METHOD AND SYSTEM FOR DETERMINING THE WEIGHT AND CENTRE OF GRAVITY OF A STRUCTURE

Abstract

A method and system for determining the weight and at least a first coordinate of the center of gravity of a structure such as a vehicle, in particular, an aircraft.

Claims

1. A method for determining the weight (W) and/or at least a first coordinate (X) of the position of the centre of gravity of a structure, the method comprising the following steps: a) measuring the responses () of a first plurality of installed sensors located in sensitive load points of the structure, and b) determining the weight (W) and/or the first coordinate (X) of the position of the centre of gravity of the structure based on the measured responses (), as: $W = C_{w} + {.Math.}_{j_{w} = 1}^{k_{w}} .Math. .Math._{j_{w}} .Math._{j_{w}}$ $X = C_{x} + {.Math.}_{j_{x} = 1}^{k_{x}} .Math. .Math._{j_{x}} .Math._{j_{x}}$ wherein W is the weight of the structure, X is the first coordinate of the position of the centre of gravity of the structure on a plane of projection, k.sub.w and k.sub.x are natural numbers and are the responses measured by the first plurality of installed sensors, wherein the subscript in the response () denotes the sensor which has performed the measurement, wherein for determining the weight (W) a first group of sensors is used which comprises a number of installed sensors k.sub.w, for determining the first coordinate (X) of the centre of gravity a second group of sensors is used which comprises a number of installed sensors k.sub.x, and wherein coefficients .sub.j.sub.w, with j.sub.w=1, . . . k.sub.w, and .sub.j.sub.x, with j.sub.x=1, . . . k.sub.x, and constants C.sub.w and C.sub.x are previously determined applying the following calibration steps: i) locating a plurality of calibration sensors in sensitive load points of the structure, wherein the number of calibration sensors is m, m being a natural number, ii) loading the structure with a probe weight (Wp.sub.i), obtaining a loading state (i), and measuring the first coordinate (X.sub.i) of the position of the centre of gravity and the weight (W.sub.i) of the structure in said loading state (i), iii) measuring for each calibration sensor (r) the response (.sub.r,i) associated to the loading state (i), with r=1, . . . m, being r a natural number, iv) repeating steps ii) and iii) for a plurality of loading states (i), with i=1, . . . s, being s the number of loading states, s being a natural number, v) selecting groups of at least two calibration sensors and solving for each group an equation system with a number of equations (P) equal to or greater than N.sub.w+1, being N.sub.w the number of calibration sensors in the group, wherein the equation system is: $W_{1} = C_{w} + {.Math.}_{n = 1}^{N_{w}} .Math. .Math._{n, 1} .Math._{n}$ $.Math.$ $W_{P} = C_{w} + {.Math.}_{n = 1}^{N_{w}} .Math. .Math._{n, P} .Math._{n}$ .sub.n,q, with n=1, . . . , N.sub.w, being the measured responses of the calibration sensors and W.sub.q being the weight associated to the respective loading state q, q=1, . . . , P, wherein the equation systems are solved by least squares method, obtaining as a result weight coefficients (.sub.n) for n=1, . . . , N.sub.w, and weight constant (C.sub.w), vi) determining for each group of calibration sensors an estimated weight (We.sub.i) for each loading state (i) as ${We}_{i} = C_{w} + {.Math.}_{n = 1}^{N_{w}} .Math. .Math._{n, i} .Math._{n}$ wherein .sub.n,i are the responses of the calibration sensors of the group, associated to a loading state i, vii) selecting a first group of calibration sensors which fulfils that a first probable error (PE.sub.w) is minimum, wherein PE.sub.w is: ${PE}_{w} = C_{E} .Math. \sqrt{\frac{{.Math.}_{i = 1}^{s} .Math. .Math. {({We}_{i} - W_{i})}^{2}}{s - (N_{w} + 1)}}$ s being the total number of loading states, N.sub.w being the number of calibration sensors in said group of calibration sensors, and C.sub.E being a real positive number, viii) selecting groups of at least two calibration sensors and solving for each group an equation system with a number of equations (P) equal or greater than N.sub.x+1, being N.sub.x the number of calibration sensors in the group, wherein the equation systems is: $X_{1} = C_{x} + {.Math.}_{n = 1}^{N_{x}} .Math. .Math._{n, 1} .Math._{n}$ $.Math.$ $X_{P} = C_{x} + {.Math.}_{n = 1}^{N_{x}} .Math. .Math._{n, P} .Math._{n}$ .sub.n,q, with n=1, . . . , N.sub.x, being the measured responses of the calibration sensors and X.sub.q being the X-coordinate of the centre of gravity associated to the respective loading state q, q=1, . . . , P, wherein the equation systems are solved by least squares method, obtaining as a result X-coefficients (.sub.n) for n=1, . . . , N.sub.x, and X-constant (C.sub.x), ix) determining for each group of calibration sensors an estimated X-coordinate (Xe.sub.i) of the centre of gravity for each loading state (i), as ${Xe}_{i} = C_{x} + {.Math.}_{n = 1}^{N_{x}} .Math. .Math._{n, i} .Math._{n}$ wherein .sub.n,i are the responses of the calibration sensors of the group, associated to a loading state i, x) selecting a second group of calibration sensors which fulfils that a second probable error (PE.sub.X) is minimum, wherein PE.sub.X is: ${PE}_{X} = C_{E} .Math. \sqrt{\frac{{.Math.}_{i = 1}^{s} .Math. .Math. {({Xe}_{i} - X_{i})}^{2}}{s - (N_{x} + 1)}}$ s being the total number of loading states, N.sub.x being the number of calibration sensors in said group of calibration sensors, and C.sub.E being a real positive number, xi) selecting as the first plurality of installed sensors a plurality of calibration sensors including: the first group of calibration sensors selected in step vii), and the second group of calibration sensors selected in step x), wherein k.sub.w is the number of sensors in the first group of calibration sensors and k.sub.x is the number of sensors in the second group of calibration sensors.

2. The method according to claim 1, further comprising determining a second coordinate (Y) of the position of the centre of gravity of the structure, wherein the second coordinate (Y) of the position of the centre of gravity of the structure is determined based on the measured responses () of the first plurality of installed sensors, as: $Y = C_{y} + {.Math.}_{j_{y} = 1}^{k_{y}} .Math. .Math._{j_{y}} .Math._{j_{y}}$ wherein Y is the second coordinate of the position of the centre of gravity of the structure on a plane of projection, k.sub.y is a natural number and are the responses measured by the first plurality of installed sensors, wherein the subscript in the response denotes the sensor which has performed the measurement, wherein for determining the second coordinate (Y) of the position of the centre of gravity a third group of sensors is used which comprises a number of installed sensors k.sub.y, and wherein Y-coefficients .sub.j.sub.y, with j.sub.y=1, . . . k.sub.y, and Y-constant C.sub.y are previously determined applying the following calibration steps at least after steps i)-iv), wherein the step ii) further comprises measuring the second coordinate (Y.sub.i) of the position of the centre of gravity of the structure in each loading state (i): viii) selecting groups of at least two calibration sensors and solving for each group an equation system with a number of equations (P) equal or greater than N.sub.y+1, being N.sub.y the number of calibration sensors in the group, wherein the equation systems is: $Y_{1} = C_{y} + {.Math.}_{n = 1}^{N_{y}} .Math. .Math._{n, 1} .Math._{n}$ $.Math.$ $Y_{P} = C_{y} + {.Math.}_{n = 1}^{N_{y}} .Math. .Math._{n, P} .Math._{n}$ .sub.n,q, with n=1, . . . , N.sub.y, being the measured responses of the calibration sensors and Y.sub.q being the Y-coordinate of the centre of gravity associated to the respective loading state q, q=1, . . . , P, wherein the equation systems are solved by least squares method, obtaining as a result Y-coefficients (.sub.n) for n=1, . . . , N.sub.y, and Y-constant (C.sub.y), ix) determining for each group of calibration sensors an estimated Y-coordinate (Ye.sub.i) of the centre of gravity for each loading state (i), as ${Ye}_{i} = C_{y} + {.Math.}_{n = 1}^{N_{y}} .Math. .Math._{n, i} .Math._{n}$ where .sub.n,i are the responses of the calibration sensors of the group, associated to a loading state i, and x) selecting a third group of calibration sensors which fulfils that a third probable error (PE.sub.Y) is minimum, wherein PE.sub.Y is: ${PE}_{Y} = C_{E} .Math. \sqrt{\frac{{.Math.}_{i = 1}^{s} .Math. .Math. {({Ye}_{i} - Y_{i})}^{2}}{s - (N_{y} + 1)}}$ s being the total number of loading states, N.sub.y being the number of calibration sensors in said group of calibration sensors, and C.sub.E being a real positive number, wherein the first plurality of installed sensors further includes the third group of calibration sensors selected in step x) and wherein k.sub.y is the number of sensors in the third group of calibration sensors.

3. The method according to claim 2, further comprising the following steps: c) measuring the responses () of a second plurality of installed sensors located in at least one lifting surface (h) of the structure, and d) determining a corrected weight of the structure (W.sub.corrected) and/or a corrected position (X.sub.corrected, Y.sub.corrected) of the centre of gravity of the structure as: $W_{corrected} = W - {.Math.}_{h = 1}^{M} .Math. .Math. V_{h}^{}$ $X_{corrected} = \frac{X .Math. W - {.Math.}_{h = 1}^{M} .Math. .Math. (X_{h}^{} .Math. V_{h}^{})}{W - {.Math.}_{h = 1}^{M} .Math. .Math. V_{h}^{}}$ $Y_{corrected} = \frac{Y .Math. W - {.Math.}_{h = 1}^{M} .Math. .Math. (Y_{h}^{} .Math. V_{h}^{})}{W - {.Math.}_{h = 1}^{M} .Math. .Math. V_{h}^{}}$ wherein W is the calculated weight of the structure, (X, Y) is the calculated position of the centre of gravity of the structure, wherein M is the number of lifting surfaces considered at step c), wherein V.sub.h is the vertical component of a resultant force applied on a lifting surface h of the structure, wherein X.sup.h and Y.sub.h are the X-coordinate and Y-coordinate, respectively, through which the vertical component of the resultant force (V.sub.h) passes, wherein V.sub.h, X.sub.h and Y.sub.h are determined based on the measured responses (), for each lifting surface (h) as: $V^{} = C_{v}^{} + {.Math.}_{j_{v} = 1}^{L_{v}} .Math. .Math._{j_{v}}^{} .Math._{j_{v}}^{}$ $X^{} = C_{x}^{} + {.Math.}_{j_{x} = 1}^{L_{x}} .Math. .Math._{j_{x}}^{} .Math._{j_{x}}^{}$ $Y^{} = C_{y}^{} + {.Math.}_{j_{y} = 1}^{L_{y}} .Math. .Math._{j_{y}}^{} .Math._{j_{y}}^{}$ wherein are the responses measured by the second plurality of installed sensors, the subscript in the response () denoting the sensor which has performed the measurement, being L.sub.v, L.sub.x and L.sub.y natural numbers, wherein W, V and W.sub.corrected are expressed in the same axes system; X, X and X.sub.corrected are expressed according to the same coordinate system, and Y, Y and Y.sub.corrected are expressed according to the same coordinate system, and wherein: for determining V a fourth group of sensors is used which comprises a number of installed sensors L.sub.v, for determining X a fifth group of sensors is used which comprises a number of installed sensors L.sub.x, for determining Y a sixth group of sensors is used which comprises a number of installed sensors L.sub.y, and wherein coefficients .sub.j.sub.v, with j.sub.v=1, . . . L.sub.v, .sub.j.sub.x, with j.sub.x=1, . . . L.sub.x, and .sub.j.sub.y, with j.sub.y=1, . . . L.sub.y, and constants C.sub.v, C.sub.x, C.sub.y are previously determined applying the following calibration steps: s-i) locating a plurality of calibration sensors in at least one lifting surface (h) of the structure, wherein the number of calibration sensors is m, m being a natural number, s-ii) applying a probe force to the at least one lifting surface (h) of the structure, obtaining a force state (f), and measuring the vertical component of the resultant force (V.sub.f), the X-coordinate (X.sub.f) and the Y-coordinate (Y.sub.f) respectively through which the vertical component of the resultant force (V.sub.f) passes in said force state (f), s-iii) measuring for each calibration sensor (r) the response (.sub.r,f) associated to the force state (f), with r=1, . . . m, being r a natural number, s-iv) repeating steps s-ii) and s-iii) for a plurality of force states (f), with f=1, . . . s, being s the number of force states, wherein for each force state (f) a different probe force is applied to the at least one lifting surface (h), s being a natural number, s-v) selecting groups of at least two calibration sensors and solving for each group an equation system with a number of equations (P) greater than N.sub.v+1, being N.sub.v the number of calibration sensors in the group, wherein the equation system is: $V_{1}^{} = C_{v}^{} + {.Math.}_{n = 1}^{N_{v}} .Math. .Math._{n, 1}^{} .Math._{n}^{}$ $.Math.$ $V_{P}^{} = C_{v}^{} + {.Math.}_{n = 1}^{N_{v}} .Math. .Math._{n, P}^{} .Math._{n}^{}$ with .sub.n,q, with n=1, . . . , N.sub.v, being the measured responses of the calibration sensors and V.sub.q being the vertical component of the resultant force measured for the respective force state q, with q=1, . . . , P, wherein the equation systems are solved by least squares method, obtaining as a result vertical force coefficients .sub.n for n=1, . . . , N.sub.v and constant C.sub.v, s-vi) determining, for each group of calibration sensors an estimated vertical force (Ve.sub.f) for each force state (f) as ${Ve}_{f}^{} = C_{v}^{} + {.Math.}_{n = 1}^{N_{v}} .Math. .Math._{n, f}^{} .Math._{n}^{}$ where .sub.n,f are the responses of the calibration sensors of the group, associated to a force state f, s-vii) selecting a fourth group of calibration sensors which fulfils that fourth probable error (PE.sub.v) is minimum, wherein PE.sub.v is: ${PE}_{v}^{} = C_{E} .Math. \sqrt{\frac{{.Math.}_{f = 1}^{s .Math. .Math.} .Math. .Math. {({Ve}_{f}^{} - V_{f}^{})}^{2}}{s^{} - (N_{v} + 1)}}$ s being the total number of force states, N.sub.v being the number of calibration sensors in said group of calibration sensors, and C.sub.E being a real positive number, s-viii) selecting groups of at least two calibration sensors and solving for each group an equation system with a number of equations (P) equal to or greater than N.sub.x+1, being N.sub.x the number of calibration sensors in the group, wherein the equation systems is: $X_{1}^{} = C_{x}^{} + {.Math.}_{n = 1}^{N_{x}} .Math. .Math._{n, 1}^{} .Math._{n}^{}$ $.Math.$ $X_{P}^{} = C_{x}^{} + {.Math.}_{n = 1}^{N_{x}} .Math. .Math._{n, P}^{} .Math._{n}^{}$ .sub.n,q, with n=1, . . . , N.sub.x, being the measured responses of the calibration sensors and X.sub.q being the X-coordinate through which the measured vertical component of the resultant force (V.sub.q) passes, associated to the respective force state q, q=1, . . . , P wherein the equation systems are solved by least squares method, obtaining as a result X-coefficients .sub.n for n=1, . . . , N.sub.x and X-constant C.sub.x, s-ix) determining for each group of calibration sensors an estimated X-coordinate (Xe.sub.f) through which the vertical component of the resultant force (V.sub.f) passes for each force state (f), as ${Xe}_{f}^{} = C_{x}^{} + {.Math.}_{n = 1}^{N_{x}} .Math. .Math._{n, f}^{} .Math._{n}^{}$ where .sub.n,f are the responses of the calibration sensors of the selected group associated to a force state (f), s-x) selecting a fifth group of calibration sensors which fulfils that a fifth probable error (PE.sub.X) is minimum, wherein PE.sub.X is: ${PE}_{X}^{} = C_{E} .Math. \sqrt{\frac{{.Math.}_{f = 1}^{s .Math. .Math.} .Math. .Math. {({Xe}_{f}^{} - X_{f}^{})}^{2}}{s^{} - (N_{x} + 1)}}$ s being the total number of force states, N.sub.x being the number of calibration sensors in said group of calibration sensors, and C.sub.E being a real positive number, s-xi) selecting groups of at least two calibration sensors and solving for each group an equation system with a number of equations P equal or greater than N.sub.y+1, being N.sub.y the number of calibration sensors in the group, wherein the equation systems is: $Y_{1}^{} = C_{y}^{} + {.Math.}_{n = 1}^{N_{y}} .Math. .Math._{n, 1}^{} .Math._{n}^{}$ $.Math.$ $Y_{P}^{} = C_{y}^{} + {.Math.}_{n = 1}^{N_{y}} .Math. .Math._{n, P}^{} .Math._{n}^{}$ .sub.n,q, with n=1, . . . , N.sub.y, being the measured responses of the calibration sensors and Y.sub.q being the Y-coordinate through which the measured vertical component of the resultant force (V.sub.q) passes associated to the respective force state (q), q=1, . . . , P wherein the equation systems are solved by least squares method, obtaining as a result Y-coefficients .sub.n for n=1, . . . , N.sub.y and Y-constant C.sub.y, s-xii) determining for each group of calibration sensors an estimated Y-coordinate (Ye.sub.f) through which the vertical component of the resultant force (V.sub.f) passes for each force state (f), as ${Ye}_{f}^{} = C_{y}^{} + {.Math.}_{n = 1}^{N_{y}} .Math. .Math._{n, f}^{} .Math._{n}^{}$ where .sub.n,f are the responses of the calibration sensors of the selected group associated to a force state f, s-xiii) selecting a sixth group of calibration sensors which fulfils that a sixth probable error (PE.sub.Y) is minimum, wherein PE.sub.Y is: ${PE}_{Y}^{} = C_{E} .Math. \sqrt{\frac{{.Math.}_{f = 1}^{s .Math. .Math.} .Math. .Math. {({Ye}_{f}^{} - Y_{f}^{})}^{2}}{s^{} - (N_{y} + 1)}}$ s being the total number of force states, N.sub.y being the number of calibration sensors in said group of calibration sensors, and C.sub.E being a real positive number, s-xiv) selecting as the second plurality of installed sensors a plurality of calibration sensors including: the fourth group of calibration sensors selected in step s-vii), the fifth group of calibration sensors selected in step s-x), and the sixth group of calibration sensors selected in step s-xiii), wherein L.sub.v is the number of sensors in the fourth group of calibration sensors, L.sub.x is the number of sensors in the fifth group of calibration sensors and L.sub.y is the number of sensors in the sixth group of calibration sensors.

4. The method according to claim 1, comprising, after steps vii), x) and/or x), verifying for at least one loading state i that the first group of calibration sensors fulfills that a weight residual value (w.sub.i) is lower than a first predefined threshold, wherein $.Math. .Math. .Math. w_{i} = 100 .Math. \frac{({We}_{i} - W_{i})}{W_{i}},$ and/or the second group of calibration sensors fulfills that a X-coordinate residual value (x.sub.i) is lower than a second predefined threshold, wherein $.Math. .Math. .Math. x_{i} = 100 .Math. \frac{({Xe}_{i} - X_{i})}{X_{i}},$ and/or the third group of calibration sensors fulfills that a Y-coordinate residual value (y.sub.i) is lower than a third predefined threshold, wherein $.Math. .Math. .Math. y_{i} = 100 .Math. \frac{({Ye}_{i} - Y_{i})}{Y_{i}} .$

5. The method according to claim 1, wherein at each iteration of step ii) the structure is loaded with the probe weights Wp.sub.i in steps of a predetermined percentage of a maximum admissible weight of the structure.

6. The method according to claim 1, wherein the structure is an on ground vehicle.

7. The method according to claim 6, wherein at least one sensitive load point is located in at least one bulkhead of the vehicle.

8. The method according to claim 6, wherein the on ground vehicle is an aircraft.

9. The method according to claim 8, wherein at least one sensitive load point is located in at least one landing gear bulkhead.

10. The method according to claim 8, wherein at least one sensitive load point is located in the nose landing gear pin.

11. The method according to claim 8, wherein at least one sensitive load point is located in the main landing gear pin.

12. The method according to claim 1, wherein the first coordinate (X.sub.i) of the position of the centre of gravity and/or the weight (W.sub.i) is measured in calibration step ii) using scales and/or jacks with load cells, preferably, using three hydraulic jacks.

13. The method according to claim 1, wherein at step vii) a plurality of first groups of calibration sensors are selected, which fulfil that the first probable error is minimum, and/or wherein at step x) a plurality of second groups of calibration sensors are selected, which fulfil that the second probable error is minimum, and/or wherein at step x) a plurality of third groups of calibration sensors are selected, which fulfil that the third probable error is minimum.

14. A system configured for determining the weight (W) and/or at least a first coordinate of the position of the centre of gravity of a structure, comprising: a plurality of installed sensors located on the structure, a data acquisition module configured to register data from the plurality of installed sensors located on the structure, and a data processor configured to: determine the weight (W) and/or the first coordinate (X) of the position of the centre of gravity of the structure based on the measured responses (), as: $W = C_{w} + {.Math.}_{j_{w} = 1}^{k_{w}} .Math. .Math._{j_{w}} .Math._{j_{w}}$ $X = C_{x} + {.Math.}_{j_{x} = 1}^{k_{x}} .Math. .Math._{j_{x}} .Math._{j_{x}}$ wherein W is the weight of the structure, X is the first coordinate of the position of the centre of gravity of the structure on a plane of projection, k.sub.w and k.sub.x are natural numbers and are the responses measured by the first plurality of installed sensors, wherein the subscript in the response () denotes the sensor which has performed the measurement, wherein for determining the weight (W) a first group of sensors is used which comprises a number of installed sensors k.sub.w, for determining the first coordinate (X) of the centre of gravity a second group of sensors is used which comprises a number of installed sensors k.sub.x, and wherein coefficients .sub.j.sub.w, with j.sub.w=1, . . . k.sub.w, and y.sub.j.sub.x, with j.sub.x=1, . . . k.sub.x, and constants C.sub.w and C.sub.x are previously determined applying the following calibration steps: i) locating a plurality of calibration sensors in sensitive load points of the structure, wherein the number of calibration sensors is m, m being a natural number, ii) loading the structure with a probe weight (Wp.sub.i), obtaining a loading state (i), and measuring the first coordinate (X.sub.i) of the position of the centre of gravity and the weight (W.sub.i) of the structure in said loading state (i), iii) measuring for each calibration sensor (r) the response (.sub.r,i) associated to the loading state (i), with r=1, . . . m, being r a natural number, iv) repeating steps ii) and iii) for a plurality of loading states (i), with i=1, . . . s, beings the number of loading states, s being a natural number, v) selecting groups of at least two calibration sensors and solving for each group an equation system with a number of equations (P) equal to or greater than N.sub.w+1, being N.sub.w the number of calibration sensors in the group, wherein the equation system is: $W_{1} = C_{w} + {.Math.}_{n = 1}^{N_{w}} .Math. .Math._{n, 1} .Math._{n}$ $.Math.$ $W_{P} = C_{w} + {.Math.}_{n = 1}^{N_{w}} .Math. .Math._{n, P} .Math._{n}$ .sub.n,q, with n=1, . . . , N.sub.w, being the measured responses of the calibration sensors and W.sub.q being the weight associated to the respective loading state q, q=1, . . . , P, wherein the equation systems are solved by least squares method, obtaining as a result weight coefficients (.sub.n) for n=1, . . . , N.sub.w, and weight constant (C.sub.w), vi) determining for each group of calibration sensors an estimated weight (We.sub.i) for each loading state (i) as ${We}_{i} = C_{w} + {.Math.}_{n = 1}^{N_{w}} .Math. .Math._{n, i} .Math._{n}$ wherein .sub.n,i are the responses of the calibration sensors of the group, associated to a loading state i, vii) selecting a first group of calibration sensors which fulfils that a first probable error (PE.sub.w) is minimum, wherein PE.sub.w is: ${PE}_{w} = C_{E} .Math. \sqrt{\frac{{.Math.}_{i = 1}^{s} .Math. .Math. {({We}_{i} - W_{i})}^{2}}{s - (N_{w} + 1)}}$ s being the total number of loading states, N.sub.w being the number of calibration sensors in said group of calibration sensors, and C.sub.E being a real positive number, viii) selecting groups of at least two calibration sensors and solving for each group an equation system with a number of equations (P) equal or greater than N.sub.x+1, being N.sub.x the number of calibration sensors in the group, wherein the equation systems is: $X_{1} = C_{x} + {.Math.}_{n = 1}^{N_{x}} .Math. .Math._{n, 1} .Math._{n}$ $.Math.$ $X_{P} = C_{x} + {.Math.}_{n = 1}^{N_{x}} .Math. .Math._{n, P} .Math._{n}$ .sub.n,q, with n=1, . . . , N.sub.x, being the measured responses of the calibration sensors and X.sub.q being the X-coordinate of the centre of gravity associated to the respective loading state q, q=1, . . . , P, wherein the equation systems are solved by least squares method, obtaining as a result X-coefficients (.sub.n) for n=1, . . . , N.sub.x, and X-constant (C.sub.x), ix) determining for each group of calibration sensors an estimated X-coordinate (Xe.sub.i) of the centre of gravity for each loading state (i), as ${Xe}_{i} = C_{x} + {.Math.}_{n = 1}^{N_{x}} .Math. .Math._{n, i} .Math._{n}$ wherein .sub.n,i are the responses of the calibration sensors of the group, associated to a loading state i, x) selecting a second group of calibration sensors which fulfils that a second probable error (PE.sub.X) is minimum, wherein PE.sub.X is: ${PE}_{X} = C_{E} .Math. \sqrt{\frac{{.Math.}_{i = 1}^{s} .Math. .Math. {({Xe}_{i} - X_{i})}^{2}}{s - (N_{x} + 1)}}$ s being the total number of loading states, N.sub.x being the number of calibration sensors in said group of calibration sensors, and C.sub.E being a real positive number, xi) selecting as the first plurality of installed sensors a plurality of calibration sensors including: the first group of calibration sensors selected in step vii), and the second group of calibration sensors selected in step x), wherein k.sub.w is the number of sensors in the first group of calibration sensors and k.sub.x is the number of sensors in the second group of calibration sensors.

15. A vehicle comprising the system according to claim 14.

Description

DESCRIPTION OF THE DRAWINGS

[0172] These and other characteristics and advantages of the invention will become clearly understood in view of the detailed description of the invention which becomes apparent from a preferred embodiment of the invention, given just as an example and not being limited thereto, with reference to the drawings.

[0173] FIG. 1 shows sensitive load points used in an embodiment of the present invention.

[0174] FIG. 2 shows sensitive load points used in an embodiment of the present invention.

[0175] FIGS. 3a-3b show the installation of a sensor in at least one sensitive load point according to an embodiment of the present invention.

[0176] FIG. 4 shows an aircraft loaded with weight probes according to an embodiment of the present invention.

[0177] FIGS. 5a and 5b show a method to obtain the weight and the center of gravity by mean of jacks with load cells according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0178] Once the object of the invention has been outlined, specific non-limitative embodiments are described hereinafter. In particular, it is described an embodiment of the method for determining the weight (W) and a first coordinate, which is the X-coordinate, of the position of the centre of gravity (X, Y) of an aircraft (6). In this particular embodiment, the position of the centre of gravity is defined in relation to a coordinate system, the origin of which is a predefined point. In this particular example, the origin is located in the X-axis in front of the nose of the aircraft (6) if seen from the side, in particular at a distance of 1587 mm from the nose. In this aircraft (6) the X-axis is selected as the projection on the horizontal plane of the longitudinal direction along the fuselage (roll axis).

[0179] FIGS. 1 and 2 respectively show a main landing gear bulkhead (1) and a nose landing gear (2) of an aircraft (6). Selected sensitive load points (3) in the main landing gear bulkhead (1) and in pins (7) of the nose landing gear (2) are indicated in these figures. In the context of the invention the sensitive load points (3) of the structure which weight and/or centre of gravity are to be determined are the points where the structure is seated on the ground. In this particular example four of the sensitive load points (3) are located in the main landing gear bulkhead (1) and three of the sensitive load points (3) are located in the pins (7) of the nose landing gear (2), as shown in FIGS. 1 and 2 respectively.

[0180] After selecting the sensitive load points (3), at least one sensor (4) is located in each sensitive load point (3). In this particular example, the sensors (4) are strain gauge bridges. In FIGS. 3a and 3b, some of the strain gauge bridges (4) installed on the structure are schematically shown.

[0181] The strain gauge bridges (4) are attached to the structure by abrasion, adhesive application, application of pressure, and thermal curing. In the example shown in FIG. 3a, the strain gauge bridges (4) are attached to the main landing gear bulkhead (1). In FIG. 3b, the strain gauge bridges (4) are attached to the nose landing gear pin (7). In this particular example of FIG. 3b, the sensor (4) is embedded in one of the pins (7) of the nose landing gear pins.

Example

[0182] For a particular example, prior to determining the weight (W) and the X-coordinate (X) of the position of the centre of gravity (X, Y) of an aircraft (6), the following calibration steps were performed:

[0183] i) 19 calibration sensors were located in sensitive load points (3) of the aircraft (6). Thus, in this particular example m=19. In this particular example, all the calibration sensors located are strain gauges bridges. Further, the calibration sensors 1 to 16 are located in the main landing gear bulkhead, and the calibration sensors 17 to 19 are located in the nose landing gear pin (7).

[0184] ii) The structure was loaded with a probe weight Wp.sub.1, obtaining a first loading state (i=1), and the X-coordinate of the centre of gravity (X.sub.1) and the weight (W.sub.1) of the aircraft were measured for the loading state i=1. In this particular example, the Y-coordinate of the centre of gravity is not exemplified below, since it is obtained as for the X-coordinate.

[0185] iii) For each calibration sensor r the response .sub.r,1 associated to the loading state i=1 was measured, with r=1, . . . 19.

[0186] iv) Steps ii) and iii) were repeated for a plurality of loading states i. In this example, nine different configurations of loaded probe weights were used, different loading states being obtained by modifying the weight and/or the location of the probe weight loaded on the aircraft (6). As schematically shown in FIG. 4, twelve water tanks (8) were arranged at specific positions in the aircraft (6). In this example the loading states were obtained by filling up different combinations of tanks at different water levels. Tables 1A-1B show the filled water tanks and the maximum probe weight in each configuration. In Tables 1A-1B and in FIG. 4 the twelve tanks (8) are identified as T1, T2, . . . T12.

TABLE-US-00001 TABLE 1A Probe weight (kg) T1 T2 T3 T4 T5 T6 T7 configuration 1 1000 1000 configuration 2 configuration 3 1000 1000 configuration 4 1000 1000 configuration 5 1000 1000 1000 configuration 6 1000 configuration 7 1000 configuration 8 1000 configuration 9 1000 1000 1000 1000 1000

TABLE-US-00002 TABLE 1B Probe weight (kg) T8 T9 T10 T11 T12 Total Kg configuration 1 2000 configuration 2 1000 1000 2000 configuration 3 2000 configuration 4 1000 1000 4000 configuration 5 1000 4000 configuration 6 1000 1000 1000 4000 configuration 7 1000 1000 1000 4000 configuration 8 1000 2000 configuration 9 1000 1000 1000 1000 1000 10000

[0187] Additionally, for each of the configurations of filled water tanks (8) of Tables 1A-1B, several percentages of filling were considered. For example, for configuration 1 as indicated in Tables 1A-1B increasing percentages of tanks filling of 33%, 66%, 100% and decreasing percentages of tanks filling of 66%, 33% and 0% where considered. As a result, six loading states were obtained for configuration 1 of tanks (8) indicated in Table 1.

[0188] In these calibration steps, the weight (W.sub.i) and the X-coordinate (X.sub.i) of the position of the centre of gravity of the aircraft (6) in each loading state i have been measured with jacks with load cells as it is schematically shown in FIGS. 5a and 5b, wherein the load cell (10) is attached to the hydraulic jack (9) in a jacking point (11) in order to measure the real weight value (W.sub.i) and real X-coordinate (X.sub.i) of the centre of gravity of the aircraft (6) in each loading state i. The load cell (10) is connected to a weight indicator system (5) which registers the measures.

[0189] The following tables 2A-2E to 10A-10E show the weight (W.sub.i), the X-coordinate (X.sub.i) of the centre of gravity and the response of each sensor (the sensors are identified as bridges) measured for each loading state i:

TABLE-US-00003 TABLE 2A CONFIGURATION 1: six loading states Percent- Bridge Bridge Bridge Bridge age of Weight X_CG 01 02 03 04 cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 33% 111022.080 11117.346 0.590 0.022 1.503 0.250 66% 117004.640 10835.995 0.597 0.024 1.518 0.247 100% 122297.760 10614.656 0.604 0.027 1.542 0.241 66% 115403.360 10948.294 0.607 0.028 1.549 0.243 33% 110888.640 11164.416 0.603 0.031 1.570 0.224 0% 103527.200 11424.708 0.586 0.032 1.537 0.219

TABLE-US-00004 TABLE 2B CONFIGURATION 1: six loading states Percent- Bridge Bridge Bridge Bridge age of Weight X_CG 05 06 07 08 cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 33% 111022.080 11117.346 0.033 0.247 0.377 0.397 66% 117004.640 10835.995 0.038 0.253 0.391 0.407 100% 122297.760 10614.656 0.035 0.259 0.395 0.414 66% 115403.360 10948.294 0.028 0.253 0.380 0.402 33% 110888.640 11164.416 0.022 0.263 0.328 0.427 0% 103527.200 11424.708 0.013 0.249 0.311 0.398

TABLE-US-00005 TABLE 2C CONFIGURATION 1: six loading states Percent- Bridge Bridge Bridge Bridge age of Weight X_CG 09 10 11 12 cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 33% 111022.080 11117.346 0.607 0.005 1.433 0.087 66% 117004.640 10835.995 0.614 0.005 1.450 0.086 100% 122297.760 10614.656 0.626 0.012 1.489 0.064 66% 115403.360 10948.294 0.628 0.009 1.497 0.069 33% 110888.640 11164.416 0.611 0.007 1.443 0.086 0% 103527.200 11424.708 0.593 0.007 1.418 0.080

TABLE-US-00006 TABLE 2D CONFIGURATION 1: six loading states Percent- Bridge Bridge Bridge Bridge age of Weight X_CG 13 14 15 16 cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 33% 111022.080 11117.346 0.068 0.226 0.434 0.347 66% 117004.640 10835.995 0.071 0.231 0.441 0.356 100% 122297.760 10614.656 0.068 0.245 0.434 0.382 66% 115403.360 10948.294 0.057 0.238 0.416 0.371 33% 110888.640 11164.416 0.066 0.219 0.444 0.333 0% 103527.200 11424.708 0.061 0.209 0.432 0.316

TABLE-US-00007 TABLE 2E CONFIGURATION 1: six loading states Percentage Weight X_CG Bridge 17 Bridge 18 Bridge 19 of cargo (N) (mm) (mV/V) (mV/V) (mV/V) 33% 111022.080 11117.346 1.915 1.042 1.080 66% 117004.640 10835.995 2.335 1.294 1.289 100% 122297.760 10614.656 2.895 1.627 1.611 66% 115403.360 10948.294 2.317 1.334 1.372 33% 110888.640 11164.416 1.860 1.012 1.045 0% 103527.200 11424.708 1.460 0.798 0.882

TABLE-US-00008 TABLE 3A CONFIGURATION 2: six loading states Percent- Bridge Bridge Bridge Bridge age of Weight X_CG 01 02 03 04 cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 33% 108686.880 11509.888 0.618 0.025 1.561 0.250 66% 114157.920 11590.373 0.661 0.031 1.665 0.250 100% 120162.720 11673.937 0.727 0.040 1.826 0.242 66% 112734.560 11579.179 0.681 0.043 1.725 0.215 33% 108086.400 11509.259 0.613 0.014 1.508 0.282 0% 103349.280 11420.250 0.585 0.014 1.450 0.270

TABLE-US-00009 TABLE 3B CONFIGURATION 2: six loading states Percent- Bridge Bridge Bridge Bridge age of Weight X_CG 05 06 07 08 cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 33% 108686.880 11509.888 0.030 0.253 0.387 0.403 66% 114157.920 11590.373 0.037 0.278 0.421 0.443 100% 120162.720 11673.937 0.043 0.321 0.454 0.503 66% 112734.560 11579.179 0.029 0.309 0.418 0.471 33% 108086.400 11509.259 0.047 0.244 0.460 0.369 0% 103349.280 11420.250 0.038 0.232 0.437 0.341

TABLE-US-00010 TABLE 3C CONFIGURATION 2: six loading states Per- Bridge Bridge Bridge Bridge centage Weight X_CG 09 10 11 12 of cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 33% 108686.880 11509.888 0.641 0.011 1.530 0.067 66% 114157.920 11590.373 0.683 0.016 1.625 0.056 100% 120162.720 11673.937 0.728 0.017 1.687 0.059 66% 112734.560 11579.179 0.680 0.018 1.592 0.037 33% 108086.400 11509.259 0.647 0.014 1.551 0.048 0% 103349.280 11420.250 0.613 0.015 1.489 0.037

TABLE-US-00011 TABLE 3D CONFIGURATION 2: six loading states Per- Bridge Bridge Bridge Bridge centage Weight X_CG 13 14 15 16 of cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 33% 108686.880 11509.888 0.060 0.240 0.404 0.384 66% 114157.920 11590.373 0.069 0.262 0.435 0.416 100% 120162.720 11673.937 0.098 0.279 0.575 0.386 66% 112734.560 11579.179 0.083 0.267 0.540 0.367 33% 108086.400 11509.259 0.065 0.258 0.373 0.414 0% 103349.280 11420.250 0.056 0.247 0.353 0.393

TABLE-US-00012 TABLE 3E CONFIGURATION 2: six loading states Percentage Weight X_CG Bridge 17 Bridge 18 Bridge 19 of cargo (N) (mm) (mV/V) (mV/V) (mV/V) 33% 108686.880 11509.888 1.334 0.735 0.784 66% 114157.920 11590.373 1.336 0.743 0.788 100% 120162.720 11673.937 1.296 0.746 0.799 66% 112734.560 11579.179 1.308 0.744 0.802 33% 108086.400 11509.259 1.374 0.771 0.822 0% 103349.280 11420.250 1.404 0.786 0.836

TABLE-US-00013 TABLE 4A CONFIGURATION 3: six loading states Per- Bridge Bridge Bridge Bridge centage Weight X_CG 01 02 03 04 of cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 33% 109198.400 11162.881 0.560 0.014 1.417 0.270 66% 115136.480 10924.562 0.553 0.018 1.404 0.261 100% 120385.120 10738.966 0.548 0.017 1.388 0.263 66% 115069.760 10940.000 0.558 0.017 1.414 0.266 33% 109554.240 11157.164 0.563 0.015 1.431 0.265 0% 104149.920 11395.553 0.568 0.016 1.446 0.264

TABLE-US-00014 TABLE 4B CONFIGURATION 3: six loading states Per- Bridge Bridge Bridge Bridge centage Weight X_CG 05 06 07 08 of cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 33% 109198.400 11162.881 0.044 0.208 0.449 0.320 66% 115136.480 10924.562 0.048 0.214 0.460 0.334 100% 120385.120 10738.966 0.053 0.194 0.481 0.296 66% 115069.760 10940.000 0.049 0.190 0.484 0.289 33% 109554.240 11157.164 0.034 0.220 0.398 0.352 0% 104149.920 11395.553 0.033 0.215 0.400 0.343

TABLE-US-00015 TABLE 4C CONFIGURATION 3: six loading states Per- Bridge Bridge Bridge Bridge centage Weight X_CG 09 10 11 12 of cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 33% 109198.400 11162.881 0.634 0.015 1.549 0.050 66% 115136.480 10924.562 0.663 0.018 1.612 0.041 100% 120385.120 10738.966 0.690 0.021 1.657 0.037 66% 115069.760 10940.000 0.670 0.020 1.628 0.039 33% 109554.240 11157.164 0.632 0.014 1.525 0.056 0% 104149.920 11395.553 0.614 0.010 1.495 0.066

TABLE-US-00016 TABLE 4D CONFIGURATION 3: six loading states Per- Bridge Bridge Bridge Bridge centage Weight X_CG 13 14 15 16 of cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 33% 109198.400 11162.881 0.058 0.249 0.370 0.412 66% 115136.480 10924.562 0.067 0.270 0.399 0.444 100% 120385.120 10738.966 0.078 0.285 0.472 0.442 66% 115069.760 10940.000 0.067 0.276 0.443 0.425 33% 109554.240 11157.164 0.056 0.252 0.369 0.418 0% 104149.920 11395.553 0.040 0.236 0.330 0.395

TABLE-US-00017 TABLE 4E CONFIGURATION 3: six loading states Percentage Weight X_CG Bridge 17 Bridge 18 Bridge 19 of cargo (N) (mm) (mV/V) (mV/V) (mV/V) 33% 109198.400 11162.881 1.804 1.004 1.019 66% 115136.480 10924.562 2.243 1.261 1.239 100% 120385.120 10738.966 2.656 1.517 1.461 66% 115069.760 10940.000 2.305 1.352 1.331 33% 109554.240 11157.164 1.856 1.040 1.044 0% 104149.920 11395.553 1.494 0.855 0.906

TABLE-US-00018 TABLE 5A CONFIGURATION 4: five loading states Per- Bridge Bridge Bridge Bridge centage Weight X_CG 01 02 03 04 of cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 33% 115381.120 11364.245 0.662 0.030 1.679 0.250 66% 127168.320 11344.276 0.745 0.042 1.871 0.248 100% 138221.600 11320.850 0.828 0.052 2.046 0.250 50% 121719.520 11381.470 0.735 0.049 1.835 0.222 0% 103972.000 11414.744 0.587 0.029 1.540 0.229

TABLE-US-00019 TABLE 5B CONFIGURATION 4: five loading states Per- Bridge Bridge Bridge Bridge centage Weight X_CG 05 06 07 08 of cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 33% 115381.120 11364.245 0.034 0.293 0.398 0.465 66% 127168.320 11344.276 0.051 0.350 0.479 0.550 100% 138221.600 11320.850 0.074 0.403 0.577 0.629 50% 121719.520 11381.470 0.035 0.355 0.495 0.538 0% 103972.000 11414.744 0.029 0.235 0.348 0.379

TABLE-US-00020 TABLE 5C CONFIGURATION 4: five loading states Per- Bridge Bridge Bridge Bridge centage Weight X_CG 09 10 11 12 of cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 33% 115381.120 11364.245 0.650 0.010 1.527 0.079 66% 127168.320 11344.276 0.703 0.016 1.648 0.064 100% 138221.600 11320.850 0.759 0.030 1.794 0.014 50% 121719.520 11381.470 0.694 0.032 1.672 0.004 0% 103972.000 11414.744 0.596 0.005 1.418 0.096

TABLE-US-00021 TABLE 5D CONFIGURATION 4: five loading states Per- Bridge Bridge Bridge Bridge centage Weight X_CG 13 14 15 16 of cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 33% 115381.120 11364.245 0.069 0.244 0.445 0.374 66% 127168.320 11344.276 0.079 0.275 0.485 0.420 100% 138221.600 11320.850 0.077 0.316 0.478 0.495 50% 121719.520 11381.470 0.060 0.294 0.444 0.454 0% 103972.000 11414.744 0.069 0.198 0.471 0.285

TABLE-US-00022 TABLE 5E CONFIGURATION 4: five loading states Percentage Weight X_CG Bridge 17 Bridge 18 Bridge 19 of cargo (N) (mm) (mV/V) (mV/V) (mV/V) 33% 115381.120 11364.245 1.692 1.010 1.010 66% 127168.320 11344.276 1.885 1.107 1.087 100% 138221.600 11320.850 2.017 1.161 1.153 50% 121719.520 11381.470 1.692 0.998 1.030 0% 103972.000 11414.744 1.417 0.823 0.820

TABLE-US-00023 TABLE 6A CONFIGURATION 5: six loading states Per- Bridge Bridge Bridge Bridge centage Weight X_CG 01 02 03 04 of cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 0% 103972.000 11414.744 0.588 0.029 1.542 0.228 33% 115603.520 11301.925 0.649 0.037 1.683 0.233 66% 126567.840 11224.119 0.702 0.040 1.773 0.243 100% 135508.320 11150.887 0.754 0.049 1.892 0.237 50% 119717.920 11267.787 0.674 0.038 1.723 0.239 0% 102370.720 11424.841 0.601 0.035 1.551 0.210

TABLE-US-00024 TABLE 6B CONFIGURATION 5: six loading states Per- Bridge Bridge Bridge Bridge centage Weight X_CG 05 06 07 08 of cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 0% 103972.000 11414.744 0.029 0.234 0.350 0.379 33% 115603.520 11301.925 0.035 0.274 0.399 0.440 66% 126567.840 11224.119 0.036 0.315 0.429 0.503 100% 135508.320 11150.887 0.048 0.353 0.484 0.562 50% 119717.920 11267.787 0.037 0.299 0.412 0.476 0% 102370.720 11424.841 0.010 0.258 0.344 0.408

TABLE-US-00025 TABLE 6C CONFIGURATION 5: six loading states Per- Bridge Bridge Bridge Bridge centage Weight X_CG 09 10 11 12 of cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 0% 103972.000 11414.744 0.597 0.005 1.420 0.095 33% 115603.520 11301.925 0.659 0.012 1.557 0.081 66% 126567.840 11224.119 0.721 0.022 1.685 0.046 100% 135508.320 11150.887 0.766 0.029 1.782 0.028 50% 119717.920 11267.787 0.686 0.020 1.620 0.053 0% 102370.720 11424.841 0.600 0.018 1.445 0.035

TABLE-US-00026 TABLE 6D CONFIGURATION 5: six loading states Per- Bridge Bridge Bridge Bridge centage Weight X_CG 13 14 15 16 of cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 0% 103972.000 11414.744 0.070 0.197 0.472 0.284 33% 115603.520 11301.925 0.078 0.234 0.516 0.339 66% 126567.840 11224.119 0.080 0.295 0.509 0.445 100% 135508.320 11150.887 0.092 0.325 0.547 0.491 50% 119717.920 11267.787 0.076 0.264 0.480 0.400 0% 102370.720 11424.841 0.057 0.230 0.427 0.339

TABLE-US-00027 TABLE 6E CONFIGURATION 5: six loading states Percentage Weight X_CG Bridge 17 Bridge 18 Bridge 19 of cargo (N) (mm) (mV/V) (mV/V) (mV/V) 0% 103972.000 11414.744 1.422 0.760 0.822 33% 115603.520 11301.925 1.756 0.949 0.988 66% 126567.840 11224.119 2.012 1.111 1.131 100% 135508.320 11150.887 2.283 1.265 1.266 50% 119717.920 11267.787 1.901 1.069 1.129 0% 102370.720 11424.841 1.411 0.778 0.867

TABLE-US-00028 TABLE 7A CONFIGURATION 6: six loading states Per- Bridge Bridge Bridge Bridge centage Weight X_CG 01 02 03 04 of cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 0% 102370.720 11424.841 0.599 0.034 1.552 0.212 33% 114091.200 11544.014 0.705 0.044 1.827 0.223 66% 125878.400 11630.835 0.804 0.058 2.047 0.217 90% 135019.040 11692.424 0.900 0.070 2.245 0.223 50% 120184.960 11586.200 0.779 0.065 1.964 0.183 0% 102192.800 11423.009 0.570 0.022 1.480 0.245

TABLE-US-00029 TABLE 7B CONFIGURATION 6: six loading states Percent- Bridge Bridge Bridge Bridge age of Weight X_CG 05 06 07 08 cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 0% 102370.720 11424.841 0.009 0.257 0.344 0.408 33% 114091.200 11544.014 0.036 0.311 0.414 0.502 66% 125878.400 11630.835 0.058 0.383 0.518 0.611 90% 135019.040 11692.424 0.077 0.444 0.635 0.698 50% 120184.960 11586.200 0.034 0.384 0.524 0.579 0% 102192.800 11423.009 0.024 0.223 0.346 0.366

TABLE-US-00030 TABLE 7C CONFIGURATION 6: six loading states Percent- Bridge Bridge Bridge Bridge age of Weight X_CG 09 10 11 12 cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 0% 102370.720 11424.841 0.599 0.019 1.446 0.036 33% 114091.200 11544.014 0.632 0.004 1.463 0.109 66% 125878.400 11630.835 0.650 0.006 1.509 0.111 90% 135019.040 11692.424 0.732 0.027 1.709 0.043 50% 120184.960 11586.200 0.678 0.029 1.606 0.016 0% 102192.800 11423.009 0.585 0.003 1.373 0.100

TABLE-US-00031 TABLE 7D CONFIGURATION 6: six loading states Percent- Bridge Bridge Bridge Bridge age of Weight X_CG 13 14 15 16 cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 0% 102370.720 11424.841 0.056 0.228 0.427 0.339 33% 114091.200 11544.014 0.087 0.204 0.571 0.252 66% 125878.400 11630.835 0.086 0.214 0.577 0.270 90% 135019.040 11692.424 0.079 0.256 0.562 0.363 50% 120184.960 11586.200 0.065 0.244 0.532 0.337 0% 102192.800 11423.009 0.058 0.194 0.445 0.288

TABLE-US-00032 TABLE 7E CONFIGURATION 6: six loading states Percentage Weight X_CG Bridge 17 Bridge 18 Bridge 19 of cargo (N) (mm) (mV/V) (mV/V) (mV/V) 0% 102370.720 11424.841 1.410 0.796 0.870 33% 114091.200 11544.014 1.359 0.753 0.794 66% 125878.400 11630.835 1.481 0.821 0.859 100% 135019.040 11692.424 1.349 0.725 0.805 50% 120184.960 11586.200 1.350 0.743 0.816 0% 102192.800 11423.009 1.363 0.749 0.797

TABLE-US-00033 TABLE 8A CONFIGURATION 7: six loading states Percent- Bridge Bridge Bridge Bridge age of Weight X_CG 01 02 03 04 cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 0% 102192.800 11423.009 0.575 0.017 1.478 0.247 33% 113735.360 11509.838 0.652 0.026 1.655 0.255 66% 124988.800 11572.303 0.732 0.040 1.833 0.250 100% 136397.920 11632.690 0.810 0.052 2.008 0.246 50% 119740.160 11552.059 0.694 0.030 1.730 0.269 0% 102392.960 11412.718 0.594 0.024 1.498 0.234

TABLE-US-00034 TABLE 8B CONFIGURATION 7: six loading states Percent- Bridge Bridge Bridge Bridge age of Weight X_CG 05 06 07 08 cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 0% 102192.800 11423.009 0.030 0.227 0.347 0.365 33% 113735.360 11509.838 0.037 0.276 0.401 0.436 66% 124988.800 11572.303 0.046 0.322 0.468 0.503 100% 136397.920 11632.690 0.061 0.373 0.538 0.583 50% 119740.160 11552.059 0.052 0.282 0.501 0.441 0% 102392.960 11412.718 0.023 0.233 0.418 0.355

TABLE-US-00035 TABLE 8C CONFIGURATION 7: six loading states Percent- Bridge Bridge Bridge Bridge age of Weight X_CG 09 10 11 12 cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 0% 102192.800 11423.009 0.587 0.001 1.372 0.102 33% 113735.360 11509.838 0.663 0.006 1.546 0.090 66% 124988.800 11572.303 0.749 0.021 1.743 0.045 100% 136397.920 11632.690 0.826 0.032 1.905 0.017 50% 119740.160 11552.059 0.721 0.027 1.721 0.017 0% 102392.960 11412.718 0.607 0.022 1.492 0.010

TABLE-US-00036 TABLE 8D CONFIGURATION 7: six loading states Percent- Bridge Bridge Bridge Bridge age of Weight X_CG 13 14 15 16 cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 0% 102192.800 11423.009 0.068 0.201 0.447 0.287 33% 113735.360 11509.838 0.078 0.240 0.492 0.350 66% 124988.800 11572.303 0.085 0.291 0.536 0.428 100% 136397.920 11632.690 0.101 0.339 0.596 0.497 50% 119740.160 11552.059 0.072 0.282 0.457 0.442 0% 102392.960 11412.718 0.046 0.233 0.387 0.362

TABLE-US-00037 TABLE 8E CONFIGURATION 7: six loading states Percentage Weight X_CG Bridge 17 Bridge 18 Bridge 19 of cargo (N) (mm) (mV/V) (mV/V) (mV/V) 0% 102192.800 11423.009 1.367 0.729 0.793 33% 113735.360 11509.838 1.427 0.755 0.817 66% 124988.800 11572.303 1.436 0.762 0.831 100% 136397.920 11632.690 1.481 0.787 0.851 50% 119740.160 11552.059 1.422 0.741 0.824 0% 102392.960 11412.718 1.363 0.724 0.808

TABLE-US-00038 TABLE 9A CONFIGURATION 8: five loading states Percent- Bridge Bridge Bridge Bridge age of Weight X_CG 01 02 03 04 cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 0% 102392.960 11412.718 0.594 0.026 1.497 0.236 50% 111555.840 11324.863 0.589 0.019 1.489 0.262 100% 119540.000 11263.699 0.621 0.026 1.583 0.246 50% 111066.560 11341.331 0.609 0.028 1.568 0.237 0% 102170.560 11411.070 0.568 0.011 1.435 0.266

TABLE-US-00039 TABLE 9B CONFIGURATION 8: five loading states Percent- Bridge Bridge Bridge Bridge age of Weight X_CG 05 06 07 08 cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 0% 102392.960 11412.718 0.021 0.232 0.417 0.354 50% 111555.840 11324.863 0.034 0.230 0.393 0.362 100% 119540.000 11263.699 0.030 0.258 0.361 0.410 50% 111066.560 11341.331 0.023 0.251 0.352 0.388 0% 102170.560 11411.070 0.032 0.228 0.356 0.362

TABLE-US-00040 TABLE 9C CONFIGURATION 8: five loading states Percent- Bridge Bridge Bridge Bridge age of Weight X_CG 09 10 11 12 cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 0% 102392.960 11412.718 0.607 0.023 1.492 0.012 50% 111555.840 11324.863 0.668 0.011 1.577 0.071 100% 119540.000 11263.699 0.732 0.018 1.707 0.048 50% 111066.560 11341.331 0.673 0.020 1.587 0.033 0% 102170.560 11411.070 0.595 0.004 1.423 0.082

TABLE-US-00041 TABLE 9D CONFIGURATION 8: five loading states Percent- Bridge Bridge Bridge Bridge age of Weight X_CG 13 14 15 16 cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 0% 102392.960 11412.718 0.044 0.232 0.384 0.362 50% 111555.840 11324.863 0.066 0.259 0.432 0.407 100% 119540.000 11263.699 0.093 0.309 0.516 0.462 50% 111066.560 11341.331 0.072 0.290 0.466 0.430 0% 102170.560 11411.070 0.057 0.225 0.334 0.374

TABLE-US-00042 TABLE 9E CONFIGURATION 8: five loading states Percentage Weight X_CG Bridge 17 Bridge 18 Bridge 19 of cargo (N) (mm) (mV/V) (mV/V) (mV/V) 0% 102392.960 11412.718 1.376 0.724 0.819 50% 111555.840 11324.863 1.640 0.874 0.932 100% 119540.000 11263.699 1.863 1.017 1.043 50% 111066.560 11341.331 1.649 0.918 0.970 0% 102170.560 11411.070 1.389 0.729 0.818

TABLE-US-00043 TABLE 10A CONFIGURATION 9: five loading states Percent- Bridge Bridge Bridge Bridge age of Weight X_CG 01 02 03 04 cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 0% 102122.100 11412.858 0.562 0.016 1.443 0.259 50% 147150.000 11409.637 0.841 0.058 2.068 0.251 100% 185801.400 11399.015 1.075 0.103 2.583 0.189 50% 145580.400 11431.630 0.856 0.074 2.081 0.187 0% 102612.600 11400.263 0.602 0.036 1.505 0.222

TABLE-US-00044 TABLE 10B CONFIGURATION 9: five loading states Percent- Bridge Bridge Bridge Bridge age of Weight X_CG 05 06 07 08 cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 0% 102122.100 11412.858 0.028 0.228 0.361 0.366 50% 147150.000 11409.637 0.073 0.419 0.595 0.650 100% 185801.400 11399.015 0.138 0.605 0.840 0.923 50% 145580.400 11431.630 0.049 0.460 0.608 0.680 0% 102612.600 11400.263 0.006 0.253 0.369 0.383

TABLE-US-00045 TABLE 10C CONFIGURATION 9: five loading states Percent- Bridge Bridge Bridge Bridge age of Weight X_CG 09 10 11 12 cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 0% 102122.100 11412.858 0.593 0.009 1.430 0.072 50% 147150.000 11409.637 0.876 0.049 2.036 0.036 100% 185801.400 11399.015 1.111 0.094 2.515 0.170 50% 145580.400 11431.630 0.871 0.064 2.025 0.105 0% 102612.600 11400.263 0.606 0.026 1.486 0.015

TABLE-US-00046 TABLE 10D CONFIGURATION 9: five loading states Percent- Bridge Bridge Bridge Bridge age of Weight X_CG 13 14 15 16 cargo (N) (mm) (mV/V) (mV/V) (mV/V) (mV/V) 0% 102122.100 11412.858 0.049 0.223 0.338 0.377 50% 147150.000 11409.637 0.102 0.408 0.582 0.629 100% 185801.400 11399.015 0.167 0.580 0.840 0.852 50% 145580.400 11431.630 0.084 0.432 0.614 0.647 0% 102612.600 11400.263 0.033 0.241 0.378 0.404

TABLE-US-00047 TABLE 10E CONFIGURATION 9: five loading states Percentage Weight X_CG Bridge 17 Bridge 18 Bridge 19 of cargo (N) (mm) (mV/V) (mV/V) (mV/V) 0% 102122.100 11412.858 1.402 0.746 0.824 50% 147150.000 11409.637 1.993 1.088 1.117 100% 185801.400 11399.015 2.415 1.330 1.335 50% 145580.400 11431.630 1.979 1.109 1.168 0% 102612.600 11400.263 1.422 0.786 0.891

[0190] Considering all the filling percentages, a total of 51 loading states were obtained.

[0191] Once the measurements of each sensor (4) were obtained according to each loading state i, the following calibration steps were performed:

[0192] v) Groups of four calibration sensors (N.sub.w=4) were formed and for each group an equation system with a number of equations P=51 was solved by least squares. Also, groups of three calibration sensors (N.sub.w=3) were formed and for each group an equation system with a number of equations P=51 was also solved by least squares. In this example, all the combinations of 3 sensors and 4 sensors were considered. For each group of sensors the weight coefficients .sub.n for n=1, . . . , 4 and for n=1, . . . , 3 were obtained, respectively.

[0193] vi) The estimated weight (We.sub.i) for each loading state i and the first probable error (PE.sub.w) were determined for each group of 4 and 3 sensors (N.sub.w=4, N.sub.w=3) using the measured responses and the obtained weight coefficients.

[0194] Below are shown several (not all) equations obtained in steps v) and vi) for some of the groups of four sensors (N.sub.w=4) and the first probable error (PE.sub.w) obtained for said groups:

We.sup.Eq1=(86556.3.sup.bridge1)+(73945.4.sup.bridge2)+(63713.4.sup.bridge9)+(11350.0.sup.bridge17)Equation 1:

[0195] First probable error for Equation 1: PE.sub.w=736.0

We.sup.Eq2=(72791.4.sup.bridge1)+(75957.2.sup.bridge9)+(65926.8 65926.8.sup.bridge10)+(11083.7.sup.bridge17)Equation 2:

[0196] First probable error for Equation 2: PE.sub.w=684.3

We.sup.Eq3=(29698.7.sup.bridge3)+(75203.4.sup.bridge9)+(24293.0.sup.bridge17)+(25100.2.sup.bridge19)Equation 3:

[0197] First probable error for Equation 3: PE.sub.w=713.8

We.sup.Eq4=(28387.9.sup.bridge3)+(44809.5.sup.bridge5)+(72570.8.sup.bridge9)+(11039.6.sup.bridge17)Equation 4:

[0198] First probable error for Equation 4: PE.sub.w=704.4

We.sup.Eq5=(85744.5.sup.bridge1)+(81280.3.sup.bridge2)+(67149.1.sup.bridge9)+(18817.2.sup.bridge18)Equation 5:

[0199] First probable error for Equation 5: PE.sub.w=935.3

We.sup.Eq6=(80364.5.sup.bridge1)+(57544.1.sup.bridge2)+(67523.6.sup.bridge9)+(20592.7bridge 19)Equation 6:

[0200] First probable error for Equation 6: PE.sub.w=1036.4

We.sup.Eq7=(156095.0.sup.bridge1)+(335755.3.sup.bridge2)+(181157.1.sup.bridge10)+(23123.7.sup.bridge18)Equation 7:

[0201] First probable error for Equation 7: PE.sub.w=1749.8

[0202] wherein We.sup.Eq1 denotes an estimated weight obtained with a first combination of sensors, namely sensors 1, 2, 9 and 17, and wherein the first probable error (PE.sub.w) has been obtained for each group of sensors according to the following expression

[00026] ${PE}_{w} = C_{E} .Math. \sqrt{\frac{{.Math.}_{i = 1}^{s} .Math. .Math. {({We}_{i} - W_{i})}^{2}}{s - (N_{w} + 1)}}$

[0203] with s=51, N.sub.w=4, and C.sub.E=0.6745, i denoting the loading state. In this particular example, the obtained weight constant C.sub.w in the above equations is 0.

[0204] From the above results, equations 2 and 4 were selected due to their lower values for the first probable error. The sensors corresponding to said equations are sensors 1, 9, 10 and 17 for equation 2 and sensors 3, 5, 9 and 17 for equation 4.

[0205] Below are shown several (not all) equations obtained in the steps v) and vi) for some of the groups of three sensors (N.sub.w=3) and the first probable error (PE.sub.w) obtained for said groups:

We.sup.Eq1=(67486.3.sup.bridge1)+(141344.7.sup.bridge2)+(114424.1.sup.bridge9)Equation 1:

First probable error for Equation 1: PE.sub.w=2989.5

We.sup.Eq2=(67642.3.sup.bridge1)+(74448.0.sup.bridge2)+(46822.8.sup.bridge11)Equation 2:

First probable error for Equation 2: PE.sub.w=3142.9

We.sup.Eq3=(74227.1.sup.bridge1)+(71078.6.sup.bridge9)+(11693.7.sup.bridge17)Equation 3:

First probable error for Equation 3: PE.sub.w=899.9

We.sup.Eq4=(42357.3.sup.bridge1)+(132662.4.sup.bridge9)+(9092.1.sup.bridge13)Equation 4:

First probable error for Equation 4: PE.sub.w=3159.1

We.sup.Eq5=(125553.4.sup.bridge1)+(87136.1.sup.bridge7)+(253449.0.sup.bridge10)Equation 5:

[0206] First probable error for Equation 5: PE.sub.w=5497.9

We.sup.Eq6=(28267.7.sup.bridge3)+(75931.5.sup.bridge9)+(10896.8.sup.bridge17)Equation 6:

First probable error for Equation 6: PE.sub.w=856.5

[0207] wherein the first probable error (PE.sub.w) has been obtained for each group of sensors according to the following expression

[00027] ${PE}_{w} = C_{E} .Math. \sqrt{\frac{{.Math.}_{i = 1}^{s} .Math. .Math. {({We}_{i} - W_{i})}^{2}}{s - (N_{w} + 1)}}$

[0208] with s=51, N.sub.w=3, and C.sub.E=0.6745, i denoting the loading state.

[0209] From the above results, equations 3 and 6 were selected due to their lower values for the probable error. The sensors corresponding to said equations are sensors 1, 9 and 17 for equation 3 and sensors 3, 9 and 17 for equation 6.

[0210] vii) Four first groups of sensors were selected from the plurality of calibration sensors (4) according to the first probable errors (PE.sub.w) previously determined for each group of sensors (N.sub.w=4, N.sub.w=3). The sensors included in said four groups are sensors 1, 3, 5, 9, 10, and 17. Said six sensors (4) are thus selected as the installed sensors usable for determining the weight (W) of the aircraft (6). Once performed the calibration steps, the determination of the weight (W) of the aircraft (6) can be performed based on the responses of the sensors according to one or several of the following expressions:

We.sup.App1=(72791.4.sup.bridge1)+(75957.2.sup.bridge9)+(65926.8.sup.bridge10)+(11083.7.sup.bridge17)Approach 1:

We.sup.App2=(28387.9.sup.bridge3)+(44809.5.sup.bridge5)+(72570.8.sup.bridge9)+(11039.6.sup.bridge17)Approach 2:

We.sup.App3=(74227.1.sup.bridge1)+(71078.sup.bridge9)+(11693.7.sup.bridge17)Approach 3:

We.sup.App4=(28267.7.sup.bridge3)+(75931.5.sup.bridge9)+(10896.8.sup.bridge17)Approach 4:

[0211] In a preferred embodiment at least two groups of sensors having different number of sensors are selected.

[0212] The following calibration steps were performed to obtain the X-coordinate of the centre of gravity:

[0213] viii) Groups of four calibration sensors (N.sub.x=4) were formed and for each group an equation system with a number of equations P=51 was solved by least squares. Also, groups of three calibration sensors (N.sub.x=3) were formed and for each group an equation system with a number of equation P=51 was also solved by least squares. For each group of sensors, the X-coordinate coefficients .sub.n for n=1, . . . , 4, and for n=1, . . . , 3, and the constant C.sub.x were obtained, respectively.

[0214] ix) The estimated X-coordinate (Xe.sub.i) for each loading state i and the second probable error (PE.sub.x) were determined for each group of 4 and 3 sensors (N.sub.x=4, N.sub.x=3) using the measured responses, the obtained X-coordinate coefficients and the obtained X-constant C.sub.x.

[0215] Below are shown several (not all) equations obtained in steps viii) and ix) for some of the groups of four sensors (N.sub.x=4) and the second probable error (PE.sub.x) obtained for said groups:

Xe.sup.Eq1=(2501.7.sup.bridge5)+(299.5.sup.bridge7)+(2695.3.sup.bridge10)+(1031.6.sup.bridge19)+12040.8Equation 1:

[0216] Second probable error for Equation 1: PE.sub.x=48.0

Xe.sup.Eq2=(498.6.sup.bridge5)+(569.2.sup.bridge8)+(654.5.sup.bridge9)+(979.6.sup.bridge19)+11555.4Equation 2:

[0217] Second probable error for Equation 2: PE.sub.x=31.3

Xe.sup.Eq3=(2330.6.sup.bridge13)+(580.9.sup.bridge15)+(953.6.sup.bridge17)+(616.9.sup.bridge19)+11934.0Equation 3:

[0218] Second probable error for Equation 3: PE.sub.x=38.4

Xe.sup.Eq4=(17814.8.sup.bridge1)+(4114.3.sup.bridge7)+(12056.8.sup.bridge8)+(1118.8.sup.bridge11)+8539.4Equation 4:

[0219] Second/probable error for Equation 4: PE.sub.x=98.4

Xe.sup.Eq5=(302.2.sup.bridge3)+(2523.8.sup.bridge10)+(393.1.sup.bridge11)+(570.3.sup.bridge17)+11223.3Equation 5:

[0220] Second probable error for Equation 5: PE.sub.x=16.6

Xe.sup.Eq6=(272.6.sup.bridge3)+(807.4.sup.bridge9)+(1508.3.sup.bridge10)+(571.7.sup.bridge17)+11341.5Equation 6:

[0221] Second probable error for Equation 6: PE.sub.x=16.7

[0222] wherein Xe.sup.Eq1 denotes an estimated X-coordinate obtained with a first combination of sensors, namely sensors 5, 7, 10 and 19, and wherein the second probable error (PE.sub.X) has been obtained for each group of sensors according to the following expression

[00028] ${PE}_{X} = C_{E} .Math. \sqrt{\frac{{.Math.}_{i = 1}^{s} .Math. .Math. {({Xe}_{i} - X_{i})}^{2}}{s - (N_{x} + 1)}}$

[0223] with s=51, N.sub.w=4 and C.sub.E=0.6745, i denoting the loading state.

[0224] From the above results, the equations 5 and 6 were selected due to their lower values for the probable error. The sensors (4) corresponding to said equations are sensors 3, 10, 11 and 17 for equation 5 and sensors 3, 9, 10 and 17 for equation 4.

[0225] Below are shown several (not all) equations obtained in the steps viii) and ix) for some of the groups of three sensors (N.sub.x=3) and the second probable error PE.sub.X obtained for said groups:

Xe.sup.Eq1=(274.9.sup.bridge3)+(632.6.sup.bridge9)+(570.8.sup.bridge17)+11428.6Equation 1:

[0226] Second probable error for Equation 1: PE.sub.x=17.6

Xe.sup.Eq2=(6343.1.sup.bridge1)+(21746.6.sup.bridge2)+(15172.6.sup.bridge5)+8477.4Equation 2:

[0227] Second probable error for Equation 2: PE.sub.x=128.1

Xe.sup.Eq3=(924.9.sup.bridge3)+(6513.9.sup.bridge5)+(80.9.sup.bridge11)+10182.0Equation 3:

[0228] Second probable error for Equation 3: PE.sub.x=145.2

Xe.sup.Eq4=(688.2.sup.bridge1)+(559.8.sup.bridge9)+(570.2.sup.bridge17)+11481.6Equation 4:

[0229] Second probable error for Equation 4: PE.sub.x=18.2

Xe.sup.Eq5=(667.9.sup.bridge8)+(2024.6.sup.bridge13)+(575.1.sup.bridge17)+11872.0Equation 5:

[0230] Second probable error for Equation 5: PE.sub.x=25.1

Xe.sup.Eq6=(801.3.sup.bridge5)+(834.1.sup.bridge7)+(1015.7.sup.bridge19)+11903.2Equation 6:

[0231] Second probable error for Equation 6: PE.sub.x=48.3

[0232] wherein the second probable error PE.sub.X has been obtained for each group of sensors according to the following expression

[00029] ${PE}_{X} = C_{E} .Math. \sqrt{\frac{{.Math.}_{i = 1}^{s} .Math. .Math. {({Xe}_{i} - X_{i})}^{2}}{s - (N_{x} + 1)}}$

[0233] with s=51, N.sub.w=3 and C.sub.E=0.6745, i denoting the loading state.

[0234] From the above results, the equations 1 and 4 were selected due to their lower values for the second probable error. The sensors (4) corresponding to said equations are sensors 3, 9 and 17 for equation 1 and sensors 1, 9 and 17 for equation 4.

[0235] x) Four second groups of sensors were selected from the plurality of calibration sensors (4) according to the second probable errors (PE.sub.X) previously determined for each group of sensors (N.sub.w=4, N.sub.w=3). The sensors included in said four second groups are sensors 1, 3, 9, 10, 11 and 17. Said six sensors (4) are thus selected as the installed sensors usable for determining the X-coordinate of the centre of gravity of the aircraft (6). Once performed the calibration steps, the determination of the X-coordinate of the centre of gravity of the aircraft (6) can be performed based on the responses of the sensors (4) according to one or several of the following expressions:

Xe.sup.App1=(302.2+.sup.bridge3)+(2523.8.sup.bridge10)+(393.1.sup.bridge11)+(570.3.sup.bridge17)+11223.3Approach 1:

Xe.sup.App2=(272.6.sup.bridge3)+(807.4.sup.bridge9)+(1508.3.sup.bridge10)+(571.7.sup.bridge17)+11341.5Approach 2:

Xe.sup.App3=(274.9.sup.bridge3)+(632.6.sup.bridge9)+(570.8.sup.bridge17)+11428.6Approach 3:

Xe.sup.App4=(688.2.sup.bridge1)+(559.8.sup.bridge9)+(570.2.sup.bridge17)+11481.6Approach 4:

[0236] xi) In this example, the first plurality of installed sensors includes the calibration sensors in the first groups of sensors selected in step vii) and the calibration sensors in the second groups of sensors selected in step x), specifically calibration sensors 1, 3, 5, 9, 10, 11 and 17.

[0237] Once the approaches for determining the weight (W) of the aircraft (6) have been obtained in calibration step vii), it is shown below a check that the weight approaches are satisfied for all the loading states i. For this, it is determined a weight residual value (w.sub.i) to verify that said obtained weight residual value (w.sub.i) is small, wherein w.sub.i=100(We.sub.iW.sub.i)/W.sub.i.

[0238] The following tables 11A-11B to 19A-19B show the estimated weight (We.sub.i) obtained in the calibration step vi), the subtraction of We.sub.i minus W.sub.i and the weight residual value (w.sub.i) for each weight approach and each loading state i respectively. In these tables the weight residual value (w.sub.i) has been denoted (Error W).sub.i.

TABLE-US-00048 TABLE 11A CONFIGURATION 1: six loading states Approach 1 Approach 2 Wei Wei Wi (Error Wei Wei Wi (Error (N) (N) W)i (%) (N) (N) W)i (%) 109948.564 1073.516 0.967 109336.959 1685.121 1.518 115644.949 1359.691 1.162 115131.437 1873.203 1.601 122811.347 513.587 0.420 122731.325 433.565 0.355 116973.050 1569.690 1.360 116380.646 977.286 0.847 110457.225 431.415 0.389 110429.150 459.490 0.414 103419.071 108.129 0.104 103366.964 160.236 0.155

TABLE-US-00049 TABLE 11B CONFIGURATION 1: six loading states Approach 3 Approach 4 Wei Wei Wi (Error Wei Wei Wi (Error (N) (N) W)i (%) (N) (N) W)i (%) 109332.062 1690.018 1.522 109444.150 1577.930 1.421 115260.537 1744.103 1.491 114976.328 2028.312 1.734 123181.516 883.756 0.723 122668.120 370.360 0.303 116787.422 1384.062 1.199 116719.527 1316.167 1.140 109938.178 950.462 0.857 111042.493 153.853 0.139 102719.440 807.760 0.780 104384.185 856.985 0.828

TABLE-US-00050 TABLE 12A CONFIGURATION 2: six loading states Approach 1 Approach 2 Wei Wei Wi (Error Wei Wei Wi (Error (N) (N) W)i (%) (N) (N) W)i (%) 107734.091 952.789 0.877 106902.448 1784 1.64 113746.857 411.063 0.360 113238.508 919 0.81 121459.891 1297.171 1.080 120901.919 739 0.62 114532.618 1798.058 1.595 114056.485 1322 1.17 108071.443 14.957 0.014 107036.658 1050 0.97 103717.322 368.042 0.356 102850.655 499 0.48

TABLE-US-00051 TABLE 12B CONFIGURATION 2: six loading states Approach 3 Approach 4 Wei Wei Wi (Error Wei Wei Wi (Error (N) (N) W)i (%) (N) (N) W)i (%) 107033.080 1653.800 1.522 107334.331 1352.549 1.244 113233.535 924.385 0.810 113485.094 672.826 0.589 120863.316 700.596 0.583 121017.248 854.528 0.711 114177.419 1442.859 1.280 114648.254 1913.694 1.698 107556.163 530.237 0.491 106727.600 1358.800 1.257 103411.940 62.660 0.061 102833.303 515.977 0.499

TABLE-US-00052 TABLE 13A CONFIGURATION 3: six loading states Approach 1 Approach 2 Wei Wei Wi (Error Wei Wei Wi (Error (N) (N) W)i (%) (N) (N) W)i (%) 107926.108 1272.292 1.165 108122.524 1075.876 0.985 114287.281 849.199 0.738 114883.642 252.838 0.220 120353.946 31.174 0.026 121172.235 787.115 0.654 115738.273 668.513 0.581 116404.779 1335.019 1.160 108634.846 919.394 0.839 108500.776 1053.464 0.962 103882.990 266.930 0.256 103579.188 570.732 0.548

TABLE-US-00053 TABLE 13B CONFIGURATION 3: six loading states Approach 3 Approach 4 Wei Wei Wi (Error Wei Wei Wi (Error (N) (N) W)i (%) (N) (N) W)i (%) 107726.375 1472.025 1.348 107853.734 1344.666 1.231 114401.579 734.901 0.638 114471.947 664.533 0.577 120779.046 393.926 0.327 120570.177 185.057 0.154 115995.272 925.512 0.804 115961.744 891.984 0.775 108414.969 1139.271 1.040 108664.251 889.989 0.812 103273.587 876.333 0.841 103776.872 373.048 0.358

TABLE-US-00054 TABLE 14A CONFIGURATION 4: five loading states Approach 1 Approach 2 Wei Wei Wi (Error Wei Wei Wi (Error (N) (N) W)i (%) (N) (N) W)i (%) 115654.412 273.292 0.237 115036.758 344.362 0.298 127465.421 297.101 0.234 127225.883 57.563 0.045 138300.782 79.182 0.057 138745.570 523.970 0.379 122859.913 1140.393 0.937 122703.194 983.674 0.808 103374.989 597.011 0.574 103912.090 59.910 0.058

TABLE-US-00055 TABLE 14B CONFIGURATION 4: five loading states Approach 3 Approach 4 Wei Wei Wi (Error Wei Wei Wi (Error (N) (N) W)i (%) (N) (N) W)i (%) 115125.109 256.011 0.222 115254.350 126.770 0.110 127310.001 141.681 0.111 126809.203 359.117 0.282 138994.816 773.216 0.559 137446.595 775.005 0.561 123671.147 1951.627 1.603 123005.105 1285.585 1.056 102504.076 1467.924 1.412 104228.222 256.222 0.246

TABLE-US-00056 TABLE 15A CONFIGURATION 5: six loading states Approach 1 Approach 2 Wei Wei Wi (Error Wei Wei Wi (Error (N) (N) W)i (%) (N) (N) W)i (%) 103579.156 392.844 0.378 104096.635 124.635 0.120 115969.240 365.720 0.316 116554.789 951.269 0.823 126714.684 146.844 0.116 126480.027 87.813 0.069 136460.101 951.781 0.702 136653.308 1144.988 0.845 120919.588 1201.668 1.004 121340.072 1622.152 1.355 103774.348 1403.628 1.371 103597.023 1226.303 1.198

TABLE-US-00057 TABLE 15B CONFIGURATION 5: six loading states Approach 3 Approach 4 Wei Wei Wi (Error Wei Wei Wi (Error (N) (N) W)i (%) (N) (N) W)i (%) 102707.850 1264.150 1.216 104415.173 443.173 0.426 115548.258 55.262 0.048 116748.198 1144.678 0.990 126882.744 314.904 0.249 126789.620 221.780 0.175 137110.072 1601.752 1.182 136523.422 1015.102 0.749 121018.638 1300.718 1.086 121509.089 1791.169 1.496 103757.408 1386.688 1.355 104777.513 2406.793 2.351

TABLE-US-00058 TABLE 16A CONFIGURATION 6: six loading states Approach 1 Approach 2 Wei Wei Wi (Error Wei Wei Wi (Error (N) (N) W)i (%) (N) (N) W)i (%) 103475.797 1105.077 1.079 103496.991 1126.271 1.100 114121.910 30.710 0.027 114345.336 254.136 0.223 123915.847 1962.553 1.559 124229.581 1648.819 1.310 134284.806 734.234 0.544 135195.347 176.307 0.131 121254.584 1069.624 0.890 121383.759 1198.799 0.997 100835.340 1357.460 1.328 100590.354 1602.446 1.568

TABLE-US-00059 TABLE 16B CONFIGURATION 6: six loading states Approach 3 Approach 4 Wei Wei Wi (Error Wei Wei Wi (Error (N) (N) W)i (%) (N) (N) W)i (%) 103526.181 1155 1.13 104718.952 2348 2.29 113143.473 948 0.83 114442.587 351 0.31 123197.998 2680 2.13 123357.663 2521 2.00 134608.684 410 0.30 133742.688 1276 0.95 121800.653 1616 1.34 121710.046 1525 1.27 99828.893 2364 2.31 101108.485 1084 1.06

TABLE-US-00060 TABLE 17A CONFIGURATION 7: six loading states Approach 1 Approach 2 Wei Wei Wi (Error Wei Wei Wi (Error (N) (N) W)i (%) (N) (N) W)i (%) 101659.254 533.546 0.522 100991.735 1201.065 1.175 113240.473 494.887 0.435 112507.813 1227.547 1.079 124706.957 281.843 0.225 124304.588 684.212 0.547 136006.963 390.957 0.287 136029.344 368.576 0.270 119263.349 476.811 0.398 119462.956 277.204 0.232 103000.784 607.824 0.594 102653.084 260.124 0.254

TABLE-US-00061 TABLE 17B CONFIGURATION 7: six loading states Approach 3 Approach 4 Wei Wei Wi (Error Wei Wei Wi (Error (N) (N) W)i (%) (N) (N) W)i (%) 100388.960 1803.840 1.765 101247.400 945.400 0.925 112208.041 1527.319 1.343 112675.391 1059.969 0.932 124364.214 624.586 0.500 124335.231 653.569 0.523 136153.196 244.724 0.179 135619.167 778.753 0.571 119389.671 350.489 0.293 119145.016 595.144 0.497 103174.073 781.113 0.763 103287.798 894.838 0.874

TABLE-US-00062 TABLE 18A CONFIGURATION 8: five loading states Approach 1 Approach 2 Wei Wei Wi (Error Wei Wei Wi (Error (N) (N) W)i (%) (N) (N) W)i (%) 103078.945 685.985 0.670 102678.592 285.632 0.279 111065.588 490.252 0.439 110375.276 1180.564 1.058 120266.346 726.346 0.608 119970.855 430.855 0.360 112407.615 1341.055 1.207 112587.226 1520.666 1.369 101671.578 498.982 0.488 100684.112 1486.448 1.455

TABLE-US-00063 TABLE 18B CONFIGURATION 8: five loading states Approach 3 Approach 4 Wei Wei Wi (Error Wei Wei Wi (Error (N) (N) W)i (%) (N) (N) W)i (%) 103326.090 933.130 0.911 103401.188 1008.228 0.985 110377.875 1177.965 1.056 110683.614 872.226 0.782 119909.858 369.858 0.309 120630.377 1090.377 0.912 112323.053 1256.493 1.131 113394.494 2327.934 2.096 100695.260 1475.300 1.444 100879.068 1291.492 1.264

TABLE-US-00064 TABLE 19A CONFIGURATION 9: five loading states Approach 1 Approach 2 Wei Wei Wi (Error Wei Wei Wi (Error (N) (N) W)i (%) (N) (N) W)i (%) 100897.369 1224.731 1.199 100730.350 1391.750 1.363 146615.444 534.556 0.363 147551.129 401.129 0.273 183209.184 2592.216 1.395 186796.344 994.944 0.535 146183.456 603.056 0.414 146327.336 746.936 0.513 103897.388 1284.788 1.252 102668.802 56.202 0.055

TABLE-US-00065 TABLE 19B CONFIGURATION 9: five loading states Approach 3 Approach 4 Wei Wei Wi (Error Wei Wei Wi (Error (N) (N) W)i (%) (N) (N) W)i (%) 100259.757 1862.343 1.824 101095.005 1027.095 1.006 147995.318 845.318 0.574 146690.950 459.050 0.312 187002.658 1201.258 0.647 183691.178 2110.222 1.136 148589.621 3009.221 2.067 146526.219 945.819 0.650 104386.737 1774.137 1.729 104052.650 1440.050 1.403

[0239] Furthermore, once the approaches for determining the X-coordinate of the centre of gravity of the aircraft (6) have been obtained in the calibration step x), it is shown below a check that the approaches for determining the X-coordinate are satisfactory for all the loading states i. For this, it is determined an error (Error X).sub.i to verify that said obtained error is small, wherein (Error X).sub.i=100(Xe.sub.iX.sub.i)/2561, wherein such error is calculated according to the overage chord length of the aircraft (6) that is 2561 mm in this example.

[0240] The following tables 20A-20B to 28A-28B show the estimate weight Xe.sub.i obtained in the calibration step ix), the subtraction of Xe.sub.i minus X.sub.i and the (Error X).sub.i for each weight approach and each loading state i respectively.

TABLE-US-00066 TABLE 20A CONFIGURATION 1: six loading states Approach 1 Approach 2 Xei Xei Xi (Error X)i Xei Xei Xi (Error X)i (mm) (mm) (%) (mm) (mm) (%) 11136.066 18.720 0.731 11139.023 21.677 0.846 10907.772 71.777 2.803 10908.658 72.663 2.837 10593.342 21.314 0.832 10594.190 20.466 0.799 10935.783 12.510 0.488 10932.669 15.624 0.610 11186.558 22.143 0.865 11188.943 24.527 0.958 11394.864 29.844 1.165 11394.086 30.622 1.196

TABLE-US-00067 TABLE 20B CONFIGURATION 1: six loading states Approach 3 Approach 4 Xei Xei Xi (Error X)i Xei Xei Xi (Error X)i (mm) (mm) (%) (mm) (mm) (%) 11132.637 15.291 0.597 11135.413 18.067 0.705 10901.449 65.454 2.556 10904.648 68.654 2.681 10595.984 18.672 0.729 10596.849 17.806 0.695 10929.102 19.192 0.749 10929.632 18.662 0.729 11184.980 20.565 0.803 11177.962 13.546 0.529 11392.846 31.862 1.244 11384.282 40.426 1.579

TABLE-US-00068 TABLE 21A CONFIGURATION 2: six loading states Approach 1 Approach 2 Xei Xei Xi (Error X)i Xei Xei Xi (Error X)i (mm) (mm) (%) (mm) (mm) (%) 11507.900 1.989 0.078 11505.384 4.505 0.176 11562.908 27.465 1.072 11558.962 31.411 1.227 11656.214 17.723 0.692 11660.544 13.393 0.523 11578.985 0.193 0.008 11585.886 6.708 0.262 11469.759 39.501 1.542 11468.388 40.871 1.596 11408.230 12.020 0.469 11406.466 13.785 0.538

TABLE-US-00069 TABLE 21B CONFIGURATION 2: six loading states Approach 3 Approach 4 Xei Xei-Xi (Error X)i Xei Xei-Xi (Error X)i (mm) (mm) (%) (mm) (mm) (%) 11501.730 8.158 0.319 11505.024 4.864 0.190 11555.748 34.625 1.352 11556.988 33.385 1.304 11651.306 22.631 0.884 11650.408 23.528 0.919 11586.326 7.148 0.279 11585.039 5.860 0.229 11468.124 41.135 1.606 11482.133 27.127 1.059 11413.547 6.703 0.262 11426.723 6.472 0.253

TABLE-US-00070 TABLE 22A CONFIGURATION 3: six loading states Approach 1 Approach 2 Xei Xei-Xi (Error X)i Xei Xei-Xi (Error X)i (mm) (mm) (%) (mm) (mm) (%) 11193.740 30.860 1.205 11185.753 22.873 0.893 10956.661 32.100 1.253 10950.132 25.570 0.998 10726.427 12.539 0.490 10726.941 12.025 0.470 10925.569 14.431 0.564 10920.049 19.951 0.779 11161.407 4.242 0.166 11159.736 2.571 0.100 11370.676 24.878 0.971 11362.273 33.280 1.300

TABLE-US-00071 TABLE 22B CONFIGURATION 3: six loading states Approach 3 Approach 4 Xei Xei-Xi (Error X)i Xei Xei-Xi (Error X)i (mm) (mm) (%) (mm) (mm) (%) 11189.436 26.555 1.037 11193.178 30.298 1.183 10953.622 29.061 1.135 10954.260 29.699 1.160 10730.560 8.406 0.328 10730.425 8.541 0.333 10925.409 14.591 0.570 10926.265 13.735 0.536 11162.337 5.173 0.202 11164.471 7.307 0.285 11361.707 33.846 1.322 11364.262 31.291 1.222

TABLE-US-00072 TABLE 23A CONFIGURATION 4: five loading states Approach 1 Approach 2 Xei Xei-Xi (Error X)i Xei Xei-Xi (Error X)i (mm) (mm) (%) (mm) (mm) (%) 11340.745 23.500 0.918 11341.664 22.581 0.882 11321.121 23.155 0.904 11317.413 26.862 1.049 11320.782 0.068 0.003 11313.757 7.092 0.277 11389.357 7.887 0.308 11386.535 5.065 0.198 11425.339 10.595 0.414 11424.925 10.181 0.398

TABLE-US-00073 TABLE 23B CONFIGURATION 4: five loading states Approach 3 Approach 4 Xei Xei-Xi (Error X)i Xei Xei-Xi (Error X)i (mm) (mm) (%) (mm) (mm) (%) 11335.512 28.733 1.122 11336.197 28.048 1.095 11311.654 32.622 1.274 11312.930 31.346 1.224 11319.840 1.009 0.039 11326.127 5.277 0.206 11406.231 24.761 0.967 11411.066 29.596 1.156 11420.113 5.369 0.210 11411.170 3.574 0.140

TABLE-US-00074 TABLE 24A CONFIGURATION 5: five loading states Approach 1 Approach 2 Xei Xei-Xi (Error X)i Xei Xei-Xi (Error X)i (mm) (mm) (%) (mm) (mm) (%) 11423.878 9.134 0.357 11423.419 8.675 0.339 11312.203 10.277 0.401 11310.417 8.492 0.332 11218.488 5.632 0.220 11223.579 0.541 0.021 11120.367 30.519 1.192 11126.869 24.017 0.938 11246.176 21.611 0.844 11248.162 19.625 0.766 11409.889 14.952 0.584 11414.976 9.865 0.385

TABLE-US-00075 TABLE 24B CONFIGURATION 5: five loading states Approach 3 Approach 4 Xei Xei-Xi (Error X)i Xei Xei-Xi (Error X)i (mm) (mm) (%) (mm) (mm) (%) 11418.442 3.698 0.144 11409.566 5.178 0.202 11305.773 3.848 0.150 11295.794 6.132 0.239 11223.608 0.512 0.020 11220.994 3.125 0.122 11130.099 20.788 0.812 11127.436 23.451 0.916 11251.082 16.705 0.652 11245.428 22.358 0.873 11429.092 4.251 0.166 11426.465 1.624 0.063

TABLE-US-00076 TABLE 25A CONFIGURATION 6: six loading states Approach 1 Approach 2 Xei Xei-Xi (Error X)i Xei Xei-Xi (Error X)i (mm) (mm) (%) (mm) (mm) (%) 11408.630 16.211 0.633 11413.504 11.337 0.443 11565.346 21.332 0.833 11566.895 22.881 0.893 11575.284 55.552 2.169 11568.640 62.195 2.429 11736.004 43.580 1.702 11732.613 40.189 1.569 11604.991 18.791 0.734 11608.822 22.622 0.883 11425.362 2.353 0.092 11433.574 10.565 0.413

TABLE-US-00077 TABLE 25B CONFIGURATION 6: six loading states Approach 3 Approach 4 Xei Xei-Xi (Error X)i Xei Xei-Xi (Error X)i (mm) (mm) (%) (mm) (mm) (%) 11429.305 4.464 0.174 11425.099 0.258 0.010 11554.890 10.876 0.425 11545.602 1.588 0.062 11557.115 73.720 2.879 11554.240 76.595 2.991 11738.766 46.342 1.810 11741.482 49.058 1.916 11626.788 40.588 1.585 11627.411 41.212 1.609 11427.484 4.475 0.175 11424.106 1.096 0.043

TABLE-US-00078 TABLE 26A CONFIGURATION 7: six loading states Approach 1 Approach 2 Xei Xei-Xi (Error X)i Xei Xei-Xi (Error X)i (mm) (mm) (%) (mm) (mm) (%) 11432.179 9.170 0.358 11438.390 15.381 0.601 11502.177 7.661 0.299 11503.147 6.691 0.261 11590.410 18.107 0.707 11593.340 21.037 0.821 11653.545 20.855 0.814 11660.901 28.211 1.102 11543.481 8.578 0.335 11541.608 10.452 0.408 11429.627 16.909 0.660 11427.587 14.870 0.581

TABLE-US-00079 TABLE 26B CONFIGURATION 7: six loading states Approach 3 Approach 4 Xei Xei-Xi (Error X)i Xei Xei-Xi (Error X)i (mm) (mm) (%) (mm) (mm) (%) 11425.917 2.907 0.114 11426.385 3.376 0.132 11488.403 21.435 0.837 11487.706 22.132 0.864 11586.601 14.298 0.558 11585.772 13.469 0.526 11657.733 25.042 0.978 11656.894 24.204 0.945 11548.565 3.494 0.136 11551.930 0.130 0.005 11446.350 33.632 1.313 11452.938 40.220 1.570

TABLE-US-00080 TABLE 27A CONFIGURATION 8: five loading states Approach 1 Approach 2 Xei Xei-Xi (Error X)i Xei Xei-Xi (Error X)i (mm) (mm) (%) (mm) (mm) (%) 11419.388 6.670 0.260 11418.375 5.657 0.221 11330.120 5.257 0.205 11332.622 7.759 0.303 11264.790 1.091 0.043 11271.879 8.180 0.319 11330.075 11.256 0.440 11339.475 1.856 0.072 11414.069 2.999 0.117 11413.009 1.939 0.076

TABLE-US-00081 TABLE 27B CONFIGURATION 8: five loading states Approach 3 Approach 4 Xei Xei-Xi (Error X)i Xei Xei-Xi (Error X)i (mm) (mm) (%) (mm) (mm) (%) 11438.654 25.937 1.013 11445.525 32.807 1.281 11324.350 0.513 0.020 11325.688 0.825 0.032 11263.387 0.313 0.012 11256.374 7.325 0.286 11344.093 2.762 0.108 11337.119 4.212 0.164 11406.599 4.471 0.175 11413.501 2.431 0.095

TABLE-US-00082 TABLE 28A CONFIGURATION 9: five loading states Approach 1 Approach 2 Xei Xei-Xi (Error X)i Xei Xei-Xi (Error X)i (mm) (mm) (%) (mm) (mm) (%) 11399.206 13.652 0.533 11398.602 14.256 0.557 11388.292 21.345 0.833 11399.287 10.350 0.404 11377.973 21.042 0.822 11420.301 21.286 0.831 11358.023 73.608 2.874 11384.173 47.458 1.853 11385.643 14.620 0.571 11388.926 11.337 0.443

TABLE-US-00083 TABLE 28B CONFIGURATION 9: five loading states Approach 3 Approach 4 Xei Xei-Xi (Error X)i Xei Xei-Xi (Error X)i (mm) (mm) (%) (mm) (mm) (%) 11400.112 12.745 0.498 11400.839 12.019 0.469 11413.602 3.965 0.155 11414.256 4.619 0.180 11462.954 63.939 2.497 11466.204 67.189 2.624 11422.004 9.627 0.376 11429.763 1.868 0.073 11413.964 13.701 0.535 11424.239 23.976 0.936

[0241] Therefore, this example performed on an aircraft shows that the method of the present invention provides valid estimations for the values of the weight and the X-coordinate of the position of the centre of gravity of the aircraft. Also, it has been shown that the method allows obtaining several mathematical expressions for determining the values of the weight and of the position of the centre of gravity. The fact that different mathematical expressions provide very similar results shows that the results are accurate and reliable.

[0242] While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms comprise or comprising do not exclude other elements or steps, the terms a or one do not exclude a plural number, and the term or means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.

METHOD AND SYSTEM FOR DETERMINING THE WEIGHT AND CENTRE OF GRAVITY OF A STRUCTURE

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G01M1/125

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