Deployment Subsystem and Attitude Control Subsystem of STARS-I

Deployment subsystem is one of important subsystems for STARS-I mission to verify TSR technology on orbit, and it is mounted on mother satellite. Its main objectives are to give an initial velocity of daughter satellite for deployment, and to deploy and to retrieve daughter satellite by tether control.

Eject unit makes an initial velocity of daughter satellite, here mother satellite has a velocity due to reaction force. Hook attached to motor presses the spring, and hook unlatch the spring, then spring is extended by its potential energy. Thus, bowl supported by the spring gives an initial velocity of daughter satellite.

Deployment unit controls tether deployment and retrieval. It contains of tether reel, motor, and the torque transmission device, which keeps constant torque. Tether can avoid excessive tension and its sudden change. Fundamentally, tether deployment and retrieval is controlled by motor velocity control. When excessive tension is applied on tether, differential rotation of tether reel and motor are occurred due to the permanent wave torque.

Attitude control subsystem is very important to employ attitude control function of Tethered Space Robot (TSR). Attitude of TSR is controlled by tether position and tensions of the arm and mass centre of the robot. Since relation of tether extension position and lines of tether attachment point and mass centre of the robot is operated by arm motion, torque due to tether tension acting on the robot. There fore the two degrees of freedom for arm motion around the tether extension line axis, and TSR attitude can be controlled around two vertical axis of tether extension line.

Two motors are equipped on daughter satellite in attitude control subsystem. Motor 1 is mounted on the main body of daughter satellite, and actuates the bowl. Motor 2 is mounted on the bowl, and actuates the arm. As a result the arm end attached to tether can be places in spatial space, and then attitude control around tether extension line is possible.

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