A Robust High-Accuracy Ultrasound Indoor Positioning System Based on a Wireless Sensor Network

Abstract

This paper describes the development and implementation of a robust high-accuracy ultrasonic indoor positioning system (UIPS). The UIPS consists of several wireless ultrasonic beacons in the indoor environment. Each of them has a fixed and known position coordinate and can collect all the transmissions from the target node or emit ultrasonic signals. Every wireless sensor network (WSN) node has two communication modules: one is WiFi, that transmits the data to the server, and the other is the radio frequency (RF) module, which is only used for time synchronization between different nodes, with accuracy up to 1 μs. The distance between the beacon and the target node is calculated by measuring the time-of-flight (TOF) for the ultrasonic signal, and then the position of the target is computed by some distances and the coordinate of the beacons. TOF estimation is the most important technique in the UIPS. A new time domain method to extract the envelope of the ultrasonic signals is presented in order to estimate the TOF. This method, with the envelope detection filter, estimates the value with the sampled values on both sides based on the least squares method (LSM). The simulation results show that the method can achieve envelope detection with a good filtering effect by means of the LSM. The highest precision and variance can reach 0.61 mm and 0.23 mm, respectively, in pseudo-range measurements with UIPS. A maximum location error of 10.2 mm is achieved in the positioning experiments for a moving robot, when UIPS works on the line-of-sight (LOS) signal.

Online Time-Resolved Reconstruction Method for Acoustic Tomography System

“…The major challenge in employing acoustic tomography for temperature field monitoring is to achieve high TOF measurement accuracy. An accurate TOF estimation is also essential in other applications, for example, ultrasonic ranging, positioning and synchronisation systems [36,37], ocean tomography [3], ultrasonic breast cancer detection [7], and seismic wave arrival time estimation. To date, a number of TOF estimation methods have been developed in other disciplines.…”

Monitoring of Concrete Placement and Vibration for Real-Time Quality Control

“…Ultrasonic positioning system has many advantages which made it gain popularity. Ultrasound waves cannot penetrate walls and are negligibly affected by the surroundings, they which means that the system is not disturbed by ultrasonic waves in other rooms [16]. It provides with centimetre-level accuracy with a low system cost, and it can track multiple mobile nodes simultaneously [22].…”

Development of High-accuracy Multi-degrees-of-freedom Indoor Ultrasonic Positioning Approach for Automated Guided Vehicles

“…AGV is on the ground so that the Z′-axis coordinate of point A is −h. The coordinates of point A in the rotating coordinate system can be expressed as ( , , ) , , 4 4…”

“…(2,3) Although the current technology, e.g., time of flight (ToF) combined with ultrasonics and trilateration localization has been applied to determine the distance between the object and the anchor node, some limitations still exist. (4,5) For example, the accuracy of ultrasonic positioning is greatly affected by wave loss and the blind area of the ultrasonic sensor. (6,8) Accordingly, the ultrasonic applications in positioning are still facing a big challenge.…”