Construction Of Large Space Structures Research Articles

Design and Verification of Continuous Tube Forming Process Parameters for PEEK-Based Rod Aimed at Space Manufacturing Applications

To meet the in-orbit construction needs of super-large spacecraft for ultra-long rod structures, this paper proposes an innovative on-orbit roll forming method for polyetheretherketone (PEEK)-based rod stock. This method ingeniously integrates temperature gradient control into a continuous deformation surface cavity design to achieve an efficient forming of resin rod components. A parametric model of the forming die cavity was established based on the comprehensive bending and downhill methods, and the boundary conditions for the temperature distribution gradient within the cavity were determined. Through the simulation and analysis of the PEEK rod curling and stitching forming process, the influence of the cavity configuration parameters on the forming load was determined. By constructing a test platform for the roll forming characteristics of resin rod components, the effects of different forming methods, stitching temperatures, and feed rates on forming quality and load were verified, and the main factors affecting the width of the welding zone, the roundness of the rod, and the straightness of the weld were analyzed. Experimental results show that the proposed continuous roll forming scheme can achieve an efficient and continuous forming of resin rod structures. When the length of the member is processed to 300 mm, at a formed rod diameter of 20 mm, by employing a cavity deformation zone length of 210 mm, a cavity clearance of 0.1 mm, a sheet width of 61 mm, a feed rate of 1 mm/s, and a sealing zone temperature setting of 335 °C, optimal rod forming quality can be achieved, characterized by a straightness error of 0.0133 ± 0.005 mm and a roundness error of 0.19 ± 0.07 mm. The proposal of this scheme provides a reliable basis for the continuous manufacturing of rod structures in the on-orbit construction of large space structures in terms of both the scheme and the parameter selection.

Dynamics and control of robotic spacecrafts for the transportation of flexible elements

The technology of robotic spacecrafts has been identified as one of the most appealing solutions to the on-orbit construction of large space structures in future space missions. As a prerequisite of a successful on-orbit construction, it is needed to use small autonomous spacecrafts for the transportation of flexible elements. To this end, the paper presents an energy-based scheme to control a couple of robotic spacecrafts carrying a flexible slender structure to its desired position. The flexible structure is modelled as a long beam based on the formulation of absolute nodal coordinates to account for the geometrical nonlinearity due to large displacement. Meanwhile, the robotic spacecrafts are actuated on their rigid-body degrees of freedom and modelled as two rigid bodies attached to the flexible beam. The energy-based controller is designed using the technique of energy shaping and damping injection such that translational and rotational maneuvers can be achieved with the suppression of the flexible vibrations of the beam. Finally, numerical case studies are performed to demonstrate the proposed schemes.

Experimental Verification of Periodic Libration of Tethered Satellite System in Elliptic Orbit

Tethered satellite systems are often considered as revolu- tionary new technologies capable of solving complex tasks for challenging future space missions such as construction of large space structures, momentum exchange [1], debris elimination [2], artificial gravity generation by rotational motion, and so on [3]. To make the application of tethered satellite systems feasible, their dynamics and control must be comprehensively understood and properly addressed.

A Kinematic Approach to Determining the Optimal Actuator Sensor Architecture for Space Robots

Autonomous space robots will be required for such future missions as the construction of large space structures and repairing disabled satellites. These robots will need to be precisely controlled. However, factors such as manipulator joint/actuator friction and spacecraft attitude control thruster inaccuracies can substantially degrade control system performance. Sensor-based control algorithms can be used to mitigate the effects of actuator error, but sensors can add substantially to a space system’s weight, complexity, and cost, and reduce its reliability. Here, a method is presented to determine the sensor architecture that uses the minimum number of sensors that can simultaneously compensate for errors and disturbance in a space robot’s manipulator joint actuators, spacecraft thrusters, and reaction wheels. The placement and minimal number of sensors is determined by analytically structuring the system into “canonical chains” that consist of the manipulator links and spacecraft with force/torque sensors placed between the space robot’s spacecraft and its manipulators. These chains are combined to determine the number of sensors needed for the entire system. Examples of one- and two-manipulator space robots are studied and the results are validated by simulation.

Implementation algorithms for self-identification of adaptive structures with variable geometric properties

On-orbit vibration testing is one of the issues for in-orbit construction of large space structures because of structural variations during assembly. Variable geometry truss structures would be the candidates as the tools for the in-orbit construction. This paper proposes structural identification algorithms for implementing self-identification of variable geometry truss structures. Using the implementation algorithms, the variable geometry truss determines quasi-static changes of their own geometric parameters to enhance the lack of vibration modes with limited excitation locations for on-orbit vibration testing. The proposed algorithms are numerically examined through the identification of the stiffness matrix of a two-dimensional variable geometry truss with a single variable length member and a single excitation location. We assumed that all the nodes of the truss structure were fully instrumented for measuring mode shape and modal frequency. In the numerical experiments, unknown stiffness matrix of finite element model corresponding to the variable geometry truss is identified under the assumption that exact mass matrix is given using finite element model. It is found that increasing the number of geometry changes can enhance the lack of vibration modes, and the identification error of stiffness matrix is reduced accordingly. The sensitivity of identification accuracy to the modeling error in given mass matrix is also addressed. Furthermore, we discuss a method for selecting sufficient number of geometry changes by considering the convergence of the norm of identified stiffness matrix.

Symmetric Motion Control for Adaptive Structure Based Construction of Large Space Structures

Covers advancements in spacecraft and tactical and strategic missile systems, including subsystem design and application, mission design and analysis, materials and structures, developments in space sciences, space processing and manufacturing, space operations, and applications of space technologies to other fields.

炭素繊維強化複合材ケーブルの直接通電による成形と引張特性に関する研究

For the construction of large space structures, onorbit fabrication of cable net structures is proposed. This is accomplished by transporting coiled stock of prepreg of CFRP cable to the orbit from the earth and curing it by means of resistance heating whose operating power is supplied by solar electric system. Laboratory tests indicate that CFRP cables can be cured uniformly and precisely with the specified cure cycle by passing low voltage current through them. Tensile tests of CFRP cables cured by resistance heating as well as those of uncured ones have also been performed and the results show that cured cables exhibit tensile strength and stiffness which are about two times higher than those of uncured ones. In preparing for tensile specimens of uncured cables, it has been found that any part of CFRP cables can be left uncured by the present method without changing curing process. At these uncured portions, they can be bent for folding and be tied to other structural members with knots without using mechanical hinges or joints.

Adaptive Structures Research at ISAS, 1984-1990

This article reviews the research and development on adaptive structures and intelligent structural systems done by the structures and structural dynamic group at the Institute of Space and Astronautical Science (ISAS) from 1984 to 1990. Our activity is closely linked to the practical needs for actively controlled structures on board scientific satellites and interplanetary vehicles which ISAS launches annually. The subjects described here are: the proposal of novel structural concepts such as the variable geometry truss, the adaptive structure and the tension truss antenna; the proposal of vibration control schemes for flexible structures and the shape control scheme for precision antenna reflectors; and the study on construction of large space structures by assembling adaptive structures.

Development of advanced composite materials and geodetic structures for future space systems

The results of recent work accomplished under a NASA Johnson Space Center contract to develop an advanced composite geodetic beam and beam fabrication machine for the on-orbit construction of large space structures are given in this paper. Testing to determine mechanical, physical, thermal and electrical property characteristics of a near thermally inert advanced composite material for fabrication of geodetic structures is described and results are presented. Development testing of full-scale segments of geodetic structures fabricated with this material is discussed, along with results of a test to demonstrate structural feasibility of the cylindrical geodetic beam's end attachment design. Future tests of a long geodetic beam with conical end attachments are described. These latter tests are to verify the ability of geodetic structures to withstand mechanical and thermal loading environments of space.

Computer Coordination of Limb Motion for Locomotion of a Multiple-Armed Robot for Space Assembly

Consideration is given to a possible robotic system for the construction of large space structures, which may be described as a multiple general purpose arm manipulator vehicle that can walk over the structure under construction to a given site for further work. A description is presented of the locomotion of such a vehicle, modeling its arms in terms of a currently available industrial manipulator. It is noted that for whatever maximum speed of operation is chosen, rapid changes in robot velocity create situations in which already-selected handholds are no longer practical. A step is added to the 'free gait' walking algorithm in order to solve this problem.