Variable-structure filtering method for an unmanned wave glider

Abstract

The unmanned wave glider (UWG) comprises an underwater glider and surface float connected by an umbilical cord. It is a highly adaptable marine vehicle with the advantages of low cost, low power consumption, and long endurance. At present, research on UWG filtering is still immature and not fully utilized. This paper proposes a variable-structure filtering method based on the double-body coupled yaw manoeuvrability response model considering the hysteresis of the umbilical cord. The filtering method contains two core contents:an iteration-mean EKF (IMEKF) method and a variable-structure criterion. The former improves the filtering accuracy by iteration and mean processing of the one-step state prediction and transfer matrix to solve the nonlinear filtering problem of the double-body yaw motion; the latter solves the problem of the switching filtering model according to the tension / relaxation state of the umbilical cord, so that the filtering method is suitable for high sea conditions. Besides, the extended application of the variable-structure filtering method is proposed to replace the yaw motion sensor of the glider, thus reducing the cost and energy consumption of a motion sensor. Numerical simulation experiments were performed to verify the feasibility of the proposed method. The above research results will greatly contribute to the design, filtering, and control of UWGs for engineering applications.