Commonly used maintenance strategies vary from simple ones such as Corrective Maintenance (CM), which is performed upon system failure, to Preventive Maintenance (PM) where maintenance actions are taken at scheduled time intervals. Both strategies, however, have limitations. Recent advances in sensors, control systems, software engineering, and communication technology have prompted manufacturers to move towards the condition monitoring of system health. Maintenance is performed based on the observed system condition, which is referred to as Condition-Based Maintenance (CBM). This presentation gives a comprehensive introduction to CBM, and introduces a method for CBM scheduling for systems with multiple failure modes. It is observed in some applications that the hazard rate corresponding to each failure mode depends on both time and system state. The system state stochastically degrades, and the degradation rate is often a function of time and the degradation level at that particular time. A maintenance alarm is used to signal when the degradation reaches a threshold value. A new joint model is developed for the stochastically dependent time-to-maintenance due to system degradation and time-to-failure of different failure modes. The model is then utilized to obtain the optimum threshold value that maximizes the system’s availability over its life cycle, or, minimizes the long-run cost per unit time. A illustrative example, using real-life data from a reliability test of communication systems, is provided to demonstrate the application of the approach.
2. ASQ Reliability Division
ASQ Reliability Division
Chinese Webinar Series
Chinese Webinar Series
One of the monthly webinars
One of the monthly webinars
on topics of interest to
reliability engineers.
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Division members only) visit asq.org/reliability
) /
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3. 1
INTRODUCTION TO CONDITION-
BASED MAINTENANCE
(基于系统状态的维护--简介)
Chinese Language Webinar Series
American Society for Quality, Reliability Division
Dr. Liu Xiao
15-04-2012
13. 11
生物学中的“内在随机性”
“… Genetically identical animals kept in as
similar an environment as possible will not
behave the same upon exposure to
environmental carcinogens. While it is
possible to estimate the proportion of animals
that will develop a malignancy at a particular
exposure level, there appears to be a random
element determining which particular animals
will develop tumors … ”
-- Brennan, P. (2002) “Gene-environment
interaction and aetiology of cancer: what
does it mean and how can we measure it?”
Carcinogenesis 23, 381–387
18. 16
例: AH-64直升飞机传动系统CBM
• 通过对轴承S1S2处的振动信号进行实
时监控和分析,从而得到对直升机传
动系统进行预防性维护的最佳时机。
D. Coats, K. Cho, Y.J. Shin, N. Goodman, V. Blechertas And A.M.E.
Bayoumi, “Advanced Time–frequency Mutual Information Measures
For Condition-based Maintenance Of Helicopter Drivetrains,” IEEE
Transactions On Instrumentation and measurement, 60, 2011.
19. 17
例:车辆CBM
• 当冷却剂温度上升到
一定温度的时候,对
冷却剂温度
车辆进行维护,从而
预防因冷却剂流失而
造成的故障。
冷却剂温度瞬
时变化速度
Rabeno, E. and Bounds, M. “Condition Based maintenance of Military
Ground Vehicles”
32. 衰变模型
General path models
衰变模型
Stochastic degradation processes
Brownian motion • Failure time models
Gamma process •
Inverse-Gaussian process • Weibull •
Exponential •
Log-normal •
Joint modeling of degradation
and failure times
Competing
risks model
Joint modeling of degradation
and multiple s-dependent failure
times
35. 33
例子
• 系统性能衰变:dX(t) = X(t) (μ(t)dt + σdB(t))
• 系统拥有K种故障模式
• 故障率:λ(k)(t,X(t)), k = 1,2,…,K
• 系统可靠性函数:
æ K t ö
R(t ) = exp ç-
ç å ò E {l (k )
( s, X s ) | T > s}ds÷
÷
÷
ç
è k= 1
0 ø
t
ò
(k )
for l ( s, X s )ds < ¥ , k = 1, 2,..., K
0
该推导通常十分具有挑战性;因问题的不同,表达式
亦不相同
36. 34
多种故障模式
………
Component 1 Component 2 Component k
潜在故障时 T (1) T (2) T (k )
间(latent
lifetimes)
• 系统故障时间: T = min(T (1) , T (2) ,..., T ( k ) )
竞争失效模型
(Competing Risks Model)