Design and control of robotic joint module driven by twisted and coiled actuators

Lightweight robots have been studied widely due to their safety and friendly interaction properties. There are lots of cable driven robots which have been proposed which show good application potential on service robots. Cable driven robot can only transmit force by the cables and the force transmission has only one direction, which increases its mechanical design complexity. The twisted-and-coiled artificial (TCA) muscles possess unique contraction properties that have advantages for researchers seeking to simplify the development of robots. However, twisted-and-coiled artificial muscles are greatly affected by its external disturbance and produce process, which makes it difficult to be controlled. In this paper, a robotic joint with two-degree-of-freedom module weighing 85.8g is designed driven by twisted-and-coiled artificial muscles. A Linear Active Disturbance Rejection Control (LADRC) method has been proposed for the driven artificial muscles position control. The experimental device has been setup and the control effect has been studied. The experiment results show a good control effect. The position error is less than 2% and the step response is within 13 seconds. This study validated that the TCA has strong possibility used for lightweight robot joint under the designed LADRC control method.