Path following experiments were carried out in a testing pool at IIS to investigate the designed controllers' performances. Two types of 2-dimensional paths, a rectangular path and a zigzag path, are planned as the targets of control. Two modes of control actions, straight cruising and rotation at the corner, are prepared and the target paths can be realized as a sequence of these control actions. Fig.8 and 9 show the experimental results of the Twin-Burger to follow these target paths which are indicated by dotted lines.
In these figures, the trajectories and surging position data are calculated by dead reckoning on the basis of the outputs from the onboard speed sensors and the other data are directly measured by onboard sensors. It is shown that the Twin-Burger successfully follows both of the target paths by the implemeted sliding controllers.
The position errors of the control actions are, however, accumulated along a whole path because the target trajectory for each action is determined on the basis of the relative position of a waypoint to the preceded one in the planned path. This can be avoided by defining the target trajectories with the absolute positions of the waypoints.
Even though the implemented sliding controllers are designed on the basis of a simplified equations of motion, the Twin-Burger succeeds in following the commanded paths stably. It can be confirmed that the sliding control methodology provides simple and effective control system for underwater vehicles.