On Misalignment Between Magnetometer and Inertial Sensors

Abstract

Magnetometer, gyroscope and accelerometer are commonly used sensors in a variety of applications. In addition to sensor's physical imperfection, magnetometer's parameters are also affected by magnetic disturbance. Specifically, the soft-iron magnetic effect not only changes its intrinsic model parameters including the scale factor, orthogonality matrix and bias, but also its relative misalignment with respect to other sensors, like inertial sensors of interest in this paper. Almost all existing methods rely on the local gravity information for cross-sensor calibration, thus requiring to collect accelerometer measurements at static positions. Based on the rationale that in a homogenous magnetic field the magnetometer's measurement variation is exclusively induced by orientation change, this paper proposes a novel magnetometer-inertial sensor misalignment estimation algorithm requiring no local gravity information.Founded on a constrained optimization, the algorithm is recursive in time with self-initialization and is also capable of estimating the gyroscope bias as an added benefit. Field test results show that the proposed algorithm has quite good estimation accuracy. As it is inherently immune to any acceleration disturbance, the test equipment does not have to keep still for effective measurement.Index Terms-Magnetometer, gyroscope bias, accelerometer, misalignment, soft-iron magnetic effect

A Portable Support Attitude Sensing System for Accurate Attitude Estimation of Hydraulic Support Based on Unscented Kalman Filter

“…Scientific research is not limited to sensor applications [ 19 ], but also includes the performance of IMUs [ 20 ]. The performance improvement and calibration analysis of IMU provide precise attitude estimation technologies for its application [ 21 ], such as the method of improving estimation performance based of sine rotation vector; the acceleration and magnetic field measurements are transformed into the differences between the Euler angles of the measured attitude and the predicted attitude to correct the predicted attitude [ 22 ]. However, the measurement accuracy and performance of these low-cost MEMS inertial measurement units are easily limited by the complex working environment [ 23 , 24 ], especially the automatic coal mining working face with complex magnetic interference produced by coal structure and high-power electromechanical equipment.…”

Real-Time Calibration of Magnetometers Using the RLS/ML Algorithm

“…In the second category, the magnetometer calibration is performed with assistance from inertial sensors [18][19][20][21][22][23]. This approach has the advantage that it can perform an alignment estimation of the sensor axes between the inertial sensors and the magnetometer.…”

Accelerometer and Magnetometer Joint Calibration and Axes Alignment

“…This gives rise to the need of alignment between their sensitivity axes. The authors in [15,16] use a gyroscope to align the axes of an accelerometer and a magnetometer. The authors in [17,18] exploit the fact that the measured magnetic inclination angle should be locally constant across different measurements when the accelerometer is still and the magnetometer is away of magnetic disturbances in order to align the axes of the two sensors.…”