GNSS/INS Integration using a Tightly Coupled Approach for Navigation of People

with Visual Impairments

M. Troger, C. Fösleitner, J. Seybold

TeleConsult Austria GmbH, Austria

European Navigation Conference 2013

23rd – 25th April 2013

Vienna, Austria

ENC 2013, April 23rd - 25th 2013 - Vienna, Austria2

Motivation (1/2)

Navigation of pedestrian through GNSS

• Position is determined by means of GNSS

• Route to the destination point (track point) is calculated

• Manoeuvring list is generated

• Visually guidance to the track point through Smartphone screen

How to proceed, if the pedestrian is visually impaired?

ENC 2013, April 23rd - 25th 2013 - Vienna, Austria3

Motivation (2/2)

Navigation of visually impaired people

• Determination of position

• Binaural sounds generatedo Depending on user’s position

o Depending on user’s heading

o Depending on position of track point

• Binaural sounds provided to user through stereo-headphone

• Requirements:o High accuracy and availability of position

o High availability of heading

Fusion between GNSS and INS sensors

• Different properties of both systems qualify them for combined use

• Kalman Filter optimal tool for fusion

ENC 2013, April 23rd - 25th 2013 - Vienna, Austria4

Contents

Loosely vs. tightly coupling

Tightly coupled approach

• Parameters of the state

• Measurement updates

• Dynamic model

Dynamic test and results

Conclusion and future work

ENC 2013, April 23rd - 25th 2013 - Vienna, Austria5

Loosely vs. tightly coupling

Loosely coupling Tightly coupling

Advantage of tightly coupling: GNSS measurements can be used if less than four satellites are visible!

ENC 2013, April 23rd - 25th 2013 - Vienna, Austria6

Tightly coupled approach (1/4)

Parameters of the state vector

• ECEF position

• ECEF velocity

• Distance error caused by receiver clock error

• Velocity error caused by receiver clock drift

• Quaternion vector

• Biases of the gyroscopes

ENC 2013, April 23rd - 25th 2013 - Vienna, Austria7

Tightly coupled approach (2/4)

Measurement update: GNSS observations

• Code pseudorangeso Corrected due to ionosphere, troposphere, and satellite clock error

o Elevation based measurement noise

• Dopplero Measurement noise indirect proportional to SNR

ENC 2013, April 23rd - 25th 2013 - Vienna, Austria8

Tightly coupled approach (3/4)

Measurement update: Velocity

• Derivation of step frequency using autocorrelation of acceleration measurements

• Computation of horizontal velocity with step length and step length variation parameter

Measurement update: Bias of angular rates

• During phases without rotation and without movements

• Identification of phases using inertial measurements

ENC 2013, April 23rd - 25th 2013 - Vienna, Austria9

Tightly coupled approach (4/4)

Time update

• Model of uniform motion

• Angular rates and gyro biases are introduced into dynamic coefficient matrix

ENC 2013, April 23rd - 25th 2013 - Vienna, Austria10

Dynamic test and results (1/3)

• Positioning unit was fixed tightly onto the belt at the back of a test person

• Low-cost GPS L1 receiver with raw data outputo Code pseudoranges, Doppler (Output rate: 1 Hz)

o Navigation Message

• IMU with low-cost characteristicso Angular rates, accelerations (Output rate: 20 Hz)

• Synchronisation and storage of measurements on micro-processor board sensor fusion in post-processing

• Reference trajectory based only on GPS observations processed by means of Kalman filtering in real-time (1 Hz)

• Initial alignment at the beginning of the dynamic testo Roll and pitch from accelerations during static phase

o Heading from GPS during dynamic phase

• Default step length of user

ENC 2013, April 23rd - 25th 2013 - Vienna, Austria11

Dynamic test and results (2/3)

Hea

ding

with

out

GP

S

outa

geH

eadi

ng w

ith s

imul

ated

G

PS

out

age

(35

s)

Hor

izon

tal p

ositi

ons

with

out

GP

S o

utag

eH

oriz

onta

l pos

ition

s w

ith

sim

ula

ted

GP

S o

utag

e (3

5 s

)

Dynamic test and results (3/3)

Overview of trajectories overlaid with GoogleTM Earth

Horizontal positions overlaid with GoogleTM Earth

ENC 2013, April 23rd - 25th 2013 - Vienna, Austria13

Conclusion and future work

Conclusion

• Kalman Filter approach shows potential in area of pedestrian navigation

• GPS outages can be bridged over short time interval

• Heading information is usable for binaural guidance

Future work

• Find the optimal weighting between measurement noise and system noise

• Software integration for real time operation

• Online step length derivation

• Refinement of bias update

ENC 2013, April 23rd - 25th 2013 - Vienna, Austria14

Acknowledgement

The research work described was conducted within the project ARGUS, which is co-funded by the EU Seventh Framework Programme under grant FP7-288841(ARGUS).

E-MAIL mtroger@tca.at

WEB www.tca.at

PHONE +43-316-890971-11

FAX +43-316-890971-55

Markus TrogerSenior Systems Engineer