RECURRENCE PLOTS

Dear sir:
I am doing some research on bearing fault diagnosis by using RQA ,like the guy in the forum ，I am very confused about the selection of the threshold epsilion.
so I use CWRU bearing fault data ，calculate the Normal bearing and faulty bearing's RPs,but I can't determine the threshold (i’ve seen your recommended papers )，I am trying a lot of threshold but I do not know what is the best choice (sequence's std 0.25*std 1*std,1.5*std,2*std，even 10% max phase radius).
if i want to to compare the different RQA feature between the different bearing fault，how should I set the threshold？ Can I simply set them as a factor multiple of the standard deviation of the time series，or 10% max phase raduius？（I found normal status‘ rps use the 10% max Phase radius almost white and one of the fault condition is almost black..）
i am very sorry about my stupid and repeat question ，i dont know how to set the threshold to makes the recurrence structure clear ...

The threshold selection depends on the research question and the data.

If your data has many outliers or behaves like from a non-stationary process, a normalisation and using a threshold in units of the standard deviation might not be the best choice. Then consider the slecetion that preserves a preselected recurrence rate (such as based on a quantile of the pairwise distances or the fixed amount of nearest neighbours approach).