Featured Research

from universities, journals, and other organizations

Stopping The Noise: Active Control System Could Halt Squealing Brakes In Cars, Trucks And Buses

Date:
June 18, 2003
Source:
Georgia Institute Of Technology
Summary:
Squealing brakes cost auto manufacturers several hundred million dollars a year in warranty repairs and are among consumers' top 20 vehicle complaints – even in luxury cars. Now, acoustics researchers at the Georgia Institute of Technology have developed a solution that could stop the problem of noisy brakes once and for all.

Squealing brakes cost auto manufacturers several hundred million dollars a year in warranty repairs and are among consumers' top 20 vehicle complaints – even in luxury cars. Now, acoustics researchers at the Georgia Institute of Technology have developed a solution that could stop the problem of noisy brakes once and for all.

In disc brakes, squeal can occur when the brake pads contact the rotor while the vehicle is moving at low speeds, setting up a vibration that manifests itself as an annoying high-pitched squeal. The noise doesn't affect brake operation, but the problem – which occurs in cars, trucks and buses – leads to needless replacement of brake pads and the addition of shims, damping materials and other parts designed to stop the noise.

"A squealing brake still works, and from an engineering perspective, there is no safety problem when the brakes are squealing," said Kenneth Cunefare, an acoustics researcher in Georgia Tech's School of Mechanical Engineering. "But it's a perceived problem with the quality of the vehicle. If you've bought a new luxury car, you don't want the brakes to squeal. So manufacturers must spend money on warranty repairs that shouldn't be necessary."

Automotive engineers have learned many tricks for designing quiet braking systems, but despite their best efforts, squeal still appears unpredictably. Designers have proposed feedback control systems that would detect the noise and then generate out-of-phase vibrations to counter the specific frequency of the squeal. Because of the complexity and cost, such systems haven't been implemented.

By contrast, the Georgia Tech system would use a simple piezoceramic actuator mounted inside the brake piston to apply bursts of a "dithering" frequency to the backing plate of the inside brake pad, suppressing the vibrations that cause squeal. This active control would work despite temperature and humidity changes – and normal brake system wear – all of which can change the squeal frequency.

The system would be connected to vehicle brake light switches, turned on whenever the brakes were applied.

"Compared to feedback control, our dither system would be much simpler," Cunefare said. "It would be an open loop control system in which we won't need to detect the presence of squeal. All we would need to know is that the brakes have been applied."

Without the need for detectors or logic systems to determine the proper control frequency, the Georgia Tech system could be much simpler, with fewer components. The piezoceramic stacks that Cunefare is now testing cost $130 each today, but he estimates high-volume production should reduce that to around $30 each – and perhaps even to a few dollars each. A single frequency generator and power electronics system could serve a vehicle's entire braking system, though an actuator would be required for each brake piston.

In extensive laboratory testing using a dynamometer and acoustic measuring equipment, the system has been able to control brake squeal under a variety of different conditions. Next, Cunefare and his collaborators would like to field-test the system under real vehicle operating conditions.

"In terms of understanding the design constraints, we are pretty far along with this," he said. "We know the temperature changes we'll have to survive, and we know the forces that we'll have to generate."

Long-term reliability of the system and its potential effects on braking efficiency are among the critical long-term questions that must be answered by field testing. The brake system would still stop the vehicle if the squeal control system malfunctioned because the actuator would be located inside the piston. So far, Cunefare's testing shows minimal – or no – impact on brake performance.

"This is fundamentally a fail-safe technology," he added. "If an actuator were to break, there would still be another load path to allow the piston to operate the brakes."

While the system would probably be installed first on high-end automobiles, it could potentially be retrofitted to existing vehicles. "Our goal is to have a drop-in module that slips directly into the brake piston and connects to the vehicle wiring harness," Cunefare said.

The same principle could also be applied to drum brakes, which are used in heavier vehicles such as trucks and buses, and on the rear wheels of many automobiles.

The piezoceramic stacks consist of several layers of piezoelectric materials that stretch or contract when electrical current passes through them. Such devices are already used in vehicles, reliably powering fuel injection systems. However, when used to control brake squeal, the actuators would add to demands on vehicle electrical systems.

The actuators would operate at frequencies of about 20 kilohertz (kHz), well above where brake squeal occurs – and above the range of human hearing. The system, Cunefare said, would not be affected by anti-lock braking systems (ABS) now used on many vehicles.

The research has been supported by the National Science Foundation, using dynamometers and other equipment provided by automotive manufacturers and suppliers, including the Ford Motor Company and General Motors. The results of the research were presented in late April at the Acoustical Society of America meeting and have been the subject of papers in several professional journals, including the Journal of Sound and Vibration. In May, a paper (2003-01-1617) was presented to the 2003 SAE NVH Conference in Traverse City, MI.


Story Source:

The above story is based on materials provided by Georgia Institute Of Technology. Note: Materials may be edited for content and length.


Cite This Page:

Georgia Institute Of Technology. "Stopping The Noise: Active Control System Could Halt Squealing Brakes In Cars, Trucks And Buses." ScienceDaily. ScienceDaily, 18 June 2003. <www.sciencedaily.com/releases/2003/06/030618080125.htm>.
Georgia Institute Of Technology. (2003, June 18). Stopping The Noise: Active Control System Could Halt Squealing Brakes In Cars, Trucks And Buses. ScienceDaily. Retrieved October 21, 2014 from www.sciencedaily.com/releases/2003/06/030618080125.htm
Georgia Institute Of Technology. "Stopping The Noise: Active Control System Could Halt Squealing Brakes In Cars, Trucks And Buses." ScienceDaily. www.sciencedaily.com/releases/2003/06/030618080125.htm (accessed October 21, 2014).

Share This



More Matter & Energy News

Tuesday, October 21, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Graphene Paint Offers Rust-Free Future

Graphene Paint Offers Rust-Free Future

Reuters - Innovations Video Online (Oct. 21, 2014) British scientists have developed a prototype graphene paint that can make coatings which are resistant to liquids, gases, and chemicals. The team says the paint could have a variety of uses, from stopping ships rusting to keeping food fresher for longer. Jim Drury reports. Video provided by Reuters
Powered by NewsLook.com
Gulfstream G500, G600 Unveiling

Gulfstream G500, G600 Unveiling

Flying (Oct. 20, 2014) Watch Gulfstream's public launch of the G500 and G600 at their headquarters in Savannah, Ga., along with a surprise unveiling of the G500, which taxied up under its own power. Video provided by Flying
Powered by NewsLook.com
Japanese Scientists Unveil Floating 3D Projection

Japanese Scientists Unveil Floating 3D Projection

Reuters - Innovations Video Online (Oct. 20, 2014) Scientists in Tokyo have demonstrated what they say is the world's first 3D projection that floats in mid air. A laser that fires a pulse up to a thousand times a second superheats molecules in the air, creating a spark which can be guided to certain points in the air to shape what the human eye perceives as an image. Matthew Stock reports. Video provided by Reuters
Powered by NewsLook.com
Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-Fuel Impala

Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-Fuel Impala

3BL Media (Oct. 20, 2014) Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-fuel Impala Video provided by 3BL
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins