A Portable and Costeffective Configuration of Strapdown INSGPS

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) 1

A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use Outline Background: we need precise, small, light and inexpensive navigation system. 2. Method: my system 3. Evaluation: how precise? 4. Conclusion 1. 2006 KSAS/JSASS Joint Symposium 2

A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use Background (1/5) Many Needs for Precise Navigation data n Many applications for requiring precise navigation data (position, velocity, attitude) Of course, navigate aircrafts, spacecrafts n Observe cars, trains, etc. n Control robots, UAVs n Can we apply accumulated navigation technologies of aircrafts to these applications? 2006 KSAS/JSASS Joint Symposium 3

A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use Background (2/5) One of technologies: INS/GPS n 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 4

A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use Background (3/5) Mechanism of INS/GPS the laws of motion Inertial Sensors Acceleration Angular Speed INS Position Velocity Attitude GPS Receiver Position Velocity triangle surveying Satellites Radio wave Integration INS/GPS Position, Velocity, Attitude 2006 KSAS/JSASS Joint Symposium 5

A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use Background (4/5) Traditional vs. Developing INS/GPS n Traditional n Ultra Precise (Error: <1 m, <1 deg) Big (> 1000 cm 3) Heavy (> 1 kg) and s t f a r c ir A ly n O Spacecrafts! Expensive Now developed Precise? Trade-Off motivation Small (< 1000 cm 3) Light (< 1 kg) Cost-Effective (> $100 K) 2006 KSAS/JSASS Joint Symposium (< $100 K) 6

A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use Background (5/5) Goal of my study Meaningful to discuss about the tradeoff between precision and other specifications. n The goal of my study n 1. 2. Develop as small, light, cost-effective INS/GPS system as possible. Investigate its precision correctly 2006 KSAS/JSASS Joint Symposium 7

A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use Method (1/7) Components Do not use n Big, heavy, expensive dedicated components n Ring laser gyro n Military-use GPS Use n Small, light, inexpensive components n MEMS inertial sensors n Civil-use GPS 2006 KSAS/JSASS Joint Symposium 8

A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use Method (2/7) MEMS Sensors and Civil-use GPS n MEMS inertial sensors n n 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 n n n Mainly for car navigation system Small(~10 cm 2), Light(<10 g), Inexpensive(~$100) AND good precision (Error: 10~20 m) 2006 KSAS/JSASS Joint Symposium 9

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

A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use 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) • Attitude (4[Roll, Pitch, Heading] States) quaternion Angular Speed 2006 KSAS/JSASS Joint Symposium 11

A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use 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 12

A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use Method (6/7) Equations: EKF When INS update n When GPS data is obtained EKF Time Update n EKF Correct 2006 KSAS/JSASS Joint Symposium quaternion 13

A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use Method (7/7) Overall View Strap-down configuration MEMS sensors Leverage quaternion for system modeling 2006 KSAS/JSASS Joint Symposium 14

A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use Evaluation Outline (1/11) n Prototyping Based on my proposed system n Calibration is performed n n Test n for Precision Compare the prototype with an existent precise navigation device 2006 KSAS/JSASS Joint Symposium 15

A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use 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 2006 KSAS/JSASS Joint Symposium 16

A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use Evaluation (3/11) Detail of Prototype 2006 KSAS/JSASS Joint Symposium 17

A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use Evaluation (4/11) Calibration for MEMS INS n Temperature Drift n Misalignment rotating settling main error source of MEMS INS that can be easily removed 2006 KSAS/JSASS Joint Symposium 18

A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use Evaluation (5/11) Calibration of Prototype n The n result of calibrations Temperature drift n Misalignment slope not 0 ! Y, Z X Temperature vs. Sensed Acceleration (X-axis Accelerometer) True Angular Speed (X-axis) vs. Sensed Angular Speed (X, Y, Z-axis Gyro) 2006 KSAS/JSASS Joint Symposium 19

A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use Evaluation (6/11) n Comparison of the prototype with GAIA Test for Precision (2006/06) n GAIA: an ultra high-precision INS/GPS device developed by Japan Aerospace Exploration Agency (JAXA) n Error: < 1 m in absolute position n In flight of an experimental aircraft, Mu. PALa of JAXA 2006 KSAS/JSASS Joint Symposium 20

A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use Evaluation Scene of Test (7/11) GAIA Mu. PAL-a Prototype 2006 KSAS/JSASS Joint Symposium 21

A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use Evaluation (8/11) Results of Test Results (The Prototype: Red, GAIA: Green) Position (3 D) Velocity Attitude Nearly equal to GAIA 2006 KSAS/JSASS Joint Symposium 22

A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use Evaluation (9/11) Detail of Results Statistical Summary of the error of the prototype by reference to GAIA Position < 10 m Velocity < 2 deg Attitude > 10 deg 2006 KSAS/JSASS Joint Symposium 23

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

A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use Evaluation (11/11) Effectiveness of Calibration n With calibration n Without calibration Example : Roll History Calibration works well. 2006 KSAS/JSASS Joint Symposium 25

A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use Conclusion n My Navigation System n n n 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 26

A Portable and Cost-effective Configuration of Strap-down INS/GPS for General-purpose Use Future Work n Fight n against low frequency noise Time-Frequency Analysis n Wavelet multi resolution analysis n Wavelet de-nosing n Other compensation system n Earth magnetism sensor for attitude etc. 2006 KSAS/JSASS Joint Symposium 27