Motion System Design

Human-machine interface


Marc • B&R: The machine designer must be very intimate with the actual operation of the machine from an end-user's perspective. At the end of the day, it's an operator who runs the machine day-in, day-out — not the engineer who designed it. The designer needs to have insight into the mind of the end-user in order to develop a machine and an interface that truly meets the demand for highest value. All too often the end-user is forced to try to recreate the thought process of the designer.

Roy • GE Fanuc: HMI systems can take many forms, from dedicated panel devices to higher-level PCs running Windows and HMI software. On PC/Windows platforms, basic HMI functionality may be augmented with high-level analytics and data acquisition, features more often thought of as SCADA (supervisory control and data acquisition). In the more general case, where the HMI functions as the machine controller and operator interface, the emphasis is more focused on running machines more effectively, measuring performance, and managing downtime more efficiently.

The greater the role of the HMI, the more important it is to select one with a high degree of scalability — one that provides operator controls and connectivity to supervisory systems. In motion applications, HMIs must also be able to respond quickly to commands as well as unanticipated situations requiring complex maneuvers.

To maximize productivity, HMIs should display information in the context of the machine state. It's not the job of an operator to navigate to the correct screen at the correct time; it's the job of the HMI to react to machine conditions (the machine context) and deliver displays appropriate for the current state.

Today's HMIs must also deliver a wealth of information, from operation manuals to troubleshooting guides. They should not only run, but also help maintain a machine. They should track downtime history and capture reason codes, and take responsibility for the lifecycle of the equipment.

Eyal • Unitronics: From the operator's point of view, the HMI is the communication focal point, the “ear and mouth” of the machine, accepting commands and directions while displaying processes, values, results, errors, and other status messages. This calls for an intelligent interface with built-in diagnostic qualities and immediate access to real-time information required to troubleshoot common machine problems. From a PLC hardware perspective, this means having access to internal registers and program variables.

The right HMI implementation provides not only built-in diagnostics — eliminating the need for external testing equipment during troubleshooting — but also increases the operator's overall productivity:

  • It may replace most printed documents, providing online help, operation “wizards,” and even tutorials

  • It allows international implementation of a system by using more graphics and less text, being less language dependent

  • It facilitates operation using color-coded icons, values, and gauges, guiding the operator within the normal operation envelope

  • In a well-designed system, it consolidates all relevant information to one screen, popping up only the values and statuses that need immediate attention

  • Using a combined HMI and PLC can save development time, wiring, and component cost as well


Marc • B&R: The main challenges involve complexity and usage needs. Allowing operators to control a complex machine in a way that hides the complexity is the first test. The HMI needs to be intuitive and simple, yet should not limit the operator's interaction with the machine. Second, different operators and assorted machine operations require different levels of user interface. What works for one might not be the optimum for the other.

Roy • GE Fanuc: The greatest challenge is to develop a HMI that delivers the correct information at the right time, based on the context of the machine. This requires more than just knowledge of the machine. It may require knowledge of the process — what part is being manufactured and what other actions are required at this station, from visual inspection and data collection to operator management and inventory requests.

Maintenance of the HMI is also extremely important. If it's down for some reason, how quickly is a spare available? Are backup programs ready to go? Are they under version management? How easily are they downloaded to the HMI? Do they require a PC and cable connection or simply a Compact Flash memory card? Motion system HMIs are also becoming part of the setup process, delivering the ability to move the machine, save positions, store actions, and then take over operation in an automated manner.

Eyal • Unitronics: The main challenges result from the complexity and amount of data that needs to be consolidated, displayed, and controlled. Complex motion control systems usually handle multiple-axis motion, hundreds of I/Os, infinite scenarios, and typically have distributed control. In addition, a motion system generates constant changes that need to be updated and monitored, but constant update of a graphical representation on an HMI may result in poor performance or, worse, will be hard to follow. The HMI should be adapted to human ability to track and respond.

One way to represent constantly changing information is to use trend graphs, rather than showing specific movements. A well-designed HMI shows a synoptic view of the entire system, giving operators a quick overview and allowing them to “zoom in” or “dive” into a specific area or component for more information.


Marc • B&R: The biggest area of opportunity stems from something called context-sensitive elements. This means that the operator sees only those elements pertinent to the current operation; with an older HMI, everything had to be present, creating a vast amount of (now) unnecessary information. Reducing the information present to the operator greatly increases system usability. The same applies for operator controls. By giving the operator command choices that are currently relevant, machines become so much more useable.

Roy • GE Fanuc: HMIs are taking on additional roles as teaching tools and have become an integral part of equipment setup, in addition to managing ongoing machine operation. There's also a greater shift to becoming aware of machine states (context) and automatically delivering information important to the decision process at hand. One scenario might include a troubleshooting procedure: Machine is down; automatically highlight typical key causes; enable a drill down into one and see likely causes for that condition. In this scenario, the HMI delivers an “intelligent” interface to the machine, reacting to current states and displaying results as appropriate.

Eyal • Unitronics: Easily implemented HMI reduces total cost of ownership and is more attractive to operators, maintenance workers, and owners. Using a combined HMI and PLC allows unified developing tools (to develop PLC logic and HMI from a single platform), resulting in a faster time to market.


Marc • B&R: HMIs will further evolve through improvements in interface technology, such as better displays, wearable displays, command elements, and language input/output. At the same time, the use of computing power to better present information and predict an operator's needs will lead to more intuitive HMIs that make it easier and safer to operate complex machinery.

Roy • GE Fanuc: The next generation is just around the corner. Tools are now becoming available to create “context.” Variables are now defined in the context of an “equipment model,” which highlights both their location and relationship by the function they perform. Additional context will define data relevance to different users, such as variables an engineer only has access to, variables for an operator, or specific variables for the quality department.

Context will eventually include the cause and effect relationships of variables — for example, this speed will impact that torque, or this limit switch will stop that travel. If a machine is down, the cause and effect context will immediately enable automated troubleshooting, displaying the information an operator needs to quickly access a situation.

Machine builders will spend more time developing context models and less time developing interface screens. Screens will become the automated function of the HMI, automatically delivering appropriate views for operation, troubleshooting, and process workflow management, based on the current state and process knowledge that is now an inherent part of the control system.

Eyal • Unitronics: Just as the cell phone is becoming less of a communication device and more of an entertainment device (with embedded camera, music and video player, and Internet browser), mobile phones and wireless PDAs will have an increasing role as HMI command and control centers. The use of the Internet and fast communication technologies will increase the use of browsers (local and remote) as consolidated HMIs. Voice operated and voice response systems will also increase in use; voice recognition technologies are emerging with better quality and accuracy, with industrial applications already available, such as “pick by voice” logistic solutions. In a futuristic scenario, a 3-D HMI will allow “virtual walkthrough” inside machines, mainly for inspection and troubleshooting.

Meet the experts

Marc Ostertag
B&R Industrial Automation

Roy Kok
GE Fanuc

Eyal Saban
Photo courtesy of B&R Industrial Automation.

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