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Stochastic resonance (SR) has been proved to be an effective way to detect a weak signal submerged in heavy background noise. This paper addresses the improvement of the SR approach to enhance the effectiveness of weak signal detection through a circuitry system. There are mainly two contributions in this study. First, the multiscale noise tuning through a filter array is designed based on the property of 1/ f process to enhance the performance of a classical SR circuitry system. Second, a practical weak signal detection approach is proposed by combining the multiscale noise tuning SR (MSTSR) circuitry with the traditional synchronous demodulation (SD) detector. The multiscale noise tuning greatly widens the noise intensity range suited for the SR effect in comparison with white noise tuning as exhibited by the experiment, and hence the MSTSR circuitry has better applicability. By taking advantage of both the MSTSR circuitry and the SD detector, the proposed combination could effectively detect a weak signal in extremely heavy noise with the signal-to-noise ratio (SNR) lower than −50 dB. The effectiveness of the proposed weak signal detection approach is confirmed by experimental results in output stability and SNR outperforming the SD detector.

This paper proposes a novel approach to periodic fault signal enhancement in rotating machine vibrations with a tristable mechanical vibration amplifier (TMVA) by exploiting stochastic resonance (SR). The TMVA is a nonlinear physical structure system that consists of a cantilever beam and a magnet system. Through the TMVA, the periodic weak signal can be amplified with the assistance of noise in the regime of SR. Benefitting from a wider interwell spacing and a smoother potential curve, the TMVA produces a more regular output waveform with lower noise in a wider operating bandwidth as compared to the monostable and bistable amplifiers. Different from the traditional signal enhancement approach which is based on digital signal processing (DSP) techniques, the designed physical structure can realize signal enhancement in a simple, intuitive, effective and adaptive way without too much complex operations. The effectiveness and efficiency of the proposed approach are validated by a simulated fault signal and the practical bearing and gearbox fault signals, in comparison with a traditional DSP-based SR method. The principle of the proposed approach shows potential applications on rotating machine fault diagnosis area and other areas related to weak periodic signal enhancement.

This Letter reports an out-of-resonance vibro-acoustic modulation (VAM) effect in nonlinear ultrasonic evaluation of a microcracked cantilever beam. We design a model to involve the microcracked cantilever beam in a nonlinear oscillator system whose dynamics is introduced to extend the operating vibration excitation band of the VAM out of resonance. The prototype model exhibits an effective bandwidth four times that of the traditional linear model. The reported VAM effect allows efficiently enhancing the detection, localization, and imaging of various types of microcracks in solid materials at out-of-resonance vibration excitation frequencies.