Modeling and position control of a high performance twisted-coiled polymer actuator

This paper presents the property characterization, modeling and position control of a hybrid twisted-coiled polymer actuator made from Spandex and nylon fibers. The actuator is low-cost, easy to fabricate and light-weight. Moreover, it can generate large displacement and provide Joule heating capability. Based on the energy method and experimental observations, a nonlinear dynamic model is developed to estimate the displacement of the actuator. The model is then utilized in a finite time controller, which guarantees the robustness of the actuator over model variations and external disturbances. The controlled system is proved to be stable using Lyapunov stability theory and verified through experiments. Experimental results show good control performance with highest position error of 0.25mm and root-mean squared error of 0.11 mm at steady state, nearly 2 times smaller compared with those of a computed-torque method controller.