Color marker employed in conjunction with space robots for on-orbit assembly has been developed. The marker consists of three printed discs with different colors. When used for on-orbit assembly, markers will be attached at the proximity of the connection mechanisms of assembly segment for large space structures. The distance and attitude of the segments can be measured by the positional relationship between the color discs of the marker. From the evaluation test, it has been verified that the performance of the measuring system with the color markers can meet the requirement of the space robot arms.
An algorithm is developed for estimating the motion (relative attitude and relative position) of large pieces of space debris, such as failed satellites. This algorithm is designed to be used by a debris removal system which would perform various operations on space debris such as observation, investigation, capture, repair, refuel and de-orbit. The algorithm uses a combination of stereo vision and 3D model matching, applying the ICP (Iterative Closest Point) algorithm, and uses time series of images to increase the reliability of relative attitude and position estimates. To evaluate the algorithm, a visual simulator is prepared to simulate the on-orbit optical environment in terrestrial experiments, and the motion of a miniature satellite model is estimated using images obtained from this simulator.
On Earth orbit, astronomical observation is in very good condition that is free from any absorptions or disturbances by the Earth's atmosphere. Therefore, some large space telescopes and large space radio telescopes are planned. Diameter of payload bay of launch vehicle might be restriction for the size of such telescopes. That is the reason why structures larger than the payload bay have to be deployed or assembled onboard. Onboard assembling structure is better in surface accuracy and rigidity than deployable structure. We present a constitution of on-board assembling telescope reflector structure and its connecting mechanisms suitable for robot tasks. For assembling of such large structure, space robot has to move around on the structure. Power/signal lines, its connectors and grapple fixtures are needed on the structure for providing power/signal and foot restraints to the mobile robot arm. Compliant motions of robot are needed for constrained motion tasks such as grasping, attaching and mobile inchworm motion of onboard structure assembling. A new control method, active limp control of the robot arm joints, has high response and high stability because of their sensor/actuator collocation. So they are adequate to space robots for onboard assembling tasks. Constitutions of on-board assembling structure, a scenario of its assembling and control methods of the space robot are described in this paper. Characteristics of the new control methods and its suitability for onboard assembling tasks were confirmed by testing with using a prototype joint mechanism and its control system. The testing results and evaluation are also described in this paper.
The Communications Research Laboratory has been studying the inspection technology needed for the first step of 'Orbital Maintenance System' (OMS) that maintains space system by inspecting of satellites, re-orbiting useless satellites, and simply repairing satellites in orbit. In this paper, we introduce a re-configurable modular-type manipulator for space utilization, and its control algorithm for the inspection of satellites in orbit. The manipulator system is interconnected by a joint mechanism which can be connected and disconnected by simple robotic motion and also resist inertia during space operation. The modules are also specially designed for thermal, vacuum, and radiation conditions. The control processors are qualified in a piggyback flight on 2000. We have adopted a decentralized control algorithm for the redundant manipulator, which automatically adapts to the manipulator reconfigurations.