Development of the Crown Motor

Conventional fluid motors require high-pressure fluids (20MPa~) and rotation speeds of these motors are extremely high (2,000~10,000rpm or more). Therefore it is difficult to apply these motors to mobile robots under hard conditions, like in fire disasters. Usually, high torque, low rotation speed, low pressure fluid motors are desired in robotics. This paper describes a new fluid motor named “Crown Motor”. It uses a new mechanism that consists of two crown gears with more than three cylinders around the rotation axis. The torque of this motor is high, with a high gear ratio of 77:1 that is accomplished by using only two crown gears, while rotation speed is slow enough (~16rpm) to allow for mobile robotic applications. The Crown Motor is being developed for the new fire fighter robot “Genbu” under construction in our laboratory. It has many advanced properties to be used in many applications. First, Crown Motors can drive with a low-pressure fluid (0.2~0.7MPa), like tap water (~0.2MPa), and they can take 4 states, CW, CCW, free and lock without any motor driver. Moreover, the motor is able to control its torque and rotation speed independently when supplied pressure of fluid is constant. It is easy to apply the motor to many kinds of machines such as used under (near) water or any kind of fluid. On the other hand, to use water fluid practically, it is necessary to introduce a mechanical valve system. In this paper, an electric valve system like pulse control and a mechanical valve system like timing control of brushless DC motor are also described.