The Robotics Institute

RI | Seminar | May 5, 2006

Robotics Institute Seminar, May 5, 2006
Time and Place | Seminar Abstract | Speaker Biography | Speaker Appointments

Broadcast Feedback for Muscle Actuators and Organic Robotics:
Biologically-Inspired Cellular Actuators Using Distributed Stochastic Control

H. Harry Asada
Department of Mechanical Engineering
Massachusetts Institute of Technology


Time and Place

Mauldin Auditorium (NSH 1305)
Refreshments 3:15 pm
Talk 3:30 pm


 A biological muscle has an amazing structure consisting of a vast number of discrete cellular units, which are highly coordinated, despite limited communication and slow feedback control. This seminar presents a new framework for communication and control of a vast number of independent cellular units, and applies the concept to broad robotic systems, including artificial muscle actuators. Over the years the robotics community has been striving to develop various muscle-like actuators, ranging from PZT and SMA to conducting polymers and elastomers. These actuator materials, although an order-of-magnitude higher in stress and energy density than electro-mechanical actuators, are difficult to use due to prominent hysteresis, creep, and limited life cycle. To cope with these difficulties, a new approach is explored by dividing the actuator material into a vast number of small segments, each taking a bi-stable ON-OFF state. As the size of cellular units becomes smaller, the dynamic response gets faster, exhibiting the type of behavior of ON-OFF finite state machine. Like a biological muscle, the aggregate effect of a vast number of ON-OFF cellular units can be smooth and continuous with effective coordination.  To aggregate all the cellular units, a new control method, called “broadcast feedback”, will be developed based on stochastic control theory. In broadcast feedback, only a few global output signals are “broadcasted” to all the cellular units, which in turn make a probabilistic decision based 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. It will be shown that, although 30 percent of the cellular units are dead, the system can still track the trajectory. This cellular architecture will be applied to a five-fingered humanoid hand, and the potential of the broadcast feedback for future “organic” robots will be addressed at the end.

Speaker Biography

H. Harry Asada is Ford Professor of Mechanical Engineering and Director of the Brit and Alex d’Arbeloff Laboratory for Information Systems and Technology in the Department of Mechanical Engineering, Massachusetts Institute of Technology (MIT), Cambridge. He received the B.S., M.S., and Ph.D. degrees in precision engineering in 1973, 1975, and 1979, respectively, all from Kyoto University, Japan. He specializes in robotics, biomedical engineering, and system dynamics and control. His current research areas in robotics include actuators, vast DOF robotic systems, and broadcast feedback. His biomedical research interests include wearable health monitoring and robotic aids for bedridden patients. He received Best Paper Awards at the IEEE International Conference on Robotics and Automation in 1993, 1997, and 1999, the O. Hugo Schuck Best Paper Award from the American Control Council in 1985, and the Dynamic Systems and Control Outstanding Researcher Award from ASME in 1998. Dr. Asada is a Fellow of ASME.

Speaker Appointments

For appointments, please contact Janice Brochetti (

The Robotics Institute is part of the School of Computer Science, Carnegie Mellon University.