Abstract: A cross axis actuator (1.1) for reducing the transmission of vibration along elongate members (1.2) comprising a series of windings (1.5, 1.6, 1.7, 1.8, 1.9, 1.10) wound helically at 30.degree. pitch around the member (1.2) along part of its length in clockwise and anti-clockwise fashion and are anchored at two or more points (1.3, 1.4) to the member (1.2), the windings (1.5, 1.6, 1.7. 1.8, 1.9, 1.10) being able to be subjected to strain which causes deformation of the member (1.2) between attachment points (1.3, 1.4). The member (1.2) can be either a steel pipe or a rod. The windings (1.5, 1.6, 1.7, 1.8, 1.9, 1.10) can either be in the form of steel wires or be strips of material. The numbers of windings (1.5, 1.6, 1.7, 1.8, 1.9, 1.10) wound around the member (1.2) in a clockwise and anti-clockwise direction should be equal. Ideally, the windings (1.5, 1.6, 1.7, 1.8, 1.9, 1.10) are attached to the member (2) on a continuous basis except for the ends which are left free.

Abstract: A method of and system for active vibration control in an elongate member such as a pipe (2), wherein an actuator which comprises at least one constrictive element (3) capable of changing its length is attached between flanges (1) spaced along the member and is controlled to produce deformations of the member which inhibit the transmission of unwanted vibration from the member to one side of the attached actuator to the other side.

Abstract: A method of and a system for active vibration control of an extended mechanical structure having a point or region at which unwanted vibrations are to be reduced or suppressed, wherein a plurality of uni-axial inertial actuators (4, 5) are disposed to act on a rigid intermediate part such as a flange (1) attached to the point or region of the structure. The actuators may be controlled by an electronic controller (35, FIG. 3) to which are fed control signals from accelerometer sensors (27, 28) adjacent the flange (11).