Active control of forced harmonic vibration in finite degree of freedom structures with negligible natural damping

Methods of synthesis for vibration controllers are presented for mechanical structures where the number of actuators equals the number of modes to be controlled and for structures where the number of modes exceeds the number of actuators. Provided an observer can be constructed complete isolation from the disturbance will be possible for the first case even when the dynamics of the structure are not well defined. In the second case complete isolation is not in general possible but a considerable reduction of strain energy can still be achieved. Possible practical limitations are discussed.