Optimal design of step-stress accelerated degradation tests based on the Tweedie exponential dispersion process

In this paper, we are interested in the optimization of step-stress accelerated degradation test plan when the degradation path follows the Tweedie exponential dispersion process which has been shown to be an important family in degradation analysis. We firstly prove that, under the Tweedie exponential dispersion process model with a drift parameter being an exponential function of the (transformed) stress level, a multi-level step-stress accelerated degradation test plan will correspond to a simple step-stress accelerated degradation test plan using only the minimum and maximum stress levels under D-optimality and V-optimality criteria. The optimum step-stress accelerated degradation test plan based on these two optimality criteria is subsequently derived, a numerical example is furthermore presented to compare the efficiency of the proposed optimum simple step-stress accelerated degradation test plans and some step-stress accelerated degradation test plans proposed by a previous study. In addition, a simulation study is conducted for investigating the performances of the proposed step-stress accelerated degradation test plans.