Set Of Magnetic Sensors Research Articles

Vehicle Localization Using Magnetic Markers Incorporating EKF and Maximum Likelihood Estimation

Vehicle localization is an important technical factor in autonomous driving vehicles. Particularly, accurate and precise information about the vehicle position should be obtained, with robustness towards various weather and road conditions. A method using magnetic road markers as coordinate reference points for vehicle localization has proven to achieve the above requirements. However, such method has various limitations. For example, it is unable to localize the vehicle when the vehicle veers off the course of magnetic marker system. This is problematic especially in places where vehicles can take various paths, such as intersections. In this paper, we propose a concept to localize the vehicle using only one set of magnetic sensors, and a novel marker placement method, where markers are placed in a grid-like patterns to enable localization for various paths. To achieve this, extended Kalman filter was used to integrate information from inertial measurement unit with the information from magnetic markers. Maximum likelihood estimation was used to associate the coordinates of detected markers from a known marker coordinate map. Simulation using MATLAB showed that the proposed method is plausible. The proposed localization algorithm was able to correctly associate the marker coordinates and accurately estimate the vehicle position and heading in some conditions. It also suggested that the marker placement pattern could affect the precision of the marker association algorithm.

Fluctuations of the Magnetic Field of Plasma Currents in Uragan-3M Stellarator

At the torsatron-type stellarator Uragan-3M, frequency spectrum and spatial structures of the fluctuations of the poloidal component of the magnetic field in frequency range 0.3–52 kHz, which are caused by the plasma current, are studied with a set of magnetic sensors. The studies were carried out in the microwave heating regime in confining magnetic fields of different strength. The magnetic field fluctuations were studied in weakly and strongly collisional plasmas. Studies showed that the spectrum of the recorded magnetic field fluctuations consists of a relatively narrowband number of frequencies. The fluctuating magnetic fields are caused by plasma currents, which can be presented as a number of poloidal structures with wave numbers m = 0, 1, 2, and 3 (and, possibly, also 4). Each spatial structure of plasma currents (expect the one with m = 0) can be represented as a sum of two oscillation types: a rotating and a standing structure. The rotating structure moves in the poloidal direction with a rotation frequency close to the frequency of the standing structure. The rotation direction is not constant and it changes during the discharge. The standing structure does not change its position (phase) and oscillates at a fixed frequency. The conducted analysis showed that the observed fluctuations of the magnetic field are a result of plasma instabilities, which cause perturbations of the plasma pressure. These oscillations have the growth rate and damping rate of the order of the carrier frequency. The perturbation of the plasma density initiates the appearance of polarization removal currents whose magnetic field is recorded in the described experiments. Estimates show that the fluctuation level reaches 4 × 10–3 relative to the average plasma pressure in the discharge. It was also shown that, in these experiments, microwave heating does no cause the observed instabilities. The time behavior of the discharge parameters and the energy of magnetic field fluctuations at the boundary of the confinement region allows us to conclude that at the quasi stationary stages of the discharge, the observed instabilities determine the main energy losses from the plasma volume.

Automatic Vehicle Model Recognition and Lateral Position Estimation Based on Magnetic Sensors

This paper presents a new approach for automatic vehicle model recognition and simultaneous estimation of lateral transit position, based on magnetic sensor technology. A set of magnetic sensors is deployed on the road surface and, upon transit of a target vehicle on the equipment, the system records six magnetic signatures relative to different vehicle sections. The recorded signatures are then compared with the Dynamic Time Warping algorithm to previously recorded ones, which are relative to known vehicles that have transited at known lateral position; the system then assesses whether the target vehicle’s model matches one of the models already in the database, and estimates its lateral transit position. With the considered experimental set-up, the system is able to discriminate between many different vehicle models and six lateral positions, with a resolution of about $20\,cm$ : the performance of the system is presented by comparing a set of different classifiers. In terms of vehicle model recognition, 1-Nearest Neighbor classifier obtains 0% of misclassification rate, while for lateral position estimation, if an error of one position is tolerated (precision of $\pm \,20\,cm$ ), the system is shown to reach 2.4% of misclassification rate.

Magnetic Hand Tracking for Human-Computer Interface

Hand motion tracking is useful in human-computer interface and many other applications requiring human-machine interactions. In this work, permanent magnets and contactless magnetic sensors are used to track finger motion. A magnet patch is affixed to each fingernail to mark the location and orientation of the fingertip. When fingers move, the combined magnetic fields produced by the magnets at fingertips are recorded by a set of magnetic sensors around a wristband. The recorded data from the sensors are utilized to calculate the magnets' locations and orientations, which can provide estimate of the hand posture based on a geometric hand model.

Isolated word recognition of silent speech using magnetic implants and sensors

There are a number of situations where individuals wish to communicate verbally but are unable to use conventional means—so called ‘silent speech’. These include speakers in noisy and covert situations as well as patients who have lost their voice as a result of a laryngectomy or similar procedure. This paper focuses on those who are unable to speak following a laryngectomy and assesses the possibility of speech recognition based on a magnetic implant/sensors system. Permanent magnets are placed on the tongue and lips and the changes in magnetic field resulting from movement during speech are monitored using a set of magnetic sensors. The sensor signals are compared to sets of pre-recorded templates using the dynamic time warping (DTW) method, and the best match is identified. Experimental trials are reported for subjects with intact larynx, typically using 500–1000 utterances used for speaker dependant training and testing. It is shown that recognition rates of over 90% are achievable for vocabularies of at least 57 isolated words: sufficient to drive command-and-control applications.

Design and performance analysis of ITER ex-vessel magnetic diagnostics

Accurate magnetic diagnostics are essential to perform reliable operation of any tokamak. The ITER magnetic diagnostics include a wide variety of sensors located on the inner and outer surfaces of the vacuum vessel, in the divertor cassettes and in the casing of the toroidal field coils. As the measurement accuracy of the inner set of magnetic sensors might be compromised by various radiation effects and high heat loads, the complementary ex-vessel set is essential to provide backup information. This paper is an overview of the ex-vessel magnetic diagnostic which consists mainly of pick-up coils, steady state sensors, Rogowski coils in the toroidal field coil casing and fibre optic current sensors. The work presented aims at designing these sensors to meet the performance requirements in spite of the constraints due to the tokamak environment. The manufacturing constraints and the positioning requirements for all the ex-vessel magnetic sensors are described. The use and expected accuracy of the entire ex-vessel magnetic diagnostic is assessed in terms of magnetic equilibrium reconstruction and plasma current measurement precision.