Cutting ties with the past: Wireless motion feedback

July 1, 2012
Wireless functionality is everywhere, including motion designs. Some discrete-product applications usethese connections to transmit data where cabling is prohibitively expensive or complicated.

Wireless connectivity offers cost effective turnkey networking, and the ability to integrate feedback from inaccessible motion designs. Like all networking, it’s been influenced by commercial innovation.

“Wireless connectivity is proliferating in industrial, commercial, and consumer applications because it offers a convenient way to connect and control machinery,” explains Erling Simensen of Texas Instruments Inc., Dallas.

A key driver is the Internet of Things, in which systems are connected to the Internet for live monitoring and control. Often, wireless sensors are involved; command transmission is still in its infancy, though growing. “There’s increasing demand for wireless control — particularly for very large installations,” says Jacob Stock, Director of Business Development at GCI, Garfield, Minn.

Power consumption

Minimizing power consumption is key to wireless-functionality success. “With our ultra-low power MSP430 MCU controller, battery-operated wireless sensor nodes can operate longer to gather more data,” says Simensen.

Other designs take a different tack. Some of the first industrial wireless devices were for predictive maintenance — in the form of handheld vibration probes with HMI functionality. Therefore, it’s natural that new innovation should come from this arena. Consider Perpetuum Ltd., Austin, a company that manufactures electromagnetic vibration energy harvesters incorporated into wireless probes. With their design, a passive magnetic structure is attached to an oscillating mass so that it traverses a magnetic field established by a stationary magnet. A coil collects induced ac voltage according to Faraday’s law — for voltage regulated to storage or usage. Applications include monitoring bearings, braking systems, and motors.

“Alternate power sources are an important complementary technology for industrial wireless products and the Perpetuum solution demonstrates the value of these combined technologies,” says Andre Ristaino, managing director of the International Society of Automation ISA100 Wireless Compliance Institute.

Another source of wireless motion innovation: Military

Mike Donfrancesco of InterSense Inc., Billerica, Mass., explains his company’s core technology: “We focus most of our engineering efforts on motion tracking — realtime motion measurements of human operators or machinery. Often used in military simulation applications, our inertial sensors — gyrometers and accelerometers — track position and orientation.”

Now, in a design project led by manufacturer GCI, these functions and wireless capabilities are improving an assembly application as well. GCI focuses on material handling and custom manufacturing. Their recent solution is used by one jet-engine manufacturer for digital verification of manual assembly processes. In short, installation verification (usually through a master checklist) is executed with wireless communications from specially equipped torque wrenches used to install the design’s myriad fasteners.

“A tracking device verifies wrench location, and torque sensors verify that each bolt is torqued to the right value, in a given sequence, at a specific time,” says Donfrancesco. Information is fed wirelessly through a 2.4 GHz or 900-MHz network to a CPU keeping a master log of every bolt fastened.

Meeting standards, avoiding errors

A final challenge is ensuring adherence to standards and error avoidance. “In industrial settings, there’s interference and saturation to address, even when technologies appropriate for an application exist,” says Stock. “The challenge for an integrator — and from an application standpoint — is to know and trust that a wireless subcomponent is going to work. In one recent design requiring wireless functionality, we encountered challenges in securing hardware with a licensed frequency. These chips can be large, and hardware dedicated to an exact range can be limited. Eventually, we found a design, originally used in crane applications.” Suppliers work to address these issues.

For the TI controller mentioned, an RF module is mounted on TI’s BoosterPack or bought separately when manufacturers are ready to take a design into production. “Designing with a module incorporating RF transceiver, passives, and antenna saves manufacturers money when applying for regulatory approval, as the modules are pre-certified FCC/IC and ETSI compliant, and minimize the chance of a noncompliant RF,” says Simensen.

Another design to boost reliability is the SwiftComm quadrature incremental encoder interface. From BEI Sensors, Goleta, Calif., it provides wireless signals in realtime over a secure network. Point-to-point configuration allows data relay between transmitter and receiver every 600 μsec with no inherent latency; the signaling unit uses adaptive frequency hopping to avoid data interruptions due to interference. When a verified packet of information is received, the unit determines any accumulated error and sends corrections to the controller.

For more information on CANblue II/Generic, visit

About the Author

Elisabeth Eitel

Elisabeth Eitel was a Senior Editor at Machine Design magazine until 2014. She has a B.S. in Mechanical Engineering from Fenn College at Cleveland State University.

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