Automatic calibration of a three-axis magnetic compass

Claims

We claim:

1. A method for determining a distortion corrected magnetic heading comprising the steps: acquiring a first set of data from two or more magnetometers and a second set of data from oneor more means for gravity field strength sensing within a predetermined time period in a first orientation; processing the first set of data with a first digital filter; processing the second set of data with a second digital filter; compensating thefirst set of data with a first temperature compensation algorithm; compensating the second set of data with a second temperature compensation algorithm; generating a first filtered signal by processing the first filtered set of data with a firstnonlinear function whose coefficients are predetermined; generating a second filtered signal by processing the second filtered set of data with a second nonlinear function whose coefficients are predetermined; and calculating a heading orientation fromthe first and second filtered signals, wherein a multiplicity of the first and second data sets are acquired in a multiplicity of orientations for the determining, such that the accuracy of the distortion correction improves as additional first andsecond data sets are acquired and wherein the acquiring, the processing, the compensating, the generating, the calculating and the determining are continuously ongoing.

2. A method for determining a distortion corrected magnetic heading as in claim 1 further comprising the steps: calculating a pitch and roll orientation from said second filtered signal; generating a third data set by processing said firstfiltered signal and said second filtered signal; calculating a tilt compensated heading orientation from said third data set; and communicating the tilt compensated heading orientation and the pitch and roll orientation.

3. A method for determining a distortion corrected magnetic heading as in claim 1 wherein said multiplicity of first and second data sets and said multiplicity of orientations is at least five.

4. A method for determining a distortion corrected magnetic heading as in claim 1 wherein said predetermined time period is less than about one second.

5. A method for determining a distortion corrected magnetic heading comprising the steps: acquiring a first set of data from two or more magnetometers for magnetic field strength sensing and a second set of data from one or more means forgravity field strength sensing within a predetermined time period in a first orientation; generating a first filtered data set by processing the first set of data with a first digital filter, wherein the first digital filter comprises a Finite ImpulseResponse algorithm; generating a second filtered data set by processing the second set of data with a second digital filter, wherein the second digital filter comprises a Finite Impulse Response algorithm; compensating the first filtered data set witha first temperature compensation algorithm; compensating the second filtered data set with a second temperature compensation algorithm; calibrating the first set of data with a first nonlinear function whose coefficients are predetermined; calibratingthe second set of data with a second nonlinear function whose coefficients are predetermined; generating a third set of magnetometer data from the calibrated first and second set of data; wherein the generating a third set of magnetometer data stepcomprises the steps: filtering said calibrated first set of data with a stability filter; filtering said calibrated second set of data with a minimum tilt separation filter; processing the filtered first and second set of data with a median filter witha first-in-first-out buffer to define the third set of data; processing the third set of data with a recursive least squares soft-iron and hard-iron offset estimator comprising a first stage estimator and a second stage estimator; wherein saidfirst-stage estimator comprises calculating an upper-triangular soft-iron distortion matrix and a hard-iron offset vector to obtain a first-stage corrected geomagnetic field vector and wherein said second-stage estimator comprises calculating a rotationmatrix to obtain a second stage corrected geomagnetic field vector; calculating a pitch and roll orientation from the calibrated second set of data; calculating a heading orientation from the calibrated second set of data and the third set ofmagnetometer data, wherein a multiplicity of first and second data sets are acquired in at least five orientations for the determining such that the accuracy of the distortion correction improves with two or more first and second data sets acquired; andcommunicating the magnetic heading and the pitch and roll orientation.

6. A method for determining a distortion corrected magnetic heading as in claim 5 wherein said communicating comprises an interface device comprising at least one from a group comprising visual display, visual touch display, optical fiber,electronic, audible, printed, telephonic, wireless and digital symbols.

7. A method for determining a distortion corrected magnetic heading as in claim 5 wherein said predetermined time period is less than about one second.

8. A method for determining a distortion corrected magnetic heading as in claim 5 wherein said two or more means for gravity field strength sensing are chosen from a group comprising gyroscopes, inclinometers and accelerometers.

9. A magnetic compass apparatus comprising: two or more magnetometer sensors; one or more means for gravity field strength sensing; a magnetic distortion correction algorithm; means for signal conditioning for the sensors wherein said meansfor signal conditioning comprises a finite-impulse-response digital filter with user-selective taps; means for processing; wherein the means for processing comprises at least one processor configured to apply a fitting function with parametersdetermined using least squares to correct a calibration setting for converting sensor data to gravity field strength readings and/or magnetometer readings: and wherein the means for processing comprises at least one processor configured to processreceived magnetometer data with a stability filter, to process received gravity field strength data using a minimum-tilt-separation filter, and to process magnetometer data and gravity field strength data using a median filter with a first-in-first-outbuffer to define a third set of data; and wherein the means for processing comprises at least one processor configured to process the third set of data with a recursive least squares soft-iron and hard-iron offset estimator comprising a first stageestimator and a second stage estimator; and wherein said recursive least squares soft-iron and hard-iron offset estimator further comprises predetermined or user selectable initialization values; means for information storage storing at least a portionof the magnetic distortion correction algorithm; at least one temperature compensator wherein the at least one temperature compensator processes magnetic sensor data; a means for starting and stopping a calibration procedure; and means forcommunicating.

10. The magnetic compass apparatus of claim 9, wherein said magnetometer sensors comprise magneto-inductive sensors.

11. The magnetic compass apparatus of claim 9, wherein said one or more means for gravity field strength sensing are chosen from a group comprising gyroscopes, inclinometers and accelerometers.

12. The magnetic compass apparatus of claim 9, wherein said means for information storage comprises at least one from a group comprising volatile semiconductor, non-volatile semiconductor and hard disk memory wherein at least one from a groupcomprising gravity field strength reading, magnetometer reading, one or more sets of calibration settings, one or more sets of calculated pitch, roll, and tilt-compensated heading readings, initialization values, filtering algorithm, location code andidentity code are stored therein.

13. The magnetic compass apparatus of claim 9, wherein said means for communicating comprises at least one interface device chosen from a group comprising visual display, visual touch display, keyboard, signals via hard wire, Bluetooth™,video, voice, RF, optical fiber, telephonic, wireless and digital symbols.

14. The magnetic compass apparatus of claim 9, wherein said means for processing and said means for signal conditioning are one or more processors resident on one or more integrated circuit chips.

15. The magnetic compass apparatus of claim 9, wherein said means for processing and said means for signal conditioning comprise at least one software program.

16. The magnetic compass apparatus of claim 9, wherein said magnetometer sensors and said means for gravity field strength sensing may be sensing continuously.

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이제 마지막으로 개발하면 되는 여러 참조 자료들 중에 선정된 지자기센서 소프트웨어 알고리즘 프로젝트 자료.

8개월동안 기나긴 기간동안 연구&개발을 해왔던 프로젝트를 종지부를 지을 수 있는 계기가 되길-

처음에는 무엇을 할지 막막했는데, 이제는 익숙하고, 내가 다룰 수 있는 기술이 되어버렸다.

자~ 정상이 저기 앞에 보이기 시작 했으니, 조금만 더 노력하고, 최선을 다하자!