Research on Reliability Analysis and Life Distribution of Brushed DC Motor Based on Intelligent Valve Working Condition

The brushed DC motor is the key control component of intelligent valve, and its running state will affect the performance of the whole heat supply system. Therefore, to improve the reliability evaluation accuracy of brushed DC motors, a reliability curve fitting method based on staged lognormal distribution is proposed in this paper. Firstly, the characteristic quantity which can reflect the degradation of brushed DC motor is determined by mathematical model and failure mechanism, and the rationality of the selected degradation quantity is verified by simulation. Then, according to the actual condition of frequent start-stop of intelligent valve, the start-stop experiment is designed to ensure the stability and reliability of the experimental data. Then, through goodness of fit and error analysis, lognormal distribution is selected to fit the degradation quantity, and the degradation model of brushed DC motor is established, and the model parameters are obtained by maximum likelihood estimation. Finally, the life of the brushed DC motor is predicted and the reliability curve of the overall degradation process is fitted in stages. Compared with the global reliability curve fitted directly, the global reliability curve fitted based on staged method can accurately describe the fault probability of brushed DC motor at each time point, reflect its real reliability level, and provide more accurate reliability analysis results.