As manufacturing and extraction industries worldwide become more complex and increasingly automated, the efficacy of human machine interfaces (HMI), the portals through which operators exchange data with networks, becomes more significant.

If done well, the HMI will support efficient and meaningful communication and control. However, if it is clumsy or difficult to use, it can become a bottleneck that diminishes the value of the automated system.

“In the early days of industrial automation, system designers attempted to automate everything and remove the human operator – whom they considered the weakest link in the process control loop – entirely," says the 2007 article "Human in the Loop" in the ABB Review. Its authors say that the human operator clearly is an integral part of any automated control loop in almost all industrial applications of any size. Understanding and maximizing collaboration between the control system and the human operator is essential. Furthermore, the article says, a systematic design approach "is crucial for reasons of safety and optimum system performance."

IHS Technology Industrial Automation Analyst George Dickinson identifies three industrial HMI developments that will be important to watch over the next five years. First is the adoption of multi-touch capacitive touchscreens, second is enabling HMIs to communicate with mobile devices and third is the development of modern HMI software.

Two research reports published by IHS focus on HMI, an operator terminal report that covers more “traditional” HMI and an industrial PC report that includes data on panel PCs, which can be used as HMI. The former report sizes the market for operator terminals at $2.3 billion in 2013, and expects it to grow to $3.1 billion in 2018. That represents a compound annual growth rate of 6.2%. Combining recent figures for operator terminal and panel industrial PCs gives a combined HMI market size of $3.1 billion in 2012; that is expected to grow to $4.4 billion in 2017.

The distinguishing feature of multi-touch HMIs is that they sense simultaneous touches in more than one location. The combination of the location and motion of fingers (called gestures) can change displays through different levels, zoom in or out and trigger events. These features are taken for granted on smart phones and tablets but not so much on industrial HMIs.

Although multi-touch screens are efficient, easy and rapid to operate and learn and have a number of other practical advantages, their appeal is not limited to performance. Younger workers who are entering the labor force expect to see HMIs that function like the devices that are part of their everyday lives. As a result, they are creating a demand for change.

While multi-touch is a major trend, resistance exists to adopting it because developing the software is expensive, says Dickinson. There has to be a perceived problem that it solves in order for it to be widely adopted, says John Krajewski, of Invensys. On the other hand, Doua Yang, Industrial PC product specialist at Beckhoff Automation, says that when factored over the lifetime of a machine, it is not much more expensive than single touch.
“If the implementation of new technology such as multi-touch HMIs can help a builder to outsell its competition, the HMI has paid for itself,” says Yang.

Much value may be found in using multi-touch. New users can be trained quickly because they are used to interfacing with their personal devices. Therefore, the training can be focused on understanding the process rather than the interface.

Operators can access options by tapping them on the screen and enlarging or shrinking them as needed. They can drill through layers of screens with a simple gesture. They can execute commands up to three times faster than with a traditional touch screen. Menus and submenus can be replaced with easy-to-understand intuitive symbols, eliminating complex screen layers. Two-hand touch can be required for safety critical functions to prevent accidental operations. (See some of these features in action.)

A new HMI standard is expected to be issued before the end of 2014. Image source: COPA-DATA.A new HMI standard is expected to be issued before the end of 2014. Image source: COPA-DATA.
Since multi-touch panels rely on body capacitance to disturb the electric field at the point of contact, there is no pressure or deflection applied to the screen, improving their durability and life expectancy. Typically, industrial-grade multi-touch HMIs have a protective overlay of glass or polycarbonate. And, because they are sealed, they can be hardened to operate in harsh environments. They also are relatively easy to clean, which is a plus in the food, beverage and pharmaceutical industries.

Dickinson’s second trend, the mobile HMI, improves the sending of process alarms quickly and directly to the personnel who need them. In addition to the alarm, personnel will be able to see data to identify what is happening and why. This information will allow the technicians to respond to the most critical problems.

One of the most valuable applications is to track important variables and check trends in order to catch problems before they occur. “On iPhone and iPad, we Web-publish reports; you can pull up screen snapshots or customized reports,” says Tom Craven, GE Intelligent Platforms operator interface product manager.

A case history reported in Plant Engineering illustrates this function at a Del Monte vegetable processing plant. Operators previously had to move from machine to machine to make sure that the process was going smoothly. The time lag meant there could be wasted product before a problem was spotted. "Now we're not running product that has to be thrown away. We can take actions much quicker," Automation Engineer Christian Nondorf was quoted as saying.

Companies such as Panasonic and DAP Technologies offer tablets and smart phones for industrial environments. The devices will withstand a fall onto a concrete floor and are water and dust proof.

Mobile HMIs can function by tapping into a plant’s wireless network or accessing its SCADA software over the Internet using HTML5. However, HMI apps that run natively on the device, altogether bypassing the Internet, are now available. Some of these can be downloaded from the iTunes store. Two examples are ScadaMobile, from SweetWilliam S.L., and i-View, from ProSoft Technology.

Dickinson’s third trend, modernizing software, has become critical. “A lot of HMI software still has the look and feel based on software that was developed years ago with very little thought given to ease of use,” he says. The benefits of multi-touch and mobile HMIs can only be realized through the modernization of HMI software.

Traditional HMI software, whether for PC or single-point touch screen, was based on drop-down menus, pointing and keyboard devices, which were slow and cumbersome and required training for new users.

“Lack of understanding of human factors, too much emphasis on technology and not enough involvement by operators in the planning phase results in dissatisfied staff,” writes Per Lundmark in Ergonomics – A Systems Approach. He cites the importance of appropriate fonts, colors and shapes for presenting all relevant information in a consistent way. “It is more important for the operator to easily read the actual information than to know where and how to find it,” he writes.

William Zupon, Maverick Technologies' senior control systems specialist, adds some specific recommendations. The HMI layout must support the functions it is required to perform. Information should be presented in meaningful clusters, without trying to squeeze too much onto the main graphic. “Group by process, area, device category, geographic location, or whatever makes the most sense for your application,” he says. The user should not have to drill down more than two or three levels to get to any function and for consistency, group the text color and font by function.

Dave Board, commercial engineer of visualization and information software of Rockwell Automation provides tips, such as staying away from potentially confusing animated 3D color graphics. Instead, he recommends using analog status indicators because “the brain interprets analog more quickly than a number.” The indicator should clearly indicate the normal operating upper and lower limits. Trending of the important operating parameters should be shown on the top screen, and low-level details should be accessed by clicking when they’re needed.

A new HMI Standard, ISA101, is expected to be issued before the end of 2014. It will provide general guidelines rather than specific mandates. For example, it will not specify colors for different functions, but will recommend that "the background shouldn’t contrast with the foreground so much that it gives the operator eyestrain.” It will also provide samples of good designs. In addition, the standards writing committee will release technical reports including HMI Philosophy Development, Style Guide Development, Design Guide Development, Usability and Performance, Purchase Specification and Design Guide for Mobile HMIs.

The three HMI trends noted by IHS's George Dickinson are closely interrelated. Multi-touch capacitive touchscreens are growing in popularity in large part because of their similarity to the interfaces used by consumer mobile devices. Smart phones and tablets are being adopted for HMI functions because they can offer provide many of the useful features of consumer devices. And, finally, software must be updated to enable multi-touch screens and mobile devices to operate most effectively.