Future space stations and space factories require many small manipulators which work in hazardous space environment instead of man. An actuator is one of the most critical element for the manipulator. The long-life and light-weight are expected for the space using actuator. This paper presents the development of a harmonic drive actuator which has the features of the vacuum environment durability and the light-weight for a 1-m class space manipulator. The tribological study on bearings and gears is carried out experimentally. Some candidates for materials and lubricants are tested in the vacuum chamber and the wear-out properties are investigated. The ball bearing with the MoS2 sputtered ball and race and the PTFE composite retainer had the excellent characteristic and life-time. The operation life-time over 1, 000 hours was attained for the hamonic gear by employing the nitrided steel spline and the PFPE grease. The actuator with the high torque/weight ratio, which was integrated with a rare-earth brushless servo motor, an optical encoder, drive electronics and a harmonic gear compactly, was developed.
A single gimbal CMG system is a promising candidate for an actuator of attitude control systems for large space structures. One of its problems is the existence of singular states. Various steering laws assume redundancy in the system and avoid singular states by maximizing a certain criterion function value by a gradient method. But it is not theoretically clear whether these steering laws can avoid all singular states actually. In this paper, a quadratic form is defined for each singular state, which enables to classify singular states into three types. In the vicinity of the two types of singular states, escape from the vicinity is not guaranteed locally. Also it is diffcult to guarantee that the system does not go into the vicinity of any two types of singular points by using the gradient method only. Examples of three type singular states are shown for three configurations.
A static instability of a slender free-fiXed elastic sttrip in a uniform air stream is studied.The analysis is performed using slender body aerodynamic theory and beam theory. Both aerostatic divergence speed and divergence mode are fomd by the analysis. lt is seen by wind tunnel tests that there exist higher divergence speed based on linear lift and lower divergence speed due to nonlinear lift of slender body caused by side edge suction forces.
Flying Platform, supported by the ducted fan (s), is the safe and simplest airplane. The height of vehicle CG. from the ducted-fan-aerodynamic-center should be selected quite carefully, in the stability and control view point. A simple design philosophy is presented, which makes the horizontal speed and the attitude uncouple. The vehicle is made neutrally stable, and the CG. is located above the ductaerodynamic-center by the order of duct-innerdiameter. This design philosophy would also make the vehicle safe against horizontal gust. Preliminary numerical example is presented by using available (somewhat incOmplete) data. The author believes that this kind of vehicle will attract many youngmen in near future, as their hobby vehicles.