Patent Publication Number: US-2006016940-A1

Title: Apparatus and method for directing an instrument

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates generally to directing instruments at targets and, more particularly, to directing instruments mounted on vehicles toward moving or stationary targets on the ground and in the air.  
      2. Description of the Related Art  
      A variety of instruments can be mounted to aircraft and other vehicles to send and/or receive signals or images. In the areas of reconnaissance, tracking and surveying, the instruments are typically mounted to aircraft. The instruments are generally directed toward the ground and are configured to receive electromagnetic radiation to produce images, still or moving, of the underlying terrain or of targets on the ground. In some applications, the instruments may be configured to send and/or receive alternative forms of energy or signals.  
      To permit the instrument to be directed relative to the vehicle, the instruments are typically movably mounted to the vehicle. The instrument may be directed at any target within its range of movement. Some applications can require that the instrument tracks a moving or stationary target on the ground or in the air. In other applications, the instrument may be required to continuously monitor a particular location as the vehicle on which the instrument is mounted moves over or by the location. Still other applications can require that the instrument is directed across a large cross section of terrain as the vehicle moves forward such as by sweeping side to side or in other broadening coverage patterns.  
      The mounting structures for many instruments commonly include gimbals and gimbal-like systems to permit the controlled movement of the instruments. These mounting structures are configured to secure the instrument and to direct an aperture/sensor/emitter of the mounted instrument. In many cases, instruments mounted to gimbals and gimbal-like systems attempt to substantially balance the mass of the instrument about each axis of rotation. This results in a significant portion of the instrument extending beyond the axis of rotation. Typically, such positioning of such instruments will swing the end of the instrument to be directed at a target in a wide arch outside the center of the gimbals axis of rotation. This arch creates the need for many prior instruments to extend outside of a vehicles body or fuselage so that the instrument can maintain a wide range of movement to track targets.  
      With some mounting systems, the base of instrument is hingedly attached to the vehicle to swing in an arch of between 0 and 90 degrees. This swinging permits the azimuth to be changed as a target is tracked. Such mounting systems also rotate up to 360 degrees in the horizontal plane. This combination of movements allows the directed end of instrument to move about at least a portion of a hemisphere and provides the instrument with a wide range of movement to direct the instrument at a target. However, these systems and other systems can present some problems in their application.  
      One problem is the result of the rotation of an instrument relative to the vehicle to which it is mounted. This rotation can twist and torque the cables that connect the instrument to other equipment on the vehicle. This twisting and torquing can increase fatigue and reduce the useful life of the cables. Accordingly, relatively complex rotatable interconnects are typically used to connect of the instrument to other systems in the vehicle. The rotatable interconnects typically increase costs and can create reliability and maintenance issues.  
      Another problem relates to the control of mounting systems. In certain positions, the control systems for some mounting systems can be subject to gimbal lock. This phenomenon may occur when the instrument is directed along the vertical axis or gimbal pole. With some control systems, this position can induce a singularity error in the control algorithm. In essence, the control system does not know whether to rotate the instrument or change the azimuth to continue directing the instrument. This can lock up the computer and freeze the instrument which prevents further movement of the instrument until the system is reset. Of course, it is not desirable to have an instrument freeze or lock up during an operation.  
      Further, a semi-circular window or an external turret is necessary to protect the instrument as the aperture swings about its arch of rotation. These structures can be necessary to permit the movement of the aperture of the instrument through its desired range of movement while protecting the instruments from the damaging forces of wind and debris. The windows and turrets commonly extend from the structure of an aircraft or other vehicle. The turrets typically move in conjunction with aspects of the instrument relative to the aircraft. The aperture of the instrument typically has a constant position relative to at least a portion of the turret. The semi-circular windows typically remain stationary relative to the aircraft as the instrument moves relative to the aircraft. The semi-circular windows are substantially transparent to the signal or image which is to be sent or received through them by the instrument. The instrument typically is directed such that its directed end moves about the concave inner surface of the window to track a target through the window. The distance from the interior surface of the window typically remains substantially constant. The constant distance maintains a relatively constant curvature through which the instrument may transmit or receive signals. The relatively constant distance and curvature present a relatively constant level of distortion which can be compensated for by the instrument or by manipulation of the instrument&#39;s output data.  
      The windows and turrets are frequently referred to as “warts” or “blisters” due to the structural anomaly that they present on the fuselage of the aircraft or other vehicles. These structures can produce anomalies in the fluid flow about the vehicle and reflect radar which increases the visibility of the vehicle to enemy radar. On aircraft, these anomalies in fluid flow can substantially increase the aerodynamic drag on the aircraft. This increased drag reduces an aircrafts top speed, increases fuel consumption, creates noise, and alters the aircrafts performance and flight characteristics. In some cases, the anomalies can result in damaging vibration which increases fatigue and maintenance on the aircraft. Accordingly, some aircraft are fitted with fairings around the external housings to smooth airflow. However, these fairings are large and expensive and can limit the range of positions at which the instrument may effectively transmit or receive a signal.  
      Other instrument systems use a mirror or plurality of mirrors to direct the image or signal to or from the instrument mounted in the vehicle. However, these systems tend to introduce distortions, especially at low angles, into the resulting image unless manufactured to extremely precise tolerances. These systems&#39; complexity introduces a number of variables which complicate manufacture and may limit the accuracy of the instrument.  
     SUMMARY OF THE INVENTION  
      The present invention addresses the above mentioned problems in the prior art and provides additional improvements and advantages that will be recognized by those skilled in the art upon review of the following Figures and description.  
      An object of the present invention is to provide an apparatus and method for directing an instrument at a target from a vehicle. Another object of the present invention is to provide an apparatus and method for directing an instrument mounted to a vehicle that is mounted substantially internal within the vehicle. Yet another object of the present invention is to reduce the size or eliminate the need for the external window or external turret used to protect the instrument on some vehicles. Still another object of the present invention is provide an apparatus which with control systems which is not prone to gimbal lock.  
      In one aspect, the present invention provides an apparatus for mounting an instrument. The mounting apparatus includes a first support having a first arched surface. The first arched surface can define a first arch having a constant radius of curvature or a variable radius of curvature. Accordingly, the first arch may be in the shape of a semicircle. The first support is hingedly secured to a mount to rotate about a first axis. The mount may be integral with a surface of a vehicle or may be a separate component which could be attached to a vehicle. An instrument mount is secured to the first arched surface to be movable between a plurality of points along the first arched surface. The instrument mount is generally configured to direct an instrument toward a center of the first arch. The instrument mount may include a friction reducing element to reduce friction as the instrument mount is moved along the first arched surface. The friction reducing surface may be a roller, a low friction material, or other friction reducing surface that will be recognized by those skilled in the art. The mounting apparatus can further include a first actuator connected to the first support to position the first support about the first axis. The mounting apparatus may also include a first linear actuator secured to the instrument mount to position the instrument mount along the first arched surface.  
      In another aspect, the present invention provides an apparatus for mounting an instrument having a first support and a second support. The first support again having a first arched surface. The first arched surface can define a first arch having a constant radius of curvature or a variable radius of curvature. Accordingly, the first arch may be in the shape of a semicircle. The first support is hingedly secured to a mount to rotate about a first axis. The second support having a second arched surface. The second arched surface can define a second arch having a constant radius of curvature or a variable radius of curvature. Accordingly, the second arch may be in the shape of a semicircle. The second support is hingedly secured to a mount to rotate about a second axis. The mount may be integral with a surface of a vehicle or may be a separate component which could be attached to a vehicle. An instrument mount is secured to the first arched surface and the second arched surface to be movable between a plurality of points along both of the first arched surface and the second arched surface. The instrument mount is generally configured to direct an instrument toward a center of the first arch and the second arch. The instrument mount may include a friction reducing element to reduce friction as the instrument mount is moved along the first arched surface and the second arched surface. The friction reducing surface may be a roller, a low friction material, or other friction reducing surface that will be recognized by those skilled in the art. The mounting apparatus can further include a first actuator connected to the first support to position the first support about the first axis. Similarly, the mounting apparatus can include a second actuator connected to the second support to position the second support about the second axis. Alternatively, the mounting apparatus may include a first linear actuator secured to the instrument mount to position the instrument mount about the second axis and may include a second linear actuator secured to the instrument mount to position the instrument mount about the first axis.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  illustrates a side view of a vehicle in partial cross-section including an apparatus for directing an instrument in accordance with the present invention;  
       FIG. 2  illustrates a perspective view of an embodiment of an apparatus for directing an instrument in accordance with the present invention;  
       FIG. 3  illustrates a side view of an embodiment of an apparatus for directing an instrument in accordance with the present invention;  
       FIG. 4  illustrates a top view of an embodiment of an apparatus for directing an instrument in accordance with the present invention;  
       FIG. 5  illustrates a perspective view of another embodiment of an apparatus for directing an instrument in accordance with the present invention;  
       FIG. 6  illustrates a perspective view of yet another embodiment of an apparatus for directing an instrument in accordance with the present invention; and  
       FIG. 7  illustrates a block diagram of an embodiment of a control system for an apparatus in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      The present invention provides an apparatus for mounting an instrument in a vehicle. The apparatus of the present invention could be used to mount an instrument in a wide variety of vehicles, including aircraft, spacecraft, ground vehicles, ships, and submarines. Furthermore, an apparatus in accordance with the present invention could be secured in an external pod or other modular elements that may be attached to the exterior of any one of the listed vehicles. For exemplary purposes and ease of description, the following description is generally directed to an apparatus and method for mounting an imaging instrument on an aircraft for ground surveillance.  
      Generally, an apparatus  10  in accordance with the present invention includes an instrument  12 , an instrument mount  14 , and at least a first support  16 . Apparatus  10  typically mounts internally within a vehicle  100  and directs instrument  12  through a portal  102  in vehicle  100  toward a target or desired location. One or more supports may be hingedly secured to the vehicle  100 . Instrument mount  14  is slidably attached to an arched portion of the one or more supports. Instrument  12  is secured to instrument mount  14 . Instrument mount  14  is guided by at least a first support  16  through a range of motion which typically approximates a hemisphere (or other dome like shape) or portion thereof to direct instrument  12  toward a target.  
      Instrument  12  is typically configured to send or receive signals or to receive images. Instrument  12  includes a body defining a mounted portion  30  to instrument mount the instrument and a directed end  32 . Directed end  32  of instrument  12  is the portion of the instrument which is directed toward the target location to send or receive signals or to receive images. Mounted portion  30  of instrument  12  is secured to instrument mount  14 . Instrument  12  is typically secured to instrument mount  14  to maintain a constant position relative to instrument mount  14 . Further, instrument  12  is secured to instrument mount  14  such that directed end  32  of instrument  12  is positioned inward toward the center of the hemisphere relative to mounted end  30 . The movement of instrument mount  14  positions the mounted portion  30  of instrument  12  to align the directed end  32  of instrument  12  with a target. Thus, apparatus  10  can direct the directed end  32  of instrument  12  toward a target by moving the mounted end  30  to a particular set of coordinates on the hemisphere (or other shape) defined by the movement of instrument mount  14 .  
      First support  16  functions to position instrument mount  14  within vehicle  100 . Accordingly, first support  16  is configured to support the weight of at least instrument mount  14  and instrument  12  as the weight of instrument mount  14  and instrument  12  is shifted to various locations on first support  16 . In some configurations having multiple supports, first support  16  may only need to be configured to support a portion of the weight of instrument mount  14  and instrument  12 . First support  16  is movably secured to a vehicle to swing around a first axis  42 . The swinging of first support  16  functions to position instrument mount  14  at various locations about first axis  42 . As illustrated for exemplary purposes, first support  16  may be hinged to a base plate  90  which is secured to a vehicle  100  or may be hinged directly to vehicle  100 .  
      First support  16  includes a first arched surface  40 . First arched surface  40  is generally configured to receive instrument mount  14  and to facilitate the movement of instrument mount  14  along an arch defined by first arched surface  40 . First arched surface  40  is typically in the shape of a semicircle but may include other fractional portions of a circle. Alternatively, first arch  42  may assume forms of other than circular origin such as a portion of a hyperbolic arch or other forms for orienting instrument mount  14 . The combination of instrument mount  14  being movably secured to first arched surface  40  and the swinging rotation of the first arched surface  40  about the first axis  42  permits the positioning of instrument mount  14  at any coordinate on the surface defined by the rotation of first arched surface  40  about first axis  42 .  
      In one aspect, the movement of first arched surface  40  may be controlled by a first actuator  60  which can controllably position first arched surface  40  at various positions along it range of motion about first axis  42 . First actuator  60  may drive second support  18  in a variety of manners such as, for example, using gear, a worm drive, belt drive, chain drive, directly, a combination drive, or by other apparatus or systems that will be recognized by those skilled in the art upon review of the present disclosure. First actuator  60  is typically controlled by a controller  100 , shown in  FIG. 7 , to position instrument mount  14  about first axis  42 . The computer may communicate with the instrument  12  and motors through a set of cables  80  which connect the instrument to systems within vehicle  100 .  
      A second support  18  may also be provided. Depending on the particular configuration, second support  18  may function to further support and position instrument mount  14  within vehicle  100 . Accordingly, second support  18  is configured to support at least a portion of the weight of at least instrument mount  14  and instrument  12  as the weight of instrument mount  14  and instrument  12  is shifted to various locations on first support  16 . Second support  18  is movably secured to a vehicle to swing around a second axis  46 . First axis  42  and second axis  46  may be coplanar and may be perpendicular to one another. The swinging second support  18  functions to position instrument mount  14  at various locations about second axis  46 . As illustrated for exemplary purposes, second support  18  may be hinged to a base plate  90  which is secured to a vehicle  100  or may be hinged directly to vehicle  100 .  
      Second support  18  includes a second arched surface  44 . Second arched surface  44  may also be generally configured to receive instrument mount  14  and to facilitate the movement of instrument mount  14  along an arch defined by second arched surface  44 . Second arched surface  44  is typically in the shape of a semicircle but may include other fractional portions of a circle. Alternatively, second arch  44  may assume forms of other than circular origin such as a portion of a hyperbolic arch or other forms for orienting instrument mount  14 . The combination of instrument mount  14  being movably secured to second arched surface  44  and the swinging rotation of the first arched surface  44  about the second axis  46  permits the positioning of instrument mount  14  at any coordinate on the surface defined by the rotation of second arched surface  44  about second axis  46 .  
      In one aspect, the movement of second arched surface  44  may be controlled by a second actuator  64  which can controllably position second arched surface  44  at various positions along it range of motion about second axis  46 . Second actuator  64  may drive second support  18  in a variety of manners such as, for example, using gear, a worm drive, belt drive, chain drive, directly, a combination drive, or by other apparatus or systems that will be recognized by those skilled in the art upon review of the present disclosure. Second actuator  64  is typically controlled by a controller  100 , shown in  FIG. 7 , to position instrument mount  14  along second arched surface  44  as set forth in the examples below. The computer may communicate with the instrument  12  and motors through a set of cables  80  which connect the instrument to systems within vehicle  100 .  
      Instrument mount  14  is movably secured to at least one arched surface. The attachment of instrument mount  14  to the at least one arched surface is of sufficient strength to support the weight of both instrument mount  14  and instrument  12  at the various locations at which instrument mount  14  may be positioned about arched surface  40 . Instrument mount  14  is generally configured to secure and direct instrument  12  as instrument mount  14  is positioned at various coordinates on the hemisphere, portion of a hemisphere, or other shape defined by the mount&#39;s range of movement. Accordingly, instrument mount  14  is generally configured to stably support and position the mass of instrument  12 . Instrument mount  14  is secured to first arched surface  40  such that instrument mount  14  may be positioned at a plurality of points along the arch defined by first arched surface  40 . Instrument mount  14  may include one or more friction reducing elements  72  such as, for example, rollers, ball bearings, low friction surfaces or other structures to reduce the frictional forces as instrument mount  14  is positioned at various coordinates. In one aspect, instrument mount  14  may be positioned along the first arched surface  40  by the mount&#39;s connection to a second support  18  having a second arched surface  44  to which instrument mount  14  is also movably secured as generally illustrated in the embodiments of FIGS.  2  to  4 . In another aspect, instrument mount  14  may include a first linear actuator  82  to position instrument mount  14  along the first arched surface  40 . In yet another aspect, instrument mount  14  may include a second linear actuator  82  to position instrument mount  14  along the second arched surface  44 .  
      The mounted end  30  of instrument  12  is secured to instrument mount  14  to position the directed end  32  of instrument  12 . Instrument  12  is secured to instrument mount  14  such that at least the directed end  32  of instrument  12  extends inward toward the center of first arched surface  40 , generally toward the foci of the first arched surface  40 , or otherwise generally into the first arched surface  40 . As instrument mount  14  is moved through its range of motion, the longitudinal axis of instrument  12  can maintain a constant angle to a plane tangent to the shape defined by the movement of arched surface or arched surfaces which guide instrument mount  14 . This constant angle is typically normal to the tangent plane. Essentially, instrument  12  can be supported by instrument mount  14  to form a cantilever along its longitudinal axis of instrument  12  to generally position the instrument&#39;s directed end  32  adjacent to portal  102  in a vehicle  100 . In certain configurations, the position of directed end  32  remains substantially adjacent to the portal  102  the mounted end  30  is positioned by instrument mount  14  to direct the instrument.  
      When the instrument mount&#39;s range of movement defines in at least a portion of a hemisphere, instrument mount  14  will move at a fixed distance about a single point of rotation which will coincide with the center of the hemisphere. When the range of movement of instrument mount  14  is not hemispherical, the point of rotation may vary to some degree as instrument mount  14  is positioned at various locations in its range of movement. At any given location that instrument mount  14  may be positioned, the position of directed end  32  of instrument  12  relative to the point of rotation will depend on the length of the instrument relative to the radius of the hemisphere defined by the movement of instrument mount  14 . In one aspect, directed end  32  of mounted instrument  12  will be remain inside the point of rotation as instrument mount  14  is positioned at various coordinates in its range of movement. In other aspects, directed end  32  of a mounted instrument  12  may extend to this point of rotation. In still other aspects, the directed end  32  of a mounted instrument  12  may extend beyond this point of rotation as instrument mount  14  is positioned at various coordinates in its range of movement.  
      Similar embodiments of an apparatus  10  in accordance with the present invention are shown in FIGS.  1  to  4 . As illustrated, apparatus  10  includes instrument  12  secured to an instrument mount  14 , a first support  16 , and a second support  18 . The embodiment of  FIG. 1  is operatively mounted for ground surveillance to a vehicle  100  which is illustrated for exemplary purposes as an unmanned aerial vehicle (UAV). Apparatus  10  is positioned in vehicle  100  to direct an instrument  12  generally downward through a portal  102  toward a target or location. A window  104  is provided over portal  102  on the underside of vehicle  100  to protect instrument  12  and to smooth airflow over the surface of vehicle  100 . Window  104  is illustrated for exemplary purposes with some curvature to minimize variations in the distortion of an image received by instrument  12 .  
      As illustrated in  FIG. 1 , first support  16  and second support  18  are secured by mounts  50  which are integral or otherwise attached to the fuselage of vehicle  100 . Alternatively, mounts  50  may be integral with or attached to a base  90 , as shown in FIGS.  2  to  4 , which is secured to vehicle  100 . Further, mounts  50  may be particularly described herein as first mount  50  and second mount  50  relative to being secured to first support  16  and second support  18 , respectively. When mounted in a base  90 , the directed end  32  of instrument  12  is typically positioned such that a sensing structure or emitting structure at the directed end is directed through an orifice  92  in the base  90 . First support  16  and second support  18  are illustrated as having a similar semicircular configuration for exemplary purposes substantially differing only in their radii for exemplary purposes. Further, first support  16  and second support  18  are illustrated as having a triangular cross section for exemplary purposes. As illustrated, each of the three exterior surfaces of the triangular cross-section may be considered a first arched surface  40  and a second arched surface  44  for first support  16  and second support  18 , respectively. In essence, the embodiments illustrated in FIGS.  1  to  4  present a first support  16  and a second support  18  in which the first arched surface  40  and the second arched surface  44  are substantially coextensive with the entire exterior surface of the respective first support  16  and second support  18 . In other embodiments, the first arched surface  40  and the second arched surface  44  may be limited to distinct regions or portions of first support  16  and a second support  18 , respectively.  
      First support  16  rotates about a first axis  42  to position instrument mount  14  along second arched surface  44 . A first actuator  60  controlled by a controller  100 , shown in  FIG. 7 , positions first support  16  about first axis  42 . For exemplary purposes, actuator  60  is illustrated as positioning first support  16  around first axis  42  with a belt  62 .  
      Second support  18  rotates about a second axis  46  to position instrument mount  14  along first arched surface  40 . A second actuator  64  controlled by a controller  100 , shown in  FIG. 7 , positions first support  16  about first axis  42 . For exemplary purposes, second actuator  64  is illustrated as positioning second support  18  around second axis  46  with a belt  66 .  
      Instrument mount  14  is illustrated in FIGS.  2  to  4  with a composite structure for exemplary purposes. As illustrated, instrument mount  14  includes a first member  70  slidably secured to first arched surface  40  and a second member  74  slidably secured to second arched surface  44 . First member  70  includes a first friction reducing element  72  illustrated as a plurality of rollers to minimize the frictional forces resulting from the first element&#39;s contact with the first arched surface  40  for exemplary purposes. Second member  74  includes a second friction reducing element  76  illustrated as a plurality of rollers to minimize the frictional forces resulting from the second element&#39;s contact with the second arched surface  44  for exemplary purposes. First member  70  and second member  74  are securedly attached to one another to form instrument mount  14 . First member  70  and second member  74  may be secured to one another in a manner to permit the rotation of first member  70  and second member  74  relative to one another. In other embodiments, instrument mount  14  may be formed from a single piece of material or may be formed from more than two components.  
      Instrument  12  includes a mounted end  30  and a directed end  32 . Mounted end  30  is secured proximate to instrument mount  14 . As illustrated in FIGS.  2  to  4 , instrument  12  is secured to instrument mount  14  by a bracket  34  for exemplary purposes. In other embodiments, the instrument  34  may be directly secured to instrument mount  14 . Directed end  32  extends away from instrument mount  14  toward the center of the portion of the hemisphere defined by the movement of instrument mount  14  along first arched surface  40  and seconded arched surface  44 . Furthermore, the directed end  32  of instrument  12  is typically configured such that a sensing structure or emitting structure at the directed end is generally directed toward the center of the rotation of instrument mount  12  about first axis  42  and second axis  46  regardless of the position of the mount. In some embodiments, directed end  32  of instrument  12  may extend beyond the center of the rotation of instrument mount  12  about first axis  42  and second axis  46 .  
      In operation, second actuator  64  positions second support about second axis  46 . This movement of second support  18  slidably positions instrument mount  14  on first arched surface  40 . First actuator  60  positions first support about first axis  42 . This movement of first support  16  slidably positions instrument mount  14  on second arched surface  44 . The combination of the mount&#39;s positioning about first arched surface  40  and second arched surface  44  permits instrument mount  14  to direct instrument  12  at a desired target.  
      Another embodiment of an apparatus  10  in accordance with the present invention is illustrated in  FIG. 5 . Apparatus  10  of  FIG. 5  generally includes a first support  16 , an instrument mount  14 , a mount drive unit  26 , and an instrument  12 . First support  16  is secured by mounts  50  to a base  90  or other mounts  50  which are otherwise secured to vehicle  100 . When mounted in a base  90 , the directed end  32  of instrument  12  is typically positioned such that a sensing structure or emitting structure at the directed end is directed through an orifice  92  in the base  90 . First arched surface  40  is illustrated as having a semicircular configuration for exemplary. Further, first support  16  is illustrated as having a rectangular cross section for exemplary purposes. As illustrated, each of the four exterior surfaces of the triangular cross-section may be considered a first arched surface  40  of first support  16 . In essence, the embodiment illustrated in  FIG. 5  presents a first support  16  in which the first arched surface  40  is substantially coextensive with the entire exterior surface of the first support  16 . In other embodiments, the first arched surface  40  may be limited to a distinct region or portion of first support  16 .  
      First support  16  rotates about a first axis  42  to position instrument mount  14  around first axis  42 . A first actuator  60  controlled by a controller  100 , shown in  FIG. 7 , positions first support  16  about first axis  42 . For exemplary purposes, actuator  60  is illustrated as positioning first support  16  around axis  42  with a belt  62  driven by motor  60 .  
      Instrument mount  14  is fixedly secured to the mounted end  30  of instrument  12 . Instrument mount  14  is also movably secured to first support  16  to permit positioning along the first arched surface  40 . As illustrated in  FIG. 5 , a first linear actuator  82  is secured to instrument mount  14 . First linear actuator  82  can include a motor or other actuator operatively connected to first support  16  to facilitate the movement or positioning of instrument mount  14  on first arched surface  40 . To drive instrument mount  14 , first linear actuator  82  may for example include a drive wheel communicating with the first arched surface  40 , or a cog or worm gear which receives a series of teeth on the first support  16 . First linear actuator  82  is typically controlled by a controller  100 , shown in  FIG. 7 , to position instrument mount  14  about first ached surface  40 .  
      In one aspect, instrument mount  14  may be positioned along the first arch by a linear motor. In this aspect, first linear actuator  82  may function as the rotor of linear motor while the first arched surface  40  operates as the stator of the linear motor. To function as linear motor, first linear actuator  82  may include a magnet and first arched surface  40  may include a plurality of wound electrical elements. The wound electrical elements may be embedded in the material of first arched surface  40 . The wound electrical elements are used to generate a magnetic field by passing an electric current through them. By controlling the magnetic field, instrument mount  14  may be precisely positioned along first arched surface  40 .  
      In operation, first linear actuator  82  positions instrument mount  14  on first arched surface  40 . First actuator  60  positions instrument mount  14  about axis  42  by positioning first arched surface  40  about first axis  42 . The combination of positioning instrument mount  14  on arched surface  40  and positioning instrument mount  14  about first axis  42  permits instrument mount  14  to direct instrument  12  at a desired target.  
      Yet another embodiment of an apparatus  10  in accordance with the present invention is shown in  FIG. 6 . As illustrated, apparatus  10  includes instrument  12  secured to an instrument mount  14 , a first support  16 , and a second support  18 . First support  16  and second support  18  are illustrated as hinged to mounts  50  which are integral with a base  90 , for exemplary purposes. Again, mounts  50  may be particularly described herein as first mount  50  and second mount  50  relative to being secured to first support  16  and second support  18 , respectively. First support  16  and second support  18  are illustrated as having a similar semicircular configuration for exemplary purposes substantially differing only in their radii for exemplary purposes. Further, first support  16  and second support  18  are illustrated as having a triangular cross section with the apexes of the triangles directed toward one another for exemplary purposes. As illustrated, each of the three exterior surfaces of the triangular cross-section may be considered a first arched surface  40  and a second arched surface  44  for first support  16  and second support  18 , respectively. Like another illustrated embodiment, the embodiment illustrated in  FIG. 6  includes a first support  16  and a second support  18  in which the first arched surface  40  and the second arched surface  44  are substantially coextensive with the entire exterior surface of the respective first support  16  and second support  18 . In other embodiments, the first arched surface  40  and the second arched surface  44  may be limited to distinct regions or portions of first support  16  and a second support  18 , respectively.  
      Instrument mount  14  is movably secured to first support  16  to permit positioning of instrument mount  14  along the first arched surface  40 . As illustrated in  FIG. 6 , a first linear actuator  82  and a second linear actuator  84  are secured to instrument mount  14 . First linear actuator  82  can include a motor or other actuator operatively connected to first support  16  to permit the movement or positioning of instrument mount  14  along first arched surface  40 . Second linear actuator  84  can include a motor or other actuator operatively connected to second support  18  to facilitate the movement or positioning of instrument mount  14  along second arched surface  44 . To drive instrument mount  14 , first linear actuator  82  and second linear actuator  84  may for example include a drive wheel communicating with the first arched surface  40 , or a cog or worm gear which receives a series of teeth on the first support  16 . First linear actuator  82  and second linear actuator  84  are typically controlled by a controller  100 , shown in  FIG. 7 , to position instrument mount  14  about first ached surface  40 .  
      In one aspect, instrument mount  14  may be positioned by linear motors. In this aspect, first linear actuator  82  and second linear actuator  84  may function as the rotors of linear motors while the first arched surface  40  and the second arched surface  44  operate as the stators of the linear motors. To function as linear motors, first linear actuator  82  and second linear actuator  84  may include a magnet and first arched surface  40  and the second arched surface  44  may include a plurality of wound electrical elements. The wound electrical element may be embedded in the material of first arched surface  40  and the second arched surface  44 . The wound electrical elements are used to generate a magnetic field by passing an electric current through them. By controlling the magnetic fields, instrument mount  14  may be precisely positioned along both of first arched surface  40  and second arched surface  44 .  
      Instrument  12  includes a mounted end  30  and a directed end  32 . Mounted end  30  is secured proximate to instrument mount  14 . As illustrated in  FIG. 6 , instrument  12  is secured to instrument mount  14  by a bracket  34  for exemplary purposes. In other embodiments, the instrument  34  may be directly secured to instrument mount  14 . Directed end  32  extends away from instrument mount  14  toward the center of the portion of the hemisphere defined by the movement of instrument mount  14  along first arched surface  40  and seconded arched surface  44 . Furthermore, the directed end  32  of instrument  12  is typically configured such that a sensing structure or emitting structure at the directed end is generally directed toward the center of the rotation of instrument mount  12  about first axis  42  and second axis  46  regardless of the position of the mount. In some embodiments, directed end  32  of instrument  12  may extend beyond the center of the rotation of instrument mount  12  about first axis  42  and second axis  46 .  
      In operation, first linear actuator  82  positions instrument mount  14  on first arched surface  40 . Second linear actuator  84  positions instrument mount  14  on second arched surface  44 . The combination of the mount&#39;s positioning about first arched surface  40  and second arched surface  44  permits instrument mount  14  to direct instrument  12  at a desired target.  
       FIG. 7  illustrates an exemplary embodiment of a controller  100  to position and control the movement of instrument mount  14 . As illustrated, controller  100  includes a power supply  102 , a processor  104  and one or more sensors  106 . Power supply may provide power to processor  104  and sensor  106  as well as other components of the mounting apparatus  10 . Processor  104  is typically a microprocessor. In one aspect, the microprocessor can control the position of instrument mount  14  to direct instrument  12  at a target using an algorithm based on two pi steradian movement. Processor  104  controls the actuators to position instrument mount  14 . Sensors  106  can determine the position of instrument mount  14 , the position of first arched surface  40 , the position of seconded arched surface  44 , and/or the position of the actuators and provide a signal to the microprocessor indicative of these one or more positions. Processor  104  may use these signals to adjust the position of instrument mount  14 .  
      The present invention is not intended to be limited to the particular embodiments disclosed in this description. Upon review of the description and figures, it will be apparent to those skilled in the art that various modifications and variations can be made to the structure and method of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the invention cover modifications and variations to the described embodiments that come within the scope of the claims and their equivalents.