Author: Carl Richter, Vice President, Engineering and Business Development

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Designing a motion control system includes taking a close look at the efficiency and effectiveness of the design as well as overall cost of the system. PC-based motion control (commonly called Soft PLC or PAC - Programmable Automation Control) lets you cut system design and implementation costs while providing a truly open control solution. With valuable options for a streamline system design, the right PC automation package can help you maintain and update your system while keeping budgetary constraints in line.

Originally taunted as a threat to PLC-based motion control, it wasn't until recently that the seasoned idea of PC-based motion control became a contender in the motion control industry. With annual sales of PC-based motion controls reaching 70 million dollars and an estimated cumulative annual growth rate of 24%*, there is every indication that this technology is here to stay.

Converging Forces

Due to several converging forces, engineers are changing the way they design motion control systems. They are sidelining the PLC-based and proprietary motion control systems and migrating to Soft PLC motion control. But why the shift? The answer lies in pivotal advancements in software, operating systems, processors, I/O hardware and networking connectivity, especially Ethernet. PC platforms provide lightening fast execution ?for tighter and more intelligent system control ?with plenty of room for increased functionality, flexibility and often performance. PLC-based motion controls are designed and built with old hardware, making them expensive to maintain, difficult to upgrade and limited in performance.

Designing the System

The design cycle and integration of a control system can be a challenge even for the best engineers. The first step in the process is to choose the components for your system. Choosing, however, can be harder than it sounds considering that every day an ever increasing number of suppliers are entering the market claiming that their drives, PLC's, I/O or motors are the best available. While ever-increasing competition can drive costs down, it can also create confusion and doubt about which products best meet your system needs. This confusion is also why assigning the same project to ten different engineers will result in ten different system designs.

For years, systems had to be designed using different control platforms and different software packages leading to integration headaches. A truly open architecture is motion control in a PC that allows connectivity to all of the popular networks and motion control companies.

It has been a commonplace marketing ploy for large manufacturers to claim that their solutions are open when in fact they are closed, with little or no opportunity to interoperate with equipment and software from other vendors.

A Common Sense Approach

The shift from PLC's to PC technology offers compelling propositions for most manufacturing companies. Why design machine logic in a PLC, drive logic in a drive and HMI in a PC? Wouldn?t it be more efficient and cost saving to combine PC-based logic and motion control into a single PC platform with a common programming language? It seems like common sense. SoftPLC lets engineers design and test the system at their desk in simulation mode, with or without, the I/O connected. The software is completely integrated and easy-to-use ?significantly simplifying the installation process. Since the software is in one location, you can perform online diagnostics, editing and forcing capabilities. Why spend more for ?smart? drives when their main function is to spin motors when you can purchase inexpensive, off-the-shelf, commodity drives or amplifiers and perform the motion control and process in the PC. In addition, the PC automation approach doesn?t tie you to a specific vendor. Commodity drives and amplifiers can be interchanged, easily meeting costs and user demands.

What to Look For in PC Automation

Today there are many Soft PLC's on the market and the significant growth potential promises that many more will enter the market in the near future. There are a number of characteristics to look for before purchasing a PC-based motion control system. You should ensure that:

• Employs the international standard IEC 61131-3 programming software. The software utilizes ladder logic, function block diagrams, sequential function charts, sequential text, and instructional lists. Adhering to this international standard makes it easy for the end user to modify the program.
  
  
• Has multiple network connectivity capability and that the package is truly open.
  
  
• Is truly real-time. Some suppliers claim that they are using Win32 software but are not truly real-time.
  
  
• Includes a simple easy to use canned package that seamlessly integrates to your motion and process logic. The package should also use Windows® ActiveX® controls and integrate Visual Basic® as needed.
  
  
• Is compatible with the most recent version of Windows software and operating systems including, Windows NT, 2000, XP and 2003 .Net applications.
  
  
• Has the ability to read encoders in high-speed applications possibly using marker pulses.
  
  
• Includes online editing, forcing and diagnostics.
  
  
• Has a dedicated research and development team capable of supporting and applying the software.
  
  

Choosing a supplier is another critical step on your path to entering the PC-based revolution. While there are many suppliers, only a select few have all that it takes to keep you up and running.

When choosing a supplier, keep the following points in mind:

• Be sure that the supplier knows how to integrate the software to the hardware and has a track record integrating PC-based motion control systems. In many situations, there are various pitfalls in PC motion control which only experienced suppliers have the knowledge and know-how to avoid.
  
  
• Can the supplier provide proven developed standard software packages? Examples may include: Winder/Unwinder Algorithms, Advanced Position Control, Electronic Camming capabilities, Cut-to-Length, Registration Control, Electronic Digital Lock, Tension/Speed control and pre-engineered HMI screens. All of these can eliminate wasteful engineering practices and reinventing the wheel while ensuring fast, productive installations.
  
  
• Select a supplier that has a dedicated research and development team ready to further develop, support and apply the application software.
  
  
• It is important to have a partner who has the knowledge and can provide a total solution.

You may be wondering, is it possible to find a Soft PLC and a supplier with all of these traits? The answer is YES! FALCON software developed by Cleveland Motion Controls can fulfill all of your needs. FALCON software is a truly open, easy-to-use application that can communicate with up to six network interfaces simultaneously! At CMC, knowledge and experience is the key to success. With over 10 years in the PC-based control business, and a persistent drive for excellence, FALCON software has evolved into a powerful, cutting-edge application package.

In addition to extensive PC motion control knowledge, CMC has successfully executed system engineering and installations around the world since 1958. Cleveland Motion Control has the knowledge, ability and resources to provide your PC automation solution today!

Many Excuses

Some people are attempting to postpone the PC-based revolution and hold on to market share by putting fear, uncertainty and doubt into the market place. These naysayers state: "Operating systems aren't stable, my computer crashes all the time - the motion control will too" or "Ethernet is non-deterministic."

Utilizing Windows XP Embedded (XPE) for the operating system with VenturCom's RTX® for real-time operation, Soft PLC's can produce, fast, dependable and deterministic motion control that quickly refutes the ?naysayers?. The operating system is carefully built by selecting individual components and application software that become the single executable image loaded into the target system. Components not built in the original image cannot be added or loaded after the fact, making Windows XPE highly reliable and resistant to attack or corruption.

Don"t Be Left Behind!

As with any technology introduction, there are innovators, early adopters, early majority, late majority and laggards, The Soft PLC market is currently in the early adopter stage with some OEM's and users already leading the game. Others will wait and lag behind eventually losing market share. Fortunately, history provides a clear perspective with the following progressions: AC vs. DC motors, AC vector vs. servo, high-speed networks vs. discrete bulk hard wiring and HMIs vs. meters and buttons.

Those who move to PC-based motion control solutions will differentiate themselves from the pack with lower overall system costs, faster design cycles and increased flexibility.
Don"t be left behind.

About the Author

Carl Richter is the Vice President of Engineering and Business Development for Cleveland Motion Controls. He holds a Bachelor of Science from Cleveland State University and an MBA from Baldwin Wallace College. He has 18 years of motion control experience. Carl can be contacted by telephone at 800.321.8072 or by e-mail at crichter@cmccontrols.com

References

*Source: ARC Advisory Group website, www.arcweb.com

Window, ActiveX and Visual Basic are registered trademarks of Microsoft Corporation. VenturCom RTX is a registered trademark of VenturCom, Inc..