Innovation in Underwater Robots: Biologically Inspired Swimming Snake Robots

Abstract : Increasing efficiency by improving locomotion methods is a key issue for underwater robots. Moreover, a number of different control design challenges must be solved in order to realize operational swimming robots for underwater tasks. This paper proposes and experimentally validates a straight line 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 towards 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 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 towards and along the desired path for both lateral undulation and eel-like motion patterns.

 EXISTING SYSTEM :

 ? There does not exist a theoretical foundation for analyzing the stability of the complete CPG-robot system. ? A VHC is a time-independent relation involving the configuration variables of a mechanical system that does not physically exist in the system, but is enforced via feedback. ? The structure of the system will therefore be explained in an intuitive and non-technical way. ? The intuition behind using is that the control system has access to its position while knowing its velocity with respect to the surrounding fluid. ? The robot therefore has to compensate for an oscillating current component.

 DISADVANTAGE :

 ? An important control problem concerns the ability to follow given reference paths, and this is the topic of this paper. ? For centuries, engineers and scientists have gained inspiration from the natural world in their search for solutions to technical problems, a process termed biomimetics. ? Another important control problem for underwater vehicles concerns the ability to achieve efficient motion with preferably a minimum amount of consumed energy in order to be able to undertake longer missions. ? However, including the impact of the fluid torques on the power consumption of the system, will improve the accuracy of the model from a hydrodynamic and energy efficiency point of view.

 PROPOSED SYSTEM :

 • The proposed feedback control strategy enforces virtual constraints which encode biologically inspired gaits on the snake robot configuration. • A two-state ocean current observer based on relative velocity sensors is proposed. • This generalized gait includes, but is not limited to, lateral undulation for land based snake robots, eel-like motion for underwater snake robots, and other sinusoidal forms of motion, like the gaits proposed. • We propose the new control system for maneuvering control of underwater snake robots.

 ADVANTAGE :

 ? It is expected that the performance of the robot will be influenced by the external structure that is used to attach the reflective markers during the motion of the robot. ? In particular the performance of the guidance strategy was investigated experimentally for straight line paths for both lateral undulation and eel-like motion patterns. ? It should be noted that in order to investigate the performance of the path following control strategies, the fluid coefficients were chosen under the the assumption of a steady-state flow. ? Underwater snake robots thus bring a promising prospective to improve the efficiency and maneuverability of modern-day underwater vehicles. ? It is furthermore of interest to test the scheme for the fluid coefficient identification in combination with current effects in the future.