Haptic augmented reality: Taxonomy and an example of stiffness modulation
Presence: Teleoperators and Virtual Environments
SqueezeBlock: using virtual springs in mobile devices for eyes-free interaction
UIST '10 Proceedings of the 23nd annual ACM symposium on User interface software and technology
Real stiffness augmentation for haptic augmented reality
Presence: Teleoperators and Virtual Environments
Discrimination of springs with vision, proprioception, and artificial skin stretch cues
EuroHaptics'12 Proceedings of the 2012 international conference on Haptics: perception, devices, mobility, and communication - Volume Part I
ACM Transactions on Applied Perception (TAP) - Special issue SAP 2013
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This study compares the Weber fraction for human perception of stiffness among three conditions: vision, proprioceptive motion feedback, and their combination. To make comparisons between these feedback conditions, a novel haptic device was designed that senses the spring behavior through encoder and force measurements, and implements a controller to render linear virtual springs so that the stimuli displayed haptically could be compared with their visual counterparts. The custom-designed, torque-controlled haptic interface non-invasively controls the availability of proprioceptive motion feedback in unimpaired individuals using a virtual environment. When proprioception is available, the user feels an MCP joint rotation that is proportional to his or her finger force. When proprioception is not available, the actual finger is not allowed to move, but a virtual finger displayed graphically moves in proportion to the user's applied force. Visual feedback is provided and removed by turning on and off this graphical display. Weber fractions were generated from an experiment in which users examined pairs of springs and attempted to identify the spring with higher stiffness. To account for slight trial-to-trial variations in the relationship between force and position in the proprioceptive feedback conditions, our analysis uses measurements of the actual rendered stiffness, rather than the commanded stiffness. Results for 10 users give average Weber fractions of 0.056 for vision, 0.036 for proprioception, and 0.039 for their combination, indicating that proprioception is important for stiffness perception for this experimental setup. The long-term goal of this research is to motivate and develop methods for proprioception feedback to wearers of dexterous upper-limb prostheses.