Control charts, as had been used traditionally for quality monitoring, were applied alternatively to monitor systems' reliability. In other words, they can be applied to detect changes in the failure behavior of systems. Such purpose imposed modifying traditional control charts in addition to developing charts that are more compatible with reliability monitoring. The latter developed category is known as probability limits control charts. The existing reliability monitoring control charts were only dedicated to binary-state systems, and they can't be used to monitor several states simultaneously. Therefore, this paper develops a design of control charts that accommodates multi-state systems, called here as the Angular Control Chart, which represents a new version of the probability limits control charts. This design is able to monitor state transitions simultaneously and individually in addition. Illustrative system examples are implemented to explore the monitoring procedure of the new design and to demonstrate its efficiency, effectiveness, and limitations.

翻译：传统上用于质量监测的管制图表,用于监测系统的可靠性;换句话说,可以用来检测系统故障行为的变化;这种用途是,除了开发更符合可靠性监测的图表之外,还强制修改传统管制图表;后者开发的类别称为概率限制控制图表;现有的可靠性监测控制图表仅用于二元状态系统,不能同时用于监测几个州;因此,本文件开发了一套包括多州系统的管制图表设计,此处称为角控制图,这是概率限制图表的新版本;这一设计能够同时和单独地监测状态的转变;还采用说明性系统实例,探索新设计的监测程序,并展示其效率、有效性和局限性。