Robot-assisted assessment of vibration perception and localization on the hand

Identification of Vibrotactile Patterns Encoding Obstacle Distance Information

Delivering distance information of nearby obstacles from sensors embedded in a white cane-in addition to the intrinsic mechanical feedback from the cane-can aid the visually impaired in ambulating independently. Haptics is a common modality for conveying such information to cane users, typically in the form of vibrotactile signals. In this context, we investigated the effect of tactile rendering methods, tactile feedback configurations and directions of tactile flow on the identification of obstacle distance. Three tactile rendering methods with temporal variation only, spatio-temporal variation and spatial/temporal/intensity variation were investigated for two vibration feedback configurations. Results showed a significant interaction between tactile rendering method and feedback configuration. Spatio-temporal variation generally resulted in high correct identification rates for both feedback configurations. In the case of the four-finger vibration, tactile rendering with spatial/temporal/intensity variation also resulted in high distance identification rate. Further, participants expressed their preference for the four-finger vibration over the single-finger vibration in a survey. Both preferred rendering methods with spatio-temporal variation and spatial/temporal/intensity variation for the four-finger vibration could convey obstacle distance information with low workload. Overall, the presented findings provide valuable insights and guidance for the design of haptic displays for electronic travel aids for the visually impaired.

Neurocognitive robot-assisted therapy of hand function

Neurocognitive therapy, according to the Perfetti method, proposes exercises that challenge motor, sensory as well as cognitive functions of neurologically impaired patients. At the level of the hand, neurocognitive exercises typically involve haptic exploration and interaction with objects of various shapes and mechanical properties. Haptic devices are thus an ideal support to provide neurocognitive exercises under well-controlled and reproducible conditions, and to objectively assess patient performance. Here we present three neurocognitive robot-assisted exercises which were implemented on the ReHapticKnob, a high-fidelity two-degrees-of-freedom hand rehabilitation robot. The exercises were evaluated for feasibility and acceptance in a pilot study on five patients suffering from different neurological disorders. Results showed that all patients were able to take part in the neurocognitive robot-assisted therapy, and that the proposed therapy was well accepted by patients, as assessed through subjective questionnaires. Force/torque and position measurements provided insights on the motor strategy employed by the patients during the exploration of virtual object properties, and served as objective assessment of task performance. The fusion of the neurocognitive therapy concept with robot-assisted rehabilitation enriches therapeutic approaches through the focus on haptics, and could provide novel insights on sensorimotor impairment and recovery.