Characteristic analysis in water for an amphibious spherical robot

After the Second World War, knowing ocean, using ocean and protecting ocean has become a strategic choice for the sustainable development of the world. Underwater vehicle research is increasingly active. This paper has focused on characteristic analysis in Water for an amphibious spherical robot. The amphibious spherical robot consists of a circular acrylic plate, a sealed hemispheroid, two mechanical arms and four drive units. Each of drive unit includes a water-jet propeller and two servo motors. The rotation angle of the servo motor can be changed by adjusting the duty ratio of the motor. In order to evaluate the performance of the amphibious spherical robot, we have done the experiment of forward motion in water, rotating experiment, floating and diving experiment. From the results we found that the robot had a maximum forward speed of 9.6 cm/s. Besides, the velocity was approximate linear change when the duty ranged from 30% to 90%. As to rotating experiment, when the PWM input signal was 100%, the angular velocity of spherical amphibious robot was 0.378 rad/s. When the PWM input signal was 10%, the angular velocity was 0.052 rad/s, which was too slow to work well. The angular velocity was approximate linear change when the duty ranged from 40% to 80%. From the floating and diving experiment we found that the diving time was the same whenever load or none-load. However, the load floating time was longer than none-load. The results proved that it is feasible to study performance evaluation for robot and also made a foundation for future research.