %.

A Novel Absolute Magnetic Rotary Sensor

To measure the angular position of motors, robot joints, etc., an absolute magnetic rotary position sensor is developed, which possesses small-size, light, robust, and easy-to-integrate properties. The sensor consists of two inductors, i.e., a code disc and a signal processing part. Both of the two inductors are embedded with a big planar spiral copper coil and four smaller copper coils by employing microelectromechanical system (MEMS) technology, and there are two circles of regular copper sheets listing on the surface of the code disc. In addition, mathematical analyses of the inductor structure as well as the relationships of position and dimension among the coils and the copper sheet are addressed. Finite-element simulation results demonstrate that one group of the optimal sine and cosine signals can be generated by each inductor. Then, the absolute position measurement method is validated by a mathematical method. Finally, experiments are performed on the high-speed and the low-speed testing platforms to assess effectiveness and accuracy of the sensor.

Design of Permanent Magnet Synchronous Motor Rotor Position Detection System Based on TLE5012

Currently, the application of permanent magnet synchronous motor is in a wide range of electric vehicle. Field oriented control algorithm is the main way to control permanent magnet synchronous motor, the magnetic field oriented control must be precise to get the rotational position of the motor. Therefore, the performance of the motor position sensor directly affects the accuracy of the magnetic field oriented control. There are three main kinds of sensors: photoelectric position sensor, magnetic position sensor and magnetic sensor. Due to its superior performance, the application of magnetic position sensors is increasingly widespread. This paper designed permanent magnet synchronous motor position detection circuit for the position of permanent magnet synchronous motor based on TLE5012 used to detect the position and 32-bit micro-controllers Infineon TC1767 used as the main chip.

Development of a Gesture Learning Environment for Novices’ Erhu Bow Strokes

This paper describes the development of a gesture learning environment for a novices’ erhu bow strokes, which diagnoses bow strokes by using magnetic position sensors and feedback errors by showing bow strokes on virtual 3D space and coloring. The system has two windows: bow strokes window for visualization of bow strokes and feedback errors and score window for diagnosing bow strokes along score. In addition, we evaluated the system by Likert scale questionnaire survey. The result of questionnaire indicates that the novice learner was able to recognize and improved errors of bow strokes. It was difficult for novice learners to do that by using conventional method. Moreover, our experiment shows the system useful to learn gesture of bow strokes.