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ABSTRACT: A new method of lower-limb exoskeleton control aimed at improving the agility of leg-swing motion is presented. In the absence of control, an exoskeleton's mechanism usually hinders agility by adding mechanical impedance to the legs. The uncompensated inertia of the exoskeleton will reduce the natural frequency of leg swing, probably leading to lower step frequency during walking as well as increased metabolic energy consumption. The proposed controller emulates inertia compensation by adding a feedback loop consisting of low-pass filtered angular acceleration multiplied by a negative gain. This gain simulates negative inertia in the low-frequency range. The resulting controller combines two assistive effects: increasing the natural frequency of the lower limbs and performing net work per swing cycle. The controller was tested on a statically mounted exoskeleton that assists knee flexion and extension. Subjects performed movement sequences, first unassisted and then using the exoskeleton, in the context of a computer-based task resembling a race. In the exoskeleton's baseline state, the frequency of leg swing and the mean angular velocity were consistently reduced. The addition of inertia compensation enabled subjects to recover their normal frequency and increase their selected angular velocity. The work performed by the exoskeleton was evidenced by catch trials in the protocol.
IEEE transactions on neural systems and rehabilitation engineering: a publication of the IEEE Engineering in Medicine and Biology Society 01/2012; 20(1):68-77. · 2.42 Impact Factor
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I. J. Robotic Res. 01/2011; 30:486-499.
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IEEE T. Haptics. 01/2010; 3:189-198.
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Human Vision and Electronic Imaging XIV - part of the IS&T-SPIE Electronic Imaging Symposium, San Jose, CA, USA, January 19-22, 2009, Proceedings; 01/2009
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World Haptics 2009 - Third Joint EuroHaptics conference and Symposium on Haptic Interfaces for Virtual Environment and Teleoperator Systems, Salt Lake City, UT, USA, 18-20 March 2009; 01/2009
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IEEE T. Haptics. 01/2009; 2:224-235.
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IEEE Transactions on Robotics. 01/2007; 23:101-111.
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2007 IEEE/RSJ International Conference on Intelligent Robots and Systems, October 29 - November 2, 2007, Sheraton Hotel and Marina, San Diego, California, USA; 01/2007
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Frontiers in the Convergence of Bioscience and Information Technologies 2007, FBIT 2007, Jeju Island, Korea, October 11-13, 2007; 01/2007
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IEEE RO-MAN 2007, 16th IEEE International Symposium on Robot & Human Interactive Communication, August 26-29, 2007, Jeju Island, Korea, Proceedings; 01/2007
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Frontiers in the Convergence of Bioscience and Information Technologies 2007, FBIT 2007, Jeju Island, Korea, October 11-13, 2007; 01/2007
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Second Joint EuroHaptics Conference and Symposium on Haptic Interfaces for Virtual Environment and Teleoperator Systems (WHC 2007), 22-24 March 2007, Tsukuba, Japan; 01/2007
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ABSTRACT: We envision cobotic infinitely-variable transmissions (IVTs) as an enabling technology for haptics and prosthetics that will allow for increases in the dynamic range of these devices while simultaneously permitting reductions in actuator size and power requirements. Use of cobotic IVTs eliminates the need to make compromises on output flow and effort, which are inherent to choosing a fixed transmission ratio drivetrain. The result is a mechanism with enhanced dynamic range that extends continuously from a completely clutched state to a highly backdrivable state. This high dynamic range allows cobotic devices to control impedance with a high level of fidelity. In this paper, we discuss these and other motivations for using parallel cobotic transmission architecture in prosthetic devices.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 02/2006; 1:5635-7.
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14th International Symposium on Haptic Interfaces for Virtual Environment and Teleoperator Systems (HAPTICS 2006), 25-26 March 2006, Arlington, VA, USA, Proceedings; 01/2006
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I. J. Robotic Res. 01/2006; 25:1099-1119.
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ABSTRACT: Smooth, frictionless, kinematic constraints on the motion of a grasped object reduce the motion freedoms at the hand, but add force freedoms, that is, force directions that do not affect the motion of the object. We are studying how subjects make use of these force freedoms in static and dynamic manipulation tasks. In this study, subjects were asked to use their right hand to hold stationary a manipulandum being pulled with constant force along a low-friction linear rail. To accomplish this task, subjects had to apply an equal and opposite force along the rail, but subjects were free to apply a force against the constraint, orthogonal to the pulling force. Although constraint forces increase the magnitude of the total force vector at the hand and have no effect on the task, we found that subjects applied significant constraint forces in a consistent manner dependent on the arm and constraint configurations. We show that these results can be interpreted in terms of an objective function describing how subjects choose a particular hand force from an infinite set of hand forces that accomplish the task. Without assuming any particular form for the objective function, the data show that its level sets are convex and scale invariant (i.e., the level set shapes are independent of the hand-force magnitude). We derive the level sets, or "isocost" contours, of subjects' objective functions directly from the experimental data.
Journal of Neurophysiology 06/2005; 93(5):2752-65. · 3.32 Impact Factor
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World Haptics Conference (WHC 2005), 18-20 March 2005, Pisa, Italy; 01/2005
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World Haptics Conference (WHC 2005), 18-20 March 2005, Pisa, Italy; 01/2005
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Proceedings of the 2005 IEEE International Conference on Robotics and Automation, ICRA 2005, April 18-22, 2005, Barcelona, Spain; 01/2005
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Proceedings of the 2004 IEEE International Conference on Robotics and Automation, ICRA 2004, April 26 - May 1, 2004, New Orleans, LA, USA; 01/2004
