TITLE: System and method for automatic harmonization of position and/or orientation between equipment on board a mobile carrier and a reference frame of said mobile carrier

The present invention relates to a system and a method for automatic harmonization of position and/or orientation between equipment on board a mobile carrier and a reference frame of said mobile carrier, for example an aircraft.

The invention lies in the field of the use of equipment on board mobile carriers, and finds a particular application in the field of airborne radar systems.

In this field, it is necessary to know the precise orientation of the line of sight of the on-board radar system with respect to a reference frame of the mobile carrier, on the one hand to perform processing and compensate for the movements of the carrier in the system of radar, and on the other hand to correctly display the output data of the radar system with respect to the mobile carrier.

For example, radar systems comprising one or more antenna panels, fixed in a distributed manner at several places on the carrier, are used. The mobile carrier is for example an airplane, a helicopter or a drone.

Conventionally, it is possible to perform precise mechanical calibration, using centering pins or dedicated wedges, to fix the position and orientation of the or each antenna panel with respect to the wearer in a known manner. However, such an operation requires mechanical parts and precise assembly, and is not suitable for use in which the on-board systems are regularly dismantled/reassembled, for example for maintenance or depending on the various missions to be carried out by the mobile carrier. .

It is also known to carry out an installation with less mechanical fixing precision, but to obtain an accurate measurement of the positioning of the on-board equipment, or of each antenna panel of the on-board equipment in the case of a radar system with multiple antenna panels. Such an accurate measurement is then used to perform digital compensation in the radar system.

For example, methods are known which use the acquisition of several images or of several targets (or targets) by the radar system, and the application of digital processing to calculate the position and/or the orientation of the on-board system in a reference frame of the wearer which is for example supplied by an inertial unit of the wearer. Such methods have the advantage of providing results automatically, but are dependent on the wearer's environment, and do not make it possible to obtain satisfactory results in all circumstances. For example, when optical sights are used, it is necessary to carry out measurements on the ground, in a harmonization procedure, which is particularly tedious in the event of disassembly and reassembly of the radar systems on a mobile carrier.

The object of the invention is to remedy the drawbacks of the state of the art, and to provide a method and a system for automatic harmonization of position and/or orientation between equipment on board a mobile carrier and a reference frame of said carrier. mobile adapted to operate independently of the wearer's environment.

To this end, the invention proposes an automatic position and/or orientation system between equipment on board a mobile carrier and a reference frame of said mobile carrier, said mobile carrier being equipped with an inertial unit adapted to provide measurements of acceleration and angular speed of rotation of said mobile carrier in said frame of reference. This system includes:

- at least one accelerometer mechanically coupled to the on-board equipment, and providing acceleration measurements in a so-called repository of the associated on-board equipment,

- a reception unit configured to receive measurements supplied by said inertial unit and measurements supplied by the accelerometer,

- a calculation unit configured to calculate values ​​of parameters defining a geometric transformation of passage between the frame of reference of the wearer and the frame of reference of the on-board equipment, from said measurements, carried out for at least two different flight orientations, by said control unit inertial and by said accelerometer.

Advantageously, the system for automatic harmonization of position and/or orientation between equipment on board a mobile carrier and a reference frame of the mobile carrier implements calculations on measurements carried out on the one hand by the inertial unit on board the wearer, on the other hand by the accelerometer(s) attached to the on-board equipment, without requiring any other measurements or adjustments.

The automatic harmonization system according to the invention can also have one or more of the characteristics below, taken independently or according to all the technically possible combinations:

The accelerometer is an accelerometer adapted to provide acceleration measurements along three spatial axes.

The mobile carrier is an aircraft, the on-board equipment is a radar system comprising at least one antenna panel, the or each antenna panel having an associated phase, and comprising an accelerometer mechanically coupled to the antenna panel and having a frame of reference centered on said phase center.

The passing geometric transformation includes a rotation and a translation, the rotation being defined by three angles of rotation and the translation being defined by a translation vector.

The calculation of parameter values ​​is performed by numerical resolution of a system of equations implementing a rotation matrix defining said rotation and said translation vector.

According to another aspect, the invention relates to a method for automatic harmonization of position and/or orientation between equipment on board a mobile carrier and a reference frame of the mobile carrier, implemented by a harmonization system such as briefly described above, and comprising steps, for at least two flight maneuvers corresponding to two different flight orientations, of:

- reception and storage of inertial data obtained from the measurements provided by the inertial unit in a repository of the inertial unit;

- reception and storage of acceleration data obtained from the measurements provided by an accelerometer in a repository of the on-board equipment associated with said accelerometer;

- calculation of values ​​of parameters defining a geometric transformation of passage between the frame of reference of the wearer and the frame of reference of the on-board equipment by using said stored inertial data and acceleration data.

The automatic harmonization method according to the invention can also have one or more of the characteristics below, taken independently or according to all technically conceivable combinations.

The calculation of parameter values ​​is performed by numerical resolution of a system of equations implementing a rotation matrix and a translation vector defining said geometric transition transformation.

The system of equations is obtained by the expression of an acceleration vector of the on-board equipment, supplied by the accelerometer, in the frame of reference of the mobile carrier and by the expression of the said acceleration vector of the

carrier on board in the frame of reference of the mobile carrier from inertial data provided by the inertial unit in the frame of reference of the mobile carrier.

The inertial data comprises an acceleration vector of the mobile carrier and a vector of angular speeds of rotation of the mobile carrier in the frame of reference of the mobile carrier.

The expression of an acceleration vector of the on-board equipment supplied by the accelerometer in the frame of reference of the mobile carrier, implements said rotation matrix.

The method is implemented for a plurality of flight maneuvers listed in a list of flight maneuvers, comprising a first subset of flight maneuvers at zero angles of rotation and a second subset of flight maneuvers comprising accelerations angles of the moving carrier.

According to another aspect, the invention relates to a computer program comprising code instructions which, when said program is executed by a computer, implement a process for automatic harmonization of position and/or orientation between equipment embedded on a mobile carrier and a repository of the mobile carrier as briefly described above.

According to another aspect, the invention relates to a non-volatile information recording medium on which is recorded a computer program comprising code instructions which, when said program is executed by a computer, implement a method automatic harmonization of position and/or orientation between equipment on board a mobile carrier and a repository of the mobile carrier as briefly described above.

Other characteristics and advantages of the invention will emerge from the description given below, by way of indication and in no way limiting, with reference to the appended figures, among which:

[Fig 1] FIG. 1 schematically illustrates a system for automatic harmonization of position and/or orientation between equipment on board a mobile carrier and a reference frame of the mobile carrier according to one embodiment of the invention;

[Fig 2] Figure 2 schematically illustrates an example of reference of the mobile carrier and reference of the on-board equipment;

[Fig 3] figure 3 is a flowchart of the main steps of a process for automatic harmonization of position and/or orientation between equipment

embedded on a mobile carrier and a repository of the mobile carrier according to one embodiment of the invention.

CLAIMS

1. Automatic position and/or orientation harmonization system between on-board equipment (6, 10) on a mobile carrier (4) and a reference (RIMU) of said mobile carrier, said mobile carrier (4) being equipped with an inertial unit (8) adapted to provide measurements of acceleration and angular speed of rotation of said mobile carrier in said frame of reference, characterized in that it comprises:

- at least one accelerometer (12) mechanically coupled to the on-board equipment (6, 10), and providing acceleration measurements in a so-called associated on-board equipment reference (RRAD),

-a reception unit (14) configured to receive measurements provided by said inertial unit (8) and measurements provided by the accelerometer (12),

- a calculation unit (20) configured to calculate values ​​of parameters defining a geometric transition transformation between the frame of reference (RIMU) of the wearer and the frame of reference (RRAD) of the on-board equipment, from said measurements, carried out for at least two different flight orientations, by said inertial unit (8) and by said accelerometer (12).

2. System according to claim 1, wherein said accelerometer (12) is an accelerometer adapted to provide acceleration measurements along three spatial axes.

3. System according to one of claims 1 or 2, wherein said mobile carrier (4) is an aircraft, said on-board equipment (6) is a radar system comprising at least one antenna panel (10), the or each panel antenna (10) having an associated phase, and comprising an accelerometer mechanically coupled (12) to the antenna panel (10) and having a reference frame (RRAD) centered on said phase center.

4. A system according to any one of claims 1 to 3, wherein the passage geometric transformation comprises a rotation and a translation, the rotation being defined by three angles of rotation and the translation being defined by a translation vector.

5. System according to claim 4, in which the calculation of parameter values ​​is carried out by numerical resolution of a system of equations putting

implements a rotation matrix defining said rotation and said translation vector.

6. Method for automatic harmonization of position and/or orientation between equipment on board a mobile carrier and a reference frame of said mobile carrier, implemented by a harmonization system in accordance with claims 1 to 5, and comprising steps , for at least two flight maneuvers corresponding to two different flight orientations, of:

- reception and storage (32) of inertial data obtained from the measurements provided by the inertial unit in a repository of the inertial unit;

- reception and storage (34) of acceleration data obtained from the measurements supplied by an accelerometer in a repository of the on-board equipment associated with said accelerometer;

- calculation (36) of parameter values ​​defining a geometric transformation of passage between the frame of reference (F½u) of the wearer and the frame of reference (RRAD) of the on-board equipment by using said stored inertial data and acceleration data.

7. Method according to claim 6, in which the calculation of parameter values ​​is carried out by numerical resolution of a system of equations implementing a rotation matrix and a translation vector defining said transition geometric transformation.

8. Method according to claim 7, in which said system of equations is obtained by the expression of an acceleration vector of the on-board equipment, supplied by the accelerometer, in the frame of reference of the mobile carrier and by the expression of said acceleration vector of the carrier on board in the frame of reference of the mobile carrier from inertial data provided by the inertial unit in the frame of reference of the mobile carrier.

9. Method according to claim 8, in which the inertial data comprise an acceleration vector of the mobile carrier and a vector of angular speeds of rotation of the mobile carrier in the frame of reference of the mobile carrier.

10. Method according to claim 8 or 9, in which the expression of an acceleration vector of the on-board equipment supplied by the accelerometer in the frame of reference of the mobile carrier, implements the said rotation matrix.

11. Method according to any one of claims 6 to 10, implemented for a plurality of flight maneuvers listed in a list of flight maneuvers, comprising a first subset of flight maneuvers with zero angles of rotation and a second subset of flight maneuvers comprising angular accelerations of the moving carrier.

12. Computer program comprising software instructions which, when executed by a computer, implement a process for automatic harmonization of position and/or orientation between equipment on board a mobile carrier and a reference frame of said moving carrier.