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Smarter Sensors, Fewer Wires

Improved sensing technologies and wireless networking strategies are helping manufacturers make better decisions, as well as save time and money.

This sensor from Balluff receives power as well as sends data through an air gap. Source: Balluff
This sensor from Balluff receives power as well as sends data through an air gap. Source: Balluff

Advances in photoelectric sensors using improved fiber optic cables have allowed manufacturers to add many more sensors in smaller areas, in order to provide much more usable information to the process controllers. One example of this occurs at Laser Die & Engineering, based in Kentwood, Mich.,an original equipment manufacturer (OEM) that builds a wide variety of custom assembly tooling equipment—from stand-alone workstations to fully automated production lines. An ongoing project at Laser Die & Engineering involves building tooling that assembles headliners—the interior ceilings of automobiles.

Each trim level within an automobile model requires a unique headliner. Laser Die & Engineering uses fiber optic sensors for specific inspection tasks. One particular application, employing 20 fiber optic sensors, verifies that holes through the headliner are correctly located. A second application uses as many as 30 additional sensors to confirm the presence of hardware to be attached to the headliner. But while these sensor applications get the job done, they also presented a design challenge for Laser Die & Engineering. “Running power to each fiber optic amplifier created a wiring mess,” Controls Manager Harry Rissley explains. “Additionally, the amplifiers were overly complicated and difficult to program.”

To increase productivity, Rissley began using a multi-channel fiber optic controller from ifm efector, a sensor manufacturer with U.S. headquarters in Exton, Pa. Designed for multiple sensing point applications, the fiber optic controller reduces excessive wiring for multi-fiber applications with a single cable. The liquid crystal display (LCD) operator interface is used to program fibers with the controller’s pushbutton programming and user menu.

On sensor programming

Laser Die & Engineering also takes advantage of the logic functions available on the fiber optic controller. By programming an “AND” function for the hole verification task, the company is able to reduce each group of eight signals to a single output, greatly reducing the input/output (I/O) points required for the workstation.

Rissley sums it up: “Installation time for our fiber optic controls has decreased by 40 percent and our material cost per fiber has dropped by more than 20 percent.”

Sometimes the area that needs to be sensed is in a location that is impossible to hard wire. That requirement is problematic enough, but what if even getting electrical power to the sensor is somewhere between difficult and impossible? Such is the case with rotary index machines, some welding machines and also on heavy equipment. Moving data through “thin air” is a well-known phenomenon. But is it possible to provide power to a sensor across an air gap?

Tad Hatakeyama, product manager at Florence, Ky., sensor supplier Balluff Inc., explains that a “sender” can be hard wired to a power source and the programmable logic controller (PLC) and located on a stationary surface. As the sensor moves past it, the sensor receives power, checks its condition and reports data back through air to the sender. The sender, in turn, reports back to the PLC.

“Another application our customers have reported is in progressive stamping press dies,” says Hatakeyama. A progressive die set up is when there are two or more dies in the same punch press. Material is fed into the first die, the machine stamps the part, then the part is fed to the next die for further operations. “The sending unit could be installed in the first die to sense ‘part present,’ with the remote sensor installed in the second die,” continues Hatakeyama. “Because dies are heavy and dangerous to wire, it makes sense from both a safety and an easier set-up time perspective to use sensors that do not require wires.”

Sensor research

While individual companies continue to innovate and bring new products to the market, other organizations are sponsoring research into technology advancements and better ways to use sensors. The National Center for Manufacturing Sciences (NCMS), in Ann Arbor, Mich., is leading many projects in various facets of manufacturing engineering. The Center’s stated mission is to lead the rapid development of cross-industry research and development programs to build the global competitiveness of its manufacturing industry partners.

Jim Dallum, product development manager at Cincinnati Lamb, describes a joint industry/government/academia collaboration called the Smart Machine Project that is exploring ways to retrofit machinery with modern sensors, and then collect data on machine performance and health. The Cincinnati-based machine tool manufacturer is participating in a pilot project with its Freedom e-Log system that relies on a dedicated network to gather process and machine health data into a time-stamped database, with results presented via a Web browser interface.

The pilot project involves the Red River Army Depot (RRAD), in Texarkana, Texas. It is the only remaining organic depot that can process rubber for tank treads. Given the wars in Iraq and Afghanistan, its workload has increased dramatically, but its processing equipment is outdated. This project aims to increase the quality and efficiency of the rubber processing equipment at RRAD by retrofitting it with modern sensors and data collection on machine performance and health. Cincinnati Lamb will install systems at RRAD and at Caterpillar, the Peoria, Ill.-based heavy equipment maker, which is also participating in the project. The systems will be exercised for about two months, gathering data on machine cycle times, down time, machine utilization, and health and diagnostics data such as temperatures, pressures and so forth.

Dallum adds, “We have been chasing the fertile ground of smarter machine technology with NIST and NCMS over the last couple of years. Many people think it would be a competitive advantage, leading to fewer reasons for offshoring manufacturing as machines become more autonomous.”

The challenge with traditional computer numeric controlled (CNC) machines, according to Dallum, is gaining access to the data that is already there, then adding on more sensors. Dallum believes that the biggest bang for buck can come from exploiting Web technologies with more plug-and-play components. “We need a quicker, faster implementation,” he says. “We need to open up the data, giving a team of people the same data picture. In a shop that runs 24/7, first shift people don’t always know what happened in previous shifts. They may just get filtered information from the person before them.”

So just what constitutes a “smart sensor?” Reno Suffi, sensing products product manager at Omron Electronics, a supplier of automation products with North American headquarters in Schaumburg, Ill., says, “Much of the definition involves the types of information they can provide. For example, some day we may have a proximity sensor, something that senses without contacting the target, that knows when it impacts something. That could send a signal to maintenance asking for re-alignment.”

“Many sensors today understand when their performance has degraded and can make internal compensation,” Suffi observes. “Some sensors can have built-in algorithms for process control—for example, a vision sensor that sees how the product coming down the line is getting wider and causes the guide rails to change.”

Sensors usually report their status to a PLC. It is the PLC’s job to control the process. But with smart sensors, that need not always be the case, Suffi notes. “Say you have an oven with a bunch of heating elements. These elements could have a temperature sensor with built-in control algorithms that each would know when to turn on or off in order to keep an even temperature in the oven,” he says. A smart function block in the sensor could then just interact with a touchscreen operator interface, and perhaps a PLC could be eliminated, saving the company some expense, Suffi explains. “There are so many uses for intelligent sensing that your imagination is the limit.”

GO wireless

Today, almost all sensors have a wire that connects each one to a controller. But there are many applications for which the expense in labor and material is too great to justify adding sensors and associated wiring to a process—even when the information they provide could be valuable to a manufacturing software application.

One potential solution for these applications involves a new wireless network standard that is gaining traction, and is low cost and easy to install. Based on the IEEE 815.4 standard of the Institute of Electrical and Electronic Engineers, ZigBee is a “mesh” and “self-healing” network. New devices added into the wireless area find the network and add themselves to it. Other devices find it as well and start using it if needed.

One early supplier of ZigBee chips, protocol stacks and development tools is Boston-based Ember Corp. Venkat Bahl, Ember vice president of marketing for device and ZigBee lines, is also a board member of the ZigBee Alliance. “We’re a promoter of the ZigBee alliance,” states Bahl, “because it fosters interoperability of platforms so that end users don’t have to worry about getting stuck with some kind of niche proprietary product.”

Eaton Corp., in Milwaukee, is an Ember customer that develops wireless sensor networks for applications such as building automation. Jose Gutierrez is principal engineer and program manager for wireless communications at Eaton’s Corporate Research and Development Center. “We were co-founders of the IEEE standard for wireless mesh networking and also for the ZigBee Alliance,” states Gutierrez. “There were no standards for this technology at the time, and we wanted all the benefits of stability and collaboration that standards bring.”

A first commercial offering of this technology from Eaton is called the Home Heartbeat System. Described as a “home awareness” system, not precisely a security system, Home Heartbeat consists of a base station, removable key fob-style display and a variety of wireless sensors that detect open/closed doors, water flow, electric power and other conditions. “We are now working to expand this to building automation with two grants from the U.S. Department of Energy,” says Gutierrez. “Some research slated for the future is how to provide power to run the system and a three-dimensional location system for each sensor. What is available now is a low-cost, bi-directional wireless mesh network. As competition increases, we should see prices drop to where it is economical to apply. The trouble is that everyone wants wireless, but no one wants to pay extra for it.”

Gutierrez points to the future, “The winners among the components people are those who provide the complete package with development tool set, plug-ins and commissioning help. Wireless mesh networking is the next big revolution, but everyone still has the point-to-point networking attitude.”

For more information, search keyword “smart sensors” at www.automationworld.com.

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