Model-Free Adaptive Control for Tendon-Driven Continuum Robots

Continuum robots have been increasingly employed in various fields, such as minimally invasive surgery, aerospace, and nuclear industry, due to their high flexibility. A model-free adaptive control-based position control method for continuum robots is proposed in this paper to improve their tracking accuracy in constrained environments. First, the kinematic model-based control method of continuum robots, and effects of the modeling error on the distal positioning accuracy were studied and analyzed. Next, the pseudo-Jacobian matrix of the continuum robot was estimated in real time according to its control input and distal position output signals to reduce external disturbances, such as hysteresis, modeling error, and other interferences. Finally, experiments on the developed continuum robot platform were conducted, and the tracking error for two different trajectories was analyzed in the free space. The comparison between the proposed method and the model-based feedback method indicated that this method had better precision and anti-interference ability. The results showed that the root mean squared error(RMSE)of the continuum robot along the circular and triangular trajectories were 2.31mm and 2.448mm, respectively, indicating the excellent control accuracy of the proposed method and a stable root mean square error value during the tracking movement. The RMSE of the proposed method increases with the expansion of the motion range and remains stable within an acceptable error range. The proposed method considerably resisted external disturbances and improved the accuracy of the control of continuum robots. © 2022, Editorial Board of Journal of Tianjin University(Science and Technology). All right reserved.