The Japan Agency for Marine-Earth Science and Technology (JAMSTEC) has been developing "YUMEIRUKA", an autonomous underwater vehicle (AUV) with a fore X-rudder and an aft X-rudder. The vehicle can change its submersion depth by controlling the pitch angle using the two-sets X-rudder system.
As described herein, motion simulation results are compared with field experimental results to ascertain values of hydrodynamic coefficients of the vehicle. Several motion control-simulations are conducted to assess the vehicle performance.
The Japan Agency for Marine-Earth Science and Technology (JAMSTEC) has been developing "YUMEIRUKA", an autonomous underwater vehicle (AUV) (Ohta et al., 2016). The name is a word coined from Japanese words for dream and dolphin. The vehicle, which has tasks of seabed resource exploration and oceanographic observation, has a fore X-rudder and an aft X-rudder to control the submersion depth and pitch angle. Several reports of the relevant literature have described the vehicle's motion control by an X-rudder (Dubbioso et al., 2016; Lin et al., 2017; Zhang et al., 2017). Our vehicle uses PID control.
As described herein, motion simulation results are compared with field experimental results to ascertain values of hydrodynamic coefficients. Furthermore, several motion control simulations are conducted to assess the vehicle performance.
A photograph of "YUMEIRUKA" is portrayed in Fig. 1, with its principal dimensions shown in Table 1. The AUV, with 5000 mm body length, has maximum diving depth of 3000 m. A lithium ion battery drives the vehicle with maximum cruising speed of 3 knots. It can cruise while tracing bottom topography, using motion control modes of two kinds: a mode in which the pitch angle is controlled according to the slope of a submarine hill, and a mode in which a zero pitch angle is maintained. To realize these two control modes, the vehicle has two sets of X-rudders: a fore X-rudder and an aft X-rudder. Four thrusters located at the stern are driven at the same number of revolutions. The generated thrust does not control the vehicle depth or attitude. Therefore, the vehicle has five actuators to control pitch angle, submersion depth, heading angle, deviation in the Y-direction (Fig.2) and speed. The advantages over a cross rudder of an X-rudder are the following.
(1) The rudder increases horizontal and vertical control force by about 1.4 times.
(2) Even if one component of the rudder breaks down, cruising is possible with tolerable performance.
(3) The overhang by the body of a rudder in a plan view and side view are small, thereby facilitating handling on release and recovery and handling on the deck.
(4) Because the rudder face inclines, stealth performance is high.