【作者】 李常有；

【导师】 徐敏强；

【作者基本信息】 哈尔滨工业大学 ， 一般力学与力学基础， 2009， 博士

【摘要】 维修是为了保持和恢复系统良好工作状态所进行的一切活动。维修决策研究的目的是为系统安排合理的维修计划,以用最少的经济代价、时间、资源以及最高的修复率,使系统经常处于完好状态,提高可用性和可靠性,降低退化速度,延长使用寿命,保障使用中的安全性和环境保护等。维修决策的研究内容主要包括维修方式的决策以及各维修方式下如何为系统安排合理的维修计划。本文针对当前维修方式和视情维修决策中存在的一些问题,结合离心压缩机转子系统,对以下几个方面进行了探索和研究:(1)未知权值和混合数据下维修方式决策的研究。将决策者提供的用定性语言描述的属性间的成对比较矩阵转化为模糊数矩阵,采用模糊偏好规划方法求取各属性符合决策者偏好的清晰(crisp)权值。为了解决混合数据问题,提出了基于随机优势和模糊数质心距的ELECTRE III方法。这一方法创建基于模糊数质心距的局部和谐指数和非和谐指数,用于解决任意两个维修方式在模糊评价下的比较问题,并与基于随机优势的局部和谐指数和非和谐指数及ELECTRE III方法相结合,解决混合数据问题。将上述方法应用到离心压缩机转子系统的维修方式决策中,结果表明,提出的方法能为系统在未知权值和混合数据下选择合理的维修方式。(2)离心压缩机转子系统状态评估的研究。采用基于模型的处理方法来估计转子的不平衡量、弯曲量及不对中程度,为了降低噪声对估计精度的影响,提出了基于改进的EMD预处理方法,用有限元分析来论证其有效性;提出基于轴向力的离心压缩机级密封状态的评估方法,该方法采用BP神经网络建立级密封状态和轴向力的关系模型并将训练好的BP神经网络模型用于估计级密封状态,采用FLUENT软件计算不同级密封状态下的轴向力,以验证方法的有效性。结果表明,基于改进的EMD预处理方法和基于模型的处理方法相结合能比较准确地识别出转子系统的不平衡量、弯曲量和不对中程度;基于轴向力的离心压缩机级密封状态的评估方法能较为准确地估计出级密封的状态。(3)连续完全监测的多退化状态变量系统的视情维修决策研究。采用不同参数的平稳Gamma过程描述各退化状态变量,给出平稳Gamma过程单参数的共轭先验分布并进行了证明;推导了单个退化状态变量下预防性维修的期望间隔时间模型,由此得出系统预防性维修的期望间隔时间;根据有效年龄模型(effective age model)的思想建立了不完全预防性维修对系统状态的影响模型;建立了单位时间的期望运行成本模型和平均可用度模型,在此基础上,根据机会维修决策模型的思想,构建了连续完全监测的多退化状态变量系统的视情维修决策模型,并提出改进的理想点法对其进行求解。将提出的模型应用到离心压缩机转子系统的状态分别由不平衡量和由不平衡量、级密封状态及弯曲量决定下的视情维修决策中,数值分析结果表明,提出的模型可以解决连续完全监测的多退化状态变量系统的视情维修决策问题。(4)遭受突然失效和多类退化失效系统的视情维修决策研究。使用不同参数的平稳Gamma过程描述各退化状态变量,推导出单个退化状态变量系统的可靠度计算公式,并采用贝叶斯估计方法实现可靠度中参数的实时估计,其中该方法还考虑了监测噪声的影响。采用两参数weibull分布描述系统突然失效时间的分布,使用贝叶斯估计方法实现可靠度中参数的实时估计。建立了系统同时遭受突然失效和多类退化失效时的可靠度模型,将可靠度作为表征系统状态的指标。创建系统无失效时的预防性维修间隔时间模型以及一次循环内的期望运行时间、停机时间、单位时间的期望运行成本模型,在此基础上,构建了系统同时遭受突然失效和多类退化失效下的视情维修决策模型。将该方法应用到离心压缩机转子系统同时遭受由于不平衡量增大导致的退化失效和轴或者叶轮出现裂纹而导致的突然失效下的视情维修决策中,算例分析结果表明,提出的系统同时遭受突然失效和多类退化失效时的视情维修决策模型是有效的。本文针对当前维修方式和视情维修决策中存在的一些问题,结合离心压缩机转子系统这一对象,提出了可行的解决方法,为维修决策的深入研究及其在离心压缩机转子系统甚至其他系统中的应用提供一定的参考。更多还原

【Abstract】 Maintenance is the performed actions to keep and restore the system in a well condition. The objective of maintenance decision making (MDM) is to scheme the optimal maintenance plan for a system to make the system in a good condition usually, improve system reliability and availability, decrease the deterioration rate, prolong the service life, guarantee the safety as much as possible during system operating, protect the environment and so on under the condition of the minimization of the spent cost, time and other resource and the maximization of the restoration ratio. The research content of MDM consists of the maintenance policy decision making and making the optimal maintenance plan for a system under a certain maintenance policy. In this dissertation, aiming at some problems of the decision making of maintenance policy and condition-based maintenance which have not been solved and are combined with the rotor system of centrifugal compressor, the following contents are explored:(1) Study on maintenance policy decision making with mix data and unknown weight of every attribute. The qualitative pairwise compassion matrix among attributes which is presented by decision-makers is transformed into the fuzzy number matrix before the fuzzy preference programming method is employed to calculate the crisp weights of all attributes. To solve the ploblem of mix data, the ELECTRE III based stochastic dominance and the distance between the centroid point of a fuzzy number and coordinate origin (DCPFNCO) is proposed. The approach constructs the local harmonious and non-harmonious index (LHI and LNHI) based on DCPFNCO firstly in order to solve the problem of the comparision of any two maintenance polices under fuzzy evaluation, and they are combined with LHI and LNHI based on stochastic dominance and ELECTRE III to solve the ploblem of mix data. The proposed approach is applied to maintenance policy decision making of the rotor system of centrifugal compressor. The results of the numerical example show that the optimal maintenance policy for a system could be determined by the proposed approach.(2) Study on condition assessement of the rotor system of centrifugal compressor. The model-based approach is employed to assess the unbalance quantity, the degree of misalignment and the quantity of bending deformation of the rotor system; the preprocessing approach based the improved EMD is presented to reduce the effect of noise on the assessement accuracy; then, finite element analysis is used to verify the two approaches.The condition assessment approach of the stage seal of centrifugal compressor based on the axial thrust is proposed, where the BP neural network is applied to express the relationship between the axial thrust and the stage seal condition and the trained BP neural network is used to assess the stage seal condition; the axial thrusts are calculated by FLUENT under the different condition of the stage seal to verify the proposed approach. According to the results of the numerical examples, it could be seen that the unbalance quantity, the degree of misalignment and the quantity of bending deformation of the rotor system could be assessed accurately by the preprocessing approach based the improved EMD and the model-based approach; the stage seal condition could be estimated exactly by the condition assessment approach of the stage seal of centrifugal compressor based on the axial thrust.(3) Study on condition-based maintenance optimization for the system of which the condition is determined by multi-deterioration condition variables monitored continuously and perfectly. Suppose each deterioration condition variable follow a stationary Gamma process with two certain parameters which are estimated by Bayesian estimation method. The conjugate prior distribution of single parameter of the stationary Gamma process could be obtained and is proved in this section. Then, the expected time interval model of the preventive maintenance of the system whose condition is determined by only one deterioration condition variable is derived and that of the considered system is given subsequently. The effect of the imperfect preventive maintenance on the system condition is formulated according to the idea of the effective age model and the expected restoration time period model of the imperfect preventive maintenance in some literatures is used. The expected operation cost per unit time and the expected availability of the considered system are modeled. On these bases, the condition-based maintenance optimization model for the system whose condition is determined by multi-deterioration condition variables monitored continuously and perfectly is formulated and solved by the improved ideal point method which is proposed in this dissertation. The proposed approach is applied to two cases that the rotor system of centrifugal compressor of which the condition is determined only by unbalance quantity and by unbalance quantity, stage seal condition and the quantity of bending deformation of the shaft, respectively. The results of the numerical examples show that the proposed maintenance optimization model accords with practical engineering and could solve the problem of condition-based MDM for the system of which the condition is determined by multi-deterioration condition variables monitored continuously and perfectly.(4) Study on condition-based maintenance optimization for the system subject to sudden failure and multiple deterioration failure simultaneously. Each deterioration condition variable is assumed to follow a stationary Gamma process with two certain parameters; then, the reliability of the system whose condition is determined by only one deterioration condition variable is derived on the basis of the reliability definition, whose parameter is estimated real-timely by the Bayesian estimation method. Suppose the sudden failure time follow the Weibull distribution with two parameters; then, the reliability of the system subject to only the sudden failure is modeled whose parameters is estimated real-timely by Bayesian estimation method with the conjugate prior distribution of two parameters. Subsequently, the considered system reliability is formulated on the basis of the above two reliability models. It is used for the index of the condition of the system. The models of the interval between two preventive maintenances under the condition without sudden failure, the expected uptime and downtime of the system in a cycle and the expected operational cost per unit time are modeled respectively. On these bases, the condition-based maintenance optimization model for the system undergoing the sudden failure and multi-deterioration failure simultaneously is formulated. The proposed approach is applied to the condition-based MDM of the rotor system of centrifugal compressore which suffer from sudden failure due to occurrence of the crack of the shaft or impeller and deterioration failure due to increase of unbalance quantity. The results of the numerical examples show that the presented condition-based maintenance optimization model for the system undergoing the sudden failure and multi-deterioration failure simultaneously is effective.To sum up, some feasible and effective approaches to solving the not solved problem of decision making of maintenance policy and condition-based maitiance are proposed in this dissertation and they may provides some references for the deep research on MDM and the application of MDM to the rotor system of centrifugal compressor or other system.更多还原