Micro-doppler-based in-home aided and unaided walking recognition with multiple radar and sonar systems

Published in IET Radar, Sonar and Navigation. Online first 21/06/2016.The potential for using micro-Doppler signatures as a basis for distinguishing between aided and unaided gaits is considered in this study for the purpose of characterising normal elderly gait and assessment of patient recovery. In particular, five different classes of mobility are considered: normal unaided walking, walking with a limp, walking using a cane or tripod, walking with a walker, and using a wheelchair. This presents a challenging classification problem as the differences in micro-Doppler for these activities can be quite slight. Within this context, the performance of four different radar and sonar systems – a 40 kHz sonar, a 5.8 GHz wireless pulsed Doppler radar mote, a 10 GHz X-band continuous wave (CW) radar, and a 24 GHz CW radar – is evaluated using a broad range of features. Performance improvements using feature selection is addressed as well as the impact on performance of sensor placement and potential occlusion due to household objects. Results show that nearly 80% correct classification can be achieved with 10 s observations from the 24 GHz CW radar, whereas 86% performance can be achieved with 5 s observations of sonar

Robust and Analytical Cardiovascular Sensing

The photoplethysmogram (PPG) is a noninvasive cardiovascular signal related to the pulsatile volume of blood in tissue. The PPG is user-friendly and has the potential to be measured remotely in a contactless manner using a regular RGB camera. In this dissertation, we study the modeling and analytics of PPG signal to facilitate its applications in both robust and remote cardiovascular sensing. In the first part of this dissertation, we study the remote photoplethysmography (rPPG) and present a robust and efficient rPPG system to extract pulse rate (PR) and pulse rate variability (PRV) from face videos. Compared with prior art, our proposed system can achieve accurate PR and PRV estimates even when the video contains significant subject motion and environmental illumination change. In the second part of the dissertation, we present a novel frequency tracking algorithm called Adaptive Multi-Trace Carving (AMTC) to address the micro signal extraction problems. AMTC enables an accurate detection and estimation of one or more subtle frequency components in a very low signal-to-noise ratio condition. In the third part of the dissertation, the relation between electrocardiogram (ECG) and PPG is studied and the waveform of ECG is inferred via the PPG signals. In order to address this cardiovascular inverse problem, a transform is proposed to map the discrete cosine transform coefficients of each PPG cycle to those of the corresponding ECG cycle. As the first work to address this biomedical inverse problem, this line of research enables a full utilization of the easy accessibility of PPG and the clinical authority of ECG for better preventive healthcare

A semi‐active human digital twin model for detecting severity of carotid stenoses from head vibration—A coupled computational mechanics and computer vision method

In this work we propose a methodology to detect the severity of carotid stenosis from a video of a human face with the help of a coupled blood flow and head vibration model. This semi‐active digital twin model is an attempt to link non‐invasive video of a patient face to the percentage of carotid occlusion. The pulsatile nature of blood flow through the carotid arteries induces a subtle head vibration. This vibration is a potential indicator of carotid stenosis severity and it is exploited in the present study. A head vibration model has been proposed in the present work that is linked to the forces generated by blood flow with or without occlusion. The model is used to generate a large number of virtual head vibration data for different degrees of occlusion. In order to determine the in vivo head vibration, a computer vision algorithm is adopted to use human face videos. The in vivo vibrations are compared against the virtual vibration data generated from the coupled computational blood flow/vibration model. A comparison of the in vivo vibration is made against the virtual data to find the best fit between in vivo and virtual data. The preliminary results on healthy subjects and a patient clearly indicate that the model is accurate and it possesses the potential for detecting approximate severity of carotid artery stenoses