Development of Actuator for Large Space Manipulator Arm

Abstract

This paper presents the study on an actuator for a 10-meter class space manipulator, which would be required for constructing large space structures and handling payloads on orbit. The durability in vacuum environment, compactness and light-weight are emphasized in designing the actuator. A mechanical paradox planetary gear mechanism is employed for the gear box, since it has several advantages for the actuator of a space manipulator essentially, such as high reduction ratio, light-weight, high rigidity and simplicity. The tribological study on the gears in vacuum environment are conducted. The combination of hardened SUS 440 C and nitriding steel with PFPE grease lubricant shows the sufficient friction and wear properties. The life test by cyclic rotational motion is carried out, and the efficiency and wear of the gear box are investigated, relating with the paradox gear mechanism. The actuator, which has the mass of 20 kg, diameter of 200 mm and durability more than 1 000 hours in vacuum environment, were developed.