gnss/ins product design cycle taking into account memsmems

GNSS/INS Product

Design Cycle

GNSS/INS Product GNSS/INS Product

Design CycleDesign Cycle

Taking into account

MEMS-based IMU sensors

Taking into account Taking into account

MEMSMEMS--based IMU sensorsbased IMU sensors

L. Vander Kuylen

15th December 2005

L. Vander Kuylen

15th December 2005

December 19, 2006 ©2006 Septentrio N.V. 2

ContentContent

� Product Definition

� Product Development� Hardware � Firmware

� Measurement Campaign in Challenging Environment


Integrating MEMS-based IMU Integrating MEMS-based IMU

� Increased usage of GNSS receivers in industrial applications� Short GNSS-outage periods

� Development of MEMS-based IMU sensors� Small� Low-power consumption� Cheap


Product DefinitionProduct Definition

� Goal:� Mainly to increase availability of reliable position

solution� Provide an attitude solution

� IMU sensor shall� Be cost effective� Provide an accurate IMU-based position during

periods of GNSS outage

� Optimal solution: application dependent



� Applications� Industrial and agriculture applications

� Regular short periods of GNSS outage� Low-visibility areas when driving next to buildings/trees

� Orientation of vehicle

� UAVs� Orientation of vehicle

� Interested in MEMS IMU due to small size and low-power consumption

� Maritime applications� Orientation of vehicle



� Types of IMU sensors� Navigational-grade

� LN92 (Northrop Grumman), etc.� Export licence constraint

� 100,000 €

� Tactical-grade IMU sensors� HG1700 (Honeywell), LN-200 (Northrop Grumman), etc.

� Possibly export licence constraint

� 15,000 € - 20,000 €

� Low-grade IMU sensors� Xsens, Crossbow, BEI Technologies, VIT Engineering, etc.� MEMS-based� 1,000 € - 10,000 €


Product Development: HardwareProduct Development: Hardware

� Commercial Of The Shelf (COTS) IMU� Increase flexibility for different applications

� Integration firmware runs on receiver CPU

� IMU measurements are provided to receiver through RS232 COM-interface


Product Development: FirmwareProduct Development: Firmware

� Firmware Development for MEMS-based IMU

� Loosely-coupled Integration: � Data fusion in position, velocity,

time domain � 2 decentralized (Kalman) Filters� Closed-loop

� Advantages compared to tightly-coupled integration:

� Better fault detection performance

� Less complexity � Less computational effort

� Disadvantages compared to tightly-coupled integration:

� Less availability� Less accurate


ContentContent

� Product Definition

� Product Development� Hardware � Firmware

� Measurement Campaign in Challenging Environment


Measurement Campaign in Challenging

Environment


Environment

GPS antenna is placed above error sources

cranes are open structures

signal-obstruction is limited: signal loss is brief

GPS does not suffer from crane tail



Environment


Environment

� PolaRx2 High-end GPS-receiver� SBAS PVT, available @1Hz

� Prototype MEMS-based IMU� Sensors:

� Analog Devices: accelerometers (XYZ) and gyroscopes(XY)

� Motorola: gyroscope (Z)

� Measurement processing @100Hz

� Vicinity of cranes:� Low/No GPS visibility (DOP)� Degraded position solution


Measurement Campaign: GPS based PVTMeasurement Campaign: GPS based PVT

GPS-based

solution (red)

Nort

h [m

]

East [m]


Measurement Campaign: Integrated PVTMeasurement Campaign: Integrated PVT

Nort

h [m

]

East [m]

≈≈≈≈ 5 m

≈≈≈≈ 5 m

GPS-based

solution (red)

Integrated GPS/IMU

solution (blue)


Measurement Campaign: ConclusionsMeasurement Campaign: Conclusions

� Error growth using MEMS-based IMU� 05 sec GPS outage ⇒ 2.5m horizontal position error� 10 sec GPS outage ⇒ 5m horizontal position error� 30 sec GPS outage ⇒ 80m horizontal position error

� Conclusions� Results are not perfect, due to

� IMU sensor used

� Models used in integration filter

� Usage of low-quality IMU improves availability of reliable position solution in challenging environments

� Depending on the vehicle motion, constraints can be used to improve the solution


� Thank you!

Leen Vander Kuylen

Navigation Research & Development

[email protected]

Please visit our website www.septentrio.com

gnss/ins product design cycle taking into account memsmems

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