Design of biomimetic compliant devices for locomotion in liquid environments
Author:Valdivia y Alvarado, Pablo (Pablo Alvaro), 1977-
Citable URI: http://hdl.handle.net/1721.1/38927
Other Contributors:Massachusetts Institute of Technology. Dept. of Mechanical Engineering.
Department:Massachusetts Institute of Technology. Dept. of Mechanical Engineering.
Publisher:Massachusetts Institute of Technology
Presently, there is a need for devices capable of autonomous locomotion in liquid environments. Humanitarian, industrial and defense applications are numerous and include examples such as search and rescue missions, ocean exploration, and de-mining operations. Due to the nature of the environments involved, the required devices must overcome several challenges. The main challenges are related to hardware performance in terms of propulsion efficiency, mechanical robustness, maneuverability, adaptability, stealth and autonomy. Current traditional approaches that use propeller driven devices have limited success in addressing these challenges. As a result devices that mimic fish-like swimming techniques have emerged as a promising alternative that can provide additional maneuvering features and the promise of improved performance. However, the inherent problems of current biomimetic devices have been identified as: (i) mechanical complexity due to the use of discrete and rigid components, and (ii) lack of a systematic design approach. These problems limit the practical implementation of biomimetic techniques in real mission environments. This thesis presents an alternative approach for implementing biomimetic fish-like swimming techniques by exploiting natural dynamics of compliant bodies.(cont.) The resultant devices are simpler and more mechanically robust than traditional biomimetic devices. Models are developed to express both the swimming kinematics and the corresponding swimming performance of the proposed devices, in terms of material, actuation and geometry design parameters. Design methodologies that identify the required prototype design parameters for a given target performance are proposed. The designs for caranguiform and thunniform type swimming devices are presented and their performance is characterized experimentally. Predictions based on an elongated body theory model that uses a second order approximation for the body kinematics display good agreement with prototype performance. Finally, the performance limits and the sensitivity to changes in design parameters are shown to be related to the second order system approximation of the body kinematics.
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.; Includes bibliographical references (p. 161-164).
Show full item metadata
Files in this item
This item appears in the following Collection(s)
Pablo Alvarado, 46, normally affable and soft-spoken, bristles when he's called the Cesar Chavez of day laborers. Despite his accomplishments as director of the National Day Laborer Organizing Network, he doesn't see himself as a hero. "I do this work because I love it," he says. His manner is relaxed but his ebony eyes, deeply set into broad, copper-hued features, reveal fierce determination.
As a child in the farming village of El Níspero in El Salvador, Alvarado witnessed the horror of his country's 12-year civil war, which would leave 75,000 dead. On his daily walk to school, along the roadside, he saw the bodies of those who'd been murdered. Eventually the death squads claimed his teachers; Alvarado witnessed their execution. "Everyone knew someone who was killed," he recalls. Still, amid the brutality and terror, he experienced compassion, and resolved to guide his life by "acts of love."
More than 25 percent of El Salvador's population fled the country during these years. In 1990 Alvarado joined the multitude of Salvadorans entering the United States illegally.
In Los Angeles, Alvarado, who had studied sociology while in college in El Salvador, found himself seeking work in factories, construction and gardening. Although his daily experiences often were "dirty, nasty and abusive," he became convinced that "being a day laborer is honorable."
Alvarado soon volunteered to teach literacy to Latino workers and organized soccer leagues to foster friendship among Mexicans and Central Americans competing for work. He helped found the day-laborer group in 2001 and became its national director the following year.
With offices across from MacArthur Park, the organization is a coalition of nearly 50 day-laborer organizations nationwide that fight to protect the civil, labor and human rights of workers. Among numerous successes, it has created 70 centers where workers can safely solicit jobs, and has advocates for their right to do so in any public space. It has recovered "millions" in unpaid wages, Alvarado says, and represents day laborers' interests in the immigration-reform debate.
Although some day laborers are American-born, most are undocumented and mainly from Mexico and Central America. They endure discrimination, dangerous working conditions and often low wages — or none at all. Many live in fear of deportation.
Alvarado believes that the arts, especially music, can be an important force to inspire worker empowerment and dignity. In 1996 he helped found the band Los Jornaleros del Norte (The Day Laborers of the North), which has produced three albums of salsas, cumbias and ballads that express the day laborer's trials and triumphs.
As for the future? One of Alvarado's next challenges is to create a network of allies — clergy, immigrant-rights activists, labor unions, neighborhood organizations and others — to further his organization's mission.
Alvarado recognizes that no easy solution is in sight. Yet day laborers are not going away, and often they are desperate to support their families.
Alvarado is clear: "People will risk anything to feed their loved ones," he says. "My daughter is 13, and my son is 7. If I have to stand in front of a business to look for work, that's exactly what I'd do because I love them."
One of the fascinating Angelenos featured in L.A. Weekly's People 2013 issue. Check out our entire People 2013 issue here.