Pushing the limits of intertial motion sensing

Abstract

This thesis explores how to capture and digitize human and animal motion with miniature IMU motion sensing devices and fulfill a wide range of application requirements despite resource constraints related to sensor limitations, wireless communication, processing, and energy consumption. The hypothesis is that the limitations of inertial sensing technology can be circumvented by devising intelligent algorithms that exploit application specifics. In the first part of this thesis, these limitations are circumvented by only measuring the acceleration and angular velocity magnitude, which are directionless values. This is used to track the intensity of motion over time, allowing for objective measurement of for example how active a person is, which has applications in healthcare. In the second part of this thesis, the capabilities of the sensor devices include measuring orientation and displacement with acceptable quality, yet only over short intervals of up to a minute, depending on the intensity of the motion. This is used to measure body angles and gait symmetry for human and equine applications. The time limitation for the displacement result is circumvented by exploiting the periodicity of locomotion, so that it is not needed to calculate the absolute displacement. Body angles are only measured relative to the vertical axis, so that an accurate attitude measurement is sufficient. In the third part of this thesis, an indoor positioning system is designed and analyzed that aims to meet the requirements for use by firefighters using foot-mounted motion sensors and pedestrian dead-reckoning (PDR). This is achieved by tracking the full path that a motion sensor takes trough a building while it is attached to the firefighter's boot. Performance is impeded by drift errors on the orientation yaw direction and in the displacement result and the irregular and sometimes intense movements performed by firefighters are challenging. These challenges are addressed by using innovative algorithms that involve additional sensors in the tracking process.Experiments show that it is possible to estimate simple motion features like motion intensity and whether sensors are moving simultaneously, even with very limited IMU sensors. With more recent and capable inertial sensors, it possible to measure periodic angular and lateral kinematic motion features with sufficient accuracy for sports and medical applications targeted at humans and animals alike. With state-of-the-art IMU v devices augmented with barometric and magnetic sensors, it is possible to estimate the path of a firefighter in a building, despite the fact that firefighters tend to move in unconventional ways. The collective experiments show that limitations of inertial sensing technology can be circumvented by devising intelligent algorithms that exploit application specifics. During the course of these experiments, sensor devices were developed that are now being used world-wide in academia and medical applications. vii zoals bewegingsintensiteit en of sensoren gelijktijdig...