The equipment module model defines the relevant module characteristics which need to be captured. The configuration methodology requires an equipment description that is transparent and understandable. The reasoning behind this requirement is the need to identify what information is necessary in order to establish a configuration. This information also needs to be structured in order to become semantically understandable. The XML format is also used here for the equipment module description, thus its structure will be provided through an XSD file.
The definition of the equipment module capabilities is central to enable the matching of available capabilities against required ones. The definition of the module capabilities allows the configuration method to identify those set of modules which have the capability to fulfil the given assembly process requirements. Therefore, this information needs to be contained in the equipment module description. In addition, the assembly processes need to follow the established standard descriptions. For this reason, the equipment module description will simply include a node for capabilities, where you can set a number of specific assembly processes that follow the classifications and terminologies established before in section 4.2.4. The use of overall classifications and terminologies guarantees the ability to compare capabilities between different module vendors, and more importantly to map these to established set of requirements, which is the trigger of the configuration process. The equipment module physical descriptions required for the configuration are the physical ports. This work focuses solely on the connectivity aspects, thus other physical consideration are not covered here. It follows from this that physical ports are the only physical description required which needs to be in line with the standard interface definitions. For completeness of the model it was included the ability to define reference coordinates for the physical ports. This aspect is not used in the configuration process since the assessment for plugability can be made by checking if a combination of ports has a established interface. The ports also provide characteristics of type, namely:
· Physical Fit – Ports that provide only physical connections with other ports. · Product Fit – Ports that provide connection for interactions with the product.
72 These port types are quite important to maintain, since only the physical fit is considered to have a standard interface description. The product fit is an open port that is not considered as an interface in this work. Nevertheless, the model allows for this to change in a future enhancement of the configuration methodology that includes the product descriptions. Figure 4.10 provides an example where a gripper is attached to a robot to establish a physical fit, while highlighting the importance of the product fit to achieve valid configurations.
Product Gripper Module
Robot Module Physical Fit
Product Fit
Figure 4.10 - Example of Equipment Connectivity Issues
The XSD for the physical ports is established based on what has been described and can be seen in Figure 4.11.
The final required description for the equipment model is business information. The crucial information required for the configuration methodology in this section is cost. The equipment modules description has to contain what the cost of the module is. However, this is not considered to be a straightforward number. The concept of MAS presents two different business solutions for cost, the buying of the modules and leasing of the module (EUPASS [4]; Maffei [130]). This needs to be described in a way that caters for the three possibilities that arise (just buying, just leasing or both). The lease option also requires an extra definition for the availability of the module. This characteristic can also be used for identifying available and unused modules for reconfiguration purposes.
73 Figure 4.11 - Physical Port XSD Description
The delivery time is an important consideration for cost, especially taking into account the reconfiguration of a system. So, it is established as the average time to deliver the specified module. Another aspect is the preferable collaboration, which contains information to drive equipment modules to interact with preferred modules suppliers. This is introduced because industrialists tend to cooperate with one another within groups, which they want to maintain. Thus, when present, this definition would force configurations to use preferred supplier if the configuration solution is possible using preferred modules. The description also allows for an added value to the collaboration, meaning it is established a percentage to use to discount the cost. This is an important characteristic that is expected to be used when module supplier has several types of modules. The final attribute of the business information establishes the owner of the module. This information is important to determine the source of the module, but also in the case of reconfiguration it allows the method to readjust the values if modules are already present.
The final node within the equipment module is the configurability strategy, which is a simple weight matrix that attributes which configuration indicators are more relevant to the equipment module (Figure 4.12). To understand the proposal of this node one needs to look at the previously defined configuration attributes. It is clear
74 that some modules will be cheaper, others more accurate, others quicker, etc. Therefore it is only logical that module suppliers want to influence an automatic configuration by establishing priorities among these attributes in order to increase the chances of participating in a system configuration. This way, the module suppliers have the ability to influence the configuration strategy of the equipment modules playing to their strengths. It is clear that a cheap module might want to put emphasis on this aspect to collaborate with other cheap modules. On the other hand a very precise module might want to value this aspect more. The idea here is to provide the module suppliers with the means to influence how their module will try to fulfil its objective of being selected into a MAS configuration. The total value of the sum of all the elements of this matrix is always one.
Figure 4.12 - Weight Matrix for the Configuration Attributes of the Equipment Module
In summary the equipment module XSD contains all the described characteristics, divided into four main nodes, namely Module Capabilities, Module Structure, Business Information and Configuration Strategy. An overview of the equipment module XSD is provided in Figure 4.13.
75 Figure 4.13 - Equipment Module XSD Overview