Bidirectional position and stiffness control of twisted string actuators

Abstract

This thesis covers the modeling and analysis of the dynamic relationship between the link space and the motor space of the twisted string actuator system and its control methodology by breaking away from the conventional kinematics model and employing the static model. The static model allows it possible to analyze which procedure between the motor and link space propagates the torque of motor to tension in the link space through the twisted string actuator which cannot be explained in the kinematic model. Then, we design the dynamic model of twisted string actuator system using force components derived from static model and propose design methodology of dynamic based adaptive tension controller. The twisted string actuator also has variable stiffness property depending on the state of the motor and link. Then, we analyze the variable stiffness property. And based on its results, we propose the design methodology of bidirectional position and stiffness controller.