How to update an HMI
Upgrading human-machine interface (HMI) hardware, software, and applications can be an efficient process with limited required development time if these recommendations are followed. See before and after HMI photos.
Most manufacturing facilities use PC-based HMIs to operate and monitor automated equipment. Unfortunately, just about every one of these facilities has HMI software or hardware that is, or soon will be, obsolete (see Figure 1).
This article will provide pointers for efficiently upgrading from one PC-based HMI operating system to the next, from one version of HMI software to the next, or from one HMI software supplier to another—all while minimizing rework of the existing HMI graphics, programming, and configuration.
The dreaded operating system upgrade
Typically triggered by a PC hardware failure, upgrading the operating system (OS) on a PC-based HMI can be difficult for a variety of reasons. To perform this type of an upgrade, the issues listed in Table 1 must be evaluated and addressed.
Typically, the first step is consulting the HMI software vendor to verify what HMI versions are compatible with the new OS. However, as technology evolves, many HMI vendors are tempted to create new products and disregard compatibility with legacy operating systems.
Table 1: Considerations when upgrading operating systems and PCs
Operating system incompatibility with existing HMI software
Device driver changes
Screen size factors
Physical size and shape
More often than not, the HMI software originally used to design the application has been discontinued, and in order to support the new OS, it must be migrated to different HMI software—not just a newer version of the same software.
If migration is necessary, the application must typically be re-designed, either partially or entirely, which results in high costs related to engineering and downtime. These costs can be reduced or even avoided when purchasing HMI software from a supplier with a proven record and commitment to adopting technological evolution while maintaining compatibility with applications created in previous software versions.
Communication protocols that implement a proprietary physical layer, such as DH+, Profibus DP, and others, require a physical adapter to connect a PC to the proprietary network. Such adapters require custom device drivers so the OS can recognize them. Migrating to a new OS usually requires an updated version of these device drivers.
In the long term, the best approach to avoid or minimize the risks and costs associated with this migration is to replace, when feasible, protocols and networks based on proprietary physical layers with protocols supporting communication through standard Ethernet-based networks. Ethernet has grown as a standard physical network in automation systems. HMI software that provides a layer of abstraction or separation between the communication interface and the tags database will facilitate the new configuration, and it will also aid and simplify future upgrades.
The impact on the HMI software project will depend on the level of isolation that HMI software provides between the communication interface and other interfaces of the project such as graphical display and scripts. More separation or isolation is better.
Hardware migration issues
When upgrading the PC display, changes in screen resolution can pose two common challenges. In the first scenario, a different screen resolution has the same aspect ratio (e.g. migrate from 800x600 to 1,024x768). Some products offer a native feature to scale the graphical interface automatically, so no modifications are necessary to the original application to fit a new resolution. Other alternatives would be off-line automated conversion and, in the worst-case, manual adjustment of the screens.
In the second scenario, both the resolution and aspect ratio change simultaneously, as when migrating from 1,024x768 to 1,920x1,080 while upgrading to 16:9 wide-screen monitors and panels. A cost-effective method to mitigate this scenario is to use the automatic screen scaling capability of the HMI software development platform, if such is available. And, it's also often helpful to design a single new screen that is always visible and shows critical alarms indicators to fill the gap caused by the new aspect ratio.
Often overlooked, mechanical changes must be completed in advance to support the physical size of the new PC, especially when the device must fit in a panel door. The touch screen operation may also change. The HMI software must be compatible with the input method of the new station such as touchscreen, physical keys, and/or mouse. Depending on the original software characteristics, configuration adjustments may be required for the application.
Upgrading from one HMI version to the next
There are many functional reasons to upgrade existing HMI software to a supplier's newest version such as an improved user interface, added features, and improved communication. Another reason to upgrade is to maintain customer support from the software supplier, as most suppliers will be better at supporting their latest version as opposed to older offerings. A final reason to upgrade is to incorporate patches and fixes.
Backward compatibility is a key factor in the cost/benefit decision to upgrade the HMI software version. If the current HMI software supplier does not provide a smooth migration path, it may be an opportunity to switch to another supplier that does, since it can reduce engineering investment for future upgrades (see Table 2).
Table 2: Considerations when migrating to new versions of HMI software
Incorporating new features and graphics
Traceability and authentication
New built-in drivers to replace older custom communication drivers
It's good practice to check the HMI software supplier's release notes for newer versions, not only to find potential issues that have been solved, but to also find new features. New features may enable implementation of new functionality, such as support for multi-touch and gestures.
A machine or process retrofit may involve not only the HMI, but the controllers as well. In many cases, new controllers support tag-based communication rather than just memory addresses. In this case, upgrading the HMI to a version that supports tag integration with the controller will considerably reduce the time needed to adjust the application. It will also minimize configuration errors since the tags will be browsed and selected from the controller, instead of typing them manually.
Newer versions of HMI software often include support for traceability and authentication, features which can ease compliance with regulations and also improve operations.
Next page: Learn about how new software versions improve communication and how to decide when you should upgrade your HMI.