Research On The Calibration Method Of Inertial/Geomagnetic Integrated Measurement System

With the development of Micro-electromechanical Systems (MEMS) technologies,the research and application of Tri-axial Inertial/Geomagnetic Integrated MeasurementSystem (TIGIMS) based on low cost MEMS inertial sensors and Magnetometers havebeen attractive. In this paper, in order to improve the measurement accurate of TIGIMS,the errors models are developed, a novel calibration method for the whole system isproposed. Simulation and experimental results are presented that validate the proposedmethod and quantify its accuracy. The following work has been completed in thisresearch:1. Based on the self-errosr and working environment of MEMS accelerometers,digital magnetometers, MEMS gyroscopes, the error model of accelerometers,magnetometers and gyroscopes are buliding including the installing errors. This is thefoundation of later calibration and compensation.2. Depended on the Earth’s gravity as a stable physical calibration standard, amulti-position calibration method is designed. The accelerometers errors are estimatedby least square method with the outputs of the accelerometer and the local gravity.Different from the traditional calibration method, this method allows the accelerometersto be calibrated without external equipment, such as a turntable, which reduces the costof calibration.3. Aiming at estimating the mounting error angles, which is a drawback ofmulti-position calibration method, a dot product invariance method is proposed. First,part of the magnetometers errors are calibrated by the multi-position calibration method.And then employs the invariance of two constant vectors’ dot product such as the dotproduct between gravity and magnetic field vector, the magnetometers are easilycalibrated without external equipment.4. A new calibration method based on attitude matching for tri-axial gyroscopesmeasurement system is proposed. First, the attitude error equations are establishedaccording to error propagation characteristics of the gyroscopes when in navigationstate. And then, using the difference between the compensated outputs of theaccelerometers, the magnetometers, and the attitude integration computed of gravityvector, geomagnetic vector as the observation information, the results including thezero-bias, scale factor, non-orthogonalities and mounting error angles of gyroscopessare obtained with a Kalman filter estimator.5. The arrangement of calibration position and rotating scheme is designed dependon the observability analysis of system errors. The arrangement constrained ofcalibration position and rotating scheme is carried out based on the experimentcondition and the frame of instrument. The observability under different arrangement of calibration is analyzed by the theory of PWCS and the singular value decompositionmethod. With the analytic results, one arrangement of calibration position and rotatingscheme is also designed.6. Through the calibration experiment of a set of tri-axial inertial/geomagneticmeasurement system, the method proposed in this paper is test to be effective. In theexperiment the zero-bias, scale factor, non-orthogonalities and mounting error anglesalignments of accelerometers, magnetometers and gyroscopes are obtained. Using thecalibration result, the outputs are compensated, and the navigation algorithm isimplemented to verify the calibration results. Comparing the compensated results andthe uncompensated results, it indicates that the output errors are smaller than before.Furthermore, the calibration method is valid way to improve the measurement accuracyof the TIGMS.