To improve orientation control of an underwater vehicle, a whale-like underwater vehicle was developed. The intension of this research is that the vehicle performs quicker ascending/descending motion by controlling pitch and thrusting toward the direction of the body axis. This vehicle has copied the function of a spermaceti organ of a sperm whale (Physeter macrocephalus) to adjust its buoyancy and to control its pitch. A weight positioning system for the vehicle had been developed to realize this function. The internal dead weight moves inside the vehicle body, not only to the body axis direction but also perpendicular to it. In swimming experiments, the vehicle was able to change its pitch angle at 45 degrees within 5 seconds. By using this mechanism, high-speed and large-angled orientation control of an underwater vehicle will be realized.
In recent years, underwater robots on the basis of aquatic animals had been developed and studied by many researchers (Triantafyllou et al, 2000). If quick turning and ascending/descending motions like an aquatic animal are realizable, underwater operation efficiency will improve, and it will be useful for various underwater tasks. For this reason, several biomimetic underwater vehicles were developed in this research based on various knowledge about propulsion performance and turning and ascending/descending motions (Hirata, 2000; Hirata, Takimoto and Tamura, 2000; Konno et al, 2006). It spends most of its life in the deep ocean but periodically travels to an oxygen source at the surface. It uses its spermaceti organ to adjust its buoyancy and to control its pitch (Clarke, 1970). The pitch angle of a sperm whale in a deep diving performance is 40 to 60 degrees (descending) or 40 to 80 degrees (ascending) (Miller et al, 2000; Watwood et al, 2006).
