Physics-Based Kinematic Modeling of a Twisted String Actuator-Driven Soft Robotic Manipulator

Due to their high tendon-based (muscle-like) linear actuation, large force generation, and good operational bandwidth, twisted string actuators (TSAs) are strongly suited to actuate robotic devices. TSAs have been widely employed in numerous robotic applications; however, their inclusion in soft robots has been limited. This paper presents the modeling of the one-degree-of-freedom kinematics of a soft robotic manipulator driven by TSAs. The manipulator consists of soft silicone that bends in different directions due to the contraction of three TSAs. A physics-based model was developed to predict the bending angle of the soft manipulator. Furthermore, the bending velocity of the soft manipulator was modeled by using the equations derived from the bending angle model. The proposed modeling approaches were experimentally verified to be effective. For example, the proposed model predicted bending angle and bending velocity with mean errors of 1.58 degrees (2.63 %) and 0.405 degrees/sec (4.31%), respectively.