A Study on Rehabilitation Using a Tactile-Force Presentation System

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In the present study, we are attempting to develop a compound display to represent pressure and force via two fingers and the robotic hand in order to provide adequate stimuli to handicapped individuals in order to facilitate recovery of dexterity skills. The compound display comprises an apparatus to be manipulated by one hand, which is called the "master hand". The master hand is equipped with two tactile displays and an articulated manipulator functioning as the force display. There is one tactile display for the index finger and one for the thumb. Each tactile display has a 6-by-4 array of stimulus pins which contacts each finger pad. An operator manipulates the master hand to feel virtual tactile sensation. A virtual object can be handled and moved in two dimensions via the tactile and position feedback delivered through the master hand. To evaluate the display's representational capability, we performed two series of experiments. In Experiment A, human subjects grasped virtual pe … More gs and attempted to judge their diameters. In Experiment B, the human subjects tried to insert various pegs into a hole. In Experiment A, we evaluated the representational capability of the display on the basis of how precisely the peg's diameter can be judged. The results of Experiment A show that the ability to accurately identify grasped-object size is greater when the subject receives both tactile and force feedback. In a "pick up and place" task a human operator grasps objects many times, and so identification accuracy is important for successful completion of such a task. In Experiment B, the subject attempts to insert a virtual peg into a different size hole. As the diameter of the hole increases, the range of angles at which a peg can be successfully inserted decreases. Final attitudes of pressure-force and force-only representations are-0.3 and 2.5°, respectively. A second finding was that when the peg was only slightly smaller in diameter than the hole, the operator sometimes was unable to find the hole, or sank the peg into the wall of the hole. We were able to measure the amount by which the peg penetrated the hole wall. Our compound presentation is effective at enhancing the realism of grasped objects if pressure and force are both represented. The quality of virtual reality could be further improved by means of representing rotational force caused in the process of inserting the virtual peg, which we are currently working to develop. We could not perform a field test with handicapped patients due to unresolved safety issues of the present display, but we anticipate being able to perform such field tests in the near future after meeting the necessary safety requirements. Less