A Coupling Dynamic Model for Studying the Physical Interaction Between a Finger Exoskeleton and a Human Finger

This paper presents a coupling dynamic model that is based on a spring-damping contact for modeling and analyzing the physical interaction between the soft exoskeleton and the finger. The physiological structure and biomechanical model of the finger were introduced. According to the movement mechanism of the finger, a bionic prototype of the single-finger model, which is driven by shape memory alloy (SMA) wire, was designed, and its mechanical model was established. A spring-damping model was used to expound an interaction force of a human-robot with a coupling dynamic model. The experiment was carried out to verify the exoskeleton mechanical model and determine the bending angle trajectory of each joint. The inverse solution of the coupling dynamic model was verified by using angle data and driving parameters as input. According to the torque relationship, the actual active shrinkage torque of SMA wire was compared with the simulation data for the circumstances with or without consideration of the interaction contact force. The results confirm that the actual values are consistent with the simulation values. After comparing the actual active shrinkage torque and simulation curve without considering the interaction contact force, the error range is between 0 and $19.57~\text {N}\cdot \text {mm}$ . The comparison that considers the interaction contact force model yields an error range between -0.74 and $10.89~\text {N}\cdot \text {mm}$ . The accuracy of the model is increased by an average of 7.05%.