Finite-time tracking control for a variable stiffness pneumatic soft bionic caudal fin

This paper introduces a finite-time tracking control method for a pneumatic soft bionic caudal fin with driving fins and variable stiffness fins. Designs, fabrications and kinematic modelling are shown for the pneumatic soft bionic caudal fin. Based on a kinematic model, a dynamic nonlinear system is established for the driving fins in the pneumatic soft bionic caudal fin. A nonlinear error feedback controller is designed for the pneumatic soft bionic caudal fin via an extended state observer based on a second-order finite-time tracking differentiator. Finite-time convergence of tracking error is proved by Lyapunov approach for the dynamic nonlinear system. Finally, experimental and simulation results are shown to verify the effectiveness for the design of the pneumatic soft bionic caudal fin and the proposed control method of the dynamic nonlinear system, respectively.