The Modulation Of Chirp Signal And Its Test Research On Detecting Technique Of Rockbolt

With the continuous construction of various projects, the application of rockbolt is expending, which leads to sharp increase in use of rockbolt, and also makes more and more attention to the relationship between quality of rockbolt and safety of projects. And the voice of demanding for improving detection accuracy becomes stronger and stronger.For perfecting the detecting system of bolt-anchoring quality, we put forward vibroseis technique to accurately realize the control of stress wave signal, and Chirp signal, which has good autocorrelation, is adopted as vibroseis signal. With application compiled by Delphi, many kinds of signals are modulated by changing sweep mode and frequency range, like sinusoidal signal, ricker wavelet signal and three types of Chirp signals, et al. Through a series of laboratory tests on signals' autocorrelation and attenuation, we verify that Chirp signal has wider frequency band, higher energy, better autocorrelation, and is easier to be detected, which is quite suitable to be detecting signal for vibroseis.With computer sound card, supraconduction magnetic resonance, and other technologies, Chirp signal and vibroseis are introduced to the field on testing of bolt-anchoring quality, which is also my innovation in this thesis. Based on the advanced idea, we realize a test device, and carry out a series of laboratory experiments with it. Therefore, we comprehend more about autocorrelation and attenuation of the signals, and the main results are as follows:(1) The autocorrelation of sinusoidal signal is so poor that it's unsuitable as detecting signal for vibroseis. Although ricker wavelet signal has better autocorrelation, because it's short pulse signal, and the attenuation of signal is too fast, which makes it excluded also.(2) Three kinds of Chirp signals all have good autocorrelation, even when the reflected signals add together, which reveals its antinoise performance is satisfying. The Chirp signals all have a optimal frequency range that generally exists in the section between 2k-20kHz and 4k-20kHz, but further research is needed for its exact location.(3) In our testing condition, the autocorrelation of sinusoidal signal remains badness. When the amplitude of received signal is smaller, the autocorrelation of ricker wavelet signal becomes extremely poor. In the same condition, Chirp signal could maintain good autocorrelation, and the first arrival time is very obvious, even on the extreme conditions when the amplitude of received signal attenuates observably.(4) Through the comparison of attenuation coefficient, we find, for testing Chirp signals, the energy of received signals attenuates more slowly, and the rate of autocorrelation's deterioration is evidently smaller than the rate of amplitude's decay. In the same condition, their character is close to each other in energy attenuation. Relatively, the linear Chirp signal of 2k-20k and the exponential Chirp signal of 4k-20k have more excellent performance than others.The quantitative control of vibroseis signal, especially for the control of signal's frequency, is still the virgin land in this field. The research on this subject perfects the testing system of bolt-anchoring Quality, and definitely makes some contribution to the development of stress wave detection method. The performance of our test device in laboratory tests is satisfying comparatively, and we generally achieve the anticipated result. As the technology involves plentiful knowledge of many fields, there still needs further improvement.