Human Machine Interface (HMI) Performance for the Long Run
Design Considerations & How Human Machine Interfaces will Continue to Transform Traditional Manufacturing Automation and Robotics
In the technologically complex world of manufacturing, machine operators and maintenance personnel rely heavily on the information collected and displayed by the plant’s equipment.
While the Human Machine Interface (HMI) application must contain all of the necessary technical capabilities to gather and display the data in a meaningful way adequately, designers must also be aware of how well the system will hold up day in and day out.
The post seems at some of the quality, durability, and environmental features designers should place high on their requirements list.
1. Environmental Factors
Industrial computers are built to withstand a great deal of pressure, heat, and moisture. HMI systems differ in that their nature requires them to be exposed to the right conditions that would negatively impact their performance.
While other automation system components are sheltered safely within a suitably rated ingress protected enclosure, the touchscreen that human operators access regularly remains less than ideal environmental conditions.
Of course, all automation equipment in a manufacturing setting needs to be built to withstand environmental conditions like extreme temperatures and moisture, but for those tasked with designing an HMI system extra care needs to be taken to ensure the more visible components of the interface are robust enough to perform as required despite the less than ideal conditions.
Temperature and moisture may be the most common environmental conditions that need to be considered, but the conditions can also vary by site; some installations may be required to operate in atypical hazards, so the designer must ensure that their design can accommodate a wide range of changing conditions.
Fortunately, HMI designers aren’t left in the dark when it comes to standards. Customers looking for an industrial HMI solution typically gravitate towards those that feature a minimum Ingress Protection (IP) rating of IP66F or IP67F, or those that meet specific NEMA standards depending on the intended installation.
If the HMI is being installed into an inspected piece of equipment or system, it will likely need a UL 6101, ULC, and CE rating.
When it comes to temperatures, as a general rule, most HMI systems are rated for standard operation in temperatures ranging from 0°C to +50°C. However, it isn’t uncommon for a customer to request a system capable of withstanding an even higher temperature range.
Customers attempting to select a system that will stand the test of time will look for an HMI that is rated to operate in conditions considerably more extreme than expected.
2. Visual Considerations
Like any other computer system, user experience is a critical criterion in an HMI. Operators and maintenance personnel will be accessing the touchscreen interface daily, so the design must be intuitive, the screen should remain bright and comfortable to see even after years of near-constant use, it should be responsive to touch (also while the user wears PPE) and the data and controls must be presented. Sometimes, the most massive screen isn’t the best solution depending on where the panel will be installed.
In this case, designers will need to emphasize resolution, color, and brightness. Of the three, screen brightness is arguably the most important visual component of an HMI. As many HMIs need to be installed in less than ideal locations, ensuring that the HMI can deliver up to 800 cd/m2 is perfect.
Since some HMIs are installed in areas with a significant amount of direct sunlight, having an exceedingly bright display will make it easier to see. Still, for best results, the HMI should be installed in more accomodating lighting conditions.
3. Recovery Considerations & HMI Maintenance
No matter the system, nothing how robust or expensive, the HMI will go down. How quickly can it be restored, and how much will it cost to repair it? Unfortunately, when it comes to manufacturing, the cost associated with a malfunctioning HMI is not only the labor cost and materials required to address the issue but also the downtime on the factory floor.
Having a system that can be quickly restored is of vital importance. Like any industrial computer system, built-in redundancy is a sound practice. Many HMIs must be installed and replaced as an entire unit, which can be costly and time-consuming.
Conversely, HMIs that feature add-on modules that can be replaced independently of the more extensive system will be cheaper and quicker to replace.
Since physically installing the replacement unit is just the first step to getting the system back online (technicians may need to configure the new HMI), it is generally recommended that the replacement HMI is pre-configured as much as possible before the field install.
Fortunately, modern HMI systems incorporate removable memory and mobile applications designed to reduce downtime. The technician can use the mobile app to wireless configure the newly installed HMI and offer other benefits such as extended data viewing or system diagnostic functionality.
While it is true that an HMI needs the right technical capabilities, it is equally essential for designers to examine how robust an HMI will be over the long run and for users to educate themselves, whether through online technology courses or field experience, on the long-term uses and care considerations of HMIs.