Method for taking the right of a four-axis inertial platform table body

Abstract

The application relates to the field of inertial measurement, and particularly discloses a method for taking the positive of a four-axis inertial platform table body, which comprises the following steps: acquiring the projection of a gravity vector in a table body coordinate system of the four-axis inertial platform; determining the projection of the gravity vector in a base coordinate system of the four-axis inertial platform according to the projection of the gravity vector in the table body coordinate system and frame angle information of the four-axis inertial platform; determining a target frame angle for platform taking the positive according to the projection of the gravity vector in the base coordinate system; and generating a rotation trajectory of the four-axis inertial platform according to the target frame angle. The scheme has the advantages that the precision jump and precision over tolerance of a three-floating gyroscope after long-time storage can be avoided.

Description

Technical Field

[0001] This application relates to the technical field of inertial measurement, and in particular to a method for calibrating a four-axis inertial platform. Background Technology

[0002] When a triple-floating gyroscope mounted on a platform is placed statically in a fixed posture for an extended period, the primary coefficient will change due to gravity, gradually stabilizing over time, with different stability values ​​for different postures. If the posture of the triple-floating gyroscope during static placement differs from its usage posture, when it is powered on again, the primary coefficient of the gyroscope will exhibit abrupt changes and accuracy deviations compared to its previous state.

[0003] After the inertial platform is transported or the carrier base is rotated, without active intervention, the platform body is in a free state under the torque coupling effects of shaft end friction, static unbalance, etc., meaning the spatial position of the platform body is uncertain. Therefore, the attitudes of the three three-float gyroscopes installed on the platform are all uncertain, and there is a high probability that there will be a large attitude deviation from the normal use state, which will cause the accuracy of the first term coefficient of the gyroscope to exceed the tolerance after long-term static placement.

[0004] To minimize the variation in the coefficients of the three-float gyroscope, the relationship between the instrument and the gravity vector should be kept as consistent as possible during storage as it is in operation, i.e., the Y-axis of the platform should be kept pointing upwards. Therefore, before storage, the platform should be powered on to perform a calibration process, rotating the Y-axis of the platform to the upward direction, and then the power should be turned off for storage. Summary of the Invention

[0005] This application provides a method for calibrating a four-axis inertial platform, the purpose of which is to avoid accuracy jumps and out-of-tolerance errors of the three-float gyroscope.

[0006] In a first aspect, a method for calibrating a four-axis inertial platform is provided, characterized by comprising:

[0007] Obtain the projection of the gravity vector onto the table coordinate system of the four-axis inertial platform;

[0008] Based on the projection of the gravity vector in the platform coordinate system and the frame angle information of the four-axis inertial platform, the projection of the gravity vector in the base coordinate system of the four-axis inertial platform is determined.

[0009] The target frame angle for platform orthogonalization is determined based on the projection of the gravity vector onto the base coordinate system.

[0010] Based on the target frame angle, the rotation trajectory of the four-axis inertial platform is generated.

[0011] Compared with the prior art, the solution provided in this application has at least the following beneficial technical effects:

[0012] Before static placement, the inertial platform is briefly powered on for a few minutes without heating or gyroscope operation, and the platform position is rotated to the Y-axis facing upwards (i.e., the platform's normal working posture).

[0013] In conjunction with the first aspect, in some implementations of the first aspect, the projection of the gravity vector onto the table coordinate system of the four-axis inertial platform satisfies:

[0014]

[0015] This is the projection vector of the gravity vector onto the table's coordinate system. The actual acceleration to compensate for the accelerometer error coefficient; δ ij The angle represents the installation error angle of accelerometer i about the j-axis of the platform coordinate system, in radians.

[0016] In conjunction with the first aspect, in some implementations of the first aspect, the projection of the gravity vector onto the table coordinate system of the four-axis inertial platform satisfies:

[0017] τ represents the time interval.

[0018] The projection of the gravity vector onto the table coordinate system of the four-axis inertial platform can be normalized, which helps to make the vector projection more accurate and stable.

[0019] In conjunction with the first aspect, in certain implementations of the first aspect, the frame angle information of the quadcopter inertial platform satisfies:

[0020]

[0021]

[0022]

[0023] θ x′ For the angle of the follower ring frame, θ y For the outer ring frame angle, θ x For the inner ring frame angle, θ z For the corner of the platform frame.

[0024] In conjunction with the first aspect, in some implementations of the first aspect, the projection of the gravity vector into the base coordinate system of the quadaxial inertial platform satisfy:

[0025] This represents the rotation matrix from the platform coordinate system to the base coordinate system, as described before the platform is positive. This indicates the projection of the gravity vector, as described before the platform is aligned, onto the platform's coordinate system.

[0026] In conjunction with the first aspect, in some implementations of the first aspect, the rotation matrix from the platform coordinate system to the base coordinate system after the platform is positive is... satisfy:

[0027] This represents the projection of the gravity vector onto the platform coordinate system after the platform is aligned.

[0028] In conjunction with the first aspect, in some implementations of the first aspect, the platform frame angle θ is positive after the platform is positive. z2 =arcsin(c1);

[0029] After the platform is calibrated, the following ring frame angle

[0030] After the platform is positive, the inner ring frame angle θ x2 =0;

[0031] After the platform is positive, the outer ring frame angle θ y2 =0,

[0032] in,

[0033] This helps ensure the uniqueness of the solution and reduces the amount of data processing required for the four-axis inertial platform to achieve positive values.

[0034] In conjunction with the first aspect, in some implementations of the first aspect, the transposed trajectory track_att(k) satisfies:

[0035] real_att is the current frame angle, k is the control cycle count, step is the step size, and sign is the sign function.

[0036] In conjunction with the first aspect, in some implementations of the first aspect, the step function `step` satisfies: a represents the step size change rate, b represents the peak step size increase, and c represents the step size deceleration threshold.

[0037] This facilitates acceleration and deceleration with a positive step size, enabling the four-axis inertial platform to achieve stable positive alignment.

[0038] In a second aspect, an electronic device is provided for performing the method as described in any of the implementations of the first aspect above. Attached Figure Description

[0039] Figure 1 This is a schematic structural diagram of a four-axis inertial platform provided in an embodiment of this application.

[0040] Figure 2A schematic flowchart of a method for aligning a four-axis inertial platform according to an embodiment of this application is shown.

[0041] Figure 3 A schematic flowchart of a method for aligning a four-axis inertial platform according to an embodiment of this application is shown. Detailed Implementation

[0042] The present application will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0043] The coordinate system of the four-axis inertial platform is as follows: Figure 1 As shown. The X'F axis is the follower axis, the YF axis is the outer ring axis, the XF axis is the inner ring axis, and the ZF axis is the platform axis. OXYZ is the gravitational inertial coordinate system of the launch point; OX P Y P Z P Let X be the platform's body coordinate system; b Y b Z b Let OX' be the base coordinate system. F Y F Z F Let θ be the platform's main frame axis. x′ For the angle of the follower ring frame, θ y For the outer ring frame angle, θ x For the inner ring frame angle, θ z The frame angle is defined as positive when rotating clockwise around the frame axis. Three quartz crystals are mounted on the stage, with their sensitive axes pointing to the X, Y, and Z directions of the stage's coordinate system, respectively. Three gyroscopes are also mounted on the stage, with their sensitive axes pointing to the X, Y, and Z directions of the stage's coordinate system, respectively.

[0044] Figure 2 This illustration shows a schematic flowchart of a method for aligning a four-axis inertial platform according to an embodiment of this application. The specific execution steps of the method for aligning a four-axis inertial platform can be found in [reference needed]. Figure 3 .

[0045] 110. Obtain the projection of the gravity vector onto the platform coordinate system of the four-axis inertial platform.

[0046] The zero-order term and installation error compensation were applied to the measurement information from the three quartz dials on the platform to obtain the gravity vector in the platform coordinate system, as follows:

[0047] The installation error of the accelerometer input shaft is defined as the positive rotation around the reference coordinate system, and the installation error angle is considered to be small enough to be approximated. This leads to the accelerometer installation error compensation algorithm:

[0048]

[0049] In the formula, This is the acceleration vector in the table coordinate system (p-frame); The actual acceleration to compensate for the accelerometer error coefficient; δ ij This represents the installation error angle of the table i around the j-axis of the platform coordinate system, in radians.

[0050] In some embodiments, the average projection of the gravity vector onto the table coordinate system over a certain time interval can be taken and normalized, as follows:

[0051] Take the average projection of the gravity vector onto the table coordinate system during the time interval τ.

[0052]

[0053] Normalization results in:

[0054]

[0055] 120. Based on the projection of the gravity vector in the platform coordinate system and the frame angle information of the four-axis inertial platform, determine the projection of the gravity vector in the base coordinate system of the four-axis inertial platform.

[0056] The transformation matrix from the frustum coordinate system to the base coordinate system is the transformation matrix for rotating the current frame angle according to the order of frustum, inner ring, outer ring, and follower ring frame angles until the frame angle is zero, as detailed below:

[0057]

[0058] Define the frame angle as positive when it rotates clockwise, thus having

[0059]

[0060]

[0061] Before the platform is calibrated, the projection of the gravity vector onto the table coordinate system is: The angles of the platform, inner ring, outer ring, and follower ring frame are θ. z1 θ x1 θ y1 θ x'1 The rotation matrix from the platform coordinate system to the base coordinate system is: Then we have: This represents the projection of the gravity vector onto the base coordinate system.

[0062] 130. Based on the projection of the gravity vector onto the base coordinate system, determine the target frame angle for platform orthogonalization.

[0063] This allows us to obtain the frame angle value when the Y-axis of the platform system points upwards. The details are as follows:

[0064] The projection of the gravity vector onto the base coordinate system is defined as: After the platform is calibrated, the projection of the gravity vector onto the platform coordinate system is: The angles of the platform, inner ring, outer ring, and follower ring frame are θ. z2 θ x2 θ y2 θ x'2 The rotation matrix from the platform coordinate system to the base coordinate system is: Then we have: This ensures that the platform is aligned, guaranteeing that the Y-axis points upwards.

[0065] To ensure the uniqueness of the solution, in practice, the inner and outer ring frame angles can always be controlled to be zero, i.e., θ x2 =0; θ y2 =0, only the platform and the two follower frame angles need to be rotated. Therefore:

[0066]

[0067] Therefore:

[0068]

[0069] Where θ z2 The value range is (-π / 2, π / 2], θ x′2 The range of values ​​is (-π, π).

[0070] 140. Based on the target frame angle, generate the rotation trajectory of the four-axis inertial platform.

[0071] After receiving the calibration command, the platform stability control software reads the target frame angle (denoted as goal_att) and the current frame angle (denoted as real_att), generates the rotation trajectory (denoted as track_att(k)), and rotates the frame to track the generated frame angle trajectory.

[0072] The platform framework's trajectory generation cycle and trajectory control cycle are consistent, and the specific trajectory is shown in the following formula:

[0073]

[0074] Where k is the control cycle count, sign is the sign function, and we have

[0075]

[0076] step is the step size, and has

[0077]

[0078] a represents the rate of change of step size. b represents the peak value of step size increase. c represents the step size deceleration threshold. <b, k' represents the minimum value of k when step(k) = b. goal-_attt>c / 2.

[0079] When initially selecting the rotating frame, the step size can be relatively small. The step size can be controlled to increase slowly using step(k) = step(k-1) + a. Once the step size reaches a certain level, it can be maintained at b. When the frame is about to rotate to the target frame angle, the step size can be controlled to decrease slowly using step(k) = step(k-1) - a. In some embodiments, a = 0.000003, b = 0.003, and c = 1.5.

[0080] When the platform stability control software executes the alignment function, it rotates sequentially in the order of platform body (Z), inner ring (X), outer ring (Y), and follower (X'). When each frame angle rotates to within a certain angle of the target frame angle, the alignment control operation for the next frame is added, until all four axes have completed alignment frame axis control. When the deviations of all four frame angles from their corresponding target frame angles are within a certain angle, the platform is considered aligned correctly, and the "aligned" status is set.

[0081] This application also provides an electronic device for performing, for example... Figure 2 The method for aligning the quadcopter platform shown is illustrated. In some embodiments, the electronic device may include... Figure 1 The four-axis inertial platform shown.

[0082] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims of the present invention.

Claims

1. A method for calibrating a four-axis inertial platform, characterized in that, include: Obtain the projection of the gravity vector onto the table coordinate system of the four-axis inertial platform; Based on the projection of the gravity vector in the platform coordinate system and the frame angle information of the four-axis inertial platform, the projection of the gravity vector in the base coordinate system of the four-axis inertial platform is determined. The target frame angle for platform orthogonalization is determined based on the projection of the gravity vector onto the base coordinate system. Based on the target frame angle, the rotation trajectory of the four-axis inertial platform is generated; The transposition trajectory track_att(k) satisfies: ， For the current frame angle, To control the cycle count, For symbolic functions: Step function satisfy: Indicates the rate of change of step size. Indicates the peak value of step size growth. This indicates the step size deceleration threshold.

2. The method according to claim 1, characterized in that, The projection of the gravity vector onto the platform coordinate system of the four-axis inertial platform satisfies: ， This is the projection vector of the gravity vector onto the table's coordinate system. To compensate for the actual acceleration due to the accelerometer error coefficient; The angle represents the installation error angle of accelerometer i about the j-axis of the platform coordinate system, in radians.

3. The method according to claim 2, characterized in that, The projection of the gravity vector onto the platform coordinate system of the four-axis inertial platform satisfies: , τ represents the time interval.

4. The method according to any one of claims 1 to 3, characterized in that, The frame angle information of the quadcopter inertial platform satisfies: ， ， For the angle of the follower ring frame, For the outer ring frame angle, For the inner ring frame corner, For the corner of the platform frame.

5. The method according to claim 4, characterized in that, The projection of the gravity vector into the base coordinate system of the quadaxial inertial platform satisfy: , This represents the rotation matrix from the platform coordinate system to the base coordinate system, as described before the platform is positive. This indicates the projection of the gravity vector, as described before the platform is aligned, onto the platform's coordinate system.

6. The method according to claim 4, characterized in that, The rotation matrix from the platform coordinate system to the base coordinate system after the platform is calibrated. satisfy: , This represents the projection of the gravity vector onto the platform coordinate system after the platform is aligned.

7. The method according to claim 4, characterized in that, After the platform is corrected, the platform frame angle ; After the platform is calibrated, the following ring frame angle ; After the platform is calibrated, the inner ring frame angle ; After the platform is corrected, the outer ring frame angle , in, .

8. An electronic device, characterized in that, The electronic device is used to perform the method as described in any one of claims 1 to 7.

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