Tension Element Vibration Damping

The Rotational Tension Element Damper (RTED) uses a controlled tension line, backed by hydraulics, to damp large displacements in large structures. NASA built RTED prototypes that have been successfully tested on a 170-foot long wind turbine blade in test beds at the University of Maine. In this case, the RTED device damps the vibration of the large, tall turbine blades relative to a stationary anchor structure on the ground using a line and spring coupled to both the blade and the anchor, and controlled by a spool fitted with a one-way clutch. When force is applied, from heavy wind for example, the resulting movement of the tall structure triggers the necessary tension and compression cycles in the system to engage the rotating damper. The reaction force interferes with the rotation speed of the spool and disrupts and damps the vibration in the tall structure. The figure below shows test data for the RTED used on the wind turbine.

NASA MSFC&#8217s Fluid-Filled Frequency-Tunable Mass Damper (FTMD) technology implements a fluid-based mitigation system where the working mass is all or a portion of the fluid mass that is contained within the geometric configuration of either a channel, pipe, tube, duct and/or similar type structure. A compressible mechanism attached at one end of the geometric configuration structure enables minor adjustments that can produce large effects on the frequency and/or response attributes of the mitigation system. Existing fluid-based technologies like Tuned Liquid Dampers (TLD) and Tuned Liquid Column Dampers (TLCD) rely upon the geometry of a container to establish mitigation frequency and internal fluid loss mechanisms to set the fundamental mitigation attributes. The FTMD offers an innovative replacement since the frequency of mitigation and mitigation attributes are established by the compressible mechanism at the end of the container. This allows for simple alterations of the compressible mechanism to make frequency adjustments with relative ease and quickness. FTMDs were recently successfully installed on a building in Brooklyn, NYC as a replacement for a metallic TMD, and on a semi-submersible marine-based wind turbine in Maine. The FTMD technology is available for non-exclusive licensing and partially-exclusive licensing (outside of building construction over 300 feet).

Structural vibrations frequently need to be damped to prevent damage to a structure. To accomplish this, a standard linear damper or elastomeric-suspended masses are used. The problem associated with a linear damper is the space required for its construction. For example, if the damper's piston is capable of three inches of movement in either direction, the connecting shaft and cylinder each need to be six inches long. Assuming infinitesimally thin walls, connections, and piston head, the linear damper is at least 12 inches long to achieve +/-3 inches of movement. Typical components require 18+ inches of linear space. Further, tuning this type of damper typically involves fluid changes, which can be tedious and messy. Masses suspended by elastomeric connections enable even less range of motion than linear dampers. The NASA invention is for a compact and easily tunable structural vibration damper. The damper includes a rigid base with a slider mass for linear movement. Springs coupled to the mass compress in response to the linear movement along either of two opposing directions. A rack-and-pinion gear coupled to the mass converts the linear movement to a corresponding rotational movement. A rotary damper coupled to the converter damps the rotational movement. To achieve +/- 3 inches of movement, this design requires slightly more than six inches of space.

Structural vibrations frequently need to be damped to prevent damage to a structure or payload. To accomplish this, a standard linear damper or elastomeric-suspended masses are used. The problem associated with a linear damper is the space required for its construction. For example, if the damper's piston is capable of three inches of movement in either direction, the connecting shaft and cylinder each need to be six inches long. Assuming infinitesimally thin walls, connections, and piston head, the linear damper is at least 12 inches long to achieve +/3 inches of movement. Typical components require 18+ inches of linear space. Further, tuning this type of damper typically involves fluid changes, which can be tedious and messy. Masses suspended by elastomeric connections enable even less range of motion than linear dampers. The NASA invention is a compact and self-tunable structural vibration damper. The damper includes a rigid base with a slider mass for linear movement. Springs coupled to the mass compress in response to the linear movement along either of two opposing directions. A rack-and-pinion gear coupled to the mass converts the linear movement to a corresponding rotational movement. A rotary damper coupled to the converter damps the rotational movement. To achieve +/- 3 inches of movement, this design requires slightly more than six inches of space.

The NASA innovation leverages existing ballast fluid of a maritime structure to proactively mitigate undesirable resonant response characteristics of the platform or vessel. Essentially, this innovation couples water ballast as a functional working mass to the dynamic motion of a floating structure in order to provide passive motion management of the primary structure. The system can be implemented pre-design or post manufacture. The systems are simple and are easily manufactured, transported, and implemented onto a primary structure. The NASA technology has been designed (patents applied for) for a range of platform designs and can be further customized depending on the final application requirements. Prototypes have been built and tested in a wind-wave tank test bed at the University of Maine.