This seminar is open to the public. Students in ME 328 and CS/ME 571 are required to attend.
Prof. Michael Zinn
Seminar Topic: Minimally Invasive Robotic Catheters: Addressing Challenges through Modeling, Control, and Design
In recent years, minimally-invasive surgical systems based on flexible robotic manipulators have met with success. One major advantage of the flexible manipulator approach is its superior safety characteristics as compared to rigid manipulators — a critical characteristic in sensitive applications including cardio-vascular and neurosurgical procedures. However, their soft compliant structure, in combination with internal friction, results in poor position and force regulation which have limited their use to simpler surgical procedures. To understand the underlying reasons of their performance limitations and potentially overcome them, we have undertaken a coordinated effort to develop improved modeling, controls, and device manipulation approaches. The modeling investigation has focused on developing improved models by which this behavior is explained and predicted. In this work, we explicitly incorporate internal device friction which, in combination with the flexible device structure and drive train, predicts behavior including motion hysteresis, whipping, and control-tendon aligned lobbing — behaviors which are not captured using standard linear-elastic descriptions. However, the underlying history-dependent behavior limits the ability to apply these modeling results towards improved device performance. As such, we have investigated the use of closed-loop control to mitigate the effect of both nonlinear disturbances, such as internal friction, and dynamic flexible body motions. In particular, the use of a hybrid tracking controller, where motions are decomposed and controlled in both modal and flexible-segment joint-space coordinates, has shown significant improvement in both the steady-state and dynamic response. While these improvements are notable, the interaction of the controller and uncontrolled flexible body modes limit the extent of the possible performance improvements. Finally, in an attempt to address the limitations of flexible manipulators directly, we discuss a new approach to continuum robotic manipulation, referred to as interleaved continuum-rigid manipulation, which combines flexible, actively actuated continuum segments with small rigid-link actuators. In this approach the small rigid-link joints are interleaved between successive continuum segments and provide a redundant motion and error correction capability.
Michael Zinn received the B.S. and M.S. from M.I.T. and a Ph.D. in Mechanical Engineering (2005) from Stanford University. He joined the faculty at the University of Wisconsin - Madison in 2007. His research interests are broadly directed at understanding and overcoming the design and control challenges of complex electro-mechanical systems with a primary focus on human-centered robotics. His focus on human-centered robotics spans multiple application areas including manufacturing, medical devices, and haptics. Prior to joining the UW-Madison faculty, he was Director of Systems and Controls Engineering at Hansen Medical where he helped to develop the world's first commercially available minimally invasive flexible surgical robotic system. In addition to his experience at Hansen Medical, he has over 10 years of electro-mechanical system design and manufacturing experience in aerospace and high-technology industries.