Joystick in Closed-loop Control of ROVs with Experimental Results

In standard ROV operations a joystick command console is used for positioning control. The joystick command console controls the propeller speed of each thruster. A thrust allocation may be used for manual control in surge, sway, heave and yaw. Accurate station keeping or high precision moves require a skilled and concentrated pilot. Some ROV tasks, such as station keeping and trajectory tracking, can be automated by a closed-loop positioning control system. However, for tasks such as inspection of an unknown object or complex manipulation work, the desired trajectory is not known in advance, and must be decided by a pilot based on view from ROV cameras or other sensor data. In that case, the pilot should have an easy way of guiding the ROV without spending a lot of effort on the positioning control itself. The low level position control should be automated by a controller that compensates for ROV dynamics and environmental loads. A joystick with closed-loop control functions is proposed in this paper. Joystick inputs will generate desired velocities or positions rather than direct thruster speed commands. The control of desired states is done by a closed-loop positioning system with feedback. The methods for the proposed joystick control modes are described in this paper. Full scale experiments are presented demonstrating the performance of the joystick in closed-loop control.