New motion control tools for robotics and rehabilitation

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This research proposal concerns the development of algorithms to make robots perform complex motions with proven stability. The tools of this research are grounded in nonlinear control theory and mechanics.******Once relegated to the floors of manufacturing plants, today robots are spreading in our homes, hospitals, and the society at large. As the technology of robotics advances, there is an increasing need for control algorithms making robots perform complex tasks with proven safety. How to make a walking robot climb stairs or jump? How to make a fish-like robot swim or a snake robot crawl on land?******The traditional approach to controlling the motion of robots was to partition the motion control problem into two conceptually separate sub-problems: motion planning and trajectory tracking. Over the past fifteen years, a new paradigm has emerged for motion control of robots which is capable of producing strikingly natural motions with a superior degree of robustness. The paradigm in question is that of virtual constraints. The idea is to represent a desired motion (e.g., bipedal walking) implicitly by means of constraints on the robot joints. Such constraints do not physically exist, but they are enforced by means of feedback control, hence the adjective "virtual". While virtual constraints have come to represent a prominent paradigm for the control of walking robots, their applicability in other areas of robotics remains largely unexplored. The proposed research is driven by the conjecture that the virtual constraint paradigm is in fact applicable to a large class of motion control problems for robots, and it is a good candidate to induce biologically inspired motions of great complexity. ******Over the past few years, my collaborators and I have developed a theory of virtual constraints for robots with degree of underactuation one, i.e., robots with one actuator less than their number of degrees-of-freedom. While the results we obtained so far are encouraging, much work remains to be done, and this is the subject of my current Discovery Grant application. The research I intend to perform over the next five years has two main thrusts: theoretical and experimental. On the theoretical side, I intend to develop a new theory of virtual constraints for robots with degree of underactuation greater than one. This will allow the virtual constraint paradigm to become viable in a wide variety of robot locomotion problems. On the experimental side, I will initiate a collaborative thrust with researchers in the area of medical rehabilitation, investigating the use of virtual constraints for prosthetic devices and exoskeletons.******The long-term objective of this research is the development of a comprehensive set of tools for advanced motion control of biologically inspired robots, capable of producing complex motions that look natural, and which are endowed with a superior degree of robustness against environmental uncertainties.