NASA engineers developed a new approach to mitigating unwanted structural vibrations that cause maintenance issues and compromise the performance and safety of large, tall structures. The Rotational Tension Element Damper (RTED) uses a controlled tension line, backed by hydraulics, to damp large displacements in large structures.
NASA’s method is fundamentally different from conventional passive and active vibration damping methods used today. The RTED uses disruptive modal coupling between two different structures, each with their own vibrational behavior, to provide vibration damping for one or both of the structures. This novel reactive vibration damping method uses feedback from the vibrational displacement itself, such as the tension and compression cycles from the movement of the vibrating structure (like a wind turbine or tower), to disrupt the vibration. Line tension is provided by either hydraulic, pneumatic, or magnetic means to suit the application and the size/displacement of the vibration. Compared to conventional spring dampers, TED devices are simple in design, lightweight, very effective, and have a smaller footprint.
NASA built RTED prototypes that were successfully tested on a 170-foot-long wind turbine blade in test beds. In this case, the RTED device damped 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.