Biologically Inspired Techniques for Autonomous Shop floor Control

Abstract

Currently, the conventional manufacturing systems, such as the Flexible Manufacturing Systems (FMSs) are unable to adapt to the complexity and dynamic of the manufacturing environment. These systems activate the automatic operations by using the pre-instructed programs and should be stopped to re-program and re-plan in case of changes of the manufacturing environment, which reduce the flexibility of the systems and increase the downtime. Self-adaptation to disturbances is a crucial issue in the development of intelligent manufacturing systems, which keeps the manufacturing system running and avoids stopping completely. Many methods for the management of changes and disturbances within manufacturing systems were proposed in the literature such as rescheduling (Vieira et al., 2003; Wang et al., 2008), reactive and collaborative approaches (Monostoni et al., 1998; Leitao & Restivo, 2006). These methods can be classified by two criteria: reconfiguration and autonomy (Saadat et al. 2008). Reconfiguration is to rearrange and restructure manufacturing resources that require the rescheduling method (Vieira et al., 2003) and reconfigurable ability of manufacturing systems (Park & H.W. Choi, 2008). A dynamic rescheduling is done when there is an occurrence of disturbances such as the machine breakdown, malfunction of robot or transporter with long recovering time. Here, a new schedule is generated when the current schedule is affected by disturbances (Vieira et al., 2003; Wang et al., 2008). Autonomy allows the system to recover autonomously without modifying scheduling. Reactive and collaborative methods were proposed following this criterion (Monostoni et al., 1998). Reactive method is an autonomous control of an entity to overcome disturbances by itself, while the collaborative method is used for a cooperation of an entity with other entities in order to adapt to disturbances. These methods are suitable for disturbances, which are not necessary to reschedule. In order to implement reactive/collaborative methods, the distributed control architecture is required (Park & Lee, 2000). The control architecture changes from centralized control of non-intelligent entities in hierarchical structures of the FMSs towards decentralized control of intelligent entities in distributed structures.