Speed evaluation of a freely swimming robotic fish with an artificial lateral line

Artificial lateral line has been drawing an increasing attention recently for its potential applications in robotics. Experiments are usually conducted with a bioinspired robot in a controlled environment, where the sensing platform is held stationary or slowly driven with a simple linear motion. In this paper, we conduct a more practical and challenging study where the robot uses artificial lateral line to evaluate its linear velocity while freely swimming. We use onboard artificial lateral line to measure the pressure profiles over the surface of a robotic fish and employ onboard IMU (inertial measurement unit) to record the motion kinematics of the robot while freely swimming at various speeds. We find that 1) pressure changes are greatest on the head of the robot; 2) pressures increase along with the swimming speed and the oscillation amplitude of angular velocity of the robot. Therefore, we propose a nonlinear prediction model which incorporates distributed pressure and angular velocity to estimate the speed of the robot. Online speed evaluation experiment demonstrates the effectiveness and the accuracy of the proposed model.