Sagem Defense Securite

Safran Electronics & Defense

Christian Lignon

Philippe Elie

Alain Renault

Sylvain Faure

Etienne Brunstein

Frédéric Davi

Yannick Foloppe

Arnauld Carre

Nicolas Gendre

Arnaud Carre

Inertial measurement apparatus arranged to be carried by a carrier vehicle include a chassis, a turntable mounted on the chassis, a first inertial measurement unit mounted on the turntable and connected to an electronic control unit connected to a motor for controlling turning of the turntable, and a second inertial measurement unit secured to the chassis. The control unit turns the turntable through one revolution with periodic alternating motion from a fixed initial angular position of the turntable. The control unit calculates the acceleration of the carrier vehicle from measuring the first inertial measurement unit while the turntable is stationary and from measuring the second inertial measurement unit while the turntable is moving. The control unit reconstitutes an inertial reference frame for each inertial measurement unit and compares the two inertial reference frames to determine a difference and takes account of this difference when calculating the acceleration.

Inertial measurement device

A method and a device resets an inertial unit of a transport on the basis of information delivered by a viewfinder of the transport. According to one embodiment: a horizontal velocity vector of the transport and coordinates of the transport are obtained from the inertial unit, a horizontal line of sight of the viewfinder is obtained on at least one landmark, coordinates of at least one landmark are obtained, an angle between the horizontal velocity vector and the horizontal line of sight is computed, the drift of the computed angle is computed, an error is computed on the basis of the obtained coordinates, the computed angle and its computed drift, and the computed error is transferred to a Kalman filter for filtering the error and resetting the inertial unit.

Method and device for resetting an inertial unit of a transport means on the basis of information delivered by a viewfinder of the transport means

A method of characterizing an inertial measurement unit includes a block carrying one accelerometer positioned on an axis of a measurement reference frame and having one gyro arranged to determine the orientation of the frame relative to an inertial reference frame. The method includes keeping the inertial measurement unit centered on a point that is stationary relative to the ground and that is in a predetermined environment, to obtain accelerometer signals that are images of at least one component of the specific force vector in the measurement reference frame and also gyro signals that are images of at least one component of the instantaneous rotation of the measurement reference frame; processing the signals to obtain data representative of projecting of the specific force vector into the inertial reference frame, after compensating for rotation of the Earth; and calculating Allan variance on the data and comparing it with reference data.

Method for characterising an inertial measurement unit

An inertial unit comprising an inertial core () that is connected to a control unit () and that includes three gyros () that are mounted relative to one another so as to have sensing axes (X, Y, Z) that are substantially perpendicular to one another, the gyros being vibrating axisymmetric gyros with hemispherical resonators, the unit being characterized in that the core is mounted on a carousel () arranged to drive the inertial core in rotation about an axis of rotation () at at least one frequency that corresponds to a minimum for spectral error density of the gyros. An angle-measurement method making use of the unit.

Inertial unit having vibrating gyros mounted on a carousel, and an angle-measurement method

A gyroscopic system provides measurements on the basis of a vibrating gyroscope and provides a measurement signal. A periodic control signal is applied to it; in order to rotate the position of vibration, during a half period, according to a first speed profile, from a first up to a second position; and in order to rotate the position of vibration in an opposite direction during the other part of the period, according to a second speed profile, up to a third position. The measurements are based on corrected signals, each of said corrected signals, respectively for each of the vibrating gyroscopes, being obtained by; deducting the control signal from the measurement signal of the vibrating gyroscope; and taking account of errors identified on the basis of a comparison of the measurements provided by the gyroscopic system as a function of the position of vibration with reference measurements.

Gyroscopic measurement in a navigation system

Gyroscopic measurements are provided, by a system comprising a vibrating gyroscope, in the form of an output signal. The vibrating gyroscope provides an original measurement signal. A periodic control signal (CP) is applied to it over a time period, which signal is suitable: for rotating the geometric position of vibration in a first direction, during a part of the time period; and for rotating the geometric position of vibration in a second direction opposite to the first direction, during the other part of the time period; said control signal having a zero mean over said time period and exhibiting portions of signal at high frequency relative to the output signal; said output signal being based on a corrected signal emanating from the original measurement signal; in which the corrected signal is based on an identification of errors made during the signal portions at high frequency.

Gyroscopic measurement by a gyroscope vibrating in precession

A long-term navigation method using an inertial unit associated with a system of axes X, Y, Z and mounted on a vehicle traveling relative to the Earth in order to measure its movements relative to an inertial frame of reference having axes Xi, Yi, and Zi. The method includes the steps of acting in permanent manner to measure an orientation of the system of axes X, Y, Z in the inertial frame of reference and applying a predetermined sequence of turnovers to the inertial unit in the inertial frame of reference about first and second axes that are substantially perpendicular to each other and in such a manner that at the end of the sequence the inertial unit is in a final orientation identical to its initial orientation relative to the inertial frame of reference, with the turnovers canceling within the sequence.

Method and device for long-duration navigation

A gyroscopic system supplies measurements on the basis of a vibratory gyroscope, which vibrates in a first vibration position and supplies a measurement signal. A periodic command signal is applied to it over a time period to cause the vibration geometrical position to turn a first way during one part of the time period, causing a change in accordance with a first speed profile from the first position to a second position; and to cause the vibration geometrical position to turn a second way opposite the first way during the other part of the time period, causing a change in accordance with a second speed profile from the second position to the first position. The speed profiles indicate a speed variation of the change of position. The measurements supplied by the system are then based on a corrected signal obtained by subtracting the command signal from the measurement signal supplied by the gyroscope.

Gyroscopic measurement by a vibratory gyroscope

A gyroscopic system is disclosed comprising at least a vibrating gyroscope, as a first mechanism of angle measurement, designed to provide a first measurement of angle values according to a measurement axis; and a second mechanism of angle measurement, designed to provide a second measurement of angle values according to said measurement axis. First angle values through the first angle measurement mechanism vibrating in a current vibration position and second angle values through the second angle measurement mechanism are provided simultaneously; and from these second angle values corrected on the basis of a comparison of the first and second angle values are deduced. Then the vibration position of the first angle measurement mechanism is changed from the current position to another vibration position. First angle values through the first angle measurement mechanism and second angle values through the second angle measurement mechanism are then provided simultaneously; and from these first angle values corrected on the basis of a comparison of the first and second angle values are deduced.

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Paris, France

Christian Lignon