Haptic Guidance Needs to Be Intuitive Not Just Informative to Improve Human Motor Accuracy (original) (raw)
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On the Efficacy of Haptic Guidance Schemes for Human Motor Learning
2009
This article investigates the efficacy of different haptic guidance schemes on human motor learning. In particular, the performances of four training protocols, virtual practice, virtual fixtures, fixed-gain error-reducing shared control, and progressive error-reducing shared control, are compared. The experimental results indicate that, if not designed carefully, haptic guidance protocols may be detrimental on motor learning, since such schemes actively interfere with the coupled system dynamics and cause participants to experience task dynamics that are altered from those of the real task. Results also show that the amount of assistance is an important factor, and fixed-gain assistance schemes may cause subjects to gain dependence on the existence of the guidance. Adjusting the amount of haptic guidance based on performance, utilizing progressive gains, is shown to increase the training effectiveness when compared to fixed gain controllers. Key parameters that influence the principles of motor learning in healthy human subjects may guide the design of more effective rehabilitation training protocols.
Haptic Feedback Enhances Force Skill Learning
Second Joint EuroHaptics Conference and Symposium on Haptic Interfaces for Virtual Environment and Teleoperator Systems (WHC'07), 2007
This paper explores the use of haptic feedback to teach an abstract motor skill that requires recalling a sequence of forces. Participants are guided along a trajectory and are asked to learn a sequence of onedimensional forces via three paradigms: haptic training, visual training, or combined visuohaptic training. The extent of learning is measured by accuracy of force recall. We find that recall following visuohaptic training is significantly more accurate than recall following visual or haptic training alone, although haptic training alone is inferior to visual training alone. This suggests that in conjunction with visual feedback, haptic training may be an effective tool for teaching sensorimotor skills that have a forcesensitive component to them, such as surgery. We also present a dynamic programming paradigm to align and compare spatiotemporal haptic trajectories.
Misjudgment of direction contributes to curvature in movements toward haptically defined targets
Journal of Experimental Psychology: Human Perception and Performance, 2014
The trajectories of arm movements toward visually defined targets are curved, even if participants try to move in a straight line. A factor contributing to this curvature may be that participants systematically misjudge the direction to the target, and try to achieve a straight path by always moving in the perceived direction of the target. If so, the relation between perception of direction and initial movement direction should not only be present for movements toward visually defined targets, but also when making movements toward haptically defined targets. To test whether this is so, we compared errors in the initial movement direction when moving as straight as possible toward haptically defined targets with errors in a pointer setting task toward the same targets. We found a modest correlation between perception of direction and initial movement direction for movements toward haptically defined targets. The amount of correlation depended on the geometry of the task.
IEEE Transactions on Human-Machine Systems, 2016
When subjects reach for a visual target with their unseen hand, they make systematic errors (visuo-haptic matching errors). Visuohaptic matching errors are idiosyncratic and consistent over time. Therefore, it might be useful to compensate for these subject-specific matching errors in the design of haptic guidance to make the guidance perceptually consistent with the visual information. In this study, we investigated whether compensating for visuo-haptic matching errors results in better perceptual consistency in a reaching task. Subjects (N = 12) had to reach for visual targets with the handle of a haptic device (PHANToM Premium 3.0/6DoF) held in their unseen dominant hand without guidance, with haptic guidance toward the target position, or with haptic guidance toward the position they would reach for according to their idiosyncratic visuo-haptic matching error. We found that the distance between the aiming point of the guidance and the reached end position was smaller for the guidance toward the idiosyncratic matched positions, suggesting a larger perceptual consistency. Adjusting for idiosyncratic visuo-haptic matching errors seems to have benefits over guidance to the visual target position.
Effect of visual and haptic feedback on grasping movements.
Perceptual estimates of three-dimensional (3D) properties, such as the distance and depth of an object, are often inaccurate. Given the accuracy and ease with which we pick up objects, it may be expected that perceptual distortions do not affect how the brain processes 3D information for reach-to-grasp movements. Nonetheless, empirical results show that grasping accuracy is reduced when visual feedback of the hand is removed. Here we studied whether specific types of training could correct grasping behavior to perform adequately even when any form of feedback is absent. Using a block design paradigm, we recorded the movement kinematics of subjects grasping virtual objects located at different distances in the absence of visual feedback of the hand and haptic feedback of the object, before and after different training blocks with different feedback combinations (vision of the thumb and vision of thumb and index finger, with and without tactile feedback of the object). In the Pretraining block, we found systematic biases of the terminal hand position, the final grip aperture, and the maximum grip aperture like those reported in perceptual tasks. Importantly, the distance at which the object was presented modulated all these biases. In the Posttraining blocks only the hand position was partially adjusted, but final and maximum grip apertures remained unchanged. These findings show that when visual and haptic feedback are absent systematic distortions of 3D estimates affect reach-to-grasp movements in the same way as they affect perceptual estimates. Most importantly, accuracy cannot be learned, even after extensive training with feedback.
Journal of neuroengineering and rehabilitation, 2006
Mechanical guidance with a robotic device is a candidate technique for teaching people desired movement patterns during motor rehabilitation, surgery, and sports training, but it is unclear how effective this approach is as compared to visual demonstration alone. Further, little is known about motor learning and retention involved with either robot-mediated mechanical guidance or visual demonstration alone. Healthy subjects (n = 20) attempted to reproduce a novel three-dimensional path after practicing it with mechanical guidance from a robot. Subjects viewed their arm as the robot guided it, so this "haptic guidance" training condition provided both somatosensory and visual input. Learning was compared to reproducing the movement following only visual observation of the robot moving along the path, with the hand in the lap (the "visual demonstration" training condition). Retention was assessed periodically by instructing the subjects to reproduce the path withou...
Haptic Feedback and Human Performance in a Dynamic Task
2002
This study explores the effects of haptic feedback on performance and learning by human subjects executing a dynamic task. We present the results of experiments involving the control of a ball and beam. Human subjects perform position targeting of the ball through hand operation of the beam angle. In our dynamic analysis we discuss how this prototype task may be used to test the efficacy of various haptic feedback conditions. We obtain results for two conditions of haptic feedback, produced using two ball sizes, and apply various metrics to analyze performance. We also examine ordering effects that occur in the presentation of these haptic conditions. Our analysis and experimental findings indicate that the performance of a dynamic task is governed by the complexity of system dynamics and the magnitude of haptic feedback. Our results provide modest support to recommend exposure to a more complex, higher force-feedback task prior to the execution of a simpler lower feedback task.
A brief glimpse at a haptic target is sufficient for multisensory integration in reaching movements
2021
Goal-directed aiming movements toward visuo-haptic targets (i.e., seen and handheld targets) are generally more precise than those toward visual only or haptic only targets. This multisensory advantage stems from a continuous inflow of haptic and visual target information during the movement planning and execution phases. However, in everyday life, multisensory movements often occur without the support of continuous visual in- formation. Here we investigated whether and to what extent limiting visual information to the initial stage of the action still leads to a multisensory advantage. Participants were asked to reach a handheld target while vision was briefly provided during the movement planning phase (50 ms, 100 ms, 200 ms of vision before movement onset), or during the planning and early execution phases (400 ms of vision), or during the entire movement. Additional conditions were performed in which only haptic target information was provided, or, only vision was provided either briefly (50 ms, 100 ms, 200 ms, 400 ms) or throughout the entire movement. Results showed that 50 ms of vision before movement onset were sufficient to trigger a direction-specific visuo-haptic integration process that increased endpoint precision. We conclude that, when a continuous support of vision is not available, endpoint precision is determined by the less recent, but most reliable multisensory information rather than by the latest unisensory (haptic) inputs.
Correcting for Visuo-Haptic Biases in 3D Haptic Guidance
PloS one, 2016
Visuo-haptic biases are observed when bringing your unseen hand to a visual target. The biases are different between, but consistent within participants. We investigated the usefulness of adjusting haptic guidance to these user-specific biases in aligning haptic and visual perception. By adjusting haptic guidance according to the biases, we aimed to reduce the conflict between the modalities. We first measured the biases using an adaptive procedure. Next, we measured performance in a pointing task using three conditions: 1) visual images that were adjusted to user-specific biases, without haptic guidance, 2) veridical visual images combined with haptic guidance, and 3) shifted visual images combined with haptic guidance. Adding haptic guidance increased precision. Combining haptic guidance with user-specific visual information yielded the highest accuracy and the lowest level of conflict with the guidance at the end point. These results show the potential of correcting for user-spec...