| In this thesis, the obstacle detection technology based on ultrasonic sensors has been studied for Autonomous Land Vehicle (ALV) applications. The thesis consists of three closely related subjects: ultrasonic range-finding system, ultrasonic ranging processing method and localization and classification of obstacles.At first, an ultrasonic range-finding system based on a single-chip microcomputer is designed and realized. According to different instructions from PC, the system can accomplish ranging work under different transmitting schemes, different sampling rates as well as different processing methods. The system shows high precision, portability and high resistance to interference through practices.With deeply research of both the effect of the introduction of modulation and demodulation technology on processing gain of range-finding system and the equivalence of correlation detection and matching detection, this paper has realized the digital correlation detection arithmetic based on PN code via the envelope demodulation method. Also the calculate formulas for a fast matching detection approach based on two step correlation is concluded. Besides, for the further improvement of the processing gain, M sequence and polar envelopes are utilized to realize PSK demodulation.In order to get the precise position of the echo, a novel peak detection method is proposed. The error due to the fluctuation of the peak pulse of the cross-correlation function could be eliminated effectively in this way, so the assignment problem of threshold in unknown environment can be resolved well.Incorporating the design of sensor array, data fusion of multiple ultrasonic sensors in different situations is discussed, and also the obstacle localization method is presented. Finally, the echo model is built by analyzing the affecting factors of the waveform of echo, and as a result, a novel obstacle recognition method based on the echo amplitude and duration features is proposed. |
PDF Full Text Request