FR2487971A1 - APPARATUS FOR DETERMINING THE NORTHERN DIRECTION - Google Patents

Abstract

THE PRESENT INVENTION RELATES TO AN APPARATUS FOR DETERMINING THE DIRECTION OF THE NORTH. APPARATUS CHARACTERIZED IN THAT BY THE FACT THAT THE FIVE SIGNAL PROCESSING MEANS SERVING TO DETERMINE NORTHERN DIRECTION INCLUDE: A) MEANS 44, 46, 48 FOR STORING THE SIGNALS PROVIDED TO THE FIRST TORQUE GENERATOR 36 IN POSITION 0, POSITION 90 AND POSITION 180, B) MEANS 50, 52 FOR FORMING THE HALF-DIFFERENCE OF SIGNALS STORED IN POSITION 0 AND IN POSITION 180, C) MEANS 54 FOR DIVIDING THE SIGNAL THUS OBTAINED BY THE HORIZONTAL COMPONENT OO COSPH OF EARTH ROTATION.

Description

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  The invention relates to an apparatus for determining

  direction of the north, comprising: a frame of azi-

  mut rotatably mounted about an azimuth axis, a two-axis gyroscope disposed on the azimuth frame and having a torsion axis lying in a plane perpendicular to the azimuth axis, a first axis of entry

  gyroscope being parallel to the azimuth axis and the

  x the gyroscope's input axis being perpendicular to the torsion axis and the first input axis, first and second sensors respectively on the first and second

  second axis of entry of the gyroscope, a first and a second

  x torque generators respectively on the first and second input axes of the gyroscope, the first sensor disposed on the first input axis being connected to the

  second torque generator that is mounted on the second

  the gyroscope's input axis, the second sensor

  placed on the second input axis being connected to the first torque generator, which is mounted on the first input axis of the gyroscope, a servomotor for rotating the azimuth frame about the azimuth axis, an angular position transmitter disposed on the azimuth axis, a switchable control device receiving

  the angular position transmitter signal and com-

  mandating the servomotor so that the azimuth frame can be rotated at a position O where the torsion axis of the gyroscope is parallel to an axis integral with the apparatus, at a position 90 or at a position 180 O position, signal processing means serving

  to determine the direction of the north and to which

  the signals fed to the first torque generator.

  It is known (DE-A-2 545 025) a navigation apparatus for land vehicles in which the angle between the torsion axis of the gyroscope and the direction of the north is determined by means of a meridian gyroscope suspended at a link and whose moment of recovery is compensated by an antagonistic moment. We align on the direction of the north thus determined a free gyroscope,

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  which is used for navigation as a heading reference device. Such a north-auto-search heading reference aircraft thus operates in two stages: before

  to begin the journey, we determine the direction of the north.

  An initial alignment of the heading reference apparatus is made from this north direction. Then,

  the heading reference apparatus, in the service of reference

  direction, continually determines the course of the vehicle,

  reported to this north direction.

  From DE-A-2 741 274, it is known to determine the direction of the north not by means of a gyroscope with horizontal torsion axis, suspended from a link, but with the aid of a biaxial gyroscope whose torsion axis is arranged vertically. The biaxial gyroscope comprises, on each of two horizontal input axes perpendicular to each other, a sensor and a torque generator. The output signals of the sensors are in each case cross-referenced, via an amplifier, to the torque generator mounted on the respective other input axis. The signals applied to the torque generators

  correspond to the components of the horizontal component

  earth rotation. Starting from the ratio of the two signals, we obtain the initial value of the heading angle. To correctly obtain this initial value

  when the torsion axis of the gyro, located in the di-

  of the yaw axis of the vehicle, is not exactly

  vertical to the surface of the earth, it is pre-

  seen two accelerometers that provide the position of obli-

  city of the vehicle. Starting from the signals of the accelerometers and the signals applied to the two torque generators

  of the reversing gyroscope, it is determined in a

  the initial value of the reported heading angle

  a coordinate system integral with the earth.

  In the arrangement according to the aforementioned DE-A 2,741,274, the same biaxial gyro is used as cap-position reference apparatus, after a pivoting of 90, the torsion axis being substantially horizontal and the 2487th calculator, starting from angular velocities and signals from accelerometers and taking into account the values

  initials determined during the initial alignment, cal-

  Constantly calculates the position of the vehicle and in particular continuously calculates the true heading angle. In both cases, based on the heading angle and the vehicle speed measured in the longitudinal axis of the vehicle, the position of the vehicle in a

  geographic system or a network coordinate system.

  It is true that the known provisions described

  provide the position of the vehicle with great accuracy.

  if we. However, they are too expensive for many applications.

  while there are, on the other hand,

  where the requirements for navigational accuracy are lower but a reference device is required

less expensive heading.

  By the German patent application DE-2 922 412.2-

  52 we know a north-north cap-position reference apparatus in which the north direction is also determined by an initial alignment

  and, in cape reference service, we then

  an angle of course for navigation. The known heading reference apparatus comprises an azimuth frame rotatably mounted about an azimuth axis. On the azimuth frame is a biaxial gyroscope whose torsion axis is located in a plane perpendicular to the azimuth axis, a first input axis of the gyroscope being parallel to the azimuth axis and the second input axis of the gyroscope being perpendicular to the torsion axis and the first input axis. On each of the first and second input axes of the gyroscope are mounted first and second sensors. In addition, on each of the first and second input axes of the gyroscope are mounted first and second torque generators. The second sensor disposed on the second input axis is connected to the first torque generator mounted on the first axis

  gyro input. The signal applied to the first

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  torque generator for the initial alignment is at the same

  applied to means of determining the direction of

  north. The azimuth frame can be rotated around the azimuth axis by a servomotor. In addition, on the azimuth axis is disposed an angular position transmitter. In the northward-looking known capposition reference apparatus, the azimuth frame is mounted in a roll frame so as to be rotatable about the substantially vertical azimuth axis and the roll frame is in turn mounted so as to be pivotable about the longitudinal axis of the vehicle. The biaxial gyro is of the rotating type. Not only is the second sensor connected to the first torque generator, but, in addition, similarly to DE-A-2 741 274, the first sensor mounted on the first input shaft is connected to the second mounted torque generator. on the second input axis of the gyroscope. Finally, on the azimuth frame is still mounted an accelerometer whose axis

  input is parallel to the torsion axis of the gyroscope.

  In a first mode of operation "north search" or "initial alignment", the azimuth frame, with the

  roll frame, can be aligned around the longitudinal axis

  the vehicle in such a way that the azimuth axis is

  located in a vertical plane passing through the longitudinal axis

  the vehicle. In a second operating mode "capposition reference", the azimuth frame, with the roll frame, may be aligned about the longitudinal axis

  the vehicle in such a way that the azimuth axis is parallel

  leash to the yaw axis of the vehicle.

  The azimuth frame may rotate about the azimuth axis, relative to the roll frame, under the action

  of the azimuth servomotor, to take a choice of

  where the torsion axis is parallel to the longitudinal axis

  tudinal-vehicle or a position making an angle of

  with the first.

  In the first mode of operation "search of

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  north, "the calculator, starting from the signals of the gyros-

  biaxial cope, measured and stored in both positions of the azimuth frame and representing the rotational speed

  around the second input axis and acceleration signals

  of the accelerometer, also measured and stored in these positions, provides the initial deviation between a vertical plane passing through the longitudinal axis of the vehicle and the

  meridian plane (initial gap of north).

  In the second operating mode "cap-position reference", the azimuth frame rotating at the position, the computer, starting from the angular velocity signals of the reversing gyroscope, provides a signal

  representing the true heading of the vehicle.

  Also in this known arrangement, as in the previously mentioned DE-A-2,741,274, a calculator, starting from the two signals of the two-axis gyroscope and the signals of the accelerometer, calculates the direction of the north as well. initial alignment as the heading angle in

  the operating mode "cap-position reference".

  The advantage of the provision according to the German patent application DE 2 922 412.2-52 lies in the fact that with

  economic mechanical means, we obtain a simpli-

  significant application of signal processing relatively

  at the disposal according to DE-A-2 741 274.

  However, here too, the expense is still too great for many applications, while in many

  In some cases, achievable precision is not even necessary.

  The invention aims to give an apparatus of the species defined above such a simple constitution

  as far as possible, mechanically and mechanically

signals.

  According to the invention, this problem is solved by the fact that the signal processing means used to determine the north direction comprise:

  a) means for memorizing the signals brought to the first

  first torque generator in the 0 O position, the posi-

90 and 180,

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  (b) means of forming the half-difference of

  registers in the position 0 and in the position, c) means of division of the signal thus obtained by the horizontal component A) C = -C ECos5 of the

Earth rotation.

  In the apparatus according to the invention, the direction of the north is determined from the components of the rotation.

  by means of a biaxial gyroscope subject to

  geometrically. The signal processing is thus very simple and by measuring in different angular positions of the

  framework of azimuth, significant sources of error in gyro-

  used cope are compensated. As a result, the requirements

  as to the accuracy of the gyroscope could be reduced.

  In the position for northern research, the gyros

  The cope can then be used as a cap-position reference apparatus and the momentary position angles, including the heading angle, are each determined from the angular velocities measured by the gyroscope, taking into account the initial position determined during of the initial alignment. The invention is explained more precisely below with reference to three exemplary embodiments shown in the accompanying drawings, in which: FIG. 1 is a schematic perspective view of a

  first embodiment of a cap-position reference apparatus

  Figure 2 shows a part of the signal processing means for the determination of the elements C31 and C32 of

  the direction cosine matrix for transforming

  of a coordinate system integral with the apparatus in a coordinate system integral with the earth, FIG. 3 shows part of the processing means of FIG.

  signals for the determination of the element Cil of the

  of the direction cosine, Figure 4 shows a part of the processing means of

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  signals for the determination of the C12 element of the

  steering cosine, Figure 5 shows part of the processing means

  signals for determining the trigonal function

  of the azimuth angle to the north from the elements of the direction cosine matrix, Figure 6 is a schematic perspective view of a

  second simplified embodiment of apparatus for the de-

  termination of the north direction, and Figure 7 shows the corresponding signal processing means,

  FIG. 8 shows, in a modified embodiment of

  yens signal processing, the means of determination

  coarse trigonometric functions of the angle of azimuth

  to the north, FIG. 9 shows, in this modified embodiment, the determination of the precise value of the azimuth angle as well as the determination of the heading angle, FIG. from the northern research process,

  Figure 11 shows a variant of the means of determining

  the trigonometric functions and shows how the error angle of the gyro

  Figure 12 shows a variant of the means of determining

  the exact value of the azimuth angle and how the gyro mounting error angle is taken into account.

  The cap-position reference apparatus searches

  north of Figure 1 has an azimuth frame

  mut 10 rotatable about an azimuth axis z. The azimuth frame defines a coordinate system with C C

  the x, y and zC coordinate axes. On the frame of azi-

  mut 10 is arranged a gyroscope 12 whose torsion axis H C is parallel to the x axis. The gyroscope defines a coordinate system comprising the z axis, a first input axis

  y parallel to the azimuth axis zC and a second axis of

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KK

  perpendicular to the torsion axis z and the first

  K input axis y. The azimuth frame 10, with its x, y and zC coordinate system, can rotate around the c

  of the azimuth axis z in relation to a coordinate system

  X, Y and Z are integral with the casing, the coordinate axis z being parallel to the coordinate axis z and the x and y coordinate axes being parallel, in the position O 0 which is represented, to the axes of coordinates xC and y of the azimuth frame 10. The rotation angle of the azimuth frame 10 about the azimuth axis x C, starting from the

  0 position shown, is designated by z Preferably

  the co-ordinate coordinate system of the cabinet is

  parallel to a coordinate system of the

  hicle, with the axes of coordinates which are the axis

  longitudinal axis x of the vehicle, the transverse axis yF of the vehicle

  hicle and yaw axis zF of the vehicle.

  On the first input axis yK of the gyroscope 12 are mounted a first sensor 14 and a first generator of K torque 16. On the second input axis x of the gyroscope 12

  mounted a second sensor 18 and a second genera-

  torque converter 20. The first sensor 14 disposed on the first input axis is connected thereto via an amplifier 22 on the second generatrix of torque

  mounted on the first input axis xK of the gyroscope 12.

  The second sensor 18 disposed on the second axis of

  xK is connected via an amplifier 24 to the first torque generator 16 mounted on the first input axis yK of the gyroscope 12. In this way, the gyroscope is electrically secured to its casing around its axes. 'Entrance. This is a gyroscope

  turning biaxial. The signals T2, Tl brought to the genera-

  Torque transducers 16 and 20 are picked up through respective filters 26, 28 and ducts in a manner described in FIG.

  further, to the signal processing means.

  On the azimuth axis zC is mounted a servomotor 30 for rotating the azimuth frame 10 around the azimuth axis z. On the azimuth axis z is, in addition,

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  disposed an angular position transmitter 32. A

  positive switchable control 34 receives the signal from the

  angular position transmitter 32 and controls the

  in such a way that the azimuth frame 10 can be rotated as desired at the position 0 shown K o the axis of rotation z of the gyroscope is parallel to an axis x integral with the apparatus at a position 90 or

a position 180.

  On the azimuth frame 10 are arranged a first accelerometer 36 whose sensitivity axis is parallel

  to the torsion axis z of the gyroscope and a second acceleration

  rometer 38 whose sensitivity axis is parallel to the

  x the input axis x of the gyroscope 12. The signals Ux and Uy of the first and second accelerometers are also fed, via respective filters 40, 42,

  to the signal processing means.

  The portions of the signal processing means that serve for the initial alignment are represented by the

Figures 2 to 5.

  The signal processing means comprise means 44, 46, 48 for memorizing the signals -T2I, -T2190 -T21180 fed to the first torque generator

  16, respectively in the positions 00, 90 O and 180.

  The signal processing means further comprise means 50, 52 for forming the half-difference of the signals stored in the position 0 and in the position, and means 54 for dividing the signals thus obtained by the horizontal component J. c JI B. cos + earth rotation. In addition, the signal processing means comprise means 56, 58 for forming the average of the signals supplied to the first torque generator 16 and stored in the memories 44.

  and 48 in positions 0 and 180 O, means 60 serving

  subtracting from this average the signal -T2 90 me-

  memorized in memory 46 in position 90 and

  means 62 for dividing the signal thus obtained by the com-

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  horizontal pose J c = n- E.cos of the rock

earthly tation.

  In the embodiment of FIG. 1, account is also taken of any obliquity of the azimuth frame during the initial alignment. This is ensured by

  signals from accelerometers 36 and 38.

  Correspondingly, the processing means of

  signals to determine the north direction

  in addition, means 64, 66 for dividing the accelerometer signals by the negative terrestrial acceleration to generate signals representing the elements C31

  and C32 of the direction cosine matrix for the trans-

  forming an x, y, z coordinate system integral with the apparatus to a coordinate system integral with the earth having north, east and vertical. In

  in addition, means 68 (FIG. 4) of multiplication are provided.

  of the signal C thus obtained by the vertical component

  hold Q E. sin + of earth rotation, - E

  being the speed of rotation of the earth and the

  study. In addition, there are means 70 for adding the product obtained Q s. c32 to the mentioned half-difference of the signals stored in the memories 44 and 48, before the division mentioned by the horizontal component of the earth's rotation (by the means 54), this division providing a signal which represents the element C12 of the

matrix of direction cosine.

  Similarly, means 72 are provided for multiplying the signal C31 by the vertical component = -α E. cos of the earth's rotation, as well as means 74 for adding the difference mentioned between the signal stored in the memory 46 and the average of

  signals stored in memories 44, 48 to the product

  of the signal C31 and the vertical component, prior to division by the horizontal component of the earth rotation, this division providing a signal which represents the element C of the cosine matrix of

direction (Figure 3).

  In addition, as shown in FIG. 5, signal forming means representing the sinus are provided.

  and the cosine of the azimuth angle to the north.

  These means for forming the sine and the cosine of the azimuth angle to the north comprise means 76 for dividing the signal Cl by -C 2, which gives a signal representing the cosine of the azimuth angle to the north. , cos tf. In addition, means 78 are provided for multiplying the signal C12 by -c and means 12 31 are for multiplying the signal cos t by C31.C32. The product signal thus obtained is added, by adding means 82, to the product of the signal C12 by the root. Means are provided to divide the sum as well

  obtained by the negative element -C33 of the cosine matrix

  direction, which gives a signal representing the sine of the azimuth angle to north sin. We

  gets the element C33 from the cosine matrix of direc-

  starting from the elements C31 and C32 determined according to FIG. 2, by the relation c33 = 31 32 To also eliminate the errors, which are not compensated by the measurement in position O and in position O and by the combination described of the stored signals thus obtained, at the mentioned difference in

  memorized in the memoirs 44 and 48 are opposed

  recording of the signal stored in the memory 44 in position O by the scale factor error DSF and the product of the x signal stored in the memory 46 at position 90 0 by a factor representing the mounting error angle M xy C of the gyroscope around the azimuth axis z. With the difference mentioned between the average of the signals memorized in

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  memories 44 and 48 (FIG. 3) and the memorized signal

  in memory 46, the product of the

  in the memory 44 in position O o by a factor

  representing the mounting error angle oC of the gyros

  xy cope around the azimuth axis z and superimpose the product of the signal stored in the memory 46 in position

  o by the DSF scale factor error.

  In the embodiment according to FIGS. 1 to 5 are further provided means 86, 88 and 90, 92 for storing the signals of the two accelerometers 36, 38 in each of the positions 0 o and 180 o. In addition, the signal interpreting means comprise means 94, 96 and 98, 100 serving to form the half-differences of the signals stored in the 0 o and 180 o positions for each of the two accelerometers 36, 38, as signals

  of accelerometer for the division by the acceleration ter-

  as shown in 64 and 66 in Figure 2. At

  signal of the first accelerometer 36, formed as half

  difference of the memorized signals, the product of the

  signal of the first accelerometer 36 stored in the posi-

  O o by the scale factor error DK of this x

  accelerometer 36 as well as the signal product of the

  x accelerometer 38 stored in the position O o by

  a factor E corresponding to the angle error of

  xz stage of the first accelerometer 36 about the azimuth axis C z. At the signal of the second accelerometer 38, formed as a half-difference of the stored signals, the signal product of the second accelerometer 38 stored in the position O o is contrasted by the scale factor error DK of this accelerometer and the product the signal y first accelerometer 36 stored in the position O o by a factor É corresponding to the yz angle error mounting the second accelerometer 38 about the azimuth axis z. In this way, we obtain the components C31 and C32 of the direction cosine matrix, corrected

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  for the errors of the components used, which allows

  to reduce the requirements for the accuracy of

  sants. It is simply necessary that the errors of the components are known. They can be determined by a calibration process before delivery of the device. For the

  same reason, in the mode of execution described, in the differ-

  mentioned between the average of the signals stored in the memories 44 and 48 and the signal stored in the

  memory 46, the signal of the first accelerator is superimposed

  meter 36 stored in the position O, divided by the scale factor SF of this accelerometer and multiplied x by a factor m representing the unbalance drift of the gyroscope and opposes the product of the signals of the first

  and second accelerators 36, 38 stored in the memories

  res 86, 90 in the position O, each divided by the corresponding scale factor SF, SF, multiplied by xy a factor representing twice the anisoelasticity 2n of the gyroscope 12. This is shown in Figure 3 by the block 102 and the summation point 104 as well as by the

  block 106 symbolizing a multiplication and block 108.

  As indicated in FIG. 4 by the block 110 and the summing point 112, at the mentioned half-difference of the signals stored in the memories 44 and 48 is superimposed the product of the signal of the second accelerometer 38 stored in the OO position by a factor m representing the

unbalance drift of the gyroscope 12.

  A simplified embodiment is shown in Figures 6 and 7. In this embodiment, the basic constitution is similar to that of the previous one. The corresponding parts therefore relate to Figures 6 and 7 the same references as the previous ones. In the embodiment of FIGS. 6 and 7, it is assumed that the frame

  of azimuth 10, by its azimuth axis z, is exactly

  vertically for the initial alignment or in all

  In this case, deviations from the vertical are neglected.

  geable. In this case, the signal processing means

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  for the initial alignment are simplified as shown in FIG. 7. The division by the horizontal component of the earth rotation, represented by the blocks 54 and 62, then provides sin tj and cos t respectively directly. The accelerometer signals become zero and the respective elements C12 and C11 of the direction cosine matrix are directly -sin t and cos

  The elements C31 and C32 of the cosine matrix of direc-

  disappear, while the C33 element of the

  steering cosine becomes 1.

  In operation with cap-position reference, during travel, the continuous calculation of the heading angle is carried out as described in the German patent application DE 29 22 414.4-52 where the axes of the gyroscope are arranged in the same manner. way that in the execution mode

  described above. In relation to the aforesaid

  The advantage gained is that there is no longer a need to rotate the gyroscope around a horizontal axis.

* In the apparatus according to Figures 6 and 7, to obtain

  to achieve maximum precision of northern research,

  account for the scale factor error of the gyro-

  cope as well as an error of mounting angle of the gyros-

  C cope around the azimuth axis z. Here is described a mode of execution in which we can do without

  count by calculating a scale factor error.

  The mechanical structure of the variant is practical-

  the same as in Figure 6. The Azimuth Frame 10

  may, however, also by virtue of an appropriate constitution

  requested from the control device 34, to turn under the action of the servomotor 30 at the position 270 in which one therefore has X = 270 O z

  The signal processing means for deter-

  north of the direction of the north comprise, in addition to the memories for storing the signals supplied to the first torque generator 16 in the position O, the position

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    and the position 180, a memory 114 serving to

  moriser the signals brought to the first torque generator

  16 in position 270. Means 50, 52 are also

  provided for forming the half-difference of the signals stored in the memories 44, 48 in the 0 O position.

  and in position 180. Similarly, the means of

  North-direction signals also comprise means 116, 118 serving to form the half-difference of the signals stored in the memories.

  46, 114 in the 90 O position and in the 270 position.

  As in the embodiment of FIG. 7, means 54 are provided for dividing the half-difference of the signals stored in memories 44 and 48 by the component

  horizontal it = AL cos of the terrestrial rotation.

  As in FIG. 7, a signal is obtained which represents the negative sine of the azimuth angle -sin y m. Similarly, in the embodiment of FIG.

  FIG. 8, means 120 are provided for dividing the half

  difference of the signals stored in the memories 46, 114 by the horizontal component - c = n E. cos @ of the terrestrial rotation. This division gives a negative cosine value of the azimuth angle -cos y * The values thus obtained of-sin y and -cos

  are obtained without exact knowledge of the error of

  scale. By a scale factor error, they may be inaccurate. However, they determine the quadrant in which the azimuth angle is located to the north. Correspondingly, means are provided for determining the quadrant of the north azimuth angle based on sinus values.

  and negative cosines of this angle, obtained by the di-

  visions in 54 and 120 without exact knowledge of an error

scale factor.

  Means are furthermore provided for determining, independently of the scale factor, the absolute value

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  a trigonometric function of the azimuth angle to the north. These means are represented by FIG.

  described in detail below. In addition,

  means for determining a corresponding angular value

  less than 90 O, starting from the absolute value

  the trigonometric function, and means of deter-

  azimuth angle to the north, starting from the specified angular value and determined quadrants

according to the sine and the cosine.

  The embodiment described is based on the idea that

  on the one hand, it is possible, according to

  nometrics of the azimuth angle, influenced by an erosion

  scale factor, to determine the quadrant of

  this angle, and. that, on the other hand, it is possible to

  a trigonometric function of the azimuth angle, unaffected by a scale factor error, but which, however, is ambiguous with respect to the azimuth angle itself. Starting from the quadrant determined by one channel and the trigonometric function determined by the other channel, for example from the absolute value of the sinus, it is possible to

  then determine the effective value of the azimuth angle.

  Correspondingly, the signal processing means comprise, in addition, means for determining

  azimuth angle to the north, according to the

  mentioned and the quadrant determined from the sinus

and the cosine.

  In detail, this embodiment presents the constitution

  As can be seen from Figure 8, means 122,

  124 are expected to divide the half-differences

  born by (1 + DSF) before division by the horizontal component <of terrestrial rotation, DSF being a c x

  accepted scale factor error. For the first

  ration, we can admit, for example, DSF = O or

  an estimated or known value can be introduced by

  ximation. The arrangement of FIG.

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  the means for determining the absolute value of a trigonometric function of the azimuth angle, means

  determining (1 + DSF) according to the memory signals

  in the memories 44, 48, 46, 114, which are described more precisely below. A signal (1 + DSF) appears at an output 126. Means 128, 130 are provided to introduce the new value of (1 + DSF) thus determined in the means mentioned 122, 124 for the multiplication. The means for determining the absolute value of a

  trigonometric function of the azimuth angle are

  shown in Figure 9. They include means 132 serving

  to form the difference of the signals stored in the

  moires 44, 48 in the 0 O position and in the position

  180, means 134 for squaring this dif-

  and means 136 for forming the difference of the signals stored in the memories 46, 114 in position and in position 270 O, means 138 for squaring this difference and means for adding the squares thus obtained. Means 142 are provided to extract the root of the sum of the squares obtained and the

  144 to form the quotient of the first difference.

  given by the means 132, by the root of the sum of the squares, so that a signal representing the absolute value of the sine of the north azimuth angle is obtained, | sin Y t. The means for determining the corresponding angular value are formed by

  means 136 for generating the arc-sine function.

  The means for determining the quadrant determine

  the quadrant of the azimuth angle from the following relationship

  vante: Quadrant I sin tj> 0 cos 0 O It sin Y -, O cos d O III sin Y <0 cos <0 IV sin Y <O cos Ä> O i

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  With the quadrant thus determined and the value of t '| calculated according to FIG. 9, angle Y is obtained

  effective, not influenced by errors in

  scale, according to the relationship Quadrant Angle of azimuth I y = {t | II M> = 180 - + t III ^ ç = 180 + | t

IV = 360

  The aforesaid means for determining (1 + DSF) are formed, as shown in FIG. 9, of means 148 serving to divide the mentioned root of the sum of the squares by twice the horizontal component 2SX c of the earth's rotation, and which provide a current value of (1 + DSF) at output 126. This is applied

  present value at means 122 and 124 for multiplying

  tion. The described arrangement allows a precise measurement,

  which is not impaired by scale factor errors.

  Thus, it is not necessary to take into account, by

  ass, scale factor errors. Another condition of the arrangement described so far is that the mounting error angle of the gyroscope 12 about the azimuth axis z can be reduced to a negligible value. If this is not possible or if it represents an excessive expenditure, the angle can be taken into account.

  mounting error according to Figures 11 and 12, provided that

  that it has, on the one hand, been determined, and, on the other hand, stored in the calculator. This is possible1 since the mounting error angle hardly varies

not with time.

  Figure 11 essentially corresponds to the provision

  of Figure 8 and Figure 12 corresponds essentially to

  4 and the corresponding parts have the same references. According to

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  FIG. 11, the product of the half-difference of the signals stored in memories 44, 48 in position 180

  by a factor d representing the angle error of

  As indicated by block 150 and summing point 152, the gyroscope 12 is rotated about the azimuth axis z at the half-difference of the signals stored in the memories 46 and 114 at position 90 O and position 270. . Similarly, the product of the half-difference of the signals stored in the memories 46 and 114 in position 90 O and in position 270 by the factor i (representing the mounting angle error of the gyroscope 12 around the axis d azimuth z is opposite, as indicated by the block 154 and the summing point 156, to the half-difference of the signals stored in the memories 144,

  148 in position 0 O and in position 180.

  Similarly, in Figure 12, when determining

  of the absolute value of the trigonometric function of the azimuth angle, the product of the difference of the signals stored in the memories 46 and 114 in position 90 and in

  position 270 O, formed at 136, by a factor t represented

  sensing the mounting angle error of the gyroscope 12 about the azimuth axis z is opposite, as indicated by the block

  158 and the point of summation 160, unlike

  registers stored in memories 44 and 48 in position 0 and in position 180 O, formed at 132. The product of the difference of the signals stored in memories 44 and 48 in position 0 O and in position 180 O, formed at 132, by the factor oC y representing the mounting angle error of the gyroscope 12 about the azimuth axis z is opposite, as indicated by the block 162 and the summing point 164, unlike the signals stored in the memories 46, 114 in position 90 and in position 270 O.

  Figure 10 is a table of the progress of the process

northern research.

  Instead of accelerometers, you can also use

  other vertical detectors, for example levels.

2487971

  It is then necessary to modify the signal processing according to

  the nature of the signals of these vertical detectors.

21 2487971

Claims (17)

R E V E N D I C A T IO N S   Apparatus for determining the north direction, comprising: an azimuth frame rotatably mounted about an azimuth axis, a two-axis gyroscope disposed on the azimuth frame, and torsion axis is located in a plane perpendicular to the axis   of azimuth, a first axis of entry of the gyroscope being parallel   aligned with the azimuth axis and the second input axis of the gyro-   cope being perpendicular to the torsion axis and the first   input axis, first and second sensors respectively   on the first and second input axes of the gyro-   first and second torque generators   respectively on the first and second input axes of the gyroscope, the first sensor disposed on the first input axis being connected to the second torque generator which is mounted on the second input axis of the gyroscope, the second sensor disposed on the second input axis being connected to the first torque generator, which is mounted on the first input axis of the gyroscope, a servomotor for rotating the azimuth frame about the azimuth axis, a transmitter angular position arranged on   the azimuth axis, a switchable control device   transmitting the angular position transmitter signal and controlling the servomotor so that the azimuth frame can be rotated to a position O o   the torsion axis of the gyroscope is parallel to a solid axis   from the device, at a 90 position or at a position   O, signal processing means for determining   the north direction and to which the signals fed to the first torque generator are applied   characterized in that the means of   Signals used to determine the north direction include:   a) means (44, 46, 48) for memorizing the signals   born at the first torque generator (36) in position O, position 90 O and position 180 O, 22 2487971   b) means (50, 52) for forming the half-difference   signals stored in position 0 and in the po- 180 ', -   c) means (54) for dividing the signal thus obtained by the horizontal component. Earth rotation.   2. Apparatus according to claim 1, characterized by   d) averaging means (56, 58) for   stored signals fed to the first torque generator in the position 0 O and in the position 180 O, e) means (60) for subtracting from this average the signal stored in the position 90 O, f) means (62) of division of the signal thus obtained by the horizontal component Qc = n E cos of the Earth rotation.   3. Apparatus according to claim 2, characterized by the following points: a) on the azimuth frame (10) are arranged a first vertical detector, for example an accelerometer (36) whose sensitivity axis is parallel to the torsion axis (z) of the gyroscope and a second vertical detector> for example an accelerometer (38) whose sensitivity axis is parallel to the second input axis (x) of the gyroscope (12),   (b) the signal processing means for the determination of   direction of the north include, in addition:   b1) means (64, 66) for dividing the acceleration signals   romate by the negative terrestrial acceleration for the obtain-   signals representing the elements C31 and C32 of the direction cosine matrix for transforming a coordinate system integral with the apparatus to a coordinate system integral with the earth, b2) means (68) for multiplying the signal C32 by the vertical component _Q = l E Sin t of the earth's rotation, f being the speed of rotation of the earth and t the latitude, b3) means (70) for adding the product obtained IL s C32 to the half -difference mentioned of the stored signals before the division mentioned by the horizontal component of the earth rotation, this division providing a signal representing the element C12 of the direction cosine matrix, b4) means (72) of multiplication of the signal C31 by   the vertical component ú = úSince of rotation   b5) means (74) for adding the aforesaid difference between the stored signal and the average to the aforesaid product of the signal C31 by the vertical component before the division mentioned by the horizontal component of the earth's rotation, this division providing a signal, which represents the element Cil of the direction cosine matrix, and   b6) means (FIG. 5) for forming signals representing   sensing the sine and cosine of the azimuth angle to the North.   4. Apparatus according to claim 3, characterized in that the means for forming the sine and the cosine of the azimuth angle to the north comprise: a) means (76) for dividing the signal C11 by   V 1 - CU? v which gives a signal representing the cosi-   north of the azimuth angle, cos t b) means (78) for multiplying the C12 signal by 1-C 2 1   c) means (80) for multiplying the signal cos t by C31.C32, d) means (82) for adding the product signal thus obtained to the quotient of the signal C12 by the root, and e) means (84) ) of division of the sum thus obtained by the negative element -C33 of the direction cosine matrix, which gives a signal representing the sine of the azimuth angle to the north, sin t 5. Apparatus according to any one of claims 2 to 4, characterized by the following: a) the mentioned difference in the stored signals is opposite to the product of the signal stored in the 0 o position by the scale factor error DSF and the product of the x   signal stored in position 90 o by a representative factor   both the mounting angle error "of the gyroscope around xy C of the azimuth axis z, and b) at the difference mentioned of the mean and the stored signal are superimposed the product of the signal stored in position 0 O by a factor representing the mounting angle error i / of the gyroscope around the xy axis of azimuth z and the product of the signal stored in position   O by the DSF scale factor error. x   6. Apparatus according to any one of the claims   1 to 5, characterized in that it comprises: a) means (86, 88; 90, 92) for storing the signals of the two accelerometers (36, 38), each time in the OO position and in the 180 O position, and   b) means (94, 96, 98, 100) for forming half   differences of the signals memorized in the O o position and in the 180 o position for each of the two accelerometers (36, 38) as accelerometer signals for the division by the terrestrial acceleration.   Apparatus according to claim 6, characterized by the following points: a) at the signal of the first accelerometer (36) formed as a half-difference of the stored signals are opposite the product of the signal of the first accelerometer (36) stored in the OO position by the scale factor error DK x35 of this accelerometer (36) and the product of the signal of this accelerometer (36) and the product of the signal of the second accelerometer (38) stored in position 0 o by   a factor ú corresponding to the angle error of   first accelerometer (36) around the azimuth axis   C mut z, and b) at the signal of the second accelerometer (38), formed as a half-difference of the stored signals, is opposite the signal product of the second accelerometer (38) stored in position O o by the factor error of scale DK y   of this accelerometer (38) and at the signal of this same acceleration   rometer (38) is superimposed the product of the signal of the first accelerometer (36) stored in position OO by a factor yz corresponding to the mounting angle error C second accelerometer (38) around the azimuth axis z .   Apparatus according to any of the claims   1 to 5, characterized by the following points: a) the difference between the average of the stored signals and the stored signal al) is superimposed the signal of the first accelerometer (36) stored in position 0 o, divided by the factor of scale SF of this accelerometer and multiplied by a factor m X representing the unbalance drift of the gyroscope, and a2) is opposite the product of the signals of the first and second accelerometers (36, 38) stored in the position 0 o, each divided by the corresponding scale factor   SFx, SFy, by a factor representing twice the   gyroscope 2n soelasticity, and b) to the mentioned half-difference of stored signals   is superimposed the signal product of the second accelerator   meter (38) memorized in position O O by a factor m   presenting the unbalance drift of the gyroscope.   Apparatus according to claim 1, characterized by the following:   (a) the azimuth frame may, in another switching state,   of the control device, turn the actuator to a position 270 O under the action of   (b) the signal processing means for the determination of   tion of the north direction further comprise: b1) means for storing the signals supplied to the first torque generator in the position 270 O, b2) means for forming the half-difference of the signals stored in position 90 and in FIG. position 270, b3) means for dividing the signal thus obtained by the   horizontal component a% = c cos of rotation   b4) means for determining the quadrant of the azimuth angle to the north from the values of the negative sine and the cosine of this angle, obtained by the divisions without exact knowledge of a factor error. scale, b5) means for determining the absolute value of a trigonometric function of the azimuth angle to the north, independently of the scale factor, b6) means for determining an angular value   less than 90%, based on the absolute value   of the trigonometric function, and b7) means for determining the azimuth angle to   north according to the angular value mentioned and the   drant, determined from the sine and the cosine.   10. Apparatus according to claim 9, characterized   in that it comprises means for multiplying half   differences mentioned by (1 + DSF) before division by the horizontal component of the Earth's rotation,   DSF is an accepted scale factor error.   x 11. Apparatus according to claim 10, characterized in that it comprises: a) means for determining (1 + DSF) according to the stored signals, and b) means for introducing the new value of   (1 + DSF), thus determined, in the means of multiplying cation.   Apparatus according to any of the claims 27 2487971   9 to 11, characterized in that the means for deter-   quadrant determination determine the quadrant of the azimuth angle tj from the following relationship Quadrant I sin? 0 cos4>> 0 II sint7 O cos <t O III sin O4 c Cos4t <0 IV sin O cos t > O   Apparatus according to any of the claims   9 to 12, characterized in that the determination means   the absolute value of a trigonometric function com-   relate: a) means for forming the difference of the signals stored in position 0 and in position 180 O, b) means for forming the square of this difference, c) means for forming the difference of the signals stored in position 90 and in position 270 D, d) means for forming the square of this difference, e) means for adding the squares thus obtained, f) means for extracting the root of the sum of squares obtained, and   (g) means of training the quotient of the first   by the root of the sum of the squares, which gives a signal representing the absolute value of the sine of the azimuth angle to the north Isin y 1 Apparatus according to claim 13, characterized   in that the means for determining the angular value   corresponding field are formed of generating means for arc-sine function.   Apparatus according to claims 11 and 13, characterized   characterized in that the aforementioned means for determining (1 + DSF) are formed by means of dividing the root mentioned by twice the horizontal component of Earth rotation   Apparatus according to any one of the claims   9 to 15, characterized by the following points: 28 2487971   a) the product of the half-difference of the signals stored in position 0 and in position 180 by an OC factor representing the mounting angle error of the gyroscope about the azimuth axis z is opposite to the half-difference of the signals stored in position 90 and in position 270 to, and b) the product of the half-difference of the signals stored in position 90 O and in position 270 by the factor cC y which represents the error of mounting angle of the gyroscope around the azimuth axis z is opposite the half-difference   signals stored in position 0 O and position 180.   Apparatus according to claims 13 and 16, characterized   characterized in that in determining the absolute value of the trigonometric function of the azimuth angle a) the product of the difference of the signals stored in position 90 O and in position 270 O by a factor 0 (_ xy   representing the mounting angle error of the gyroscope   rotation of the azimuth axis is opposed to the difference in   registers stored in position 0 and in position 180 O, and b) the product of the difference of the signals stored in position 0 and in position 180 0 by the factor a   representing the mounting angle error of the gyroscope   rotation of the azimuth axis is opposed to the difference in   stored in position 90 and position 270.