This project is to investigate passivity based control in bipedal locomotion. In recent years, passivity based control has proven to be one of the most powerful design methodologies for the control of electromechanical systems such as robot manipulators, underwater vehicles, induction motors, automotive and aerospace systems, and others. With a few exceptions the application of these methods to walking robots and other systems with impacts has not been adequately investigated. The project will explore several extensions of bipedal locomotion in the context of passivity based hybrid nonlinear control. The project will investigate speed regulation, the use of alternate potential functions to increase the basins of attraction of stable limit cycles, the effect of control saturation and under actuation in passivity based control, and the efficiency of passivity based control methods compared to true energy optimal control. It will also investigate passivity based control of gait transitions, including starting and stopping. The goal, and the technical merit of the project, is to help solidify the foundations of the field through analysis, development of new concepts, and the design of provably correct control algorithms. Another aspect of the project is to integrate the theoretical tools of passivity based analysis and control with studies of balance and locomotion in human subjects in order to supplement the descriptive research typical in those studies with more analytical methods.
The practical application of this research project is on the design of walking robots that have improved performance capabilities over existing machines. Current walking robots have limited range due to poor energy utilization and are limited in their ability to navigate rough terrain. More practical and more efficient walking machines will result once the full power of available theoretical tools is brought to bear on the analysis and design questions in this project. From a broader perspective, the applications of this research will extend beyond the design of improved walking machines. The analysis and design tools developed in this project will also contribute to a better understanding of human locomotion, which will result in applications in biomechanics and biomedicine, such as the design of improved prosthetic devices, the development of falls prevention programs for the elderly, and rehabilitation techniques. The impact of falls among the elderly in the United States alone has a yearly impact on the economy of more than ten billion dollars in medical bills and other expenses. The improved modeling and analysis tools of this project will be applied to real data obtained from human subjects in order to understand not only how aging affects balance and locomotion, but also how to develop intervention techniques to decrease the rate of falls.
