Earth Magnetic Field Measurement Research Articles

CubeSat attitude determination with decomposed Kalman filters

CubeSats are the cost-effective entry to space research and applications. As mission requirements increase to carry out more complex tasks, the constraints on the satellite challenge how attitude estimation and control systems are designed. Limited energy, sensors, and computational capacity require compromises. In this paper, we propose a Kalman filter architecture to reduce the computational cost of attitude estimation, leveraging the conditional independence structure of its physical model. Our method decomposes attitude dynamics and kinematics, leading to a linear attitude quaternion and a nonlinear angular velocity filter. As accommodating all vector measurements would require a nonlinear filter, we propose the virtual sensor paradigm that transforms the nonlinear observation model into a linear one, without relying on approximations. Our numerical experiments showcase superior error dynamics and robustness to epistemic uncertainty compared to a nonlinear quaternionic filter, and we also investigate performance against star tracker measurement frequency and sensitivity to the angle between Sun and Earth magnetic field measurements.

Measurement of human rotation behavior for psychological and neuropsychological investigations.

The investigation of rotation behavior in human beings enjoys a longstanding and enduring interest in laterality research. While in animal studies the issue of accurately measuring the number of rotations has been solved and is widely applied in practice, it is still challenging to assess the rotation behavior of humans in daily life. We propose a robust method to assess human rotation behavior based on recordings from a miniature inertial measurement unit that can be worn unobtrusively on a belt. We investigate the effect of different combinations of low-cost sensors-including accelerometers, gyroscopes, and magnetometers-on rotation measurement accuracy, propose a simple calibration procedure, and validate the method on data from a predefined path through and around buildings. Results suggest that a rotation estimation based on the fusion of accelerometer, gyroscope, and magnetometer measurements outperforms methods based solely on earth magnetic field measurements, as proposed in previous studies, by a drop in error rate of up to 32 %. We further show that magnetometer signals do not significantly contribute to measurement accuracy in short-term measurements, and could thus be omitted for improved robustness in environments with magnetic field disturbances. Results also suggest that our simple calibration procedure can compete with more complex approaches and reduce the error rate of the proposed algorithm by up to 38 %.

SMART SILICON SENSOR – MAGNETIC COMPASS ON THE BASE OF A 3-D HALL STRUCTURE

In this paper is discussed some of the trends in the industrial designs of smart sensor systems. High performance sensor systems have been implemented by combining the sensing and signal processing functions on the same chip. A very promising magnetic compass for Earth magnetic field measurement is created on the base of a 3-D Hall structure.

3D Magnetic Field Sensor Concept for Use in Inertial Measurement Units (IMUs)

We report on the design, fabrication, and characterization of a microfabricated 3D magnetic field sensor that is suitable for co-integration with inertial sensors to form single-chip inertial measurement units. In contrast to classical resonant MEMS magnetometers, which are based on Lorentz force measurement, our sensor uses permanent magnetic materials and piezoresistive detection with silicon strain gauges of nanometric section, leading to low power consumption and high sensitivity for small sensor size. Thin multilayers of CoFe and PtMn as ferro- and antiferromagnetic materials are integrated within the MEMS fabrication process. Sensitivities of 1.09 V/T for x- and y- components of the magnetic field and 0.124 V/T for z- component of the magnetic field were measured, respectively. To be sensitive to magnetic fields along all three spatial directions, two permanent magnetization directions on the same die are required. Implementation of the two magnetization directions was validated by a measured correlation of 99.7% between x- and y- sensitivity axes. Power consumption of the 3D sensor is for polarization with a 100 μA dc current. With resolutions of 100 nT/√Hz for x- and y-component of the magnetic field and 350 nT/√Hz for z- component, the sensor is suitable for precise measurement of earth magnetic field.

Multi-Magnetometer Based Perturbation Mitigation for Indoor Orientation Estimation

: Determining orientation with respect to a known reference plays an important role in almost all modes of navigation. As the sensors required for measuring magnetic field have found their way into portable navigation devices, researchers have started investigating their application to orientation estimation in different environments. Nevertheless, the success of these sensors for orientation estimation is conditioned by their capacity to sense Earth's magnetic field in environments full of magnetic anomalies like urban canyons and indoors. These artificial fields contaminate Earth's magnetic field measurements, making orientation estimation very difficult in heavily perturbed areas. To overcome the effect of magnetic anomalies, a perturbation mitigation technique is proposed that utilizes multiple magnetometers. This mitigation technique is then used for estimating Earth's magnetic field indoors thus providing users with better magnetic orientation estimates. Performance of the proposed mitigation technique is assessed for pedestrian navigation in a shopping mall.

CRENEGON Project and its impact on magnetic observations in NIS countries

Critical changes in magnetic observations in Russia were connected with the project initiated by Russian, Ukrainian, and West European magnetologists in the late 1990ties. This project named CRENEGON (Creation of a Renewed Network of basic Geomagnetic Observatories of NIS countries) allowed to five NIS observatories to join INTERMAGNET. This presentation gives a short historical sketch of the Earth's magnetic field measurements in the Soviet Union and NIS countries since the IGY-1957. A role of cooperation with European magnetologist community in recovering observations is discussed. Problems of providing high-quality magnetic measurements at modern observatories are considered. Final part of the report presents proposals for deployment of national network of magnetic monitoring. The work was supported by RFBR grants 10-05-00661 and 11-05-00906.

A 2D micro-fluxgate earth magnetic field measurement systems with fully automated acquisition setup

In this paper we present an Earth magnetic field measurement system and an automated acquisition setup to characterize it. The measurement system consists of a fluxgate sensor and an integrated front-end circuit, both realized in CMOS technology. The couple of orthogonal axes of the sensor makes the system suitable for realizing an electronic compass device. Indeed, we can measure not only the amplitude of the Earth magnetic field (whose full-scale value is of the order of 60 μT), but also its direction. The complete measurement system achieves a maximum angular error of 1.5° in the measurement of the Earth magnetic field direction. Furthermore, an acquisition setup was developed to evaluate the measurement system performance. It consists of a precision mechanical plastic structure, in tower form, a microcontroller-based interface circuit, that provides a digital output through an RS232 serial interface, a PC software suitably developed to post-process the data from the acquisition system and a couple of Helmholtz coils to evaluate the linearity of the system. This setup allows us to perform a completely automated and numerically controlled characterization of the measurement system.

He 3 maser for earth magnetic field measurement

We describe the realization of a He3 Maser operating as an Earth magnetic field magnetometer. Preliminary experiments in order to optimize the device are first presented and finally the He3 Maser is used in the Earth magnetic field and compared with a He4 magnetometer.

Monolithic piezoresistive CMOS magnetic field sensors

Abstract Two original electromechanical magnetic sensors have been developed using a fully industrial fabrication process that relies on bulk wet etching of CMOS dies. The first device uses the Lorentz force to actuate a U-shaped cantilever beam, while piezoresistive polysilicon gauges convert the beam bending into an electrical signal. A 2 μT sensor resolution is demonstrated, making this device suitable for earth magnetic field measurement. The second prospective device uses a ferromagnetic material deposited on top of a free standing mechanical frame. Such approach leads to the design of a passive sensor that does not require any electrical power for actuation.

Integrated vector sensor and magnetic compass using a novel 3D Hall structure

A new 3D silicon vector sensor using the Hall effect principle is realized and characterized. This microtransducer functionally integrates in a common sensor region two parallel-field Hall devices for the in-plane components of the magnetic field and one orthogonal Hall magnetic field version for the perpendicular to the chip. The advantages of this microtransducer are its very low channel cross-sensitivities about three orders of magnitude lower than the respective channel sensitivities, simultaneous on line 3D measurement at equal voltage surface conditions by separate differential current outputs and high spatial resolution 250 μm×220 μm×100 μm. A very promising magnetic compass for Earth magnetic field measurement is created and tested on the base of this 3D Hall structure using ferrite flux concentrators and liquid nitrogen temperature T=77 K.

Crest of the Mid-Atlantic Ridge at 26°N

A relatively detailed investigation of the Mid-Atlantic Ridge crest at 26°N was conducted by using narrow-beam bathymetric data, total earth's magnetic field measurements, and underwater photographs. The Mid-Atlantic Ridge crest at 26°N appears to be hydrothermally active. The structural setting of this area is conducive to the occurrence of hydrothermal deposits. The walls of the rift valley are extensively faulted with blocks and steps ranging in size from kilometers to meters in width and relief. Underwater photographs show hydrothermal manganese associated with interpreted fault steps at depths between 3100 and 2500 m on the east wall, suggesting that the faults provide avenues for hydrothermal fluids. Small topographic highs in the floor of the rift valley are the sites of relatively recent volcanism and are believed to represent the top of an active dike emplacement zone. Bathymetric trend directions for this portion of the ridge crest are complex in comparison with plate rotation predicted trends for the Mid-Atlantic Ridge. The bathymetric grain is a function of processes active in the rift valley.

AN EXPERIMENTAL STUDY OF PROTON FREE PRECESSION IN A WEAK MAGNETIC FIELD AND ITS APPLICATION TO FIELD WORK

A Packard-Varian type experiment was done, in which the free precession of proton magnetic moment about a very weak magnetic field was observed, by first lining up the protons in an aqueous sample with a separate magnetic field and then allowing them to execute the free precession. In out experiment the studies on the non-adiabatic process of withdrawing the polarizing field, the absolute value of the signal strength and the reduction of sample size to minimize the effect of inhomogeneity of the magnetic field were emphasized. The effect of rotating the sample coil upon the measured signal frequency was also noted, and it is pointed out that this is the most direct way to determine the sign of the nuclear magnetic moment.The phenomenon of proton free precession in weak magnetic field has important practical applications in earth's magnetic field measurement at high altitudes, in geological prospecting, and in petroleum recovery from oilfield rocks. The present studies may be helpful in solving the problems likely to occur in these applications.In order to check the performance of the entire experimental set-up for field works, and especially to investigate the influence of magnetic substances in surroundings on the signal frequency, a series of experiments was carried out on a lake. Affirmative results were obtained. The relative accuracy of the measurement of the precessional signal frequency, which in turn determines the magnetic field strength, is 1×10 -5 .