Space Manipulator System Research Articles

Space Robotics Researches at Electrotechnical Laboratory: Dexterous EV Robot Technology

Studies on basic technologies on space robots have been conducted at the Electrotechnical Laboratory (ETL) since 1983. The research emphasizes on developing key technologies of dexterous extravehicular robots. It is categorized into four areas: space adaptive mechatronics; telerobotics; on-board skill technology; and motion control of free flying robots in 0-gravity. We have been developing several pilot models such as a dexterous space manipulator system working in a vacuum, a graphic simulator augmented teleoperation system for long-distance robots, a smart end-effector for a large space manipulator arm, and an astronaut reference flying robot. This paper overviews the space robotics research efforts at ETL and presents a current topic of the precise space telerobotics experiment on ETS-VII.

Jacobian control for space manipulator

Parlaktuna, O., Cook, G.E., Strauss, A.M. and Fernandez, K., Jacobian control for space manipulator, Robotics and Autonomous Systems, 11 (1993) 35–44. To control robot or teleoperated manipulators in space, the motion of the satellite (which is actually the base of the manipulator) which will move due to the force exerted by the moving manipulator, must be considered. Most of the algorithms developed to control a robot manipulator assume that the manipulator is connected to a fixed base. Since the satellite moves due to the motion of the robot manipulator, the control schemes developed for fixed-base manipulators cannot be used for space robots and telerobots. In this paper, using a modified resolved motion rate control and angular momentum conservation law, a generalized Jacobian matrix is derived to control the space manipulator. It is shown that a manipulator controlled in this manner follows a prescribed path independent of the motion of the satellite.

Dynamic Singularities in Free-Floating Space Manipulators

Dynamic Singularities are shown for free-floating space manipulator systems where the spacecraft moves in response to manipulator motions without compensation from its attitude control system. At a dynamic singularity the manipulator is unable to move its end-effector in some inertial direction; thus dynamic singularities must be considered in the design, planning, and control of free-floating space manipulator systems. The existence and location of dynamic singularities cannot be predicted solely from the manipulator kinematic structure because they are functions of the dynamic properties of the system, unlike the singularities for fixed-base manipulators. Also analyzed are the implications of dynamic singularities to the nature of the system’s workspace.

Minimizing spacecraft attitude disturbances in space manipulator systems

This paper presents a technique called the enhanced disturbance map to plan space manipulator motions that will result in relatively low spacecraft disturbances. This subject is of significant concern because future robotic systems used in space may encounter problems due to the dynamic disturbances imposed on their spacecraft by their manipulator motions. Although a spacecraft's attitude control reaction jets can compensate for these dynamic disturbances, jet fuel is a limited resource and excessive disturbances would limit the life of a system. The enhanced disturbance map can aid in understanding this complex problem and in the development of algorithms to reduce disturbances, including ones that use manipulator redundancy to eliminate the disturbances.

On the nature of control algorithms for free-floating space manipulators

It is suggested that nearly any control algorithm that can be used for fixed-based manipulators also can be employed in the control of free-floating space manipulator systems, with the additional conditions of estimating or measuring a spacecraft's orientation and of avoiding dynamic singularities. This result is based on the structural similarities between the kinematic and dynamic equations for the same manipulator but with a fixed base. Barycenters are used to formulate the kinematic and dynamic equations of free-floating space manipulators. A control algorithm for a space manipulator system is designed to demonstrate the value of the analysis. >

The Kinematics and Dynamics of Space Manipulators: The Virtual Manipulator Approach

Future robotic manipulator systems will be required to per form complex tasks in space such as satellite repair. These robotic manipulators will encounter a number of kinematic, dynamic, and control problems caused by the dynamic coup ling between the manipulators and its spacecraft. This dy namic coupling also makes it difficult to analyze these sys tems. This paper introduces a new analytical modeling method for space manipulators called the Virtual Manipula tor (VM), which has a fixed base in inertial space at a point called a Virtual Ground. The kinematics and dynamics of the manipulator, spacecraft, and payload can be described relatively easily in terms of the VM. With its fixed base, the Virtual Manipulator is shown to have the potential to be an effective aid for the analysis, design, and development of future space manipulator systems.

Design techniques for robots: Space applications

This article is based on a report commissioned by the European Space Agency and available as ESA CR(P)2048. It deals with analytical techniques and technologies required for the design and developed of robotic manipulators in space. In general, it has appeared that many techniques developed for terrestrial applications may be used for a space manipulator system. However, the space environment introduces constraints, requiring considerable modifications to the techniques identified. In short these can be summarized as • Increased requirement for system autonomy and realibility • Different mass-velocity operating regime • Adaptation to limited (on-board) computing power.

Control Aspects of a European Space Manipulator System

This paper is based on the results of an ESA study on “Design Techniques for Robots (Space Applications)”, performed by Fokker and subcontractors ACEC, Tecnomatix and NLR. The aim of the study was to review existing design techniques for robots on their applicability for design and development of a space manipulator system. In this paper attention is paid to the definition and the design approach of the overall control system. Special emphasis is given to the control elements dealing with task definition, path construction and on-board control. Also a number of on-board implementation aspects are considered . Furthermore a comparison is made with the Remote Manipulator Control, as used on the Space Shuttle.