Steering characteristics and path following control of a bionic underwater vehicle with multiple locomotion modes

The research on the path following control of the bionic underwater vehicle with high maneuverability and propulsive performance is a crucial issue. This paper investigates the planar path following control task of a bionic underwater vehicle with superior maneuverability. The steering characteristics of the sinusoidal offset and unilateral asymmetric steering signals are analyzed. The experimental results demonstrate that the two signals separately have smaller steering radius and power consumption in the low-frequency and relatively high-frequency range, and are consequently suitable for distinct scenarios. Furthermore, a switching nonlinear model predictive control strategy is proposed, which regulates the state error weighting values according to the real-time yaw angle error. The control strategy realizes autonomous switching of multiple locomotion modes to enhance the swimming speed of the bionic underwater vehicle and fulfills the purpose of improving the task-completing efficiency. The simulation and experimental results indicate that the bionic underwater vehicle achieved 3.49 and 2.92 times enhancement in swimming speed performance at straight and steering target path following control tasks, respectively. The proposed methods as well as obtained results can provide universal inspiration for the multiple motion-based path following control of autonomous underwater vehicles.