Vibration isolation

Abstract

A support for machinery, and for isolating vibration from the machinery, comprises a plurality of mounts, each mount comprising an elastomeric block for completely supporting the static load of the machinery, and active isolation means comprising inertial shakers arranged to maintain essentially a zero stiffness of the mount to excited structural resonances over a desired frequency band above said mount resonant frequency, and to modify the transmission of out of balance forces to the hull. A control system coupled to the inertial shakers includes a means for applying damping force signals, such as to dampen structural resonances, to inhibit the onset of resonant vibration.

1 . A method for mounting machinery, and for isolating vibration therefrom, the method comprising:
 (a) supporting said machinery by means of a support that includes a plurality of resilient mounts, each mount comprising a passive resilient means for fully supporting the static load of the machinery, and active isolation means; and   (b) controlling said active isolation means of each said mount, the controlling comprising:
 (i) sensing motion of the support; 
 (ii) filtering, from the sensed motion, displacement arising from excited resonances, to determine the motion of the mount due to rigid body modes of motion; 
 (iii) calculating modal restoring forces; and 
 (iv) applying local demand forces to each said resilient mounts for compensating for rigid body modes of motion; 
   controlling said active isolation means being arranged such that:
 (i) below the mount resonant frequency a performance parameter of each mount is essentially that of the passive resilient means; and 
 (ii) above the mount resonant frequency and over a desired frequency band, essentially a zero stiffness of each mount is maintained to excited structural resonances. 
   
     
     
         2 . A method according to  claim 1 , wherein said active isolation means apply only alternating forces. 
     
     
         3 . A method according to  claim 1 , including controlling said active isolation means such as to dampen structural resonances, to inhibit the onset of resonant vibration. 
     
     
         4 .- 25 . (canceled) 
     
     
         26 . A machine readable medium comprising machine-executable instructions for performing a method for isolating vibration from machinery supported by a support that includes a plurality of resilient mounts, each mount comprising a passive resilient means for fully supporting the static load of the machinery, and active isolation means; the method comprising:
 controlling said active isolation means of each said mount, the controlling comprising:
 (i) sensing motion of the support; 
 (ii) filtering, from the sensed motion, displacement arising from excited resonances, to determine the motion of the mount due to rigid body modes of motion; 
 (iii) calculating modal restoring forces; and 
 (iv) applying local demand forces to each said resilient mounts for compensating for rigid body modes of motion; 
   the controlling said active isolation means being arranged such that:
 (i) below the mount resonant frequency a performance parameter of each mount is essentially that of the passive resilient means; and 
 (ii) above the mount resonant frequency and over a desired frequency band, essentially a zero stiffness of each mount is maintained to excited structural resonances. 
   
     
     
         27 . A machine readable medium according to  claim 26 , wherein the method performed by said machine executable instructions includes said active isolation means applying only alternating forces. 
     
     
         28 . A machine readable medium according to  claim 26 , wherein the method performed by said machine executable instructions includes controlling said active isolation means such as to dampen structural resonances, to inhibit the onset of resonant vibration. 
     
     
         29 . A method for mounting machinery, and for isolating vibration therefrom, the method comprising:
 (a) supporting said machinery by a support that includes a plurality of resilient mounts, each mount comprising a passive resilient support for fully supporting the static load of the machinery, and an active isolator; and   (b) controlling said active isolator of each said mount, the controlling comprising:
 (i) sensing motion of the support; 
 (ii) filtering, from the sensed motion, displacement arising from excited resonances, to determine the motion of the mount due to rigid body modes of motion; 
 (iii) calculating modal restoring forces; and 
 (iv) applying local demand forces to each said resilient mounts for compensating for rigid body modes of motion; 
   the controlling said active isolator of each said mount being arranged such that:
 (i) below the mount resonant frequency a performance parameter of each mount is essentially that of the passive resilient support; and 
 (ii) above the mount resonant frequency and over a desired frequency band, essentially a zero stiffness of each mount is maintained to excited structural resonances. 
   
     
     
         30 . A method according to  claim 29 , wherein said active isolators apply only alternating forces. 
     
     
         31 . A method according to  claim 29 , including controlling said active isolators such as to dampen structural resonances, to inhibit the onset of resonant vibration. 
     
     
         32 . A machine readable medium comprising machine-executable instructions for performing a method for isolating vibration from machinery supported by a support that includes a plurality of resilient mounts, each mount comprising a passive resilient support for fully supporting the static load of the machinery, and an active isolator means; the method comprising:
 controlling said active isolator of each said mount, the controlling comprising:
 (i) sensing motion of the support; 
 (ii) filtering, from the sensed motion, displacement arising from excited resonances, to determine the motion of the mount due to rigid body modes of motion; 
 (iii) calculating modal restoring forces; and 
 (iv) applying local demand forces to each said resilient mounts for compensating for rigid body modes of motion; 
   the controlling said active isolator being arranged such that:
 (i) below the mount resonant frequency a performance parameter of each mount is essentially that of the passive resilient support; and 
 (ii) above the mount resonant frequency and over a desired frequency band, essentially a zero stiffness of each mount is maintained to excited structural resonances. 
   
     
     
         33 . A machine readable medium according to  claim 32 , wherein the method performed by said machine executable instructions includes said active isolators applying only alternating forces. 
     
     
         34 . A machine readable medium according to  claim 32 , wherein the method performed by said machine executable instructions includes controlling said active isolators such as to dampen structural resonances, to inhibit the onset of resonant vibration.