Improvement of Measurement Range via Chaotic Binary Frequency Shift Keying Excitation Sequences for Multichannel Ultrasonic Ranging System

Abstract

The important indicators of multichannel ultrasonic ranging system are correlation characteristics and energy efficiency. The excitation sequences with good correlation characteristics can help avoid crosstalk among multichannel ultrasonic sensors. High energy efficiency can enhance measurement range. This paper proposes a crosstalk elimination method by using the optimal binary excitation sequences modulated with chaotic codes, which include chaotic binary amplitude shift keying (c-BASK), chaotic binary phase shift keying (c-BPSK) and chaotic binary frequency shift keying (c-BFSK). To obtain the both best correlation characteristics and energy efficiency, the Nondominated Sorting Genetic Algorithm-II (NSGA-II) is applied to optimize the chaotic binary excitation sequences. Real experiments have been conducted using an ultrasonic ranging system that consists of eight-channel SensComp 600 series instrument-grade electrostatic sensors excited with chaotic binary modulation sequences. The experimental results show that the c-BFSK outperforms the c-BASK and c-BPSK in terms of the correlation characteristics and energy efficiency. With 2 ms c-BFSK excitation sequences, the longest measurable distance was 720 cm (i.e., increased 11% and 27% with c-BPSK and c-BASK, respectively) with maximal relative error 2.4%.