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GRASP Seminar Series: Spring 2006
April 14, 12:00 p.m., Wu & Chen Auditorium
Harry Asada
Massachusetts Institute of Technology
Broadcast feedback of robot muscle actuators: Biologically-inspired
cellular actuators using distributed stochastic control
Abstract: Muscle-like actuators having
high energy-density and high-force, low-speed characteristics matched
to the load impedance are expected to revolutionize robot design. Humanoids
and other robotic systems recently developed have increasing degrees of
freedom, needing novel actuators replacing traditional electromechanical
derives. In this seminar, recent progress in robot actuators using PZT,
SMA, and conducting polymers will be presented. These actuator materials,
although an order-of-magnitude higher in stress and energy density, are
difficult to use due to prominent hysteresis, creep, and limited life
cycle. To cope with these difficulties, novel system design and control
methodology based on biologically-inspired cellular architecture will
be presented in this seminar. A muscle-like actuator structure comprising
a vast number of cellular units, each taking bi-stable ON-OFF states,
will be developed and implemented. To coordinate a vast number of cellular
actuators, a new control method, called “broadcast feedback”,
will be developed for distributed stochastic control of numerous cellular
units. In broadcast feedback, only a few global output signals are “broadcasted”
to all the cellular units, which in turn make a probabilistic decision
depending on the broadcast information and local state observation. Although
there is no deterministic coordination among the vast number of cellular
units, the ensemble of the cellular actuators can track a given trajectory
accurately and robustly. Although 30 percent of the cellular units are
dead, the system can still track the trajectory. The cellular architecture
will be applied to a five-fingered humanoid hand and a snake robot for
aircraft assembly.
Biography: H. Harry Asada is Ford Professor
of Engineering in the Department of Mechanical Engineering, and Director
of the d'Arbeloff Laboratory for Information Systems and Technology at
Massachusetts Institute of Technology. He received his Ph.D. in Precision
Engineering from Kyoto University in 1979. His research interests include
robotics, biomedical engineering, dynamic systems and control, information
technology, design, and manufacturing.
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