Optimization Design Of Reliability Degradation Test Of Motorized Spindle Under Step-stress Acceleration

Motorized spindle is one of the core components of middle and high grade CNC machine tools.The stable production operation of manufacturing industry is inseparable from the technical support of high reliability motorized spindle.Reliability test is the basis of reliability information acquisition,reliability prediction and evaluation.Motorized spindle is a high reliability and long life product.It is difficult to get a lot of fault information in the short term,but its performance degradation information always exists.Therefore,considering the test time and cost,combined with the performance degradation information of motorized spindle,it is of great significance for the design and optimization of accelerated degradation test for motorized spindle.First of all,according to the basic structure of the motorized spindle,the sub-system of the motorized spindle is divided,combining with the site fault data information to determine the frequent occurrence of the electro-spindle fault.The random wiener process is used to describe the performance degradation of the motorized spindle.Combining with the Copula function to judge the correlation of the selected performance degradation feature,the life distribution function of the motorized spindle under normal working stress is determined.Secondly,the inverse power rate model is used to establish the step-stress acceleration degradation equation of the motorized spindle.The estimated value of the unknown parameter in the acceleration equation is determined by the experimental data obtained from the accelerated degradation bottoming experiment under step stress.Considering the time cost,test cost and sample cost in the test,the traditional test plan of the motorized spindle step-stress acceleration degradation test based on the inverse power rate model is obtained under the given test interval.Finally,with the objective of minimizing the asymptotic variance of the median life of the motorized spindle performance degradation,a mathematical model for optimal design is established.Combining with particle swarm optimization algorithm,iteratively optimizes the design variables in the model to determine the final test plan.The robustness and stability of the verification results are evaluated through sensitivity analysis and simulation.