A method for calibrating and compensating for gain variation in the servo loop of a three-axis stabilized platform

Abstract

This invention discloses a method for calibrating and compensating for the gain variation of the servo loop in a three-axis stabilized platform. First, the platform axis, inner frame axis, and outer frame axis are positioned at 0°, 0°, and 0° respectively. The servo loop is closed, and an external testing device inputs a sine wave to acquire the output signal of the three-axis stabilized platform. The amplitudes of the input and output signals at different frequencies are calculated to obtain the open-loop amplitude-frequency characteristic curve of the three-axis stabilized platform at its current position. Second, the inner frame axis is rotated 10° each time, and the gain variation of the servo loop at different angles is calculated. Finally, using the above calibration data, a function relating the inner frame axis angle to the gain variation is fitted and used to compensate for the gain of the outer frame axis servo loop. This invention provides, for the first time, a method for calibrating and compensating for the gain variation of the servo loop in a three-axis stabilized platform under uncertain rotational inertia, ensuring the stability of the servo loop in the platform frame system at any position of the inner frame.

Description

Technical Field

[0001] This invention relates to a method for calibrating and compensating for gain variation in the servo loop of a three-axis stabilized platform, belonging to the field of inertial navigation. Background Technology

[0002] With the increasing demand for maneuvering and trajectory-changing flight from carriers, inertial navigation systems are required to achieve precise navigation and guidance under conditions of high maneuvering and high dynamics. When a carrier is to perform high maneuvering and trajectory-changing flight, the inner frame axis of the three-axis stabilized platform will experience large attitude angles. Under such conditions, the platform's servo loops must still maintain sufficient stability margin and reliability.

[0003] Because the three-axis stabilization platform uses a frame structure, changes in the frame's position will cause changes in its moment of inertia, leading to changes in the gain of the platform's servo loop and consequently affecting the servo loop's amplitude stability margin. However, measuring the moment of inertia has limitations. For a single-axis frame, both the torsion method and the single-line method can only measure the moment of inertia in the direction of the rotation axis, not in the direction without a rotation axis. Simulation values ​​are also not accurate; when the mass distribution on the platform's frame structure is uneven or the frame itself is irregular, the simulation values ​​deviate significantly.

[0004] Currently, to minimize gain changes caused by alterations in rotational inertia, the three-axis stabilization platform primarily operates within a ±45° range of the inner frame. Changes in rotational inertia caused by small angles of the inner frame remain within a controllable range. However, compensation based on the mechanical model relies on the accuracy of both the model and the rotational inertia, leading to potential inaccuracies. Therefore, existing measures, when the carrier exhibits large maneuvers, cause changes in the stability margin of the servo loop due to altered rotational inertia, resulting in unstable open-loop frequency characteristics when the inner frame operates at different angles. Summary of the Invention

[0005] The technical problem solved by this invention is to overcome the shortcomings of the prior art and provide a method for calibrating and compensating for the gain variation value of the servo loop of a three-axis stabilization platform. This method can effectively improve the stability and reliability of the carrier under large-scale maneuvering conditions when the inner frame axis is working at a large angle.

[0006] The technical solution of this invention is:

[0007] A method for calibrating and compensating for gain variation in the servo loop of a three-axis stabilized platform, comprising the following steps:

[0008] (1) Position the three-axis stabilizing platform body axis, inner frame axis and outer frame axis at 0°, 0° and 0° respectively;

[0009] (2) Close the servo loop, input a sine wave to the three-axis stabilization platform from the external test equipment, and simultaneously collect the output signal of the three-axis stabilization platform. Use the least squares method to identify the frequency response of the sine wave, calculate the amplitude of the input signal and the output signal at different frequencies, and obtain the open-loop amplitude-frequency characteristic curve of the three-axis stabilization platform at the current position.

[0010] (3) Each time, increase the inner frame axis by 10°, while keeping the other two axes at 0°. Repeat step (2) until the inner frame axis rotates to 70°.

[0011] (4) The gain variation of the servo circuit of the inner frame shaft at different angles is calculated by using the open-loop amplitude-frequency characteristic curve of the inner frame shaft in the 0° to 70° orientation.

[0012] (5) The fitting function between the inner frame axis angle and the gain change value is obtained by using the second-order polynomial data fitting method, and the function is compensated into the servo loop.

[0013] Preferably, in step (2), the open-loop amplitude-frequency response curve is obtained by the following method:

[0014] An external test device generates a sinusoidal input signal Uin, which is output to the servo circuit via a digital serial port. The servo circuit adds the sinusoidal input signal Uin to the control output signal Uctl to obtain the output signal Uout = Uctl + Uin, which is then sent to the external test device via a digital serial port. The external test device uses the least squares identification method to calculate the open-loop amplitude-frequency response curve of Uout / Uin.

[0015] Preferably, in step (4), the gain variation of the servo loop at different angles of the inner frame axis is obtained by the following method:

[0016] When the position of the inner frame axis of the three-axis stabilization platform changes, causing a change in the gain value of the servo loop, the open-loop cutoff frequency will shift linearly. Taking the open-loop amplitude-frequency response curve of the inner frame axis at 0° as a reference, let the cutoff frequency at this time be ω. c When the inner frame axis is 0°, the frequency is ω. c The amplitude is 0dB; when the inner frame shaft rotates to 10°, the frequency is ω. c The corresponding amplitude is h1dB; when the inner frame rotates to 20°, the frequency is ω. c The corresponding amplitude is h2 dB; the following data were obtained from the tests:

[0017] Inner frame axis angle 0° 10° 20° 30° 40° 50° 60° 70° <![CDATA[ω c Amplitude at time]]> <![CDATA[h0]]> <![CDATA[h1]]> <![CDATA[h2]]> <![CDATA[h3]]> <![CDATA[h4]]> <![CDATA[h5]]> <![CDATA[h6]]> <![CDATA[h7]]>

[0018] The gain compensation value K is calculated using the following formula. i :

[0019] Ki =10 (-hi / 20)

[0020] Right now:

[0021] Inner frame axis angle 0° 10° 20° 30° 40° 50° 60° 70° Gain compensation value <![CDATA[K0]]> <![CDATA[K1]]> <![CDATA[K2]]> <![CDATA[K3]]> <![CDATA[K4]]> <![CDATA[K5]]> <![CDATA[K6]]> <![CDATA[K7]]> .

[0022] Preferably, in step (5), the fitting function between the inner frame axis angle and the gain change value is obtained by the following method:

[0023] With the inner frame axis angle β yk The independent variable is the change in gain K. i As the dependent variable, a second-order polynomial fitting function K is used. i =p0×β yk 2 (i)+p1×β yk (i)+p2, K i and the corresponding β yk (i) Substitute them into the fitting function to calculate the values ​​of p0, p1, and p2, and finally obtain the fitting function between the inner frame axis angle and the gain change value.

[0024] Preferably, the inner frame axial angle β yk Let β be the angle by which the outer frame rotates about the axis of the inner frame. xk Let β be the angle of rotation of the base around the outer frame axis, and β be the angle of the platform axis. zk The angle at which the inner frame rotates around the axis of the platform is denoted as .

[0025] Preferably, the inner frame axis angle β yk , outer frame axis angle β xk , platform axis angle β zk The measurement method is as follows:

[0026] An angle sensor is installed on the outer frame shaft to measure the angle β of the base rotating around the outer frame shaft. xk An angle sensor is installed on the inner frame shaft to measure the angle β of the outer frame's rotation around the inner frame shaft. yk A sensor is installed on the axis of the platform to measure the angle β of the inner frame's rotation around the axis of the platform. zk .

[0027] The advantages of this invention compared to the prior art are as follows:

[0028] (1) The present invention provides a method for calibrating and compensating the gain variation of a three-axis stabilized platform servo loop, which can compensate for the gain variation of the inner frame axis at any angle, especially when the inner frame is at a large angle, thereby increasing the stability and reliability of the carrier's high-maneuver flight.

[0029] (2) The present invention provides a method for calibrating and compensating the gain change value of a three-axis stabilized platform servo loop. Compared with other gain compensation methods, it can more accurately compensate for the gain change value caused by unknown mechanisms. Attached Figure Description

[0030] Figure 1 This is a flowchart of a method for calibrating and compensating for gain variation in a servo loop of a three-axis stabilized platform according to the present invention.

[0031] Figure 2 This is a schematic diagram of the curves showing the changes in the inner frame angle and the outer frame servo loop gain obtained from the test calibration of this invention.

[0032] Figure 3 The amplitude-frequency response curve of the uncompensated servo loop;

[0033] Figure 4 This is the amplitude-frequency response curve of the servo loop after calibration and compensation according to the present invention. Detailed Implementation

[0034] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments:

[0035] The present invention discloses a method for calibrating and compensating for the gain variation of a three-axis stabilization platform servo loop under uncertain rotational inertia. This method calculates the gain variation of the servo loop at different angles of the inner frame axis by calibrating the amplitude-frequency characteristics of the platform servo loop. Using the calibration data from the tests, a mathematical function is fitted between the inner frame axis angle and the gain variation of the outer frame servo loop. This function is then used to compensate for the gain of the outer frame servo loop under uncertain rotational inertia, thereby improving the stability and reliability of the platform servo loop.

[0036] The experimental process flowchart of the method of the present invention is as follows: Figure 1 As shown, the specific steps are as follows:

[0037] 1. Set the platform axis, inner frame axis and outer frame axis of the three-axis stabilization platform to the 0°, 0° and 0° positions respectively.

[0038] 2. Close the servo loop, input a sine wave to the three-axis stabilization platform from the external test equipment, and simultaneously acquire the output signal of the three-axis stabilization platform. Use the least squares method to identify the frequency response of the sine wave, calculate the amplitude of the input signal and the output signal at different frequencies, and obtain the open-loop amplitude-frequency characteristic curve of the three-axis stabilization platform at the current position.

[0039] An external test device generates a sinusoidal input signal Uin, which is output to the servo circuit via a digital serial port. The servo circuit adds the sinusoidal input signal Uin to the control output signal Uctl to obtain the output signal Uout = Uctl + Uin, which is then sent to the external test device via a digital serial port. The external test device uses the least squares identification method to calculate the open-loop amplitude-frequency response curve of Uout / Uin.

[0040] 3. Each time, increase the inner frame axis by 10°, while keeping the other two axes at 0°. Repeat step 2 above until the inner frame axis rotates to 70°.

[0041] Inner frame axis angle β yk , outer frame axis angle β xk , platform axis angle β zk The measurement method is as follows:

[0042] An angle sensor is installed on the outer frame shaft to measure the angle β of the base rotating around the outer frame shaft. xk An angle sensor is installed on the inner frame shaft to measure the angle β of the outer frame's rotation around the inner frame shaft. yk A sensor is installed on the axis of the platform to measure the angle β of the inner frame's rotation around the axis of the platform. zk .

[0043] 4. By using the open-loop amplitude-frequency response curves of the inner frame shaft in the 0° to 70° orientation, the gain variation of the servo circuit at different angles of the inner frame shaft is calculated.

[0044] When the position of the inner frame axis of the three-axis stabilization platform changes, causing a change in the gain value of the servo loop, the open-loop cutoff frequency will shift linearly. Taking the open-loop amplitude-frequency response curve of the inner frame axis at 0° as a reference, let the cutoff frequency at this time be ω. c When the inner frame axis is 0°, the frequency is ω. c The amplitude is 0dB; when the inner frame shaft rotates to 10°, the frequency is ω. c The corresponding amplitude is h1dB; when the inner frame rotates to 20°, the frequency is ω. c The corresponding amplitude is h2 dB; the following data were obtained from the tests:

[0045] Inner frame axis angle 0° 10° 20° 30° 40° 50° 60° 70° <![CDATA[ω c Amplitude at time]]> <![CDATA[h0]]> <![CDATA[h1]]> <![CDATA[h2]]> <![CDATA[h3]]> <![CDATA[h4]]> <![CDATA[h5]]> <![CDATA[h6]]> <![CDATA[h7]]>

[0046] The gain compensation value K is calculated using the following formula. i :

[0047] K i =10 (-hi / 20)

[0048] Right now:

[0049]

[0050] 5. A second-order polynomial data fitting method is used to obtain the fitting function between the inner frame axis angle and the change value of the outer frame servo loop gain, and the calibrated function is used to compensate the servo loop.

[0051] With the inner frame axis angle β yk With K as the independent variable and the change in gain K as the dependent variable, a second-order polynomial fitting function K is used. i =p0×β yk 2 (i)+p1×β yk (i)+p2, K i and the corresponding β yk (i) Substitute them into the fitting function to calculate the values ​​of p0, p1, and p2, and finally obtain the fitting function between the inner frame axis angle and the gain change value.

[0052] Figure 2 This is a schematic diagram of the curves showing the changes in the inner frame axis angle and the outer frame servo loop gain obtained from the test calibration of this invention. Using the open-loop amplitude-frequency response curve of the inner frame axis at 0° as a reference, the cutoff frequency at 0° of the inner frame axis is denoted as ω. c The amplitude is 0dB, and the corresponding normalized gain value K0 = 1; when the inner frame shaft rotates to 10°, the cutoff frequency ω c The corresponding amplitude is h1dB, and the normalized gain relative to the inner frame axis at 0° is K1. When the inner frame axis rotates to 20°, its cutoff frequency ω c The corresponding amplitude is h2 dB, and the normalized gain value relative to the inner frame axis at 0° is K2. (β) is obtained sequentially according to the test procedure. yk (i), K i Based on the calibration data, a schematic diagram of the curves showing the relationship between the inner frame axis angle and the gain change was obtained.

[0053] Figure 3 This is the amplitude-frequency response curve of the uncompensated servo loop. The three-axis frame-type stabilization platform is not a spherical design, and the moment of inertia of the frame structure changes when it rotates around different axes. As the inner frame axis changes from 0° to 70°, the cutoff frequency of the outer frame axis shifts from around 25Hz to around 50Hz, and the corresponding amplitude margin also decreases, affecting the stability of the control system.

[0054] Figure 4This is the open-loop amplitude-frequency characteristic curve of the servo loop after calibration and compensation according to the present invention. The calibration method allows for precise testing of the gain change of the outer frame control loop at different angles of the inner frame shaft, without relying on known parameters such as moment of inertia. The calibration results are used to fit data to obtain a precise fitting function between the inner frame shaft angle and the gain change value of the outer frame servo loop. As the inner frame shaft angle changes from 0° to 70°, the cutoff frequency of the outer frame shaft remains consistently around 25Hz, accurately compensating for the amplitude-frequency characteristic change of the outer frame servo loop caused by the change in moment of inertia, thus improving the stability and reliability of the control system.

[0055] The above test results can verify the correctness and rationality of the calibrating and compensation method for the gain variation value of the servo loop of the three-axis stabilization platform of the present invention.

[0056] The above description is only one specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the protection scope of the present invention.

[0057] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A method for calibrating and compensating for gain variation in a servo loop of a three-axis stabilized platform, characterized in that, The steps are as follows: (1) Position the three-axis stabilizing platform body axis, inner frame axis and outer frame axis at 0°, 0° and 0° respectively; (2) Close the servo loop, input a sine wave to the three-axis stabilization platform from the external test equipment, and simultaneously collect the output signal of the three-axis stabilization platform. Use the least squares method to identify the frequency response of the sine wave, calculate the amplitude of the input signal and the output signal at different frequencies, and obtain the open-loop amplitude-frequency characteristic curve of the three-axis stabilization platform at the current position. (3) Each time, increase the inner frame axis by 10°, while keeping the other two axes at 0°. Repeat step (2) until the inner frame axis rotates to 70°. (4) The gain variation of the servo circuit of the inner frame shaft at different angles is calculated by using the open-loop amplitude-frequency characteristic curve of the inner frame shaft in the 0° to 70° orientation. (5) The fitting function between the inner frame axis angle and the gain change value is obtained by using the second-order polynomial data fitting method, and the function is compensated into the servo loop.

2. The method for calibrating and compensating for gain variation in a servo loop of a three-axis stabilized platform according to claim 1, characterized in that: In step (2), the open-loop amplitude-frequency response curve is obtained by the following method: An external test device generates a sinusoidal input signal Uin, which is output to the servo circuit via a digital serial port. The servo circuit adds the sinusoidal input signal Uin to the control output signal Uctl to obtain the output signal Uout = Uctl + Uin, which is then sent to the external test device via a digital serial port. The external test device uses the least squares identification method to calculate the open-loop amplitude-frequency response curve of Uout / Uin.

3. The method for calibrating and compensating for gain variation in a servo loop of a three-axis stabilized platform according to claim 1, characterized in that: In step (4), the gain variation of the servo loop at different angles of the inner frame axis is obtained by the following method: When the position of the inner frame axis of the three-axis stabilization platform changes, causing a change in the gain value of the servo loop, the open-loop cutoff frequency will shift linearly. Taking the open-loop amplitude-frequency response curve of the inner frame axis at 0° as a reference, let the cutoff frequency at this time be ω. c When the inner frame axis is 0°, the frequency is ω. c The amplitude is 0dB; when the inner frame shaft rotates to 10°, the frequency is ω. c The corresponding amplitude is h1dB; when the inner frame rotates to 20°, the frequency is ω. c The corresponding amplitude is h2 dB; the following data were obtained from the tests: The gain compensation value K is calculated using the following formula. i : K i ＝10 (-hi / 20) Right now: 。 4. The method for calibrating and compensating for gain variation in a servo loop of a three-axis stabilized platform according to claim 1, characterized in that: In step (5), the fitting function between the inner frame axis angle and the gain change value is obtained by the following method: With the inner frame axis angle β yk The independent variable is the change in gain K. i As the dependent variable, a second-order polynomial fitting function K is used. i =p0×β yk 2 (i)+p1×β yk (i)+p2, K i and the corresponding β yk (i) Substitute them into the fitting function to calculate the values ​​of p0, p1, and p2, and finally obtain the fitting function between the inner frame axis angle and the gain change value.

5. The method for calibrating and compensating for gain variation in a servo loop of a three-axis stabilized platform according to claim 4, characterized in that: The inner frame axis angle β yk Let β be the angle by which the outer frame rotates about the axis of the inner frame. xk Let β be the angle of rotation of the base around the outer frame axis, and β be the angle of the platform axis. zk The angle at which the inner frame rotates around the axis of the platform is denoted as .

6. The method for calibrating and compensating for gain variation in a servo loop of a three-axis stabilized platform according to claim 5, characterized in that: Inner frame axis angle β yk , outer frame axis angle β xk , platform axis angle β zk The measurement method is as follows: An angle sensor is installed on the outer frame shaft to measure the angle β of the base rotating around the outer frame shaft. xk An angle sensor is installed on the inner frame shaft to measure the angle β of the outer frame's rotation around the inner frame shaft. yk A sensor is installed on the axis of the platform to measure the angle β of the inner frame's rotation around the axis of the platform. zk .

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