In many of today's automation applications, it's common to need to combine different types of control in the same system. For example, a packaging system may need to combine sequence control of heat-sealing bars for plastic film with precise motion control for registration.
The difficulty many companies face in this situation is finding the control systems they need for separate specific tasks, and then making them work together. The ideal choice for these kinds of applications is an automation platform that can offer multi-faceted control to address all aspects of the system's operation. However, before you select a vendor for this kind of application, consider the following requirements:
Integration. Insure the system can combine multiple types of control on the same platform. Typically you would expect to see a system offering the ability to tie together sequence, motion, process, and PC-based control on the same rack. With the additional capabilities required of modern systems, the ability to integrate a PC into the controller is especially valuable.
Engineering time. A key benefit afforded by a true automation platform is the way you avoid having to spend engineering time on making the parts of the system work together. Look for the ability for all parts of the system to share information readily, regardless of what type of control they handle. A bonus is software tools that reduce the amount of time spent on configuration, so you can concentrate on your application.
Network capability. Support for a variety of different networks at different levels is essential. Typically you need connectivity to Ethernet to share information with other systems, and support for a device level network to reduce the costs of wiring the system. Consider some of the more recent, high performance options such as CC-Link, as well as older types of device level networks.
Remote maintenance. Many OEMs are realizing the benefits of being able to troubleshoot systems remotely, saving the expense of service calls for simple faults. A better automation platform will allow you to access the system as if you were connected directly and see all programs and data in its memory for complete serviceability. Typically you will be able to choose a variety of communication methods, such as Ethernet or modem. Also look for features such as multiple programs that permit code reuse and modularization of control programs to quickly isolate code when problems occur.
Performance. Leading edge systems execute their programs in microseconds, allowing even demanding applications such as high-speed packaging to be easily accommodated. Beware of PC-based systems that are actually running their control as a Windows-based task; this soft real-time approach can cause serious reliability problems during operation.
Software tools. Gone are the days of poring over pages and pages of ladder code when programming and debugging your system. Today's automation platform offers a variety of programming formats, some completely independent of ladder logic. Look for options such as:
- Structured Text, Sequential Function Chart, Function Blocks, and Label Programming.
- If your system includes a PC-based processor, then of course languages such as Visual Basic by Microsoft also become options.
- Also look for graphical motion system programming that lets you use virtual gears, cams, and clutches to create the motion program, rather than lines of code.
- Beware of systems that require you to buy separate software tools to configure networks, etc. Typically you would look for this feature to be included in the main programming software.
Backup. What other components can the vendor offer to address other aspects of your system? Is there an HMI option for operator control? Motion control needs servos or drives to complete the solution. Is there software to handle communications to other systems, such as an OPC server?
If your application is more complex than average, then considering these issues can help guide you toward a more appropriate automation platform that will address your needs.
