Study On The Photoacoustic Weak Signal Based On The Duffing Equation

With more and more pollution gases emissioning, it affects people’s health. Photoacoustic spectrum detection technology has become the key technology of pollution gas detection for its good real-time and high precision. Duing to the low content of pollution gases, combing with the complicated external environment, makes the photoacoustic signal looks extremely weak compared with noise. The traditional detection method can’t effectively detect this signal. The method based on Duffing equation has high sensitivity to the same frequency, and its immunity to noise. But there still is a long way to apply it in reality. So it is necessary to research and explore this photoacoustic weak signal detection based on Duffing equation.First of all, we analyze the advantages and disadventages of existing methods, at last we choose the dirving force disturbance detection method. On the system status discrimination, the time of calculation method is too long; the observation method is unable to automatically recognize.They are all not suitable for practical application. So this paper puts forward the new method-regional separation method. The experimental results show that the system can correctly judging chaos state and large period state, and realizes the automatic discrimination.Then this paper analyzes the impact of parameters on the state of the system in detail. Next it introduces the mechanism and characteristics of weak photoacoustic signal, as well as the problems existing in the detection. Aiming at these problems, we apply a variable scale difference method. Results show that this method enhances the detection accuracy and the capability of anti-noise compared to the traditional Duffing equation,the realative error of the measured signal is small.Finally, this paper proposes a system design based on Duffing equation of the photoacoustic spectrum pollution gases detection, then detailly analyzes the design of light source, photoacoustic pool and the signal processing modules. Subsequent to it, the practical application of the main influence factors are detailly analyzed. The implementation of the system not only broadens the application scope of Duffing detection method, but also promote the development of its research.