Optimization of Flight Parameters for Petrel-L Underwater Glider

With recent developments in battery technology and low power technology, biofouling, a process referring to the gradual accumulation of organisms on underwater surfaces, has gained a foothold as the primary adversary in long-duration underwater glider flights (C. D. Haldeman, D. K. Aragon, T. Miles, S. M. Glenn, and A. G. Ramos, "Lessening biofouling on long-duration AUV flights: Behavior modifications and lessons learned," in Proc. OCEANS MTS/IEEE Conf., Monterey, CA, USA, 2016, pp. 1-8). Not only can biofouling increase the drag of the glider, but also it can add the buoyancy discrepancies, which changes the flight characteristics of the glider. Thus, it is necessary to adjust the flight parameters of underwater gliders accordingly for long-duration flights. In this article, the problems of a Petrel-L glider caused by biofouling are introduced. Several critical parameters including the hydrodynamic coefficients, the thermal expansion coefficient, the compressibility, and the net buoyancy compensation of the glider are optimized by an inner penalty function method based on the glider data and the dynamic model of Petrel-L. The effect of these parameters influenced by biofouling on the gliding range is analyzed. The results indicate that the changed hydrodynamic coefficients and net buoyancy compensation decrease the gliding range by 14.64% when the hotel load, including the power of the control system and the sensors, is 0.2 W. The gliding range loss can be decreased to 7.11% by adjusting the flight parameters. This article provides a reference of flight parameter adjustment for other types of biofouled underwater gliders.