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A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use

A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use. ＊ Masaru Naruoka (Univ. of Tokyo) Takeshi Tsuchiya (Univ. of Tokyo). Outline. Background : we need precise , small , light and inexpensive navigation system. Method : my system

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A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use

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  1. A Portable and Cost-effective Configurationof Strap-down INS/GPSfor General-purpose Use ＊ Masaru Naruoka (Univ. of Tokyo) Takeshi Tsuchiya (Univ. of Tokyo)

  2. Outline • Background: we need precise, small, light and inexpensive navigation system. • Method: my system • Evaluation: how precise? • Conclusion 2006 KSAS/JSASS Joint Symposium

  3. Background (1/5)Many Needs for Precise Navigation data • Many applications for requiring precise navigation data (position, velocity, attitude) • Of course, navigate aircrafts, spacecrafts • Observe cars, trains, etc. • Control robots, UAVs Can we apply accumulated navigation technologies of aircrafts to these applications? 2006 KSAS/JSASS Joint Symposium

  4. Background (2/5)One of technologies: INS/GPS • INS/GPS Navigation System Inertial Navigation System (INS) Global Positioning System (GPS) + High update ratio but Accumulate Error Cancel Error but Low update ratio Cancel Error and High update ratio 2006 KSAS/JSASS Joint Symposium

  5. Background (3/5)Mechanism of INS/GPS the laws of motion triangle surveying INS GPS Inertial Sensors Receiver Acceleration Angular Speed Position Velocity Attitude Satellites Position Velocity Radio wave Integration INS/GPS Position, Velocity, Attitude 2006 KSAS/JSASS Joint Symposium

  6. Traditional Now developed Background (4/5)Traditional vs. Developing INS/GPS Precise? Ultra Precise (Error: <1m, <1deg) Trade-Off motivation Big (> 1000cm3) Heavy (> 1 kg) Small (< 1000cm3) Light (< 1 kg) Only Aircrafts and Spacecrafts! Cost-Effective (< $100K) Expensive (> $100K) 2006 KSAS/JSASS Joint Symposium

  7. Background (5/5)Goal of my study • Meaningful to discuss about the trade-off between precision and other specifications. • The goal of my study • Develop as small, light, cost-effectiveINS/GPS system as possible. • Investigate its precision correctly 2006 KSAS/JSASS Joint Symposium

  8. Big, heavy, expensive dedicated components Ring laser gyro Military-use GPS Small, light, inexpensive components MEMS inertial sensors Civil-use GPS Method (1/7)Components Do not use Use 2006 KSAS/JSASS Joint Symposium

  9. Method (2/7)MEMS Sensors and Civil-use GPS • MEMS inertial sensors • Electronic circuit and sensing element integrated • Small(~1cm2), Light(<1 g), Inexpensive(<$100) • BUT,an INS device using MEMS inertial sensors accumulates error very quickly. • Civil-use GPS receiver • Mainly for car navigation system • Small(~10 cm2), Light(<10g), Inexpensive(~$100) • AND good precision (Error: 10~20m) 2006 KSAS/JSASS Joint Symposium

  10. Method (3/7)INS/GPS Algorithm • Strap-down configuration • No need for any mechanical gimbals • Integration by extended Kalman filtering (EKF) • Loose-coupling: require small calculation power • Use quaternions actively • Mathematically simple model to compensate for large MEMS sensor error • Eliminate singular points derived from Euler angles 2006 KSAS/JSASS Joint Symposium

  11. Method (4/7)Equations: equations of motion for INS • Velocity (3[North, East, Down Speed] States) Acceleration Gravity • Position (4[Latitude, Longitude, Azimuth] + 1[Height] = 5 States) quaternion • Attitude (4[Roll, Pitch, Heading] States) Angular Speed 2006 KSAS/JSASS Joint Symposium

  12. Method (5/7)Equations: Linearization for EKF Obtain linearized form for EKF by following substitution to the equations of motion quaternion Quaternion linearization with keeping the norm unity • Jacobian i.e. Additive (4 States) • Multiplicative (3 States) 2006 KSAS/JSASS Joint Symposium

  13. EKF Time Update EKF Correct Method (6/7)Equations: EKF When INS update When GPS data is obtained quaternion 2006 KSAS/JSASS Joint Symposium

  14. Method (7/7)Overall View Strap-down configuration MEMS sensors Leverage quaternion for system modeling 2006 KSAS/JSASS Joint Symposium

  15. Evaluation (1/11)Outline • Prototyping • Based on my proposed system • Calibration is performed • Test for Precision • Compare the prototype with an existent precise navigation device 2006 KSAS/JSASS Joint Symposium

  16. Evaluation (2/11)Developed Prototype Size: ~ 100 cm3 Weight: ~ 30 g Cost: ~ $ 300 (w/o structural element) The prototype shows my system is small, light and low-cost 2006 KSAS/JSASS Joint Symposium

  17. Evaluation (3/11)Detail of Prototype 2006 KSAS/JSASS Joint Symposium

  18. Temperature Drift Misalignment Evaluation (4/11)Calibration for MEMS INS rotating settling main error source of MEMS INS that can be easily removed 2006 KSAS/JSASS Joint Symposium

  19. Temperature drift Misalignment Evaluation (5/11)Calibration of Prototype • The result of calibrations slope not 0 ! slope not 0 ! Y,Z X Temperature True Angular Speed (X-axis) vs. vs. Sensed Acceleration (X-axis Accelerometer) Sensed Angular Speed (X, Y, Z-axis Gyro) 2006 KSAS/JSASS Joint Symposium

  20. Evaluation (6/11)Test for Precision • Comparison of the prototype with GAIA (2006/06) • GAIA: an ultra high-precision INS/GPS device developed by Japan Aerospace Exploration Agency (JAXA) • Error: < 1m in absolute position • In flight of an experimental aircraft, MuPAL-a of JAXA 2006 KSAS/JSASS Joint Symposium

  21. Evaluation (7/11)Scene of Test GAIA MuPAL-a Prototype 2006 KSAS/JSASS Joint Symposium

  22. Evaluation (8/11)Results of Test Results (The Prototype: Red, GAIA: Green) Position (3D) Velocity Attitude Nearly equal to GAIA 2006 KSAS/JSASS Joint Symposium

  23. Evaluation (9/11)Detail of Results Statistical Summary of the error of the prototype by reference to GAIA Position < 10m Velocity < 2 deg Attitude > 10 deg 2006 KSAS/JSASS Joint Symposium

  24. Evaluation (10/11)Summary and Discussion of Test • Error: <10m(Position), <2deg(Roll, Pitch) • Precise enough for general-purpose use • Heading is the worst (Error: >10 deg) • Effect of frequency mode of dynamics • Roll and Pitch is comparatively high mode (> 1Hz) • Heading is low mode (< 1 Hz) • Overlap with low mode noise that cannot remove easily (for example, zero-point change) 2006 KSAS/JSASS Joint Symposium

  25. With calibration Without calibration Evaluation (11/11)Effectiveness of Calibration Example : Roll History Calibration works well. 2006 KSAS/JSASS Joint Symposium

  26. Conclusion • My Navigation System • small, light and cost-effective INS/GPS system for general-purpose use • Strap-down configuration using MEMS sensors and a civil-use GPS receiver • Temperature drift and misalignment calibrated • Use EKF and Quaternion • The test shows it is precise enough for general-purpose use; Error is under 10 m in position, and 2 deg in roll and pitch. 2006 KSAS/JSASS Joint Symposium

  27. Future Work • Fight against low frequency noise • Time-Frequency Analysis • Wavelet multi resolution analysis • Wavelet de-nosing • Other compensation system • Earth magnetism sensor for attitude etc. 2006 KSAS/JSASS Joint Symposium

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