The Engineering Test Satellite VII of the National Space Development Agency of Japan, launched in 1997, has a 2-m-long robot arm to conduct space robot technology experiments. The robot arm was teleoperated from the ongroundcontrol stationusing a communication link througha data relay satellite in geostationaryorbit. Tomaintain satellite attitude stability and the direction of the intersatellite communicationantenna vs the robot arm’s motion, coordinated satellite attitude control and coordinated robot-arm control were introduced. Coordinated satellite attitude control was realized by adding feedforward angular momentum cancellation in addition to traditional feedback attitude control. The coordinated robot-arm control was to manage the robot arm’s angularmomentum within the capability of the satellite attitude control system. Gain scheduling control was also tested to reduce the satellite attitude error that was caused by the robot arm motion and showed good performance. With these controls, the onboard robot arm conducted various tasks safely and successfully. Robot-arm motions while the satellite attitude was not actively controlled were also tried. However, it is shown that the robot-arm motion on a free-motion satellite was not easy due to the gravity-gradient torque and other disturbance torques.
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