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Mechanical Engineering

Speaker: Kaveh Akbari Hamed
Assistant Professor
San Diego State University

Centralized and Decentralized Feedback Control Design for Robust Stabilization of Hybrid Periodic Orbits: Application to Robotic Walking

Wednesday, February 8, 2017
3:30 PM  to 4:30 PM

128  Mechanical Engineering Building
Rice University
6100 Main St
Houston, Texas, USA

The past few years have seen an accelerated effort to design rehabilitation and emergency response robots and to develop robots with human and animal traits. Legged locomotion is extremely important in this advancement. The study of legged locomotion has been motivated by the desire to allow people with disabilities to walk (i.e., co-walkers) and to assist or replace humans in hazardous environments (i.e., co-workers). Legged co-robots that can perform at this level do not yet exist, and part of what is holding back their development and deployment is adequate feedback control theory. We address periodic locomotion in legged robots. Our approach provides a systematic and computationally attractive solution to tuning the parameters in fixed-structure centralized and decentralized controllers so as to achieve local exponential orbital stability as well as H_2 robustness. We investigate nonlinear stability tools for hybrid systems to formulate the problem of designing robust nonlinear controllers as an iterative optimization problem involving bilinear and linear matrix inequalities. Our innovative algorithm overcomes the difficulties in the design of controllers arising from the high dimensionality and underactuation of increasingly sophisticated gaits in legged robots. The power of the algorithm is finally demonstrated in designing robust stabilizing centralized controllers for walking of ATRIAS, a highly underactuated 3-D bipedal robot. It is also illustrated in designing a set of robust stabilizing decentralized controllers for walking of an underactuated 3-D autonomous bipedal robot with a decentralization scheme motivated by amputee locomotion with a transpelvic prosthetic leg.

Biography of Kaveh Akbari Hamed:
Dr. Kaveh Akbari Hamed is currently an Assistant Professor at the Mechanical Engineering Department of San Diego State University. He received his Ph.D. in Electrical Engineering with specialization in Robotics and Controls from Sharif University of Technology in 2011. He held a postdoctoral research fellow position at the University of Michigan from 2012 to 2014. He is currently working on different problems and approaches related to robotics, control theory, cyber-physical systems, and optimization. His research is well positioned to transform methods for the control of a class of dynamical systems arising from legged robots with two key innovations: (1) Creating computational algorithms to systematically design robust stabilizing controllers for hybrid dynamical systems; and (2) Transferring the control framework into practice with experimental and challenging legged robots. In particular, his career goal is to provide the analytical foundation to develop effective and powerful algorithms to advance knowledge in the design of nonlinear controllers for hybrid systems.

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