What makes an HMI excel on the plant floor

A human-machine interface (HMI) can offer engineers different benefits depending on the industry and setting it’s being used in.

By Aaron Block January 17, 2024
Courtesy: Inductive Automation


Learning Objectives

  • Understand what role human-machine interfaces (HMIs) in different facilities.
  • Learn how HMIs are used in different ways to overcome challenges.
  • Learn what general principles and concepts make HMIs the same regardless of industry.

HMI insights

  • Tailoring human-machine interfaces (HMIs) to distinct user categories—business, operators, and investors—maximizes relevance, emphasizing context, real-time data and visual appeal for diverse needs.

  • Industry-specific HMIs excel when incorporating contextualized data, intuitive navigation, and compliance with stringent standards, empowering operators and enhancing efficiency.

When it comes to human-machine interface (HMI) design, there are basic concepts to keep in mind, but no one-size-fits-all solution. Every screen will be unique, with functionality and requirements particular to the needs of its operators, and the more specialized the use, the more critical those differences will be. Three integrators shared their insights about the defining features of how HMIs excelled in the electric vehicle (EV) manufacturing, power generation and pharmaceutical industries.

EV manufacturing HMI addresses user needs

When designing for an EV manufacturing facility HMI, Alex Marcy from Corso Systems stressed the importance of user needs. Not everyone requires the same information, so Marcy recommended dividing the overall user group into three categories: business, operators, and investors/customers.

The business category — think C-suite and managers — is less concerned with the minutiae of the plant floor. Instead, they need large-scale context and high-level key performance indicators (KPIs) so they can answer questions about general operations and make informed decisions. “Business folks are typically from an ISA 95 perspective… they’re not necessarily concerned with what’s happening in a particular workstation,” Marcy said.

In contrast, operators are focused on running a specific process, so their HMI will have a more localized context, emphasizing real-time KPIs, alarms, and production schedules. “We used a Map Component from [Ignition’s] Perspective [Module] and a custom tile set to show their plant floor with equipment. This Map Component sort of simplifies navigation throughout the application,” Marcy said.

Figure 1: Courtesy: Inductive Automation

Figure 1: Courtesy: Inductive Automation

Investors or customers will not see HMIs nearly as much as the other categories but still need the same immediate understanding. “We can also build process flow diagrams to show the flow of material through the process with arrows indicating where things are going, and that will give somebody a visual representation while they’re looking at the equipment.”

Marcy also stressed looks matter for investors. Screens need color, polish and clarity, unlike the grayscale high-performance HMIs (HP-HMIs) that foreground functionality over pageantry.

Power generation HMI on the assembly line

What about an HMI for a company without an assembly line? As Frank Peronace from Kupper Engineering explained, a power-generation facility’s HMI should be designed around a strong organizational hierarchy, supplying contextualized data while making room for a few industry-specific features.

Intuitive navigation is vital for this particular facility because it has a complex system, monitoring 70+ solar fields. “We try to avoid the situation where the user asks, ‘What did I click to get here, or where is this data coming from?’” Peronace said.

A tree-style navigation structure with no more than two layers maintains accessibility while keeping operators orientated within the system. A tabbed interface lets operators view more without having to move from screen to screen, indicating hierarchy and avoiding jarring changes.

Data without context isn’t data at all, only numbers. Pairing context to data can be accomplished in a variety of ways, including grouping sets of trends together, displays that associate a given tag with a location, sparklines and analog indicators for monitoring if a given tag is within spec at a glance.

This plant creates energy from landfill gas, so Peronace recommended something as simple as a fixed banner on the top of the screen to display relevant KPIs like total capacity, total KW output, methane percentage, oxygen percentage and more at all times.

Figure 2: Courtesy: Inductive Automation

Figure 2: Courtesy: Inductive Automation

Some issues are industry-specific. Large solar field systems can experience an influx of nuisance alarms at sunrise and sunset. To suppress these unnecessary alarms, Peronace said Kupper “implemented a system which allows entering the latitude and longitude for the site to calculate sunrise and sunset times, combined with the deadband after sunrise and before sunset to suppress alarms to ensure that alarms received are actually important enough to act on.”

Figure 3: Courtesy: Inductive Automation

Figure 3: Courtesy: Inductive Automation

Pharmaceutical HMI standards challenges

While every industry has its own best practices, a highly regulated one like pharmaceutical manufacturing has a particularly strict set. Chris Monchinski from InflexionPoint (formerly Automated Control Concepts) stressed the importance of following ISA 101 and ISA 88 guidelines when designing a pharmaceutical HMI.

The overview display should maintain situational awareness, meaning the relationship between the operator’s understanding of the plant’s condition and its actual condition. For this facility, a minimalist ISA 101-compliant HP-HMI design gives operators better immediate understanding.

“Widgets that are built [into] the Ignition dashboarding tool allow our user to see at a glance the information that is critical to running that operation,” Monchinski said. “They animate based on alarm conditions, they show them through either standard text descriptions or through gauges and/or charts, the values of data that are important to that operation.”

Figure 4: The overview display should maintain situational awareness so the operator understand the plant's condition and its actual condition. Courtesy: Inductive Automation

Figure 4: The overview display should maintain situational awareness so the operator understand the plant’s condition and its actual condition. Courtesy: Inductive Automation

Giving the operator the ability to customize their screen or “unchain the system” can be beneficial and make all the difference between an intuitive process and a frustratingly clunky one. Integrators or controls engineers may understand the software better, but operators are the floor-level subject matter experts.

“We can add that widget in, and then we can set that to a different location and pull up data for that location. This allows us to not just design screens that are built for the different audiences that we need to consider, but actually build components for screens that we can let our end users [leverage to] define screens,” Monchinski said.

In such a highly regulated industry, design and functionality are often closely linked throughout the integration process.

According to Monchinski, “We’ll build those [templatized] standard modules from the control layer, building the control logic, the control module, the equipment module, and then layer that into the paired user-defined type (UDT) within Ignition all the way up to the templated graphic. So that we’re building these foundational graphics throughout the entire process from a control system all the way up tightly integrated into the Ignition process.”

Back to the HMI home screen

Across a variety of HMIs, certain concepts apply no matter the industry, but others will differ drastically. And those differences are the direct result of operator and organizational needs. Whether that means strict adherence to specific standards or following more general guidelines, what’s important is users carefully consider the industry requirements of any given HMI and achieve the appropriate balance of efficiency and usability. Great practical HMI design begins with talking to people to discover their needs, and ends with solving their pain points.

Aaron Block is marketing content writer at Inductive Automation, a CFE Media and Technology content partner. Edited by Chris Vavra, web content manager, CFE Media and Technology, cvavra@cfemedia.com.


How do you use HMIs and how do they differ in your facility?

Author Bio: Aaron Block, marketing content writer, Inductive Automation