Current progress on weak signal detection

In machinery condition monitoring, weak signal is a type of signal that has very low signal-to-noise ratio (SNR). Therefore, it is necessary to develop effective methods so as to enhance or extract useful information from the noisy signal. These methods aim to solve the problem of de-noising and separation of mixed-signal. This paper investigated the current progress on weak signal detection methods, including traditional and emerging, linear and non-linear methods. The combination of various methods is presented according to their advantages and disadvantages of these methods. In the end, the future development of weak signal detection technology is summarized.