Wireless Keeps Machines Coordinated
Wireless integration of control systems has been around for a long, long time. Wireless remote control of aircraft and marine vessels—essentially the technology used by RC (radio controlled) modelers today—was developed before World War II. Because the barriers to entry have been lowered so dramatically, wireless control has become competitive with wired control for most applications. A sampling of applications illustrate how developers have solved problems by sending signals through the luminiferous ether, instead of metal wires.
|For MSI’s crane scales, basic networks wirelessly forward data gathered from instruments to digital indicators.|
Wireless weighs in
Seattle-based Measurement Systems International has a rich, 30-year history of innovative technical breakthroughs in industrial weighing and process control systems. MSI is especially known for systems built around its crane scales, which can accurately weigh objects weighing up to 250 tons. The only practical way to weigh a multi-ton load is by lifting it with a properly instrumented crane.
For obvious safety reasons, crane scales always display their weight readings remotely. MSI has relied for years on Cirronet industrial radio modules to provide the wireless link.
The most sophisticated MSI network in operation to date is at a major U.S. aluminum plant. Electric furnace pots, typically 20 to 30 in a line and each about 500 feet long, burn the oxide off bauxite to produce pure aluminum.
Vacuums remove the pure aluminum from the pots and deposit it in crucibles, which are moved around by cranes. A typical operation consists of removing several hundred pounds of aluminum from a pot and delivering it to a mold. Crane scales make it possible to extract just enough aluminum to keep each pot line running efficiently and balance aluminum production with demand.
This particular U.S. aluminum plant fully leverages MSI’s wireless capabilities The plant features a master modem in each pot room, with a Yagi RF antenna providing good signal strength throughout the pot room. A Cirronet CellModem with dual independent ports sends data to a scoreboard, an RFID reader, and RF tags embedded in walls, pots lines, and crucibles.
In this environment, a human operator with a handheld controller can walk the plant, directing each crucible to a specific pot to extract a specific amount of aluminum. The operator is relaying information from the plant’s mainframe regarding quantities needed for specific orders, linking the crane scale to the corporate information system and central databases.
Dust Networks’ network-ready SmartMesh products, based on the company’s time synchronized mesh protocol (TSMP), will provide low-power wireless sensor networking systems for Streetline’s parking management solutions. The systems provide, according to Dust, highly reliable, low-power wireless connectivity to previously inaccessible information.
Recent Streetline parking management deployments include a pilot with the City of Los Angeles designed to support the city’s on-street parking operation with real-time information about meter operation and parking space usage. Based on reliable ultra-low-power networks, environmental sensors and machine interface technology, Streetline’s City Infrastructure Technologies platform (CiT) is designed specifically to support city management. Streetline’s parking management system, featuring Meter Monitors and Vehicle Sensors, is part of the CiT platform.
Streetline Meter Monitors provide two-way networking to standard single space parking meters, with no wiring and no modification to the meter housings. The patented technology is compatible with over 90% of installed meters, and in most cases plugs into existing meter data ports. The monitors help cities track usage and vandalism, and provide a detailed audit of all meter operations in real-time.
Streetline Vehicle Sensors deliver accurate real-time information about arrivals, departures and occupancy in on- street parking spaces. The rugged and reliable sensors are available in an easily deployed surface mount version, as well as a pavement-embedded version for snow areas.
In combination, the Meter Monitors and Vehicle Sensors give operators a complete picture of on-street parking operations, as well as a foundation for effective enforcement, maintenance, pricing, and other policy decisions.
|CiT integrates sensor data acquired wirelessly forward data gathered from instruments to digital indicators.|
Wireless for life
Just as in a factory, owners of health clubs are concerned with machine uptime and usage data.
“Our biggest customers tell us that their number-one challenge today is ensuring that the mileage on equipment is uniformly spread,” says Raj Rao, general manager of connectivity for Life Fitness, maker of more than 300 cardio strength training machines.
“If you have several treadmills on a floor, you’d be surprised how different the usage is of each machine over its life cycle. So you could end up replacing a treadmill earlier than you would have done if you had just switched a heavily used unit with one with less mileage.
Club owners don’t know when to rotate the treadmills because they don’t know the mileage on them to start with, says Rao. Then, just to move a treadmill three feet to the left to improve its utilization, the staff has to rewire the network, or possibly even take it down for a day or two.
Life Fitness investigated a number of wireless options and selected the proprietary battery-powered, mesh-networking technology provided by Crossbow Technology. Life Fitness favored the Crossbow solution because of how it addresses power issues, and because of Crossbow’s reputation for excellent customer support.
Each node transmits data to the gateway and acts as a repeater for other nodes. The mesh network has built-in intelligence, reconfiguring itself whenever equipment is moved. Gym operators can serve members better and run their businesses more efficiently.
Crossbow technology also gives gym operators over-the-air programming capability. Any node can be reprogrammed remotely from anywhere; all that’s needed to do the reprogramming is an Internet connection. This wireless sensor networking approach reduces cost, shortens the time it takes to set up and provision the network, and makes it easy for gym operators to implement upgrades.
|C.G. Masi is senior editor for discrete manufacturing and machine control. Reach him at firstname.lastname@example.org .|