Engineering News 7355

Fuzzy logic offers new ways
to solve tough control problems

Newton, MA--Maytag, General Motors, John Deere, Eaton Corp., and NASA. What do these U.S. enterprises have in common? They're all using fuzzy logic and aren't afraid to say so.

Maytag's IntelliSense(TM) dishwasher uses fuzzy logic to decide exactly how long to wash dishes, thus saving energy, water, and time. In GM Saturns with automatic transmissions, a fuzzy-logic controller mimics an expert's down-shifting skills. Engineers at Deere's Industrial Equipment Division are using fuzzy logic to make construction equipment easier to control, Eaton is working on fuzzy-logic sensors, and NASA is using the technology to control the next generation of a power wrench for use in space.

Lots of other companies are using fuzzy logic, some with great success. In fact, some analysts say that a leading color-printer company is using fuzzy logic, as well as almost every car company.

Fuzzy what? Fuzzy logic is based on fuzzy set theory, a mathematical discipline invented in the U.S. This theory allows for shades of gray between absolute truth and falseness, unlike bilevel logic, which holds that a statement must be 100% true or false. In fuzzy logic, a statement such as, "Julie is driving fast," can be 75% true and 25% false if Julie is cruising the highway at, say, 70 mph.

Fuzzy logic lets engineers control real-world systems by using language-based rules rather than rigorous mathematical modeling. It has proven especially effective for situations having complex equations, lots of exceptions to the equations, nonlinearities to accommodate, system inputs that provide vague or ambiguous information, or no equations at all.

A PID control system is an example of a traditional, linear approach. "With fuzzy logic," says Boyd Nichols, senior development engineer with John Deere, "instead of coming up with one equation for everything, designers write rules that tell the controller what they want it to do for every combination of error, derivative of error, and whatever other conditions they want to look at." Construction equipment encounters such nonlinear factors as soil condition and traction.

Deere looks to fuzzy-logic technology to make machines easier to manage. One example is a bulldozer making a level cut straight ahead. This is a job that requires years--even decades--of experience, says Nichols. A fuzzy control system makes use of knowledge of the experienced operator as well as sensor inputs from the machine to help the machine do a better job--even with a mediocre operator.

Reported fuzzy benefits include: accelerated R&D, reduced time to market, simpler solving of complex control problems, and the ability to get more horsepower out of a given processor. "Fuzzy logic has the potential to have the same impact on technology over the next two decades that the microprocessor had over the last two," forecasts fuzzy-logic consultant David Brubaker.

There are drawbacks. There is no formal method for designing fuzzy systems. In addition, the resulting system is not analytic, and you generally cannot prove a system's stability on paper. "But remember," notes Brubaker, "fuzzy logic was developed for complex systems for which designers could not create mathematical models or whose models were gross simplifications."

The field incorporates some comical-sounding terminology. Values are "fuzzy" or "crisp." Converting crisp values to fuzzy values is "fuzzifying." And computing a crisp output from fuzzy membership functions is deemed "defuzzification."

"Fuzzy logic is just a horrible name," says Rod Hemmerlein, fuzzy technologies product manager at Inform Software, Oak Brook, IL, which develops fuzzy-logic tools and conducts training. "It should have been called multivariate math or something like that. When I tell my friends what I do for a living, they kind of laugh at me."

Adds Nichols: "People have a bad response to the word 'fuzzy'--it doesn't seem worthy of an industrial machine and connotes imprecision."

Lack of understanding also keeps some designers from trying fuzzy logic. Will Schrieber, senior program manager at Intel's Embedded Microcontroller Division, resells Inform software products with embedded control tools for Intel chips. He says he's developed fuzzy-logic solutions for key accounts and handed it to them. "They evaluated it but because they didn't truly understand the technology, they didn't want to deal with it. They'd rather use a high-powered mathematical program and a DSP chip as opposed to going with fuzzy logic, which might give them a 10% performance improvement using a less expensive chip. The American mode is brute force."

Competitive edge. Inform's Hemmerlein says he does have some U.S. customers doing great things with fuzzy logic, but they won't let him publicize their names. "One company implemented a control algorithm in fuzzy logic and was surprised at how compact and efficient the code was compared with the previous C code. They went from using a DSP to using a far-cheaper 8-bit microcontroller. They say they're leaps and bounds ahead of the competition right now, and they don't want to tell people."

Even though fuzzy logic hasn't caught on as quickly in the U.S. as experts expected, they're still hopeful. But even advocates don't regard fuzzy logic as the answer to all control problems. "It's not a panacea," says Brubaker. "Your success will depend on how good an engineer you are and how familiar you are with the problem."

Fuzzy-logic resources

Two new books not only describe how fuzzy logic works, but also give application examples. The first, Fuzzy Logic & Neurofuzzy Applications Explained, by Constantin von Altrock (Prentice-Hall, Englewood Cliffs, NJ, ISBN 0-13-368465-2, $39.95), delves into more than 30 case studies. The second, Industrial Applications of Fuzzy Logic and Intelligent Systems, edited by John Yen, Reza Langari, and Lofti A. Zadeh (IEEE Press, Piscataway, NJ, ISBN 0-7803-1048-9, $64.95), is an anthology of fuzzy-logic success stories from researchers in Japan, Europe, and the U.S.

For $199, Motorola offers FLEDKT01--an education kit that includes a demo version of Fide software from Aptronix, San Jose, CA, that generates C and assembler code for several 8- and 16-bit Motorola microcontrollers.

Also for $199, National Semiconductor, Santa Clara, CA, will sell you the NeuFuz4 Learning Kit.

Inform Software Corp. has teamed up with Intel, Microchip Technology, and Texas Instruments, Siemens, and SGS-Thomson Microelectronics to provide starter tools for microprocessors, microcontrollers, and digital signal processors (DSPs) from each company. Prices start at $200.

Helicopter flies to market

Houston--Engineers at McDonnell Douglas Helicopter Systems slashed the development time for a new large-cabin, single-turbine helicopter by bringing experts from across the company together from the project's beginning.

In just over 19 weeks, the 8-place MD 600N flew for the first time--128 days after the development team received project approval. The aircraft's six-bladed main rotor system, a key feature of this larger, more powerful version of the MD 520N, was built and flight tested in just 11 weeks.

The MD 600N incorporates the new Allison 250-C47 turbine engine. The replacement includes a Full Authority Digital Engine Control to give the power plant greater efficiency and lower fuel consumption.

"While others are talking about rapid prototyping we're doing it," says Al Winn, vice president of Integrated Product Definition division, McDonnell Douglas Helicopter Systems. "We're reducing our time to market, reducing risk in the development cycle, and reducing the costs that are inherent in extended projects. "

MD officials say they encourage design team members to challenge and change existing processes. Suppliers, engineers, manufacturing personnel, and business development staff members involved from the project's inception worked together at the outset in a small, classified work area.

The result: The MD 600N flew ahead of schedule and within budget, MD says. At Heli-Expo '95, first-year MD 600N production sold out in one day.

The team plans to fly a second MD 600N prototype by the end of 1995, and expects to win Federal Aviation Administration certification by late 1996. First deliveries are slated to begin in late 1996.

Auto initiative focuses on environment

Goteborg, Sweden--Engineers at Volvo want to change the way cars are designed, and disposed of. A broad environmental initiative at the company is generating interactive databases and design innovations that could apply to cars and trucks of all makes.

For example, a new fuel database gives engineers a tool to compare the energy consumption and emissions of alternative fuels. The database takes into account energy use and emissions involved in extracting, producing, and transporting the fuels, as well as their actual engine performance.

Using a 940 engine for a baseline, Volvo engineers collected data on reformulated gas, diesel, compressed natural gas (CNG), methane, methanol, ethanol, hydrogen, electricity, and several other fuels. The software also evaluates engine modifications required to accommodate the fuels.

The software lets engineers graph comparative operating costs, efficiencies, and emissions of the fuels. Data on specific pollutants such as carbon monoxide, hydrocarbons, and nitrogen oxide can be displayed separately.

Chemical and material impacts. Another Volvo database helps engineers evaluate chemicals. "MOTIV" lets them assess the environmental impact and health, fire, and transport risks of more than 4,000 automotive chemical products.

Intended for routine use, the program provides product classifications and safety and handling regulations, and lets engineers compare all products of a specific type in order to minimize the use of toxic or hazardous chemicals. Some products MOTIV covers: Cutting fluids, adhesives, sealants, welding putty, lubricants, cleaning agents, coatings, and hydraulic fluids.

Likewise, new life-cycle analysis software for materials guides Volvo engineers in the earliest stages of design. The Environmental Priorities System, or EPS, quantifies the environmental effects of a given material. For instance, an engineer can use EPS to accurately compare the environmental impact of a body panel made of aluminum to one of plastic. The analysis takes into account raw-material production, transport, processing, performance in use, and recycling potential.

Based on their evaluations, Volvo engineers have developed electric hybrids, CNG and methane cars. Their newest electric car, based on the 850 model, uses a serial hybrid drivetrain with a gas-turbine-driven high-speed generator, nickel-cadmium batteries, and an electric motor.

"The next generation of batteries in our development program will probably be nickel-metal hybrid; lithium-based alternatives are likely to be used in the longer term," predicts Volvo Environmental Director Olle Boethius.

Volvo's Dual-Fuel vehicles use both compressed methane and gasoline. Several of the cars are already in use in a Goteborg fleet and easily meet California ULEV requirements, says Volvo fuel specialist Birger Agnetun. The driver switches from conventional gas to methane by pushing a button on the dashboard. A microprocessor and fuel distributor use engine speed, inlet manifold pressure, and oxygen-sensor input to determine the correct fuel ratio.

'Waste is a resource.' Volvo engineers and several dismantling firms have also embarked on an ambitious program to dispose of unusable cars, production waste, and used parts from service stations. At a pilot plant in Jonkoping, Sweden, engineers are developing methods for dismantling and recycling--especially plastic, rubber, and glass, which are not presently recycled from cars.

Several new technologies have emerged from the Environmental Car Recycling in Scandinavia (ECRIS) pilot program. "Vampire" devices collect hazardous liquids such as brake fluid, and wheeled pallets allow technicians to roll cars around the shop floor using one hand. A modified manufacturing fixture lets technicians rotate auto chassis 90 degrees for access to the undercarriage. The fixture is designed to accommodate many vehicle makes.

Clear ABS aids oxygen-filter design

Irvine, CA--Environmental legislation limits chemicals that manufacturers can use in their plants. This obstacle, plus material cost reductions, helped Gish Biomedical decide to switch from a polycarbonate to a clear medical-grade ABS (MABS) in the design of a new filter housing for a gas-filter line.

When Gish moved its plant to Irvine, the company learned that town laws prohibited the use of a solvent it currently used to produce the filter housing, but permitted the use of methyl ethyl ketone (MEK), which works well with MABS. MEK, on the other hand, could not be used to solvent-weld polycarbonate components. The material selected: Terlux(R) clear MABS resin from the BASF Corporation's Plastic Materials Group, Mt. Olive, NJ.

The filter housing makes up an important component in Gish's Gas Line Filter. Hospitals use the medical device to remove particulate matter from oxygen lines.

John Grossjan, Sr., manufacturing engineer at Gish, reports that the Terlux resin provides comparable clarity and impact strength to polycarbonate. In fact, with its water-clear clarity, it matches the solvent-welded polycarbonate resins at a light-transmission rate of around 90 percent.

Good clarity proved important to the clean appearance of the gas-line filters, which are tinted green to indicate they can be used with oxygen. High impact strength also was critical, since the components cannot break or shatter under operating room conditions.

The housing, which contains the filter element, connects to a clear PVC tube. The housing consists of two halves solvent-welded to ensure a void-free bond line. The filter is inserted into the oxygen line above the fluid level in the oxygenator. Typically, the filters are used for several hours in the OR setting and then replaced.

Switching from polycarbonate to a clear medical-grade ABS enabled Gish Biomedical to meet environmental laws in the design of a filter housing for its gas-line filter.

Stiffer isolator smooths ride

Brighton, MA--In small utility vehicles, vibration increases operator discomfort and fatigue and boosts maintenance costs--all factors that limit the amount of time the equipment can be used. Cushman Inc., Lincoln, NE, redesigned their GT-1 Small Utility Vehicle with the goal of decreasing vibration.

Redesign of the GT-1, which is used in turf, agriculture, and golf course maintenance, included a change from an 8-hp, 4-cycle unit to a 14-hp Vanguard V-Twin 2-cylinder, 4-cycle engine. This included a separately mounted fully automatic torque converter driven from a belt across the mounting system. But, the location of the drive belt presented a challenge.

"Having a drive belt over the mounting system is a lot like jumping on a trampoline with a rope tied around your leg," says Jim Quigley, an engineer with Clarkson Co., Hoffman Estates, IL, a Barry Controls manufacturers representative who helped Cushman with its design. While engaging the belt requires tension, too much stiffness in the direction of rotation will increase vibration.

To overcome this, a Barry Controls engineering team constructed a cradle under the engine to extend the mounting points to their most effective position. In addition, the isolators chosen were 2.5 times stiffer in the lateral direction than in the vertical. This ensured sufficient rigidity in the system to hold the belt tight without compromising isolation. Vibration isolation improved dramatically, significantly reducing noise associated with rattling sheet metal on the vehicle.

According to Barry Controls, subsequent testing of old and new GT-1s has shown isolation efficiency of the new system varied from 84 to 91 percent, depending on operating mode, while that of the old design varied from 35 to 66 percent under the same conditions.

CAD helps secure Olympic win for safety firm

Deerfield Beach, FL--Design automation technology helped bring home an Olympic win for Sensormatic Electronics Corp., the official electronic-security supplier for the 1996 games in Atlanta.

The company will be developing systems using hand geometry--an identification technology that reads the configuration of an individual's hand and bone structure--into its Sensor ID system.

In addition, Sensormatic will install computer-controlled closed-circuit cameras, fixed cameras, monitors, and video managers for surveillance of Olympic entrances, exits, grounds, and passageways.

All the company's products are designed using Intergraph EMS and electronic design software, according to Keith Sutherland, design supervisor. Its SpeedDome computerized closed-circuit television system uses five on-board microcomputers to locate targets in less than a second. One key to the device: a mechanism that lets the lens assembly rotate rapidly in three axes. Sutherland says that 3-D solid models helped determine information such as moments of inertia and centers of gravity, which are essential to designing the rotating mechanisms.

Sensormatic also uses variational design to create new parts from similar existing parts by changing key dimensions. "Using 3D modeling for design has increased overall productivity 600%," he says.

Secretary redefines 'keep in touch'

Lexington, MA--Wildfire Communications, Inc., Lexington, MA, has developed an "electronic secretary" that understands spoken commands, forwards your phone calls, and even discreetly notifies you who is calling if you're on another line.

At the heart of the Wildfire Electronic Assistant(R) is intelligent communications software on a high-performance computer. An embedded object-oriented database stores user and system information, while the Wildfire operating system provides telephony and speech recognition.

Once installed at the office and connected to the public telephone network via a digital T-1 line, the electronic assistant interacts with users through spoken commands. Then, in the office or on the road, users can request call routing, call forwarding, and messages simply by talking to the system.

Wildfire also lets users call in from a pay phone and, by saying commands such as "Call Bob Wellington," will look up a phone number and dial the call.

Engineers focused on making it as human sounding as possible, company officials say. "Originally the terminology had the flavor of talking to a computer, with messages like "Jump to" or "Start up." "Now, it's reached a much more 'human' level, as the Wildfire demonstration line (1-800-WILDFIRE) shows," says Tony Level, software engineer.

Wildfire's architecture is designed to be scalable and device-independent. In the future, Wildfire will grow to support a wide variety of communications networks and devices, according to Level.

Binoculars deliver high power in small size

New York, NY--The next time you go to a concert or sporting event, taking along a pair of binoculars may not be a hassle. That's because New York-based BNOX Inc. recently introduced a pair that weighs just four ounces and measures 2 x 2 x 4 inches.

These portable, pocket-sized binoculars, called BNOX, offer the same magnification as traditional styles (5X, 7X, and 9X versions are available), yet retail for less than $20. Traditional compact binoculars of comparable quality and magnification power cost upwards of $60.

BNOX feature a Quadratic Reflection System(TM) that uses high-reflectance mirrors rather than prisms for magnification, and high-precision, molded acrylic lenses in place of heavy glass ones.

Unlike traditional binoculars, that are basically two magnification tubes connected together, BNOX are constructed with a "nested-L" configuration. Two L-shaped plastic pieces slide together to form the rectangular shape of BNOX, then slide apart to facilitate viewing.

BNOX have a wide-angle (390 ft field of vision at 1,000 yards), televisual, rectangular "picture" like that of a television or computer screen, rather than the circular field of traditional binoculars.

BNOX are made of high-grade plastic and are resistant to water, shock, and force. The company claims they are the first new design and technological development in binoculars since the 1890s.

Currently available in southeastern U.S., BNOX will be sold nationwide by the end of 1995.

Updates refresh workhorse Suburban

Newton, MA--If cars were animals, the new Chevy Suburban might be an ox. With four-wheel drive, seats for nine, and a 10,000-lb towing capacity, this vehicle is designed for business.

It is far from "all work and no play," however. Engine enhancements and several new safety and interior features make it an enjoyable truck to drive.

The half-ton Suburban Design News drove uses a 5.7-l V8 engine that delivers 200 hp and 310 lb-ft torque. For best efficiency, the engine's electronically controlled fuel-injection system uses a powertrain control module to adjust the fuel/air mixture as many as 80 times per second.

For '95, engineers designed new high-flow exhaust manifolds to further improve engine efficiency. Powder metal connecting rods reduce internal friction and increase valve durability. Chevrolet also offers a 7.4-l V8 engine.

New safety features add to the truck's utilitarian appeal. The '95 model comes with four-wheel ABS and a driver-side airbag; the redesigned horn switch is active anywhere on the steering-wheel hub. A new brake/transmission shift interlock prevents unintended movement by forcing the driver to push the brake pedal before shifting out of park.

Bigger doesn't have to mean louder. Although the Suburban stands six feet tall and weighs about 8,000 lbs, engineers kept interior noise low. To do this, they designed a quarter-wave tuner and resonator that reflect induction sounds a half-wave out of phase. This feature is effective when towing heavy loads.

The Suburban starts at $23,897. With extras such as power driver's seat, a/c, leather, stereo cassette, cruise control, and electric mirrors, the model we tested lists at $33,180.

Windows-NT workstation targets engineers

Mountain View, CA--NEC Technologies has unveiled a RISC-based workstation for Windows NT aimed specifically at engineering applications.

The RISCstation 2200 uses 1 or 2 200-MHz MIPS R4400 microprocessors, to achieve 50-percent higher floating-point performance than Pentium-based systems, the company says. Enhanced graphics capabilities include support for 2-D and 3-D Open GL accelerator PCI cards.

NEC is betting that Windows NT will become the operating system of choice for many CAD users seeking power and flexibility who are also price-sensitive. One of the hottest engineering software vendors is also bullish on NT.

"We expect our Windows NT business to increase significantly over the next year," says Olimpio DeMarco at Parametric Technology Corp. Microsoft's Matt Ragen says that engineering has been "one of the largest markets for Windows NT since its release last fall."

Prices for NEC's RISCstation 2200 range from $5,299 to $10,874 with 1 CPU, 64M bytes RAM, 1G-byte disk, and 3-D graphics acceleration.

Rugged step-motor survives space travel

Newbury, OH--Engineers at Empire Magnetics, Rohnert Park, CA, pride themselves on their electric-motor designs for unusual environments. Recently, they created a custom size-15 step-motor for use in deep space.

The motor drives a movable calibration system (MCS) designed by Bicron for the gamma-ray telescope on the Italian Space Agency's X-ray Astronomy Satellite (SAX). Produced by Laben SPA in Milan, Italy, SAX circles in a low-earth orbit, scanning deep space for X-rays.

To maintain the telescope's performance, the MCS passes a known gamma-ray line-source (americium 241) over the telescope's scintillator once per orbit. It's here--driving a 0.375-inch diameter, 18-inch-long titanium ball-screw to move the source in a precise grid pattern--that the step motor finds a home.

Engineers had to design the motor to withstand vacuum shock, vibration, high g-loads, and repeated rapid temperature swings from 15 to +50C. And, with space launches costing tens of thousands of dollars a pound, it had to be light.

"The thermal-vacuum is undoubtedly the toughest criteria," says Bicron's director of advanced engineering, Jack White. To qualify the motor's design, White placed it in a cycling, thermal-vacuum chamber and ran it for a simulated three years of life in space.

The biggest design driver, however, involved efficiency. "They needed 100-oz-in of torque--1.4 watts of power--from 2 watts of input," says Rick Halstead, Empire Magnetics' president. To compound the problem, he had to use a non-optimized motor driver that was already space qualified.

After discarding the classic cylinder-magnet design as too inefficient, engineers turned to a complex bar-magnet rotor. Without time to construct FEA models, they built five prototypes to ensure one would meet spec. Finishing touches involved selecting bearings, lubrication, and light materials that could withstand a vacuum. A Bicron-designed inertial damper smoothes vibration. "We even found a way to hollow the titanium motor shaft to shave a few ounces," says Halstead.