# Condition-Based Monitoring and Maintenance: State of the Art Review
## 2 Literature Review
### Standardization of CBM Systems  
Although CBM systems are well known and are used in many applications with significant improvement, there is no consensus about universal standard. There are barriers in platform, industry sectors, IP issues, etc., to coming up with an open system. Thurston and Lebold [144] discussed the development of open system architecture for CBM and defined the requirements for a general CBM architecture and the framework of the distributed architecture. It was also being evaluated for transition by both Army and Nany programs. The changing role of maintenance is presented from the perspective of life cycle management and identified technical issues of maintenance [145]. A generic model was presented with the total productive maintenance (TPM) and CBM basics, in conjunction with ecology-oriented manufacturing (EOM) and 5S f in attaining organizational equipment maintenance goals [146]. A systematic implementation framework coupled with the standard tools, techniques, and practices has been designed in a large semiconductor manufacturing company. Another generic CBM architecture was developed across different domains with a combined data fusion/data mining-based architecture [147]. Data fusion is extensively used in defense applications with an automated process of combining information from several sources in order to make decisions regarding the state of an object. Whereas data mining seeks unknown patterns and relationships in large datasets, the methodology is used to support data fusion and model generation at several levels. In the architecture, methods from both these domains analyze CBM data to determine the overall condition or health of a machine. This information is then used by a predictive maintenance model to determine the best course of action for maintaining critical equipment. Banjevic et al. [148] used Cox's PHM (prognostic and health management) with a Weibull baseline hazard function, and time-dependent stochastic covariates are used to describe the failure rate of the system with proposed structure of the decision-making software EXAKT. Sundberg [149] provides the economical aspect of condition monitoring and the strategically important considerations inside the maritime industry. Web and agent technologies in condition monitoring and the maintenance of mechanical and electrical systems are presented [150]. The OSA-CBM (Open System Architecture Condition-Based Maintenance) layers are used for the analysis of the reviewed work. Different architectures, methodologies, and tools are proposed by the researchers for the development of agent systems. Few findings report the use of mobile devices. Since the mobile/handheld devices spread markets recently, the effectiveness of those types of equipment for CBM to reduce downtime is unaddressed. The limited methodologies are available for the applications of mobile devices. There is a great potential to use handheld device injunction with web-based system for wider integration and effective use for decision making. It might give easy access remotely since the technologies are evolving faster than ever. Web-sensor open platform could be application also.