| CPC G01C 21/16 (2013.01) | 9 Claims |
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1. A location system, configured to be mounted on a vehicle, for determining a position and an orientation of the vehicle, comprising:
an inertial navigation unit containing an accelerometer and a gyrometer configured to measure an acceleration and an angular speed of the vehicle at each instant tk of a temporally ordered series of instants {0, t1, t2, . . . , tk−1, tk, . . . };
an odometer configured to measure an angular speed of a wheel of the vehicle around its axis of rotation at each instant toj of a temporally ordered series of instants {0, to1, to2, toj−1, toj, . . . }, said angular speed measured at the instant toj being an average angular speed of the wheel in an interval [toj−1, toj], a frequency of the instants toj being less than a frequency of the instants tk, so that several instants tk are interspersed between immediately consecutive instants toj−1 and toj; and
an electronic computer configured to determine the position and the orientation of the vehicle on a basis of the measurements of the accelerometer, of the gyrometer and of the odometer,
wherein the electronic computer is configured to execute a method comprising:
acquiring using the electronic computer, at each instant tk of the temporally ordered series of instants {0, t1, t2, . . . , tk−1, tk, . . . }, a measurement of the acceleration and of the angular speed of the vehicle carried out by the inertial navigation unit;
constructing using an inertial measurement integration module, for each instant tk, an estimated position and orientation of the vehicle on a basis of a previous position and of a previous orientation of the vehicle and using the measurements of the acceleration and of the angular speed acquired at the instant tk;
acquiring, at each instant tot of the temporally ordered series of instants {0, to1, to2, . . . , toj−1, toj, . . . }, a new measurement of an angular speed of a wheel of the vehicle around its axis of rotation, with the angular speed acquired at the instant toj being an average angular speed of the wheel in an interval [toj−1, toj] delivered by an odometer, the frequency of the instants toj being less than the frequency of the instants tk, so that several instants tk are interspersed between immediately consecutive instants toj−1 and toj; and
for each instant toj;
constructing a measurement of a physical quantity on a basis of the average angular speed acquired at the instant toj, with the physical quantity being proportionate to a sum of instantaneous values of the physical quantity between the instants toj−1 and toj; and
constructing an estimate of the physical quantity at the instant toj on a basis of the measurements carried out by the inertial navigation unit and without using the measurement of the average angular speed acquired at the instant toj; then
computing a deviation between the measurement and the estimate of the physical quantity at the instant toj; and
correcting using a correction module, as a function of the deviation computed for the instant toj, estimated positions and orientations for an instant tk equal to or subsequent to the instant toj, in order to obtain a corrected position and a corrected orientation;
wherein the method also comprises:
for several instants tk ranging between the instants toj−1 and toj, constructing an estimate of the instantaneous value of the physical quantity on a basis of the measurements of the inertial navigation unit acquired at the instant tk; then
constructing the estimate of the physical quantity for the instant toj on a basis of a sum of the instantaneous values constructed for the instants tk ranging between the instants toj−1 and toj.
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