Direct calculation method of probability density from sampled vibration signal based on linear interpolation method

In order to monitor, analyze and diagnose the conditions of all kinds of machines, it is often necessary to calculate the probability density function of the sampled vibration signal. A new direct calculation method of probability density from sampled vibration signal based on the linear interpolation method (LIM) is presented in this paper. Two advantages are observed: 1) the time length of each amplitude segment obtained from a sampled vibration signal by the LIM is closer to the original continuous vibration signal, and 2) the calculation results of probability density got by calculating directly the ratio of time length of each amplitude segment to the total time of sampled vibration signal are more correct than those obtained by other existing methods. The applications to sampled simulation and actual vibration signals of a rolling bearing show that the probability density curves obtained by the new direct calculation method are more accurate and smoother than the curves got by other estimating methods used in a lot of famous software.