McMahan, William
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Electrical and Computer Engineering
Electro-Mechanical Systems
Electro-Mechanical Systems
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Now showing 1 - 4 of 4
Publication High Frequency Acceleration Feedback Significantly Increases the Realism of Haptically Rendered Textured Surfaces(2010-04-08) McMahan, William; Romano, Joseph M.; Rahuman, Amal M. Abdul; Kuchenbecker, Katherine J.Almost every physical interaction generates high frequency vibrations, especially if one of the objects is a rigid tool. Previous haptics research has hinted that the inclusion or exclusion of these signals plays a key role in the realism of haptically rendered surface textures, but this connection has not been formally investigated until now. This paper presents a human subject study that compares the performance of a variety of surface rendering algorithms for a master-slave teleoperation system; each controller provides the user with a different combination of position and acceleration feedback, and subjects compared the renderings with direct tool-mediated exploration of the real surface. We use analysis of variance to examine quantitative performance metrics and qualitative realism ratings across subjects. The results of this study show that algorithms that include high-frequency acceleration feedback in combination with position feedback achieve significantly higher realism ratings than traditional position feedback alone. Furthermore, we present a frequency-domain metric for quantifying a controller's acceleration feedback performance; given a constant surface stiffness, the median of this metric across subjects was found to have a significant positive correlation with median realism rating.Publication Octopus-Inspired Grasp-Synergies for Continuum Manipulators(2009-02-01) McMahan, William; Walker, Ian DHuman operation of continuum “continuous-backbone” manipulators remains difficult, because of both the complex kinematics of these manipulators and the need to coordinate their many degrees of freedom. We present a novel synergy-based approach for operator interfaces, by introducing a series of octopus-arm inspired grasp-synergies. These grasp-synergies automatically coordinate the degrees of freedom of the continuum manipulator, allowing an operator to perform kinematically complex grasping motions through simple and intuitive joystick inputs. This effectively reduces the complexity of operation and allows the operator to devote more of his attention to higher-level concerns (e.g. goal, environment). We demonstrate the grasp-synergies interface design in both simulation and hardware using the nine degree of freedom Octarm continuum manipulator.Publication Haptic Displayof Realistic Tool Contact via Dynamically Compensated Control of a Dedicated Actuator(2009-12-15) McMahan, William; Kuchenbecker, Katherine J.High frequency contact accelerations convey important information that the vast majority of haptic interfaces cannot render. Building on prior work, we present an approach to haptic interface design that uses a dedicated linear voice coil actuator and a dynamic system model to allow the user to feel these signals. This approach was tested through use in a bilateral teleoperation experiment where a user explored three textured surfaces under three different acceleration control architectures: none, constant gain, and dynamic compensation. The controllers that use the dedicated actuator vastly outperform traditional position-position control at conveying realistic contact accelerations. Analysis of root mean square error, linear regression, and discrete Fourier transforms of the acceleration data also indicate a slight performance benefit for dynamic compensation over constant gain.Publication Haptography: Capturing and Recreating the Rich Feel of Real Surfaces(2011-01-01) Kuchenbecker, Katherine J; Romano, Joseph; McMahan, WilliamHaptic interfaces, which allow a user to touch virtual and remote environments through a hand-held tool, have opened up exciting new possibilities for applications such as computer-aided design and robot-assisted surgery. Unfortunately, the haptic renderings produced by these systems seldom feel like authentic re-creations of the richly varied surfaces one encounters in the real world. We have thus envisioned the new approach of haptography, or haptic photography, in which an individual quickly records a physical interaction with a real surface and then recreates that experience for a user at a different time and/or place. This paper presents an overview of the goals and methods of haptography, emphasizing the importance of accurately capturing and recreating the high frequency accelerations that occur during tool-mediated interactions. In the capturing domain, we introduce a new texture modeling and synthesis method based on linear prediction applied to acceleration signals recorded from real tool interactions. For recreating, we show a new haptography handle prototype that enables the user of a Phantom Omni to feel fine surface features and textures.