No abstract

A terrain-adaptable tracked vehicle suitable for traveling over a variety of surfaces, including stairways, with features of low energy consumption, high speed, and light weight, has been designed and developed. Active terrain adaptability is performed by the variable track configuration scheme, which can be changed to suit temporary road conditions. Many requirements for the robot vehicle, such as simple track configuration control, suspension for high road grip, reduction of turning resistance force, coexistence of high climbing ability and high speed on flat surfaces, and reduced tare weight, have been achieved mechanically without disturbing variable track configuration characteristics.

The goal of this paper is to develop an underwater robot with a buoyancy control system based on the spermaceti oil hypothesis. Sperm whales have a spermaceti organ in their head that is filled with spermaceti oil. Spermaceti oil is high quality oil and was used as material for candles, lubricant, and so on. There is a hypothesis about spermaceti oil that insists that sperm whales melt and congeal their spermaceti oil and change the volume of the oil to control their own buoyancy. This hypothesis appears suitable for the underwater robot because no materials for the ballast, such as sea water taken in at another place and iron, are discarded in the sea. To choose the best material as a spermaceti oil substitute, we measured the densities of four materials at both liquid and solid states, and calculated their buoyancy differences between both states. From the results, we concluded that the paraffin wax was the best material because its buoyancy difference is the largest of the four and its melting point is relatively low. Next, we directly measured the buoyancy of the paraffin wax and found that a particular arrangement of nichrome wire, which heats the oil, increases the level of buoyancy. Finally, we developed an underwater robot with a buoyancy control system based on this hypothesis. We measured its buoyancy and succeeded in surfacing of the robot in a small water tank.

The highly maneuverable water-rescue robot vehicle we propose has variably configured segmented wheels (VCSW) that propel it over rough or muddy terrain, on water, or even underwater. The VCSW consist of six segments, a hub and spokes, and a drive wheel. The ends of segments are supported by the drive wheel and are pushed and towed by the spokes and eccentric hub based on wheel rotation. The direction and maximum deployment of segments are controlled by an eccentric vector of the hub, which is controlled by the combination of rotational angles of duplicate eccentric shafts. This motion catches on a slippery surface, e.g., a wet road, and produces a strong thrust on and under water. Under water, the vehicle must control forward and reverse speed, direction, depth, and inclination. The newly designed semiautomatic control automatically controls depth and inclination via the feedback of pressure and inclination information, and speed and direction are controlled manually by joysticks. Data required for control is acquired, calculated, and converted by a computer to rotation speed and eccentric vectors for each VCSW.

A conceptional idea of the pseudo mechanism is proposed. This concept means that a different mechanical feature from the natural one appears on the mechanism by means of control method. For example, a worm gear behaves like an one-way clutch. Generally, worm gears cannot be driven by load torque because of its mechanical stop feature. But the worm gear of this concept can be driven by load in specified direction, and the rotation to the other direction is prohibited. This asymmetrical motion is achieved by a switching operation of a force feedback control. The applied load torque is detected and fed back positively to a position servo control system in order to achieve power assist control. The worm gear seems to be driven by the load torque and it resembles to a spring motion. If the force feedback line is cut off, the drive system cannot be driven by a load. The switching operation of the force feedback line causes to a selection of back drivable feature or mechanical stop feature. The switching condition is set by a direction and threshold value according to the required mechanical feature. The pseudo mechanical worm gear also pretends as a torque limiter or a ratchet.