There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

We present a new method to accurately locate persons indoors by fusing inertial navigation system (INS) techniques with active RFID technology. A foot-mounted inertial measuring units (IMUs)-based position estimation method, is aided by the received signal strengths (RSSs) obtained from several active RFID tags placed at known locations in a building. In contrast to other authors that integrate IMUs and RSS with a loose Kalman filter (KF)-based coupling (by using the residuals of inertial- and RSS-calculated positions), we present a tight KF-based INS/RFID integration, using the residuals between the INS-predicted reader-to-tag ranges and the ranges derived from a generic RSS path-loss model. Our approach also includes other drift reduction methods such as zero velocity updates (ZUPTs) at foot stance detections, zero angular-rate updates (ZARUs) when the user is motionless, and heading corrections using magnetometers. A complementary extended Kalman filter (EKF), throughout its 15-element error state vector, compensates the position, velocity and attitude errors of the INS solution, as well as IMU biases. This methodology is valid for any kind of motion (forward, lateral or backward walk, at different speeds), and does not require an offline calibration for the user gait. The integrated INS+RFID methodology eliminates the typical drift of IMU-alone solutions (approximately 1% of the total traveled distance), resulting in typical positioning errors along the walking path (no matter its length) of approximately 1.5 m.

/pdf/accurate-pedestrian-indoor-navigation-by-tightly-coupling-1bj85o1lov.pdf

Accurate Pedestrian Indoor Navigation by Tightly Coupling Foot-Mounted IMU and RFID Measurements

Online telemedicine systems are useful due to the possibility of timely and efficient healthcare services. These systems are based on advanced wireless and wearable sensor technologies. The rapid growth in technology has remarkably enhanced the scope of remote health monitoring systems. In this paper, a real-time heartmonitoring systemis developed considering the cost, ease of application, accuracy, and data security. The system is conceptualized to provide an interface between the doctor and the patients for two-way communication. The main purpose of this study is to facilitate the remote cardiac patients in getting latest healthcare services which might not be possible otherwise due to low doctor-to-patient ratio.The developed monitoring system is then evaluated for 40 individuals (aged between 18 and 66 years) using wearable sensors while holding an Android device (i.e., smartphone under supervision of the experts). The performance analysis shows that the proposed system is reliable and helpful due to high speed. The analyses showed that the proposed system is convenient and reliable and ensures data security at low cost. In addition, the developed system is equipped to generate warning messages to the doctor and patient under critical circumstances.

/pdf/a-real-time-health-monitoring-system-for-remote-cardiac-22ycwkypxr.pdf

A real-time health monitoring system for remote cardiac patients using smartphone and wearable sensors

This paper is concerned with the distributed set-membership filtering problem for a class of general discrete-time nonlinear systems under event-triggered communication protocols over sensor networks. To mitigate the communication burden, each intelligent sensing node broadcasts its measurement to the neighboring nodes only when a predetermined event-based media-access condition is satisfied. According to the interval mathematics theory, a recursive distributed set-membership scheme is designed to obtain an ellipsoid set containing the target states of interest via adequately fusing the measurements from neighboring nodes, where both the accurate estimate on Lagrange remainder and the event-based media-access condition are skillfully utilized to improve the filter performance. Furthermore, such a scheme is only dependent on neighbor information and local adjacency weights, thereby fulfilling the scalability requirement of sensor networks. In addition, an optimization algorithm is developed to minimize the trace of the estimated ellipsoid set, and the effect from the adopted event-triggered threshold is thoroughly discussed as well. Finally, a simulation example is utilized to illustrate the usefulness of the proposed distributed set-membership filtering scheme.

A Set-Membership Approach to Event-Triggered Filtering for General Nonlinear Systems Over Sensor Networks

Fall detection is a major challenge in the public healthcare domain, especially for the elderly as the decline of their physical fitness, and timely and reliable surveillance is necessary to mitigate the negative effects of falls.This paper develops a novel fall detection system based on a wearable device. The system monitors the movements of human body, recognizes a fall from normal daily activities by an effective quaternion algorithm, and automatically sends request for help to the caregivers with the patient's location.

/pdf/development-of-a-wearable-sensor-based-fall-detection-system-1ox7znuva1.pdf

Development of a Wearable-Sensor-Based fall detection system

This study proposes a fast and stable recursive ellipsoidal state-bounding-based set-membership estimation algorithm for the state estimation of linear system with unknown-but-bounded (UBB) disturbances. The proposed algorithm has a prediction–correction structure in time update and observation update, which is similar to Kalman filter. For both time update and observation update, there is a data-depending weighting factor. The observation weighting factor is acquired by minimising the upper bound on a Lyapunov function of the posteriori estimation error. It has been demonstrated that the estimation error of the proposed algorithm is input-to-state stable when the system is uniformly observable. With the property of selective observation update, the proposed algorithm not only improves the point estimation accuracy but also decreases the computation load of observation weighting factors and the volume of feasible ellipsoid sets. The efficiency of the proposed algorithm has been demonstrated by numerical simulations with different UBB disturbances.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-cta.2015.0654

Ellipsoidal state-bounding-based set-membership estimation for linear system with unknown-but-bounded disturbances

The current GPS satellite constellation provides limited availability and reliability for a country like Japan where mountainous terrain and urban canyons do not allow a clear skyline to the horizon. At present, the Japanese Quasi-Zenith Satellite System (QZSS) is under investigation through a government-private sector cooperation. QZSS is considered a multi-mission satellite system, as it is able to provide communication, broadcasting and positioning services for mobile users in a specified region with high elevation angle. The performance of a Global Navigation Satellite System (GNSS) can be quantified by availability, accuracy, reliability and integrity. This paper focuses on availability, accuracy and reliability of GPS with and without augmentation using QZSS. The availability, accuracy and reliability of GPS only and augmented GPS using QZSS in the Asia-Pacific and Australian area is studied by software simulation. The simulation results are described by the number of visible satellites as a measure of availability, geometric dilution of precision as a measure of accuracy and minimal detectable bias, and bias-to-noise rate as a measure of reliability, with spatial and temporal variations. It is shown that QZSS does not only improve the availability and accuracy of GPS positioning, but also enhances the reliability of GPS positioning in Japan and its neighboring area.

/pdf/performance-analysis-of-gps-augmentation-using-japanese-54q0lxnntm.pdf

Performance analysis of GPS augmentation using Japanese Quasi-Zenith Satellite System

The current global positioning system (GPS) provides limited availability and capability for a country like Japan where mountainous terrain and urban canyons do not allow a clear skyline to the horizon. At present, the Japanese Quasi-Zenith Satellite System (QZSS) is under investigation through a cooperative effort between the government and the private sector. QZSS is considered a multi-function satellite system, as it is able to provide communication, broadcasting, and positioning services for mobile users in a specified region with a high elevation angle. The additional GPS compatible signals from QZSS can remarkably improve the availability, accuracy, and capability of GPS positioning. This work focuses on the performance of GPS augmentation using the proposed QZSS. The QZSS satellite constellation and signal structure are briefly reviewed. Positioning with pseudo-range and carrier phase are discussed. The performance of GPS augmentation using QZSS in the Asian-Pacific and Australian area is studied using software simulations. The results are presented using the number of visible satellites as a measure of availability, GDOP as a measure of accuracy, and ambiguity success rate as a measure of capability of carrier-phase-based positioning with spatial and temporal variations. The results show that the QZSS will improve not only the availability and accuracy of GPS positioning, but will also enhance the capability of the GPS carrier-phase-based positioning in Japan and neighboring regions.

Performance evaluation of GPS augmentation using Quasi-Zenith Satellite System

Currently the research in binocular stereo vision area mainly focuses on camera calibration and stereo matching. For camera calibration, to estimate the camera's parameters is of vital very importance for acquiring better three-dimensional positioning reconstruction accuracy. This research investigates camera calibration parameters for a binocular stereo vision system and their effects on system reconstruction accuracy. Three different types of parameters and their effects on system reconstruction accuracy are probed with a semi-physical simulation. Firstly, a mathematic model is established and the major sources of parameter errors are analyzed for measuring system. Secondly, a semi-physical simulation system is developed to analyze the effects of parameter errors on the system reconstruction accuracy in the binocular stereo vision system. The binocular stereo vision system is treated as a black box. Three types of parameter errors (i.e., errors of the distortion parameter, camera internal and external parameters) are selected as input variables of the black box, and corresponding system reconstruction errors are regarded as output variables. The effects on the system reconstruction accuracy are analyzed using results of simulation. Finally, correlations between each of the three parameter errors and the system reconstruction error are analyzed, and influence on accuracy of the system is given. The results show that distortion parameter error has a minimal impact on system reconstruction accuracy and belongs to secondary factor. The impact of internal parameter error on system reconstruction accuracy is slightly larger, and correlation of them is linear. The external parameter error directly determines system reconstruction accuracy by affecting baseline distance and the angle between cameras.

Falin Wu

Papers

Development of a Wearable-Sensor-Based fall detection system

Ellipsoidal state-bounding-based set-membership estimation for linear system with unknown-but-bounded disturbances

Performance analysis of GPS augmentation using Japanese Quasi-Zenith Satellite System

Performance evaluation of GPS augmentation using Quasi-Zenith Satellite System

Error analysis of calibration parameters estimation for binocular stereo vision system