PTEROA150

DEVELOPMENT OF AUV 'PTEROA'


Pilot Model PTEROA150

Mission

The design concept of PTEROA150 has following two distinctive features: high gliding performance and altitude keeping capability even when it cruises over a complicated bed.
At the first/last stage of the mission, the vehicle is obliged to descend/ascend from/to the surface to/from a target point on the bottom. If the vehicle can move horizontally at this stage converting potential energy to velocity energy, it can be operated far from the mothership without her shifting. High gliding ability is essential for this purpose. When it dives, for example, to 6000m depth at a gliding angle of 15 deg, it could cover an area 22km radius from the mother ship. Energy in battery cells is not dissipated and is saved for the cruising over the bottom.
For the measurements at the bottom, the vehicle may be obliged to keep constant and low altitude from the bed. When it comes to an obstacle, it should ascend over the obstacle by pull-up maneuvering because the vehicle is inhibited from swimming aside to keep a straight measurement line. This action should be done automatically on the basis of ranging data, and good pull-up maneuverability is requested for this purpose.

Design


******Fig.1 Pilot model PTEROA150******

Fig. 1 shows a pilot-model vehicle named PTEROA150, which was designed and constructed in 1989. PTEROA150 can dive to 2000m depth and cruise for 1 hour in 2 knots. General arrangement is illustrated in Figure 2 and the principal particulars are shown in Table 1. The vehicle consists of a body, a pair of elevators, twin vertical stabilizing fins, twin skegs, and a pair of rudders. Principal dimensions of body are 150cm, 75cm, and 45cm in length, width, and thickness, respectively. Dry weight is about 220kg.



***********Fig.2 General arrangement of PTEROA150********

*********Table 1. Principal particulars of PTEROA150*********

The shape of longitudinal cross section of the body at the center line is NACA0030 and the transversal cross section is approximately oval [2,3]. The center of buoyancy is located a little behind the 6 square station, and the center of gravity is located just before it. As the body is not cylindrical as torpedoes but rather flat, the lift force acts mainly on the body. Elevators enhance good performance of pull-up behavior and stability of swimming. A pair of propeller thrusters are fitted under the vertical stabilizing fins. They can be operated independently to let the vehicle yaw. Two oil-immersed induction motors of 300W are directly connected to propellers. The speed of revolution is about 600 rpm for 1 m/sec cruising. A small inverter was newly designed to supply electric power to the induction motor. Three actuators constructed of oil-immersed stepping motors are equipped to trim control surfaces, i.e. two for elevators and one for rudders, by which the elevator can be trimmed by about 30 deg/sec when the vehicle is cruising in 3 knots.

Considering the convenience of handling and testing in the towing tank, the principal dimensions are designed so as to minimize the total volume. All apparatus are installed in 8 pressure cylinders. The main pressure cylinder is 27 cm in diameter, which is rather large compared to the dimension of the body, because commercially available CPU board and interface boards, which can be set at the slot of personal computer, are selected. This restricts the arrangement of other cylinders in the body. Though 65% of the void in the body is filled with buoyant, it is impossible to install cylinders for 6000 m depth diving. The design depth of these cylinders is, therefore, determined as 2000 m to reduce the total weight of the vehicle.
Four active echo sounders are fitted to detect the shape of the bed for constant altitude swimming over the bed. Sonic beams are projected towards the front and in the directions of 30 deg, 60 deg, and 90 deg in dips. Several algorithms of control on the basis of ranging data were examined by the computer simulation study[4].
PTEROA150 can be connected to the support computer on the surface through a RS232C connector and an umbilical cable. It can be also operated, therefore, as a ROV under the control of the support computer.

Last modified: Thur July 6 1995