Abstract
The authors have developed a ring-type sensor system that focuses on the tension in the flexor tendons of the fingers in order to measure the force applied to the fingertips without interfering with the sensation at the fingertips. The flexor digitorum superficialis and flexor digitorum profundus are mainly involved in the flexion of the finger, and this sensor measures the combined force of the forces on each tendon. On the other hand, the mechanical model that represents the measurement principle of the sensor requires the tension applied to each tendon. In this study, we propose a method to measure the surface electromyogram during fingertip force generation in various finger postures, and to estimate the ratio of tension between the flexor digitorum superficialis and flexor digitorum profundus during fingertip force generation from the activity of each muscle. In order to determine this ratio, experiments were conducted to measure the relationship between joint angle and muscle activity. The results showed that the percentage of activity of the flexor digitorum profundus increased and the percentage of activity of the flexor digitorum superficialis decreased in the maximum voluntary muscle strength in proportion to the finger flexion angle.
