The motor boat here considered has standard actuation means composed of a propulsion force along the boat’s main axis, and a rotation torque used to modify the boat’s heading.
Classical, either linear on nonlinear, control techniques can control the motion of such a boat effectively as long as the boat has to keep moving along a feasible trajectory. But they are inefficient when it comes to stabilize the boat at a fixed desired position and orientation.
The transverse function control approach can be used to design a feedback control law capable to handle all operational conditions.
The first simulation video illustrates the following scenario. Initially the boat has to reach a fixed reference point (materialized by the origin of the yellow frame), then has to track this point along a circular path that ends up at another fixed reference position. Wind is blowing from north-west (represented by the white arrow on the video) and, because of it, the only way to maintain the boat at a fixed position is to have its heading converge to the wind’s direction, with a propulsion force that opposes the action of the wind on the boat. These objectives have to be achieved without knowing the wind’s direction, nor its amplitude, in advance. It turns out that, by contrast with a classical approach of control, on-line measurement or estimation of the wind’s characteristics is not needed with this approach. On the video, the thrust applied to the boat is represented by the thick colored line behind the boat’s stern. The color is green when the thrust is positive, and red otherwise.
Click here to watch the video.
The second video implements the same feedback control, except that the desired boat’s orientation is fixed and set equal to the (horizontal) west-east direction. Since this objective is not compatible with precise position tracking along the circular trajectory, the control performs a compromise between these contradictory objectives. During the final phase, maneuvers that are needed to maintain the boat near the desired position and orientation are performed automatically.
Click here to watch the video.