Research On Mini-SOSIE Based On Ternary Pseudorandom Coding Technique

In some environment-sensitive areas such as urban geological prospecting,and mineral resources exploration in complex mountainous areas,it is difficult to carry out seismic exploration work for some large volume of vehicle-controlled vibrator,because it is inconvenient to move in some complex terrain.Moreover,in China mineral resources are mostly in the mountains,complex terrain where traffic is not convenient.The mini-SOSIE has a great advantage over these seismic sources in geological exploration for it is in a small size,light weight,easy to move and high output force.However,in the study of mini-SOSIE,high resolution and high signal-to-noise ratio(SNR)have been a hot issue,and it is an urgent problem to be solved.In the traditional control mode of mini-SOSIE,there is serious correlation interference and side lobe effect in the correlation seismic records,because the vibrating signal is periodic when it dose continuous impact.In the improved binary pseudorandom coding control mode,the correlation interference is reduced compared with the traditional control method,but the autocorrelation function of binary pseudorandom coding has side lobe effect,which restricts the increase of the resolution and SNR of seismic records.In order to solve these problems,a control method based on ternary pseudorandom coding technique is proposed in this paper and an excitation signal generator is also designed.Firstly,we study the ternary pseudorandom coding technique and the coding sequence generation principle.The result of the autocorrelation function of ternary pseudorandom coding sequence turns out to be similar to the perfect pulse function for it has no side lobe effect.Secondly,the application of ternary pseudorandom coding technique in the control of mini-SOSIE is introduced in detail and the coding matching principle is put forward.Each code corresponds to the different vibration state of the mini-SOSIE.According to theprinciple of coding matching,the excitation signal generator is designed to realize the coding control mode of the mini-SOSIE.In the design of the control system,we added a feedback modular for some signals cannot be output correctly because of the mechanical characteristics of the mini-SOSIE.A sensor is placed on the base plate,and we can detect the correctness of the output signal of the mini-SOSIE by collecting the signal from the sensor.The software and hardware are combined to realize the ternary pseudorandom coding control of the mini-SOSIE,which can provide a new method for the development of the mini-SOSIE technology.Finally,a field experiment was carried out in a test site.We verified whether the excitation signal generator can correctly send out the control signal or not by comparing the output vibrating signal and the under known coding sequence.In addition,the seismic records obtained by the binary pseudorandom control method and the ternary pseudorandom coding control method are compared.The results turn out to be like this: coherent interference is reduced significantly and the ratio between the main lobe and the side lobe is improved thus improved the SNR of seismic exploration.In the analysis of spectrum,the frequency range is obviously widened thus the resolution is improved.The above results show that the control method proposed in this paper is feasible and effective.The influence of different control parameters on the experimental results is also discussed in this paper.The experimental parameters should be set according to the experimental requirements and the exploration conditions in different experiments.And we summarized the whole paper and put forward some suggestions for the future research.