Mechanical modeling of a ring-type fingertip force sensor

In this paper, focusing on the relationship between tendon tension and force applied to the fingertip, we develop a ring-type sensor that estimate fingertip force from tendon tension. To establish the measurement principle, mechanical models were constructed in three steps for sensor structure, deformation of finger and sensor, and finger kinematics. By integrating those mechanical relationships, we derived a relation expression between ring-type sensor output and fingertip force. In addition, we conducted experiments in which the developed ring-type fingertip force sensor was attached to the index finger and force was applied to the fingertip. As the results, it was confirmed that the fingertip force could be estimated by using the derived relational expressions both when the finger was extended and when it was bent. The results showed the validity of the mechanical models and the effectiveness of the sensor. These results provide important insights that will be useful for future sensor design and applications.