Human Machine Interface / Network Infrastructure

Portable HMI gives maintenance the tools to prevent unintended downtime

The sky's the limit.

By Keith Kersten

Among manufacturers, old-school maintenance is increasingly meeting new-era technology. With the advent and implementation of portable human-machine interface (HMI) devices, manufacturers have more equipment information and control than ever before, helping to improve productivity and worker safety. Portable HMI devices give maintenance departments more tools, time and freedom to focus on reducing unplanned downtime.

Advances in portable HMI technology have improved manufacturer's efficiency and decision-making. Packed with maintenance capabilities previously available only on desktop computers or panel-mounted HMIs, portable HMI devices have become the go-anywhere, do-anything dynamos capable of making even the most basic of maintenance programs shine. Even better, they can be tailored to a manufacturer's specific maintenance needs, often complementing traditional panel-based operator interfaces.

Going mobile

As technologies have advanced (batteries, wireless communications), portable HMI developments have used low-power compact electronics. They are small, lightweight and available in cabled and wireless designs. Both perform the same functions, run the same software and communicate on the same protocols. The difference is that cabled devices need a full-time power and communications connection, whereas wireless devices have onboard capabilities for both.

When developed on a Windows CE platform, portable HMIs facilitate the information exchange by communicating with a high-speed network protocol, such as Ethernet. The inherent flexibility of Windows CE means that manufacturers can develop and run customized software to interface with installed control and maintenance software programs.

Because of their versatile open design, portable HMI devices are ideal in distributed HMI architectures when used as thin clients communicating with networked servers. Maintenance personnel using portable HMI devices as distributed thin clients have the power of a computer combined with the mobility of a portable HMI. This allows immediate access to the right amount of data at the right location at the right time. Ultimately, the real value of using distributed HMI through portable devices is that it allows plant-floor personnel to get real time production information for more accurate and strategic business decision-making.

Maintenance on the move

Having faster access to operational information facilitates quicker repair and more accurate corrective actions. With portable HMI devices, users can obtain detailed operating information directly from a machine or a production line, and control or track machine maintenance on the spot.

For example, during routine preventive maintenance activities, a maintenance technician using a portable HMI with maintenance software can be notified of specific machinery problems. Users receive detailed information on procedures, step-by-step instructions and system schematics. Additionally, through the maintenance server, they can access information on machine performance history, spare part availability or machine schematics without having to request this information elsewhere.

Manufacturing operations that extend over a large area, such as in process industries or automotive assembly, will especially benefit from wireless Operators can review and maintain more machines and cover more factory floor because they don't have to return to a panel-mounted device for machinery condition information.

For example, consider an automobile assembly line within an expansive factory floor. Maintenance personnel cannot access the entire assembly line feasibly from one location. To perform routine maintenance on the line, workers need to carry a laptop down the line and later download data or move back and forth to a panel-mounted device. With a portable HMI device, they can monitor equipment remotely by walking down the line. Because operators have access to machine control in hand, they don't need to return to a panel-mounted device to check machine status.

Ultimately, portable HMI devices can complement existing panel-mounted operator interfaces cost-effectively for efficient maintenance and troubleshooting. By using portable HMI devices to perform more complicated tasks, such as troubleshooting, control programming or maintenance, manufacturers can use smaller, less expensive fixed mounted devices to perform machine start-stop functions.

Machine-side troubleshooting

Portable HMI devices also can diagnose problems within machines that stop operating. For example, if a limit switch deep inside a machine fails, an operator with a portable HMI device can identify the faulty sensor.

Without a portable HMI, one would need to call in a control engineer for the repair. The engineer, in turn, would likely use a traditional panel-mounted display to troubleshoot the problem. If it is a sensor fault that's difficult to see, the engineer would have to manipulate the machinery to activate the sensor, then go back to the panel-mounted device to see if the machine activated. This operation might require several trips between the machine and the panel-mounted display--or a second worker to assist--before the problem is even diagnosed.

With a portable device, a single maintenance worker could do the same work directly. The worker can check the machine's process variables to identify the specific part that failed, make adjustments in real time and observe the results directly. And if the worker is using the portable device as a thin client, the machine schematics are available directly from the server.

Maintaining safety-critical areas

Although maintenance personnel usually remain outside safety-critical areas, a safety-enabled HMI device allows them to monitor equipment inside gated areas. Consider an automobile manufacturer that uses traditional HMI devices to monitor a cell of welding robots. Because of the danger of entering an area in which robots work automatically, this area is gated and closed to personnel.

If the welding cell fell short of its production quota, maintenance could use a portable HMI device to troubleshoot the robots. With an enable or "dead man" switch on the portable device, parts of the cell can still run while workers repaired or adjusted other parts, allowing at least some production to occur.

Additionally, using a safety-enabled HMI device, this maintenance can be performed by a single worker, instead of two. A portable HMI device that contained the machine's interface information, e-stop and enable switch, allows a worker to confidently enter a semi-shutdown, gated area, to complete the necessary repairs or adjustments. With the enable switch on, the machinery will remain in its semi-shutdown state and "read" that the worker is okay.

Portable HMI devices are blurring the lines between machine control and maintenance, giving manufacturers an effective alternative and complement to traditional panel-mounted devices. And with the advances in the technology and wireless capability, these tools are increasingly allowing manufacturers to design the optimum maintenance systems for their applications.

Keith Kersten is the product marketing manager for the MobileView product line of the Information Platforms Business (IPB) group at Rockwell Automation. Keith can be contacted at 414-382-2381 or