Distance and velocity measurement method of ultrasonic sensor using single-bit signal correlation

Abstract

This paper introduces a computationally intensive method for measuring distance and velocity at high measurement rates using chaotic pulse position modulation (CPPM) signals and single-bit signal processing in a single ultrasound sensor system. To prevent crosstalk from other ultrasonic sensor systems a chaotic system is used, and an ultrasonic pulses are transmitted as a pulse sequence generated by CPPM. After receiving the ultrasound signal, the single-bit signal was generated by a fast Fourier transform threshold, which also functions as an environmental noise filter. Single-bit signal processing has been adopted to reduce the computational load when cross-correlating the transmitted and received signals for time of flight (TOF) calculations. Single bit signal processing has more than 100 times memory saving effect in this study. Additionally, as the signal to noise ratio (SNR) increases, extension of the maximum measurable distance in ultrasonic distance sensor system is expected. The simulation shows the crosstalk rejection performance of the proposed method and the experimental results confirm the improvement of the measurement speed by the proposed method. The proposed distance measurement method solves the crosstalk problem and prevents the decrease of the measurement speed as the distance increases. The advantage of the proposed distance measurement method is that it can remove crosstalk while maintaining high sampling rate by using general ultrasonic hardware and general microcontroller. The proposed velocity measurement method using time dilation correlation enables the Doppler effect to be analyzed in the time domain. The speed can be obtained with much lower computation than the Doppler effect analysis in the frequency domain, which is a general method, so that the improvement of the vehicle control performance can be expected. The total signal processing method is minimized so that the price competitiveness, which is the advantage of ultrasonic sensors, is saved. As a result, it is possible to improve the measurement performance in the measurement within 20 m, thereby contributing to the safety of the vehicle.