Abstract:
An active mirror guidance system for a vehicle is disclosed. The guidance system includes active mirrors to track a target. The mirrors are moved in response to disturbances detected by sensors or manually via remote control. The image provided from the mirrors is sent to a focus device for processing. A signature signal processing device and additional optics may also be used. A control system connects each of the components of the guidance system. The guidance system is also connected to the vehicle control equipment to steer the vehicle toward the target.

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Part of the work performed during development of this invention utilized U.S. Government funds. The U.S. Government has certain rights in this invention. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a guidance system. More specifically, the present invention relates to a guidance system using active mirrors to guide a vehicle. 
     2. Description of the Related Art 
     Conventional seekers employ a gimbal guidance system. Gimbal systems contain many moving parts, each of which is susceptible to failure. Due to their number of parts and complexity, gimbal systems also are weighty. Weight is typically a design constraint for airborne vehicles, which can be a difficulty for gimbal systems. Also, gimbal systems require numerous complex electrical interfaces for operation. What is needed is an improved guidance system that does not use gimbals. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an improved guidance system. 
     It is another object of the present invention to provide a guidance system that does not use gimbals. 
     It is another object of the present invention to provide a lightweight guidance system. 
     It is another object of the present invention to provide a reliable guidance system. 
     It is another object of the present invention to provide a vehicle employing an improved guidance system. 
     The present invention is a guidance system for a vehicle. The guidance system includes active mirrors to track a target. In a preferred embodiment, there are three mirrors. The mirrors are moved in response to disturbances detected by gyros, accelerometers, or manually via remote control. The image provided from the first and second mirrors is sent through a focus device to a third mirror. The image is then filtered and received by the image sensor for processing. A signature signal processing device and additional optics may also be used. A control system connects each of the components of the guidance system. The guidance system is also connected to the vehicle control equipment to steer the vehicle toward the target. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention is described with reference to the accompanying drawings, in which like reference characters reference like elements, and wherein: 
     FIG. 1 shows a schematic block diagram of a guidance system of the present invention; and 
     FIG. 2 shows an exploded view of a vehicle and a guidance system of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows a schematic block diagram of a guidance system  1  of the present invention. System  1  comprises sensors  10  to detect structural disturbances. Sensors  10  may include gyros and/or accelerometers. Preferably, sensors  10  include inertial rate gyros. Sensors  10  are coupled to a platform or casing  12  of a vehicle. Whenever platform  12  is subjected to outside forces, sensors  10  detect the disturbance and measure it. 
     Sensors  10  are operatively coupled to a control system  20 . When sensors  10  detect and measure a disturbance, this information is transmitted to control system  20 . Control system  20  may then affect other components of guidance system  1  based on the information received from sensors  10 . 
     A first active mirror  30 , a second active mirror  31 , and a third active mirror  32  are operatively coupled to sensors  10  and control system  20 . Mirrors  30 ,  31 ,  32  are “active mirrors” because their movement is controlled by a motor or by a magnetic system. Mirrors  30  and  31  are single rotation moveable mirrors that are used to resolve large angle slow disturbances and target direction in the pitch and yaw of the tracking system. Mirror  32  is a dual axis mirror used to resolve small, fast disturbances in the pitch and yaw of the tracking system. Mirrors  30 ,  31 ,  32  can move back and forth, tip, tilt, etc. Preferably, each mirror  30 ,  31 ,  32  is constrained to rotate about a single axis, with the axis of rotation of mirror  30  being substantially perpendicular to the axis of rotation of mirror  31 . In this manner, the viewing capability of mirrors  30 ,  31  is maximized while minimizing the number of mirrors required. Mirrors  30 ,  31  are movable to maintain a line of sight on a target  100 . Mirrors  30 ,  31 ,  32  are moved by control system  20  in response to information received from sensors  10 . Mirrors  30 ,  31 ,  32  in conjunction with control system  20  can also determine whether and to what extent target  100  has moved. That is, guidance system  1  can be used to seek a moving target  100 . 
     Sensors  10  may take a variety of designs. For example, sensors  10  may comprise separate sensors  10 , with each mirror  30 ,  31 ,  32  being coupled to a separate sensor  10 . Alternatively, sensors  10  may comprise a plurality of sensors  10  connected together, with a composite signal being sent from the plurality of sensors  10  to all mirrors  30 ,  31 ,  32 . Preferably, sensors  10  comprise a plurality of sensors  10  arranged to measure disturbances about each of the three-dimensional Cartesian axes. 
     Information received from mirrors  30 ,  31  is sent to a focus device  40 . A preferred focus device  40  is an infrared telescope. Focus device  40  is operatively coupled to mirrors  30 ,  31  to receive information measured by mirrors  30 ,  31 . Focus device  40  focuses the image from mirrors  30 ,  31  onto mirror  32 , which is then reflected back by an optical device  50 , passed through special filters and then onto an image plane. Optical device  50  may be used with focus device  40  to process the image. Optical device  50  may also be used to bend the image around other equipment to provide a clean image at the focal plane. Optionally, guidance system  1  may comprise signature signal processing equipment  60 , which may be used for a variety of purposes, including identification of target  100  and discrimination between target  100  and other objects. 
     All of the information received by control system  20 - including information measured by sensors  10 , possible movement of target  100 , etc.- is fed to control system  20  where it is put into a calculation to determine jitter or other disturbances and the position of target  100 . A signal is then sent from control system  20  to mirrors  30 ,  31 ,  32  to keep a line of sight on target  100 . Information is also sent from control system  20  to flight control equipment  70 , thereby steering the vehicle on which guidance system  1  is used to point the vehicle toward target  100 . 
     Optionally, guidance system  1  may comprise a receiver  80 . Receiver  80  can receive a signal from a remote user to control mirrors  30 ,  31 ,  32  and control system  20 . In this manner, a user can use guidance system  1  to remotely control the flight of the vehicle on which guidance system  1  is used. 
     FIG. 2 shows an exploded view of a vehicle  2  and a guidance system  1  of the present invention. Vehicle  2  can take a variety of forms. A preferred form of vehicle  2  is a missile. In prior guidance systems using gimbals, it was necessary to provide damping devices, such as shock and vibration mitigating devices, to protect the gimbals. Such damping devices are not necessary with guidance system  1  of the present invention. Rather, guidance system  1 , also known as a seeker, can be coupled directly to the casing  110  of vehicle  2 . Sensors  10  sense the rate of any structural disturbance. Active mirrors  30 ,  31 ,  32  are commanded to move counter to the direction of the disturbance so the overall effect is to keep the image stable on the focal plane. Image smearing and/or jitter is significantly reduced or eliminated. Guidance system  1  is designed to operate with structural disturbances as large as- 50 Gs axial acceleration, 15 Gs lateral acceleration, 4 kilometers per second forward motion, and up to 400 Hz structural vibration. Windows  120  may be provided to facilitate a line of sight between mirrors  30 ,  31 ,  32  and target  100 . 
     While the preferred embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not of limitation. It will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus the present invention should not be limited by the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.