Reliability evaluation of grating encoder based on the accelerated degradation test

In order to overcome the difficulty in evaluating the reliability of grating encoders in a short time for its high reliability level, a reliability evaluation method based on the accelerated degradation test is proposed. First, according to the accelerated model with two types of stresses, an accelerated test scheme is designed. Then, models of linear degradation paths under different stress levels are established based on characteristic degradation quantity. Furthermore, the pseudo time between failures is solved according to the failure threshold value. Afterwards, a reliability model of grating encoders with a variable of pseudo time between failures is developed. At the same time, mean time between failures is estimated under different stress levels by the maximum likelihood estimation method and simulated annealing algorithm. Finally, the parameters of the accelerated model are solved and the reliability of the grating encoder at the normal stress level is evaluated.