Abstract
In this study, an inchworm-type mobile robot has been developed. This robot has an articulated structure. This robot is able to advance by using vertically undulatory motion of whole body though it has neither legs nor wheels. It consists of six segments connected by four pitch joints and one yaw joint. Using these four pitch joints, this robot demonstrated high mobility in sagittal plane. This robot was able to ascend and descend the stairs sequentially, get over the obstacle of 600mm in height and climb the vertical narrow passage. In addition, because it had symmetric structure, it was possible to move backward easily just like moving forward. Even if it became upside down, it was possible to move just like normal posture. But if the robot fell sideways, the robot was not able to move until returning to normal posture. It is necessary to develop some wake-up method of the return of the robot from the state which had fallen sideways. In this study, we propose the wake-up method which uses the yaw joint, and analyzed the wake-up motion of this articulated mobile robot. The proposed motion consists three steps. Firstly, the robot bends its tail in the direction which wants to rotate itself. We call this posture the initial posture. Secondly, The robot rotates the yaw joint to raise its tail up. According to the initial posture, the torque required for the yaw joint is different. By doing so, the robot is twisted internally. Finally, by extending the bended pitch joints, the robot returns to normal posture. In this study, we developed a mathematical model for inchworm robot that was waking up and then analyzed the wake-up motion in terms of required torque for yaw joint. The required torque was different depending on initial posture. Decreasing the angle where the third pitch joint rotates, a space necessary for the wake-up motion became small, but required torque for the yaw joint became exponentially large. It is necessary to set initial posture in proportion to the starting torque of the motor equipped in the yaw joint. When the angle of rotation was set to -2.001(rad), required torque became most small. It was confirmed that the robot returned to normal posture in 4.02 seconds in this case.
