Accurate Dynamic Modeling of Twisted String Actuators Accounting for String Compliance and Friction

This letter presents derivation and experimental evaluation of extended dynamical model of twisted string actuator (TSA). The proposed model supports more precise estimation of required motor torque for both low-speed and high-speed (up to 2 Hz) motion by considering effects of elastic deformation of strings and frictional forces. Analysis of the experimental data demonstrated that the relative error between theoretical and practical curves never exceeded 7% for the whole range of tested motion frequencies, the accuracy that is impossible to achieve with state-of-art mathematical models. The proposed dynamical model can be used for accurate model-based control of the TSA-based systems and for efficient TSA motor selection.