Availability analysis of series redundancy models with imperfect switchover and interrupted repairs

Abstract

Article citation info: Shim J, Ryu h, Lee y. Availability analysis of series redundancy models with imperfect switchover and interrupted repairs. eksploatacja i Niezawodnosc -maintenance and Reliability 2017; 19 (4): 640-649, http://dx.doi.org/10.17531/ein.2017.4.19 IntroductionThe availability of a system is defined as the probability that the system is operational at a point in time [16,25]. High availability is becoming a must in various domains such as telecommunication networks, power plants, and industrial and manufacturing systems [5, 16,27]. During the past years, many efforts have been made to improve system availability.Redundancy is a common approach to improve system availability [6]. The redundancy service can offer different levels of availability depending on its redundancy model. Availability Management Framework [16] defines the following four redundancy models: 2N, N+M, N-way, and N-way active. The 2N redundancy model ensures one standby replica for each component in active mode. The active components execute the service, while the standby components are ready to take over the active role if the active components fail. The N+M redundancy model extends the 2N redundancy by allowing more than two components to be active or standby. In the N+M redundancy, N represents the number of components in active mode and M represents the number of components in standby. The N-way redundancy model extends the N+M redundancy allowing a component to be simultaneously active and standby for different services. Lastly, the N-way active redundancy model differs from the 2N, N+M, and N-way redundancy, as it does not support standby service assignments, but allows a service to be assigned active to several components [16].The availability analysis of a redundancy model is based on analyzing the various states that the model undergoes during its lifespan [21]. The analysis mainly focuses on capturing the failures that cause the system to switch to a faulty state and the repairs that shift the system back to a healthy state [6]. Since the occurrence of failures is erratic by nature, stochastic models have been used to conduct the availability analysis [20]. Markovian models have been extensively used for this purpose because of their expressiveness and their capability of capturing the complexity of real systems [1,[23][24][25]. One of the major problems of using Markovian models is that a large number of states are required to represent the model accurately [1]. As an alternative, Kanso et al. [6] various redundancy models and evaluated the availability by using the Stochastic Petri Net Package (SPNP). Kim et al. [9] analyzed the networking service availability of 2N redundancy model with nonstop forwarding by using the SPNP. The analytic-numeric methods of SPNP provide the capabilities of solving the Markovian SRNs but fail for non-Markovian SRNs. Actually there is no reason to assume Markov property in modeling of repairable systems [11]. Recently, modeling and analysis of repairable systems with general rep...

Availability analysis for a multi-component system with different k-out-of-n:G warm standby subsystems subject to suspended animation

“…The following studies have considered SA in single k-out-of-n:G systems with hot standby [3], cold standby [17,25] or warm standby [27,28] components. Moghaddass [20] et al studied a k-out-of-n:G system with hot standby components and R repairmen.…”