SEARCH · Engineering Papers

Results for “Trusses”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 235 records · Page 13

All sources NASA NTRS DOE OSTI

NASA NTRS1993

Using experimental modal data to detect damage in a space truss

The effects of damage on a model space truss are investigated using experimentally measured modes along with a procedure that uses the vibratory residual forces and a weighted sensitivity analysis to estimate the extent of mass and/or stiffness variations, where damage is characterized as a reduction in structural stiffness. It is shown that this approach yields excellent results for a four-bay space truss under consideration and was able to accurately predict not only the location of the damage region but also estimate the relative severity for three different configurations. In addition, the method was able to accurately detect and differentiate a shift in structural mass.

Tavares, R.↗

NASA NTRS1991

Dynamic characteristics of joint dominated space trusses

The rotational stiffness of hinge joints, and the gap of the joints applied in large deployable trusses, have been experimentally shown to have a significant role in determining such structures' dynamic behavior; an analytical validation of these results is presented for the case where linear rotation springs are used to model the hinge joints employed in a simple beam in trusses. The results obtained indicate that the natural frequencies of these structures depend not only on joint stiffness but also on joint location. Such gap parameters as gap size, stiffness, position, and excitation-force levels, are discussed with a view to a deeper understanding of their effects on a space interferometry system's simulated dynamic responses.

Shih, Choon-Foo↗

NASA NTRS1988

The 12-meter truss modal test

The objective of the 12-meter truss modal test is to experimentally determine the frequencies, damping, and mode shapes for the first 6 modes in both principle axes and to use this information to update the FEM. These objectives will lead us to our goal of actively controlling the flexible modes of the truss. A secondary objective is to evaluate our capabilities to ground test this class of structures.

Henderson, Douglas↗

NASA NTRS1958

Local Instability of the Elements of a Truss-core Sandwich Plate

The charts presented give the compressive buckling coefficients for a single-truss-core and a double-truss-core sandwich plate. These charts cover a wide range of sandwich proportions and may be used for sandwiches with unequal faces. They apply to inplane compressive loads acting parallel or perpendicular to the core direction or for various combinations of these loads. (author)

Anderson, Melvin S↗

NASA NTRS1926

Wing spar stress charts and wing truss proportions

In order to simplify the calculation of beams continuous over three supports, a series of charts have been calculated giving the bending moments at all the critical points and the reactions at all supports for such members. Using these charts as a basis, calculations of equivalent bending moments, representing the total stresses acting in two bay-wing trusses of proportions varying over a wide range, have been determined, both with and without allowance for column effect. This leads finally to the determination of the best proportions for any particular truss or the best strut locations in any particular airplane. The ideal proportions are found to vary with the thickness of the wing section used, the aspect ratio, and the ratio of gap to chord.

Warner, Edward P↗

NASA NTRS1994

Kinematic modeling of a double octahedral Variable Geometry Truss (VGT) as an extensible gimbal

This paper presents the complete forward and inverse kinematics solutions for control of the three degree-of-freedom (DOF) double octahedral variable geometry truss (VGT) module as an extensible gimbal. A VGT is a truss structure partially comprised of linearly actuated members. A VGT can be used as joints in a large, lightweight, high load-bearing manipulator for earth- and space-based remote operations, plus industrial applications. The results have been used to control the NASA VGT hardware as an extensible gimbal, demonstrating the capability of this device to be a joint in a VGT-based manipulator. This work is an integral part of a VGT-based manipulator design, simulation, and control tool.

Williams, Robert L., II↗

NASA NTRS1994

Applying transfer matrix method to the estimation of the modal characteristics of the NASA Mini-Mass Truss

It is beneficial to use a distributed parameter model for large space structures because the approach minimizes the number of model parameters. Holzer's transfer matrix method provides a useful means to simplify and standardize the procedure for solving the system of partial differential equations. Any large space structures can be broken down into sub-structures with simple elastic and dynamical properties. For each single element, such as beam, tether, or rigid body, we can derive the corresponding transfer matrix. Combining these elements' matrices enables the solution of the global system equations. The characteristics equation can then be formed by satisfying the appropriate boundary conditions. Then natural frequencies and mode shapes can be determined by searching the roots of the characteristic equation at frequencies within the range of interest. This paper applies this methodology, and the maximum likelihood estimation method, to refine the modal characteristics of the NASA Mini-Mast Truss by successively matching the theoretical response to the test data of the truss. The method is being applied to more complex configurations.

Shen, Ji-Yao↗

NASA NTRS1994

Joint for a variable geometry truss and method of constructing same

A joint and a method of constructing a joint for a variable geometry truss having a variable number of planes of variable length battens connected together in a triangular configuration, each plane being connected by six fixed length longerons in a Stewart platform configuration, are presented. The variable length battens allow the orientation of one end plane of the variable geometry truss to be changed to the other end plane in a controlled manner by selectively adjusting the lengths of the variable length battens. A main pivot joint pivotally connects two battens about a pivotal axis. A universal joint is pivotally connected to the main joint such that the pivotal axis of the universal joint is coextensive with the pivotal axis at the main joint. Two longerons are pivotally connected to the universal joint. Each longeron is thereby provided with three intersecting axes of rotation. Each longeron may include a revolute joint, allowing rotation about the longitudinal axis of the longeron.

Horner, Garnett C.↗

NASA NTRS1994

The development of a fiber optics communication network for controlling a Multidegree-Of-Freedom Serpentine Truss

The problem addressed by this report is the large size and heavy weight of the cable bundle, used for controlling a Multidegree-Of-Freedom Serpentine Truss Manipulator arm, which imposes limitations on the manipulator arm maneuverability. This report covers a design of an optical fiber network to replace the existing copper wire network of the Serpentine Truss Manipulator. This report proposes a fiber network design which significantly reduces the bundle size into two phases. The first phase does not require any modifications for the manipulator architecture, while the other requires major modifications. Design philosophy, hardware details and schematic diagrams are presented.

Andrawis, Alfred S.↗

NASA NTRS1993

Minimizing distortion in truss structures -- a Hopfield network solution

Distortions in truss structures can result from random errors in elemental lengths that are typical of a manufacturing process. These distortions may be minimized by an optimal selection of elements from those available for placement between the prescribed nodes -- a combinatorial optimization problem requiring significant investment of computational resource for all but the smallest problems. The present paper describes a formulation in which near-optimal element assignments are obtained as minimum energy, stable states, of an analogous Hopfield neural network. This requires mapping of the optimization problem into an energy function of the appropriate Lyapunov form. The computational architecture is ideally suited to a parallel processor implementation and offers significant savings in computational effort. A numerical implementation of the approach is discussed with reference to planar truss problems.

Fu, B.↗

NASA NTRS1995

Truss Fastener Operable By Robot

Fastener assembly for use in erecting truss structure assembled by robot equipped with one arm and one gripper. Easier for robot or human technician to build structure in outer space or on Earth. Assembly features extremely large capture envelope; accommodates initial lateral misalignments of truss members of as much as 0.4 in. and rotational misalignments large as 28 degrees and still produces sound structural connection. Chuck key is only tool required.

Parma, George E.↗

NASA NTRS1992

Passive damping augmentation of flexible beam-like lattice trusses for large space structures

A Timoshenko beam continuum model is developed to determine the transient response of a beam-like latticed large space structure, subjected to a unit impulse. It is demonstrated that an increase in diagonal stiffness, on account of the stiffness of the vertical girder, leads to a rise in the transverse shear rigidity. This results in higher natural frequencies and reduction in peak displacement. In addition, in an asymmetrical truss configuration, coupling between the extensional and shear modes raises the maximum peak displacement compared with that obtained for a symmetrical truss. The model is modified to investigate the introduction of passive damping in the form of several dynamic vibration absorbers. A unique absorber parameter optimization procedure, based on the classical steady-state criteria, is used to tune the absorbers, having a total allocated mass budget of 10%, to the first two frequencies of the latticed structure. It is found that inclusion of transverse shear rigidity as a design parameter in damping augmentation studies reduces settling time for predetermined maximum peak displacements.

Cohen, K.↗

NASA NTRS1996

Truss Structure Could Be Folded For Transport

Proposed truss structure comprises cubical bays and folded for compactness during transport. When folded, truss 1/25.6 as long as when fully extended. Conceived for transport and deployment in outerspace, suitable for terrestrial structures that must be transported compactly and erected quickly.

Theer, Douglas S.↗

NASA NTRS2000

STS-92 Z-1 Truss Overview

Robert Galvez, Launch Package Manager, gives an overview of the launch package of the STS-92 Discovery mission (Z-1 Truss, PMA-3, DDCU, etc.), and gives details on the configuration and equipment positioning on the Z-1 Truss. Simulations show the installation of the DDCU (DC to DC power converter) and the S-band Antenna.

Source record↗

NASA NTRS2004

Exploratory Investigation of Failure Mechanisms in Transition Regions between Solid Laminates and X-cor(registered tm) Truss Sandwich

Small sub-component specimens consisting of solid laminates at the ends that transition to X-cor(R) truss sandwich in the center, were tested in a combination of three point bending, uni-axial tension, and combined tension and bending. The failure process in the transition region was documented for each loading using digital video and high-resolution cameras. For the 3-point bending tests, most of the deformation occurred in the solid laminate regions on either end of the specimen. Some pin debonding from the skin of the X-cor(R) truss sandwich was observed in the transition region and was accompanied by audible "pings" throughout the loading. Tension loaded specimens failed in the sandwich skin in the middle of the gage length, accompanied by separation of the sandwich core from the back skin and by delamination between the top skin and bottom skin at the transition region. The pinging associated with pin debonding occurred as the load was increased. However, the frequency of the pinging exceeded any visual observations of pin debonding in the video of the transition region. For specimens tested in combined tension and bending, the greatest amount of pinging occurred during initial application of the axial load. High-resolution images in the transition region indicated that the pinging corresponded to pins debonding and buckling due to the through-thickness Poisson contraction of the specimen. This buckling continued to a much smaller extent as the transverse load was applied.

OBrien, T. Kevin↗

NASA NTRS2007

Adaptive Control of Truss Structures for Gossamer Spacecraft

Neural network-based adaptive control is considered for active control of a highly flexible truss structure which may be used to support solar sail membranes. The objective is to suppress unwanted vibrations in SAFE (Solar Array Flight Experiment) boom, a test-bed located at NASA. Compared to previous tests that restrained truss structures in planar motion, full three dimensional motions are tested. Experimental results illustrate the potential of adaptive control in compensating for nonlinear actuation and modeling error, and in rejecting external disturbances.

Yang, Bong-Jun↗

NASA NTRS2007

Adaptive Control of Truss Structures for Gossamer Spacecraft

Yang Bong-Jun↗

NASA NTRS2008

Optimization of Stability Constrained Geometrically Nonlinear Shallow Trusses Using an Arc Length Sparse Method with a Strain Energy Density Approach

A technique for the optimization of stability constrained geometrically nonlinear shallow trusses with snap through behavior is demonstrated using the arc length method and a strain energy density approach within a discrete finite element formulation. The optimization method uses an iterative scheme that evaluates the design variables' performance and then updates them according to a recursive formula controlled by the arc length method. A minimum weight design is achieved when a uniform nonlinear strain energy density is found in all members. This minimal condition places the design load just below the critical limit load causing snap through of the structure. The optimization scheme is programmed into a nonlinear finite element algorithm to find the large strain energy at critical limit loads. Examples of highly nonlinear trusses found in literature are presented to verify the method.

Hrinda, Glenn A.↗