The Experts below are selected from a list of 3904938 Experts worldwide ranked by ideXlab platform
Allison M. Okamura - One of the best experts on this subject based on the ideXlab platform.
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task dynamics of prior training influence visual force estimation ability during teleoperation
arXiv: Robotics, 2020Co-Authors: Zonghe Chua, Anthony M. Jarc, Ilana Nisky, Sherry M Wren, Allison M. OkamuraAbstract:The lack of haptic feedback in Robot-assisted Minimally Invasive Surgery (RMIS) is a potential barrier to safe tissue handling during surgery. Bayesian modeling theory suggests that surgeons with experience in open or laparoscopic surgery can develop priors of tissue stiffness that translate to better force estimation abilities during RMIS compared to surgeons with no experience. To test if prior haptic experience leads to improved force estimation ability in teleoperation, 33 participants were assigned to one of three training conditions: manual manipulation, teleoperation with force feedback, or teleoperation without force feedback, and learned to tension a silicone sample to a set of force values. They were then asked to perform the tension task, and a previously unencountered palpation task, to a different set of force values under teleoperation without force feedback. Compared to the teleoperation groups, the manual group had higher force error in the tension task outside the range of forces they had trained on, but showed better speed-accuracy functions in the palpation task at low force levels. This suggests that the dynamics of the training modality affect force estimation ability during teleoperation, with the prior haptic experience accessible if formed under the same dynamics as the task.
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comparison between force controlled skin deformation feedback and hand grounded kinesthetic force feedback for sensory substitution
International Conference on Robotics and Automation, 2018Co-Authors: Yasuhisa Kamikawa, Allison M. OkamuraAbstract:Teleoperation and virtual reality systems benefit from force sensory substitution when kinesthetic force feedback devices are infeasible due to stability or workspace limitations. We compared the performance of sensory substitution when it is provided through a cutaneous method (skin deformation feedback) and a kinesthetic method (hand-grounded force feedback). For skin deformation feedback, we used a new force-controlled tactile sensory substitution device with the ability to provide tangential and normal force directly to the finger pad. Three-axis force control with 15 Hz bandwidth was achieved using a delta mechanism and three-axis force sensor. For hand-grounded force feedback, forces were grounded against the palm. As a control, world-grounded force feedback was provided using a three-degree-of-freedom kinesthetic force feedback device. Study participants were able to match a reference world-grounded force better with hand-grounded kinesthetic force feedback than with skin deformation feedback. Participants were also able to apply more accurate and precise forces with hand-grounded kinesthetic force feedback than with skin deformation feedback. Conversely, skin deformation feedback resulted in the lowest error during initial force adjustment. These experiments demonstrate relative advantages and disadvantages of skin deformation and hand-grounded kinesthetic force feedback for force sensory substitution.
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ICRA - Magnified Force Sensory Substitution for Telemanipulation via Force-Controlled Skin Deformation
2018 IEEE International Conference on Robotics and Automation (ICRA), 2018Co-Authors: Yasuhisa Kamikawa, Nima Enayati, Allison M. OkamuraAbstract:Teleoperation systems could benefit from force sensory substitution when kinesthetic force feedback systems are too bulky or expensive, and when they cause instability by magnifying force feedback. We aim to magnify force feedback using sensory substitution via force-controlled tactile skin deformation, using a device with the ability to provide tangential and normal force directly to the fingerpads. The sensory substitution device is able to provide skin deformation force feedback over ten times the maximum stable kinesthetic force feedback on a da Vinci Research Kit teleoperation system. We evaluated the effect of this force magnification in two experimental tasks where the goal was to minimize interaction force with the environment. In a peg transfer task, magnified force feedback using sensory substitution improved participants' performance for force magnifications up to ten times, but decreased performance for higher force magnifications. In a tube connection task, sensory substitution that doubled the force feedback maximized performance; there was no improvement at the larger magnifications. These experiments demonstrate that magnified force feedback using sensory substitution via force-controlled skin deformation feedback can decrease applied forces similarly to magnified kinesthetic force feedback during teleoperation.
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tactor induced skin stretch as a sensory substitution method in teleoperated palpation
IEEE Transactions on Human-Machine Systems, 2015Co-Authors: Samuel B Schorr, Ilana Nisky, Zhan Fan Quek, William R Provancher, Allison M. OkamuraAbstract:When we use a tool to explore or manipulate an object, friction between the surface of the tool and the fingerpads generates skin stretch cues that are related to the interaction forces between the tool and the object. In this study, we emulate these naturally occurring skin stretch cues in order to convey force direction and magnitude information to users during teleoperation. We hypothesize that skin stretch feedback is a useful substitute for kinesthetic force feedback in force-sensitive teleoperated tasks. In this study, ten participants performed teleoperated palpation to determine the orientation of a stiff region in a surrounding artificial tissue using five feedback conditions: skin stretch, force, reduced gain force, graphic, and vibration. When participants received skin stretch feedback, they localized the stiff region as well as with force feedback, with no increase in task completion time. Additionally, participants receiving skin-stretch feedback localized the stiff region statistically significantly more accurately than those using vibration feedback. Although participants using skin stretch exhibited higher interaction forces than when using force, vibration, and graphical feedback, skin stretch statistically significantly decreased interaction forces compared with reduced gain force feedback. Thus, skin-stretch feedback is a compelling substitute for force feedback and may be useful in scenarios where force feedback is reduced or infeasible.
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sensory substitution and augmentation using 3 degree of freedom skin deformation feedback
IEEE Transactions on Haptics, 2015Co-Authors: Zhan Fan Quek, Samuel B Schorr, Ilana Nisky, William R Provancher, Allison M. OkamuraAbstract:During tool-mediated interaction with everyday objects, we experience kinesthetic forces and tactile sensations in the form of vibration and skin deformation at the fingerpad. Fingerpad skin deformation is caused by forces applied tangentially and normally to the fingerpad skin, resulting in tangential and normal skin displacement. We designed a device to convey 3-degree-of-freedom (DoF) force information to the user via skin deformation, and conducted two experiments to determine the devices effectiveness for Force-Feedback substitution and augmentation. For sensory substitution, participants used 1-DoF and 3-DoF skin deformation feedback to locate a feature in a 3-DoF virtual environment. Participants showed improved precision and shorter completion time when using 3-DoF compared to 1-DoF skin deformation feedback. For sensory augmentation, participants traced a path in space from an initial to a target location, while under guidance from force and/or skin deformation feedback. When force feedback was augmented with skin deformation, participants reduced their path-following error over the cases when force or skin deformation feedback are used separately. We conclude that 3-DoF skin deformation feedback is effective in substituting or augmenting force feedback. Such substitution or augmentation could be used when force feedback is unattainable or attenuated due to device limitations or system instability.
David D. Yuh - One of the best experts on this subject based on the ideXlab platform.
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Effects of haptic and graphical force feedback on teleoperated palpation
2009 IEEE International Conference on Robotics and Automation, 2009Co-Authors: John C. Gwilliam, Balazs Vagvolgyi, Alexander Vacharat, David D. Yuh, Mohsen Mahvash, Allison M. OkamuraAbstract:Direct haptic feedback and graphical force feedback have both been hypothesized to improve the performance of robot-assisted surgery. In this study we evaluate the benefits of haptic and graphical force feedback on surgeon performance and tissue exploration behavior during a teleoperated palpation task of artificial tissues. Seven surgeon subjects (four experienced in robot-assisted surgery) used a 7-degree-of-freedom teleoperated surgical robot to identify a comparatively rigid rigid target object (representing a calcified artery) in phantom heart models using the following feedback conditions: (1) direct haptic and graphical feedback, (2) direct haptic only, (3) graphical feedback only, and (4) no feedback. To avoid the problems of force sensing in a minimally invasive surgical environment, we use a position-exchange controller with dynamics compensation for direct haptic feedback and a force estimator displayed via tool-tip tracking bar graph for graphical force feedback. Although the transparency of the system is limited with this approach, results show that direct haptic force feedback minimizes applied forces to the tissue, while coupled haptic and graphical force feedback minimizes subject task error. For experienced surgeons, haptic force feedback substantially reduced task error independent of graphical feedback.
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ICRA - Effects of haptic and graphical force feedback on teleoperated palpation
2009 IEEE International Conference on Robotics and Automation, 2009Co-Authors: John C. Gwilliam, Balazs Vagvolgyi, Alexander Vacharat, David D. Yuh, Mohsen Mahvash, Allison M. OkamuraAbstract:Direct haptic feedback and graphical force feedback have both been hypothesized to improve the performance of robot-assisted surgery. In this study we evaluate the benefits of haptic and graphical force feedback on surgeon performance and tissue exploration behavior during a teleoperated palpation task of artificial tissues. Seven surgeon subjects (four experienced in robot-assisted surgery) used a 7-degree-of-freedom teleoperated surgical robot to identify a comparatively rigid rigid target object (representing a calcified artery) in phantom heart models using the following feedback conditions: (1) direct haptic and graphical feedback, (2) direct haptic only, (3) graphical feedback only, and (4) no feedback. To avoid the problems of force sensing in a minimally invasive surgical environment, we use a position-exchange controller with dynamics compensation for direct haptic feedback and a force estimator displayed via tool-tip tracking bar graph for graphical force feedback. Although the transparency of the system is limited with this approach, results show that direct haptic force feedback minimizes applied forces to the tissue, while coupled haptic and graphical force feedback minimizes subject task error. For experienced surgeons, haptic force feedback substantially reduced task error independent of graphical feedback.
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effects of visual force feedback on robot assisted surgical task performance
The Journal of Thoracic and Cardiovascular Surgery, 2008Co-Authors: Carol Reiley, Allison M. Okamura, Takintope Akinbiyi, Darius Burschka, David C Chang, David D. YuhAbstract:Objective Direct haptic (force or tactile) feedback is negligible in current surgical robotic systems. The relevance of haptic feedback in robot-assisted performances of surgical tasks is controversial. We studied the effects of visual force feedback, a haptic feedback surrogate, on tying surgical knots with fine sutures similar to those used in cardiovascular surgery. Methods By using a modified da Vinci robotic system (Intuitive Surgical, Inc, Sunnyvale, Calif) equipped with force-sensing instrument tips and real-time visual force feedback overlays in the console image, 10 surgeons each tied 10 knots with and 10 knots without visual force feedback. Four surgeons had significant prior da Vinci experience, and the remaining 6 surgeons did not. Performance parameters, including suture breakage and secure knots, peak and standard deviation of applied forces, and completion times using 5-0 silk sutures, were recorded. Chi-square and Student t test analyses determined the differences between groups. Results Among surgeon subjects with robotic experience, no differences in measured performance parameters were found between robot-assisted knot ties executed with and without visual force feedback. Among surgeons without robotic experience, however, visual force feedback was associated with lower suture breakage rates, peak applied forces, and standard deviations of applied forces. Visual force feedback did not impart differences in knot completion times or loose knots for either surgeon group. Conclusions Visual force feedback resulted in reduced suture breakage, lower forces, and decreased force inconsistencies among novice robotic surgeons, although elapsed time and knot quality were unaffected. In contrast, visual force feedback did not affect these metrics among surgeons experienced with the da Vinci system. These results suggest that visual force feedback primarily benefits novice robot-assisted surgeons, with diminishing benefits among experienced surgeons.
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Effect of sensory substitution on suture-manipulation forces for robotic surgical systems.
The Journal of thoracic and cardiovascular surgery, 2005Co-Authors: Masaya Kitagawa, Allison M. Okamura, Daniell Dokko, David D. YuhAbstract:Objectives Direct haptic (force or tactile) feedback is not yet available in commercial robotic surgical systems. Previous work by our group and others suggests that haptic feedback might significantly enhance the execution of surgical tasks requiring fine suture manipulation, specifically those encountered in cardiothoracic surgery. We studied the effects of substituting direct haptic feedback with visual and auditory cues to provide the operating surgeon with a representation of the forces he or she is applying with robotic telemanipulators. Methods Using the robotic da Vinci surgical system (Intuitive Surgical, Inc, Sunnyvale, Calif), we compared applied forces during a standardized surgical knot-tying task under 4 different sensory-substitution scenarios: no feedback, auditory feedback, visual feedback, and combined auditory-visual feedback. Results The forces applied with these sensory-substitution modes more closely approximate suture tensions achieved under ideal haptic conditions (ie, hand ties) than forces applied without such sensory feedback. The consistency of applied forces during robot-assisted suture tying aided by visual feedback or combined auditory-visual feedback sensory substitution is superior to that achieved with hand ties. Robot-assisted ties aided with auditory feedback revealed levels of consistency that were generally equivalent or superior to those attained with hand ties. Visual feedback and auditory feedback improve the consistency of robotically applied forces. Conclusions Sensory substitution, in the form of visual feedback, auditory feedback, or both, confers quantifiable advantages in applied force accuracy and consistency during the performance of a simple surgical task.
Ilana Nisky - One of the best experts on this subject based on the ideXlab platform.
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Visual Feedback Weakens the Augmentation of Perceived Stiffness by Artificial Skin Stretch
2020Co-Authors: Mor Farajian, Hanna Kossowsky, Raz Leib, Ilana NiskyAbstract:Abstract Tactile stimulation devices are gaining popularity in haptic science and technology – they are lightweight, low-cost, can be easily made wearable, and do not suffer from instability during closed loop interactions with users. Applying tactile stimulation in the form of stretching the skin of the fingerpads, concurrently with kinesthetic force feedback, has been shown to augment the perceived stiffness during interactions with elastic objects. However, all of the studies to date have investigated the perceptual augmentation effects of artificial skin-stretch in the absence of visual feedback. We investigated how visual displacement feedback affects the augmentation of perceived stiffness caused by the skin-stretch. We used a forced-choice paradigm stiffness discrimination task with four different conditions: force feedback, force feedback with artificial skin-stretch, force and visual feedback, and force and visual feedback with artificial skin-stretch. We found that visual displacement feedback weakens the skin-stretch induced perceptual augmentation and improves the stiffness discrimination sensitivity.
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task dynamics of prior training influence visual force estimation ability during teleoperation
arXiv: Robotics, 2020Co-Authors: Zonghe Chua, Anthony M. Jarc, Ilana Nisky, Sherry M Wren, Allison M. OkamuraAbstract:The lack of haptic feedback in Robot-assisted Minimally Invasive Surgery (RMIS) is a potential barrier to safe tissue handling during surgery. Bayesian modeling theory suggests that surgeons with experience in open or laparoscopic surgery can develop priors of tissue stiffness that translate to better force estimation abilities during RMIS compared to surgeons with no experience. To test if prior haptic experience leads to improved force estimation ability in teleoperation, 33 participants were assigned to one of three training conditions: manual manipulation, teleoperation with force feedback, or teleoperation without force feedback, and learned to tension a silicone sample to a set of force values. They were then asked to perform the tension task, and a previously unencountered palpation task, to a different set of force values under teleoperation without force feedback. Compared to the teleoperation groups, the manual group had higher force error in the tension task outside the range of forces they had trained on, but showed better speed-accuracy functions in the palpation task at low force levels. This suggests that the dynamics of the training modality affect force estimation ability during teleoperation, with the prior haptic experience accessible if formed under the same dynamics as the task.
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tactor induced skin stretch as a sensory substitution method in teleoperated palpation
IEEE Transactions on Human-Machine Systems, 2015Co-Authors: Samuel B Schorr, Ilana Nisky, Zhan Fan Quek, William R Provancher, Allison M. OkamuraAbstract:When we use a tool to explore or manipulate an object, friction between the surface of the tool and the fingerpads generates skin stretch cues that are related to the interaction forces between the tool and the object. In this study, we emulate these naturally occurring skin stretch cues in order to convey force direction and magnitude information to users during teleoperation. We hypothesize that skin stretch feedback is a useful substitute for kinesthetic force feedback in force-sensitive teleoperated tasks. In this study, ten participants performed teleoperated palpation to determine the orientation of a stiff region in a surrounding artificial tissue using five feedback conditions: skin stretch, force, reduced gain force, graphic, and vibration. When participants received skin stretch feedback, they localized the stiff region as well as with force feedback, with no increase in task completion time. Additionally, participants receiving skin-stretch feedback localized the stiff region statistically significantly more accurately than those using vibration feedback. Although participants using skin stretch exhibited higher interaction forces than when using force, vibration, and graphical feedback, skin stretch statistically significantly decreased interaction forces compared with reduced gain force feedback. Thus, skin-stretch feedback is a compelling substitute for force feedback and may be useful in scenarios where force feedback is reduced or infeasible.
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sensory substitution and augmentation using 3 degree of freedom skin deformation feedback
IEEE Transactions on Haptics, 2015Co-Authors: Zhan Fan Quek, Samuel B Schorr, Ilana Nisky, William R Provancher, Allison M. OkamuraAbstract:During tool-mediated interaction with everyday objects, we experience kinesthetic forces and tactile sensations in the form of vibration and skin deformation at the fingerpad. Fingerpad skin deformation is caused by forces applied tangentially and normally to the fingerpad skin, resulting in tangential and normal skin displacement. We designed a device to convey 3-degree-of-freedom (DoF) force information to the user via skin deformation, and conducted two experiments to determine the devices effectiveness for Force-Feedback substitution and augmentation. For sensory substitution, participants used 1-DoF and 3-DoF skin deformation feedback to locate a feature in a 3-DoF virtual environment. Participants showed improved precision and shorter completion time when using 3-DoF compared to 1-DoF skin deformation feedback. For sensory augmentation, participants traced a path in space from an initial to a target location, while under guidance from force and/or skin deformation feedback. When force feedback was augmented with skin deformation, participants reduced their path-following error over the cases when force or skin deformation feedback are used separately. We conclude that 3-DoF skin deformation feedback is effective in substituting or augmenting force feedback. Such substitution or augmentation could be used when force feedback is unattainable or attenuated due to device limitations or system instability.
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The effect of force feedback delay on stiffness perception and grip force modulation during tool-mediated interaction with elastic force fields
Journal of neurophysiology, 2015Co-Authors: Raz Leib, Amir Karniel, Ilana NiskyAbstract:During interaction with objects, we form an internal representation of their mechanical properties. This representation is used for perception and for guiding actions, such as in precision grip, where grip force is modulated with the predicted load forces. In this study, we explored the relationship between grip force adjustment and perception of stiffness during interaction with linear elastic force fields. In a forced-choice paradigm, participants probed pairs of virtual force fields while grasping a force sensor that was attached to a haptic device. For each pair, they were asked which field had higher level of stiffness. In half of the pairs, the force feedback of one of the fields was delayed. Participants underestimated the stiffness of the delayed field relatively to the nondelayed, but their grip force characteristics were similar in both conditions. We analyzed the magnitude of the grip force and the lag between the grip force and the load force in the exploratory probing movements within each trial. Right before answering which force field had higher level of stiffness, both magnitude and lag were similar between delayed and nondelayed force fields. These results suggest that an accurate internal representation of environment stiffness and time delay was used for adjusting the grip force. However, this representation did not help in eliminating the bias in stiffness perception. We argue that during performance of a perceptual task that is based on proprioceptive feedback, separate neural mechanisms are responsible for perception and action-related computations in the brain.
John C. Gwilliam - One of the best experts on this subject based on the ideXlab platform.
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force feedback and sensory substitution for robot assisted surgery
2011Co-Authors: Allison M. Okamura, John C. Gwilliam, Lawton N. Verner, Tomonori Yamamoto, Paul G GriffithsAbstract:It is hypothesized that the lack of haptic (force and tactile) feedback presented to the surgeon is a limiting factor in the performance of teleoperated robot-assisted minimally invasive surgery. This chapter reviews the technical challenges of creating force feedback in robot-assisted surgical systems and describes recent results in creating and evaluating the effectiveness of this feedback in mock surgical tasks. In the design of a Force-Feedback teleoperator, the importance of hardware design choices and their relationship to controller design are emphasized. In addition, the practicality and necessity of force feedback in all degrees of freedom of the teleoperator are considered in the context of surgical tasks and the operating room environment. An alternative to direct force feedback to the surgeon’s hands is sensory substitution/augmented reality, in which graphical displays are used to convey information about the forces between the surgical instrument and the patient, or about the mechanical properties of the patient’s tissue. Experimental results demonstrate that the effectiveness of direct and graphical force feedback depend on the nature of the surgical task and the experience level of the surgeon.
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Effects of haptic and graphical force feedback on teleoperated palpation
2009 IEEE International Conference on Robotics and Automation, 2009Co-Authors: John C. Gwilliam, Balazs Vagvolgyi, Alexander Vacharat, David D. Yuh, Mohsen Mahvash, Allison M. OkamuraAbstract:Direct haptic feedback and graphical force feedback have both been hypothesized to improve the performance of robot-assisted surgery. In this study we evaluate the benefits of haptic and graphical force feedback on surgeon performance and tissue exploration behavior during a teleoperated palpation task of artificial tissues. Seven surgeon subjects (four experienced in robot-assisted surgery) used a 7-degree-of-freedom teleoperated surgical robot to identify a comparatively rigid rigid target object (representing a calcified artery) in phantom heart models using the following feedback conditions: (1) direct haptic and graphical feedback, (2) direct haptic only, (3) graphical feedback only, and (4) no feedback. To avoid the problems of force sensing in a minimally invasive surgical environment, we use a position-exchange controller with dynamics compensation for direct haptic feedback and a force estimator displayed via tool-tip tracking bar graph for graphical force feedback. Although the transparency of the system is limited with this approach, results show that direct haptic force feedback minimizes applied forces to the tissue, while coupled haptic and graphical force feedback minimizes subject task error. For experienced surgeons, haptic force feedback substantially reduced task error independent of graphical feedback.
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ICRA - Effects of haptic and graphical force feedback on teleoperated palpation
2009 IEEE International Conference on Robotics and Automation, 2009Co-Authors: John C. Gwilliam, Balazs Vagvolgyi, Alexander Vacharat, David D. Yuh, Mohsen Mahvash, Allison M. OkamuraAbstract:Direct haptic feedback and graphical force feedback have both been hypothesized to improve the performance of robot-assisted surgery. In this study we evaluate the benefits of haptic and graphical force feedback on surgeon performance and tissue exploration behavior during a teleoperated palpation task of artificial tissues. Seven surgeon subjects (four experienced in robot-assisted surgery) used a 7-degree-of-freedom teleoperated surgical robot to identify a comparatively rigid rigid target object (representing a calcified artery) in phantom heart models using the following feedback conditions: (1) direct haptic and graphical feedback, (2) direct haptic only, (3) graphical feedback only, and (4) no feedback. To avoid the problems of force sensing in a minimally invasive surgical environment, we use a position-exchange controller with dynamics compensation for direct haptic feedback and a force estimator displayed via tool-tip tracking bar graph for graphical force feedback. Although the transparency of the system is limited with this approach, results show that direct haptic force feedback minimizes applied forces to the tissue, while coupled haptic and graphical force feedback minimizes subject task error. For experienced surgeons, haptic force feedback substantially reduced task error independent of graphical feedback.
Strahinja Dosen - One of the best experts on this subject based on the ideXlab platform.
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Myocontrol is closed-loop control: incidental feedback is sufficient for scaling the prosthesis force in routine grasping
Journal of NeuroEngineering and Rehabilitation, 2018Co-Authors: Marko Markovic, Dario Farina, Meike A Schweisfurth, Leonard F Engels, Strahinja DosenAbstract:Background Sensory feedback is critical for grasping in able-bodied subjects. Consequently, closing the loop in upper-limb prosthetics by providing artificial sensory feedback to the amputee is expected to improve the prosthesis utility. Nevertheless, even though amputees rate the prospect of sensory feedback high, its benefits in daily life are still very much debated. We argue that in order to measure the potential functional benefit of artificial sensory feedback, the baseline open-loop performance needs to be established. Methods The myoelectric control of naïve able-bodied subjects was evaluated during modulation of electromyographic signals ( EMG task ), and grasping with a prosthesis ( Prosthesis task ). The subjects needed to activate the wrist flexor muscles and close the prosthesis to reach a randomly selected target level (routine grasping). To assess the baseline performance, the tasks were performed with a different extent of implicit feedback (proprioception, prosthesis motion and sound). Finally, the prosthesis task was repeated with explicit visual force feedback. The subjects’ ability to scale the prosthesis command/force was assessed by testing for a statistically significant increase in the median of the generated commands/forces between neighboring levels. The quality of control was evaluated by computing the median absolute error (MAE) with respect to the target. Results The subjects could successfully scale their motor commands and generated prosthesis forces across target levels in all tasks, even with the least amount of implicit feedback (only muscle proprioception, EMG task). In addition, the deviation of the generated commands/forces from the target levels decreased with additional feedback. However, the increase in implicit feedback, from proprioception to prosthesis motion and sound, seemed to have a more substantial effect than the final introduction of explicit feedback. Explicit feedback improved the performance mainly at the higher target-force levels. Conclusions The study establishes the baseline performance of myoelectric control and prosthesis grasping force. The results demonstrate that even without additional feedback, naïve subjects can effectively modulate force with good accuracy with respect to that achieved when increasing the amount of feedback information.
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myocontrol is closed loop control incidental feedback is sufficient for scaling the prosthesis force in routine grasping
Journal of Neuroengineering and Rehabilitation, 2018Co-Authors: Marko Markovic, Strahinja Dosen, Dario Farina, Meike A Schweisfurth, Leonard F EngelsAbstract:Sensory feedback is critical for grasping in able-bodied subjects. Consequently, closing the loop in upper-limb prosthetics by providing artificial sensory feedback to the amputee is expected to improve the prosthesis utility. Nevertheless, even though amputees rate the prospect of sensory feedback high, its benefits in daily life are still very much debated. We argue that in order to measure the potential functional benefit of artificial sensory feedback, the baseline open-loop performance needs to be established. The myoelectric control of naive able-bodied subjects was evaluated during modulation of electromyographic signals (EMG task), and grasping with a prosthesis (Prosthesis task). The subjects needed to activate the wrist flexor muscles and close the prosthesis to reach a randomly selected target level (routine grasping). To assess the baseline performance, the tasks were performed with a different extent of implicit feedback (proprioception, prosthesis motion and sound). Finally, the prosthesis task was repeated with explicit visual force feedback. The subjects’ ability to scale the prosthesis command/force was assessed by testing for a statistically significant increase in the median of the generated commands/forces between neighboring levels. The quality of control was evaluated by computing the median absolute error (MAE) with respect to the target. The subjects could successfully scale their motor commands and generated prosthesis forces across target levels in all tasks, even with the least amount of implicit feedback (only muscle proprioception, EMG task). In addition, the deviation of the generated commands/forces from the target levels decreased with additional feedback. However, the increase in implicit feedback, from proprioception to prosthesis motion and sound, seemed to have a more substantial effect than the final introduction of explicit feedback. Explicit feedback improved the performance mainly at the higher target-force levels. The study establishes the baseline performance of myoelectric control and prosthesis grasping force. The results demonstrate that even without additional feedback, naive subjects can effectively modulate force with good accuracy with respect to that achieved when increasing the amount of feedback information.
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Tactile feedback is an effective instrument for the training of grasping with a prosthesis at low- and medium-force levels
Experimental Brain Research, 2017Co-Authors: A. M. De Nunzio, Sabrina Lemling, Nan Ge, Meike Annika Schweisfurth, Strahinja Dosen, Bernhard Graimann, Deborah Falla, Milica Markovic, Dario FarinaAbstract:Grasping is a complex task routinely performed in an anticipatory (feedforward) manner, where sensory feedback is responsible for learning and updating the internal model of grasp dynamics. This study aims at evaluating whether providing a proportional tactile force feedback during the myoelectric control of a prosthesis facilitates learning a stable internal model of the prosthesis force control. Ten able-bodied subjects controlled a sensorized myoelectric prosthesis performing four blocks of consecutive grasps at three levels of target force (30, 50, and 70%), repeatedly closing the fully opened hand. In the first and third block, the subjects received tactile and visual feedback, respectively, while during the second and fourth block, the feedback was removed. The subjects also performed an additional block with no feedback 1 day after the training (Retest). The median and interquartile range of the generated forces was computed to assess the accuracy and precision of force control. The results demonstrated that the feedback was indeed an effective instrument for the training of prosthesis control. After the training, the subjects were still able to accurately generate the desired force for the low and medium target (30 and 50% of maximum force available in a prosthesis), despite the feedback being removed within the session and during the retest (low target force). However, the training was substantially less successful for high forces (70% of prosthesis maximum force), where subjects exhibited a substantial loss of accuracy as soon as the feedback was removed. The precision of control decreased with higher forces and it was consistent across conditions, determined by an intrinsic variability of repeated myoelectric grasping. This study demonstrated that the subject could rely on the tactile feedback to adjust the motor command to the prosthesis across trials. The subjects adjusted the mean level of muscle activation (accuracy), whereas the precision could not be modulated as it depends on the intrinsic myoelectric variability. They were also able to maintain the feedforward command even after the feedback was removed, demonstrating thereby a stable learning, but the retention depended on the level of the target force. This is an important insight into the role of feedback as an instrument for learning of anticipatory prosthesis force control.