Underwater Snake Robots Research Articles

Innovation in Underwater Robots: Biologically Inspired Swimming Snake Robots

Increasing efficiency by improving locomotion methods is a key issue for underwater robots. Moreover, a number of different control design challenges must be solved to realize operational swimming robots for underwater tasks. This article proposes and experimentally validates a straightline-path-following controller for biologically inspired swimming snake robots. In particular, a line-of-sight (LOS) guidance law is presented, which is combined with a sinusoidal gait pattern and a directional controller that steers the robot toward and along the desired path. The performance of the path-following controller is investigated through experiments with a physical underwater snake robot for both lateral undulation and eel-like motion. In addition, fluid parameter identification is performed, and simulation results based on the identified fluid coefficients are presented to obtain a back-to-back comparison with the motion of the physical robot during the experiments. The experimental results show that the proposed control strategy successfully steers the robot toward and along the desired path for both lateral undulation and eel-like motion patterns.

Adaptive controller design for underwater snake robot with unmatched uncertainties

Because of hydrodynamic model error of the present dynamic model, there is a challenge in controller design for the underwater snake-like robot. To tackle this challenge, this paper proposes an adaptive control schemes based on dynamic model for a planar, underwater snake-like robot with model error and time-varying noise. The adaptive control schemes aim to achieve the adaptive control of joint angles tracking and the direction of locomotion control. First, through approximation and reducibility using Taylor expansion method, a simplified dynamics model of a planar amphibious snake-like robot is derived. Then, the L1 adaptive controller based on piecewise constant adaptive law is applied on the simplified planar, underwater snake-like robot, which can deal with both matched and unmatched nonlinear uncertainties. Finally, to control the direction of locomotion, an auxiliary bias signal is used as the control input to regulate the locomotion direction. Simulation results show that this L1 adaptive controller is valid to deal with different uncertainties and achieve the joint angles tracking and fast adaptive at the same time. The modified L1 adaptive controller, in which the auxiliary bias item is added, has the ability to change the direction of locomotion, that is, the orientation angle is periodic with arbitrarily given constant on average.

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

This letter presents a control system that enables an underwater snake robot to converge towards and follow a straight path in the presence of constant irrotational ocean currents. The robot is assumed to be neutrally buoyant, fully submerged and moving in a virtual plane with a sinusoidal gait and limited link angles. The proposed control approach uses a heading controller that exponentially stabilises the heading of the robot towards the desired heading, which is obtained by an integral line-of-sight guidance law. Uniform semiglobal exponential stability of the control system is formally proved using cascaded systems and Lyapunov theory. Simulations are presented that illustrate and validate the theoretical results.

Experimental investigation of efficient locomotion of underwater snake robots for lateral undulation and eel-like motion patterns

Underwater snake robots offer many interesting capabilities for underwater operations. The long and slender structure of such robots provide superior capabilities for access through narrow openings and within confined areas. This is interesting for inspection and monitoring operations, for instance within the subsea oil and gas industry and within marine archeology. In addition, underwater snake robots can provide both inspection and intervention capabilities and are thus interesting candidates for the next generation inspection and intervention AUVs. Furthermore, bioinspired locomotion through oscillatory gaits, like lateral undulation and eel-like motion, is interesting from an energy efficiency point of view. Increasing the motion efficiency in terms of the achieved forward speed by improving the method of propulsion is a key issue for underwater robots. Moreover, energy efficiency is one of the main challenges for long-term autonomy of these systems. In this study, we will consider both these two aspects of efficiency. This paper considers the energy efficiency of swimming snake robots by presenting and experimentally investigating fundamental properties of the velocity and the power consumption of an underwater snake robot for both lateral undulation and eel-like motion patterns. In particular, we investigate the relationship between the parameters of the gait patterns, the forward velocity and the energy consumption for different motion patterns. The simulation and experimental results are seen to support the theoretical findings.Electronic supplementary materialThe online version of this article (doi:10.1186/s40638-015-0029-4) contains supplementary material, which is available to authorized users.

An application of genetic algorithm to optimize the 3-Joint carangiform fish robot’ s links to get the desired straight velocity

Biomimetic robot is a new branch of researched field which is developing quickly in recent years. Some of the popular biomimetic robots are fish robot, snake robot, dog robot, dragonfly robot, etc. Among the biomimetic underwater robots, fish robot and snake robot are mostly concerned. In this paper, we study about an optimization method to find the design parameters of fish robot. First, we analyze the dynamic model of the 3-joint Carangiform fish robot by using Lagrange method. Then the Genetic Algorithm (GA) is used to find the optimal lengths’ values of fish robot’s links. The constraint of this optimization problem is that the values of fish robot’s links are chosen that they can make fish robot swim with the desired straight velocity. Finally, some simulation results are presented to prove the effectiveness of the proposed method

Energy efficiency of underwater robots

Increasing efficiency by improving locomotion methods is a key issue for underwater robots. In this paper, we investigate the power consumption of different underwater robotic systems and compare the energy efficiency of the different robots depending on the desired motion. In particular, we compare the energy efficiency of underwater snake robots, which can provide both inspection and intervention capabilities and thus are interesting candidates for the next generation inspection and intervention AUVs, with those of the widely used robots for subsea operations which are the remotely operated vehicles (ROVs). In order to compare the energy efficiency of underwater snake robots with the energy efficiency of the ROVs, a simulation study is performed comparing the total energy consumption and the cost of transportation of underwater snake robots and ROVs. The simulation results show that with respect to the cost of transportation metric and the total energy consumption the underwater snake robots are more energy efficient for all the compared motion modes compared to the ROVs.