By John Martin
If you've used industrial PCs for a while, you know they've come a long way over the past 25 years. Semiconductor companies can pack a lot more power and capabilities into their microprocessors than they ever could before—gigabytes of RAM instead of kilobytes, with clock speeds in the GHz range. The PCs themselves are more rugged and versatile.
We are an OEM that incorporates PLC, CNC, PC and robotics into turnkey automation systems, ranging from process controls to multi-axis coordinated motion applications. We have systems operating all around the world, and have been providing automation solutions for more than 28 years. In the past, we would have used PCs to run the user interface applications, while a PLC or CNC ran the machine control. Now, with a multicore PC, we can run all of these applications on one piece of hardware that sits inside an environmentally controlled enclosure, and have an inexpensive monitor exposed to shop-floor conditions.
In one application, we developed a filtration fabrication system that has an overhead gantry to pick up and position large cylindrical filters (up to 20 in. diameter, 10 ft long). Inside the welding cell, a robot picks up end rings for the filter from a part-indexing conveyor. The robot uses a pneumatic gripper to pick up the rings and place them into the weld fixturing, and then the gantry places the filter into the ring and clamping jaws are actuated to hold the filter in place. The robot then changes to a welding torch tool and welds the end ring to the filter. The fixtures are opened and the gantry flips the filter so that the other end ring can be welded on. Once the second end ring is completed, the gantry moves the finished part to the unload station.
This entire process is controlled and monitored by an embedded PC. The embedded PC monitors all the various sensors and analog feedback devices, controls six axes of motion using EtherCat communications, triggers robot program executions, controls the welding process over DeviceNet, controls an induction heating system and all pneumatic operations, and runs the custom Microsoft Visual Studio user interface application. We use the Beckhoff CX1010 with a 500 MHz Pentium processor for this application and many of our other machines.
Other applications have benefited greatly from multicore processors. This is particularly true for image processing. We used a TDI line-scan camera that dimensionally measured gaps in a product 40 ft long. These gaps measured 0.004-0.100 in. wide, there could be up to 11,000 measurements per scan, and the total scan was done in motion at 3 in./s. We had a resolution of 1 µm with this camera system and, as you could imagine, a lot of processing power was required from the PC.
Our first system was built with a P4 processor (top of the line at the time), and we had to scan and save the image data to memory. After the scan was complete, we would analyze the image data and calculate the measurements. During measurement processing, we had to shut down communications between our user interface software and the CNC so that all of the processing power could be used for the analysis. This process could take 5 minutes to complete.
Our current machine uses Intel's Core 2 Quad processor, and we can perform real-time measurement analysis and maintain full machine functionality—meaning that we can scan an image then generate a measurement before the next image is acquired. The increased processing capacity allowed us to take advantage of threading in our Microsoft Visual C# application. We have multiple threads for image gathering, image processing and CNC communication. With multicore PCs, we have taken a 7.5 minute process to 2.5 minutes.
We basically replaced all PLC control with the PC, and are designing new systems with Beckhoff PCs and Delta Tau CNCs (whose new CNC, the Power PMAC, is actually a PC). For us, PC control makes sense for all our process control and motion control applications.
John Martin is a senior project manager at Houston-based Arc Specialties (www.arcspecialties.com), which specializes in turnkey automation systems with integrated robotics.