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Point, click, drag, mix: GUI guides operations on the factory floor.

GUI guides operations on the factory floor.

You're designing a new automation system for your food processing plant. Your colleagues suggest that you consider a GUI (Graphical User Interface, or "gooey"). They point out that GUI is dependable, easy to use, and rapidly gaining wide acceptance as a process control tool. But is GUI right for your automation system application?

The answer is an equivocating "sometimes." The GUI provides many operational benefits - but there is a cost.

What is GUI?

Researched by Xerox, popularized by the Macintosh computer, and introduced to the mainstream consumer by Microsoft Windows, GUI is becoming the interface of choice for millions of users. Three million copies of MS-Windows were sold in the first nine months of its release, and the program is currently selling about 1 million copies each month. What is so attractive about a GUI?

A graphical user interface is an object-oriented system that allows a user to communicate with a computer. By simply pointing to an object on the computer monitor, the user indicates the action desired.

For example, consider the Assign Recipe window shown in the example.

After the user has selected a recipe from the list, he assigns the recipe to a specific mixer by using a cursor to point to a picture of the recipe and dragging it to a picture of the mixer. Automatically, the activity represented on the computer monitor is implemented on the processing floor. In one quick, intuitive motion, the operator has initiated the production process.

The popularity of GUI has spawned a variety of basic platforms. Microsoft, IBM, Apple, OSF and Sun have all developed proprietary systems, with Microsoft leading the pack for industrial acceptance. While each of these GUI systems has the same purpose, each is driven by a unique style guide. It is not enough for a GUI to merely provide a graphical representation of an action - the representation must be consistently applied and interpreted by the user.

There are some not-so-subtle differences among the various GUI platforms. One company decided that its automation package would have the same look regardless of the GUI platform interface. The unhappy result was an application that confused users on all systems.

For the processing floor

The primary advantage of using GUI as an integral part of a manufacturing system is that the graphical interface is user-friendly, easy to learn, and can increase operator efficiency. Add the ability of the interface to mix text, graphics, sound and even real-time video, and you have an exceptional tool that's suited to the most demanding applications.

In today's quality-oriented manufacturing environments, user empowerment is a key concept - and GUI provides user empowerment. The user drives the interface, which drives the processing system. Rather than being stepped through a procedure menu by menu, as with a traditional interface, the user is free to work on multiple applications. In one window, a mixer operator can monitor the production process while simultaneously communicating with shipping using

another window.

For the user, the availability of multiple applications is highly desirable, but it can be a headache. Consider the ubiquitous alarm screen. How does it fit in with the "user drives" philosophy? Does the designer let the user cover the alarm windows with other applications? Should the alarm screen be stationary or should the user be allowed to move it? If a new alarm is sounded, should the alarm window pop to the front of the screen?

One approach to answering these questions in a manufacturing environment is the toe-in-the-water approach. Sensing resistance to the free-for-all windowing approach, some applications have been designed to take up the entire screen with the main window, while still allowing other windows to be called up on top of the main menu. This halfway tactic is unnecessary with a properly designed GUI.

Operators want GUIs

Most operators enjoy the "user drives" philosophy and are able to quickly put it to productive use. They learn to combine windows and displays in useful and creative ways that benefit them in executing their jobs. A well-designed GUI provides user empowerment that boosts morale and stimulates the operator's interest in the output of the process being controlled.

Management occasionally tries to alter the intent of GUI by limiting its options. This is an expensive and often futile maneuver. One company, for example, approved the window concept, but felt it would be best not to allow the operators to move the windows on the screen. Immediately after the system was installed, it was necessary to alter it to allow the operators to align the windows. The moral: Use GUI as intended, or select another interface. Time spent trying to circumvent the GUI philosophy is better spent training users to understand the GUI environment.

Another important GUI issue is dynamic updating. Values, whether shown as characters or as graphical representations of gauges and measurement devices, are constantly changing. In situations where user input is required, and dynamic output is a possible action, the best strategy is to divorce the input from the output. The user input should be collected in a segregated area of the window, or in a separate window altogether.

Consider a situation where an operator is using a graphic representation of pallet storage and retrieval. To correct for tracking problems, it may make sense to permit a user to "move" a pallet on the screen using a pointer, but there is no guarantee that the actual pallet hasn't been moved independently. In this case, a compromise is in order. When the user begins a move, the current state of the pallets is captured. After the move is completed, the window goes into a fast refresh, giving the user immediate feedback. In the case of a timing conflict with the real world, at least the operator will be aware immediately that an error has occurred and will be able to make the necessary adjustment.

The cost of GUI

One issue typically not addressed by GUI advocates is computer resources. It is not a coincidence that the popularity of GUI has increased with the decrease in the cost of computer hardware. It takes a lot of CPU cycles, RAM and disk space to support an effective GUI. For example, the OS/2 system needs at least an 8 MB 486 computer to effectively operate a GUI. MS-Windows will run with less, but it is not recommended if rapid display updating is required. The good news is that the cost of hardware to support an effective GUI has fallen to the $3,000-6,000 range.

So where on the food plant floor does installing a GUI make sense? In the case of simple panel display replacement, it would be overkill. But in situations where an operator must manage a large volume of information in dealing with complex manufacturing operations, GUI is today's best choice. It provides a critical link between man and machine.

Ease of operator understanding, reduced training costs, reduced operator errors, and increased productivity make GUI the first choice when selecting an interface for the processing floor.

Dan Houck is a founder and associate of Insight Automation Systems, Inc. The eight-year-old firm specializes in systems integration for the food processing industry.
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Title Annotation:graphical user interface
Author:Houck, Dan
Publication:Food Processing
Date:Nov 1, 1993
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