Integral line-of-sight for path following of underwater snake robots

Abstract

Abstract-This paper considers straight line path following control of underwater snake robots in the presence of constant irrotational currents. An integral line-of-sight (LOS) guidance law is proposed, which is combined with a sinusoidal gait pattern and a directional controller that steers the robot towards and along the desired path. Integral action is introduced in the guidance law to compensate for the ocean current effect. The stability of the proposed control scheme in the presence of ocean currents is investigated. In particular, using Poincaré map analysis, we prove that the state variables of an underwater snake robot trace out an exponentially stable periodic orbit when the integral LOS path following controller is applied. Simulation results are presented to illustrate the performance of the proposed path following controller for both lateral undulation and eel-like motion.

Multi-objective optimization for efficient motion of underwater snake robots

“…where the detailed derivation of the matrix M p and vectors V a x , V a y , k 11 , k 12 , k 21 and k 22 is given in [11,12]. In addition, it is shown that under the influence of fluid forces (2) and torques (3), the complete equation of motion of the underwater snake robot are obtained by (4) and…”

“…In order to plot the Pareto frontier, one can find the solutions for different values of w p varying from 0 to 1 (and w υ changing from 1 to 0) using a small step size ∆ w p . Therefore, the optimization problem (11) can be transformed to a new optimization problem by replacing the objective function J opt to J bal in (12). In order to find the solution of the new optimization problem for specific weighting factors, an optimization algorithm is required.…”

“…In [11,12], the authors propose a model of underwater snake robots, where the dynamic equations are written in closed form. Compared to the models in [1,4,21,24,27,30] it is an advantage from an analysis point of view that the model is in closed form, as opposed to including numerical evaluations of the drag effects.…”

“…In this paper, based on the dynamic model presented in [11,12], a multi-objective optimization problem is developed with the aim of maximizing the achieved forward velocity of the robot and minimizing the corresponding average power consumption of the system. Results are obtained for the two most common swimming patterns for underwater snake robot locomotion: lateral undulation and eel-like motion patterns.…”

“…In addition, it is beneficial that it includes both resistive and reactive fluid forces, since swimming snake robots operate at Reynolds numbers that require both these effects to be taken into account. In particular, the modeling approach presented in [11,12] takes into account both the linear and the nonlinear drag forces (resistive fluid forces), the added mass effect (reactive fluid forces), the fluid moments and current effects. This model will thus be used in the optimization.…”