Migrating PLC Software
Software obsolescence poses a threat in industrial automation equal to hardware obsolescence and should not be overlooked. Many PLC OEMs offer tools to migrate upgraded software projects to the newest controller revisions.
In industrial automation, software obsolescence is not considered an issue as significant as hardware obsolescence. However, recent trends in control systems, including the increasing popularity of industrial PCs (IPCs), are bringing them closer to modern software upgrade practices.
Traditionally, PLC programming platforms become obsolete once every new hardware generation. The driving factor behind OEMs launching new platforms in recent years is Industry 4.0. As a result, a race to provide the most advanced and integrated automation ecosystems is happening. A single unified application to do virtually anything, from PLC coding to full plant simulations, is a common theme among OEMs.
Figure 1. PLC software life cycles lead to major changes between generations of equipment. Tools are often available to ease the migration process. Image used courtesy of Canva
We need to approach software obsolescence issues the way we approach hardware ones. PLC software life cycles are based on the same cycles as hardware; therefore, users can implement the same type of analysis and strategies. Likewise, software compatibility could become a significant issue when a new PLC platform is no longer compatible with the existing devices, triggering hardware obsolescence. Users must carefully evaluate these scenarios to weigh the potential benefits of the software upgrade against the cost of the software and hardware replacements.
Many of the biggest PLC OEMs in the industry have created tools to upgrade software more efficiently to alleviate this problem. This article reviews some of these upgrade tools from Siemens and Rockwell Automation. We also add a few notes about operating system upgrades for windows-based controllers.
Migrating to TIA Portal
TIA Portal is the integrated automation platform from Siemens. It includes several application modules that used to be standalone programs, such as STEP 7 and WinCC. STEP 7 is the PLC programming software of the previous generation, and WinCC is the legacy HMI programming tool.
On its website, Siemens offers a migration tool compatible with the latest versions of TIA Portal. Also, TIA Portal itself provides an option from the main menu. To migrate a project to TIA Portal, the following steps are necessary:
Preliminary checks. Ensure the correct version of TIA Portal is installed and the project file is in STEP 7 in a compatible version. If this is not the case, the project must first be upgraded to that version of Step7, using the old platform.
Open TIA Portal and choose the “Migrate Project” option from the main menu.
Figure 2. Siemens STEP 7 project migration option on the main screen of the TIA portal software. Image provided by Control.com
Choose the project file, check the option to include the hardware configuration, and start the migration.
Once the migration is completed, TIA Portal will display a message indicating whether it was successful or if there were errors or warnings.
Check the error and warning details in TIA Portal and adapt the program as needed. Once the errors are fixed, recompile the program.
Migrating to RSLogix
The PLC-5 and SLC500 are two legacy Allen Bradley controllers that can still be found running control systems worldwide. Rockwell Automation offers the Project Migrator tool to convert these legacy controllers into RSLogix files. The Project Migrator is available from the Rockwell Automation website and a module in the Studio 5000 platform.
Follow these steps to complete a migration to RSLogix:
Export conversion files. Using RSLogix, we need to export two files that will be converted. The first file is an ASCII TXT file containing all the comments and symbols. The other file contains all the logic and can be either a PC5 or SLC extension, depending on the controller.
In RSLogix, from the Tools menu, choose RSLogix Project Migrator.
Figure 3. Locating the Project Migrator tool from the Studio 5000 interface. Image used courtesy of Rockwell Automation
Next, a wizard will guide you through several steps to choose the conversion files, create alias tags for legacy system symbols, specify the destination path for converted files, and select the I/O migration option.
Figure 4. Selecting the original PLC architecture for project migration in Studio 5000. Image used courtesy of Rockwell Automation
Once the new compilation is complete, you can open the program in RSLogix 5000. If there were any errors, RSLogix would identify them with an added possible conversion error instruction.
Next, finish reconfiguring the hardware and mapping the I/O.
Industrial PCs are increasingly popular, making Windows an important operating system for process controllers. Over the years, Microsoft has been releasing compact versions of its central OS, such as Windows CE (Compact Embedded) and, more recently, Windows 10 IoT.
Figure 5. Windows Compact Edition (CE). Image used with permission from Microsoft, courtesy of Wikipedia.
Upgrading the operating system might include software patches, new versions, or a brand new OS. The process is similar to the process for personal computers. However, one slight disadvantage with PLCs, depending on the point of view, is that they usually are fully isolated from internet access. Therefore, users must do the updates manually.
Another critical consideration to make is compatibility, especially with legacy systems. We would not be surprised to see automation systems still running Windows XP, for example. In these cases, it will most likely be impossible to install a new version of Windows CE or Windows 10 IoT because the hardware might not support it. Therefore, a hardware upgrade becomes necessary.
Industrial control systems do not experience obsolescence as quickly as many other areas of technology. Generations of industrial equipment tend to last many years, but once a replacement is necessary, the upgrades can be very significant. In this area, both hardware and software must be carefully considered and researched before decommissioning a system and switching the controllers.