Heading multi-mode control based on soft-switching for autonomous underwater vehicle

This paper aims to solve the problem that a single control method can't fit to each operating condition of heading control for autonomous underwater vehicle (AUV). A multi-mode strategy based on soft-switching is proposed, which can get better performance by smooth switching of control modes. The control mode consists of two levels, which is named as two-level-mode method. On the first level, the control mode is divided into six according to the operating state of AUV. On the second level, based on the existing mode the control mode is divided into three depending on AUV′ speed. In addition, the BB-PID controller is designed for heading control, as well as the sigmoid function is constructed to smoothly switching at different speed without saltation. The simulation and experiment results demonstrate that BB-PID controller achieves outstanding performance and the switching strategy is much more effective by comparing the RMS, RMSE, SSE between switching based on sigmoid function and switching based on threshold.