Passive Quadrupedal Gait Synchronization for Extra Robotic Legs Using a Dynamically Coupled Double Rimless Wheel Model

The Extra Robotic Legs (XRL) system is a robotic augmentation worn by a human operator consisting of two articulated robot legs that walk with the operator and help bear a heavy backpack payload. It is desirable for the Human- XRL quadruped system to walk with the rear legs lead the front by 25% of the gait period, minimizing the energy lost from foot impacts while maximizing balance stability. Unlike quadrupedal robots, the XRL cannot command the human’s limbs to coordinate quadrupedal locomotion. Using a pair of Rimless Wheel models, it is shown that the systems coupled with a spring and damper converge to the desired 25% phase difference. A Poincar´e return map was generated using numerical simulation to examine the convergence properties to different coupler design parameters, and initial conditions. The Dynamically Coupled Double Rimless Wheel system was physically realized with a spring and dashpot chosen from the theoretical results, and initial experiments indicate that the desired synchronization properties may be achieved within several steps using this set of passive components alone

Sympathy for Strangers: Picturesque Aesthetics and the Politics of Feeling in the American Gilded Age

The middle class in both Britain and America has always been a precarious position, its vague economic perimeters and financial vulnerability making it uniquely reliant on cultural and aesthetic values to define its boundaries. In mid- to late-nineteenth century America, the ability to see aesthetically to perceive any object as beautiful or interesting became a definitive feature for a class emerging between increasingly extreme wealth and poverty. The eighteenth-century British tradition of picturesque aesthetics, which prized the rough and the natural, made aesthetic taste a means by which the nascent middle class could define its social position. In America, works by Emerson, Thoreau, and Whitman imported picturesque modes of perception and infused them with moral, spiritual, and political significance: to apprehend roughness or dereliction as beautiful became a virtuous act, fundamental to the creation of their radically new nation. The Transcendentalists made the picturesque a means of unification with otherness, a process which allowed moral sentiments to become a primary site of personal agency, and thus to serve as intervention in social problems. Frequent economic crises, mass immigration, and rapid urbanization during the Gilded Age created an urban middle class for whom aestheticizing roughness could foster a cosmopolitan identity; members of the bourgeoisie needed an antidote to their sense of the contingency and unreality of middle-class life, as well as a structure for understanding their obligations toward structurally distanced others. Sketches about the picturesque qualities of urban ghettos, ranging from touristic journalism to reform literature, educated genteel Americans on aesthetic and affective responses to class and ethnic difference. Writers responding to this tradition such as H.C. Bunner, Brander Matthews, Hutchins Hapgood, and especially William Dean Howells use the picturesque to probe their own interest and that of their class in rough people and places. The self-directed irony of their work depicts and interrogates the position of genteel viewers whose sympathy with poorer people is effected primarily through aesthetic products or cross-class spectatorship. These writers forge an important link to contemporary liberal culture, which upholds the social value of moral sentiment but consistently projects an ambivalent and ironic relation to it

Bowdoin Orient v.96, no.1-24 (1966-1967)

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