Soft Pneumatic Actuator Inspired on Flexion-Extension Motion Trajectory of the Human Fingers

Soft robotics has been widely explored in recent years, medical engineering is one of the sciences that has taken the most advantages of this technology. The use of unconventional materials has allowed the development of highly flexible and mechanically adaptable medical devices. This paper presents the design of a soft bending actuator based on the flexion-extension motion trajectory of the human fingers. Moreover, we present the kinematic model of the actuator by the parametrization of the Denavit-Hartenberg convention and using the Euler-Bernoulli principle. The design of the actuator was based on the flexion-extension motion trajectory of fingers of an average Mexican hand, the geometry is based on chambers allowing bending motion. On the other hand, we introduce a new method to decrease the number of steps in the casting technique, we propose to use water-soluble material to create the internal geometry of the actuator, thus avoiding a subsequent assembly process, and furthermore, avoiding the misalignment that can occur in the parts that are joined during assembly. Finally, the experimental evaluation of the actuator by using machine vision is presented, the results are compared with the numerical evaluation of the kinematic model and the flexion-extension trajectory fingers.