Pedestrian Tracking Solution Combining an Impulse Radio Handset Transmitter with an Ankle-Mounted Inertial Measurement Unit

Abstract

We address the indoor tracking problem by combining an Impulse Radio-Ultra-Wideband handset with an ankle-mounted Inertial Measurement Unit embedding an accelerometer and a gyroscope. The latter unit makes possible the detection of the stance phases to overcome velocity drifts. Regarding radiolocation, a time-of-arrival estimator adapted to energy-based receivers is applied to mitigate the effects of dense multipath profiles. A novel quality factor associated with this estimator is also provided as a function of the received signal-to-noise ratio, enabling us to identify outliers corresponding to obstructed radio links and to scale the covariance matrix of radiolocation measurements. Finally, both radio and inertial subsystems are loosely-coupled into one single navigation solution relying on a specific extended Kalman filter. In the proposed fusion strategy, processed inertial data control the filter state prediction whereas Combined Time Differences Of Arrival are formed as input observations. These combinations offer low computational complexity as well as a unique filter structure over time, even after removing outliers. Experimental results obtained in a representatively harsh indoor environment emphasize the complementarity of the two technologies and the relevance of the chosen fusion method while operating with low-cost, noncollocated, asynchronous, and heterogeneous sensors.

Integrated UWB/MIMU Sensor System for Position Estimation towards an Accurate Analysis of Human Movement: A Technical Review

“…The PlusOn 410 UWB [ 34 ], UWB Mini4sPlus [ 54 ], and BeSpoon [ 43 ] were each used in one article. Twelve articles did not report on the UWB sensor that was used in their study [ 37 , 40 , 42 , 45 , 48 , 49 , 52 , 53 , 55 , 56 , 63 , 64 ]. Detailed information on the sensor systems used, along with their update rates, is provided in Table 1 .…”

“…The majority of the included articles used a single MIMU on the subject except for four articles that used more than one MIMU [ 7 , 41 , 42 ]. Eight articles did not report on the MIMU sensor that was used in their study [ 32 , 37 , 42 , 45 , 48 , 55 , 56 , 66 ].…”

“…In the reviewed articles, the UWB and MIMU sensors on the body were not always integrated into a single sensor platform or placed physically tied to each other. The UWB and MIMU were placed at different locations on the body for 15 articles [ 31 , 32 , 37 , 39 , 42 , 44 , 45 , 46 , 48 , 49 , 53 , 55 , 56 , 60 , 64 ]. While for another 19 they were physically tied to each other and thus placed at the same location [ 7 , 33 , 34 , 35 , 38 , 40 , 41 , 43 , 47 , 50 , 54 , 57 , 58 , 59 , 61 , 62 , 63 , 65 , 67 ].…”

“…As previously mentioned in Section 3.2.1 , only one UWB tag was placed on the body and was placed mainly on the foot [ 33 , 34 , 40 , 54 , 61 , 63 , 65 ], on a shoulder backpack [ 45 , 46 , 48 , 49 , 55 , 56 , 60 , 64 ], or held in hand steady with no swinging [ 37 , 43 , 47 , 50 , 52 , 57 , 58 , 67 ]. Meanwhile, other articles had a placement on the waist [ 38 , 39 , 41 ], on a head-worn helmet [ 31 , 32 , 44 , 53 ], on the shoulder [ 42 , 59 ], or on the chest/trunk [ 62 ].…”

“…Among them, one article [ 42 ] had two sensors on both feet while others were a single MIMU on one of the feet. The other placement locations were ankles [ 37 ], waist [ 38 ], shoulders [ 59 ], chest/trunk [ 62 ], or held in hand [ 43 , 47 , 50 , 57 , 58 , 67 ]. Three articles [ 7 , 39 , 41 ] had a set of seven MIMUs placed such that there was one on the waist, and pairs of two on the upper legs, lower legs, and feet.…”