System design optimization of an underwater glider involves various disciplines, such as hydrodynamics, structure, sizing, control, power, payload, and trajectory, which overlap with each other and influence the endurance of the system. Compared with traditional optimization methods, multidisciplinary design optimization provides a more efficient method for complex engineering problems involving overlapping disciplines. This article establishes a universal disciplinary framework of an underwater glider after the system analysis, which involves five disciplines, including hydrodynamic shape, pressure hull, buoyancy, attitude, and energy. To decouple the relationship among these disciplines and improve the efficiency of optimization, approximate models in the disciplines of hydrodynamic shape and pressure hull are established. After the coupling analysis, a novel approach is proposed for the system design optimization of an underwater glider, in which the concurrent subspace optimization, penalty function method, and the multipopulation genetic algorithm are combined together. The approach proposed in this article can meet the diversified design requirements of underwater gliders in different observation missions, which is verified by a sea trial of an improved Petrel-L glider.

Underwater glider (UG) is the only marine equipment in the field of ocean observation that can realize unmanned autonomous, all-weather and wide-area continuous 3-D observation. The rapid individualized design (RID) and full lifecycle management (FLM) make two difficulties to be solved in the industrialization development of UGs since the UG system involves interdisciplinary multiphysics and there exists multisource uncertainties in complex ocean environment. With the application of new information technologies in industry, the above problems can be effectively solved by the digital twin (DT)-driven methodology. In this article, an architecture of DT-driven RID and FLM for UGs is first put forward based on our previous theoretical research and technique development. Then, the proposed architecture of DT-driven methodology is researched in detail in terms of its digital modeling, design optimization, virtual verification and practical application. Finally, Petrel developed by China is introduced, and a typical preliminary application of DT-driven methodology is presented based on petrel to verify its feasibility. The architecture proposed in this article is also appropriate for other types of autonomous underwater vehicles.

The hydrodynamic shape, which incorporates superior turning maneuverability and gliding stability, is an important factor for underwater gliders (UGs) to realize remarkable endurance. In this study, a six-DOF parameterized dynamic model of Petrel-L glider, involving the variables of wing location and stabilizer area, is established by importing the hydrodynamic coefficient approximate models of different hydrodynamic shapes. Based on the dynamic model, the analysis of turning maneuverability is carried out to summarize the effect of wing location and stabilizer area on the spiral motion pattern of UGs. Furthermore, the gliding stability is analyzed by importing the disturbances caused by the net buoyancy variation, corrosion of the pressure hull, and biofouling into the established dynamic model. The analysis results indicate that the spiral motion of UG in both positive and negative spiral patterns can be realized by adjusting the wing location and the stabilizer area. Finally, the positive spiral pattern is proved to have higher gliding stability and thus recommended for improving the endurance of UGs, which is featured by a larger stabilizer area and a proper wing location. The parameterized dynamic model, analysis method, and analysis results in this article provide references for other UGs.

For underwater gliders (UGs), high trajectory accuracy is an important factor in improving the observation of ocean phenomena. In this paper, a novel method of trajectory optimization is proposed to increase the trajectory accuracy of UGs, which is approximately based on the nonlinear dynamic model, rather than the linearization model. Firstly, a dynamic model of UGs is established to analyze the effect of the input parameters on the trajectory error, based on some approximate models that replaced the dynamic model due to its strong nonlinearity. Then, an identification strategy for the trajectory error is proposed, and the trajectory optimization strategy is analyzed while considering gliding range loss and observation distance loss. Finally, the identification strategy and trajectory optimization strategy proposed in this paper are verified by a sea trial of Petrel-L. The dynamic model, identification strategy, and optimization strategy are appropriate for other UGs.