Adaptively tuned vibration absorber

Abstract

An apparatus for absorbing vibrations in a structural member, such as in an aircraft fuselage, has first and second plates for attaching to the structural member. A mass, which is suspended between the plates, includes a first block connected to the first plate by a first spring and a second block connected to the second plate by a second spring. The springs may be formed by metal straps which allow the mass to move along one axis or by rods which allow two axis movement of the mass. One sensor produces a signal indicating vibration of the structural member and another sensor produces a signal indicating vibration of the mass. A mechanism connected to the first and second block responds to a control signal by varying a distance between the first and second block to alter stiffness of the first and second springs. A control circuit receives the signals from the sensors and produces the control signal which causes the mechanism to alter the spring stiffness so that the spring and the mass resonate to absorb vibration of the structural member.