To solve the problem that the PH distribution proposed changes the state space of system, the value iteration algorithm for the semi-Markov decision process is improved to get the optimal inspection and maintenance policy.

• 将位相型(PH)分布引入模型后，决策过程的状态空间发生变化，为了获得适用于原有模型假设的检测与维修优化策略，提出了一种改进的值迭代算法。