What once was a war between makers of PLCs, PACs and industrial PCs over what was the best choice for controlling automated systems has instead become something of a love fest. Each of these approaches to industrial control has copied many of the capabilities of the others, to the point where many experts now say it doesn’t really matter which platform you choose because all will let you get the job done.
“The control hardware platform chosen, whether PLC, PAC or PC, is much less important than the methodology used to develop the software the system will use,” says Dan Perrier, president of Automated Control Systems (ACSI) (Automated Control Systems, Inc., http://www.automation-software.com), a control system integrator in Vancouver, Wash.
“During the infancy of PC-based control, almost all of the suppliers tried to define it as running your control logic on a Windows platform. This was a marketing solution in search of a problem,” Perrier says. “To me, PC-based control always meant PC hardware, not desktop PC software; [it meant] Intel (now including FPGA and ARM) chips, not Microsoft.”
According to Perrier, the key drivers of change today in the world of controls are safety (he includes continuous operation in this category), speed, cost and flexibility (another name for continuous improvement). These four factors are all positively impacted by the technical improvements and economies of scale of the hardware platforms.
“While any full-featured, monolithic user operating system may improve flexibility, it will always be detrimental to the first three factors,” Perrier says. “When choosing a hardware platform, you also have to take into account how rapidly changing hardware could hurt rather than help you. PLC systems have lifecycles that are measured in decades, so you always have to keep an eye open for migration paths to protect your investment.”
Perrier emphasizes the importance of using modular hardware platforms to support a wide range of situational requirements. “This allows you to match the processing, power usage, interconnect and space requirements to the situation at hand. SoftPLC (SoftPLC Corporation, http://www.softplc.com) does the best job of this,” he says, “since it doesn’t require the hardware to fit into a proprietary rack, and can take advantage of dozens of suppliers that offer hundreds of products.”
The power to do more
The number of capabilities that are built into a programmable automation controller (PAC) beyond I/O control and communications are what sets them apart from traditional programmable logic controllers (PLCs), says Cindy Hollenbeck, vice president of marketing for SoftPLC Corp. These functions typically include data logging, text messaging and database connectivity, as well as operator interface in many cases.
Hollenbeck says industrial PCs lack the robustness and rugged architecture of both PACs and PLCs, so they’re primarily used in non-critical applications that won’t bring the plant down if they fail. And while vendors keep adding new capabilities to their PAC platforms, “there will continue to be a big market for brick PLCs that provide simple, discrete control with low I/O counts,” she adds. The longer hardware life of PACs (five to 10 years) and PLCs (10-plus years or more) vs. two to three years for PCs is also an important factor when considering a control platform.
So who’s buying PACs and why? The most obvious reason, says Hollenbeck, is that “companies want to know more about what’s happening in their machines and on their production lines. People want more data, the ability to mix and match I/O from multiple vendors and simplified data logging.” For improved communication through-put, the built-in router in a SoftPLC sends Ethernet I/O and data communications on different subnets. Multiple built-in data transmission ports also minimize the risk of traffic backups and system failures.
A distinct advantage that PACs have over both PLCs and PCs, says Hollenbeck, is that they can be programmed with custom code blocks. “This is especially important for OEMs and system integrators, who risk having their work hacked when they ship machines to India, China and other countries without strong intellectual property protections. The open architecture of SoftPLCs allows machine and system builders to better protect the unique functionality of their equipment. While anything can be hacked, custom code makes it harder to do.”
Size is also important, which is another area where PACs excel. “The trend is to smaller control cabinets because floor space is so expensive,” explains Hollenbeck. “With so many built-in functions, it takes fewer components for a PAC to provide the same capabilities as it would with a PLC.”
Another strong point for PACs is the trend among customers to allow OEMs to have remote access for servicing equipment. “Service has become a bigger part of an OEM’s income stream, because no one wants to pay for travel and the time delay it causes in getting a machine or production line up again,” Hollenbeck says. “PACs also allow OEMs to keep track of a customer’s production, provide performance reports and issue preventive maintenance alerts.”
Design for connectivity
One of the most important technological improvements driving the consolidation of control hardware is the introduction of multi-core processors. “It’s not uncommon to find processors with two, four or even eight cores,” says Connie Chick, senior product manager for PLC products for GE Intelligent Platforms (GE Intelligent Platforms, http://www.ge-ip.com). “This enables greater processing power and the ability to run multiple applications on one processor for greater productivity, faster data acquisition and analytics.”
In selecting the right control platform for your application, says Chick, the first thing to consider is connectivity. “You’re going to be connected to other systems, so what is it your equipment needs to do and where does it need to interact with other systems at the edge mode. Among the questions you need to ask: What do you need to run the operation efficiently, what data do you need to share and at what point in the process, and how can you make that information easier for people to see and use?”
A crucial point for original equipment manufacturers (OEMs), which often make only part of a production system, is to consider how their equipment needs to work with those of other vendors throughout the entire system, according to Chick. This involves numerous factors like how to ship the equipment, how it will be installed, and how it needs to connect to other vendors’ equipment.
Chick says PACs are being more widely used today because they can handle a wider range of applications than a traditional PLC. Another trend is to put the control system inside other equipment, such as an HMI display with controls inside. “You have to ask, do I really need that other box or can I get one box to do everything so I can reduce costs, maintenance and wiring connections?”
Chick adds, “In the future, it’s going to be hard to tell whether the control hardware is a PC or a PLC. It’s going to be one box with the ability to do multiple things. OEMs will even have boxes that won’t be defined until the equipment gets installed and connected by the customer. The box will be able to handle whatever the user needs it to do at any given time, which will provide multiple backup capabilities as well as lots of flexibility and maintenance options.”
This new world of control will require everyone in the automation industry to step up his or her game when it comes to programming software. “You’re no longer going to be dependent on ladder logic,” says Chick. “People need to change their approach to creating software, using higher-level languages, mastering tools like MATLAB to create C/C++ code that you can download, working with different graphical interfaces, debugging code and using simulation tools. Vendors are working to develop better tools. When they do, we’ll see big changes in the industry.”
Making the transition
When is it time to consider stepping up from a PLC to either a PAC or PC-based control? Brian Phillippi, product marketing manager for National Instruments (NI) (National Instruments, http://www.ni.com), says there are a number of indicators, including whether your application requires data processing or control beyond simple PID loops, high-speed operation, advanced or model-based control, a custom board or communication protocol, vision or complex motion, including multiple axes.
“The adoption of advanced control technologies is particularly fast in applications that need smart machines to handle high-speed data processing and analysis, condition monitoring, have self-healing capabilities or make adjustments on the fly for new parts or products,” Phillippi says.
One of the major factors driving the development of PAC- and PC-based control is the huge amount of data being generated by machines in today’s production systems. “To easily integrate the data from various parts of the production process for faster and better decision-making, machines need to speak the same language and use the same data format,” says Phillippi. “That works best when you can use a single platform, which lets you simplify control hardware. It also allows engineers to distribute processing nodes across an application, at lower levels on a machine, to simplify programming requirements.”
Phillippi points to several examples of OEMs that transitioned from PLCs to either PAC- or PC-based control systems to improve machine performance.
Integrated Industrial Systems (I2S) (Tenova I2S, http://www.tenovagroup.com/companies_i2s.php?id_company=12), Wallingford, Conn., was able to add custom measurement and analysis to its gamma-based sensors without compromising control rate speed by using an off-the shelf NI CompactRIO PAC. By updating its old PLC architecture, I2S ensured faster and more accurate measurement of material thickness, increasing the production and quality of steel rolling mills.
Another customer, Master Machinery (Master Machinery, LLC, http://www.mastermachineryllc.com), Warren, Mich., combined NI’s CompactRIO hardware with Kollmorgen (Kollmorgen, http://www.kollmorgen.com/en-us/home) EtherCAT drives and LabView software to increase the throughput in its semiconductor pick-and-place machines. Equally important, the new control architecture has the flexibility to more rapidly evolve future machine designs.
Pavac Industries (Pavac Industries, Inc., http://www.pavac.com) in Richmond, B.C., Canada, turned to PC-based control to create a system for its electron-beam welding machines that’s highly scalable, expandable and easy to maintain. By using NI’s PXI hardware and its Lab-View FPGA and Softmotion modules to replace traditional PLCs, Pavac was able to integrate multi-access motion control for time-critical synchronization and signal generation.
Evolution of industrial PCs
Many PACs still depend on accumulating separate hardware modules to add functionality. A more efficient alternative, says Aurelio Banda, vice president of sales and marketing for Beckhoff Automation (Beckhoff, http://www.beckhoff.com), is the use of industrial PCs and embedded controllers with the latest in multi-core processing technologies.
“This centralized control hardware, when paired with software, can bundle full control functionality such as PLC, motion control, robotics, HMI and more,” he says. “It’s typically possible to manage all machine tasks (or multiple machines, plus robot equipment) on one piece of mechanically robust PC-based hardware with compact distributed I/O to make field connections.”
Banda cites one example, an ultra-sonic cleaning and sterilization system for hospital medical equipment that uses a Beckhoff embedded PC running TwinCAT automation software. Because patient safety is at stake, absolute reliability is critical. The UltraZonic system, developed by Z-Products (Z Products, Inc., http://www.zproductsinc.com) of Belgium, modulates the ultrasound frequency to adjust the cleaning strength to match the requirements of the items being processed, even sensitive surgical instruments. The cleaning sweeps are so efficient that even bacteria are killed.
Just as PACs represent an evolutionary step from the PLC and PC, so too are PCs evolving. “It’s no longer clear what a PC-based controller is,” says Karl Rapp, manager of application engineering, automotive and machine tools for Z.
“Vendors are supplying industrial-grade PC-based motherboards in small form factors. This approach reduces the frequent obsolescence problems that OEMs and end users have struggled with when using PC-based hardware,” says Rapp. Bosch Rexroth (Bosch Rexroth, http://www.boschrexroth.com/en/xc), for example, uses a common hardware platform for CNC, PLC and motion logic control systems. This scalable platform includes multi-core CPUs and various connectivity options for motion, I/O and factory networking.
“Embedded PCs now offer a good platform to achieve the 10+ year product lifecycle expected for automation equipment,” Rapp says.
The increasing use of mobile devices in the factory, such as smartphones, tablets and smart watches, will bring further changes for automation, allowing what were once considered consumer devices to integrate with factory systems to provide applications such as HMI, communications and machine/process control. “This will further blur the line between what is PC-based control and what is not,” Rapp adds.