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Hanks, B. R.

Publications and source records attributed to Hanks, B. R..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Structure redesign for improved dynamic response

The concepts of multivariable control design are used to redesign structures represented by lumped parameter models. When the mass is held constant, the changing of passive structural members is mathematically equivalent to an output feedback decentralized control problem. When the mass is also allowed to change, a generalization of the output feedback formulation is required. The design objective is to minimize the changes in the structure required to simultaneously satisfy inequality constraints on both the root-mean-square and absolute value of the dynamic response of each output. An alternative objective treated is to minimize the root-mean-square of the dynamic response subject to inequality constraints on the changes allowed in each structural member. Examples illustrate both procedures.

Skelton, R. E.↗
NASA NTRS1985

Control of Flexible Structures (COFS) Flight Experiment Background and Description

A fundamental problem in designing and delivering large space structures to orbit is to provide sufficient structural stiffness and static configuration precision to meet performance requirements. These requirements are directly related to control requirements and the degree of control system sophistication available to supplement the as-built structure. Background and rationale are presented for a research study in structures, structural dynamics, and controls using a relatively large, flexible beam as a focus. This experiment would address fundamental problems applicable to large, flexible space structures in general and would involve a combination of ground tests, flight behavior prediction, and instrumented orbital tests. Intended to be multidisciplinary but basic within each discipline, the experiment should provide improved understanding and confidence in making design trades between structural conservatism and control system sophistication for meeting static shape and dynamic response/stability requirements. Quantitative results should be obtained for use in improving the validity of ground tests for verifying flight performance analyses.

Hanks, B. R.↗
NASA NTRS1985

Dynamic verification of very large space structures

A research program in spacecraft structures, structural dynamics, and controls verification using a relatively large, flexible beam as a focus is introduced. This research effort addresses fundamental problems applicable to the verification of large, flexible space structures and combines ground tests, flight behavior prediction, and instrumented orbital tests. The program is expected to produce quantitative results for use in improving the validity of ground tests for verifying flight performance analyses.

Hanks, B. R.↗
NASA NTRS1985

Dynamic verification of very large space structures

The dynamic verification of spacecraft relies heavily on ground-based tests. These tests usually simulate flight environments or validate analytical models used in establishing design loads and in designing control algorithms. They also provide security against failures resulting from unanticipated or unmodeled hardware behavior. Future orbital antennas, space stations, and solar power systems are likely to be of sizes difficult to test using current ground test technology. In addition to size, other factors such as low natural frequencies, lightweight construction, and the presence of many structural joints, cause significant sensitivity of the test process to the earth-gravity environment. Yet, accuracy requirements on the verification process will be more stringent because of modern flexible-structure control approaches. This paper describes some of the problems and discusses research on potential solutions. The importance of an integrated ground test, analysis, and flight test program is emphasized. An ongoing research program of this type focusing on a 60-meter, deployable, truss-beam test article is described.

Hanks, B. R.↗
NASA NTRS1985

Control of Flexible Structures (COFS) Flight Experiment Program

The Control of Flexible Structures (COFS) Flight Experiment Program consists of a series of four Shuttle-attached experiments specifically designed to systematically evaluate algorithms and techniques for on-orbit systems identification and flexible body control of large flexible structures, and as such, develops the enabling technologies for future NASA missions such as the evolutionary Space Station and large orbital antennas. These flight experiments are conducted on 1-year centers starting in 1989. This paper presents a description of the test article for the first two flights (COFS-I) and a discussion of the strategy for conducting the various experiments. A guest investigator program provides the opportunity for the research community to participate in the structures/controls research associated with the multi-flight COFS Program.

Fontana, A.↗
NASA NTRS1984

Deployable beam flight experiment (MAST)

Improvement of technology of space systems control is discussed. Future space systems such as large antennas or a space station may have dimensions on the order of 30 m to 200 m, yet their basic structures may be relatively lightweight and flexible, making ground tests for loads, controls analyses, and design verifications questionable if not impossible. Abandoning the extensive ground test and analysis verification program that led to the success of previous spacecraft is not a sensible option; making it meaningful using current technology will require inefficient, ultraconservative structure and control designs. New test methods are outlined.

Hanks, B. R.↗
NASA NTRS1983

Large space structures raise testing challenges

The testing approaches and techniques necessary for combined ground and space verification for large space structures (LSS) to be deployed and assembled in space are explored. The size of LSS precludes full ground tests, thereby requiring assemblies, components, and their interactions to be examined on orbit. Ground tests involving drop tests and zero-g aircraft flights can be performed with scale models, but need computational compensation to eliminate gravitational and torque effects that do not occur in space. Structural rigidity also varies from ground to space, and can partly be accounted for in ground tests by using cable supports, although numerical modelling must remove the effects of the cables' presence. Long-term funding is recommended for on-orbit tests of components in order to build a data base for later testing and actual construction of LSS.

Hanks, B. R.↗
NASA NTRS1983

Structural design for dynamic response reduction

A computer program for redesigning structural modes to reduce response has been initiated. The linear regulator approach in modal coordinates has been implemented. It is noted that the transformation of solution to physical structure is a major problem. It is concluded that the solution of stiffness equations and damping equations can be done separately as NXN set of (matrix Riccati) equations.

Hanks, B. R.↗
NASA NTRS1983

A study of the effects of a cubic nonlinearity on a modern modal identification technique

The effect of a geometric nonlinearity on the Ibrahim Time Domain (ITD) modal data analysis technique has been studied using two analytically derived models and one laboratory model. Response data for the three models were analyzed by the ITD method. Indicators of nonlinear response were found which include harmonically related frequencies with repetitive mode shapes, clusters of frequencies in a narrow band around each harmonic, and variations in frequency with amplitude of oscillation. Also,for the cases studied, the presence of a nonlinearity has no detrimental effect on identifying linear responses. A potential for applying the algorithm to the identification of a certain class of nonlinear system was indicated.

Horta, L. G.↗
NASA NTRS1978

Comparison of modal test methods on the Voyager payload

A comparison of the performance of modern modal data analysis methods on test data from the Voyager Jupiter/Saturn payload is presented. Four different test/data-analysis combinations are compared - multiple-point sine excitation tests, single-point random-excitation tests using two different techniques of manipulating Fourier transform data, and a time-domain method for analyzing random data. Results indicate that all four methods can give comparable results. Of the four, the time-domain approach detects more modes in the test data and, at the same time, shows the greatest promise for reducing the time and cost of modal testing.

Hanks, B. R.↗