Study On Track Shift Frequency Signal Detection By Improved Duffing Oscillator

In recent years,with the rapid development of high-speed railway in China,high speed and high density are the trend of China's railway development.In the CTCS(Chinese Train Control System,Chinese train control system)–level 2 train control system of train running speed has reached 200~250km/h,the ZPW-2000 jointless track circuit as a part of CTCS-2train control system plays a pivotal role.However,the development of high speed and high density makes the environment of weak current system such as signal system more complex,and it will have an impact on the ZPW-2000 frequency shift signal.At present,with the increase of the noise interference intensity around the rail,the traditional decoding method has a large error in decoding,and may even result in error decoding.In this thesis,a new method to detect the frequency shift signal based on the characteristics of noise immunity in the chaos theory is proposed.First of all,the working principle of ZPW-2000 automatic blocking system and the mathematical model of ZPW-2000 shift-frequency signal are studied in detail in this thesis,the merits and drawbacks of traditional detection methods of track shift-frequency signal are analyzed,and the interference which can affect reception of shift-frequency signal is analyzed.Secondly,the characteristics of chaotic motion are analyzed and the characteristics of the Duffing equation are studied,and the advantages and disadvantages of various chaos discriminant methods are summarized.In this thesis,the Duffing oscillator detection principle for weak 2FSK signal is studied.On this basis,the generalized time scale transform method is used to improve the Duffing equation,which can be used to detect signals with arbitrary frequency.Then the detection blind angle is eliminated by making the original driven signal phase shift a degree.In order to obtain the accurate detection results,on the basis of the qualitative judgment of the phase diagram and time domain diagram,a quantitative method based on the detection statistic is proposed to realize the accurate determination to the detection results.Finally,according to the above research results,the improved Duffing equation is applied to the detection of ZPW-2000 frequency shift signal.Respectively from the two aspects of carrier frequency and low frequency,the steps of detection are given.Using Simulink to build a simulation model and simulation parameters.Respectively in the conditions of absent noise,white noise and traction current harmonic interference,this method accurately detect the carrier frequency and low frequency,and compared with the traditional detection methods,the improved Duffing oscillator detection system can not only solve some problems of traditional Duffing oscillator detection system,but detect thefrequency shift signal in lower signal to noise.This method has high accuracy and better anti-noise performance.