Abstract:
A mass damper is provided for damping a mass. The mass damper includes a housing configured to couple to the mass and a plurality of electrostatically charged particles disposed within the housing, where the particles do not clump to one another or stick to the housing.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application is a divisional of Ser. No. 10/942,289 filed on Sep. 15, 2004. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention generally relates to vibration damping and isolation, and more particularly relates to an apparatus that uses charged particulates, without liquid media, to dampen vibration.  
       BACKGROUND OF THE INVENTION  
       [0003]     A precision pointing system carrying a sensor, such as a telescope as its payload, 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 damping the system may be needed.  
         [0004]     Typically, to minimize performance degradation caused by vibrations, a passive-mass damping and isolation system is used for damping the structure and isolating the payload carried by a precision isolation system. One type of passive mass damping and isolation system is a fluid damper. Fluid dampers operate by displacing a viscous fluid from one fluid reservoir to another fluid reservoir through a restrictive passage. Shearing of the viscous fluid as it flows through the restrictive passage provides a force that is proportional to velocity, i.e. a damping force.  
         [0005]     In these types of dampers, the viscous fluid is typically water, oil, or any one of numerous other fluid substances that are not in the gas, plasma, or solid phase. Although these fluids may be used in damping mechanisms that operate in environments where the range of temperature and pressure correspond to the fluid&#39;s liquid phase, they are inappropriate for environments outside this range. For instance, in the aerospace context where damping mechanisms may be exposed to temperatures that approach absolute zero, most of the fluids used in fluid dampers have low viscosity and/or may be a solid rather than a fluid.  
         [0006]     In other types of dampers, such as pneumatic fluid mass dampers, gases are used. Pneumatic fluid mass dampers operate by varying pressure, temperature, and gas viscosity. However, in extreme low temperatures, such as 0° Kelvin, gas-to-liquid phase changes may occur. Such changes are generally undesirable because when the gas changes into a liquid, the resulting volume of liquid and gas may not adequately absorb the system vibration and instead may begin to vibrate itself.  
         [0007]     One approach to addressing the above-mentioned drawbacks was developed by some of the inventors of the present invention. The prior approach, disclosed in U.S. patent application. Ser. No. 10/728,225 filed Dec. 3, 2003 entitled “Apparatus for Damping Vibration Using Macro Particulates,” and assigned to the assignee of the instant application, provides a mass damping system including a container within which a plurality of particulates is disposed. Although this prior approach addresses at least some of the above-noted drawbacks, it too presents certain drawbacks. In particular, although particulates may be insusceptible to phase change at extreme low temperatures, they may clump together into solids and vibrate with the mass instead of damping the mass.  
         [0008]     Accordingly, there is a need for an improved vibration damping system whose constituents do not clump and that can be used in most temperature ranges, particularly in extreme cryogenic temperature environments or extreme heat environments. 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  
       [0009]     A mass damper is provided for damping a mass. The mass damper includes an electrostatically charged housing configured to couple to the mass and a plurality of electrostatically charged particles disposed within the housing, each particle electrostatically charged with like polarity to that of the electrostatically charged housing.  
         [0010]     Another embodiment of the mass damper includes a housing, a plurality of particles, and a power source. The housing is configured to couple to the mass. The plurality of particles is disposed within the housing. The power source is coupled to the housing and configured to supply an electric potential thereto and electrostatically charge the housing, whereby when one of the particles of the plurality of particles contacts the housing, the particle is electrostatically charged.  
         [0011]     Yet another embodiment of the mass damper includes a housing, a plurality of particles, a conductive element and a power source. The housing is configured to couple to the mass. The plurality of particles is disposed within the housing. The conductive element is disposed within the plurality of particles. The power source is coupled to the housing and configured to supply an electric potential to the conductive element and electrostatically charge the conductive element, whereby the particle is electrostatically charged when one of the particles of the plurality of particles contacts the conductive element.  
         [0012]     Still yet another embodiment of the invention includes a housing, a plurality of particles, and a high-energy light source. The housing comprises negatively charged non-conductive material and is configured to couple to the mass. The plurality of particles is disposed within the housing. The high-energy light source is aimed at the plurality of particles and configured to direct high-energy photons toward at least one particle of the plurality of particles to thereby charge the particle. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and  
         [0014]      FIG. 1  is a schematic, cross sectional view of an exemplary mass damper;  
         [0015]      FIG. 2  is a schematic, cross sectional view of another exemplary mass damper;  
         [0016]      FIG. 3  is a schematic, cross sectional view of another exemplary mass damper;  
         [0017]      FIG. 4  is a schematic, cross sectional view of yet another exemplary mass damper; and 
     
    
     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 a mass damping system  100  according to an exemplary embodiment of the invention. The system  100  includes a housing  102 , a plurality of particles  104 , and an electrostatic charge supply  116 . The housing  102  has a cylindrical sidewall  106  and two end walls  108 ,  110  coupled to each of the ends of the cylindrical sidewall  106 . The walls  106 ,  108 ,  110  include an interior surface  114  that defines a chamber  112  within the housing  102 . Although the housing  102  is described herein as being cylindrical, it will be appreciated by those with skill that any one of a number of different shapes may be employed, such as for example, rectangular, prism-shaped, or square.  
         [0020]     The housing  102  may be constructed of any one of numerous types of materials that are either conductive or non-conductive (insulating). Conductive materials include, but are not limited to metallic materials, such as copper, aluminum, iron, and steel, or graphite, and insulating materials include but are not limited to glass, rubber, and ceramic. In either case, as will be discussed in more detail further below, an electrostatic charge is maintained on the housing  102 .  
         [0021]     The plurality of particles  104  are disposed within the housing chamber  112  and are used to absorb vibration from a vibrating mass. In an embodiment, the particles may be conductive material, or non-conductive material such as plastic. In another embodiment, the particles may be radioactive material. Preferably, the plurality of particles  104  has properties that allow it to simulate a homogenous fluid with inherent shear. Similar to the housing  102 , an electrostatic charge is also maintained on each of the plurality of particles  104 . The electrostatic charge on the particles  104  is of the same polarity as that on the housing  102 . The like electrostatic charge on the housing  102  and the particles  104  cause the housing  102  and particles  104  to repel one another, and the individual particles  104  to repel one another. As a result, particle clumping does not occur and the particles  104  simulate a fluid.  
         [0022]     The electrostatic charges on the housing  102  and the particles  104  may be induced in any one of numerous manners. For example, electricity may be introduced into the system  100  to cause the system components to have like electrostatic charges. In other examples, light or nuclear energy may be introduced into the system  100 . The method by which electrostatic charges are induced largely depends upon the materials from which the housing  102  and the plurality of particles comprise. Examples of various charging methods will now be described in detail below. It will be appreciated that system  100  components can have either a positive or negative charge, and although the components are described below and/or illustrated as having a positive charge, they may alternatively have a negative charge.  
         [0023]     Returning to  FIG. 1 , in the exemplary embodiment depicted therein both the housing  102  and plurality of particles  104  are made of conductive material, and the electrostatic charge supply  116  is an electric power supply. The power supply  116  is coupled to the housing  102  and is configured to create a deficiency of electrons in the housing  102  so that it becomes positively charged. Preferably, the power supply  116  is configured to carry the electrons away from the system  100 . Thus, when one of the particles  104  contacts the housing  102 , it too becomes positively charged, as it loses an electron to the positively-charged housing  102 . Once the particle  104  becomes positively charged, it repels the positively-charged housing  102 . Over time, more and more of the particles  104  contact the housing  102  and become positively charged, until substantially all of the particles  104  have like electrostatic charges. As a result, the particles  104  repel one another and the individual particles  104  do not clump. Additionally, the particles  104  do not adhere to the housing  102 .  
         [0024]     In another exemplary embodiment, such as depicted in  FIG. 2 , the housing cylindrical sidewall  106  is constructed of an insulating material, the end walls  108 ,  110  are made of a conducting material, and the power supply  116  is coupled to both end walls  108 ,  1   10 . Those with skill in the art will appreciate that alternatively separate power supplies may be coupled to each of the end walls  108 ,  1   10 . In one exemplary embodiment, the power supply  116  provides an electric potential across the end walls  108 ,  110  so that the electrons from one end wall  108  are pulled to the other end wall  110  to create an electron deficiency in one end wall  108  (positively-charged end wall  108 ) and an excess in the other end wall  110  (negatively-charged end wall).  
         [0025]     As the particles  104  contact the positively-charged end wall  108 , they lose an electron to become positively charged. Accordingly, the particles  104  repel the positively-charged end wall  108  and each other. At the other end of the housing  102 , as particles contact the negatively-charged end wall  110 , they gain an electron to become negatively charged. Thus, negatively-charged particles  104  repel the end wall  110  and one another. As the particles  104  are agitated and move toward the middle of the housing  102 , the positively-charged particles come into contact with the negatively-charged particles. When two of such types of particles  104  contact one another, the negatively-charged particle donates its excess electron to the positively-charged particle thereby neutralizing both particles. Consequently, both particles become like-charged and repel one another.  
         [0026]     Because numerous particles are included in the plurality of particles  104 , the particles behave like cold, dense plasma when interacting with one another. As the particles  104  repel each other and either end wall  108 ,  110 , kinematic motion of the particles  104  results. Thus, the particles  104  “self-mix” to further reduce clumping.  
         [0027]      FIG. 3  illustrates still yet another embodiment. In this exemplary embodiment, the housing  102  is constructed of a conductive material and the particles  104  are made of an insulating material, such as plastic. The power supply  116  is coupled to the housing  102  and configured to positively charge the housing walls  106 ,  108 ,  1   10 . An ultraviolet light source  120  is positioned proximate the housing  102  such as to direct UV photons on to the particles  104 . As the UV photons impinge upon the particles  104 , electrons are removed from the particles  104  and absorbed into the positively-charged housing  102 . Consequently, the plurality of particles  104  becomes positively charged and the particles  104  repel one another. Additionally, the particles  104  repel the positively-charged housing  102 .  
         [0028]     Another exemplary embodiment, depicted in  FIG. 4 , employs a high energy light source  121 , a housing  102  constructed of a negatively-charged insulating material, and particles  104  that are initially neutrally or positively charged. During operation, the high-energy light source  121  is aimed at the particles  104 . When the high-energy light impinges on one of the particles  104 , a proton leaves the particle  104  and is absorbed in the negatively-charged insulating material. As a result, the particle  104  becomes negatively charged. As the light hits more particles  104 , more of the particles  104  become negatively charged and, consequently, the like-charged particles  104  repel one another. Because the housing  102  is also like-charged, the particles  104  repel the housing  102  as well.  
         [0029]     Turning back to  FIG. 1 , a magnetic field may be applied to the charged components of the system  100  to enhance the damping features of the system  100 . In one exemplary embodiment, the system  100  includes a plurality of particles  104  comprising conductive material and a magnetic field coil  122 . The magnetic field coil  122  includes a wire  124 , power supply  126 , and a shaft  128 . The wire  124  is coupled to the power supply  126  and is coiled around the shaft  128 . As those with skill in the art may appreciate, the power supply  126  coupled to the wire  124  may or may not be the same as the power supply  116  coupled to the housing  102 . In either case, and as is generally known, when current from the power supply  126  flows through the wire  124 , a magnetic field is produced.  
         [0030]     When the system  100  vibrates, the application of the produced magnetic field to the system  100  causes the kinetic energy absorbed into the system  100  to dissipate as heat energy. This is due to the Lorentz effect, i.e. the combined effects of the applied magnetic field, the charged system  100 , the induced magnetic field on the charged system  100  and the rate of flow of the particles  104 . For example, the plurality of particles  104  in the system  100  may experience movement caused by mass vibration or the repulsion of the particles  104  from a like-charged particle or wall. The particles  104  may incidentally travel through the applied magnetic field, causing the particles  104  to produce an electrical current therein that creates an equal and opposite induced magnetic field relative to the applied magnetic field. However, because the particles  104  are made of conductive material, each may have an electrical resistance that prevents the electrical current from flowing freely through the particle  104 . This resistance causes the kinetic energy of the particles  104  to convert to and dissipate as heat energy. As a result, particle  104  movement is dampened.  
         [0031]     When the walls of the system  100  vibrate, the kinetic energy from the vibration is transferred to the plurality of particles  104  within the housing  102 . As previously mentioned, the absorbed kinetic energy may cause the particles  104  to travel through the applied magnetic field and to dissipate the kinetic energy into heat. Consequently, the system  100  is damped. Moreover, when the mass to be damped experiences vibration, the vibratory motion of the mass is transferred to the system  100  and then to the particles  104 .  
         [0032]     The plurality of particles  104  within the system  100  also may be mixed through the use of two magnetic fields. As illustrated in  FIG. 1 , a second magnetic coil  142  may be positioned proximate the first magnetic coil  122  to produce a second applied magnetic field. As known by those with skill in the art, if a moving charge is placed within an applied magnetic field, a force F will be exerted on the charge. When two applied magnetic fields occupy the same space, each applied magnetic field exerts a force upon the charge. The resulting force acting upon the charge is determined by calculating the sum of the two forces. Thus, based on this premise the movement of a charge (e.g., the force exerted on the charge) may be manipulated by varying the components of the two applied magnetic fields or varying the magnetic flux of a given area of either or both of the two applied magnetic fields. These may be achieved by varying the amount of current passing through the magnetic coils  122 ,  124 , or by any other known methods.  
         [0033]     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.