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User Story

Bose Corporation : Ansoft Corporation


Framingham, MA-based Bose Corporation maintains an exceptionally strong focus on research, for it is within the discipline of research that yesterday's fiction becomes tomorrow's reality. Bose engineers strive to identify things which, when made better, improve people's lives. But it's more than just research. The company aims for excellence in everything. From the way it runs its business to customer service. From the products to the owner's manuals you'll use to set them up. Bose believes that "good enough" is merely a starting point.

It's taken its commitment and passion for innovation and applied it to develop unique sound solutions to meet virtually any audio challenge in any application, even the space program. While many of its products are designed for entertainment and home audio solutions, you'll find Bose sound is prevalent in both the aviation and automotive industries, too. Bose systems can be found in stadiums and auditoriums, houses of worship, retail businesses, department stores and restaurants.

Thomas Froeschle, Bose vice president of research, says simplicity, good engineering, and elegance through styling and miniaturization are key goals in developing new Bose products. "We try to make the sound systems virtually invisible. The speakers can be almost entirely hidden away so that listeners can have the theater experience without the furniture. The process of miniaturization is very challenging. It tends to run against the paradigm that people instinctively think that things that are bigger and heavier are better and more expensive. It can be quite expensive to make a small, intense, good sounding acoustical source."

Research technologies
Froeschle and his R&D team use a suite of engineering tools. He says the greatest software expenditure for engineering is for design creation, documentation, and archiving. On the analysis side, he and other engineers are using a variety of tools for test, vibration, heat, and other mechanical analysis tools.

"Regarding the mechanical design of loudspeakers, we conduct dynamic analysis. Often, we are seeking answers with respect to vibrating walls of enclosures," adds Froeschle. "Even more challenging are the loudspeakers themselves. Analysis begins with an electrical voltage applied to the 'voice coil' of a loudspeaker. Electromagnetic forces produce mechanical motion of a loudspeaker cone, which in turn produces sound. So we often use mechanical analysis of loud speakers to better understand mechanical motion. We do a great deal of work with 1-D analysis. To do that, we use Spice software. We have our own library for analyzing loudspeaker systems. Spice also allows use to perform electronics design and analysis, as well as conceptual work regarding acoustic issues."

Software from Ansoft Corporation (Pittsburgh, PA) is an integral part of Froeschle's research. He uses the company's flagship products Maxwell 2D, Maxwell 3D, and Maxwell EMpulse. Recently, Bose implemented Ansoft's Simplorer software as well.

"Maxwell is an important tool for the prediction of loudspeaker behavior," adds Froeschle. "Using Ansoft software, we evaluate loudspeaker magnets and coil assemblies to predict the efficiency and linearity of the electromechanical conversion. In addition, we have been extensively using Ansoft products to conduct research into new ideas for electromechanical systems. In that area we are investigating linear actuators. A linear actuator is a device that moves in a single direction. We are using Maxwell to design actuators that can receive as much as 60 kilowatts of electrical power, and produce between 5,000 and 10,000 Newtons of thrust. These are very powerful devices, indeed." Froeschle and his team are also using Maxwell to study multi-phase linear actuators and to research some fast-pulse single-phase linear actuators for other applications.

In addition, Froeschle uses Ansoft products to predict eddy current associated with some of Bose's manufacturing processes. "In one case," says Froeschle, "we evaluated an induction heating process used in manufacturing to accelerate the curing of adhesives."

Benefits using Ansoft products
Froeschle says the benefits of using Ansoft software products are numerous. "The software enables us to research concepts very efficiently and has enabled us to investigate design issues more effectively than alternative methods that we have used. Working experimentally can be very slow and tedious. Often, it's hard to evaluate experimental performance because measurements are difficult, slow and expensive," Froeschle explains.

"Ansoft is an extremely useful research tool for evaluating concepts. The quality of the results is related to the number of ideas you take into consideration. The intangible is that we are thinking of new possibilities at a better level," notes Froeschle.

Bose R&D product
"We had an experience with pulse magnetization that led to some good examples of what could go wrong. The process of miniaturizing our loudspeakers is a challenge. In trying to make them virtually invisible, we try to make the speaker small but powerful. To do that, rare earth magnets are desirable because they have high volumetric energy density. These magnets require an intense magnetizing field - >3 Tesla. Creating the equipment to produce the magnetizing field in a manufacturing environment is expensive," says Froeschle.

He says that it's desirable to produce the magnetizing field for very short periods of time because the longer the magnetizing field is sustained, the more power is expended in the magnetizer coils. That power produces heating issues. "A good refrigeration system is necessary to extract heat from the magnetizing coils. So, the desire is to have short pulses in order to minimize heating," notes Froeschle. "Rise times of current pulses are in the order of two to five milliseconds." The consequences of rapid, intense pulsed fields can be significant.

There are three generic areas that are of particular interest:

"One is that a fast field does not necessarily distribute evenly throughout all regions of the magnet as might be expected with a sustained field. From a static analysis, the field might be expected to spread evenly. However, the dynamic field tends to first concentrate in certain regions of the magnet and then spread in time to other regions. In order to completely magnetize the magnet, the entire volume must be exposed to the appropriate field intensity," says Froeschle. Other factors include mechanical stresses and voltage stresses.

In the case of mechanical stresses, one Bose division proposed to design a new automotive loud speaker using an aluminum basket - the part of the loudspeaker that holds the cone. Aluminum is a highly conductive metal. Evaluating a simplified 2-D model of the proposed design using Maxwell EMpulse showed that the total induced force on the loudspeaker basket would be in excess of 5000N.

The design team was notified that the aluminum basket didn't look promising and would be difficult to handle in manufacturing. Since that was the first time that EMpulse had been used, the design team was a little skeptical of the predicted results. So, they created an alternative design with a steel basket, and they also machined an aluminum basket to see for themselves. When they placed the aluminum basket in the magnetizer, the basket bent.

"We also predicted a fairly high induced voltage > 100 volts - in a voice coil of a loudspeaker," says Froeschle. "The voice coil is the component that produces thrust on the cone. That particular coil is designed for amplifiers that produce just 15 volts peak. Facing this dilemma, we thought, 'If the voice coil is open circuited, then it will have > 100 volts on its terminal. That situation might be destructive.' Therefore, we reasoned, 'Why donít we short-out the voice coil leads?' Then, the voice coil terminals won't have any and voltage at the terminals."

Maxwell EMpulse was used to analyze behavior with the voice coil leads shorted. The analysis demonstrated that a large circulating current would be induced in the shorted voice coil giving rise to destructive forces in the coil assembly. "Based on the transient solution," adds Froeschle, "we never tried to operate the magnetizer with the loudspeaker voice coil leads shorted." The analysis proved to the speaker designers that they needed to design insulation into the voice coil to withstand a much higher voltage than they anticipated.

Time to market
Froeschle says that as a result of implementing tools such as Ansoft products, there are certain analyses that are conducted completely on the computer. When designing magnets and steel parts for speakers, for example, the R&D team doesn't bother building them anymore. There are no experimental iterations of those parts. Because of this consolidation and speed with which they are able to analyze new designs, product development time is reduced and product quality is improved.

"Ansoft products have certainly accelerated our solution process because we have so much better understanding of what was going on. Maxwell enables us to improve our designs because we can predict the fields and forces throughout the entire loudspeaker. Those fields and forces would be very difficult to measure using alternative products or methodologies," adds Froeschle.

He says that being able to consider new ideas is the most spectacular benefit of using Ansoft products. "I became an Ansoft user three years ago. At that time, I was carrying around a notebook that contained 30 years' worth of ideas that were too difficult to explore through experimental methods, and we had no software powerful enough to efficiently address the ideas. In the first year of using Ansoft, we were able to look through every concept in that notebook and determine which ones warranted further investigation.

"Maxwell 2-D, particularly in the static, parametric area, is a joy to use. It is incredible how much more productive I am. For me, it's more than a factor of 10 faster than any other magnetic tool that I have used," adds Froeschle.

Learning curve
He says the software was a breeze to learn because the user interface is very close to his own intuition. Prior to using the software, Froeschle and his team were using a competitor's product. However, as a researcher, he was inquisitive as to what other packages offered. After receiving a 30-day, fully functional copy of Maxwell 2-D, Froeschle proceeded to run the field tutorial. The results were the same as what his existing software provided. "Maxwell predicted the field as accurately as the tool we were using at the time," adds Froeschle. "I asked the Ansoft sales person why I should purchase his product because we already invested in a seemingly similar product. The sales person urged me to try the parametric solver and when I did, the light bulb went on in my head.

"I worked through the entire past year of engineering activities and expanded beyond what we had done. At the end of the 30-day trial, I called Ansoft sales person back and gave him my credit card number to purchase the software. It's just an incredible tool. The parametric solver has enabled me to understand a wide variety of problems."

For more information about Ansoft and its products, visit www.ansoft.com. Visit www.bose.com for more information about Bose Corporation.

Author: Laura Carrabine





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Page last modified on May 8, 2002
Copyright 2002 by John Stark