- Title: Associate Professor
- Group: Mechanisms of Cognitive Control
- Status: Beckman Part-time Faculty
- Home: Aerospace Engineering
- 2143 Beckman Institute
- 405 North Mathews Avenue
- Urbana, Illinois 61801
Tim Bretl joined the Aerospace Engineering faculty at the University of Illinois at Urbana-Champaign in 2006. He is a faculty member in the Beckman Institute Artificial Intelligence group and a professor in the UIUC Department of Aerospace Engineering. He received a B.S. in Engineering and a B.A. in Mathematics from Swarthmore College in 1999. Bretl received a M.S. in 2000, then a Ph.D. in 2005, both in Aeronautics and Astronautics from Stanford University.
Tim's dissertation focused on motion planning for large free-climbing robots, which (like human free-climbers) rely only on frictional contact with rock features, not tools like pitons. This research led to a working implementation on a real robot, in cooperation with NASA-JPL. Most recently, he was a postdoctoral fellow in Computer Science at Stanford University, where he extended this work to a variety of other legged robots, including a humanoid and a hexapod for lunar exploration.
Tim develops tools for motion analysis, planning, and control. These tools include geometric search algorithms, methods of model reduction, and convex optimization routines that take advantage of problem structure. He is applying these tools to a diverse set of mechanical and biological systems: legged robots for planetary exploration, autonomous sail-planes for atmospheric and environmental science, neuro-prosthetic devices with a control interface designed using biological principles, and robotic manipulators for intelligent machining of deformable objects. All of these applications are safety-critical, so there is a strong emphasis on trust: tools must be practical, easy to implement, and have verifiable performance guarantees.
Norton, J. J. S.; Lee, D. S.; Lee, J. W.; Lee, W.; Kwon, O.; Won, P.; Jung, S. Y.; Cheng, H. Y.; Jeong, J. W.; Akce, A.; Umunna, S.; Na, I.; Kwon, Y. H.; Wang, X. Q.; Liu, Z. J.; Paik, U.; Huang, Y. G.; Bretl, T.; Yeo, W. H.; Rogers, J. A., Soft, Curved Electrode Systems Capable of Integration on the Auricle as a Persistent Brain-Computer Interface. Proceedings of the National Academy of Sciences of the United States of America 2015, 112, (13), 3920-3925, DOI: 10.1073/pnas.1424875112.
- Akce, A.; Norton, J. J. S.; Bretl, T., An Ssvep-Based Brain-Computer Interface for Text Spelling with Adaptive Queries That Maximize Information Gain Rates. IEEE Transactions on Neural Systems and Rehabilitation Engineering 2015, 23, (5), 857-866.
- Norton, J. J. S.; Lee, D. S.; Lee, J. W.; Lee, W.; Kwon, O.; Won, P.; Jung, S. Y.; Cheng, H. Y.; Jeong, J. W.; Akce, A.; Umunna, S.; Na, I.; Kwon, Y. H.; Wang, X. Q.; Liu, Z. J.; Paik, U.; Huang, Y. G.; Bretl, T.; Yeo, W. H.; Rogers, J. A., Soft, Curved Electrode Systems Capable of Integration on the Auricle as a Persistent Brain-Computer Interface. Proceedings of the National Academy of Sciences of the United States of America 2015, 112, (13), 3920-3925.
Bretl, T.; McCarthy, Z., Quasi-Static Manipulation of a Kirchhoff Elastic Rod Based on a Geometric Analysis of Equilibrium Configurations. International Journal of Robotics Research 2014, 33, (1), 48-68, DOI: 10.1177/0278364912473169.
Kennedy, M. W.; Bretl, T.; Schmiedeler, J. P., Interpreting Lateral Dynamic Weight Shifts Using a Simple Inverted Pendulum Model. Gait & Posture 2014, 40, (1), 134-139, DOI: 10.1016/j.gaitpost.2014.03.011.
Becker, A.; Onyuksel, C.; Bretl, T.; McLurkin, J., Controlling Many Differential-Drive Robots with Uniform Control Inputs. International Journal of Robotics Research 2014, 33, (13), 1626-1644, DOI:10.1177/0278364914543481.
Akhtar, A.; Norton, J. J. S.; Kasraie, M.; Bretl, T., Playing Checkers with Your Mind: An Interactive Multiplayer Hardware Game Platform for Brain-Computer Interfaces. 2014 36th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) 2014 1650-1653.
Akhtar, A.; Nguyen, M.; Wan, L.; Boyce, B.; Slade, P.; Bretl, T., Passive Mechanical Skin Stretch for Multiple Degree-of-Freedom Proprioception in a Hand Prosthesis. Haptics: Neuroscience, Devices, Modeling, and Applications, Pt II 2014, 8619, 120-128, DOI: 10.1007/978-3-662-44196-1_16.
Akhtar, A.; Nguyen, M.; Wan, L.; Boyce, B.; Slade, P.; Bretl, T., Demonstration: Passive Mechanical Skin Stretch for Multiple Degree-of-Freedom Proprioception in a Hand Prosthesis. Haptics: Neuroscience, Devices, Modeling, and Applications, Pt II 2014, 8619, 413-415.
Akhtar, A.; Boyce, B.; Bretl, T., The Relationship between Energy, Phase Charge, Impedance, and Perceived Sensation in Electrotactile Stimulation. 2014 IEEE Haptics Symposium (Haptics) 2014 69-74.
Akce, A.; Johnson, M.; Dantsker, O.; Bretl, T., A Brain-Machine Interface to Navigate a Mobile Robot in a Planar Workspace: Enabling Humans to Fly Simulated Aircraft with EEG. IEEE Transactions on Neural Systems and Rehabilitation Engineering 2013, 21, (2), 306-318.
Aghasadeghi, N.; Zhao, H. H.; Hargrove, L. J.; Ames, A. D.; Perreault, E. J.; Bretl, T., Learning Impedance Controller Parameters for Lower-Limb Prostheses, In 2013 IEEE/RSJ International Conference on Intelligent Robots and Systems. Amato, N., Ed.; IEEE, New York, 2013, 4268-4274.
Awni, H.; Norton, J. J. S.; Umunna, S.; Federmeier, K. D.; Bretl, T.; Towards a Brain Computer Interface Based on the N2pc Event-Related Potential, In 2013 6th International IEEE/EMBS Conference on Neural Engineering. IEEE, New York, 2013, 1021-1024.
Bretl, T.; McCarthy, Z., Mechanics and Quasi-Static Manipulation of Planar Elastic Kinematic Chains. IEEE Transactions on Robotics 2013, 29, (1), 1-14.
Jeong, J. W.; Yeo, W. H.; Akhtar, A.; Norton, J. J. S.; Kwack, Y. J.; Li, S.; Jung, S. Y.; Su, Y. W.; Lee, W.; Xia, J.; Cheng, H. Y.; Huang, Y. G.; Choi, W. S.; Bretl, T.; Rogers, J. A., Materials and Optimized Designs for Human-Machine Interfaces via Epidermal Electronics. Advanced Materials 2013, 25, (47), 6839-6846, DOI: 10.1002/adma.201301921.
Becker, A.; Bretl, T., Approximate Steering of a Unicycle under Bounded Model Perturbation Using Ensemble Control. IEEE Transactions on Robotics 2012, 28, (3), 580-591.
Gregg, R. D.; Tilton, A. K.; Candido, S.; Bretl, T.; Spong, M. W., Control and Planning of 3-D Dynamic Walking with Asymptotically Stable Gait Primitives. IEEE Transactions on Robotics 2012, 28, (6), 1415-1423.
Shorter, K. A.; Li, Y. F.; Bretl, T.; Hsiao-Wecksler, E. T., Modeling, Control, and Analysis of a Robotic Assist Device. Mechatronics 2012, 22, (8), 1067-1077
Bretl, T., Minimum-Time Optimal Control of Many Robots That Move in the Same Direction at Different Speeds. IEEE Transactions on Robotics 2012, 28, (2), 351-363.
Ma, R.; Aghasadeghi, N.; Jarzebowski, J.; Bretl, T.; Coleman, T. P., A Stochastic Control Approach to Optimally Designing Hierarchical Flash Sets in P300 Communication Prostheses. IEEE Transactions on Neural Systems and Rehabilitation Engineering 2012, 20, (1), 102-112.
Omar, C.; Akce, A.; Johnson, M.; Bretl, T.; Ma, R.; Maclin, E.; McCormick, M.; Coleman, T. P., A Feedback Information-Theoretic Approach to the Design of Brain-Computer Interfaces. International Journal of Human-Computer Interaction 2011, 27, (1), 5-23.
Li, D. Y.; Becker, A.; Shorter, K. A.; Bretl, T.; Hsiao-Wecksler, E. T., Estimating System State During Human Walking with a Powered Ankle-Foot Orthosis. IEEE-ASME Transactions on Mechatronics 2011, 16, (5), 835-844.
Becker, A.; Bretl, T., Motion Planning under Bounded Uncertainty Using Ensemble Control, In Robotics: Science and Systems Vi; Matsuoka, Y., Durrant Whyte, H., Neira, J., Eds. 2011, 299-306.
Bretl, T.; Arechavaleta, G.; Akce, A.; Laumond, J. P., Comments on "An Optimality Principle Governing Human Walking". IEEE Transactions on Robotics 2010, 26, (6), 1105-1106.
DeVon, D.; Bretl, T., Control of many robots moving in the same direction with different speeds: a decoupling approach, American Control Conference, St. Louis, MO, 2009.
Hauser, K.; Bretl, T.; Latombe, J. C.; Harada, K.; Wilcox, B., Motion Planning for Legged Robots on Varied Terrain. International Journal of Robotics Research 2008, 27, (11-12), 1325-1349.
Omar, C.; Johnson, M.; Bretl, T.; Coleman, T. Policies for neural prosthetic control: Initial experiments with a text interface, In American Control Conference (ACC), Seattle WA, 2008.
Omar, C.; Johnson, M.; Bretl, T.; Coleman, T. Querying the user properly for high-performance brain-machine interfaces: recursive estimation, control, and feedback information-theoretic perspectives, In IEEE International Conference on Acoustics, Speech, and Signal Processing, Las Vegas, NV, 2008.
Bretl, T.; Lall, S., Testing static equilibrium for legged robots. IEEE Transactions on Robotics 2008, 24, (4), 794-807.
Bretl, T. Control of many agents by moving their targets: Maintaining separation, In International Conference on Advanced Robotics (ICAR), Jeju, Korea, 2007.
Bretl, T. Control of many agents using few instructions, robotics, In Science and Systems (RSS), Atlanta, GA, 2007.
DeVon, D.; Bretl, T. Kinematic and dynamic control of a wheeled mobile robot, In International Conference on Intelligent Robots and Systems (IROS), San Diego, CA, 2007.
Hauser, K., Bretl, T., Harada, K., and Latombe, J.C. Using Motion Primitives in Probabilistic Sample-Based Planning for Humanoid Robots. In Workshop on the Algorithmic Foundations of Robotics (WAFR), New York, NY, 2006.
Hauser, K., Bretl, T., Latombe, J.C., and Wilcox., B. Motion Planning for a Six-Legged Lunar Robot. In Workshop on the Algorithmic Foundations of Robotics (WAFR), New York, NY, 2006.
Bretl, T.; Lall, S. A Fast and Adaptive Test of Static Equilibrium for Legged Robots. In Proc. IEEE Int. Conf. on Robotics and Automation (ICRA), Orlando, FL, 2006.
Bretl, T. Motion Planning of Multi-Limbed Robots Subject to Equilibrium Constraints: The Free-Climbing Robot Problem. International Journal of Robotics Research 2006, 25, (4), 317-342.
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