Aerospace Engineering and the Institute for Systems Research
This talk will describe a bio-inspired flow sensing and control system designed to enable navigation of unmanned underwater vehicles using the principles of distributed estimation and feedback control. The system is based on two types of sensor arrays — pressure sensors and velocity “whisker” sensors — that are arranged around the perimeter of a small robotic submarine immersed in a flowing water channel. Multi-modal sensor integration is one focus of the project; another focus is the demonstration of closed-loop control using bio-inspired sensing. In experimental trials to date, the submarine is shaped like a vertical airfoil and limited to two degrees of freedom: rotational motion and translational motion in the cross-stream direction. I will describe how the sensor placement is optimized using tools from nonlinear control theory, namely the empirical observability gramian, which maximizes the sensitivity to unknown flow parameters such as flow speed and angle of attack. Sensor measurements are assimilated into a recursive Bayesian filter that integrates in space (over the robot body) and time to produce probabilistic estimates of the flow parameters. The motion of the robot is determined in real time by a dynamic closed-loop control algorithm that uses the estimated parameters to guide the robot’s orientation and position. Two fish-inspired behaviors replicated to date using flow sensing and control are rheotaxis (orientating upstream) and station-holding (positioning behind a static obstacle in the flow). We have also demonstrated how to use the pressure sensors to bootstrap the velocity whiskers in order to eliminate an unrealistic (for field robotics) and inconvenient calibration procedure. Ongoing work intends to use the velocity whiskers to detect and track vortices shed in the wake of an obstacle in order to perform station-holding at low Reynolds numbers.
Derek A. Paley is the Willis H. Young Jr. Associate Professor of Aerospace Engineering Education in the Department of Aerospace Engineering and the Institute for Systems Research at the University of Maryland. He is the founding director of the Collective Dynamics and Control Laboratory and a member of the Alfred Gessow Rotorcraft Center, the Maryland Robotics Center, the Program in Neuroscience and Cognitive Science, the Burgers Program for Fluid Dynamics, and the Applied Mathematics & Statistics, and Scientific Computation Program. Paley received the B.S. degree in Applied Physics from Yale University in 1997 and the Ph.D. degree in Mechanical and Aerospace Engineering from Princeton University in 2007. He received the National Science Foundation CAREER award in 2010, the Presidential Early Career Award for Scientists and Engineers in 2012, and is co-author of Engineering Dynamics: A Comprehensive Introduction (Princeton University Press, 2011). Dr. Paley is currently a Fellow in the 2013–2014 Office of Naval Research Sabbatical Leave Program. He teaches introductory engineering dynamics, advanced dynamics, aircraft flight dynamics and control, and nonlinear control. His research interests are in the area of dynamics and control, including cooperative control of autonomous vehicles, adaptive sampling with mobile networks, and spatial modeling of biological groups. His research is based on support by the U.S. Army, the Office of Naval Research, the Air Force Office of Scientific Research, and the National Science Foundation. Paley is an Associate Fellow of AIAA and a Senior Member of IEEE. He is an Associate Editor of the AIAA Journal of Guidance, Control, and Dynamics and is a member of the IEEE Control Systems Society Aerospace Controls Technical Committee.