Design of a Twisted-String Actuator for Haptic Force Rendering

In this paper, the design of a Twisted-String Actuation (TSA) module suitable for a wide set of robotic applications is presented. The TSA module is characterized by an integrated force sensor based on optoelectronic components and embedded controller with power electronics. The proposed actuation system is particularly suited for very compact, light-weight, wearable and low cost robotic devices, such as haptic devices, wearable systems and rehabilitation exoskeletons. The whole module design and the basic force sensor working principle are illustrated and discussed. Particular attention is given to the integration of the force sensor into the TSA module to solve the drawbacks of previous solutions. Moreover, the structure of the TSA module electronics and embedded controller is presented. Finally, the actuation module has been experimentally tested, and the ability of the system of controlling the actuation force has been demonstrated.