Patent ID: 8915340

Claim:
Actuator arrangement comprising: an actuator; a reference mass; a first suspension with at least a predetermined spring characteristic in at least one degree of freedom; and a first sensor, the actuator being arranged to apply a controlled force between a first object and a second object so that a position of the first object relative to the reference mass is controlled, the reference mass being arranged to be supported by and isolated from a third object via said first suspension to provide independent (i) transmissibility and (ii) compliance within a frequency range of active vibration control of said actuator arrangement, and said first sensor being arranged (a) to generate a first distance signal that depends on a first distance (z 2 ; z 5 ,z 6 ; z 3 ,z 4 ) between said reference mass and said first object and (b) to provide said first distance signal to a controller, wherein responsive to said first distance signal, the controller actuates said actuator to provide active vibration isolation in which the first object follows the reference mass which comprises an independent reference mass, independent of the first object, and wherein said third object is supported by said second object by a second suspension, said actuator is supported by a fourth object, and the fourth object is supported by said second object by a third suspension, further wherein the third object and the fourth object are not directly connected to one another, and wherein any force generated by the actuator is not directly transferred to the second object but filtered, resulting in less displacement of the second object and thus less displacement of the reference mass than would occur without the third and fourth objects and corresponding second and third suspensions.