Abstract:
A system is provided for damping and/or isolating vibration of a mass. The system comprises a housing, a shaft, a housing magnet, and a shaft magnet. The housing has an inner surface defining a passage. The shaft is disposed within said passage of said housing and configured to move axially therein. The shaft has an outer surface. The housing magnet is coupled to the housing inner surface. The shaft magnet is coupled to the shaft outer surface and is in alignment with the housing magnet and configured to repel the housing magnet.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention generally relates to reducing vibration experienced by a mass, and more particularly relates to a damping and/or isolation system for reducing low disturbance forces.  
       BACKGROUND OF THE INVENTION  
       [0002]     A precision pointing system carrying a sensor, such as a telescope, may be susceptible to disturbances that produce structural vibrations and, consequently, pointing errors. Such vibrations may be attributed to mechanical components or assemblies, such as reaction wheel assemblies, that are used as actuators in the precision pointing system. For the most part, because these systems tend not to have significant, inherent damping, these structural vibrations may degrade system performance and even cause structural fatigue over time. Therefore, an efficient means of providing vibration damping and/or isolation to the system may be needed.  
         [0003]     In some circumstances, a passive-mass damping system is used for damping the structure and isolating the payload carried by the precision pointing system. Passive-mass damping systems may have any one of numerous configurations. In one example, the system includes a container having a mass and a spring mounted therein. Fluid is also disposed within the container to provide damping by shearing the fluid. The mass includes a plurality of troughs formed around its outer periphery, and a ball is disposed within each of the troughs. The balls bear against the inner surface of the container to provide low friction oscillation of the mass in the container.  
         [0004]     In other circumstances, a rigid volume damper, such as an isolator, is used to minimize performance degradation caused by vibrations. Isolators may include a cylindrical container having a piston slidably mounted therein which divides the container into two sections. A fixed volume of fluid is typically disposed within the container so that when the piston moved through the container, the fluid passes from one section to the other. Balls are disposed between the piston and the inner surface of the container to minimize friction produced by the movement of the piston through the container.  
         [0005]     Although the above-described systems operate effectively in most applications, they may not be appropriate to implement in other applications. For example, in circumstances in which the system experiences a disturbance force in the range of micropounds, the systems may not provide appropriate damping. Specifically, in both of the above-mentioned systems, a friction force is generated when the balls bear against the -inner surface of the container, and if the disturbance force is less than the friction force the balls may not rotate and damping may not be provided.  
         [0006]     Accordingly, it is desirable to have a system that is operable to damp and/or isolate disturbance forces in the range of micropounds. In addition, it is desirable for the system to be relatively light weight. Moreover, it is desirable for the system to be inexpensive to manufacture. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.  
       BRIEF SUMMARY OF THE INVENTION  
       [0007]     A system is provided for damping and/or isolating vibration of a mass. The system comprises a housing, a shaft, a housing magnet, and a shaft magnet. The housing has an inner surface defining a passage. The shaft is disposed within said passage of said housing and configured to move axially therein. The shaft has an outer surface. The housing magnet is coupled to the housing inner surface. The shaft magnet is coupled to the shaft outer surface and is in alignment with the housing magnet and configured to repel the housing magnet.  
         [0008]     In another embodiment, and by way of example only, an isolator is provided for damping a mass. The isolator includes a housing, a shaft, a seal bellows, a spring, a flexure, a housing magnet, and a shaft magnet. The housing has an inner surface defining a passage. The shaft is disposed within the passage and configured to move axially therein. The shaft has an end and an outer surface. The seal bellows is disposed within the passage and coupled to the shaft end. The spring is disposed within the passage and has a first end and a second end, the first end coupled to the seal bellows and a second end. The flexure is coupled to the second end of the spring and configured to couple to the mass. The housing magnet is coupled to the housing inner surface. The shaft magnet is coupled to the shaft outer surface and is in alignment with the housing magnet and configured to repel the housing magnet.  
         [0009]     In still another embodiment, and by way of example only, a tuned mass damper is provided for damping a mass that includes a housing, a shaft, a spring, a housing magnet, and a shaft magnet. The housing has an inner surface defining a passage. The shaft is disposed within the passage and is configured to move axially therein. The shaft has an end and an outer surface. The spring is disposed within the passage and coupled to the shaft end. The housing magnet is coupled to the housing inner surface and the shaft magnet is coupled to the shaft outer surface. The shaft magnet is in alignment with the housing magnet and configured to repel the housing magnet. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and  
         [0011]      FIG. 1  is a schematic of an exemplary system having vibration isolation;  
         [0012]      FIG. 2  is a cross section of an exemplary isolator for use in the system depicted in  FIG. 1 ;  
         [0013]      FIG. 3  is a close up view of a portion of the exemplary isolator depicted in  FIG. 2 ;  
         [0014]      FIG. 4  is another cross section of the exemplary isolator of  FIG. 1  taken along line  3 - 3 ;  
         [0015]      FIG. 5  is a cross section of another exemplary embodiment of the exemplary isolator of  FIG. 1 ;  
         [0016]      FIG. 6  is a schematic of an exemplary system having vibration damping; and  
         [0017]      FIG. 7  is a cross section of an exemplary tuned mass damper for use in the system depicted in  FIG. 6 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]     The following detailed description of the invention is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description of the invention.  
         [0019]      FIG. 1  illustrates an exemplary system having vibration isolation capabilities. System  100  includes a base  102 , a payload  104 , and at least one isolator  106 . System  100  may be implemented in any one of numerous environments, such as in space, terrestrially, or under water. Base  102  is configured to provide a platform to which payload  104  and isolator  106  are coupled and may be any one of numerous application-appropriate devices. For example, in a space application, base  102  can be a satellite, an arm of a satellite, a space station, or any one of numerous other conventionally-used space apparatus. Payload  104  is a device that preferably needs vibration isolation to operate effectively and may be any one of numerous devices, such as, for example, a telescope or a camera. Isolator  106  dampens and isolates vibration that may be experienced by payload  104  and thus, is coupled between payload  104  and base  102 . Although  FIG. 1  depicts the use of a four isolators, it will be appreciated that fewer or more isolators may be implemented as well.  
         [0020]      FIG. 2  shows a cross section of an exemplary isolator  200 . Isolator  200  includes a housing  202  having an inner surface  204  that defines a passage  206 , and a shaft  208 , a seal bellows  210 , a damper spring  212 , a preload spring  214 , and compensator bellows  216 , each of which is disposed within passage  206 . Isolator  200  also includes a flexure  218  coupled to housing  202 .  
         [0021]     Housing  202  may be constructed from multiple pieces, such as shown in  FIG. 2 , or alternatively, formed from a single component. Additionally, housing  202  may have openings  219  formed on one or both ends that are configured to couple shaft  208  and other internal components of isolator  200  to base  102  or payload  104 .  
         [0022]     Turning now to  FIG. 3 , a close up view of a portion of isolator  200  is provided. As shown in  FIG. 3 , fluid  203  is disposed within housing  202  and moves through sections thereof. Shaft  208  is slidable within housing  202  and moves through passage  206  in an axial direction. Preferably, rotational motion of shaft  208  about a longitudinal axis  224  is not permitted. In this regard, a first end  226  of shaft  208  is fixedly attached to seal bellows  210 . In an alternative embodiment, a second end  228  of shaft  108  is fixedly attached to compensator bellows  216 . Gaps  220  are included between an outer surface  222  of shaft  208  and inner surface  204  of housing  202 . Gaps  220  prevent contact and reduce friction between shaft  208  and housing  202 .  
         [0023]     To ensure that gaps  220  are maintained and to further reduce friction between shaft  208  and housing  202 , repelling magnets  230   a ,  230   b ,  232   a , and  232   b  are included in isolator  200 . Magnets  230   a ,  230   b ,  232   a , and  232   b  may comprise any conventional, lightweight device used to generate magnetic fields, such as, for example, permanent magnets and electromagnets. Magnets  230   a  and  230   b  are coupled to inner surface  204  of housing  202  and may be coupled thereto in any one of a number of manners. For example, inner surface  204  of housing  202  may include grooves  234   a  and  234   b  within which magnets  230  may be disposed. Preferably, magnets  230  are spaced substantially equally apart from one another. Magnets  232   a  and  232   b  are coupled to outer surface  222  of shaft  208 , and similar to magnets  230   a  and  230   b , are coupled in any conventional manner. As shown in  FIG. 4 , magnets  232   a ,  232   b ,  232   c , and  232   d  may be disposed in grooves  236   a ,  236   b ,  236   c , and  236   d  that are formed in shaft  208 . Additionally, magnets  232   a ,  232   b ,  232   c  and  232   d  may also be spaced substantially equally apart from each other.  
         [0024]     As shown in  FIG. 3 , each of magnets  230   a  and  230   b  is preferably aligned with a corresponding magnet of magnets  232   a  and  232   b . Although four sets of magnets  230   a ,  230   b ,  232   a , and  232   b  are shown, more or fewer sets may be incorporated. Moreover, although magnets  230   a - 230   d  and  232   a - 232   d  are depicted in  FIG. 4  as each being a separate piece, they may have any other shape, such as ring-shaped, as shown in  FIG. 5 .  
         [0025]     Returning to  FIG. 2 , damper spring  212  and preload spring  214  are coupled to seal bellows  210  and compensator bellows  216 , respectively. Damper spring  212  and preload spring  214  each has a predetermined stiffness. In one exemplary embodiment, damper spring  212  and preload spring  214  are each removable from housing  102 , for example, via openings  219 . In such an embodiment, damper spring  212  and preload spring  214  may be replaced with springs having a stiffness that is different than the predetermined stiffness to thereby allow isolator  200  to be tunable.  
         [0026]     Flexure  218  is coupled to one end of housing  202  and to preload spring  214  via opening  219 . Flexure  218  is further configured to couple to base  102  or payload  104 , both shown in  FIG. 1 . Thus, when base  102  or payload  104  vibrates, the vibration is transferred through flexure  218  to preload spring  214 , and finally to shaft  208 . It will be appreciated that a second flexure  238  may be coupled to another end of housing  202  and may communicate with damper spring  212 .  
         [0027]      FIG. 6  illustrates another exemplary system  500  having vibration damping capabilities. System  500  includes a base  502 , a payload  504 , and at least one tuned mass damper  506 . System  500  may be implemented in any one of numerous environments, such as in space, terrestrially, or under water. Base  502  is configured to provide a platform to which the payload  504  is coupled and may be any one of numerous application-appropriate devices. For example, in a space application, base  502  can be a satellite, an arm of a satellite, a space station, or any one of numerous other conventionally-used space apparatus. Payload  504  is a device that preferably needs vibration damping to operate effectively and may be any one of numerous devices, such as, for example, a telescope or a camera. Tuned mass damper  506  dampens vibration that may be experienced by payload  504  and may be coupled thereto via various means such as bolts, epoxy, tape, etc.  
         [0028]      FIG. 7  shows a cross section of an exemplary tuned mass damper  506 . Tuned mass damper  506  includes a housing  602  having an inner surface  604  that defines a passage  606 , and a shaft  608 , a spring  610 , a fill cap  626 , and a cover  628 . Housing  602  defines a volume  636  therein and may be constructed from multiple pieces or alternatively, formed from a single component. Shaft  608  is slidable within housing  602  and moves through passage  606  in an axial direction. Preferably, rotational motion of shaft  608  about a longitudinal axis  634  is not permitted. In this regard, the shaft  608  is fixedly attached to spring  610 . A gap  612  is included between an outer surface  614  of shaft  608  and inner surface  604  of housing  602 . Gap  612  prevents contact and reduces friction between shaft  608  and housing  602 .  
         [0029]     To ensure that gap  612  is maintained and to further reduce friction between shaft  608  and housing  602 , repelling magnets  618   a ,  618   b ,  620   a , and  620   b  are included in tuned mass damper  506 , as shown in  FIG. 7 . Magnets  618   a ,  618   b ,  620   a , and  620   b  may comprise any conventional, lightweight device used to generate magnetic fields, such as, for example, permanent magnets and electromagnets. Magnets  618   a  and  618   b  are coupled to inner surface  604  of housing  602  and may be coupled thereto in any one of a number of manners. For example, inner surface  604  of housing  602  may include grooves  622   a  and  622   b  within which magnets  620   a  and  620   b  may be disposed. Preferably, magnets  620   a  and  620   b  are spaced substantially equally apart from one another. Magnets  618   a  and  618   b  are coupled to outer surface  614  of shaft  604 , and similar to magnets  620   a  and  620   b , are coupled in any conventional manner. Magnets  618   a  and  618   b  may be disposed in grooves  624   a  and  624   b  that are formed in shaft  604 . Additionally, magnets  618   a  and  618   b  may also be spaced substantially equally apart from each other.  
         [0030]     Each of magnets  620   a  and  620   b  is preferably aligned with a corresponding magnet of magnets  618   a  and  618   b . Although four sets of magnets  618   a ,  618   b ,  620   a , and  620   b  are shown, more or fewer sets may be incorporated. Moreover, although magnets  618   a ,  618   b ,  620   a , and  620   b  as each being a separate piece,  618   a ,  618   b ,  620   a , and  620   b  may have any other shape.  
         [0031]     Spring  610  is coupled between shaft  608  and fill cap  626 . Spring  610  has a predetermined stiffness and, in one exemplary embodiment is removable from housing  602 , for example, via fill cap  626 . In such an embodiment, spring  610  may be replaced with a spring having a stiffness that is different than the predetermined stiffness to thereby allow tuned mass damper  506  to be tunable. The mass of shaft  608  may be increased or decreases also allowing the tuned mass damper  506  to be tunable. In addition to being removable, fill cap  626  restrains shaft  608  from rotating about longitudinal axis  634  and, in this regard, is coupled to housing  602 .  
         [0032]     Cover  628  divides volume  636  into at least two sections  636   a  and  636   b . Cover  628  has an aperture  638  formed in its center that is provided to allow fluid to be passed between sections  636   a  and  636   b . Cover  628  has an outer peripheral surface that is coupled to housing  602  and is also coupled to bellows  630 . Bellows  630  is also coupled to a bellows cap  632 . When the temperature of the fluid inside housing  602  increases, fluid is passed through aperture  638  from section  636   a  into section  636   b  and bellows  630  is stretched. Consequently, the pressure in housing  602  remains relatively low when temperatures increase, and does not drop significantly when the temperatures decrease.  
         [0033]     There has now been provided a system that is operable to damp and/or isolate disturbance forces in the range of micropounds. In addition, the system is relatively light weight. Moreover, the system to inexpensive to manufacture.  
         [0034]     While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims and their legal equivalents.