STEMMER IMAGING

Direct connection to a PLC or controller

In many industrial applications it is not only necessary to trigger the system and to provide pass/fail signals, but to have the system tightly coupled with the wider plant control system and as such, it must be capable of supporting a variety of interfaces (i.e. Ethernet, serial interfaces) in order to communicate bi-directionally. Process parameters, test tolerances and job selection are needed for configuration of the system.

Component coordinate measurements, inspection results, complex test protocols, statistics and error images also need to be passed back from the vision system to the control system.

Modern vision systems have built-in driver modules that enable easy integration with factory floor data networks. In addition to the classical networking TCP/IP protocol, industrial protocols such as Modbus, ProfiNet or Ethernet/IP are often supported. Using these protocols for communication, data can be easily exchanged with other industrial systems on a network.

Other communication interfaces that are not based on Ethernet such as Profibus, DeviceNet etc. are often realised with the help of additional third party modules.

Industrial communication architectures

In recent years, the inter-connectivity of factory systems has increased considerably, under the banner of Industry 4.0 and Industrial Internet of things (IIoT). This requires that there are some common communication frameworks across a broad range of industrial devices and systems. One that looks to cover many of the requirements is OPC UA. OPC Classic was a Microsoft-only interface that was used in industrial sub-systems. OPC UA, however, is platform-independent and has wide industry acceptance. OPC UA incorporates client/ server and publish/subscribe functionality, with encryption and access control over an IP network.

In June 2018 the German manufacturing and engineering industry body VDMA published an OPC UA companion specification for machine vision systems named OPC UA Vision, to allow a common OPC UA interface to all types of vision system. Our own Common Vision Blox SDK also has an OPC UA tool to allow communications in an OPC UA-enabled factory.

User interfaces

Depending on the application, vision systems often require a human-machine interface (HMI) for supervising the results during operation, for changing of test programmes, or to enable a dynamic adaptation of settings. In this process it is important that the user interface is easy to use and only allows adjustments that the user is authorised for.

For such use the programming interface is often inappropriate due to its complexity. Instead there should be a possibility of showing only reduced user interfaces where the access rights of the individual user can be limited. Some systems even provide user logging so that changes to a system configuration can be monitored as required by standards such as 21 CFR