Title：Energy Expenditure of Actuated Dynamic Systems: Modeling and Identification with Perspectives on Negative Work
Speaker：Joo H. Kim, Ph.D. Associate Professor,
Department of Mechanical and Aerospace Engineering, New York University, USA
Time： 9:30-11:00, March 14, 2016 (Monday)
Host：Prof. Ding Guifu
Energy expenditure—as the consumption of an energy source—of actuated dynamic systems, such as machines and humans, is an important performance criterion but is complicated to measure and difficult to predict. The objective of this study is to establish rigorous mathematical models of energy expenditure for actuated dynamic systems as functions of state variables, control inputs, and system parameters. The model forms are derived theoretically using the laws of thermodynamics, the principles of multibody system dynamics, and the working principles of actuators and energy supplies, while the model parameters are estimated experimentally. The internal energy for chemical reactions (e.g., battery and food) and heat are formulated in terms of kinematic and dynamic variables. The work components for actuation (e.g., electric motor and muscle), dissipation, restoration, and reaction are formulated with respect to generalized coordinates. The (ir)reversibility of the energy transformations in actuators (regenerative vs. non-regenerative) and energy supplies (rechargeable vs. non-rechargeable) are taken into account to address negative work, as well as positive and zero work. The models are developed to reliably and accurately evaluate instantaneous energy expenditure without limitations inherent in experimental measurements or other approximation methods. Experimental and computational results of robotic and human walking energetics will be used as illustrative examples. Finally, integrating the energy expenditure models, along with novel balance criteria, into a contact optimization algorithm to determine the optimal compromise between efficiency and stability in bipedal walking will be briefly discussed.
Dr. Joo H. Kim is an Associate Professor in the Department of Mechanical and Aerospace Engineering at New York University (NYU). Dr. Kim directs the Applied Dynamics and Optimization Laboratory with fundamental disciplinary areas in multibody system dynamics, optimization theory and algorithms, and design and control of engineering and biological systems. His group’s research for application includes robots and machines, biomechanical systems, and their intersections such as powered exoskeletons and prostheses, with particular interest in nonlinear programming, contact optimization, machine and human energetics, and balance and gait stability. Dr. Kim’s research has been sponsored by NSF, NASA, NYU, and industry. He received a Ph.D. degree in mechanical engineering in 2006, M.S. degrees in mathematics, mechanical engineering, and biomedical engineering, all from the University of Iowa, and a B.S. degree in mechanical engineering from Korea University, Seoul, South Korea. Before joining NYU in 2009, he was an Adjunct Assistant Professor of Mechanical Engineering and Postdoctoral Research Scholar in the Center for Computer-Aided Design at the University of Iowa. Dr. Kim is a member of ASME and IEEE, and has organized numerous symposia and sessions in international conferences. He is currently serving as an Associate Editor for the Conference Editorial Board of the IEEE Robotics and Automation Society and the Tutorials and Workshops Chair for the 2016 ASME IDETC/CIE conferences. Dr. Kim is the recipient of several awards and honors, including the 2007 Top Government Technology of the Year Award from the State of Iowa, the 2014 AMS Best Paper Award from the ASME Computers and Information in Engineering Division, and the 2015 Freudenstein/General Motors Young Investigator Award from the ASME Design Engineering Division.