DYNAMIC LOSS OF STABILITY IN-DEPTH CONTROL OF SUBMERSIBLE VEHICLES

Control of a modem submarine is a multi-dimensional dynamical problem coupling considerations of initial static stability, hydrodynamic perf ormance, and control system response. In this work, the loss of stabil ity at moderate-to-high speeds is examined using a nonlinear Hopf bifu rcation analysis. Complete linear state feedback is used for demonstra tion purposes for depth control at level attitude and for a fixed nomi nal speed. The control time constant, the nominal and actual speeds, t he metacentric height, and the stem-to-bow-plane ratio are used as the main bifurcation parameters. A complete local bifurcation mapping pro vides a systematic method for evaluating the bounds of controllability for the control system design parameters for a vehicle with a given s et of hydrodynamic coefficients. The submarine and its potential desig n modifications are verified with direct numerical simulations.