Stiff actuator active vibration isolation system

An active vibration isolation system for isolating a payload from movement in first, second and third axes which are orthogonal to each other, said active vibration isolation system comprising:

• an intermediate mass;
• first, second and third stiff actuators having variable lengths respectively aligned with the first, second and third axes, each one of the first, second and third stiff actuators having a first end coupled to said intermediate mass and a second end coupled to a support susceptible to vibration;
• first, second and third sensors coupled to said intermediate mass and operable to sense movement along first, second and third directions, respectively, the first direction parallel with the first axis, the second direction parallel to the second axis, the third direction parallel to the third axis, said first, second and third sensors respectively generating first, second and third sensor signals;
• and
• circuitry coupled to said first, second and third sensors for generating a first control signal as a function of the first sensor signal, a second control signal as a function of the second sensor signal and a third control signal as a function of the third sensor signal, wherein the first, second and third control signals respectively govern operation of the first, second and third stiff actuators.

A method of actively isolating a payload from vibration, comprising the steps of:

• resting the payload on a passive isolator;
• coupling the passive isolator to a small mass which is at least one order of magnitude smaller than a predetermined range of payload masses;
• supporting the small mass from a base susceptible to vibration by at least one stiff actuator;
• sensing the movement of the small mass;
• generating a small mass sensor signal which is a function of the movement of the small mass;
• generating a control signal which is a function of the small mass sensor signal;
• applying the control signal to the stiff actuator;
• and
• responsive to said step of applying, varying a length of the stiff actuator, thereby reducing the vibration experienced by the payload.