Device, and related method, for determining the direction of a target

Abstract

The invention concerns the field of sighting or aiming means and more particularly a device ( 1 ) for determining the direction of a target in a predefined frame and of the type having sighting means ( 10 ), means having a sighting member ( 13 ), three gyrometers ( 14 1 , 14 2 , 2 14 3 ) arranged along three axes in different planes, means for control ( 16 ), means ( 20 ) for resetting said sighting means ( 10 ) and means ( 30 ) for processing signals derived from the sighting means ( 10 ), said processing means being capable of determining the direction between the sighting means ( 10 ) and the target and of transmitting it to imaging means or to external means, and also means ( 16 ) for controlling the transmission to the imaging means ( 40 ) or to external means, of representative values of the direction between the sighting means ( 10 ) and the target, this device being characterized in that the resetting means comprise at least one non gyroscopic sensor ( 17 ) arranged on the sighting means ( 10 ) and capable of emitting a signal for its transmission to the said processing means.

1 . A device capable of determining the direction of a target in a predefined frame of reference and of the type having sighting means ( 10 ), means having a sighting member ( 13 ), three gyrometers ( 14   1 ,  14   2 , 14   3 ) arranged along three axes in different planes, means for control ( 16 ), means ( 20 ) for resetting said sighting means ( 10 ) and means ( 30 ) for processing signals derived from the sighting means ( 10 ), said processing means ( 30 ) being capable of determining the direction between the sighting means ( 10 ) and the target and of transmitting to imaging means ( 40 ) or to external means ( 50 ,  60 ) and also means ( 16 ) for controlling the transmission to the imaging means ( 40 ) or to external means ( 50 ,  60 ), of representative values of the direction between the sighting means ( 10 ) and the target, this device being characterized in that it comprises at least one non gyroscopic sensor ( 17 ) arranged on the sighting means ( 10 ) and capable to emit a signal for its transmission to the said processing means ( 30 ), and in that the processing means are capable of determining a terrestrial frame of reference from the signals derived from the said gyrometers ( 14   1 ,  14   2 , 14   3 ) and from the said non gyroscopic sensor ( 17 ).  
     
     
         2 . The device as defined in  claim 1 , wherein the sighting means ( 30 ) are capable of determining on the one hand, the direction of a line D 1  parallel to the earth's rotation axis and going through point P where the sighting means are, by processing the signals derived from the gyroscopes, and on the other hand, the direction of the vertical D 2  of the location associated to point P, by processing the signals derived from the said non gyroscopic sensor.  
     
     
         3 . The device as defined in any one of  claim 1  or  2 , wherein the axes of the terrestrial frame are the vertical of the location, geographical north, geographic east or geographic west.  
     
     
         4 . The device as defined in any one of claims  1  through  3 , wherein the said at least one non-gyroscopic sensor ( 17 ) is composed of one two axes inclinometer or at least two indinometers.  
     
     
         5 . The device as defined in any one of claims  1  through  3 , wherein the said “at least one sensor” has one multi-axes accelerometer or at least two accelerometers.  
     
     
         6 . The device as defined in any one of claims  1  through  3 , wherein the said “at least one sensor” has one electronic imaging sensor.  
     
     
         7 . The device as defined in  claim 6 , wherein the one electronic imaging sensor is capable of generating a representative imaging signal, and which is transmitted to processing means of this signal capable of determining the position of a pattern in the said image.  
     
     
         8 . The device as defined in  claim 7 , wherein the processing means associated to the imaging electronic sensor allow compensating the operator tremors.  
     
     
         9 . The device as defined in any one of claims  7  through  8 , wherein the processing means of the sighting means are capable of compensating the operator tremors, with the value of the optical field of the electronic imaging sensor.  
     
     
         10 . The device as defined in any one of claims  8  through  9 , wherein the processing means of the sighting means, are capable of determining the angular field of the electronic imaging sensor from the relationship between the operator tremors derived from the signal of the electronic sensor, and the signal of the sighting means.  
     
     
         11 . The device as defined in any one of claims  6  through  10 , wherein the processing means of the sighting means are capable of generating, from the signals of the electronic image sensor, and the sighting means, a signed image.  
     
     
         12 . The device as defined in  claim 11 , wherein the processing means of the sighting means are capable of reconstituting the global landscape from the signed images, with position information for different zones of the latter.  
     
     
         13 . The device as defined in any one of claims  11  through  12 , wherein it is constituted by display means of the said signed images and/or of the rebuilt the landscape.  
     
     
         14 . The device as defined in any one of claims  1  through  13 , wherein the processing means are capable of participating to the transmission of identification elements of the target, and/or to the detection of the absolute direction of the sighting means.  
     
     
         15 . The device as defined in any one of claims  1  through  14 , wherein it is constituted by recording means of the signal coming from the electronic imaging sensor, and/or it comprises display means of the said images and also of some information such as the direction of the aimed target, its range and/or its nature.  
     
     
         16 . The device as defined in any one of claims  1  through  3 , wherein the said at least one sensor utilizes at least two electromagnetic receivers.  
     
     
         17 . The device as defined in claims  16 , wherein it comprises an electromagnetic emitter.  
     
     
         18 . The device as defined in any one of claims  1  through  17 , wherein it has three optical gyrometers, for example fiber-optic gyrometers.  
     
     
         19 . The device as defined in any one of claims  1  through  18 , wherein the processing means have a power supply and calculating and management means using a software program that performs several functions.  
     
     
         20 . The device as defined in  claim 19 , wherein the software program performs three main functions: 
 Target designation function, which causes data to be acquired from the sighting instrument and processes them to obtain the desired elevation and azimuth;    Transmission function, which sends the azimuth and elevation data for display on the imaging means and/or for the purpose of a weapon system;    Absolute position function, which allows correction at regular intervals of the sighting instrument's drift due to the use of gyrometers.    
     
     
         21 . The device as defined in  claim 20 , wherein the software program also performs a display function of the operational status of the invention.  
     
     
         22 . The device as defined in any one of claims  1  through  3 , wherein the said positioning radio means, such as satellite means of GPS type, constitutes at least one sensor.  
     
     
         23 . The device as defined in any one of claims  1  through  22 , wherein the sighting means comprise the acquisition of the geographic position by radio means, such as satellite means of GPS type.  
     
     
         24 . The device as defined in any one of claims  1  through  23 , wherein the sighting means have a rangefinder.  
     
     
         25 . The device as defined in any one of claims  1  through  24 , wherein the processing means comprise triangulation means, capable of performing a discreet telemetry.  
     
     
         26 . The resetting process of the device capable of determining the direction of a target in a predefined frame of reference and of the type having sighting means ( 10 ), means having a sighting member ( 13 ), three gyrometers ( 14   1 ,  14   2 , 14   3 ) arranged along three axes in different planes, and having at least one non gyroscopic sensor ( 17 ), these elements being capable of emitting a signal for its transmission to the said processing means ( 30 ), the processing means ( 30 ) being capable of determining the direction between the sighting means ( 10 ) and the target, is characterized in that it comprises a stage consisting in determining a terrestrial frame of reference from the signals derived from the said gyrometers ( 14   1 ,  14   2 ,  14   3 ) and from the said non gyroscopic sensor ( 17 ).  
     
     
         27 . A process as defined in  claim 26 , which includes a step that determines, on the one hand the direction of a line D 1  parallel to the earth's rotation axis and going through point P where the sighting means ( 10 ) are, by processing the signals derived from the gyroscopes, and on the other hand, the direction of the vertical D 2  of the location associated to point P, by processing the two signals derived from the said sensor.  
     
     
         28 . A process as defined in  claim 27 , which includes an additional step that determines the geographic north direction, this direction being obtained by the intersection of the plane defined by the D 1  and D 2  lines with the plane perpendicular to D 2  and coming through P.  
     
     
         29 . A process as defined in  claim 26 , which utilizes on the one hand sighting means comprising at least three sensors, that is to say, three electromagnetic receivers, and on the other hand the device comprises an electromagnetic emitter, the process being characterized in that the processing means ( 30 ) compute the position and the orientation, that is to say the attitude of the sighting means ( 10 ) by processing the signals derived from the magnetic sensors and of the cartography of the magnetic field expected, which has been loaded before in the memory of the these processing means.  
     
     
         30 . A process as defined in  claim 30 , which utilizes sighting means composed of an electronic imaging sensor, such as a camera rigidly fastened to the sighting means, this camera generating a signal representative of the image observed, the process being characterized in that it uses a step that makes the imaging process capable of determining the position of a pattern in the said image, the position of this pattern being known.  
     
     
         31 . A process as defined in  claim 30 , wherein the said second frame of reference is a geographic frame of reference with respect to a pattern whose position doesn't change or changes very little.  
     
     
         32 . A process as defined in any one of claims  26  through  31 , wherein it includes a stage of calculation of K, T and R angles by the processing means, defined as follows:  
       Knowing that: 
 P is the point of the earth surface where the sighting means are;  
 R T  (X t , Y t , Z t ) is a reference frame associated to point P and connected to the earth, X t  axis being the horizontal West to East axis oriented towards East, Y t  axis being the horizontal South to North axis oriented towards North, and Z t  axis being the vertical axis oriented upwards.  
 R MV  (X s , Y s , Z s ) is a frame of reference connected to the sighting means ( 10 ) integrating the three gyrometers ( 14   1 ,  14   2 ,  14   3 ) and the said at least one non gyroscopic sensor,  
 the successive rotations of a −K angle about Z t  axis, then of a −T angle about the axis resulting from the previous rotation applied on X t  axis, then of a −R angle about the axis resulting from the two previous rotations, applied on Y t  axis,  
 put the frame of reference R T  on the R MV  frame of reference.  
 
     
     
         33 . A process as defined in any one of claims  26  through  32 , wherein the processing means ( 30 ) include a step by which they determine the value of the gravity vector either in a continuous process or in a step by step one carrying out process at T 0 , T 1 , T i  , T n , of the signals sent by the gyroscopes or the said at least one non gyroscopic sensor ( 17 ) arranged on the sighting means ( 10 ).  
     
     
         34 . A process as defined in  claim 33 , wherein it computes in a first step the expression of the R T  (T i ) frame of reference into the R MV  (T i  ) frame of reference, through the implementation of the following rotations: 
 the rotation of a −α angle, which is a function of the elapsed time between instants T 0  and T i              (       α       T   i     -     T   0         =     15      °        /        h       )                     about the pole axis oriented from the South to North, that is to say, around the rotation axis of the earth, and which is only a function of point P latitude where the sighting means ( 10 ) are, in the frame of reference R T  (T O ) or R T  (T i );    the rotations of −K, −T, and −R angles previously mentioned;    the rotation which results from the integration of the incremental angles measured by the gyrometers;    and wherein, in a second stage, it determines K, T, and R angles, either by an inversion process of the equalization made of the computed and of the measured values of the gravity vector, or by a minimization process of the error function, by use of an algorithm aimed to seek the minimum value of a function of many parameters calculated on a sample of data, for example, by use of an algorithm of simple down hill type or of simulated annealing type, or by use of any one of dedicated algorithms, such as quadratic programming of Karmakar, More and Toraldo.    
     
     
         35 . A process as defined in any one of claims  31  through  34 , wherein it comprises a step for determination of the latitude of the place where the sighting means are.  
     
     
         36 . A process as defined in  claim 32 , wherein the said second step consists in computing latitude L as a complement of K, T and R angles.  35 / 36