An orbit maintenance system equipped with a robot is expected to rescue satellites enabling their life spans to be prolonged and suppressing the amount of space debris. We are studying a system that is capable of the assembly, capture, diagnosis and repair of small satellites in orbit. A ground model of the orbit maintenance vehicle, which is equipped with a pair of robot arms, has been developed for these studies. In this paper, we describe a ground experiment for capturing an uncontrollably rotating satellite using the robot. The capture experiments were performed in sensor-dased autonomous control mode. We demonstrated that the vehicle flies toward the satellite, which is rotating in a test facility simulating 3-dimensional space, by measuring the relative position and attitude through image processing of a target marker, and then captures the handrail of the satellite with a hand having an adaptive mechanism by means of predictive visual servo tracking of the robot arm.

View full abstract

We developed two solar paddle actuators for a small satellite using six shape memory alloy (SMA) springs. These actuators can orient the solar paddle alone toward the sun, and are equipped with a counterweight to compensate for the rotating motion of the small satellite in microgravity. One actuator is a prototype that was used in experiments conducted in microgravity and in vacuum. The prototype measures 100 mm in diameter and 127 mm in height, and weighs approximately 660 g including the counterweight (340 g). The counterweight is effective for compensating for the rotating motion of the small satellite in microgravity. Motion repetition experiments in vacuum were conducted to investigate the degradation properties of the SMA. We found that the prototype required the following improvements: (1) to avoid the shadow of the satellite itself, the SMA springs should be located as far from the satellite as possible, (2) offset angle and speed-up gears are required, and (3) some floating or flexible parts should be fixed so that they will not be affected by launch vibration. To this end, a modified actuator was developed. We introduce the modified actuator and show some results of motion experiments.

View full abstract