A reliability evaluation model for nonlinear multi-stage growth rate degradation competition failure was established by considering the mechanism of excitation change point and stage change point in the performance degradation of product. Firstly

the three-stage variable coefficient linear regression and homogeneous Poisson process were used to describe the natural degradation process and random shock process respectively. Secondly

the comprehensive reliability of the product was obtained by using the total probability synthesis according to the difference of the stage when the excitation change point reaches the product degradation periods. Finally

taking the micromotor as an example

the validity of the model was verified

and the sensitivity analysis of the reliability about the important parameters of the model was estimated. The sensitivity analysis reveals that to reduce the impact probability increases the system's reliability. Specifically

the probability of a fatal impact is highly sensitive to the reliability effect. Moreover

it is observed that as the arrival rate increases

the maximum number of shocks also increases

leading to a faster degradation rate. Additionally

the occurrence of stage change points is accelerated by excitation change points.