GPS World, September 2016

MEMS IMU CAROUSELING FOR GROUND VEHICLES Calibrated wheel IMU position results ADVERTISER INDEX COMPANIES FEATURED IN THIS ISSUE SEPTEMBER 2016 WWW GPSWORLD COM GPS WORLD 57 ADVERTISER PAGE S CAST NAVIGATION 7 CHC NAVIGATION 35 COMNAV TECHNOLOGY 29 EFFIGIS 24 GENEQ 43 HARXON CORP 31 HEMISPHERE GNSS 15 INTERGEO 47 ADVERTISER PAGE S IFEN 11 ITSNT 56 IP SOLUTIONS 21 KCS BV INSIDE BACK COVER KVH INDUSTRIES 5 NOVATEL BACK COVER NTLAB 19 RACELOGIC 13 ADVERTISER PAGE S SBG SYSTEMS 25 SEPTENTRIO 27 SPECTRACOM INSIDE FRONT COVER SPIRENT FEDERAL 9 SUZHOU FOIF 53 TALLYSMAN 23 TELEORBIT 55 UNICORE COMMUNICATIONS 17 M icro electromechanical system MEMS gyroscopes have advantages for orientation sensing and navigation as they are small low cost and consume little power However the significant noise at low frequencies produces large orientation errors as a function of time Controlled physical rotation of the gyroscope can remove the constant part of the gyro errors and reduce lowfrequency noise As adding motors for this would increase the system cost it would be advantageous to attach gyros to a rotating platform that is already built in the vehicle The authors present theory and results for novel navigation systems where an inertial measurement unit IMU is attached to the wheel of a ground vehicle The results show that a low cost MEMS IMU can provide a very accurate navigation solution using this placement option It has two clear advantages wheel motion removes the constant bias of the gyroscopes distance traveled can be estimated from accelerometer data For low dynamic ground vehicles this approach is superior to conventional dead reckoning with an odometer when a lowcost MEMS gyro provides the heading information Test results are obtained using a vehicle driving slowly on a relatively smooth surface and the use of an accelerometer for wheel phase angle tracking was fairly accurate for this purpose For higher vehicle dynamics and gravel roads the accelerometer data will be contaminated with significant centripetal and motion caused accelerations For that purpose the use of high range gyro with the sensitivity axis perpendicular to the wheel plane should be considered to complement the accelerometer based bias free observations Applying this method to passenger cars at highway speeds would require an IMU with wide bandwidth and solving the challenges at high speeds remains a future research topic In addition there is a requirement to bring electricity to the wheel and the need for wireless data transfer As the major error source of MEMS gyros is eliminated the method opens new applications for inertial navigation systems In addition there is a very large potential for wheel based sensing in general not restricted to Earth surface or navigation applications By Jussi Collin Department of Pervasive Computing Tampere University Published in IEEE Transactions on Vehicular Technology June 2015