Motion Control Moves Up

Use of motion control has moved from the periphery to becoming an integral part of automation systems. Applications range from one- and two-axis machining stations to such diverse uses as material handling and packaging machinery.

According to a study by Senior Analyst Himanshu Shah of the ARC Advisory Group (www.arcweb.com), the North American market for general motion control (GMC) shrunk significantly during 2001 and 2002. ARC, Dedham, Mass., predicts a rebound with a compound annual growth rate of 6.2 percent over the next five years. The study cites the greater flexibility, higher performance and lower cycle times offered by new systems versus older ways of designing machines as a factor in this growth.

Food and beverage, semiconductor and plastic and rubber industries, all major users of motion control equipment, are expected to increase capital expenditures, contributing to the anticipated rise in the GMC market.

The study finds that end users in general prefer to use newer controls that employ standards for interfaces, programming languages, physical connections and protocols that all help lower the cost of machinery. It finds further that willingness to deviate from standards by original equipment machine builders in order to optimize application form-factor, reduce cost or shorten time-to-market is “nowhere found more evident than in the motion control arena.”

Templates slash time

Tom Jensen, senior technology evangelist at Elau (www.elau.com), with its North American base in Chicago, says, “The industry is moving toward template driven project management for motion control programming development that can only work when IEC standard 61131-3 programming languages are used. Just like when you are using Microsoft Word and want to send a fax, you open up a wizard and follow the instructions, so can you program and configure motion control applications using these templates.” For example, says Jensen, a project that recently took him six days to complete required two-and-a-half months by engineers using the previous system. His faster time, says Jensen, was “mostly due to the use of templates.”

IEC 61131 is the international standard for programming languages, promulgated by the International Electrotechnical Commission. Part 3 (61131-3) gives a detailed description of the four languages and one “organizing principle.” Two languages are text-based—instruction list and structured list; two are graphic in nature—ladder diagram and function block diagram. In addition, sequential function charts, often referred to as a fifth language, are described as a standard method of organizing programs. The standard allows for modularity of code, or “encapsulation,” whereby code can be written and contained within an object with only interfaces exposed to users.

Jensen states that today, the trend is for suppliers to include all five elements within their programming packages. “It’s hard to do a template when the code is wide open and you must cut and paste ladder code into the template,” he adds. “Modularity works for suppliers when you can do a special proprietary function block for customers and yet still protect your code. For example, Elau has written an axis control function block that may take thousands of lines of structured text programming to duplicate, but the user needs only to drop it in the program and connect the interfaces.”

There are several other new trends in motion control beyond programming. Rick Rey, Bosch Rexroth (www.boschrexroth-us.com) product manager based in Hoffman Estates, Ill., cites the ability of new motion control drives to communicate using networking standards such as DeviceNet, Interbus and Profibus. Another key area of advancement, according to Rey, is the drive’s ability to offer preventative maintenance information by monitoring parameters including torque and electric current, compare those to a standard, and send a warning when a value exceeds the upper or lower limits.

Gary Mintchell, gmintchell@automationworld.com.

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