Mobile HMIs Bring New Choice and Functionality to Motion Control

There was a time the HMI consisted of a small LCD capable of showing few-digit error codes. Highly functional versions might include a few indicator lights. Today, those tiny LCDs have been replaced by high-resolution panels with multi-touch capabilities. The HMIs themselves feature processing power and memory that support a significantly higher degree of functionality. They can display sophisticated graphics, performance metrics, diagnostics, and even calculate trend data. But perhaps the key characteristic in our wireless world is that they are networked, enabling them to be accessed remotely by mobile devices, anytime and anywhere.

Remote access offers significant benefits for manufacturing. Off-site users can view the HMI screen as though they were standing at the machine. That enables maintenance and OEMs to troubleshoot faults even though they may not be anywhere nearby. They can receive automated alarms by email or text message. They can run diagnostics, change settings, and upload firmware. Depending on security settings, they can even take operational control. Suddenly, instead of the line coming to a standstill for hours or even days until the repair staff arrives, maintenance can get to work immediately diagnosing and solving issues.

The benefits of mobile HMI access go far beyond troubleshooting, however. HMIs can also deliver performance data and even some basic analytics to large-format display screens. They can leverage connectivity and data logger functionality to send data up to the cloud for more sophisticated analytics that can be accessed by client devices. This supports process control, development of best practices, operations insight, and planning for the future.

The benefits go beyond simple fault recovery. The ability to access any HMI at will makes it possible to pre-empt downtime while reducing staffing demands. It enables a single person to monitor and address multiple geographically separated assets from a single screen, for example. “It really reduces the time for issues to be recognized because that person instantly knows when there is a red area or an alarm in certain locations in the factory,” says Agnieszka Zupancic, senior product marketing engineer at Mitsubishi electric automation. “I think that is probably one of the key benefits of using mobile technology.”

Properly leveraged, mobile HMI functionality can significantly streamline day-to-day operations. Indeed, the most recent trend in remote access is, ironically, using it on site, sometimes right next to the machine. It provides new tools to increase operational efficiency and enable multiple engineers and technicians to collaborate on problem-solving.

Mobile HMI delivers a significant competitive advantage, and manufacturers are beginning to pay attention. “There isn’t a single industry that's not looking for mobility-based solutions,” says Chirayu Shah, marketing manager for HMI business at Rockwell Automation. “They're either adopting it now or they're looking to adopt in the very near future, but everybody has some sort of mobility-based roadmap.”

The flavors of mobile access
For all of the benefits of mobile access, the prospect of connecting equipment to the Internet gives operations and IT the vapors. It potentially makes equipment vulnerable to unauthorized access, malicious code, and unintentional changes. The web server approach was designed to address these issues. With the web-based interface, client devices are never in direct contact with the HMI. Instead, they communicate with it via a secure server.

Users can access the HMI through a variety of portable devices, including laptops, desktops, tablets, and smart phones. They don’t need a dedicated application for the client device, just a web browser and secure sign-on. Web server is a master-slave architecture that lends itself to the use of so-called thin clients - stripped-down mobile devices that typically lack hard drives, external drives, etc. For harsh environments, a number of ruggedized, portable HMIs exist.

Web browser functionality involves an application installed on the industrial device (HMI, PLC, PC-based control, etc.) that enables it to share its screen. The software is typically built-in with preconfigured screens that users can customize as desired. Depending on the package, it can enable users to drill down to the individual components on the machine, from encoders to drives to controllers.

The approach addresses security vulnerabilities introduced by direct access from the mobile client but the data from the HMI still needs to be moved to the server. That typically takes place through a gateway PC or manufacturing execution system (MES) edge appliance. A smart router can be used to establish a virtual private network insulated from the corporate network.

One of the challenges of the web browser approach initially was that screen sizing remained static, which meant that it didn’t scale to smaller devices. As a result, users of smart phones and tablets either had to scan and zoom the larger page or wait until a dedicated version for that device was released. Given the development costs, companies frequently limited the number and scope. iPhone users, for example, might have an app while those using an Android device or tablet would not.

The release of HTML5 mitigated this issue to some extent. One of the features of HTML5 is that it supports webpages that automatically resize to fit the aspect ratio of the web browser window. This improves matters somewhat but it still requires informed design. Pages with graphics developed for a large screen, for example, may not be readable on a smaller device. Given the limited real estate, is essential to ensure that only intuitive data appears.

HMI as server
With the increasing interest in on-site remote access, the industry is exploring new approaches to mobile HMI. It is still possible to use the web server approach on the factory floor but that introduces latencies, security risks, and additional hardware and software costs. An alternative is to use the HMI as the application server. The client devices communicate directly with the HMI over Wi-Fi or the plant network rather than downloading it from the cloud. This makes it logistically simpler. It also eases security concerns and the ongoing conflict between IT and operations technology (OT) staff.

“IT managers don’t typically like to access machines from remote devices but with wireless technology you really don’t need that,” says Zupancic. “All you need is a server IP address and with your Wi-Fi connectivity you can connect to your application easily. There is really no concern in terms of setting up firewalls or things like that, which were always difficult to collaborate with IT to give the appropriate access.”

“Given the right approach, the security woes [of web server] go away but the knee jerk reaction is that it’s unsecured because you have to push everything to the cloud,” says Kyle Reissner, mobility platform leader, Integrated Architecture, Rockwell Automation. “The reason we started on mobile devices inside the OT network layer is because we feel it can reduce the friction for people to realize value. All you need is a secure device on the Wi-Fi system, not routing through the Internet, to be more productive.”

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The functionality is more limited but still delivers benefit for modest cost. It’s a good entry point for organizations who want to explore the possibilities without deep investment. “It isn’t all about big data or regression analysis,” Reissner says. “It’s about giving your electrician the ability to [view data trends] not by being in front of the panel but rather by being in front of the motor, for example. That brings a lot of value.”

With a mobile device that can emulate the HMI, the operator can access the fault-recovery pages of the manual right where the problem is. Some HMIs support simultaneous mobile access by multiple users who each view a different screen. This can be useful during the commissioning process, with each operator handling a different axis or a different part of the process. “They can see different screens but they don’t take control over the HMI itself,” says Zupancic. “Working as a client, you can see individual screens, and one client doesn’t need to refer to the other one for accessing data. You can also set up a read and write option that would give the operator or maintenance personnel privilege to operate the system.”

This brings up one of the keys to implementing remote HMI, which is to define role-based permissions. Through passwords, it is possible to limit the screens each user sees so that an operator, for example, might see performance metrics while a maintenance technician could take advantage of trend data and diagnostics, and have the ability to make changes.

An interesting new wrinkle on this approach involves adding location awareness, also known as geo-fencing, to the system. This addresses concerns about enabling control of assets remotely. The software gives users access to certain screens and functionalities for a given piece of equipment only when device and user are within a specified distance. Perhaps they can see data while at home but can only see control screens when they are on-site, or even next to the machine. Even data display can be restricted as a function of location. “I can walk in with my tablet and within a specific vicinity of a machine, I will get the content from that machine on my tablet,” says Shah. “When I walk away from that area, that content will disappear.”

Rethinking connectivity
The key to this implementation of mobile HMI is to have a reliable wireless network. Not every organization has the funds to deploy an uber robust wireless network in their facility. Even for those who do, coverage is not always effective. The manufacturing environment is a significant source of electromagnetic noise, and conditions are seldom static. All it takes to disrupt Wi-Fi is a change such as a new microwave in the break room on the factory floor, or even dynamic conditions such as tanks of liquid that fill or empty throughout the day.

When Wi-Fi is erratic, wireless phone service may provide an alternative. “With mobile technology, and phones specifically, it’s better because if you have phone service, your internet is pretty consistent,” says Zupancic. “If you’re using iPads or even web browsers on your computer, you have to utilize some other sort of option for internet connection.”

In a recent advance, the architectures don't just use phone service as a backup Internet connection but use the communications functions of the devices for peer-to-peer contact. This is a collaboration tool rather than a mobile HMI tool. It enables users to access data from the HMI and share it with other users in a collaborative team.

This starts with an app installed on the mobile devices lets them act as smart nodes in what is essentially an impromptu mesh network. This avoids the master-slave architecture of the typical web server that prevents the system from functioning effectively when it loses connectivity.

It’s important to note that the cloud is still a key part of the architecture. It acts as a sync point, as the system of record. The devices themselves manage communications with one another, both over Wi-Fi and over cellular service. If the connection to the cloud is lost or the Wi-Fi network goes down, the smart phones can still communicate. The mesh network benefits if one of them has cloud access but it’s not necessary. So long as they maintain peer-to-peer communication, remote access continues.

An example would be an app that enables a phone or tablet to connect to the HMI inside the OT layer to monitor alarms. The data does not need to be sent to the cloud and retrieved by the client device. Instead, the remote device receives the input directly over the OT layer. The peer-to-peer relationship enables communications among devices but also enables users to collaborate by sending information from the HMI to one another. “It is a secured device just like a laptop and allows people to view alarms,” Reissner says. “I can share that alarm on a team board or I can send that to a colleague to help me solve the issue. If I just replicated the screen, it wouldn’t have that collaborative aspect. If I just sent the whole screen, it doesn’t give any context.”

Although mobile HMI is increasingly common and applications exist that enable edge devices to even act as HMIs, don't expect to see the hardwired versions go away anytime soon. Traversing the network introduces a latency unacceptable for time-sensitive operations. Instead of data that updates within milliseconds, it can take as long as two or three seconds. The bigger issue is that all connectivity, however robust, is subject to outages. For sensitive applications, there is no substitute for a hardwired HMI.

By all accounts, the technology is currently in the early-adopter phase but ready for breakout in the next year or so. “Customers realize the value of it and they are the ones who are driving us in this direction because they think this is a game-changer for them, as well,” says Shah.

“I see throughout our end-users it’s really taking off quickly,” says Zupancic. “It’s a little bit in the beginning stage but I see it accelerating in the next two or three years as the technology advances from where we are right now and there is going to be a lot of success with that.”

Acknowledgments
Thanks go to Chris Gottlieb, business manager of Kinetix servo motors, cables, and third-party Interaction at Rockwell Automation and Scott Kortier, senior technical sales at Indusoft, Schneider Electric for helpful background discussions.