Method and self-contained system for harmonizing equipments on board a vehicle, using means of measuring the earth's gravitational and magnetic fields

A method for harmonizing an equipment (2) relative to a vehicle (1), said equipment (2) being installed fixedly on board said vehicle (1) which, relative to a first absolute reference system (RM), has an orientation defined by a second reference system (R2) tied to said vehicle (1), said equipment (2) being subjected to the earth's gravitation field represented by a gravity vector g oriented along its gradient, as well as to the earth's magnetic field represented by a vector H oriented along its gradient, and the orientation of said equipment (2) being defined, relative to said first absolute reference system (RM), by a third reference system (R3), this equipment (2) comprising a device (3,4) for measuring the components of said gravity vector g, fixed to said equipment (2);

• and said vehicle (1) carrying a computer (6);
• a memory (7) associated with said computer (6);
• an equipment magnetometer (11), fixed to said vehicle (1), whose orientation, relative to said first absolute reference system (RM), is referenced by a fourth reference system (R4);
• and a first link (5) connecting said equipment (2) and the equipment magnetometer (11) to said computer (6) and to said memory (7), said method comprising the following steps:
• disposing, fixedly on board the vehicle (1), a gravity-sensing apparatus (8) harmonized relative to the vehicle and a utility magnetometer (10) harmonized relative to said gravity-sensing apparatus (8), said gravity-sensing apparatus (8) and said utility magnetometer (10) being connected to said computer (6) and to said memory (7) by a second link (9);
• placing the vehicle (1) in a first fixed position relative to the ground, corresponding to a first positioning (R21) of said second reference system (R2) relative to said first absolute reference system (RM);
• measuring, with the gravity-sensing apparatus (8), the values of the components of a vector g1, representing the earth's gravitational field g sensed by the gravity-sensing apparatus (8) in the second reference system (R2), and transforming said values into reference gravitational data indicative of said values measured by the gravity-sensing apparatus (8);
• measuring, with said utility magnetometer (10), the values of the components of a vector H1, representing the earth's magnetic field H sensed by said utility magnetometer (10) in the second reference system (R2), and transforming said values into reference magnetic data indicative of said values measured by the utility magnetometer (10);
• storing in the memory (7) said reference gravitational data, indicative of said values measured by the gravity-sensing apparatus (8), as well as said reference magnetic data, indicative of said values measured by the utility magnetometer (10);
• measuring, with said equipment (2), the values of the components of a vector g2, representing the earth's gravitational field g sensed by said equipment (2) in the third reference system (R3), and transforming said values into measured gravitational data indicative of said values measured by said equipment (2);
• measuring with said equipment magnetometer (11), the values of the components of a vector H2, representing the earth's magnetic field H sensed by said equipment magnetometer (11) in the fourth reference system (R4), and transforming said values into measured magnetic data indicative of said values measured by the equipment magnetometer (11);
• storing in the memory (7) said measured gravitational data indicative of said values measured by said equipment (2), as well as said measured magnetic data, indicative of said values measured by the equipment magnetometer (11);
• calculating a first rotation operator R1 (.alpha., .beta., .GAMMA.) in the computer (6), from said reference gravitatinal data, said reference magnetic data, said measured gravitational data, and said measured magnetic data to correct the angular errors of harmonization between the second reference system (R2) of said vehicle (1) and the third reference system (R3) of said equipment (2) according to the relationship:
• ##EQU9## storing the first rotation operator R1 (.alpha., .beta., .GAMMA.) in the computer (6);
• and
• applying the first operator R1 (.alpha., .beta., .GAMMA.) to the angle of roll, the angle of pitch attitude and the angle of heading of the equipment (2) to give subsequent measured gravitational data indicative of subsequent values measured by said equipment (2), as well as subsequent measured magnetic data indicative of subsequent values measured by the equipment magnetometer (11).

A system for harmonizing an equipment means (2) relative to a vehicle (1), said equipment means (2) being installed fixedly on board said vehicle (1) which, relative to a first absolute reference system (RM), has an orientation defined by a second reference system (R2) tied to said vehicle (1), said equipment means (2) being subjected to the earth's gravitational field represented by a gravity vector g oriented along its gradient, as well as to the earth's magnetic field represented by a vector H oriented along its gradient, and the orientation of said equipment means (2) being defined, relative to said first absolute reference system (RM), by a third reference system (R3), and wherein said vehicle (1) carries measuring means (11), fixed to said vehicle (1), whose orientation, relative to said first absolute reference system (RM), is referenced by a fourth reference system (R4), said system comprising:

• a gravity-sensing apparatus comprising means (8) for measuring the values of the components of a vector g1, representing the earth's gravitational field g in the second reference system (R2) and for transforming said values into reference gravitational data indicative of the values measured by the means (8);
• means (10) for measuring the values of the components of a vector H1 representing the earth's magnetic field H in the second reference system (R2) and for transforming said values into reference magnetic data indicative of the values measured by the means (10);
• a memory comprising means (7) for storing said reference gravitatinal data, indicative of the values measured by the means (8) and said reference magnetic data, indicative of the values measured by the means (10);
• equipment means (2) for measuring the values of the components of a vector g2, representing the earth's gravitational field g in the third reference system (R3), and for transforming said values into measured gravitational data indicative of the values measured by the means (2);
• an equipment magnetometer comprising means (11) for measuring the values of the components of a vector H2, representing the earth's magnetic field H in the fourth reference system (R4), and for transforming said values into measured magnetic data indicative of the values measured by the means (11);
• a computer comprising means (6) for calculating a first rotation operator R1 (.alpha., .beta., .GAMMA.) from said reference gravitational data, said reference magnetic data, said measured gravitational data, and said measured magnetic data to correct the angular errors of harmonization between the second reference system (R2) of said vehicle (1) and the third reference system (R3) of said equipment (2) according to the relationships:
• .alpha.=.phi.1-.phi.2
• .beta.=.theta.1-.theta.2
• .GAMMA.=.OMEGA.1-.OMEGA.2=0
• .phi.1, .theta.1 and .OMEGA.1 being respectively the angle of roll, the angle of pitch attitude and the angle of heading of the vehicle (1), which are determined from said reference gravitational data and from said reference magnetic data, and .phi.2, .theta.2, and .OMEGA.2 being respectively the angle of roll, the angle of pitch attitude and the angle of heading of the equipment means (2), which are determined from said measured gravitational data and from said measured magnetic data;
• means for applying said first rotation operator R1 (.alpha., .beta., .GAMMA.) to angles .phi.2, .theta.2, and .OMEGA.2 determined subsequently from subsequent measurements to give subsequent measured gravitational data indicative of subsequent values measured by said equipment means (2), as well as subsequent measured magnetic data indicative of subsequent values measured by the measuring means (11);
• and
• a link connecting said equipment means (2) and said equipment magnetometer to said computer and to said memory.

A system for harmonizing an equipment means (2) relative to a vehicle (1), said equipment means (2) being installed fixedly on board said vehicle (1) which, relative to a first absolute reference system (RM), has an orientation defined by a second reference system (R2) tied to said vehicle (1), said equipment means (2) being subjected to the earth's gravitational field represented by a gravity vector g oriented along its gradient, as well as to the earth's magnetic field represented by a vector H oriented along its gradient, and the orientation of said eqiupment means (2) being defined, relative to said first absolute reference system (RM), by a third reference system (R3) and wherein said vehicle (1) carries measuring means (11), fixed to said vehicle (1), whose orientation, relative to said first absolute reference system (RM), is referenced by a fourth reference system (R4), said system comprising:

• a gravity-sensing apparatus comprising means (8) for measuring the values of the components of a vector g1, representing the earth's gravitational field g in the second reference system (R2) and for transforming said values into reference gravitational data indicative of the values measured by the means (8);
• means (10) for measuring the values of the components of a vector H1 representing the earth's magnetic field H in the second reference system (R2) and for transforming said values into reference magnetic data indicative of the values measured by the means (10);
• a memory comprising means (7) for storing said reference gravitatinal data, indicative of the values measured by the means (8) and said reference magnetic data, indicative of the values measured by the means (10);
• equipment means (2) for measuring the values of the components of a vector g2, representing the earth's gravitational field g in the third reference system (R3), and for transforming said values into measured gravitational data indicative of the values measured by the means (2);
• an equipment magnetometer comprising means (11) for measuring the values of the components of a vector H2, representing the earth's magnetic field H in the fourth reference system (R4), and for transforming said values into measured magnetic data indicative of the values measured by the means (11);
• a computer comprising means (6) for calculating a first rotation operator R1 (.alpha., .beta., .GAMMA.) from said reference gravitational data, said reference magnetic data, said measured gravitational data, and said measured magnetic data to correct the angular errors of harmonization between the second reference system (R2) of said vehicle (1) and the third reference system (R3) of said equipment (2) according to the relationship:
• ##EQU11## means for applying said first rotation operator R1 (.alpha., .beta., .GAMMA.) to the angle of roll, the angle of pitch attitude and the angle of heading of the equipment means (2) determined subsequently from subsequent measurements to give subsequent measured gravitational data indicative of subsequent values measured by said equipment means (2), as well as subsequent measured magnetic data indicative of subsequent values measured by the measuring means (11);
• and
• a link connecting said equipment means (2) and said equipment magnetometer to said computer and to said memory.