Generation of Two-Dimensional Kinesthetic Illusion in Ankle Joint with Vibration Stimulation

The artificial sensation of walking can be applied to enhancing the self-efficacy and self-agency of persons whose motions are assisted by human assist-robots. When mechanical vibratory stimulation is applied to muscle tendons, a phenomenon called "Kinesthetic Illusion (KI)" is induced. The stimulated muscle feels as if it is being extended, even though it is not moving when KI is induced. If this phenomenon can be generated and controlled at the ankle joint, an artificial gait sensation can be generated. It is known that a variety of muscles such as Gastrocnemius (GA), Tibialis Anterior (TA), Peroneus Longus (PL), and Tibialis Posterior (TP) act on gait. Therefore, it would be possible to enhance gait sensation and generate two-dimensional gait sensations, such as in the sagittal and anterior forehead planes if KI is generated for those muscles. This paper investigates a basic study of KI characteristics in the two-dimensional direction at GA, TA, PL, and TP. The experiment results revealed the possibility of KI generation in the two-dimensional direction. Moreover, it is found that vibration stimulation at 30Hz-40Hz is adequate for generating KI in all muscles. The results of this study demonstrate the possibility of generating a two-dimensional gait sensation.