Seminar 2006 10 11 High Frequency Dynamics
From CISSTwiki
CISST ERC Seminar
Characterizing and Controlling the High-Frequency Dynamics of Haptic Interfaces
Date: Wednesday, October 11, 2006
Time: 12:00pm, Lunch will be served before the seminar.
Place: Maryland Hall 110
Speaker: Katherine Kuchenbecker
Title: Characterizing and Controlling the High-Frequency Dynamics of Haptic Interfaces
Presentation slideshow: Slides are available upon request for personal use only: e-mail
Abstract:
Humans are amazingly adept at eliciting and interpreting touch-based feedback during interactions with everyday objects, naturally leveraging this wealth of dynamic information to guide both exploratory and dexterous manipulation. Haptic interfaces attempt to recreate the feel of real objects for telerobotic or virtual interactions, allowing the user to "touch" distant or unreachable environments and computer-generated models through a lightweight robotic arm. Current haptic rendering techniques, which use proportional position feedback, cannot convey a crisp contact with a hard object, nor can they convey the fine surface features of a piece of wood; instead, portrayed objects feel overly soft and unnaturally smooth or oscillatory, limiting the usefulness of teleoperation systems and virtual environments.
This work has developed methods for endowing impedance-type haptic interfaces with the high-frequency feedback signals necessary to make virtual and remote objects feel nearly indistinguishable from their real counterparts. The fundamental insight for this undertaking is that the electrical, mechanical, and biomechanical dynamics of a haptic system severely distort displayed vibrations; indeed, simply replaying a scaled version of a recorded acceleration as a motor current command does not produce the intended acceleration at the user's hand. The intervening dynamics of a haptic interface can be modeled by careful application of developed identification techniques, including comprehensive evaluation and successive isolation.
A good model of the dynamics of a haptic interface can be used to improve interaction realism in two main ways. First, the controller can compensate for the dynamics that distort high-frequency feedback signals to allow for the precise creation of fingertip accelerations during contact with remote or virtual objects. For teleoperation the target accelerations are measured in real time at the remote manipulator, and in virtual environments they are pre-recorded. Inverting the dynamics of the interface before playback creates accelerations at the user's hand that are very closely matched to the specified signals and that feel almost identical to the real object, as confirmed by a human subject study.
Second, the dynamic relationship between haptic feedback command and measured device position can be estimated and canceled to improve the stability of a haptic interface. A telerobotic system that vibrates unnaturally during contact with hard or textured objects behaves well if induced master motion is canceled from the remote robot's movement command, eliminating distracting signals and allowing the user to feel the remote environment more clearly. Both of these strategies use a dynamic model of the haptic interface's high-frequency behavior to make remote and virtual interactions feel more real. Application of these techniques to minimally invasive surgery and medical simulation is specifically promising, as it would allow physicians to feel the hardness and texture of the structures being manipulated, potentially facilitating new procedures and improving patient outcomes.
Bio:
Katherine J. Kuchenbecker works with Dr. Allison Okamura as a postdoctoral research fellow at the Johns Hopkins University. Previously supported by NSF and ARCS fellowships, she was the first doctoral student of Dr. Günter Niemeyer at Stanford University, graduating in June of 2006. She completed a Master's degree in Mechanical Engineering at Stanford in June of 2002, focusing on mechatronics, robotics, and design. She also did her undergraduate work in M.E. at Stanford, graduating as the Henry Ford scholar, the top engineering student in her class, in June of 2000. After completing her postdoc, she will become an assistant professor of Mechanical Engineering and Applied Mechanics at the University of Pennsylvania.