Search

This study develops a 6-DOF mathematical model for a robotic fish that considers surge, sway, heave, roll, pitch, and yaw. The model considers the conditions of a fish swimming in ocean current perturbations similar to the ocean current perturbations of the slender-body autonomous underwater vehicles. For swimming and turning behaviors, a nonlinear, dynamic, carangiform locomotion model is derived by using a planar four-link model. A 2-DOF barycenter mechanism is proposed to provide body stabilization and to serve as an actuating device for active control design. A barycenter control scheme is developed to change the center of gravity of the robot fish body by moving balancing masses along two axes. The projected torque on x and y axes propel pitch and roll angles to the desired settings. A Stabilizing controller, fish-tail mechanism, rigid body dynamics, and kinematics are incorporated to enable the fish robot to move in three dimensional space. Simulation results have demonstrated maneuverability and control system performance of the developed controller which is proposed to conduct path tracking of the robot fish as it swims under current perturbations.

Nonlinear equations of motion for fish-robot have been derived based on three basic motion behaviors, swimming, orientating, and driving. By incorporating the fish-tail mechanism, 2-DOF barycenter mechanism, and autonomous underwater vehicle-like dynamics model, the fish robot motion and maneuverability are considered in north-east-down frame. A sliding mode controller for swimming, orientating, and tracking control of a fish robot in three-dimensional motion is designed. Simulation results demonstrate excellent maneuverability and tracking performance of the fish-robot in three-dimensional swimming, which shows effectiveness of the controller against modeling uncertainty and ocean's current turbulence.

Nonlinear equations of motion for fish-robot have been derived based on two basic behaviors, swimming and orientating. By incorporating the fish-tail mechanism and autonomous underwater vehicle-like dynamics model, the fish robot motion and maneuverability are developed in earth-fixed frame motion. A nonlinear H ∞ robust controller for swimming, orientating, and tracking control of the fish robot is developed. Simulation results demonstrate excellent maneuverability and tracking performance of the fish-robot in two-dimension motion, which shows effect of the nonlinear H ∞ robust control against ocean's current turbulence.

Derivation of the mathematical model for a robot fish considering forward motion and yaw angle kinematics is presented. This model also includes details of the hydrodynamic force by considering the condition of fish swimming underwater. The nonlinear dynamical model in Carangi form locomotion type is derived by use of Lagrange's equation, which concerning about 4 links of fish robot equivalent model similar to the 4-link planar robot manipulator. Computer simulations conduct both in terms of open-loop response and animation motion of the fish robot swimming. These results indicate feasibility of the model for the robot with swimming speed 0.48 m/s and yaw swing angle ±12 degree. The model derived will be served as a basis for further investigation of control design for the complicated object.