RU2334947C1 - Method of calibration of sensitive elements of strapdown inertial navigation system and device for its implementation - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: invention is related to the field of instrument making and may be used in creation of strapdown inertial control systems (SICS) for calibration of sensitive elements (SE). In biaxial Cardan suspension (CS) instrument platform is installed, on which in special manner three accelerometers and three angular speed detectors (ASD) are installed. On CS axes angle detectors (AD) are installed and motors for setting of accelerometers IO and ASDs into working positions for calibration. At that in device for method implementation into biaxial CS instrument platform (IP) is installed, on which three accelerometers and three ASDs are installed. On CS axes ADs and motors are installed, for rotation of IP in relation to the object.

EFFECT: increase of calibration accuracy.

2 cl, 2 dwg

Description

The invention relates to the field of instrumentation and can be used to create strapdown inertial navigation systems (SINS).

Currently, there is a known method of constructing a strapdown inertial block (BIB) in a gimbal (Patent for invention No. 2241959 with priority dated 05/20/03). A known method of calibration of sensitive elements (SE), in bench tests (U. Wrigley, U. Hollister, U. Denhard, “Theory, design and testing of gyroscopes”, M., Mir, 1972), adopted as a prototype. A disadvantage of the known method for calibrating CE BINS on special stands is the inability to calibrate them without removing from the product.

The objective of the present invention is to improve the accuracy characteristics of the SE BIB by means of their calibrated calibration without removing from the product.

The studies show that when building SINS according to the classical scheme of rigid fastening of the block of accelerometers and angular velocity sensors (DLS) on the product, it is currently not possible to provide the required accuracy characteristics of the inertial control system (IMS). This is due to the fact that the available element base, that is, accelerometers and TLS, without preliminary (refined) calibration before starting work does not have the required accuracy characteristics in the given ranges of measured values. Calibration of the main parameters of the SE BIB before starting work can significantly improve the accuracy characteristics of the ISU.

The objective of the claimed invention is to determine (clarify) the following parameters for calibrating SE:

for accelerometers:

- zero offset and scale factor (pulse price of the accelerometer signal),

for angular velocity sensors:

- the speed of departure (drift (“drift”) of zero) and the scale factor (pulse price of the TLS signal).

In the process of refined calibration, the values of the calibration parameters are determined for their subsequent consideration in the control system algorithms (the initial calibration of the CE is performed during their manufacture).

With a rigid fastening of the CE on the product, the possibility of their calibration can be provided on a special stand before being placed on the product. CEs, rigidly fixed on the product, cannot be calibrated.

The proposed method for calibrating a SE BINS and a device for its implementation makes it possible to calibrate all SE using a biaxial cardan suspension BIB and with a special arrangement of measuring axes (IO) of the SE relative to the axes of a biaxial cardan suspension.

To explain the work, the following notation is used.

Right rectangular coordinate systems:

XYZ - horizontal coordinate system; Y axis is directed in the vertical direction; X and Z axes are located in the horizon plane;

OX ₁ Y ₁ Z ₁ - the coordinate system associated with the managed object.

X _d Y _d Z _d - coordinate system formed by the corresponding measuring axes of the DOS.

X _a Y _a Z _a - coordinate system formed by the corresponding measuring axes of the accelerometers.

Figure 1 presents the device that implements the claimed calibration method.

Figure 2 presents the relationship between the elements of the claimed device.

The most preferred at present is the arrangement of three accelerometers (4.1, 4.2, 4.3) and three DOSs (5.1, 5.2, 5.3), shown in figure 1, which shows the initial initial position at which all the coordinate systems used with the object are deployed around the Z axis relative to the horizontal coordinate system at an angle μ. The inner axis of the gimbal is set horizontally. The coordinate system X _a Y _a Z _{a is} rotated around the axis Y _a from the inner axis of the cardan suspension by a design angle Ф ₃ = 45 °. The readings of the angle sensors mounted on the axles of the gimbal are consistent with the zero value of the angles Ф ₁ = Ф ₂ = 0.

The outer axis biaxial suspension set angle sensor DU1 (6.1) and D1 rotation motor (7.1), the outer axis coincides with the axis X _1, on the inner axis gimbal mounted angle sensor dy2 (6.2) and D2 of rotation of the motor (7.2), the inner axis the cardan suspension coincides with the Z axis. Amplifiers (8.1 and 8.2) of signals coming from the computing device (9) to the rotation motors and a consumer of calibration parameters (10) are installed on the object’s body (1). In the initial zero position of the dashboard shown in FIG. 1, the signals from the angle sensors DN1 and DN2 are equal to zero.

The location scheme of the SE proposed in FIG. 1 allows, with a structurally defined angle Ф ₃ = 45 ° and a deviation of the outer axis of the cardan suspension from the horizontal plane by an angle μ in the range of ± 45 °, by turning the CE block at angles Ф ₁ and Ф _2, respectively around the external and internal axes of the gimbal suspension to ensure the exposure of the IO of each of the three accelerometers in both the positive and negative directions of the acceleration vector of gravity. The values of the angles Ф ₁ and Ф ₂ depending on the angle μ for the exposure of the IO of each accelerometer in the positive and negative directions of the gravity acceleration vector are determined by the final formulas in the computing device (WU) from the condition that the direction cosines between the measuring axis of the calibrated accelerometer and the vertical the calibration location is equal to plus or minus one.

The method of calibrating the sensitive elements of the strapdown inertial navigation system installed in the body of the controlled object consists in measuring the gravity acceleration vector (measuring the projections of the gravity acceleration vector on the measuring axes of the accelerometers) and the angles of rotation of the dashboard (PP), on which the accelerometers and angle sensors are mounted speed (TLS). To calibrate the accelerometers and DOSs, the software is installed in a biaxial cardan suspension (CP), on each axis of which an angle sensor and a rotation motor are installed. DOSs and accelerometers are installed on the PC in such a way that their measuring axes (IO) form the corresponding right rectangular coordinate systems X _d Y _d Z _d and X _a Y _a Z _a , while the IO Y _a and Y _{d are} orthogonal to the internal axis of the KP. The system X _a Y _a Z _{a is} deployed around the Y axis _and from the internal axis of the gearbox at a design angle Ф ₃ = 45 ° so that the AI Z _a forms an angle of 45 ° with the internal axis of the gearbox and lies with it in the PP plane. The axis Z _d parallel to the internal axis of the gearbox. U-turns to the required angles are carried out using the D1 and D2 engines, and the current values of the angles are controlled using signals taken from the angle sensors DU1 and DU2. Before starting calibration on the equality of signals from accelerometers, the measuring axes (X _a and Z _a ) of which lie in the PP plane, using the rotation motor mounted on the outer axis of the gearbox, set the instrument panel to the initial initial position at which the internal axis of the suspension will be located in the horizon plane. By signals from the angle sensor ДУ1 installed on the outer axis of the gearbox, this position is fixed in the control unit as the initial initial position. The signals from the accelerometer, the IO of which is orthogonal to the internal axis and the signals from the angle sensor ДУ2 installed on the internal axis of the cardan suspension in the VU, determine the angle μ of the deviation of the external axis of the KP from the horizontal plane. To do this, the instrument platform (PP) is deployed from the initial starting position around the KP internal axis by a certain angle ΔФ2, at which the measuring axis of the accelerometer Y _a will be deviated from the horizon plane by a small angle at which the accuracy of determining this angle is practically independent of the scale factor error accelerometer, measured by the signals of the accelerometer Y _{a the} value of this small angle, determined by the signals from the angle sensor DN2 the value of the angle of rotation ΔF ₂ , and then in the WU determine the value of the angle μ. Calibration of the accelerometers is carried out as follows: in the control unit for each accelerometer, the angles Ф ₁ and Ф _{2 of the} PP rotations from the initial position to the calibration positions are calculated, in which the calibrated accelerometer’s IO is set along the positive, then along the negative direction of gravity acceleration g, the dashboard according to the signals, formed in the slave, via D1 and D2 engines unfolded relative to the starting position on the angles F ₁ and F ₂ in the position calibration of accelerometers, wherein the hold using rotating motors calibrateable I accelerometers in the calibration positions for predetermined intervals of time in the slave, during which perform measurements calibrated accelerometer. Based on the measurement results obtained in the WU, the value of the scale factor and the zero offset of each calibrated accelerometer are calculated.

In particular, to calculate the calibration parameters, it is possible to measure the number of pulses from the output of the calibrated accelerometer for given time intervals and, based on the data obtained, calculate the scale factor and zero offset of the accelerometer in the control unit.

For calibration, the DOSs are positioned as follows: for the first and second DOS, the corresponding IO X _D and Y _D are combined with the direction of the outer axis of the gimbal, for the third DUS, IO Z _{D is} structurally set parallel to the inner axis of the suspension. (In the ideal starting position, the first and third TLS are in the calibration positions. The IO of the second TLS are set to the calibration position by turning the PP around the internal axis by an angle Ф ₂ = -90 ° from the starting position.)

Calibration of DOSs is carried out as follows: put the software in its original position. Measure the angular position of the axles of the gimbal suspension relative to the horizon plane and their azimuth (the azimuth of the outer axis of the suspension can be determined, for example, by vector matching (patent No. 2279635 dated 02.11.2004)), based on which the projection of the Earth's angular velocity of rotation is calculated on the axis of the gimbal. According to the signals from the control unit, the D2 engine combines the IO X _D and Y _{D of the} corresponding TLS with the direction of the outer axis of the gearbox, with the indicated combinations, with the help of the D1 engine, turn the PP with the given angular velocities around the outer axis of the suspension by a predetermined positive and then negative angle, at for this, during the turns, measurements are made by the angle sensor ДУ1 (the actual positive and negative angles of the PP rotations are measured, the values of which are taken as the reference ones) and the calibrated TLS determine the projections of the PP rotation vector as a result of Earth ascheniya the EUT Dusaev calibrated on the basis of the results of measurements in the TA, with the Earth's rotation is calculated values of the scale factors and an offset ( "drift") of zero for the first and second Dusan. In a similar way carry out the calibration of the third TLS. In this case, the PP using the D2 engine is rotated around the internal axis of the cardan suspension, while during the turns the measurements are performed by the third TLS and the D2 angle sensor, based on the obtained measurement results in the TU, taking into account the rotation of the Earth, the values of the scale factor and the zero offset of the third TLS are calculated .

In particular, in order to calculate the calibration parameters, it is possible to measure the number of pulses received from the calibrated TLS during the time of the U-turn at the corresponding given angles, measure the actual U-turn angles of the U-turn, the values of which are taken as the reference ones, and based on the data obtained, taking into account the Earth’s rotation, perform in WU the calculation of the scale factor and the zero offset of the TLS.

The claimed calibration method is carried out using a device for calibrating the sensitive elements of a strapdown inertial navigation system installed in the body of a managed object containing a dashboard (PP) with three accelerometers and three angular velocity sensors (DLS), and a computing device with inputs connected to the corresponding outputs of the accelerometers and DUSov, and outputs connected with the inputs of consumers of navigation parameters, a biaxial gimbal suspension (CP), on each axis of which is installed Lena corresponding angle sensor and the motor rotation. At the same time, the dashboard is installed in the control gear, the DOSs and accelerometers are installed on the PC so that their measuring axes (IO) form the corresponding right rectangular coordinate systems X _d Y _d Z _d and X _a Y _a Z _a . IO Y _a and Y _{d are} aligned with each other and are orthogonal to the inner axis of the gimbal, IO Z _a forms an angle of 45 ° with the inner axis of the gimbal and lies with it in the PP plane, and IO 2d is parallel to the inner axis of the gimbal. The computing device is made with the additional possibility of controlling the rotation motors and controlling the angular position of the PC by means of angle sensors, calculating the scale factor and zero offset of the calibrated sensor. The outputs DU1 and DU2 are connected to the corresponding additional inputs (inputs of signals from angle sensors) of the computing device, two additional outputs of which are connected through amplifiers to the corresponding inputs of rotation motors, and a third additional output is connected to the consumer input of the calibration parameters.

A feature of the proposed calibration method and device for its implementation is:

1. The ability to calibrate the CE BIB without removing from the product.

2. A special arrangement of the SE BIB in a biaxial cardan suspension, which allows calibration of scale factors and zero offset of all three accelerometers, as well as scale factors and drift drift of all three DOSs.

3. The ability to determine before starting calibration the initial initial position of the BIB unit relative to the horizon plane according to the signals of the BIB accelerometers and the initial position of the BIB relative to the body of the object based on the signals of the angle sensors mounted on the axles of the gimbal.

4. The possibility of exhibiting IO of accelerometers in the positive and negative direction of the gravity acceleration vector by turning the BIB instrument platform around the axles of the gimbal suspension at final angles determined in the computing device depending on the angle of deviation of the outer axis of the gimbal from the horizon.

5. Determination of scale factors and “drift” of DOSs by jointly processing signals from DOSs in a computing device and comparing the received information with angular information obtained as a result of processing signals from angle sensors mounted on the axles of the gimbal.

The technical result of the proposed calibration method and device for its implementation is to increase the accuracy of the strapdown inertial control system of a moving object and the ability to calibrate CE BINS without removal from the product.

Claims (2)

1. The method of calibration of the sensitive elements of the strapdown inertial navigation system installed in the body of the managed object, which consists in measuring the acceleration vector of gravity and the rotation angles of the dashboard (PP), on which accelerometers and angular velocity sensors (DLS) are installed, characterized in that the PP they install a gimbal (gearbox) in a biaxial gimbal, on each axis of which an angle sensor and a rotation motor are installed, and DLSs and accelerometers are installed on the PC so that their measuring axes ( IO) form the corresponding right-angular coordinate systems X _d Y _d Z _d and X _a Y _a Z _a , while IO Y _a and Y _{d are} orthogonal to the inner axis of the gearbox, the ZO _a forms an angle of 45 ° with the inner axis of the gearbox and lies with it in the PP plane, and ИО Z _d parallel to the internal axis of the gearbox, before starting calibration on the equality of signals from two accelerometers, the measuring axes of which lie in the plane of the gearbox, using the rotation motor mounted on the outer axis of the gearbox, set the internal axis of the gearbox to the horizontal plane, record the readings of an angle sensor mounted on the outside the axis of the gearbox, in the computing device (WU) as the source, according to the signals of the accelerometer, the measuring axis of which is orthogonal to the internal axis, and the signals from the angle sensor mounted on the inner axis of the gearbox, the angle of deviation of the outer axis of the gearbox from the horizon plane is determined for each accelerometer in WU according to the final formulas, the angles Ф ₁ and Ф _{2 of the} turns of the PP around the outer and inner axes from the initial position to the calibration position are calculated, in which the measuring axes of the calibrated accelerometer are located along the positive, then along the negative direction of gravity acceleration, the dashboard, according to the signals generated in the control unit, using rotation motors is rotated relative to the initial position by the angles Ф ₁ and Ф ₂ to the calibration positions of the accelerometers, hold calibrated accelerometers in the calibration positions for the time intervals specified in the control unit, during which measurements are performed by a calibrated accelerometer, the value of the scale factor and the zero offset of each calibrated accelerometer are calculated in the control unit; To calibrate the DOSs, the PPs are set to their initial position, the angular position of the KP axes relative to the horizon plane is measured and their azimuths are used, based on which the projection of the angular velocity of the Earth’s rotation on the KP axis is calculated using the signals from the VU combine measuring axis Y _d and Z _d DUSov corresponding with the direction of the outer gearbox axis, said alignment via rotation of the motor mounted on the outer gearbox axis PP is rotated with a predetermined angular speed the outer axis of the suspension is at a predetermined positive and then negative angle, while during the turns of the PP, measurements are made by an angle sensor mounted on the outer axis of the gearbox and calibrated by the TLS, the projections of the rotation vector as a result of the Earth's rotation on the measuring axis of the calibrated TLS are determined in WU , taking into account the rotation of the Earth, calculate the values of the scale factors and the zero offset for the first and second DOSs, in a similar way, calibrate the third DUS, while using the rotation motor installed On the internal axis of the gearbox, the instrument pad is rotated around the internal axis of the gearbox, during the rotations of the control panel, measurements are made by the third TLS and the angle sensor installed on the inner axis of the gearbox in the WU, taking into account the rotation of the Earth, the scale factor and the zero offset of the third TLS are calculated. 2. A device for calibrating the sensitive elements of a strapdown inertial navigation system installed in the body of a controlled object, containing a dashboard (PP) with three accelerometers and three angular velocity sensors (DLS), a computing device with inputs connected to the corresponding outputs of the accelerometers and DLS, and the outputs associated with the corresponding inputs of consumers of navigation parameters, a biaxial gimbal suspension (KP), on each axis of which there are installed an appropriate angle sensor and two tor rotation, while the PP is set to manual, DUSy and accelerometers are mounted on the PCB in such a manner that their measuring axis (EUT) form respective right rectangular system X _d Y coordinate _d Z _d and X _a Y _a Z _a, IO Y _a and Y _d orthogonal to the internal axis of the gearbox, ИО Z _a forms an angle of 45 ° with the internal axis of the gearbox and lies with it in the plane of the PP, and ИО Z _d parallel to the internal axis of the gearbox, the computing device is configured to control the rotation motors and control the angular position of the PP by means of sensors angle calculating scale factor and ZO calibrated sensor, the angle sensor outputs are connected to corresponding additional inputs of the computing device, two additional outputs which are connected via the amplifiers to respective inputs of engine rotation, and a third additional output coupled to an input user calibration parameters.

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