Featured Research

from universities, journals, and other organizations

Strings As Structural Elements? Engineers Devise Mathematics For New Age Structures

Date:
April 6, 2006
Source:
University of California - San Diego
Summary:
Researchers have developed a method for optimizing the initial tension of strings in tensegrity structures as well as a second technique to maximize the strength and minimize the weight of the rods and strings for a wide range of applications.

The rods in all tensegrity structures are held in tension by a system of cables. Built-in or external actuators pull the cables to deform the structure while also maintaining a desired stiffness.
Credit: Image courtesy of University of California - San Diego

Scientists at the University of California, San Diego (UCSD) have devised two mathematical tools considered to be a major contribution to the optimal design of a new generation of deformable bridges, buildings, shape-controllable airplane wings, radio antennas, and other alternatives to current structural technologies. Two reports will be published in the International Journal of Solids and Structures, with the first appearing in the April issue. The deformable characteristic is made possible with strong, ultra-light truss-like arrangements of rods suspended by strings or wires. The resulting structure incorporates tensegrity, a combination of "tension" and "integrity."

Related Articles


"Although tensegrity structures are not yet part of mainstream design engineering, we think their amazing properties explain why you find this arrangement in spider webs, the protein cytoskeleton of cells, and many other biological structures," said Robert E. Skelton, a professor of mechanical and aerospace engineering in UCSD's Jacobs School of Engineering.

Skelton and his students have pioneered the development of rigorous scientific tools to analyze the balance of forces and movement in many types of tensegrity systems. Unlike the arms and legs of a puppet, which hang from strings, the rods within a robotic tensegrity limb would be held in tension by a system of cables. Built-in actuators could pull those cables to direct the robot to wave or pick up a block.

Skelton and postdoctoral fellow Milenko Masic describe in the April issue of the International Journal of Solids and Structures a mathematical method for optimizing the initial tension of strings within defined extremes of motion.

In a second paper in the International Journal of Solids and Structures, which is available online, Skelton, Masic, and UCSD mathematics professor Philip E. Gill describe an optimization algorithm that will help tensegrity designers maximize the strength and minimize the weight of the rods and cables. A new generation of tensile-element materials has mechanical properties that are superior to those of traditional compressive elements, and the optimization algorithm by Skelton, Masic, and Gill incorporates the strength constraints of those materials. That information is used to help specify how to design a structure with the least material while retaining the desired stiffness as the structure changes shape.

"A tensegrity-based wing could change shape as an airplane gains speed, but if the stiffness was relaxed the wing would fall off" said Skelton. "In mathematical terms, our algorithm directs the tensegrity structure to maintain its stiffness as it moves from one equilibrium position to another. The beauty of this approach is we don't have to continually use energy to maintain the shape at each new equilibrium position."

The optimization algorithm relies on mathematical parameters that define the pitch (upward tilt), yaw (left or right swings), and separation distance of each of a series of identical rods. "For a tensegrity-based wing to maintain its stiffness as it changes shape, the algorithm defines an optimal 'surface' in the space of our three parameters," Skelton said. "We would then very selectively make some strings shorter and others longer in order to change the wing shape as we move along a predetermined equilibrium surface. This would require very little energy for the control feature."

Artists such as Buckminster Fuller and Kenneth Snelson appreciated the concept of tensegrity. They created sculptures with stainless steel rods and tension wires, but most engineers have regarded tensegrity sculptures in museums as curiosities. "Tensegrity, as a concept, has been around for more than 50 years, but until now we have lacked the mathematics needed to make it an engineering tool," said Skelton. "There are lots of ways to put sticks and strings together that give you nothing but a useless pile. However, our new computational tools enable us to design an airplane wing structure that can extend and retract like a bird's wing."

While relatively new materials such as Mylar, Kevlar, titanium, and specialty steels have been used in many applications, Skelton said optimized tensegrity structures with such strong, lightweight materials may help the next generation of engineers use them to reduce costs and increase performance in a variety of new ways. "The mathematical tools we're developing could revolutionize the way engineers design all sorts of structures," Skelton said.


Story Source:

The above story is based on materials provided by University of California - San Diego. Note: Materials may be edited for content and length.


Cite This Page:

University of California - San Diego. "Strings As Structural Elements? Engineers Devise Mathematics For New Age Structures." ScienceDaily. ScienceDaily, 6 April 2006. <www.sciencedaily.com/releases/2006/04/060406230835.htm>.
University of California - San Diego. (2006, April 6). Strings As Structural Elements? Engineers Devise Mathematics For New Age Structures. ScienceDaily. Retrieved November 25, 2014 from www.sciencedaily.com/releases/2006/04/060406230835.htm
University of California - San Diego. "Strings As Structural Elements? Engineers Devise Mathematics For New Age Structures." ScienceDaily. www.sciencedaily.com/releases/2006/04/060406230835.htm (accessed November 25, 2014).

Share This


More From ScienceDaily



More Health & Medicine News

Tuesday, November 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

From Popcorn To Vending Snacks: FDA Ups Calorie Count Rules

From Popcorn To Vending Snacks: FDA Ups Calorie Count Rules

Newsy (Nov. 25, 2014) The US FDA is announcing new calorie rules on Tuesday that will require everywhere from theaters to vending machines to include calorie counts. Video provided by Newsy
Powered by NewsLook.com
Daily Serving Of Yogurt Could Reduce Risk Of Type 2 Diabetes

Daily Serving Of Yogurt Could Reduce Risk Of Type 2 Diabetes

Newsy (Nov. 25, 2014) Need another reason to eat yogurt every day? Researchers now say it could reduce a person's risk of developing type 2 diabetes. Video provided by Newsy
Powered by NewsLook.com
Madagascar Working to Contain Plague Outbreak

Madagascar Working to Contain Plague Outbreak

AFP (Nov. 24, 2014) Madagascar said Monday it is trying to contain an outbreak of plague -- similar to the Black Death that swept Medieval Europe -- that has killed 40 people and is spreading to the capital Antananarivo. Duration: 00:42 Video provided by AFP
Powered by NewsLook.com
Are Female Bosses More Likely To Be Depressed?

Are Female Bosses More Likely To Be Depressed?

Newsy (Nov. 24, 2014) A new study links greater authority with increased depressive symptoms among women in the workplace. Video provided by Newsy
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


Health & Medicine

Mind & Brain

Living & Well

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