Fig. 3 shows experimental data of depth, pitching angle and trimming angle of elevators when PTEROA150 cruises in 0.96 m/sec keeping constant depth of 1 m in the towing tank. Considering that the length of body is 1.5m, the vehicle is controlled appropriately. Measurement of state vector of the vehicle was carried out at every 0.4 second and the trimming angle of the elevators was changed at every 1 second.
Fig. 4 shows the data when the vehicle was ordered to
change the depth from 1 m to 2 m , and vice versa.
These free swimming tests in a towing tank started in January, 1990.
The first sea trial was successfully conducted in November, 1990 off Numazu, Shizuoka Prefecture. It was demonstrated that the PTEROA150 can be used as a new apparatus for underwater survey. Fig. 5 shows a trajectry of the vehicle of the trial on December, 1992. At the first stage, the vehicle swims for 100 seconds keeping 3 m depth. Then, it descends to the bottom till it finds the bed. When it finds the bed, based on data of ranging SONAR, it changes the control mode to the constant altitude mode and swims keeping constant depth as illustrated in the figure. It should be emphasized that the vehicle has not known the configuration of the bed beforehand.