The Smart Electrical Connector as Enabler of Tomorrow's Production
The article discusses the architecture of the intelligent connector, use cases and the resulting requirements for Vision Production Level 4 of the SmartFactoryKL. The result is an expandable data and interface model with which the application under consideration can be realised.
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In analogy to the fourth of five stages of autonomous driving, the SmartFactoryKL uses the term "Production Level 4" to describe a vision in which routine activities are performed by fully automated and AI-supported machines, but in which central decisions are made by humans .
Consequently, a production facility must be designed in such a way that operators, skilled workers and - although to a limited extent - even unskilled personnel have direct access to process information and can intervene for diagnosis, corrective measures or shutdown.
In the modular and flexible production system of the SmartFactoryKL, the connector plays a pivotal role in meeting the requirements of Production Level 4: Connectors link the various production modules with the supply and communication infrastructure by means of a standardised module interface, so that the addition, replacement or removal of production modules and consequently the reconfiguration of the plant, including the creation of a new topology, can be accomplished easily and quickly. It is crucial that mistakes are entirely avoided, which may affect either personal safety or production safety. This results in new requirements for the installed infrastructure:
- Like the entire production process, the shop floor infrastructure must be developed from static concepts to extensible and flexible concepts. Distributed infrastructure nodes, where multiple production modules can be supplied, enable the production modules to be connected to the shop floor infrastructure. In addition, interconnecting the modules with different infrastructure nodes and among each other needs to be taken into account. This results in complex supply structures.
- Increasingly complex infrastructure topologies must be managed in such a manner that the infrastructure can no longer consist solely of passive components, but must also be able to provide information about their interconnection and status (connected, powered). This is an essential requirement for the safe and highly reliable operation of flexible production facilities, which is enabled by the additional functions of the smart electrical connector.
Figure 1 shows the current structure of the Production Level 4 demonstrator. In several production steps, an individualised USB stick is produced on the basis of a studded brick whereby the individual production modules provide individual production services. For reconfiguration, these modules, which are arranged around a common conveyor system, can be re-arranged, supplemented or reduced as required.
Architecture of the smart electrical connector
General structure: The smart electrical connector is designed and intended to connect a production module to the power supply and communication infrastructure. The access to the infrastructure required for the modular production modules will be provided at infrastructure nodes, which can usually supply multiple modules and are distributed throughout the production facility.
The fixed connectors (sockets) are identical for all intended installation locations (infrastructure and production module). Consequently, the connecting cables are designed symmetrically as "patch cables" with two identical free plugs. These specifications reduce costs and complexity. Furthermore, it was specified that the plug is designed as a classic, conventional electromechanical component, while the socket integrates sensors, actuators and a local control unit, which, together with the digital representations of plug and socket and their service interfaces, enable the additional functions of the smart electrical connector.
Physical realisation: The future connector for the SmartFactoryKL demonstration plant is an industrial connector that will be used to connect a production module with an AC voltage supply (380 V) and with an Ethernet-based data communication (up to 10 Gbps).
The companies involved are working together on creating a uniform solution in terms of requirements and mating face to ensure maximum compatibility and consequently the greatest possible user benefits. Moreover, other application scenarios, such as industrial DC-factory grids in production which is of interest for a large user group from industry, are taken into ac-count in the solution finding process in order to further increase the practical advantage of the smart electrical connector while keeping the number of variants as low as possible.
The plug is equipped with an RFID tag that can be read by the RFID reader integrated in the socket as it approaches the socket. The information stored on the tag can then be forwarded to the socket’s digital representative for evaluation via the local control unit. This means that a socket has another data interface at its backside if this is not connected to the data interface passing through the socket, e.g. via a switch.
In addition, the socket is also equipped with an actuator that can be used to trigger a mechanism for secure locking with the plug. Moreover, a further actuator can be optionally integrated to prevent the user from inserting a plug (blocking), an incompatible plug for example.
Digital representation: The Industrie 4.0 platform defines an Asset Administration Shell (AAS) with the purpose to integrate an object (Asset) within the information world and thereby realising the digital twin. The AAS features a standardised service interface ensuring interoperability across manufacturers. In principle, the AAS can be implemented for products with and without active communication capabilities, but a clear identifiability of the product is required in order to link it to the (unique) asset administration shell. Details can be found in the publications of the Plattform Industrie 4.0 .
In the SmartFactoryKL an AAS with a standardised communication interface is defined for the socket and the plug. An essential difference is how they provide data into their respective AAS (Figure 2): The communication-capable socket exchanges data with its AAS during runtime.
As opposed to the standardised Industrie 4.0 communication, however, this communication is manufacturer specific. The purely electromechanical plug cannot actively communicate with its AAS. Consequently, updating its AAS is only possible via user intervention or through routines of the higher-level system.
Use case "Commissioning & Connect"
The SmartFactoryKL connector is designed to ensure the safe commissioning and decom-missioning of a production module, also by untrained personnel. As users are free to choose which plug to be connected/disconnected first, there is a need to lock/unlock the connector safely depending on its condition in order to prevent incorrect mating/unmating, e.g. under voltage/power. In the following sections, to give an example, the use case of commissioning ("Commissioning & Connect") is described in detail.
Status diagram and status data
The safe establishment, maintenance and interruption of a conductive connection are inher-ent functions of a connector. The following states can be derived therefrom (see Figure 3):
- 1. Mated
- 2. Mating / un-mating
- 3. Locked
- 4. Locking (locking enabled) / Un-locking (un-locking enabled)
- 5. Blocked [optional].
The Mating, Un-mating and Locking states are transitional states (dotted arrows). The Blocked, Mated/Un-mated and Locked states indicated in blue in the diagram must be com-municated and anchored in the corresponding AAS.
Sequence diagram and service interfaces
By means of a sequence diagram, the interactions of the actors involved in a use case can be analysed. For the use case under consideration, the actors are the user, the physical socket (SmEC Socket Asset), its AAS (SmEC Socket AAS), the AAS of the plug (SmEC Plug AAS) and the governing system (Infrastructure Execution System, IES).
The five columns as shown in Figure 4 are assigned to them accordingly. The sequence of the use case is run through from top to bottom with two possible starting points: Either the IES requests the user to establish the connection or the initiative is taken by the user.
In both cases, the plug is approached to the socket by the user (Plug-Socket Approach) until the RFID reader integrated within the socket can recognise the plug's RFID tag and read the self-identification stored on it. This is then forwarded to the socket's AAS, where it is checked whether the socket and plug are compatible. For this purpose, the socket requests detailed (type) information about the plug via the IES. After ascertaining compatibility, the optional blocking of the socket is removed.
When the plug is fully inserted, the socket detects when the end point is reached and provides this information to its AAS, where the Mated state is set for both the socket and, via the IES, for the plug. Optionally, the socket’s mating cycle coun-ter is incremented. For the illustrated implementation, locking is performed automatically after the connection has been established.
The sequence diagram in Figure 4 shows the interfaces of the Asset Administration Shells. A distinction must be made here between service interfaces in the sense of Industrie 4.0, which serve the exchange of data with other asset administration shells or the governing system, and (internal) interfaces for the integration of an asset with its AAS (cf. Figure 2).
The former (black, solid arrows in fig. 4) are standardised in a recently initiated standardisation project to ensure manufacturer-independent integration into the governing system, while the latter (black, dashed arrows in fig. 4) are implemented manufacturer-specifically.
Summary: The flexible production system of the SmartFactoryKL was the starting point for the considerations of how to implement an Industrie 4.0 interface on production modules. Requirements for a smart electrical connector were defined in order to support the simple and safe commissioning and decommissioning of production modules and also provide important information for the safe and reliable operation of a production facility. This results in new degrees of freedom for monitoring and design of novel and flexible infrastructure solutions.
Taking into account these requirements, which were developed by the SmartFactoryKL project group "Smart Connectivity", the DKE working group AK 651.0.3 "Connectors with additional functions - Industrie 4.0" is currently pushing forward the standardisation of the smart electrical connector.
 SmartFactory Kaiserslautern: Production Level 4, 2020
 Industry Platform 4.0: Asset Administration Shell in Practice, April 2019
 Industry Platform 4.0: Asset Administration Shell in Detail, July 2019