A method for calibrating optical platform image axis and gyro axis

Abstract

This invention relates to the field of automatic control, and more particularly to a calibration method for the image axis and gyroscope axis of an optoelectronic platform. The method includes: mounting an optoelectronic seeker on a three-dimensional turntable and establishing target tracking; controlling the roll, pitch, and yaw channels of the three-dimensional turntable to perform sinusoidal motion at specific frequencies, simultaneously recording the line-of-sight angular velocity data output by the seeker; calculating the influence factor of each mechanical axis motion on the image axis through spectral analysis of the angular velocity data; finally, constructing a compensation matrix using the influence factor to correct the original gyroscope feedback angular velocity, and using the corrected angular velocity for servo control. This invention abandons the traditional method relying on high-precision machining and optical equipment calibration, achieving high-precision calibration through purely electrical and algorithmic means. It effectively eliminates line-of-sight angular velocity errors and channel coupling caused by axis non-parallelism, significantly improving system performance while greatly reducing cost and assembly complexity.

Description

Technical Field

[0001] This invention relates to the field of automatic control, and more particularly to a calibration method for the image axis and gyroscope axis of an optoelectronic platform. Background Technology

[0002] Electro-optical seekers are typically mounted on high-speed flight platforms to track targets in real time and output the line-of-sight angular velocity between the platform and the target. In practical applications, the electro-optical platform is required to effectively isolate external disturbances, accurately output the line-of-sight angular velocity, and minimize the coupling between the yaw, pitch, and roll axes.

[0003] Currently, common methods for eliminating fixed deviations between the gyroscope's three axes and the image's three axes primarily rely on precise structural design and assembly processes. Specifically, this typically involves designing high-precision mating surfaces on the mounting surfaces of the gyroscope and optical imaging module, and using a high-precision reference structure for alignment transfer. Furthermore, a high-precision turntable is required for software calibration of the gyroscope's three axes and its mounting plane, while specialized optical instruments are used for structural adjustment of the alignment between the imaging axis and the mounting surface. Finally, through structural precision transfer, the gyroscope axes and image axes are fixedly connected, and the non-parallelism between them is calibrated and corrected.

[0004] However, the above methods have many limitations in implementation. First, they require extremely high precision in structural processing, assembly technology, and debugging equipment, leading to a significant increase in product manufacturing costs and a complex and lengthy assembly and debugging process. Second, for optical systems integrating multiple types of sensors, the complexity and cost of this method will further increase, making it difficult to promote its application in practical engineering. Therefore, existing technologies are generally only applicable to some high-value, large-volume optoelectronic devices, limiting their scope of application.

[0005] To improve the axis parallelism of multi-sensor optical systems, several technical solutions for optical system axis calibration have emerged. For example, the "Outer Field Calibration of Optical Axis Parallelism in Visible and Infrared Optical Systems" proposed by Meng Qinghua et al. of the Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, uses a Cassegrain reflector collimator in conjunction with a plane mirror to achieve parallelism calibration of the optical axes of dual optical systems. This method achieves high calibration accuracy, but it only addresses the axis calibration between optical sensors and does not address the alignment between the gyroscope axis and the image axis. Another example is the "Calibration and Verification of Optical Axis in Phased Array Radar" published by Fu Qiang et al. of the Xi'an Institute of Electronic Engineering, which focuses on solving the calibration problem between the optical axis and mechanical axis of a phased array antenna telescope. Its approach is more applicable to radar systems and does not address the calibration between the optical image axis and the gyroscope axis.

[0006] In summary, existing technologies for achieving high-precision calibration between the gyroscope axis and the image axis still suffer from problems such as complex processes, high equipment requirements, and poor engineering applicability. Therefore, there is an urgent need to propose a new calibration method that can achieve high-precision alignment between the gyroscope axis and the image axis using only the tracking function of the optoelectronic platform and conventional experimental equipment, without requiring complex processes or precision optical equipment. This method effectively compensates for line-of-sight angular velocity output errors and channel coupling caused by axis non-parallelism, thereby improving the overall system performance. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention proposes a calibration method for the image axis and gyroscope axis of an optoelectronic platform. This method does not rely on precision optical equipment and achieves high-precision calibration through algorithm compensation, significantly reducing cost and complexity.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] This invention proposes a calibration method for the image axis and gyroscope axis of an optoelectronic platform, comprising the following steps:

[0010] S1. Install the photoelectric guide head on the three-dimensional turntable and control it to enter the tracking state of the target simulator;

[0011] S2. Control the three-dimensional turntable to perform a number of sinusoidal oscillating movements in the first motion channel, and record the line-of-sight angular velocity sequence X1 and the line-of-sight angular velocity sequence X2 of the second motion channel output by the photoelectric guide head in each movement; calculate the inter-axis coupling influence factor K1 of the first motion channel to the second motion channel and the inter-axis coupling influence factor K2 of the first motion channel to the third motion channel through X1 and X2 respectively.

[0012] S3. Control the three-dimensional turntable to perform a number of sinusoidal swinging movements in the second motion channel, and record the line-of-sight angular velocity sequence X3 of the third motion channel output by the photoelectric guide head in each movement; calculate the inter-axis coupling influence factor K3 of the second motion channel to the third motion channel through X3.

[0013] S4. Control the three-dimensional turntable to perform a number of sinusoidal swinging movements in the third motion channel, and record the line-of-sight angular velocity sequence X4 of the second motion channel output by the photoelectric guide head for each movement; calculate the inter-axis coupling influence factor K4 of the third motion channel on the second motion channel through X4.

[0014] S5. Based on K1, K2, K3 and K4, correct the gyroscope feedback to complete the calibration of the image axis and the gyroscope axis.

[0015] Furthermore, the first motion channel, the second motion channel, and the third motion channel are respectively the roll channel, the yaw channel, and the pitch channel.

[0016] Furthermore, in S2, the calculation process of K1 is as follows: calculate the interaxial coupling influence factor of each first motion channel swing on the second motion channel; then take the average value of all the first motion channel swings on the second motion channel to obtain K1;

[0017] The calculation process for the inter-axis coupling influence factor of each oscillation of the first motion channel on the second motion channel is as follows:

[0018] S201. Calculate the arithmetic mean X1. 1mean Subtract X from each term in X1 1mean This yields the sequence X1';

[0019] S202. Calculate the frequency value sequence f corresponding to X1; and perform FFT fast Fourier transform on X1' to obtain the amplitude sequence a corresponding to X1.

[0020] S203. After finding the term f[m] in f that is closest to the swing frequency, find the term a[m] corresponding to f[m] in a;

[0021] S204. Calculate the inter-axis coupling influence factor of the first motion channel on the second motion channel using a[m] and the amplitude of the swing.

[0022] Furthermore, in S202, the calculation process for the amplitude sequence a and the frequency sequence f is as follows:

[0023]

[0024] In the formula, For the k-th term of a, For the k-th term of f, for The kth item.

[0025] Furthermore, the calculation process for K1, K2, K3, and K4 in S2 is the same.

[0026] Furthermore, the number of swings in the first motion channel in S2, the number of swings in the second motion channel in S3, and the number of swings in the third motion channel in S4 are all greater than or equal to 3.

[0027] Furthermore, the frequency and amplitude of the corresponding swings in the first, second, and third motion channels are the same.

[0028] Furthermore, the sampling frequency of the first motion channel in S2, the second motion channel in S3, and the third motion channel in S4 during each swing process is 50Hz, and the number of samples is an even number greater than or equal to 1000.

[0029] Furthermore, the step of correcting the gyroscope feedback is achieved through the following formula:

[0030]

[0031] In the formula, and GYRO-EL, GYRO-AZ, and GYRO-RL represent the corrected pitch and yaw gyroscope feedback values, respectively, while GYRO-EL, GYRO-AZ, and GYRO-RL represent the uncorrected pitch, yaw, and roll gyroscope feedback values, respectively.

[0032] Furthermore, the step of mounting the photoelectric seeker on the three-dimensional turntable includes: positioning the photoelectric seeker at the center of the three-dimensional turntable by means of mechanical holes, and making the axis of the three-dimensional turntable parallel to the yaw axis and pitch axis of the photoelectric seeker when it is in the zero position.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] (1) Existing technologies rely on high-precision machining, complex assembly and adjustment processes, and expensive optical calibration equipment such as collimators, resulting in high production costs and long cycles, making it difficult to promote and apply in ordinary value or large-scale optoelectronic devices. This invention completely avoids these harsh physical limitations, only requiring the use of a general-purpose three-axis turntable and the product's own tracking function to achieve high-precision calibration through algorithm analysis and compensation. This greatly reduces the dependence of the calibration process on hardware processes, significantly reduces equipment costs and assembly and adjustment complexity, and makes this technical solution have strong engineering application value and wide applicability.

[0035] (2) By accurately measuring the line-of-sight angular velocity error caused by mechanical motion coupling and calculating the influencing factor in reverse, this invention can not only effectively compensate for static installation errors, but also dynamically correct the channel coupling interference caused by non-parallel shaft systems.

[0036] (3) The present invention transforms the calibration process into a series of programmable controllable steps, which is easy to automate. This not only improves calibration efficiency and shortens calibration time, but also reduces the manual intervention and subjective judgment required in traditional optical calibration, effectively avoiding errors introduced by differences in operator experience, thereby ensuring the consistency and reliability of calibration results.

[0037] (4) This invention reduces the output error of line-of-sight angular velocity from the source by compensating for the non-parallelism between the gyroscope axis and the image axis with high precision, and significantly reduces the coupling coefficient between servo control channels, making the photoelectric platform imaging more stable, tracking more accurate, and output target information of higher quality. Attached Figure Description

[0038] Figure 1This is a block diagram of the control system of the optoelectronic platform in an embodiment of the present invention;

[0039] Figure 2 This is a schematic diagram of the shaft system calibration experiment setup according to an embodiment of the present invention.

[0040] Reference numerals: 1. 3D turntable; 2. Photoelectric seeker; 3. Target simulator. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] Example

[0043] This embodiment proposes a calibration method for the image axis and gyroscope axis of an optoelectronic platform. The control system framework of the optoelectronic platform is as follows: Figure 1 As shown, the optoelectronic platform includes a gimbal structure, a servo control unit, and an optoelectronic seeker head mounted on it. The optoelectronic seeker head integrates an optical sensor (such as a visible light or infrared camera) and a three-axis gyroscope. The hardware of the servo control unit specifically includes a three-axis gyroscope, an angle measuring element (such as a rotary transformer or encoder), and a drive motor; the software includes a current loop, a speed stabilization loop, and a position control loop. The optical sensor transmits the target miss distance signal to the servo control unit; the gyroscope feeds back the angular velocity signal to the servo control unit; after processing by the control algorithm, the servo control unit outputs drive commands to the torque motor of the gimbal, forming a complete closed-loop control system.

[0044] The calibration method proposed in this embodiment is performed according to the following steps:

[0045] S1, Reference Figure 2 The photoelectric seeker 2 is fixed to the center of the 3D turntable 1 using a clamp. Mechanical holes are used for positioning to ensure the axis of the 3D turntable 1 is parallel to the yaw and pitch axes of the photoelectric seeker 2 when it is in the zero position. The target simulator 3 is placed directly in front of the 3D turntable 1. In this embodiment, the target simulator 3 is a collimator. The target simulator 3 is positioned approximately 5 meters in front of the 3D turntable, and its mounting plane is finely adjusted to ensure it is parallel to the base plane of the 3D turntable 1. The photoelectric seeker 2 is powered on, and the target simulator 3 is moved parallel to the center of the optical sensor's field of view using its control software to make the simulated target point appear in the center of the optical sensor's field of view. Subsequently, the operator moves the image crosshairs through the control interface to precisely lock and stably track the target point. At this time, the photoelectric seeker 2 should be working stably in automatic tracking mode.

[0046] S2. Using the 3D turntable control software, the 3D turntable 1 performs several sinusoidal oscillating movements in the first motion channel. Record the line-of-sight angular velocity series X1 and X2 of the second and third motion channels output by the photoelectric seeker 2 for each movement. Calculate the inter-axis coupling influence factors K1 and K2 of the first and third motion channels from X1 and X2, respectively. In this embodiment, the first motion channel is a roll channel; the second motion channel is a pitch channel; and the third motion channel is a yaw channel.

[0047] In this step, the three-dimensional turntable 1 performs three sinusoidal oscillating motions in the roll path, with the frequencies and amplitudes of the three oscillations being respectively... , , During each swing, sampling begins after the 3D turntable 1 stabilizes. The sampling frequency is... ,sampling .

[0048] The calculation process for K1 is as follows: calculate the interaxial coupling influence factor of each first motion channel swing on the second motion channel; then take the average value of all the first motion channel swing influence factors on the second motion channel to obtain K1.

[0049] The inter-axis coupling influence factor of each oscillation of the first motion channel on the second motion channel is calculated using X1 obtained in that instance. The calculation process is as follows:

[0050] S201: Calculate the arithmetic mean X1. mean Subtract X from each term in X1 mean We obtain the sequence X1':

[0051]

[0052]

[0053] S202: Calculate the frequency sequence f corresponding to X1; and... Perform an FFT (Fast Fourier Transform) to obtain the magnitude sequence a corresponding to X1;

[0054]

[0055] In the formula, For the k-th term of a, For the k-th term of f, for The kth item.

[0056] S203. After finding the term f[m] in f that is closest to the swing frequency, find the term a[m] corresponding to f[m] in a;

[0057] S204. Calculate the interaxial coupling influence factor of the first motion channel to the second motion channel using a[m] and the amplitude of the swing. The interaxial coupling influence factor of the first motion channel to the second motion channel is the ratio of a[m] to the amplitude of the swing. For example, if the swing is the first one, then the interaxial coupling influence factor of the first motion channel to the second motion channel is a[m] / A1.

[0058] In this embodiment, K1= K11 represents the interaxial coupling influence factor of the first oscillation of the first motion channel on the second motion channel in this step; K12 represents the interaxial coupling influence factor of the second oscillation of the first motion channel on the second motion channel in this step; and K13 represents the interaxial coupling influence factor of the third oscillation of the first motion channel on the second motion channel in this step.

[0059] The calculation method for K2 is the same as that for K1. The inter-axis coupling influence factor of the first motion channel swing on the second motion channel is calculated by X2 obtained in that cycle.

[0060] K2=

[0061] K21 represents the interaxial coupling influence factor of the first oscillation of the first motion channel on the third motion channel in this step; K22 represents the interaxial coupling influence factor of the second oscillation of the first motion channel on the third motion channel in this step; and K23 represents the interaxial coupling influence factor of the third oscillation of the first motion channel on the third motion channel in this step.

[0062] S3. Control the three-dimensional turntable 1 to perform three sinusoidal oscillations in the second motion channel, and record the line-of-sight angular velocity sequence X3 output by the photoelectric guide head 2 in the third motion channel for each motion; calculate the inter-axis coupling influence factor K3 of the second motion channel to the third motion channel through X3; the frequency and amplitude of the three-dimensional turntable 1's three oscillations in the second motion channel are respectively , , During each swing, sampling begins after the 3D turntable 1 stabilizes. The sampling frequency is... ,sampling .

[0063] The calculation process for K3 is the same as that for K1.

[0064] K3=

[0065] K31 represents the interaxial coupling influence factor of the first oscillation of the second motion channel on the third motion channel in this step; K32 represents the interaxial coupling influence factor of the second oscillation of the second motion channel on the third motion channel in this step; and K33 represents the interaxial coupling influence factor of the third oscillation of the second motion channel on the third motion channel in this step.

[0066] S4. Control the three-dimensional turntable 1 to perform three sinusoidal oscillations in the third motion channel, and record the line-of-sight angular velocity sequence X4 of the second motion channel output by the photoelectric guide head 2 for each motion; calculate the inter-axis coupling influence factor K4 of the third motion channel on the second motion channel through X4; the frequency and amplitude of the three oscillations of the three-dimensional turntable in the third motion channel are respectively , , During each swing, sampling begins after the 3D turntable 1 stabilizes. The sampling frequency is... ,sampling .

[0067] The calculation process for K4 is the same as that for K1.

[0068] K4=

[0069] K41 represents the inter-axis coupling influence factor of the first oscillation of the third motion channel on the second motion channel in this step; K42 represents the inter-axis coupling influence factor of the second oscillation of the third motion channel on the second motion channel in this step; and K43 represents the inter-axis coupling influence factor of the third oscillation of the third motion channel on the second motion channel in this step.

[0070] S5. Based on K1, K2, K3, and K4, correct the gyroscope feedback value, and then input the corrected gyroscope feedback value into the servo control unit to complete the calibration. The corrected gyroscope feedback value is calculated according to the following formula:

[0071] ;

[0072] In the formula, This is the corrected pitch gyroscope feedback value; GYRO-EL represents the corrected yaw gyroscope feedback, GYRO-AZ represents the original pitch gyroscope feedback, and GYRO-RL represents the original roll gyroscope feedback.

[0073] In this embodiment, the calculation steps of the calibration method are executed by the servo control unit of the photoelectric seeker or a host computer connected to it. After calibration, the calculated coupling influence factors (K1, K2, K3, K4) are written into and permanently stored in the non-volatile memory of the photoelectric seeker. In subsequent normal operation, the real-time control software of the photoelectric seeker will call these parameters to compensate for the original gyroscope data, thereby continuously ensuring high-precision line-of-sight angular velocity output.

[0074] The specific embodiments of the present invention are provided to enable those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention.

[0075] It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A method for calibrating the image axis and gyroscope axis of an optoelectronic platform, characterized in that, Includes the following steps: S1. Install the photoelectric guide head on the three-dimensional turntable and control it to enter the tracking state of the target simulator; S2. Control the three-dimensional turntable to perform a number of sinusoidal oscillating movements in the first motion channel, and record the line-of-sight angular velocity sequence X1 and the line-of-sight angular velocity sequence X2 of the second motion channel output by the photoelectric guide head in each movement; calculate the inter-axis coupling influence factor K1 of the first motion channel to the second motion channel and the inter-axis coupling influence factor K2 of the first motion channel to the third motion channel through X1 and X2 respectively. S3. Control the three-dimensional turntable to perform a number of sinusoidal swinging movements in the second motion channel, and record the line-of-sight angular velocity sequence X3 of the third motion channel output by the photoelectric guide head in each movement; calculate the inter-axis coupling influence factor K3 of the second motion channel to the third motion channel through X3. S4. Control the three-dimensional turntable to perform a number of sinusoidal swinging movements in the third motion channel, and record the sequence of X4 of the line-of-sight angular velocity output by the photoelectric guide head in the second motion channel for each movement. The interaxial coupling influence factor K4 of the third motion channel on the second motion channel is calculated using X4. S5. Based on K1, K2, K3 and K4, correct the gyroscope feedback to complete the calibration of the image axis and the gyroscope axis.

2. The calibration method for the image axis and gyroscope axis of the photoelectric platform according to claim 1, characterized in that, The first motion channel, the second motion channel, and the third motion channel are the roll channel, the yaw channel, and the pitch channel, respectively.

3. The calibration method for the image axis and gyroscope axis of the photoelectric platform according to claim 1, characterized in that, In S2, the calculation process of K1 is as follows: calculate the interaxial coupling influence factor of each first motion channel swing on the second motion channel; then take the average value of all the first motion channel swing influence factors on the second motion channel to obtain K1. The calculation process for the inter-axis coupling influence factor of each oscillation of the first motion channel on the second motion channel is as follows: S201. Calculate the arithmetic mean X1. 1mean Subtract X from each term in X1 1mean This yields the sequence X1'; S202. Calculate the frequency value sequence f corresponding to X1; and perform FFT fast Fourier transform on X1' to obtain the amplitude sequence a corresponding to X1. S203. After finding the term f[m] in f that is closest to the swing frequency, find the term a[m] corresponding to f[m] in a; S204. Calculate the inter-axis coupling influence factor of the first motion channel on the second motion channel using a[m] and the amplitude of the swing.

4. The calibration method for the image axis and gyroscope axis of the photoelectric platform according to claim 3, characterized in that, In S202, the calculation process for the amplitude sequence 'a' and the frequency sequence 'f' is as follows: In the formula, For the k-th term of a, For the k-th term of f, for The kth item.

5. The calibration method for the image axis and gyroscope axis of the photoelectric platform according to claim 1, characterized in that, The calculation process for K1, K2, K3 and K4 in S2 is the same.

6. The calibration method for the image axis and gyroscope axis of the photoelectric platform according to claim 1, characterized in that, The number of swings in the first motion channel in S2, the number of swings in the second motion channel in S3, and the number of swings in the third motion channel in S4 are all greater than or equal to 3.

7. The calibration method for the image axis and gyroscope axis of the photoelectric platform according to claim 6, characterized in that, The frequency and amplitude of the corresponding swings in the first, second, and third motion channels are the same.

8. The calibration method for the image axis and gyroscope axis of the photoelectric platform according to claim 1, characterized in that, The sampling frequency of the first motion channel in S2, the second motion channel in S3, and the third motion channel in S4 during each swing process is 50Hz, and the number of samples is an even number greater than or equal to 1000.

9. The calibration method for the image axis and gyroscope axis of the photoelectric platform according to claim 1, characterized in that, The step of correcting the gyroscope feedback is achieved through the following formula: In the formula, and GYRO-EL, GYRO-AZ, and GYRO-RL represent the corrected pitch and yaw gyroscope feedback values, respectively, while GYRO-EL, GYRO-AZ, and GYRO-RL represent the uncorrected pitch, yaw, and roll gyroscope feedback values, respectively.

10. The calibration method for the image axis and gyroscope axis of the photoelectric platform according to claim 1, characterized in that, The steps of mounting the photoelectric seeker on the three-dimensional turntable include: positioning the photoelectric seeker at the center of the three-dimensional turntable by means of mechanical holes, and making the axis of the three-dimensional turntable parallel to the yaw axis and pitch axis of the photoelectric seeker when it is in the zero position.

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