An instance of tactile suppression: Active exploration impairs tactile sensitivity for the direction of lateral movement

The phenomenon of a reduction in tactile sensitivity during voluntarily executed body movement we call “tactile suppression”. This is in analogy to saccadic suppression where the visual sensitivity is reduced during voluntarily executed eye movements [1]. Here we investigate tactile suppression using an integrated tactile/kinesthetic display – consisting of a tactile shear force device [2] mounted on a hyper redundant haptic display (ViSHaRD10 [3]). To quantify the tactile suppression effect we measured subject’s motion-direction discrimination performance for tactile stimuli moving laterally on the index finger under various active and passive exploration conditions. In the baseline condition (“static”) only tactile stimuli were provided using the shear-force device while the arm was held still. In the “active” condition subjects had to discriminate the direction of tactile motion while actively executing arm movements at the same time. Finally, in the “passive” condition the kinesthetic device passively moved the subjects’ arm, while the subject was performing the discrimination task. Compared to the “still” condition results indicate a significant decrease of tactile sensibility during active movements whereas passive movements seem to have a minor effect on tactile discrimination performance

Experimental Evaluation of a Haptic Interface for Endoscopic Simulation

The main goal of virtual reality based surgery simulators with haptic feedback is to provide an alternative to traditional training methods on animals, cadavers or real patients. Haptic feedback is a key feature for every surgery simulator for the training of hand-eye coordination. To address the need for higher fidelity and complexity in an endoscopic simulator, we have designed a new haptic interface, instrumented a clinical endoscope and integrated it with a software simulation for colonoscopy. The proposed haptic interface provides high translational force and rotational torque with combined electrical motors and passive brakes. This paper presents the evaluation of the haptic interface. Experimental analyzes are performed for characterization and performance evaluation. A model-based feed-forward control is implemented and the results show that the control successfully compensates for the device dynamics and nonlinearities such as Coulomb and viscous friction

Docking Haptics: Extending the Reach of Haptics by Dynamic Combinations of Grounded and Worn Devices

Grounded haptic devices can provide a variety of forces but have limited working volumes. Wearable haptic devices operate over a large volume but are relatively restricted in the types of stimuli they can generate. We propose the concept of docking haptics, in which different types of haptic devices are dynamically docked at run time. This creates a hybrid system, where the potential feedback depends on the user's location. We show a prototype docking haptic workspace, combining a grounded six degree-of-freedom force feedback arm with a hand exoskeleton. We are able to create the sensation of weight on the hand when it is within reach of the grounded device, but away from the grounded device, hand-referenced force feedback is still available. A user study demonstrates that users can successfully discriminate weight when using docking haptics, but not with the exoskeleton alone. Such hybrid systems would be able to change configuration further, for example docking two grounded devices to a hand in order to deliver twice the force, or extend the working volume. We suggest that the docking haptics concept can thus extend the practical utility of haptics in user interfaces

Doctor of Philosophy

dissertationMost humans have difficulty performing precision tasks, such as writing and painting, without additional physical support(s) to help steady or offload their arm's weight. To alleviate this problem, various passive and active devices have been developed. However, such devices often have a small workspace and lack scalable gravity compensation throughout the workspace and/or diversity in their applications. This dissertation describes the development of a Spatial Active Handrest (SAHR), a large-workspace manipulation aid, to offload the weight of the user's arm and increase user's accuracy over a large three-dimensional workspace. This device has four degrees-of-freedom and allows the user to perform dexterous tasks within a large workspace that matches the workspace of a human arm when performing daily tasks. Users can move this device to a desired position and orientation using force or position inputs, or a combination of both. The SAHR converts the given input(s) to desired velocit