ME Graduate Seminar

Thursday, January 25 at 3:30 pm to 4:20 pm
Seamans Center, 3505
103 South Capitol Street, Iowa City, Iowa

Decentralized Resilient Control Algorithms for Robust Stabilization of Hybrid Dynamical Systems: Application to Robotic Walking Presented by Asst. Professor Kaveh Akbari Hamed, San Diego State University Abstract: 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 for cyber-physical systems. While rapidly advancing technologies enable the design of increasingly sophisticated legged robots, the nonlinear feedback control laws currently used to achieve stable dynamic walking cannot scale with the increasing dimensionality of these robots. The centralized nature of state-of-the-art control algorithms prevents their transfer into local controllers for wearable robots like prostheses and orthoses. In this talk, we present a systematic design framework for decentralized feedback controllers that coordinate low-dimensional interconnected subsystems to achieve robust locomotion, overcoming the curse of dimensionality in autonomous legged robots and enabling cooperative human-machine walking with powered prosthetic legs. Our approach provides a systematic and computationally attractive solution to tuning the parameters for a general form of centralized and decentralized controllers so as to achieve exponential stability as well as H2 and Hinfinity robustness. We investigate nonlinear stability tools for cyber-physical systems to formulate the problem of designing resilient nonlinear controllers as an iterative optimization problem involving bilinear and linear matrix inequalities. The power of the algorithm is finally demonstrated in designing robust stabilizing centralized controllers for walking of ATRIAS, a highly underactuated autonomous bipedal robot. It is also illustrated in designing a set of robust stabilizing decentralized controllers for walking of an underactuated bipedal robot with a decentralization scheme motivated by amputee locomotion with a transpelvic prosthetic leg. Individuals with disabilities are encouraged to attend all University of Iowa sponsored events. If you have a disability that requires an accommodation in order to participate in this program, please call the department in advance, at 335-5668.

Contact Info: MIE office,, 319-335-5939