Navigation instrument with tilt compensation mounted on or integrated into a wearable device and associated method
AssigneeETA SA Manufacture Horlogere Suisse
InventorRomain Besuchet
Life of this patent
Estimating the term…
Abstract
A navigation instrument including an orientation angle calculation unit, in particular the first and second orientation angles, wherein the orientation angle calculation unit is configured to be able to determine the first and second orientation angles in a given order and also in reverse order; and wherein the calculation unit is arranged to be able to choose between said given order and said reverse order, to calculate the first and second orientation angles, based on a comparison between an indicator of a risk of error, quantifying a risk of instability of said unit during the determination of the first and second orientation angles, and a predetermined threshold.
Claims22
A method for determining the angles of orientation of a navigation instrument (4) with respect to a terrestrial reference frame (, , ), this method comprising the following steps:
- acquisition of components of a first vector, called first measured vector, of a first terrestrial force field in a reference frame (, , ) linked to said navigation instrument, called on-board reference frame;
- determination of a first angle of orientation and of a second angle of orientation of the on-board reference frame with respect to the terrestrial reference frame, these first and second orientation angles being defined by two successive rotations of the first measured vector, around a first reference axis of rotation for the first orientation angle and a second reference axis of rotation for the second orientation angle, allowing to align the first measured vector with a calculation vector having, in the on-board reference frame, three calculation components which are identical with three reference components, in the terrestrial reference frame, of a first reference vector which is predefined or predetermined in the terrestrial reference frame;
- said determination comprising, to calculate the first and second orientation angles, a step of choosing between a given order for the two successive rotations and a reverse order based on a comparison between an indicator of a risk of error, quantifying a risk of instability during the determination of the first and second orientation angles, and a predetermined threshold, said indicator of the risk of error being determined based on at least one of said components of the first measured vector,
- wherein the navigation instrument is configured to be mounted on or integrated into a wearable device (2), and
- wherein said indicator of the risk of error is the norm of the projection of the first vector measured in a plane perpendicular to the first reference axis of rotation;
- and wherein, when said indicator of the risk of error is greater than said predetermined threshold, the first orientation angle is calculated based on said given order by firstly performing, among said two successive rotations, the rotation of the first vector measured around the first reference axis of rotation.
A method for determining the angles of orientation of a navigation instrument (4) with respect to a terrestrial reference frame ({right arrow over (1x)}, {right arrow over (1y)}, {right arrow over (1z)}), this method comprising the following steps:
- acquisition of components of a first vector, called first measured vector, of a first terrestrial force field in a reference frame ({right arrow over (1x′)}, {right arrow over (1y′)}, {right arrow over (1z′)}) linked to said navigation instrument, called on-board reference frame;
- determination of a first angle of orientation and of a second angle of orientation of the on-board reference frame with respect to the terrestrial reference frame, these first and second orientation angles being defined by two successive rotations of the first measured vector, around a first reference axis of rotation for the first orientation angle and a second reference axis of rotation for the second orientation angle, allowing to align the first measured vector with a calculation vector having, in the on-board reference frame, three calculation components which are identical with three reference components, in the terrestrial reference frame, of a first reference vector which is predefined or predetermined in the terrestrial reference frame;
- said determination comprising, to calculate the first and second orientation angles, a step of choosing between a given order for the two successive rotations and a reverse order based on a comparison between an indicator of a risk of error, quantifying a risk of instability during the determination of the first and second orientation angles, and a predetermined threshold, said indicator of the risk of error being determined based on at least one of said components of the first measured vector,
- wherein the navigation instrument is configured to be mounted on or integrated into a wearable device (2), and
- wherein said indicator of the risk of error is the absolute value of the second orientation angle when, in said given order, the first orientation angle is calculated before the second orientation angle;
- and wherein, when said indicator of the risk of error is greater than said predetermined threshold, the first and second orientation angles are again calculated in said reverse order by performing, among said two successive rotations, firstly the rotation of the first vector measured around the second reference axis of rotation;
- the values of the recalculated first and second orientation angles then being retained for these first and second orientation angles.
Dependencies are inferred from the claim text.