Giving Modern Human Machine Interfaces Their Due

Does the term Human Machine Interface (HMI) make you think of a graphic screen used by plant floor operators to help run a piece of equipment? Are you smiling because you know that now there is one screen that has replaced dozens of industrial push buttons, pilot lights, and 16-position selector switches marked with unrecognizable abbreviations? It’s true, even though many people still have oldfashioned mental pictures of HMIs.

An HMI today is a screen that enables right-brained engineers the flexibility to create functional art that beautifully depicts a machine’s operation. The operator can switch screens to command machine operation, supervise machine performance in widgets per hour, or view machine health via maintenance screens. The HMI is the human interface with the machine, or, more correctly stated, with the PLC that it is connected to. Plant floor information from the HMI and PLC is sent to a SCADA system that plant supervisors can then use to generate summary reports at the end of the week.

HMIs have successfully been employed for decades as key instruments used by plant floor operators to run, supervise, and maintain skidded equipment. They have saved manufacturers money by replacing dozens of 30mm push buttons, pilot lights, and selector switches that had needed to be wired to the PLC’s I/O modules. HMIs have become an exciting way to operate machines on the plant floor, tank farm, engine room, packaging area, and many other applications.

Times are changing. In the smart connected world, manufacturers empower workers with knowledge to make decisions based on business-related data and its analysis. In this competitive era, the plant floor operators of yesterday are now the technical users of today. These individuals need to have status information about equipment to the east and west of their production line. They need the tools to predict what will be the raw material status at mid-shift and end of shift. They need to know the overall equipment effectiveness compared to the machine’s designed specifications, compared to last night’s shift, or twin plants in Europe and Asia, all in real time. Employers have found that providing business information to their staff enables them to make better decisions at all job functions and thus increases optimal manufacturing performance.

Companies that employ Industrial Internet of Things (IIoT) tools have been enjoying the many business benefits that come along with them. The data collected via the cloud allows the headquarter staff to view data about any plant, any production line, and any machine in the enterprise. However, if the data is static and remains at HQ only to be reported out at the end of the week, the opportunity to make dynamically integrated corrections or enhancements could be lost. Plant floor operators require live, current data in their hands to make real-time decisions. Companies with IIoT systems quickly realize that the benefit is not the data; it’s that their staff has the tools to make well-informed decisions.

Advanced HMIs: essential for a smart connected world

The IT and OT worlds have converged. IIoT-enabled business systems are closely integrated with the operations at the plant floor. Data is no longer just northbound. Business systems are supplied with near real-time data from production floors across the enterprise. Critical data on supply chain materials and movements can be pushed down to the plants in order to harmonize production and supply. This allows staff at all levels to have the same view into data that is necessary to optimize performance.

HMIs can also play dual roles. They are, of course, used in the traditional way to operate and monitor machines. They are also the instruments on the plant floor that relay collected data to the connected worker about current and predictive manufacturing events. The data can be visualized in dashboards via trend graphs, gauges, or geomaps. Connected workers can interface with the data by setting up their own metric and using ad hoc queries to get to the relevant information they need.

Most controls engineers agree that PLCs and edge controllers are optimized for deterministic sequential control. The IEC 61131 standard offers users multiple languages for machine control, such as Ladder Diagram, structured text, and function charts. These tools have been the proven workhorses of the control world for decades. They continue to be revered today, as they have evolved into effective methods for machine regulation.

As IT moves closer to the machine level, engineers need new tools to tackle plant floor data management, visualization, and network security application challenges. To meet these needs, the control industry is leveraging the benefits of Linux as an operating system for automation controllers. The openness and flexibility of Linux enables engineers to develop the applications they need. In many cases, designers can leverage open applications to help them meet their needs with a packaged application. Grafana is an example of an open Linux visualization and analytics platform that can be used within an HMI to effectively display complex metrics.

Today, HMIs must have the ability to be multitasking, providing industrial control as well as analytic and visualization tools. To meet these challenges, HMIs are equipped with traditional sequential control-based runtimes that operate on a Linux operating system. Controls engineers now have the best of both worlds in a single device: OT for machine control and IT for data analytics.

HMIs with IIoT connection tools

Empowering connected people with information is critical in this globally competitive industry. In order to transport data between IIoT cloud-based systems, plant floor HMI and other control devices are necessities for smart manufacturing.

IIoT cloud systems have multiple formats for the dynamic exchange of data. However, despite these alternatives, Ethernet-based MQTT and OPC UA protocols continue to be widely used. These protocols give engineers the ability to transmit complex data in a very efficient and familiar format. HMIs for the IIoT-connected world will need to be designed to easily and securely exchange information with cloud-based applications using standard protocols such as these.

Integrated HMI and PLC

Advances in technology continue to add features and reduce costs for the devices we use today. This is also true for HMIs. Industrial control manufacturers leverage evolving technology to enhance features, decrease electronic componentry space requirements, and increase processor power all while reducing costs.

Today, integrating your HMI and PLC into one device makes sense. The basic HMI of the past did a great job of replacing physical switches wired to a PLC, saving hardware and wiring costs. Advanced HMIs now are going a step further by taking on the functions of the PLC, helping to reduce duplication. Cost savings can be gained by having one device do the job of multiple devices. Engineers can use one software tool to develop both control logic and HMI graphic screens. There is no need to spend time importing and exporting tag databases between different applications or storing and maintaining two sets of application files. Integrating the HMI and PLC into one high-performance device will help reduce the cost of ownership of any machine.

Modern HMIs The HMIs of today are not your father’s HMI. Modern HMI needs to have the power, openness, and flexibility demanded by the complex applications of this smart connected world. End users continue to look for ways to empower their staff with real-time information while reducing the system cost of ownership. At the same time, engineers are demanding HMIs that can manage their traditional industrial control as well as run data analytics in parallel. It’s time for everyone to start thinking of HMI as far more than a simple screen—this is a device that resides at the very backbone of the smart connected world.

_{Images courtesy of WAGO}

_{This feature comes from the ebook AUTOMATION 2023 Volume 3: IIoT & Industry 4.0.}