Zero Velocity Detection Using Foot Mounted Ultra Wide Band for Pedestrian Positioning

Zero velocity detection is an important problem in the context of foot mounted strapdown inertial navigation. Strapdown inertial navigation uses filtering algorithms to fuse inertial sensor information and the additional aiding information such as zero velocity potential update (ZUPT). ZUPT works on the principle that the velocity of the foot is zero during the stance phase. Various inertial sensor based Zero Velocity Detectors (ZVDs) have been proposed in the literature such as threshold-based detectors, learning based detectors and gait cycle segmentation-based detectors. These detectors suffer from limitations such as inaccurate threshold estimation, requirement of large amount of data and use of overly complex algorithms. Other sensors like pressure sensors and ultrasonic sensors have also been used complementarily with IMU sensors to perform zero velocity detection. They have not been used independently to perform zero velocity detection. In this paper, a novel approach is proposed which uses dual foot mounted ultra-wide band (UWB) sensor along with the IMU to perform zero velocity detection. From previous studies and experiments, it has been found that during heel strike and during heel off the distance between the feet is maximum. During walking, the UWB sensor provides observations of distance between the feet which are periodic in nature. The periodicity of the UWB observations and the relation of distance between the feet and the various events during walking is utilized to perform zero velocity detection by using UWB sensor. The method was evaluated in an experiment with four human participants at a single speed, yielding IoU scores ranging from 0.54-0.81, and F1 scores ranging from 0.70-0.90. These promising results indicate that the potential of UWB sensor-based zero velocity detection approaches warrants further exploration as a possible replacement for current inertial sensor-based methods.