Results 1 - 10
of
18
Memory representations underlying motor commands used during manipulation of common and novel objects
- J. Neurophysiol
, 1993
"... I. While subjects lifted a variety of commonly handled objects of different shapes, weights, and densities, the isometric vertical lifting force opposing the object’s weight was recorded from an analog weight scale, which was instrumented with high-stiffness ..."
Abstract
-
Cited by 26 (3 self)
- Add to MetaCart
I. While subjects lifted a variety of commonly handled objects of different shapes, weights, and densities, the isometric vertical lifting force opposing the object’s weight was recorded from an analog weight scale, which was instrumented with high-stiffness
Optimal sensorimotor transformations for balance
- Nat. Neurosci
, 2007
"... Here we have identified a sensorimotor transformation that is used by a mammalian nervous system to produce a multijoint motor behavior. Using a simple biomechanical model, a delayed-feedback rule based on an optimal tradeoff between postural error and neural effort explained patterns of muscle act ..."
Abstract
-
Cited by 14 (2 self)
- Add to MetaCart
Here we have identified a sensorimotor transformation that is used by a mammalian nervous system to produce a multijoint motor behavior. Using a simple biomechanical model, a delayed-feedback rule based on an optimal tradeoff between postural error and neural effort explained patterns of muscle activation in response to a sudden loss of balance in cats. Following the loss of large sensory afferents, changes in these muscle-activation patterns reflected an optimal reweighting of sensory feedback gains to minimize postural instability. Specifically, a loss of center-of-mass-acceleration information, which allowed for a rapid initial rise in the muscle activity in intact animals, was absent after large-fiber sensory neuropathy. Our results demonstrate that a simple and flexible neural feedback control strategy coordinates multiple muscles over time via a small set of extrinsic, task-level variables during complex multijoint natural movements.
Motion planning and control of cooperative robotic systems
, 1998
"... I would like to express my gratitude to the people who made an important difference and played a vital role in the successful completion of my Doctoral studies at the University of Pennsylvania. I am grateful to my advisor Professor Vijay Kumar without whose competence, dedication, generosity, and v ..."
Abstract
-
Cited by 8 (3 self)
- Add to MetaCart
(Show Context)
I would like to express my gratitude to the people who made an important difference and played a vital role in the successful completion of my Doctoral studies at the University of Pennsylvania. I am grateful to my advisor Professor Vijay Kumar without whose competence, dedication, generosity, and vision this dissertation would not have been possible. Professor Kumar has been my mentor and an inspiring role model. His energy and relentless support encouraged me towards the completion of my Masters in Mathematics. Professor James Ostrowski, my co-advisor since 1996, provided valuable advice and insight towards my work. I am very thankful for his opinion and guidance during the course of my dissertation. I am very thankful to Professor Joel Burdick (Caltech), Chairman of the committee, Professor G. K. Ananthasuresh, Professor Ruzena Bajcsy, Professor Vijay Kumar and Professor James Ostrowski for agreeing to be the members of my dissertation committee and for taking the time to read my thesis and provide valuable suggestions. This dissertation has allowed me to work with people who are both competent and compassionate. I have been fortunate to receive constant guidance and support from Professor
Predictive Feedforward Sensory Control During Grasping and
- Manipulation in Man. Biomedical Research 14:95
, 1993
"... During dexterous manipulation the basal relationships expressed in the employed fundamental muscle synergies are tuned precisely not only to the manipulative intent, but also to the physical properties of the object. Recent findings indicate that the sensorimotor mechanisms involved depend largely o ..."
Abstract
-
Cited by 8 (3 self)
- Add to MetaCart
(Show Context)
During dexterous manipulation the basal relationships expressed in the employed fundamental muscle synergies are tuned precisely not only to the manipulative intent, but also to the physical properties of the object. Recent findings indicate that the sensorimotor mechanisms involved depend largely on predictive rather than servo-control mechanisms: The CNS monitors specific, more-or-less expected, peripheral sensory events and use these to directly apply control signals that are appropriate for the current task and its phase. On a fast time scale, discrete mechanical events encoded in populations of somatosensory afferents trigger compensatory actions to task pertur-bations, and allow task progress to be monitored for timing the release of motor commands related to the serial manipulative phases. This type of predictive feed-forward sensory control is termed 'sensory discrete-event driven control'. On an extended time scale, previous experience with the object at hand or similar objects is used to adjust the motor commands parametrically in advance of the movement, e.g. for the object's weight and surface friction. Through vision, for instance, common objects
Two-arm manipulation tasks with friction assisted grasping
- in International Conference on Intelligent Robots and Systems
, 1997
"... ..."
(Show Context)
Anticipatory vibrotactile cueing facilitates grip force adjustment
"... Human grip forces are automatically adjusted upon occurrence of an external disturbance experienced by an object that is held by a thumb and index finger. We investigated some of the cues that may be used by the brain to perform rapid grip restabilization. To this end we ask subjects to grip and hol ..."
Abstract
-
Cited by 3 (2 self)
- Add to MetaCart
(Show Context)
Human grip forces are automatically adjusted upon occurrence of an external disturbance experienced by an object that is held by a thumb and index finger. We investigated some of the cues that may be used by the brain to perform rapid grip restabilization. To this end we ask subjects to grip and hold an instrumented and actuated parallelepiped-shaped handle between the index finger and the thumb. Under computer control, the handle could be jerked from the still grip and could independently provided vibration of 250 or 100 Hz to the gripping fingers. We found that the latency of the motor corrective action was 139 ms on average, but when a vibrotactile stimulation was applied 50 ms before the application of the pulling force, the latency was reduced on average to 117 ms. The average latency of the conscious response to the vibrotactile stimuli was 230 ms, suggesting that vibrotactile stimulation was capable of influencing the reflex action. A) Overall view grip handle B) Differential capstan drive encoder 1
Biomimetic tactile sensor for control of grip
- IEEE International Conference on Rehabilitation Robotics
"... Abstract — We are developing a novel, robust tactile sensor array that mimics the human fingertip and its distributed set of touch receptors. The mechanical components are similar to a fingertip, with a rigid core surrounded by a weakly conductive fluid contained within an elastomeric skin. It uses ..."
Abstract
-
Cited by 3 (0 self)
- Add to MetaCart
(Show Context)
Abstract — We are developing a novel, robust tactile sensor array that mimics the human fingertip and its distributed set of touch receptors. The mechanical components are similar to a fingertip, with a rigid core surrounded by a weakly conductive fluid contained within an elastomeric skin. It uses the deformable properties of the finger pad as part of the transduction process. Multiple electrodes are mounted on the surface of the rigid core and connected to impedance measuring circuitry within the core. External forces deform the fluid path around the electrodes, resulting in a distributed pattern of impedance changes containing information about those forces and the objects that applied them. Here we report preliminary results with prototypes of the sensor, and we propose strategies for extracting features related to the mechanical inputs and using this information for reflexive grip control. Index Terms — Biomimetic, electrode impedance, pressure
Time-varying enhancement of human cortical excitability mediated by cutaneous inputs during precision grip
- J. Physiol
, 1994
"... 1. We have investigated the afferent neurogram, muscular activity and mechanical responses while subjects restrained, with a precision grip, an object subjected to pulling loads directed away from the hand. At unpredictable times 'ramp-and-hold ' loads of 1 N were delivered a t a rate of c ..."
Abstract
-
Cited by 2 (1 self)
- Add to MetaCart
1. We have investigated the afferent neurogram, muscular activity and mechanical responses while subjects restrained, with a precision grip, an object subjected to pulling loads directed away from the hand. At unpredictable times 'ramp-and-hold ' loads of 1 N were delivered a t a rate of ca 80 N s-l. The load ramp produced a sharp increase in multiunit activity recorded from cutaneous afferents of the median nerve. The first response in the EMG of distal hand muscles commenced a t 51 f 2.4 ms (mean + s.D.); a further steep increase in activity began about 20 ms later, and this was associated with a marked augmentation of the grip force increase. 2. I n four subjects, transcranial magnetic stimulation (TMS) was delivered to the contralateral motor cortex in 1000 out of a total of 1500 loading trials. The time of the stimulus was randomly selected to occur either a t one of nine defined points (separated by 20 ms) before and after the computer command triggering the load force increase, or during steady periods of grip. 3. I n most hand and arm muscles, there was a powerful facilitation of the short-latency EMG responses evoked by TMS delivered 40-140 ms after the load force command. The
Somatosensory signals and sensorimotor transformations in reactive control of grasp. In: Somesthesis and the Neurobiology of the Somatosensory Cortex, edited by
, 1996
"... of grasp ..."
(Show Context)
ELECTROTACTILE FEEDBACK SYSTEM USING PSYCHOPHYSICAL MAPPING FUNCTIONS By
, 2006
"... Rights Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the aut ..."
Abstract
- Add to MetaCart
(Show Context)
Rights Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. Downloaded 12-Sep-2016 02:59:59
