Highly Accurate Ultrasonic Positioning and Tracking Systems

by Mohammad Khyam

Institution: University of New South Wales
Department: Engineering & Information Technology
Year: 2015
Keywords: Ultrasonic positioning; Ultrasonic tracking
Record ID: 1043359
Full text PDF: http://handle.unsw.edu.au/1959.4/54259


Localization is the process of determining the current location of a target(s) within given coordinates using a location system. The localization process has two main phases: firstly, the measurement phase, that establishes a relationship in terms of the distance and/or angle between the targets(s) to be localized and the system infrastructure; and secondly, the positioning phase, that exploits the measured information to calculate the absolute or relative location coordinates of the target(s). So far the most widely used positioning system is the Global Positioning System (GPS). However, in a GPS system, the receiver requires line-of-sight (LOS) reception from different satellites, which is usually difficult to obtain indoors. Therefore, as there is a need for alternate location systems in these GPS-obstructed environments, indoor positioning has drawn considerable attention from both academia and industry. Indoor environments, which are characterized by obstacles such as walls, floors, ceilings, and furniture, provide countless opportunities for a wide range of applications requiring different levels of accuracy. High-accuracy applications, such as gait analysis, usually use optical motion capture systems (MCSs), which are cost-prohibitive for many users, and also require complex arrangements of expensive equipment. In addition, they are responsive to changes in lighting and shadow. Therefore, with the aim of overcoming these limitations, ultrasonic positioning systems (UPSs) have drawn considerable attention. Usually, a narrowband UPS uses either a single tone or narrowband chirp signal in the measurement phase in which accurate estimations of distance, through time-of-flight (TOF) techniques, are fundamental. Generally, cross-correlation, which produces a peak at the time delay between a transmitted and received signal, is considered the optimal TOF estimation technique. Since their accuracy depends on the width of the correlation peak, which is inversely proportional to the signal’s bandwidth, these systems can only be said to be highly accurate if the reflected or multipath signal at the receiver is separated in time by more than the width of the correlation peak; otherwise, errors are introduced into the system. To improve the accuracy of such systems, the bandwidth of the signal must be increased, which increases the cost of the system. In the first part of this thesis, a new phase-correlation-based TOF estimation technique, that uses a narrowband chirp signal working in a closely spaced multipath environment, is proposed. In this system, the correlation peak becomes narrower by virtually, rather than physically, increasing the signal’s bandwidth, which reduces system cost. The performance of the proposed method is evaluated experimentally. As the correlation technique finds matches between transmitted and received signals, both signals need to be stored at the receiver, which increases hardware cost and computational complexity. In the second part of this thesis, firstly, to solve the limitations of the…