Improvements on a Novel Hybrid Tracking System Markus Zank; Leyla Kern; Andreas Kunz ETH Zurich 29.11.2018

Content Background and application field Classification of tracking systems Basic operation principle Building and testing the system Conclusions and outlook 11/29/2018

Background and application field VR environments gain immersion by the sensation of real walking on ground (without treadmills) Sizes and distances can be perceived more naturally than with a “flythrough” (using a joystick, etc.) Requires continuous accurate tracking even under adverse conditions Hybrid systems (optical and inertia-based) often not sufficient due to drift 11/29/2018

Classification of tracking systems 11/29/2018

Classification of tracking systems Inertia-based systems drift quadratically with time: Errors occur even if the user does not walk Frequent recalibration necessary Electromagnetic tracking systems directly measure distances Need fixed reference point Not suitable for exploring large virtual environments Do not drift with time Error increases with large tracking distance 11/29/2018

Basic operation principle Idea of a “quasistatic” reference on the stationary foot Base station is attached to HMD, measures distance to stationary and moving foot Distance from one foot to the other can be calculated Error linearly accumulates with the number of steps, but not with distance or time IMU is used for step detection only 11/29/2018

Basic operation principle Old switching mode changed reference one a foot entered the swing mode Large position error since reference is switched during swing phase New switching method changes reference once a foot enters stance phase Small error since reference is switched while both feet are in stance phase 11/29/2018

Building and testing the system Razer Hydra electromagnetic tracking system: Two sensors, one base station (cable-bound) Two ReSense accelerometers (Blue tooth connectivity) Razer sensors are attached to shoes’ heels Accelerometers are attached to shoes heels Razer base station is attached to head-mounted display 11/29/2018

Building and testing the system Old and new system setup is compared In both cases: Oscillations stem from walking Reference is taken with an absolute optical tracking system Intersense IS-1200 Old setup immediately shows measurement error New setup follows ideal path for about 14 s (slow walking) 11/29/2018

Conclusions and outlook Proposed system is able to bridge situations with invisible markers Recalibration is less frequently required than for inertia systems  larger distance of markers possible Electromagnetic system still cable-bound, wireless preferred  STEM Sensor signals will also be used to control limbs’ movements of an avatar Foot’s roll motion is still a source of error  will be eliminated in future work. 11/29/2018

Thank you for your attention. {zank, kunz}@iwf.mavt.ethz.ch Thank you for your attention.