Adaptive Approximation Tracking Control of a Continuum Robot With Uncertainty Disturbances

Continuum robot has certain compliance and intrinsic safety, which makes it an excellent substitute for the traditional rigid robot in the various tasks, such as human-robot interaction or medical surgery. However, due to the complex nonlinearities which are induced by the compliance, parameter uncertainties, and unknown disturbances, good performance control scheme for the continuum robot is always a challenging task for the practical applications. Thus, to overcome this challenge of the uncertain dynamics and unknown external disturbances, this article develops a novel adaptive control scheme for a continuum robot using the function approximation technique (FAT). Specifically, for the proposed continuum robot, an adaptive FAT control (AFATC) strategy with no update laws is proposed to handle the uncertain parameters of the robot dynamics and external disturbances. The control law is expressed as a finite linear combination of the orthogonal basis functions by the FAT. The proposed AFATC scheme uses a fixed control structure, and the weight matrices are not updated in time. Then, the stability of the proposed controller is proved based on the Lyapunov function. Afterwards, the simulation results indicate the proposed AFATC scheme has good control performance compared with the regressor-free adaptive control (RFAC) method. Finally, the effectiveness of the proposed AFATC scheme is demonstrated in a group of real-time experiments.