A control-oriented model of underwater snake robots exposed to currents

Abstract

Abstract-This paper presents a control-oriented model of a neutrally buoyant underwater snake robot that is exposed to a constant irrotational current. The robot is assumed to move in a horizontal, fully submerged plane with a sinusoidal gait pattern and limited link angles. The intention behind the proposed model is to describe the qualitative behaviour of the robot by a simplified kinematic approach, thus neglecting some of the non-linear effects that do not significantly contribute to the overall behaviour. This results in a model with significantly less complex dynamic equations than existing models, which makes the new model well-fitted for control design and analysis. An existing, more complex model and a class of sinusoidal gait patterns are analysed, leading to several properties that serve as a basis for the simplified model. Some of the revealed properties are also valid for ground robots. Simulations that qualitatively validate the theoretical results are presented.

Planar Path Following of Underwater Snake Robots in the Presence of Ocean Currents

“…Later, a control-oriented model of a USR exposed to currents was presented in [20]. The assumptions on which the control-oriented model is based are:…”

“…Sec. III briefly presents a model of a USR that has previously been developed in [20,21], and will serve as the basis for the control system in this paper. The control system and the stability analysis of the closedloop system are presented in Sec.…”

Analysis of underwater snake robot locomotion based on a control-oriented model

“…For these reasons, an analysis of snake robot locomotion, as well as motion planning and control design, are very challenging. This problem was approached in [10,11], where a control-oriented model for USRs was developed in order to approach these tasks. Because of the sinusoidal nature of snake locomotion, averaging is an appealing method for its analysis.…”

Waypoint guidance control for underwater snake robots exposed to ocean currents

“…In this section, a simplified modelling approach for USRs is introduced briefly and a transformation to make it suitable for path-following is presented. A detailed derivation of the model can be found in [20], [21], an analysis and comparison with the complex model from the previous section in [8], and the model transformation in [17].…”

“…Note that these values for the amplitudes of the sinusoidal motion were chosen with respect to the relationship derived in [21] that correlates the amplitude of the complex and the control-oriented model. For the complex model, the ILOS path following controller was implemented according to (16), (17), (18), and (20) with ∆ = Ln/2, σ = 0.002 m s , and control the gain k θ = 0.5.…”