METHOD FOR HARMONISING TWO INERTIAL MEASUREMENT UNITS WITH ONE ANOTHER AND NAVIGATION SYSTEM IMPLEMENTING THIS METHOD

HARMONIZING METHOD OF TWO MEASUREMENT UNITS

INERTIAL WITH EACH OTHER AND NAVIGATION SYSTEM USING THIS METHOD WORK

The present invention relates to the field of inertial measurement of position and/or attitude,

STATE OF THE TECHNIQUE

An inertial unit (or INS. English "Inertial navigational system requirement") usually incorporates an inertial measurement unit (IMU or IMU data English "Inertial response measurement unites") which comprises heading with widely accelerometric arranged in the axes of re father measuring accelerometric sensors and three angu Cigarettes, gyros or gyros, for measuring angular elements in turn moves the accelerometric measuring mark relative to a reference orientation of the mark of Me safe. Each accelerometer includes a proof mass (or "proof on mass") subjected to gravity and acceleration of the object which is integral with the inertial unit (e.g. a vehicle). In the accelerometric measuring mark, the accelerometers measure a variable named specific force {"specifies strength" or "grams-force" in English) and determine the three components of a specific force vector. The force speci Weight is equal to the sum of the forces-inertrelies to which the inertial body is subjected, divided by the mass of the inertial body. The specific force thus has the dimension of an acceleration and in addition is also termed a "greedy acceleration" in English literature - frequently stopped.

The harmonization between a first and a second central eans release tab inertial unit which are included for cartography by a same vehicle is performed by calculating a rotation matrix for projecting the specific force vectors of the two inertial navigation systems in the same frame of reference. This harmonization cannot be sheave smoothed that using a browser program eans - release tab require relatively large ticks informed resources. Further, it is neces that both inertial navigation systems have a préci SiON is performing the anvil - representative.

OBJECT OF THE INVENTION

A goal of L^F. invention is to provide a means of harmonization that is reliable and is simple,

BRIEF EXPOSES THE INVENTION

To this end, there is provided, according to the invention, a method of matching a first inertial measurement unit and a second inertial measurement unit with each other, the first measuring unit and the second release tab eans inertial measurement unit being connected to a common control circuit and being arranged to determine a specific force vector and a ith person operating the instantaneous rotation; characterized in that the method comprises the steps of:

- to compare to each other, by the control unit, at least one of the two vectors determined by each inertial measurement unit to determine a deviation by taking account of a lever arm between the two inertial measurement units;

- determining by the controller a value of harmonization basis of said deviation by taking into account the moment arm between the two measurement units.

In the method of the invention, compared directly to one another in two specific force and/or both rotation vectors respectively, without passing through an inertial mark. It is therefore not necessary in the invention to perform a navigation or calculate a mark inertial to perform the comparison result, so it is not necessary to dispose of computer resources use control two measuring units the inertial accuracies equivalent. In one particular implementation, the control unit compares the two force vectors specific to determine a deviation of the two vectors specific force and instant of rotation for mining - ting a rotational deviation and determining the value of harmonization from the spacing of specific force and rotational deviation.

The harmonization is then particularly Formant perse.

The invention also relates to a vehicle navigation system, comprising a first inertial measurement unit and a second inertial measurement unit connected to an electronic control unit arranged to implement the method of the invention

According to a particular embodiment, the system includes an optronic apparatus comprising a base and a turret provided with a sighting device and my an overarching on the base for pivotal movement about a first axis, the second inertial measurement unit being mounted to the turret, and, preferably, the control unit is arranged to determine a line of sight of the sighting device from measurements of the second unit of Me secure inertial and launch it in a reference frame of the first inertial measurement unit.

Thus, it is possible to use the apparatus PO Tronic for navigation by sighting elements of the landscape whose position is known, as bitter or celestial objects.

Other features and advantages of the invention will be apparent in the description that follows of particular embodiments of the present invention non-limited the and spons,

BRIEF DESCRIPTION OF THE DRAWINGS

It will be made with reference to the accompanying drawings, among which: - Figure 1 is a schematic view in plan of a navigation system implementing the method of the invention;

- figure 2 is a schematic view of a milking stall Cusing - inertial system_?

- figure 3 is a view showing the position of the geometric specific force vector in the markings of the two inertial navigation systems;

- figure 4 is a schematic view in section of an inertial system according to the invention.

DETAILED DISCLOSURE OF THE INVENTION

With reference to the drawings, the invention relates to a navigation system for vehicle 1. The vehicle is here a ship but the invention applies the same rrta - of voice to other type vehicle, air or road.

The navigation system 1 here comprises an electronic control unit 10 is connected to an electro bench table geo satellite optronic apparatus 20 and 30.

The geo satellite 20 is arranged in a manner known in itself for operation with at least one of the constellations of GPS satellites, and Galileo, GLONASS receivers, BAIDU...

The apparatus 30 comprises optronic, so adapted - bare in itself, a base 40 and a turret 50 provided with a sighting device mounted on the base 60 and 50 to pivot about a first axis Al or bearing axis. The sighting device 60 is mounted in the turret 50 to pivot about an axis a2, or elevation axis, perpendicu - licable to the axis ai.

The base 40 includes a motor for adjusting the angular position of the turret 50, and thus the sighting device 60, about the axis ai, relative to the base 40. The base 40 also includes a first inertial unit. The turret 50 comprises a motor for adjusting the angular position of the sighting device 60, about the axis a2, 50 with respect to the turret.

The sighting device 60, known in itself, comprises a support frame supporting a set PO tick 61 62 behind which is mounted at least one electronic imaging sensor 63. The sighting device 60 KOM takes here further stabilizing device 64 conne cting the electronic imaging sensor 63 to the frame 61 - Sub wearing. The stabilizing device includes an AC - tionneurs, for example piezoelectric, connected to a control circuit arranged to move the sensor electro pathology picture 63 in response to signals from an inertial measurement unit coupled to the control circuit 100, 2 of the stabilization device.

The inertial unit comprises a unit of Me secure inertial 100, 1 incorporating three accelerometers 111, 1, 112, 1, 113, 1 arranged according to the axes Xl, -yl, a mark of Zl 01 ri of origin. The inertial measurement unit 100, 1 angular sensors comprises 121, 1, 122, 1,

123.1 are mounted with the axes Xl, -yl, of Zl. The angle sensors 121, 1, 122, 1, 123, 1 are here gyroscopes to axisymmetric resonator vibrating.

The inertial measurement unit 100, 2 includes three accelerometers 111, 2, 112, 2, 113, 2 arranged in the axes x2, y2, a mark z2 r2 original 02. Three heading with widely spaced angular 121, 2, 122, 2, 123, 2 are mounted in accordance with the axes x2, y2, z2. The accelerometers 111, 2, 112, 2,

113.2 and angular sensors 121, 2, 122, 2, 123, 2 are herein of microelectromechanical systems (MEMS English

"Microelectromechanical systems that"}.

The inertial measurement units 100, 1, 100, 2 are positioned so that the indicia are substantially aligned r2 ri and one on the other. An accuracy of a few degrees is sufficient due to the subsequent implementation of the harmonization process of the invention which will compensate for these few of sandstones deviation.

The inertial measurement units 100, 1, 100, 2 are arranged to measure the same specific force in the form of a force vector f-specific represented in Figure 3. The inertial measurement units 100, 1, 100, 2 are adapted to also allow BTS determinants of instantaneous rotation vector. It should be noted that, in the present embodiment, the two inertial measurement units 100, 1, 100, 2 are positioned adjacent one another, c'est i.e. sufficiently proximate to one another, to have therebetween a negligible to deflect the arm.

The electronic control unit 10 is arranged to implement a method for navigating through an algorithm twining hybridization signals from:

- the electronic unit geolocation Inspace litaire 20;

- means dead reckoning as the log, the timer and the caliper edge;

- the inertial unit incorporating the inertial measurement unit 100, 1;

- the optronic apparatus 30.

The hybridization signals of the crystallizing géoloca satellite 20 and the inertial unit 100, 1 such that the inertial unit incorporating the inertial measurement unit 100, 1 provides continuity of navigation in the absence of reception of the signals of the electronic unit geo satellite 20. This is known per se.

The control unit 10 is also arranged to perform hybridization signals of the satellite calisationgéolo 20 and means dead reckoning so that the dead reckoning allow continuity of navigation in the absence of reception of the signals of the satellite geolocation electro bench table 20. This is equal centeredly known per se.

The control unit 10 is further arranged to determine a line of sight of the sighting device 60 from measurements of the second measurement unit 100, 2 - eans release tab and launch it in a reference frame of the first inertial measurement unit 100, 1. For this purpose, the aiming device is aimed at 60 landmarks whose position is known, for example celestial objects and/or bitter.

In order for this navigation is exact, it is re quired to perform the harmonization of the first inertial measurement unit 100, 1 and the second inertial measurement unit 100, 2 with each other. The method of reconciliation is implemented by the control unit 10 and comprises the steps of;

- comparing the signals from the inertial safe - Me units 100, 1, 100, 2 and representative of the specific force vector and the instantaneous rotation vector to determine a deviation of specific force and a rotational deviation between the marks ri and r2 (the lever arm between the two inertial measurement units is here négli - HG);

- determining by the controller a value of harmonization from the spacing of specific force and rotational deviation (the lever arm between the two inertial measurement units is here négli - HG).

Comparing the specific force vectors is accomplished by comparing the outputs of accéléro beings

111, 1, 112, 1, 113, 1 to the outputs of the accelerometers 111, 2,

112, 2, 113, 2 respectively. The outputs of the accelerometers are compared in pairs here after a correc - action of normalizing the specific force vectors, the comparison of vectors snapshots of rotation is accomplished by comparing the outputs of the angular sensors 121, 1, 122, 1, 123, 1 to the outputs of the angular sensors 121, 2, 122, 2, 123, 2 respectively. The outputs of the angular heading with widely are compared in pairs here after a correction of the normalizing vectors snapshots of rotation. The outputs of the accelerometers and angular sensors are herein increments of speed, i. e. an average speed for a given time.

The value of harmonization is taken into account for projecting, in the mark LAN, the information of the re father bound to the viewing direction in order to be able Licences tert this information upon hybridization.

The method of reconciliation is performed périodiquement ensures that both power plants are always matched with each other. The reconciliation is here carried out in real time.

Of course, the invention is not limited to the disclosed embodiments but encompasses any variant within the scope of the invention as defined by the claims.

In particular, the two measuring units may be mounted - eans release tab in a same apparatus, as in the described embodiment, or in separate appliance.

The control unit may be integrated with the apparatus optronic or be separated therefrom.

The second inertial measurement unit 100, 2 may be separate from the optronic apparatus 30.

The first inertial unit incorporating the inertial measurement unit 100, 1 may be separate from the optronic apparatus 30.

If the inertial measurement units are moved away from each other, it will take into account the lever arm between the inertial measurement units, when comparing vectors therebetween and when determining the value of harmonization.

According to a degraded version of the method, it is possible to determine the value of harmonization from a single deviation determined by comparing either with widely ith specific force thirst vectors snapshots of rotation. The accuracy of the reconciliation is then less than in the method described above.