Real-Time Flight Simulation of Hydrobatic AUVs Over the Full 0$^{\circ}$–360$^{\circ}$ Envelope

Abstract

Hydrobatic AUVs are very agile, and can perform challenging maneuvers that encompass the full 0 • -360 • flight envelope. Such AUVs can be beneficial in novel use cases in ocean production, environmental sensing, and security, by enabling new capabilities for docking, inspection, or under-ice operations. To further explore their capabilities in such scenarios, it is crucial to be able to model their flight dynamics over the full envelope, which includes strong nonlinear effects and turbulence at high angles of attack. With accurate and efficient simulation models, new hydrobatic maneuvers can be generated and control strategies can be developed. Therefore, this article contributes with a strategy to perform efficient and accurate simulations of hydrobatic maneuvers in real time. A multifidelity hydrodynamic database is synthesized by combining analytical, semiempirical, and numerical methods, thereby capturing fluid forces and moments over the full envelope. A component buildup workflow is used to assemble a nonlinear flight dynamics model using lookup tables generated from the database. This simulation model is used to perform real-time simulations of advanced hydrobatic maneuvers. Simulation results show agreement with literature and experiment, and the simulator shows utility as a development tool in designing new maneuvers and control strategies.

Nonlinear model predictive control for hydrobatics: Experiments with an underactuated AUV

“…The tracking and robustness performance of the NMPC is evaluated in the SMaRC hydrobatics simulator in Simulink (detailed technical information on the simulator can be found in Bhat et al, 2021). The simulator uses a full‐envelope hydrodynamic model for an AUV and exhibits dynamic behavior similar to the real vehicle even at high angles of attack.…”

“…The tracking and robustness performance of the NMPC is evaluated in the SMaRC hydrobatics simulator in Simulink (detailed technical information on the simulator can be found in Bhat et al, 2021). The simulator uses a full-envelope hydro- where the propellers are used, but a faster rise time (up to 40% the rise time of PID) in the vertical case, where the buoyancy system is used.…”

“…Uncertainty estimates are not part of this work-robustness issues are addressed by adding measurement noise, using a full envelope nonlinear model in the hydrobatics simulator (presented in Bhat et al, 2021), and extending the MPC to a hybrid automaton using behavior trees (Marzinotto et al, 2014) to account for unsafe conditions (with safety limits and emergency actions; Bhat et al, 2020). Furthermore, robustness is inherent in MPC because of its feedback nature, so a certain degree of disturbance rejection and robustness to uncertainty exists.…”

Nonlinear Model Predictive Control for Hydrobatics: Experiments with an Underactuated AUV

“…It can be seen that the LTV-MPC with a resolution of 20 time steps has a significant advantage in solver time, but with a trade-off in cost and tracking. The tracking and robustness performance of the nonlinear MPC is evaluated in the SMaRC hydrobatics simulator in Simulink (detailed technical information on the simulator can be found in [Bhat et al, 2021]). The simulator uses a full-envelope hydrodynamic model for an AUV and exhibits dynamic behavior similar to the real vehicle even at high angles of attack.…”

“…Uncertainty estimates are not part of this work -robustness issues are addressed by adding measurement noise, using a full envelope nonlinear model in the hydrobatics simulator (presented in [Bhat et al, 2021]), and extending the MPC to a hybrid automaton using behavior trees [Marzinotto et al, 2014] to account for unsafe conditions (with safety limits and emergency actions [Bhat et al, 2020]). Furthermore, robustness is inherent in MPC because of its feedback nature, so a certain degree of disturbance rejection and robustness to uncertainty exists.…”