6. Underwater torpedo

Let's consider a torpedo-type underwater robot such as the one shown in figure 24 . To move, the drone is equipped with three control surfaces and a thruster. The input u ₀ , is the speed of rotation of the thruster and u ₁ , u ₂ , u ₃ are the angles of the control surfaces. We assume that the velocity vector v _r is always along the direction of the robot, or equivalently, the drone has no lateral velocity.