Longitudinal Model Identification and Controller Design for a Fish Robot with Control Fins via Experiments.

Area of Science:

• Robotics
• Control Systems
• Biomimetics

Background:

• Biomimetic underwater robots offer advanced maneuverability but present complex control challenges due to nonlinear dynamics and uncertainty.
• Effective control of longitudinal motion, specifically surge velocity and pitch angle, is crucial for stable and efficient underwater navigation.

Purpose of the Study:

• To present an experimental longitudinal mode control approach for a biomimetic underwater robot.
• To develop input-output models for surge velocity and pitch angle to address the complexity of fish robot control.
• To design and verify closed-loop control systems using PID controllers.

Main Methods:

• Derived experimental input-output models for surge velocity and pitch angle, treating the fish robot as a single system.
• Designed Proportional-Integral-Derivative (PID) controllers based on the identified linear models.
• Validated controller performance through both simulations and experimental tests.

Main Results:

• Surge velocity response models showed high agreement (75-81%) between identified linear models and experimental results at different speeds.
• Pitch angle response models exhibited lower agreement (34-68%), indicating greater complexity in pitch dynamics.
• PID controllers demonstrated effective surge velocity control and pitch angle stabilization, with observed convergence to 0° despite oscillations.

Conclusions:

• A linear modeling and controller design approach can effectively control the surge velocity of biomimetic underwater robots.
• Stabilizing the pitch angle is achievable, though the pitch dynamics require careful consideration due to lower model agreement.
• The proposed control strategy shows potential for enhancing the performance and stability of fish-like underwater robots.