Terminal Sliding Mode Control for speed tracking of a Carangiform robotic fish

Abstract

In this paper, we implement a novel discrete-time Terminal Sliding Mode Control (TSMC) for real-time precise speed control of a two-link Carangiform robotic fish. First, using Newton's laws of motion, combined with Lighthill's slender body theory, we develop a dynamical model to analyse the robotic fish motion. The model attained is highly non-linear and non-affine in control input which is why many control techniques may not be suitable for application. Moreover, exact model parameter values might not be available. Hence, we propose a discrete-time Terminal Sliding Mode Control technique which can handle most of the unprecedented factors in modelling while controlling the speed of the robot. Additionally, a disturbance observer is implemented to learn the low frequency un-modelled variations in the system. The developed control algorithm is examined in both simulations and experiments to illustrate its effective speed tracking performance of the robotic fish.