Auto engineers show different attitude about work
Troy, MI—Nearly one-third of automotive engineers surveyed say they prefer a free-agent workstyle rather than a traditional employment arrangement, according to a survey sponsored by Kelly Services, Inc. The same survey, conducted by EPIC/ MRA (Lansing, MI) shows that more than half of the 669 engineers polled say they expect to change employers before they retire.
“Downsizing in the eighties showed people that some companies aren’t loyal to their employees,” says Martin Rome, a spokesperson for Kelly Services who believes there are several reasons why engineers, IT professionals, and other in-demand employees are opting for more freedom. “A robust economy and low unemployment also contribute to the move to free-agency,” says Rome.
“Employers need to understand what motivates engineers if they want to attract and retain them,” says Ed Sarpolus, vice president of EPIC/MRA. He believes automotive engineers like their work, but that does not mean they intend to stay with their current employer or that they aren’t open to employment arrangements such as contract work.
The Engineering Society, founded as the Association of Graduate Engineers of the University of Michigan, provided the list of engineers surveyed which included engineers from many disciplines. A full copy of the survey is available at www.kellyservices.com.
BIC brushes off bristles
Milford, CT—Everyone makes mistakes—and now there’s a new way to correct them. BIC Corporation recently brushed off the familiar bristle applicator for Wite-Out Plus correction fluid and replaced it with a foam tip.
Measuring 0.075 in2 and weighing just 0.0003 oz, the new foam applicator presented both design and manufacturing challenges, starting with the selection of a foam material that could meet conflicting goals. “The foam had to be soft (but not too soft), absorbent, and capable of being bonded to a plastic stem,” explains Michael Sanok of TMP Technologies, the Buffalo, NY, contract manufacturer that helped design and now manufacturers the tips for BIC. What’s more, the foam had to exhibit enough tear strength and chemical resistance to stand up to hundreds of dips in the Wite-Out bottle. BIC and TMP ultimately chose a proprietary polyurethane foam, which TMP heat-bonds to the applicator’s polypropylene stem. To meet manufacturing volume in the millions, TMP built custom machinery that automates the foam cutting and bonding processes.
Correction purists may bristle a bit at the switch to foam, but the new “brush” material does have its advantages. According to Charlie McCaffrey, marker group product manager for BIC, the new foam applicator allows a line of text to be covered in a single stroke, and the foam maintains its shape over time for a more precise cover-up of those inevitable misssteaks.
Isuzu’s talking about a revolution
Isuzu’s new concept car, the “KAI,” turned heads at the recent Tokyo Motor Show for its definitely un-4X4 design. Named after the Japanese character for “revolution,” the design combines a contoured body with an in-your-face girder-like chassis that shouts out its off-road ruggedness. Proposed propulsion is Isuzu’s prototype common-rail direct-injection turbo-diesel engine, in a V6 DOHC 24-valve unit in 2.5 or 3.0 liter capacity.
Cravin’ CAD sharing? Viewcad.com (www.viewcad.com) allows users to share CAD drawings with anyone anywhere. There’s nothing to install (the site uses your Internet browser) and it’s free. If you’d like to check it out and see how it works, you can download a demo, take a tour, or check out the directory of public user names.
Seat standard boosts child safety
Göteborg, Sweden—Most engineers recognize the importance of child restraints in preventing automobile accident injuries. But they may not realize, according to figures gathered worldwide by Volvo, 60% of child safety seats are improperly installed or used.
To better ensure effectiveness, the International Standardization Organization (ISO) has developed the ISOFIX attachment standard for child safety seats. Cars meeting the standard will have common, built-in attachments to fit all complying seats. These will be quick and easy to install, without different belts and straps that can complicate installation and result in improper restraint. Volvo, which chaired the ISO working group, has introduced a rear-facing ISOFIX seat, but the standard is also applicable to forward-facing seats.
The ISOFIX system is made up of two metal attachments, where the seatback and cushion meet, in the outer rear seats or front passenger seat (provided an airbag is not present or is disabled if the front seat is used for a child). On the seat frame, there are two catches that fit around the car-mounted anchorages, and a guide to quickly locate the attachments when installing the seat.
Volvo’s ISOFIX has a single frame that can hold a smaller seat for infants up to about nine months and a larger one for children nine months to three years.
With the older-child seat, a sleeping position is available in non-U.S. markets. Because such a seat option is not listed under U.S. regulations, the company opted to forgo offering it for “legal reasons,” says Bill Shapiro, director of automotive safety for Volvo Cars of North America.
S/R motors poised for takeoff
Inglewood, CA—Market Analyst George Gulalo has a theory about emerging motor technologies, which is that it takes any new motor about 30 years from the point of initial development to reach widespread acceptance. “We’ve witnessed that kind of timetable for brushless dc mo-tors,” says Gulalo, who is president of Motion Tech Trends (MTT) of Ingle-wood, CA, a marketing and consulting firm for the motor and motion-control industries, “And now we see switched reluctance motors following a similar path to commercialization.”
Switched reluctance or S/R motors, which are brushless dc motors without permanent magnets in the rotor, are of interest to engineers because of their unusual combination of reliability, high-speed operation, and high-efficiency over a wide speed range. Now fifteen years—Gulalo’s midpoint—into their development cycle, these motors are just beginning to appear in volume commercial applications.
“The activity seems to have intensified during the last two years or so,” says James R. Hendershot, president of MOTORSOFT, senior technical associate at MTT and a noted S/R motor design and application expert. “There are signs of limited acceptance in certain applications, including home washing machines from Maytag [the Neptune] and Asea. Also, there seems to be a realization that S/R drives are very well suited to electric vehicle traction.”
What’s propelling S/R technology along the acceptance curve today? “Up until now, the availability and cost of electronics to commutate the motor plus excessive audible noise were factors that limited the application of S/R technology,” says Gary Clark, director of marketing for Mavrik Motors (Mentor, OH), a division of Tridelta Industries. The company holds several patents on S/R technology, including a new design that features an asymmetrical rotor.
“But over the last few years, we’ve seen electronic component costs come down. The lower price tag, combined with development of microprocessor capability and improvements in power electronics have made S/R motors more competitive against other technologies that are less dependent on electronics,” he explains. “New designs that reduce or eliminate the eliptification of the motor structure, plus new drive software techniques, have also greatly diminished the noise level as well.”
Pete Pavlick of the Lamb Division of Ametek (Kent, OH) agrees. “You really can’t underestimate the impact of advancements in electronics and software on the S/R motor market, which continue apace today. We’ve gotten over the hurdles of noise and sensitivity to electronic interference that five years ago seemed almost insurmountable, and we think further control technology developments will drive costs down even further,” he says. Lamb recently introduced the Infin-A-Tek S/R motor for floor-care applications. It uses a unique rotor configuration to reduce harmonic noise and increase efficiency.
But is S/R technology taking off or simply taxiing today? Definitely the later, both its observers and developers agree. “Existing motors can be very tenacious about giving up their markets to any new technology, and of course an S/R motor needs a box of electronics to run and control it, which makes it more expensive than any ac induction motor,” says Hendershot. “But for the right application, it definitely has its advantages.”
Commercial tilt rotor set for take off
Agusta, Italy—Developed in Italy and unveiled as a mock-up during Helitec ’99, a specialist showplace for rotary wing aircraft, the Bell/Agusta BA609 will be the first civil tilt-rotor to take to the skies. Engineering drawings are complete, metal has been cut, and the first prototype is scheduled to fly late this year.
The BA609 is an executive turboprop able to take off and land vertically. Hydraulic actuators move its engine nacelles through 90° from horizontal to vertical. Its Pratt & Whitney PT6C-67 engines, which provide forward thrust, transition in about 20 seconds to become lift engines.
Construction. Rather than driving the prop rotors directly, each engine powers a transmission. A transverse drive shaft, mounted within the wing structure, interconnects the two transmissions. The shaft drives a gearbox in each nacelle that is directly connected to the prop rotors.
Consequently, a single engine failure is less hazardous than the same failure on a normal twin engine airplane. On the BA609, prop rotors would continue to turn, giving reduced but symmetric power. On an ordinary twin, loss of an engine means asymmetric power loss.
Both three-bladed prop rotors measure 7.9m in diameter. Because the nacelles are less than 2m from the ground, spinning up the prop rotors in the airplane mode while grounded is not possible.
Like a helicopter, the BA609 has an auto-rotate capability. The turning prop rotors power hydraulic pumps that move the nacelles. In the event of catastrophic engine failure, the prop rotors will continue turning and provide power to tilt the nacelles for landing.
Operation. The BA609 starts up, one engine at a time, like a normal twin. As soon as the first engine is running, both prop rotors start turning. With both engines running at turbine temperature, the rotors collectively lift to take the aircraft off the ground.
The tilt control rotates the nacelles down about 15 degrees once the aircraft clears building height. The aircraft has a rapid climb-out and the nacelles are moved to the horizontal position.
Downwash at take off and landing is said to be similar to medium sized helicopters. Bell/Agusta claims that with two prop rotors there are two columns of moderate pressure of about 8,000 lbs. By contrast, on a large single rotor helicopter, the downwash pressure can be 15,400 lbs in a single column. To limit the downwash, the BA609 can land and takeoff in STOL mode with nacelles angled at about 45°.
First production deliveries of the BA609 are slated for the end of 2002. Bell has announced orders for 77 aircraft from 42 customers with delivery continuing until 2005. Production will be at Amarillo, TX, with another line established in due course at the Agusta plant in Italy.
A direct predecessor of the BA609 is the XV-15 research aircraft that made its first full transition in 1979. The XV-15 has been flying for 20 years and has amply demonstrated the safety, reliability, and capabilities of a small tilt-rotor aircraft.
—Norman Bartlett, U.K., Global Design News
CAD/CAM News and updates
Paris—Among the many recent CAX product releases, CATIA Version 5 Release 3 for Windows and UNIX from Dassault Systemes includes 16 Platform P1 products, and 30 Platform P2 products, five of which are new. CATIA Knowledge Expert and Generative Knowledge included in the release are both designed to incorporate extended “knowledge-management” capabilities, including the generation of intelligent designs automatically from scripts. CATIA Plant Layout lets users make the transition from 2D layout to 3D digital manufacturing methods, and CATIA Systems Routing enables fast definition of optimized 3D routes for pipes, tubes, conveyors, ductworks and raceways.
CADDS 5i R10, Parametric Technology’s latest addition to the PTC i-Series includes new hybrid surfacing capabilities, core drafting, modeling and assembly tools, new manufacturing functionality and more than 30 enhancements specifically for shipbuilding. CADDS 5i R10 is interoperable with other PTC i-Series applications via the Associative Topology Bus (ATB).
CoCreate Software Inc.’s SolidDesigner has five new modules and other significant enhancements to its 3D CAD solution. The new modules are SolidDesigner collaboration; teamwork management; and three bi-directional interfaces to CATIA, Pro/ENGINEER, and Unigraphics that enable collaboration between product-development teams in process-centric environments. CoCreate also has extended SolidDesigner to support 3D process models for 3D-based collaboration. This new Internet-based module takes advantage of technology from CoCreate’s OneSpace solution. Other enhancements to SolidDesigner 2000 include the addition of sheet-metal functionality for designing sheet-metal parts, and more than 220 additional customer-requested enhancements.
Matra Datavision has included more than 300 enhancements in EUCLID 3 V2.2, including a new database navigator, enhanced surface and solid modeling functions, new platforms and operating system support, a CATIA V4 connector, and MEGAVISION on NT. Development to port EUCLID 3 to Linux is currently in progress.
Deneb Digital Manufacturing Solutions Version 5 Release 1.1 (D5_11) provides manufacturing engineers with seamless integration between Deneb D5_11 and ENOVIA-VPM solutions for full associativity within the product and process. Deneb D5_11 supports out-of-the-box compatibility with NT systems, and the ability to directly import Unigraphics and Pro/ENGINEER geometry, plus standard translators for all mechanical CAD packages. In this release, the CATIA Direct Access module includes new support of Sun and Hewlett-Packard UNIX platforms in addition to SGI and IBM.
Unigraphics Solutions’ latest release, Parasolid Version 11.1, has improved performance and further enhances its “Extreme Modeling” with improved sweeping and lofting for complex freeform surfaces, optimized methods for deleting blend, and new direct modeling methods. The new licensing option called PS/AccessXT gives a fully functioning copy of Parasolid for the development, distribution, and support of Parasolid translators.
New developments: Parametric Technology Corp. has entered into a strategic partnership with LightWork Design (Sheffield, UK), a supplier of software tools for producing 3D computer graphics renderings and simulations. The company’s LightWorks rendering system for advanced graphics professionals integrates radiosity, ray-tracing, and scan-line rendering. PTC’s current photo -rendering solutions will be extended with the addition of LightWorks functionality for higher image quality and accuracy. Pro/ENGINEER, CDRS, and ICEM Surf will be the first products to benefit from this technology.
SAFEWORK will become a wholly owned subsidiary of Dassault Systemes, with SAFEWORK to take charge of providing an advanced human modeling infrastructure within the V5 architecture. SAFEWORK’s human modeling software provides users with anthropometrically correct mannequins used within a digital environment to simulate, demonstrate, and optimize how a specific task may be carried out. The newly acquired company will also become the leading Dassault Systems human modeling Competency Center for other Dassault Systems’ brands.
Unigraphics Solutions has partnered with C-MOLD to develop Mold IQ for validation and optimization of plastic-injection-mold design. Mold IQ will be tightly integrated with UGS’ MoldWizard application, released earlier this year. Mold IQ will provide simulation of plastic flow through the part mold including the gates and runner systems.
LMS product releases have been numerous recently, featuring: DADS v9.5, DADS/ Engine for complete engine systems, CADA-X noise and vibration portfolio on windows NT, CAT/FLANCS for product fatigue, CAT/SYSNOISE v1.0 that embeds in CATIA, and SEADS revision 1.3 for vibro-acoustic behavior of complex systems in the high-frequency range.
Collaborative applications: Thanks to the interoperability technology relationship with Elysium Co. Ltd., OneSpace V4.0 now allows transparent access to native data from CoCreate’s SolidDesigner, Dassault Systems’ CA- TIA, PTC’s Pro/ENGINEER, Unigraphics, and SDRC’s I-DEAS Master Series software applications. The company has also announced the CoCreate Engineering E-Services Partner Program, an online catalog of Internet-based collaborative-engineering services available from certified CoCreate partners. Parametric Technology Corp. has introduced the Windchill Factor! e-Series based on Windchill Release 4.0. The Windchill Factor! e-Series is comprised of eight solutions that leverage 17 new modules, including: engineering, sourcing, product management, manufacturing planning, and collaboration modules. Finally, SOLIDWORKS now offers eDrawings (patent-pending), a new type of compressed electronic drawing file that enables users to create, view, send, and receive mechanical design drawings via e-mail. The eDrawings Publisher is available for existing users of SolidWorks, AutoCAD, and any CAD system outputting a DXF or DWG file. An eDrawing file also contains intelligence not found in standard drawings.
Matra Datavision has opened the source code for Cas.Cade, with the strategic goal of becoming the 'Linux of the CAD world'. Open CASCADE source code can be downloaded from the Internet, giving developers free access to the source code of dozens of 3D geometry data structures and hundreds of modeling algorithms. Open CASCADE demonstrations can be found at the opencascade.com and opencascade.org sites, and source code on Linux is available as well.
A newly created support organization encompassing a 50-member Matra Datavision development team will also contribute to Open CASCADE and will guarantee smooth operation and utilization. According to Marc Gainette, Director, Customized Development and Open CASCADE Solutions, "We welcome participation from development leaders in research and industry in this exciting initiative. They will join our own dedicated team in contributing to the development of new features and enhancements of Open CASCADE and will drive its future evolution."
—Katherine Tyrka, France, Global Design News
Awards underscore rotomolding possibilities
Cleveland—Rotomolders know how to put their own spin on a parts competition. The Annual Product Achievement Awards from the Association of Rotational Molders highlighted six moldings that transcend the simple-part niche once associated with the process.
Top honors went to the Smart Bar, a bumper replacement designed to protect the front of a vehicle against collisions with wild animals in Australia’s outback. Molded by Team Poly Pty. Ltd. (Lonsdale, Australia), the Smart Bar mounts on vehicle’s bumper support beam and eliminates the need for the tubular metal bars that normally shield the front of the vehicle. To fill the part’s sharp corners, which can be tough to rotomold, Team Poly used a proprietary polyethylene grade developed by Courtenay Polymers Pty. Ltd. (Victoria, Australia). While Team Poly makes SmartBars for 67 different vehicles, the winning SmartBar fits GM Australia’s Holden Commodore.
First place in the Conversion category, which honors a part once produced in another process, went to the Koala Diaper Changing Station molded by Absolute Products Inc. (Broomfield, CO). Strength requirements pushed this formerly blow-molded part into rotomolding. Thanks to a network of molded-in steel support tubes, the rotomolded version supports a Baby-Huey-like 400 lbs. Absolute molded the part from a high-melt-index LLDPE.
A 10-ft tall T Rex from El Monte Plastics (South El Monte, CA) won the Large Part award. Intended to serve as a point-of-purchase display, the LLDPE dinosaur is so big that it required a 10-piece mold.
In the PVC category, a Hockey Player Bottle Opener from Dutchland Plastics (Oostburg, WI) garnered the award (see page 30). A promotional item for Molson beer, this semi-rigid PVC bust of a hockey player has a bottle opener mounted in its mouth and is filled with a mixture of cement and foam.
A portable fountain made from 25% post-consumer reground plastic took first in the Recycled Product category. Produced by American Rotational Molding Group Inc. (Anaheim, CA), the fountain first appeared in virgin LLDPE, but the company incorporated the regrind to meet customer requests. The 4 ft-high fountain, which features a granite look, breaks down into five pieces and is designed to ship in two boxes.
—Joseph Ogando, Materials Editor
Product design to production path, automated
Herzelia, Israel—Two key elements for fast production ramp up—1) off-line programming of PLCs directly from the virtual manufacturing cell, and 2) virtual commissioning—are now possible thanks to new software called ROBCAD/PLC. Jointly developed by Tecnomatix Technologies Ltd. and Siemens Automation and Drives Group, ROBCAD/PLC lets manufacturers generate PLC programs concurrently with the design process. These programs, in turn, will simulate production lines in a virtual environment.
ROBCAD, from Tecnomatix, enables production engineers to design manufacturing processes and create programs to run PLCs, robots, and machines. It then validates and optimizes the processes and programs by means of simulation. Finally, ROBCAD downloads them directly to machines on the shop floor.
“After meeting the challenge of robotic off-line programming with ROBCAD,” explains Tecnomatix President and CEO Harel Beit-On, “programming of PLCs on the shop floor was the next step to quick ramp up.”
Adds Thomas Schott, director of Automotive System Business at Siemens Automation and Drives Group: “This breakthrough became possible through cooperation of our companies and the seamless integration of ROBCAD/PLC and Simatic PLCs.”
Because the combined Siemens and Tecnomatix product allows engineers from the mechanical design and control departments to work in parallel and share manufacturing information, manufacturers can evaluate the functionality and behavior of production lines early in the production engineering phase.
“From our experience,” argues Beit-On, “programming in the virtual environment can save 5 to 10 weeks lead time of a new product launch. This translates into tens of millions of dollars in incremental profits to our customers.”
—David J. Bak, Editor-in-Chief, Global Design News
A visualization ‘fly-through’
Give an assembly worker a workstation which is ergonomically designed, and that worker will achieve cycle times which are the fastest possible. Most assembly companies, however, fail to do this. If they only planned their assembly workstations more carefully, many could significantly improve both cycle times and set-up times. So claims Ulrich Kohler, managing director of Munich-based consultants IFP. “In most projects we reduce cycle times and set up times by 10-20% just by organizing the work station in an ergonomic manner,” he comments.
The weakness many companies suffer from, says Kohler, is the tendency to clutter up their assembly workstations with weeks’ worth of piece parts. With huge quantities of components and their associated packaging crowding out the assembly station, operators are not left with enough space to do an efficient job. The logistics of parts supply, he believes, is often the area companies find they have to change to improve the ergonomics of their assembly processes, and increase throughput.
Cycle time improvement can be obtained through the detailed analysis of the assembly processes and by precisely modeling each assembly operation. Key to this task is the Tecnomatix tool AnySIM which incorporates modules for estimating assembly cycle times, planning the 3D layout of assembly facilities and checking the ergonomics of the workplace and the manual tasks. In particular, it uses a human model so that manual operations can be checked for issues such as reachability, visibility, and collisions, and they can be analyzed according to the posture, the force, and the energy that are involved in a particular task.
AnySIM also incorporates libraries of standard assembly station components as well as tools to perform time studies based on Methods Time and Motion (MTM) methodology. The result is that the basic data for a specific assembly problem can be collated very quickly and easily. System designers can then focus on looking at different solutions and balancing cycle times at the different workstations to obtain the optimum approach.
Without the computer modeling tools, such a task is almost impossible, adds Christian Meierlohr, IFP project manager. “The alternative is to use the conventional planning tools—pen and paper. But then, you are never sure that your solution actually works and that you can achieve the required cycle times. So, you have to build pilot cells to check it out. And that involves a lot of time and investment,” he explains.
Meierlohr has recently worked with one customer in the automotive supply industry to develop a new product assembly line. Starting from a prototype version of the product, the first step was to develop the actual assembly processes. AnySim then helped to assess how best to combine automated and manual assembly operations to achieve the required cycle times, and how to design the manual workstations ergonomically. It also provided the opportunity to develop a three dimensional visualization of the proposed plant. This was important, he points out, because of the innovative nature of the product and the manufacturer’s need to demonstrate to its Board members and to potential customers that it had mastered the production process.
The client, Meierlohr says, was astonished to find that manual and automatic operations could be integrated and that the assembly worker could keep up with the speed of production. “Visualization proved it would work,” he concludes.
—Anna Kochan, U.K., Global Design News
New EPDM outlasts rubber
Sittard, The Netherlands—Higher operating temperatures, coupled with increasing demands for greater functional performance over time, present a challenge to automotive suppliers. One example? Engine mounts. While natural rubber has been the preferred material for these components, new cars demand a material that not only offers exceptional dynamic performance, but the added requirements of long-term strength and fatigue resistance at elevated temperatures.
Addressing this need, DSM Elastomers has introduced Keltan® 7441A, a new EPDM developed in collaboration with the auto industry. Keltan 7441A offers an ultra-high molecular weight for dynamic high-heat applications, plus the durability to match the operating temperatures of modern automobiles.
EPDM is a synthetic rubber produced via the reaction between ethylene, propylene, and a third monomer— ENB—which makes it vulcanizable. The material, however, has not been generally accepted for demanding dynamic applications. Despite a dynamic resilience essentially equivalent to natural rubber, amorphous EPDM has tended to fall short in terms of strength properties.
DSM, working with the auto industry, has overcome this drawback by optimizing the molecular structure to provide an EPDM superior to NR in its resistance to oxidation and heat aging. Studies indicate that the dynamic stiffness ratio (dynamic modulus at high frequency to that at low) is strongly dependent on molecular weight. Natural rubber can have a higher initial strength, but ultra-high molecular weight Keltan 7441A proves superior in strength and hardness retention after heat aging at 120C.
In general, Keltan 7441A is good for high-temperature, acoustic and mechanical vibration isolation. However, DSM cautions that Keltan 7441A is not a simple “drop-in” for natural rubber, and new applications may include some design modifications to accommodate the different balance of elastomer properties. “The function of any component,” the company states, “depends on the design of the component itself as well as the material properties.”
—David J. Bak, Editor-in-Chief, Global Design News
Electronics control rear-axle steering
Schwäbisch Gemund, Germany—Put steering at both ends of long trucks and they can be maneuvered more easily. Add electronic control and rear-end steering is even more effective—tire wear is reduced, traction improved, and stability on corners enhanced.
Rear-end steering designed around a mechanical linkage between front and rear axles is not new. The complex (and heavy) arrangement of swing arms, levers, swivels, and drag links, however, requires careful maintenance.
An electronic version of ZF Friedrichshafen’s Servocom system for rear-axle steering overcomes such disadvantages. The Servocom RAS-ES works as follows:
A steering-angle sensor and wheel-speed sensor are mounted on the front axle; a second steering-angle sensor and a brake sensor are on the rear axle. During operation, the front sensors provide input to the electronic control unit. A steering characteristic curve algorithm, applied to driving speed/steering angle data, generates a nominal value for the rear axle.
Value of the actual steering angle at the back of the vehicle is differentiated with the nominal value transmitted from the front. This calculation ensures that the rear-axle setting matches the front-steering geometry. The new value passes to a control valve that operates the hydraulic steering actuator.
If the brakes are on, a servo value is input and no actuation is possible. Release the brake, move forward, turn the steering wheel, and the system begins to take effect.
Safety reasons dictate two separate hydraulic circuits— one for operating, one for centering. An engine-driven pump powers the operating circuit, which takes commands from the proportional control valve. The centering circuit is for emergencies. It comprises a hydraulic reservoir whose pressure is maintained by a wheel-driven or electrical pump. If a fault occurs, this circuit cuts in and brings the rear axle back to the in-line position.
“Servocom RAS-ES has been fitted to MAN, Renault, and Volvo vehicles,” says Walter Kogel, manager of the AF rear steering project. “To date, we have not had to make any changes to the basic system.”
—Norman Bartlett, U.K., Global Design News
Ethernet moves to the factory floor
Neckartenzlingen, Germany—Ten years ago, no serious design engineer would have suggested using Ethernet for networking factory floor devices. Ethernet, the technology for office automation, was deliberately ignored for industrial applications, and for good reasons; its lack of determinism and robustness made it a feeble, unpredictable companion for the shop floor.
Today, the scene has almost completely reversed itself. “Every part of the process control and automation industry, from embedded systems to the Fieldbus Foundation, has recognized the importance of Ethernet and TCP/IP,” says Wolfgang Schenk of Richard Hirschmann GmbH & Co., a company that supplies Ethernet hubs, components, connectors—and plenty of enthusiasm.
Why such a radical change? Over the past few years there have been many enhancements to the Ethernet standard, especially in areas of determinism, speed, and message prioritization. Rapid developments in Ethernet switching technology have eliminated what were once barriers to the adoption of Ethernet as a control network. “There is no longer any reason why Ethernet cannot be used to build deterministic fieldbus solutions that are cost-effective and open, Schenk claims. “Since Ethernet is already the network choice for business computing, its presence at the control level will make sensor-to-boardroom integration a reality.”
Another good reason manufacturers are looking at Ethernet: the coming explosion of factory floor data traffic. Over the next four years, manufacturing plant information generated by PLCs and control systems is expected to increase from 10 to 30 times the current level as smart sensors and various devices on the plant floor eat up the available bandwidth and cry out for more.
Why the need for so much data traffic? Manufacturing management has a whole bag full of new ideas it wants to try out: manufacturing execution systems, enterprise resource planning systems, attendance recording, labor reporting, materials tracking, computerized maintenance management systems, quality information systems, decision support systems, and product data management. Managers don’t see why they can’t have all these data in real time. They don’t want to wait to collect them in “batch” mode at the end of the shift or the end of the day.
For these reasons Ethernet is poised to penetrate deep into the factory network hierarchy, down to the I/O level. That makes some programmable controller (PLC) manufacturers uncomfortable. Even the recently arrived fieldbus systems are beginning to feel the impact—some say threat—of Ethernet.
Ethernet and TCP/IP. Ethernet has become a full partner with TCP/IP, even though TCP/IP has nothing to do with the Ethernet specification. Ethernet by itself only defines the first two layers of the seven-layer Open Systems Interconnect model, the physical layer and the data link layer. To function as a data communications network it must have the “communications stack” TCP/IP which is layers 3 and 4 of the OSI model. IP (Internet protocol) is used to route messages and TCP (Transmission Control Protocol), which sits on top of IP, guarantees their delivery.
IP has taken on a life of its own. As the protocol of the Internet, it has grown to the extent that it is challenging conventional switching technology in the world’s telecommunications systems. Fiberoptic networks are now being installed in Europe that will be based entirely on IP’s “connectionless” switching technology. These networks will primarily serve Internet data communications, but Internet telephones and other “Internet appliances” will soon be able to connect to the new public IP networks.
All this illustrates a key benefit of Ethernet TCP/IP technology: its ability to scale up, as the millions of Internet users will testify. Ethernet TCP/IP and the Internet are close companions; they share the same technology. A local-area Ethernet can be connected to, and function as part of the Internet; basically all that is needed is a unique IP address for each device.
Switched Ethernet. The most important Ethernet enhancement for industrial control was the introduction of switched Ethernet, which arrived in 1992.
With switched Ethernet, the central hubs become little PBX stations. Each device on the network is connected to a switch, which uses addressing information contained in the Ethernet frame to forward the message to a switch port where the destination equipment can be reached. “The ability to switch an Ethernet frame to a specific destination based upon information in the Ethernet frame rather than broadcast the frame everywhere was the crucial step in making Ethernet deterministic,” explains Schenk. Ethernet switches support multiple simultaneous communications between many devices without collisions.
Ethernet switching has revolutionized networking, and the price of switches has declined to where they can be deployed widely, claims Schenk. The Ethernet standard now has everything it needs to be a full industrial, real-time control network. It specifies full-duplex operation and link-based flow control which further overcomes the issue of determinism by giving a single station full wire-rate connection, with no risk of data collisions.
Windows NT, which is becoming the preferred operating system in industrial circles, incorporates Ethernet drivers into the operating system. Its little brother, Windows CE, is being considered as an embedded operating system for devices and controllers, leveraging Windows NT capabilities. As Schenk sees it, Windows NT is suitable for 80% of manufacturing and process control applications, Windows CE’s proposed real-time capabilities will address 16% of the remainder, leaving 4% for specialist embedded solutions.
Not everyone loves Ethernet. Some companies, who have spent fortunes over the past ten years in developing industrial networks such as Interbus, Profibus, and DeviceNet, make it clear they are not simply going to drop their investments to adopt Ethernet technology. “While some envisage Fast Ethernet as the system-wide bus up to the field level, we believe that there is no point in throwing overboard those innovations with which Profibus facilitated and promoted distribution,” says Hubert Ovenhausen, Siemens AG, Automation & Drives Group. He points out that Profibus innovations permit setpoint changes and sophisticated servo drive controls via the bus, and, coming soon, safety-related functions.
Ethernet’s lack of power on the bus is also a deficiency. Most of the industrial device-level networks supply electrical power to the instruments and sensors. There is no provision for this on Ethernet, and there probably won’t be one soon.
Yet, in spite of what the critics say, Ethernet appears to be rapidly gaining acceptance. Most observers would probably agree with Schenk when he says, “Nothing can surpass Ethernet as the lowestcost implementation of a transparent control network.”
—Michael Babb, London, Global Design News