Telerobotics with large time delays-the ROTEX experience

The paper discusses delay-compensating techniques when operating a space robot from ground or from a another remote spacecraft. These kind of techniques have been a key element in the space robot technology experiment ROTEX that has successfully flown with shuttle COLUMBIA end of April 93. During this “spacelab-D2”-mission for the first time in the history of space flight a small, multisensory robot (i.e. provided with modest local intelligence) has performed prototype tasks on board a spacecraft in different operational modes, namely preprogrammed (and reprogrammed from ground), remotely controlled (teleoperated) by the astronauts, but also remotely controlled from ground via the human operator as well as via machine intelligence. In these operational modes the robot successfully closed and opened connector plugs (bayonet closure), assembled structures from single parts and captured a free-floating object. This paper focuses on the powerful delay-compensating 3D-graphics simulation (predictive simulation) concepts that were realized in the telerobotic ground station and which allowed the authors to compensate delays of up to 7 sec e.g. when grasping the floating object fully automatically from ground