Actuator arrangement for active vibration isolation comprising an inertial reference mass

Actuator arrangement comprising an actuator (8), a reference mass (22), a first suspension (24) with at least a predetermined spring characteristic in at least one degree of freedom, and a first sensor (26;

• 42, 43;
• 32, 36), the actuator (8) being arranged to apply a force between a first object (2) and a second object (16;
• 54), the reference mass (22) being arranged to be supported by a third object (16;
• 56) by means of said first suspension (24), and said first sensor (26;
• 42, 43;
• 32, 36) being arranged to generate a first distance signal that depends on a first distance (z2;
• z5,z6;
• z3,z4) between said reference mass (22) and said first object (2) and to provide said first distance signal to a controller (6) to actuate said actuator (8).