Abstract
This paper presents a chirp based ultrasonic positioning system (UPS) using orthogonal chirp waveforms. In the proposed method, multiple transmitters can simultaneously transmit chirp signals, as a result, it can efficiently utilize the entire available frequency spectrum. The fundamental idea behind the proposed multiple access scheme is to utilize the oversampling methodology of orthogonal frequency-division multiplexing (OFDM) modulation and orthogonality of the discrete frequency components of a chirp waveform. In addition, the proposed orthogonal chirp waveforms also have all the advantages of a classical chirp waveform. Firstly, the performance of the waveforms is investigated through correlation analysis and then, in an indoor environment, evaluated through simulations and experiments for ultrasonic (US) positioning. For an operational range of approximately 1000 mm, the positioning root-mean-square-errors (RMSEs) &90% error were 4.54 mm and 6.68 mm respectively.
Highlights
The location of a radiating ultrasonic source can be determined in three-dimensional (3D) space using information regarding its distances from at least three reference points, the locations of which are known, providing that the configuration of these reference points is adequate
The absolute location errors of the receiver obtained from the experiments for the proposed, time-division multiplexing (TDM), and frequency-division multiplexing (FDM) techniques are shown in Figure 8 in terms of 90% error
The positioning accuracies of the TDM and FDM techniques were higher and lower for the reason described in Section 1 and the accuracy of the proposed method is comparable with the TDM technique
Summary
The location of a radiating ultrasonic source can be determined in three-dimensional (3D) space using information regarding its distances from at least three reference points, the locations of which are known, providing that the configuration of these reference points is adequate This technique has been extensively used in research and production fields in many and varied applications, such as indoor positioning [1,2,3,4,5,6,7], robot navigation [8,9] and human pose estimation [10]. In threshold detection approach the TOF is measured by triggering the event when the received signal exceeds a predefined threshold level for the first time which, must be above the noise level. This is computationally simple and can be implemented with low-cost single-frequency US transducers, for low signal-to-noise ratio (SNR)
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