Human/Machine Interface Offers Best of Two Worlds

font color=black>HMI software brings operator and equipment together in new ways for more efficient machine control and better communication.

Converting has come a long way from the days of labor-intensive machine setup. With the help of automation, physical material measuring and manual machine adjustment (causing variable accuracy, excessive downtime, waste materials, and astronomical maintenance costs) are a thing of the past.

I/O modules, programmable logic controllers (PLCs), and networks have greatly simplified these formerly labor-intensive operations, bringing new levels of productivity to the factory floor. PLCs, distributed control systems (DCS), and, more recently, PC-based controllers enable the machines to talk with one another and work together in synchronized harmony for better overall efficiency. Yet, bringing people into the process has seemed the ultimate challenge-until now.

Using animated color graphics, the human-machine interface (HMI) complements existing I/O modules, PLCs, and other automation components by using software to provide a graphical representation of machine processes that tells the operator what the machine is doing. This makes machine control easier and more productive, and it reduces errors by successfully uniting operator with equipment.

Opening a Window
As machines have become more complex and sophisticated, it makes more and more sense to have sophisticated software that hides complexities and simplifies operations. Operations can be continuously monitored and controlled from a single HMI screen display acting as an instant window into critical operation parameters such as line speed, build ratios, web splicing, and run time.

Ultimately, the HMI software also performs data-gathering functions that can be tied into factory-wide and company-wide databases to supply up-to-the-minute information to decision-makers from the factory floor to the boardroom.

While HMI technology sounds somewhat futuristic, it has already gleaned unprecedented success in a variety of industries, including automotive, utilities, and material handling. Now, the HMI is poised to make an equally explosive impact on converting, as more original equipment manufacturers are starting to develop machines with an HMI capability built in and converting operations choose to retrofit the technology.

An HMI can be retrofitted by a plant's control engineer, a systems integrator, or a company that provides this product. These retrofits have been occurring in other industries for several years and have brought higher yield and lower downtime with fast return on investment.

From Machine to Screen
The most obvious feature of an HMI is its graphical user interface (GUI), and HMIs running in Microsoft Windows or Windows NT environments are fast becoming dominant.

While there's nothing new about the GUI, what is new is its expanding functionality. HMI software running in a Windows environment not only allows the simple point-and-click maneuverability that has become a standard but also indefinitely expands the realm of possibilities. Yesterday's eight-color "stick-figure" graphics have become today's 16-million-color realistic art, making the relationship between machine and screen more real and apparent.

Touchscreens, from which selections are made by pointing at the appropriate area of the screen, simplify operations even further. No keyboard or mouse skills are required. Touchscreens also are ideally suited for harsh and dirty environments, as they eliminate the need for moving parts in the operator interface.

Additional aids, including tutorials, training videos, and on-line manuals, are available. Multitasking allows several of these programs to run simultaneously, thus enabling an operator to view a training video or reference the manual while the HMI continues to monitor and control the machine.

The HMI also can permit repeatable jobs, whereby a task is created, stored, edited, and retrieved for later repetition. Essentially, the operator interface becomes the single interface between operator and machine.

Wide Open
Windows offers a robust development environment with industry-standard tools that allow machine designers to create equally robust systems. Increasingly, proprietary HMIs are falling by the wayside. The reasons are obvious. Proprietary approaches can represent a steep learning curve, may not integrate smoothly with other industry-standard software and hardware, and cannot easily offer all the features and functionality of software based on industry standards.

Windows-based HMIs are inherently easier to learn, while hidden complexities provide platforms that open up new possibilities not practical with most proprietary approaches. Windows-based HMIs represent a significant step forward in capabilities from the operator interface to the back-end database connectivity.

For example, HMI software can provide scalability from a single stand-alone machine to a multi-node network with connections into a facility's back office systems.

Tools such as ActiveX, Open Database Connectivity (ODBC), and Dynamic Data Exchange (DDE) enable easy exchange of real-time data across multiple applications programs. Data logging, analysis, and networking can all be incorporated into a single chassis, reducing the number of components. One of the potential benefits is the capability to tightly integrate HMI functions and control on a single PC. New technologies also are emerging for communicating to other plant systems such as OPC (OLE for Process Control) sponsored by Microsoft.

Quality Control Made Easier
Beyond mastering machine control, HMI software also can be used for on-line quality control, statistical quality control, and enterprise-wide planning. Equally important is on-line monitoring to give operators a clear picture of what's going on in real time. Beyond simple totals that can be achieved easily with a batch counter, HMIs allow each part of the machine to be monitored. Feedback can allow maintenance people to determine quickly the cause of a web break on a rewinding machine and to reduce the likelihood of the problem recurring. Personnel also can review machine performance during a particular shift using reports generated by the HMI.

Alarms are yet another valuable feature of the HMI. An HMI can annunciate problems using visual and auditory alarms, which can be configured with thresholds to warn the operator that certain conditions have been reached. Alarms can be informational, allowing the operator to decide the appropriate action, or they can trigger specific actions such as turning off the machine or process.

Consider a rewind or printing operation that uses large rolls of source material. Two levels of alarms can be used to indicate low paper and no paper. An informational alarm supplies a warning that the paper supply is low. A reactive alarm shuts the machine down when the paper runs out. Each alarm can be addressed separately, and some HMIs alert remote locations, including links to home computers or pagers.

A growing number of remote capabilities allows system access for increased operator flexibility and peace of mind. In a common configuration, the machine uses a modem to dial a remote number for alarm reporting. Using the same modem, operators can dial into the system to check status.

Recent innovations have increased the reach of remote capabilities. For example, hand-held palm-top computers with a wireless LAN connection and HMI software allow operators and maintenance personnel access to alarms and control points from anywhere within the plant to improve reaction time and operator flexibility.

Alternatively, installing a server option in the HMI allows casual users to access security-cleared areas of the control system through the Internet using industry-standard browsers. Managers can view reports. Vendors can monitor inventory. The possibilities are endless.

A high-end HMI also excels at collecting data and performing basic and advanced analysis. The data can be graphed in various ways to show bar charts, trend charts, histographs, and other graphic representations of quality control. Calculations can include averages, accumulations, rates of change, minimum and maximum values, and last valid value. The collected data can be logged into a relational database for further analysis.

Plugged In
An effective HMI scales to meet the needs of a single machine or an entire enterprise by providing an architecture that can be networked into a multi-node system.

Nodes can be networked through standard technologies such as Ethernet and also can be linked to "high-level" systems such as factory or corporate databases.

A client-server distributed architecture, in which a central server links to viewers distributed throughout the plant, provides greater flexibility and allows easier maintenance of the software.

While making machine control easier remains the main task of an HMI, capabilities extend far beyond the basics to embrace quality control, communications, remote access, and other needs. Today's HMI software, running on Windows-based computers, has the power to enable better monitoring and control; faster reporting and analysis; easier direct and remote access; and smoother integration with business systems.

Whether your needs are modest control of a single machine or factory-wide control of a complex converting process, an HMI can make the job easier, faster, and more efficient by linking you to the process.

Kevin Roach is VP of GE Fanuc Automation's software business located in Albany, NY. Roach is the founder of SensorPulse Corporation, South Easton, MA, and has served as the company's president since 1995. He has provided leadership to software, hardware, and mechanical engineering teams in the industrial automation and control markets for nearly 20 years.

The views and opinions expressed in Technical Reports are those of the authors(s), not those of PFFC editors. Pleas address comments to author(s).

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