1. 1 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)

2. A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use 2015/4/232006 KSAS/JSASS Joint Symposium 2 Outline 1. Background: we need precise, small, light and inexpensive navigation system. 2. Method: my system 3. Evaluation: how precise? 4. Conclusion

3. A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use 2015/4/232006 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?

4. A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use 2015/4/232006 KSAS/JSASS Joint Symposium 4 Background (2/5) One of technologies: INS/GPS INS/GPS Navigation System High update ratio but Accumulate Error Cancel Error but Low update ratio Cancel Error and High update ratio Inertial Navigation System (INS) Global Positioning System (GPS) +

5. A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use 2015/4/232006 KSAS/JSASS Joint Symposium 5 Background (3/5) Mechanism of INS/GPS Position, Velocity, Attitude Inertial Sensors Position Velocity Position Velocity Attitude INSGPS Integration Acceleration Angular Speed INS/GPS Radio wave Satellites the laws of motiontriangle surveying Receiver

6. A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use 2015/4/232006 KSAS/JSASS Joint Symposium 6 Background (4/5) Traditional vs. Developing INS/GPS Traditional Now developed Big (> 1000 cm 3 ) Heavy (> 1 kg) Small (< 1000 cm 3 ) Light (< 1 kg) Expensive (> $100K) Cost-Effective (< $100K) Only Aircrafts and Spacecrafts! Ultra Precise (Error: <1m, <1deg) Precise? motivation Trade-Off

7. A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use 2015/4/232006 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 1. Develop as small, light, cost-effective INS/GPS system as possible. 2. Investigate its precision correctly

8. A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use 2015/4/232006 KSAS/JSASS Joint Symposium 8 Method (1/7) Components Big, heavy, expensive dedicated components Ring laser gyro Military-use GPS Small, light, inexpensive components MEMS inertial sensors Civil-use GPS Do not useUse

9. A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use 2015/4/232006 KSAS/JSASS Joint Symposium 9 Method (2/7) MEMS Sensors and Civil-use GPS MEMS inertial sensors Electronic circuit and sensing element integrated Small(~1 cm 2 ), 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 cm 2 ), Light(<10g), Inexpensive(~$100) AND good precision (Error: 10~20m)

10. A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use 2015/4/232006 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

11. A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use 2015/4/232006 KSAS/JSASS Joint Symposium 11 Method (4/7) Equations: equations of motion for INS Velocity (3[ North, East, Down Speed ] States) Position (4[ Latitude, Longitude, Azimuth ] + 1[ Height ] = 5 States) Attitude (4[ Roll, Pitch, Heading ] States) quaternion Acceleration Angular Speed Gravity

12. A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use 2015/4/232006 KSAS/JSASS Joint Symposium 12 Method (5/7) Equations: Linearization for EKF Jacobian i.e. Additive (4 States) Multiplicative (3 States) Obtain linearized form for EKF by following substitution to the equations of motion quaternion Quaternion linearization with keeping the norm unity

13. A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use 2015/4/232006 KSAS/JSASS Joint Symposium 13 Method (6/7) Equations: EKF EKF Time Update EKF Correct quaternion When INS updateWhen GPS data is obtained

14. A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use 2015/4/232006 KSAS/JSASS Joint Symposium 14 Method (7/7) Overall View Leverage quaternion for system modeling Strap-down configuration MEMS sensors

15. A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use 2015/4/232006 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

16. A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use 2015/4/232006 KSAS/JSASS Joint Symposium 16 Evaluation (2/11) Developed Prototype Size: ~ 100 cm 3 Weight: ~ 30 g Cost: ~ $ 300 (w/o structural element) The prototype shows my system is small, light and low-cost

17. A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use 2015/4/232006 KSAS/JSASS Joint Symposium 17 Evaluation (3/11) Detail of Prototype

18. A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use 2015/4/232006 KSAS/JSASS Joint Symposium 18 Evaluation (4/11) Calibration for MEMS INS Temperature Drift Misalignment main error source of MEMS INS that can be easily removed settling rotating

19. A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use 2015/4/232006 KSAS/JSASS Joint Symposium 19 Evaluation (5/11) Calibration of Prototype Temperature drift Misalignment The result of calibrations Temperature slope not 0 ! Sensed Angular Speed (X, Y, Z-axis Gyro) X Sensed Acceleration (X-axis Accelerometer) True Angular Speed (X-axis) vs. Y,Z

20. A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use 2015/4/232006 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-  of JAXA

21. A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use 2015/4/232006 KSAS/JSASS Joint Symposium 21 Evaluation (7/11) Scene of Test Prototype MuPAL-  GAIA

22. A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use 2015/4/232006 KSAS/JSASS Joint Symposium 22 Evaluation (8/11) Results of Test Results (The Prototype: Red, GAIA: Green) Position (3D)VelocityAttitude Nearly equal to GAIA

23. A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use 2015/4/232006 KSAS/JSASS Joint Symposium 23 Evaluation (9/11) Detail of Results Statistical Summary of the error of the prototype by reference to GAIA Position Velocity Attitude < 10m < 2 deg > 10 deg

24. A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use 2015/4/232006 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)

25. A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use 2015/4/232006 KSAS/JSASS Joint Symposium 25 Evaluation (11/11) Effectiveness of Calibration With calibration Without calibration Example : Roll History Calibration works well.

26. A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use 2015/4/232006 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.

27. A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use 2015/4/232006 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.