Johann Heindl

Sensor-based space robotics-ROTEX and its telerobotic features

In early 1993 the space robot technology experiment ROTEX was flown with space-shuttle Columbia. A multisensory robot onboard the spacecraft successfully worked in autonomous modes, teleoperated by astronauts, as well as in different telerobotic ground control modes. These included online teleoperational and telesensor-programming: a task-level oriented programming technique involving learning-by-showing concepts in a virtual environment. The robots key features were its multisensory gripper and the local sensory feedback schemes that are the basis for shared autonomy. The corresponding man-machine interface concepts, which use a six-degree-of-freedom non-force-reflecting control ball and visual feedback to the human operator, are explained. Stereographic simulation on the ground was used to predict not only the robots free motion but even the sensor-based path refinement onboard. Prototype tasks performed by this space robot were the assembly of a truss structure, connecting/disconnecting an electrical plug (orbit replaceable unit exchange), and grasping free-floating objects. >

ROTEX-the first remotely controlled robot in space

In April 1993 for the first time in the history of space flight, a small multisensory robot performed a number of prototype tasks on-board a spacecraft (spacelab D2 on shuttle COLUMBIA) in different operational modes that are feasible today, namely preprogrammed remotely controlled operations by the astronauts using a control ball and a stereo TV-monitor, as well as remotely controlled from ground via the human operator and 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. Several key technologies have made this space robot technology experiment ROTEX a big success: multisensory gripper technology, local (shared autonomy) sensory feedback control concepts, and the powerful delay-compensating 3D-graphics simulation (predictive simulation) in the telerobotic ground station. This paper focusses on the tele-sensor-programming approach and the predictive simulation used for remote ground control.<<ETX>>

Predictive and knowledge-based telerobotic control concepts

The problems that arise when sensor-controlled robots in space are teleoperated from ground stations are discussed. A supervisory control concept is described that makes it possible to realize shared control between teleoperator and sensor-controlled robot in a variety of configurations. Predictive 3D computer graphics currently seems to be the only way to cope successfully with the problem of transmission-time delays of several seconds. Appropriate estimation schemes in combination with knowledge-based world modeling are outlined, which include models of the delay lines, the robot, moving objects, etc., and which derive the necessary updates from sensory data as they are sent down from the spacecraft to earth (e.g. via real-time stereo vision). The space robot technology experiment Rotex scheduled for the next German Spacelab mission (2D) is taken as a basis for the problem description.<<ETX>>

A Sensor-based Telerobotic System for the Space Robot Experiment ROTEX

The space robot technology experiment ROTEX to fly with the next spacelab mission D2 in 1993 provides a sensor-controlled robot which is supposed to work in an autonomous mode, teleoperated by astronauts, and teleoperated from ground. The robots key features are its multisensory gripper and the local („shared”) sensory feedback schemes. The corresponding man-machine interface concepts using a 6 dof control ball and visual feedback to the human operator are explained. Sensory simulation on ground using advanced stereo graphics is supposed to predict the sensor based path refinement on board, while realtime fusion of stereo images and laser range information helps to predict the motion of floating objects to be grasped. The telesensorprogramming concept is explained as well as the learning schemes involved.

The DLR Robot Motion Simulator Part I: Design and setup

In recent years a new generation of motion simulators, based on serial kinematics industrial robots, emerged as alternative to the currently prevalent Steward-platforms. This paper presents the newest addition to this: The DLR Robot Motion Simulator.

Reactionless Control for two Manipulators Mounted on a Cable-Suspended Platform

The dynamics and control of a cable-suspended, two-arm robotic system are developed for an entertainment application. One manipulator arm is controlled to fulfil a user defined task. The second arm is then controlled to compensate for the disturbances on the cable-suspended platform arising from the motion of the first. Model-based feedforward control, stemming from the momentum conservation equations of a free-floating robot, is developed for the motion compensation problem. Furthermore, due to model uncertainty, sensor-based feedback control is introduced, to account for undesired oscillatory motions of the system. The latter control problem reduces to the dissipation of the oscillatory energy of the system, by means of adequate robot control. Both control methods are implemented and tested on an experimental set-up

ROTEX — Die Telerobotik-Konzepte des ersten Roboters im Weltraum

Ende April 93 fuhrte erstmalig in der Geschichte der Raumfahrt bei der Spacelab-D2-Mission ein kleiner, mit lokaler, ”multisensorieller” Intelligenz ausgestatteter Roboter an Bord eines Raumfahrzeuges prototypische Aufgaben vollig flexibel in den unterschiedlichsten Betriebsarten durch; namlich vorprogrammiert (und wahrend der Mission vom Boden aus umprogrammiert), von Astronauten uber die sog. DLR-Steuerkugel und einen TV-Stereo-Monitor ferngesteuert, aber auch direkt vom Boden aus ferngesteuert, sei es durch den Menschen oder rein maschinell. Der Roboter muste in diesen Betriebsarten Steckverbindungen in Form eines Bajonett-Verschlusses losen bzw. wiederherstellen, mechanische Strukturen zusammen- bzw. auseinanderbauen und ein freifliegendes Objekt einfangen.