Heading Control of the DARPA Suboff with PID-Based CFD

This study develops a course-keeping control system for a submerged body using a PID-based CFD methodology. The DARPA Suboff hull served as a reliable benchmark for evaluating straight-ahead motion and course-keeping performance. Velocity control for the DARPA Suboff, constrained to surge motion, was achieved at various speeds (V = 2.75 m/s, V = 6.096 m/s and V = 9.152 m/s) using a Proportional-Integral (PI) controller. The propulsive characteristics of the straight-ahead maneuver were validated with the available results. While the body was advancing at the desired speed, the course-keeping capabilities were examined with the Proportional–integral–derivative (PID) controller. The PID coefficients obtained from the Nomoto model were provided as input parameters to the controller developed in this study. This study focuses on developing a controller using the unsteady RANS method and examining system responses rather than deriving PID coefficients through the Nomoto model. In the study, systematic tests were carried out at various velocities (V = 2.75 m/s, V = 6.096 m/s and V = 9.152 m/s) and target heading angles (ψ[[inf]]T[[/inf]] = 0.0 deg, ψ[[inf]]T[[/inf]] = 5.0 deg, and ψ[[inf]]T[[/inf]] = 15.0 deg) considering three degrees of freedom (surge, sway, yaw) to assess the course keeping ability and rudder responses. The flow was modeled as single-phase, incompressible, and fully turbulent. The k-ω turbulence model and URANS equations captured flow behavior. Adaptive meshing and all y+ wall treatment ensured accurate boundary layer resolution. DFBI modeling calculated force and moment interactions between the hull, propeller, and rudder. Moving Reference Frame (MRF) simulated propeller rotation, while Rigid Body Motion (RBM) handled rudder rotation, balancing computational efficiency and accuracy since it leverages the steady-state efficiency of MRF and the time-accurate capabilities of RBM. PID-controlled heading simulations demonstrated rapid, stable, and precise alignment with target headings, reducing error and overshoot. The developed PID controller showed robust performance across the wide range of tested speeds and heading angles, confirming their suitability for submerged structures. This efficient, simulation-driven approach highlights the potential for advanced control systems in marine applications.