Improvement of Ultrasound-based System Using Sine Wave Detector and CAN Network

Abstract

This paper presents an improved indoor localization system based on RF and ultrasonic signal which we named SNSH system. This system composes of a transmitter mounted in a mobile target, and a series of receiver nodes which are managed by a coordinator. By measuring Time Delay of Arrival (TDoA) of RF and ultrasonic signal from the transmitter, distance from target to receiver node is calculated and sent to the coordinator through CAN network, and all the information are gathered in PC to estimate 3D position of the target. Sine wave detector and dynamic threshold filter are applied to provide excellent accuracy of range measurement from TDoA result, and multilateration algorithms is realized to optimize coordinate determination accuracy. Specifically, Linear Least Square and Non-linear Least Square techniques are implemented to contrast their performances in target coordinate estimation. RF signal encoding/decoding time, time delay in CAN network and math calculating are carefully considered to ensure optimal system performance and get ready for field application. Experiments show that sine wave detector algorithm has greatly improved range measurement accuracy, with mean error at 2.2mm and maximum error at 6.7 mm, for distance below 5m. In addition, 3D position accuracy is greatly enhanced by multilateration methods, with mean error in position stay under 15mm, and 90% confident error values at 23mm for LLS, 20mm for NLS. Overall system update period has been verified in real system operation, with maximum rate at 25ms, and compared with other existing researches.

A Doppler-Tolerant Ultrasonic Multiple Access Localization System for Human Gait Analysis

“…We used sine chirp waveform from DAC as input to the driver circuit which consists of SN74AS04 hex inverters and IC-SN754410 which can boost the transmission power of the DAC output and can provide a bidirectional current drive of up to 1 A. The driver circuit was similar to the circuit explained in [ 34 ]. MURATA MA40S4S and MA40S4R were used as ultrasonic transmitters and receivers respectively.…”

Ultrasonic localization method based on receiver array optimization schemes

“…Accordingly, the improved estimated coordinates are obtained. Suppose that z a = ½z t p R 1 is unknown parameter, when z p = ½x y z T , then the linear equation with noise is established, as formula (12)…”

“…As a result of h 0 = G 0 a z 0 a , replace z a with z 0 a , according to formulas (14) and (12), we can obtain formula (15)…”

“…The other location technology is to make use of pre-deployed additional base stations (BS) to achieve precise indoor positionings, such as radio frequency identification (RFID), 3,4 ultra-wideband (UWB), [5][6][7][8][9] Li-Fi, 10 ultrasound, [11][12][13][14][15][16][17][18] Bluetooth, 19,20 and ZigBee 21 technology. This type of technology can be used to increase accuracy by increasing the number of reference nodes, as shown in Figure 1; the reference nodes are arranged indoor and the positioning accuracy can be centimeter level.…”