Abstract
Magnetometers combined with inertial sensors are widely used for orientation estimation, and calibrations are necessary to achieve high accuracy. This paper presents a complete tri-axis magnetometer calibration algorithm with a gyro auxiliary. The magnetic distortions and sensor errors, including the misalignment error between the magnetometer and assembled platform, are compensated after calibration. With the gyro auxiliary, the magnetometer linear interpolation outputs are calculated, and the error parameters are evaluated under linear operations of magnetometer interpolation outputs. The simulation and experiment are performed to illustrate the efficiency of the algorithm. After calibration, the heading errors calculated by magnetometers are reduced to 0.5° (1σ). This calibration algorithm can also be applied to tri-axis accelerometers whose error model is similar to tri-axis magnetometers.
Highlights
Strap-down inertial measurement units (SIMU) which consist of gyroscopes and accelerometers, have been applied to orientation estimation for a long time [1]
In thethe second coefficient matrix and bias error vector are calculated through linear algebra operations of coefficient matrix and matrix bias error vector calculated through linearlinear algebra operations of step, the error coefficient and bias errorare vector are calculated through algebra operations magnetometer interpolation outputs
The calibration errors introduced by the gyro bias, gyro misalignment, non-orthogonality of the cuboid frame, and rotation deviation are analyzed, respectively
Summary
Strap-down inertial measurement units (SIMU) which consist of gyroscopes and accelerometers, have been applied to orientation estimation for a long time [1]. Many stand-alone magnetometer calibration algorithms based on an ellipse-fitting method have been put forward [10,11,12,13,14,15] These algorithms are low-cost and easy to use. The aim of these ellipse-fitting based algorithms is to compensate the magnetometer output data from lying on an ellipsoid to a sphere. The sensor set of the tri-axis magnetometer and the tri-axis gyroscope is mounted into a non-magnetic cuboid frame. The heading errors calculated by magnetometers are reduced to 0.5◦ (1σ) This algorithm requires a cuboid frame to mount the sensor set, which is easy to obtain and inexpensive. Because the error model of tri-axis accelerometers has a similar form to tri-axis magnetometers, this calibration algorithm can be applied to tri-axis accelerometer calibrations
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