Michael L. Drake

Jitter suppression experiment active and passive damping system requirements and verification

The University of Dayton Research Institute (UDRI) is teamed with McDonnell Douglas Aerospace (MDA) to develop and fly a NASA IN- STEP experiment entitled Jitter Suppression Experiment (JSX). The JSX will demonstrate a combined active/passive vibration control system on an actual full scale space structure. This paper will present the impact of the JSX system requirements on the passive and active vibration control system and verification that these requirements were met. The basic JSX system requirements are broken down into two categories, shuttle requirements and experiment requirements.

Jitter suppression experiment passive damping design cycle

The University of Dayton Research Institute is teamed with McDonnell Douglas Aerospace to develop and fly a NASA IN-STEP experiment entitled Jitter Suppression Experiment (JSX). The JSX will demonstrate a combined active/passive vibration control system on an actual full scale space structure. This paper presents the details of the design of the passive control system to be applied to six graphite/epoxy support tubes for a gimballed telescope assembly (GTA) and the results of concept development laboratory tests. The most promising damping concepts for tubes such as the GTA truss tubes were constrained layer dampers and tuned dampers. The advantages and disadvantages of each of these damping concepts and the reasons for choosing a constrained layer concept are discussed. To verify the effectiveness of the passive damping design and to determine the constrained layer damping system effectiveness for axial modes, a finite element analysis of a single truss tube with the proposed constraining layer design was performed. A laboratory simulation was designed, developed, and evaluated to verify the analysis.

Damping designs for rotating blades

This paper presents the results of the first phase of an effort to determine the effects of centrifugal forces on viscoelastic damping concepts applicable to rotating components. The design of the experimental test specimen will be discussed along with the analytical methods used to design and evaluate damping concepts for the test specimen. A blend of classical analysis, 6th order beam theory, and finite element analysis was used. The analytical effort was divided into two tasks. The first task was to define the design of the test specimen such that: (1) a meaningful test could be conducted in the spin test facility; (2) damping concepts could be designed into the test specimen; and (3) manufacturing time and cost were reasonable. The second task of the effort was to complete a trade study evaluating various damping concepts. The trade study evaluated damping effectiveness, survivability, manufacturability, and damping material availability. The design parameters evaluated included: (1) pocket size, orientation, and number; (2) pockets with and without floating constraining layers; (3) damping concept creep potential; and (4) stresses in the test specimen due to centrifugal loading. This paper will detail the analysis techniques used, the trends found in the design parameters, and the final designs chosen for the test effort.

Trade study on damping curved airfoil-shaped plates

This paper discusses the results of a project which focused on the development and evaluation of internal damping concepts applicable to damping curved airfoil shaped plates. Thirteen damping concepts were analyzed. The analysis was completed using an FEA. The initial analysis computed modal damping for the first four modes of the structure. As the study progressed, the final analysis on the best two damping concepts calculated the modal damping for the first thirty modes. The system damping results were obtained using various damping materials, Youngs moduli, and an assumed damping material loss factor of 1.0. The modal dampen was calculated as the ratio of the strain energy in the damping elements (SED) divided by the total strain energy (TSE) in the structure times the assumed material loss factor. The damping goal was set at 0.04 loss factor. The final designs developed had an average modal damping value which exceeded 0.1. This paper details the damping concepts evaluated, the thought process which led from one design to the next, the analysis used to evaluate the damping concepts, and the results of the trade study.

Constrained layer damping system for box beams

This paper discusses the results of a project aimed at developing an effective constrained layer damping system for a large steel box beam. The primary box beam evaluated was a 4.0-inch by 8.0-inch by 0.375-inch section box which was 96.0 inches long. The goal of the project was to obtain the most damping possible in the bending, twisting, and axial modes while meeting cost, weight, and installation requirements. The project started with the evaluation of the box beam as an appropriate solid beam with a continuous constrained layer damping system applied using a 6th order theory analysis program. The next analysis step was to advance to finite elements. During the FEA, bending modes in both planes, twisting modes, and axial modes were examined. The design iterations considered damping on the 8.0-inch surfaces only, damping on all surfaces, the effects of a standoff, and multiple segmentation in the constraining layer. After the analysis had developed the best damping configuration which met all the nondamping requirements, the damping system was fabricated and installed on the box beam for testing. This paper presents the results of the project from concept development through the test results.

Jitter suppression experiment active damping system design considerations

The University of Dayton Research Institute (UDRI) is teamed with McDonnell Douglas Aerospace (MDA) to develop and fly a NASA IN- STEP experiment entitled Jitter Suppression Experiment (JSX). The JSX will demonstrate a combined active/passive vibration control system on an actual full-scale space structure. This paper presents various mechanical considerations in the design of the active control system. This includes evaluating different sensor and actuator types and evaluating applicable control theories and control implementations.