Motors for everything from pumps to fans consume nearly two-thirds of America's electricity, so any push for energy conservation would do well to begin here. Many home appliance makers have taken up the banner and have already switched to permanent magnet synchronous motors to improve efficiency.

A technique called sensorless field-oriented control promises to make these motors more efficient. According to Microchip Technology Inc. of Chandler, Ariz., the technique can also reduce system costs and simplify manufacturing.

Powerful algorithms in this digital processing controller can aid permanent magnet synchronous motor efficiency without sensors.

The key is an integrated circuit called a digital signal controller. Like a more expensive microcontroller, it is easy to program. And, like a digital signal processor, it solves complex mathematics with blinding speed. Unlike either, digital signal controllers come with embedded peripherals that make them one-chip solutions for controlling motors.

Microchip's dsPIC digital signal controllers are fast. They do the multiplication and accumulation steps found in every controller or filter four to five times faster than in the past. This gives it more time to implement field-oriented control.

According to Jorge Zambada, applications engineer at Microchip, "This is a technique that uses a series of transformations to convert the phases of a three-phase motor into two phases, one related to torque and the other related to flux. You can implement very simple control loops that let you control torque and flux directly, so your motor runs more efficiently."

The algorithm is so accurate that designers can eliminate sensors and control the motor just by measuring current and voltage, Microchip claims.

"Sensorless control is not so good at very low speeds, but for motors used in air conditioners, washing machines, and refrigerator compressors, you don't need such accuracy at low speeds," Zambada said. "This works fine for motors operating between 10 and 100 percent of their speed range."

In the past, sensorless field-oriented control was limited to ac induction motors. Microchip's latest dsPIC chips work with permanent magnet synchronous motors.

According to Zambada, the chip is flexible so companies can use it for a wide range of motors. Since the control loops are simple, engineers can fine-tune controllers and power electronics modules for each new application, "The internal flash memory is the only thing you have to change. It really reduces time to market," Zambada said.

According to Microchip, then, the system makes both motors and those who build them more efficient.

The new family of MotiFlex e100 three-phase ac motor drives from Baldor Electric Co. in Fort Smith, Ark., combines Ethernet networking and Internet connectivity with an energy-saving shared bus that simplifies system builds. The first MotiFlex drives reach up to 16 amps output power in five steps (1.5, 3, 6, 10.5, and 16 amps). More powerful systems are due later this year.

Connectivity makes the drives especially interesting. Ethernet connectivity has intrigued manufacturers because of its low cost (due to high volume) and easy connectivity to corporate networks. Yet Ethernet had one significant drawback: It is not deterministic. That is, it does not execute commands in real time.

Since 2003, Baldor and hundreds of other industrial companies have embraced PowerLink Ethernet, an open standard that includes a separate domain for real-time commands. Baldor's motion control product manager, John Mazurkiewicz, explained the difference: "If a worker crosses a light screen and a machine has to shut down immediately, PowerLink does it immediately. Traditional Ethernet does it when it gets around to it."

New electric motor drives combine a shared bus with deterministic Ethernet connectivity.

Ethernet lets users daisy-chain drives into centralized and distributed intelligent drive systems. It reduces the amount of electrical power components and cabling needed to build large multiaxis systems. A single Baldor Ethernet controller, for example, manages up to 16 interpolated axes.

The system's built-in Internet connectivity simplifies networking several plants in different locations, or communicating with distant corporate systems.

According to Mazurkiewicz, MotiFlex's shared bus is especially helpful when building systems that have three or more coordinated motors or axes. The system uses a single power supply, and each drive's ac-dc converter can supply power not only to itself, but also to one or more drives of the same total rating. Baldor says the highest rated drive alone is often enough to power a complete multiaxis system.

The approach simplifies the entire electrical system. A single set of components replaces multiple contactors, fuses, circuit breakers, terminal blocks, and electromagnetic compatibility filters.

MotiFlex drives operate independently or as part of a shared dc bus system that reuses power regenerated from axes deceleration in other axes. It stores any additional energy in each drive's local capacitor bank. The combination of energy reuse and capacitive storage often keeps total capacitance low enough to eliminate the need for an external braking resistor.

Somebody will undoubtedly contest the title of "world's fastest robot" claimed by Adept Technology Inc. of Livermore, Calif., for its new Quattro s650. Yet there is no doubt that the Quattro s650 is very fast. It can accelerate a 2-kilogram load up to 20 g over a work area 1.3 meters across and 250 mm deep with virtually no settling time.

To understand how the inverted parallel robot moves so fast without shaking itself apart, consider a chair. A three-legged chair is stable enough to sit on, but a four-legged chair stands up better, especially if you tilt or wiggle it.

The same is true of inverted robots, whose arms drop down from above the work area to control a single gripper attachment. According to Seema Gupta, Adept's product marketing manager, conventional inverted robots have three parallel arms (with an occasional fourth arm to rotate the workpiece). The Quattro s650 has four descending arms.

"Three-armed robots sometimes have problems moving away from the center of the work envelope," Gupta said. "They have trouble balancing the load, especially at high speeds.

"The whole motion control idea behind four arms is to use opposing arms to counterbalance each other. When I'm moving in one direction, our kinematics algorithms recognize and compensate for what's happening with other arms. The result is better load handling, higher acceleration, and a very good balance of torque and motion," Gupta said.

The arms themselves are made of carbon-fiber reinforced composites. The stiffness and light weight reduce the momentum of the arm at very high speeds.

Adept integrates its vision guidance software with the Quattro s650. Cameras capture pictures of objects coming down a moving belt and send them to the controller. It compares the pictures with a template, decides whether they match, and then communicates the position of the object to the robot. The system is fast enough to rapidly stack parts that are all the same (doughnuts placed in a carton) or assemble different types of objects (such as cosmetics jars) into a kit.

The Quattro s650 combines smart servos and power amplifiers into the body of the robot. This eliminates cabling and simplifies installation. The robot itself has a light enough touch to pack even fragile pastries and candies at high speeds.

"You just want to make sure it doesn't move so fast the wrappers go flying off during packing," laughed Gupta.

Options for carrying large assemblies—structures weighing 100 tons or more—through a plant often involve cranes and rail systems. If there is space enough, a factory can use one of the multiaxle hauling platforms designed for carrying very heavy loads over the road.

The Wilkes-Barre, Pa., plant of Air Products & Chemicals didn't have that kind of space. It had a rail system in place, but wanted to move subassemblies through places where the rails didn't go. So it wound up opting for something a little different.

Among its products and services, Air Products supplies gas generation equipment with capacities ranging from a few cubic meters per hour up to many hundreds of metric tons per day. Some of those systems get very big indeed.

To move some of the subassemblies around its plant, the company bought two Wheelift multiaxle transporters, each capable of carrying 110 tons. Ac- cording to Steve Swartwood, manufacturing engineer for the company, the units met the factory's space and height requirements. "They get under the loads we carry," Swartwood said. The plant uses a rail system to move equipment through the final stages of assembly, but Swartwood said, "We were limited by how much rail we had." The Wheelift transporters carry subassemblies on their way to the final stage.

Transporters for moving heavy loads through a factory need 18 inches of clearance and can carry 25 tons per axle.

The transporters come from Wheelift Systems, a unit of Doerfer Cos., in Waverly, Iowa. According to Mel Terry, a systems application design specialist at Wheelift, there is almost no limit to the capacity of the transporters. They are equipped with four or more axles, each rated to bear up to 25 tons. He said there is no limit to how many axles can be built into a transporter, or how many transporters can be combined to carry a load.

Platforms are designed to move under structures that allow for 18 inches of clearance. Hydraulics lift the platform to raise the load. The vehicles can move in any direction, usually at the pace of a slow walk, or perhaps 80 to 100 feet per minute, Terry said. The transporters can be directed to move forward, backward, to the side, or around their own center axis. Terry added that versions can be designed with even lower vertical clearances.

Regardless of the number of axles under the vehicle, the hydraulics are linked to create three systems for three-point lift. The hydraulics serve as the suspension system for the wheels, which have wide tires made of solid urethane. This arrangement allows the transporter to keep the weight distributed evenly among the wheels as they roll over the inevitable irregularities of a plant floor.

According to Terry, the transporters are made practical by an onboard computer that calculates the geometry of the multiple axles, a system that the company calls SynchroSteer. The vehicles can be directed by an operator on board or nearby. They can be programmed to move autonomously with an inertial guidance system. A laser system can detect obstacles—say, a forklift parked in an unexpected place, or a wandering pedestrian—Terry said.

The transporters in the Air Products plant are steered by an operator, Swartwood said.

The transporters are driven by electric motors. Propane engines drive generators for electric power.

Wheelift doesn't recommend them for all situations. A 150-ton transporter, with six axles, could cost $250,000 or more. Terry said, "They can only be cost-justified in applications where conventional means cannot provide the functionality needed."

The company's Web site includes a video of the transporters at work. It is at Wheelift.com.

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© 2007 by The American Society of Mechanical Engineers