Non-cooperative target trajectory prediction method fusing camera off-target amount and encoder information

Abstract

The application discloses a non-cooperative target trajectory prediction method fusing camera off-target amount and encoder information; the actual trajectory sequence of the non-cooperative target is obtained by fusing the camera off-target amount of the optical telescope and the grating encoder information; the movement trajectory of the tracking target in the blind area time is predicted by using a prediction algorithm; at the camera sampling time, the optical feedback control is directly used to control the movement of the telescope; at the encoder sampling time, the tracking error in the blind area time is obtained by subtracting the corresponding prediction value from the encoder measurement value and inputting into the telescope movement control system, so that the control frequency and the closed loop bandwidth of the telescope movement control system are improved, the error between the reference trajectory and the actual trajectory of the tracking target is reduced, and the tracking capability of the optical telescope on the non-cooperative target is improved.

Description

Technical Field

[0001] The present invention relates to the field of trajectory prediction of non-cooperative targets, and in particular to a non-cooperative target trajectory prediction method that integrates camera miss distance and encoder information. Background Art

[0002] With the development of astronomy, aerospace, and aviation, optical telescopes have become increasingly indispensable in applications such as astronomical observation, space target monitoring, and target tracking. In particular, optical telescopes play a vital role in performing complex and diverse observational missions in space exploration and national defense security. Among these, high-precision tracking of non-cooperative targets has become a key and challenging area of ​​current technological research.

[0003] Traditional optical telescopes use optical cameras for image feedback. This involves capturing an image of the target being tracked, and then using image processing algorithms to identify and calculate the pixel coordinates within the field of view. This determines the target's miss distance (i.e., the deviation between the target position and the telescope's aiming axis). This miss distance is fed as a feedback signal into the telescope's servo control system, forming a closed-loop control loop that enables precise tracking of the target.

[0004] However, traditional image feedback systems, due to their reliance on the optical camera's sampling frequency and image processing algorithms, suffer from slow response, poor real-time performance, and a tendency to lose track when tracking high-speed moving targets. This shortcoming limits traditional optical telescopes in certain tasks, particularly when tracking non-cooperative targets. Non-cooperative targets are space objects that cannot provide trajectory prediction data and lack the ability to actively cooperate, such as low-orbit satellites, drones, and space debris that lack communication and coordination. Unlike cooperative targets, trajectory prediction data for non-cooperative targets cannot be obtained in advance of the tracking mission, so tracking relies solely on image feedback from the optical telescope. When tracking fast-moving targets such as drones and low-orbit satellites, existing optical cameras suffer from low sampling frequencies, slow feedback, and even delayed response, which severely restricts the telescope's ability to track non-cooperative targets. Summary of the Invention

[0005] In view of the shortcomings of existing non-cooperative target trajectory prediction technology, the purpose of the present invention is to provide a non-cooperative target trajectory prediction method that integrates camera miss distance and encoder information. By combining two different feedback signals, the tracking trajectory of non-cooperative targets can be accurately predicted in real time, thereby improving the tracking response speed and tracking accuracy of optical telescopes for non-cooperative targets.

[0006] To achieve the above objectives, the present invention provides a non-cooperative target trajectory prediction method that integrates camera miss distance and encoder information. The method comprises the following steps:

[0007] Step 1: System initialization, including obtaining initial guidance information and initializing the telescope settings;

[0008] Step 2: At the camera sampling moment, the optical camera exposes and images the target, identifies the image, and calculates the miss distance. This is then converted into the telescope's angular position error in azimuth and elevation, which is then input into the telescope's motion control unit. Simultaneously, the encoder samples and reads the encoder's measurement value at the current moment.

[0009] In step 3, after completing an optical imaging and miss distance reading, the telescope tracks the time it enters the blind zone. The camera miss distance obtained at the camera sampling time is combined with the grating encoder information to calculate the target's actual position and update the actual trajectory sequence. Based on this actual trajectory sequence, a trajectory prediction algorithm is used to predict the motion trajectory of the non-cooperative target before the next optical imaging is completed. Interpolation is performed based on the encoder sampling time to obtain a predicted trajectory sequence.

[0010] Step 4: At the encoder sampling moment, read the grating encoder measurement value. Simultaneously read the predicted value corresponding to the current moment in the predicted trajectory sequence, subtract it from the encoder measurement value, and obtain the angular position error, which is input into the telescope motion control unit.

[0011] Step 5: Confirm whether to continue the tracking mission. If yes, repeat steps 2 to 4. If no, end the mission and turn off the telescope control system.

[0012] Furthermore, step 1 specifically includes:

[0013] Step 1.1, start the telescope motion control system and initialize the parameters. The optical telescope is equipped with an optical camera and a grating encoder, which are used to measure the target miss distance and the telescope rotation angle respectively. The sampling time of the optical camera is T c , the grating encoder sampling time is T e , the camera sampling time is an integer multiple of the encoder sampling time, that is, T c =mT e , m is a positive integer. The telescope control system sampling time T s The same as the encoder sampling time, that is, T s = T e The time between two imagings of the optical camera is called the blind time. During this time period, the system cannot obtain camera image information, but the encoder and motion control system still measure and control at the above system sampling frequency.

[0014] Step 1.2: Input the guidance information, i.e. the initial trajectory of the tracking target, and set the initial target actual trajectory sequence. The initial target actual trajectory sequence R of the system is a (0), R e(0) selects the data corresponding to the last four camera sampling moments in the above guidance information, where R a Indicates azimuth data, R e Indicates pitch angle data.

[0015] Step 1.3: The telescope motion control system controls the telescope to track the target according to the guidance information, so that the target appears in the field of view of the optical camera.

[0016] Furthermore, step 2 specifically includes:

[0017] Step 2.1: At the kth optical camera sampling moment, the camera exposes and images the tracking target, identifies the image pixels and calculates the miss distance.

[0018] Step 2.2, convert the miss distance into the angular error of the telescope in the azimuth and elevation directions. Assume that the miss distance on the horizontal axis of the imaging is Δx c , the miss distance on the vertical axis is Δy c , the camera focal length is f c , then at the kth optical camera sampling moment, that is, the kmth system sampling moment, the azimuth angle error e ca , pitch angle error e ce The calculations can be described by the following formulas:

[0019]

[0020]

[0021] The position error calculated according to the above formula is input into the telescope motion control unit.

[0022] Step 2.3, read the current grating encoder measurement value at the same time, that is, the rotation angle of the telescope in the azimuth and pitch directions, recorded as y ea (km), y ee (km).

[0023] Furthermore, step 3 specifically includes:

[0024] Step 3.1, after completing the kth optical imaging and miss distance reading, the telescope tracks the time it enters the kth blind zone. The actual position of the target is calculated by fusing the camera miss distance obtained at the camera sampling moment and the grating encoder information, as shown in the following formula:

[0025]

[0026]

[0027] Furthermore, the actual trajectory sequence is updated, i.e.

[0028]

[0029]

[0030] Step 3.2, according to the updated actual trajectory sequence R a 、R e , a polynomial fitting algorithm is used to predict the motion trajectory P of the non-cooperative target before the next optical imaging is completed a 、P e , the polynomial model is shown in the following formula

[0031]

[0032] The actual trajectory sequence R a 、R e Substitute the data points into the polynomial model to obtain the matrix equation, as shown in the following formula

[0033]

[0034] Simplified to Xa = P. The least square method is used to solve the optimal coefficient a = (X T X) -1 X T P, the polynomial model parameters a0, a1, a2, a3 are obtained, that is, the motion trajectory model is predicted according to the actual trajectory sequence.

[0035] Step 3.3, substitute the updated model parameters in step 3.2 into the polynomial model to complete the update of the prediction model. Interpolation is performed according to the encoder sampling time. Specifically, select , substitute into the updated polynomial model, and calculate the interpolated predicted trajectory sequence according to the polynomial model formula.

[0036] Furthermore, step 4 specifically includes:

[0037] Step 4.1: At the nth encoder sampling moment (n = 1, 2, …, m) in the kth blind time, read the grating encoder measurement value.

[0038] In step 4.2, the corresponding value of the interpolated predicted trajectory sequence at the current moment is subtracted from the current encoder measurement value to calculate the angular position error of the telescope during the blind time and input it into the telescope motion control unit.

[0039] Furthermore, step 5 specifically includes:

[0040] Confirm whether the tracking mission should continue. If yes, repeat steps 2 to 4. If no, end the mission and send a control command to shut down the telescope control system.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] The present invention effectively solves the problems of slow tracking speed and easy loss of tracking targets in existing optical feedback tracking technologies, improves the trajectory prediction accuracy of the telescope for non-cooperative targets during blind time, and thus significantly improves the trajectory tracking capability for non-cooperative targets. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a specific flow diagram of the present invention;

[0044] Figure 2 It is a discrete timing diagram of the present invention;

[0045] Figure 3 This is a schematic diagram of optical camera imaging and miss distance calculation;

[0046] Figure 4 It is a comparison diagram of the reference trajectories of the traditional optical feedback tracking method and the method of the present invention;

[0047] Figure 5 2 is a comparison diagram of non-cooperative target tracking effects; wherein, (a) is a non-cooperative target tracking effect diagram of the traditional optical feedback method, and (b) is a non-cooperative target tracking effect diagram of the method of the present invention. DETAILED DESCRIPTION

[0048] The specific implementation of the present invention will be described below with reference to the accompanying drawings and embodiments.

[0049] like Figures 1 to 5 As shown, the present invention provides a non-cooperative target trajectory prediction algorithm that integrates camera miss distance and grating encoder information, which specifically includes the following steps:

[0050] Step 1: System initialization, including obtaining initial guidance information and initializing the telescope settings;

[0051] Step 2: At the camera sampling moment, the optical camera exposes and images the target, identifies the image, and calculates the miss distance. This is then converted into the telescope's angular position error in azimuth and elevation, which is then input into the telescope's motion control unit. Simultaneously, the encoder samples and reads the encoder's measurement value at the current moment.

[0052] Step 3: After completing an optical imaging and miss distance reading, the telescope tracks the time it enters the blind zone. The camera miss distance obtained at the camera sampling time is combined with the grating encoder information to calculate the target's actual position and update the actual trajectory sequence. Based on this actual trajectory sequence, a polynomial fitting algorithm is used to predict the motion trajectory of the non-cooperative target before the next optical imaging. Interpolation is performed based on the encoder sampling time to obtain a predicted trajectory sequence.

[0053] Step 4: At the encoder sampling moment, read the grating encoder measurement value. Simultaneously read the predicted value corresponding to the current moment in the predicted trajectory sequence, subtract it from the encoder measurement value, and obtain the angular position error, which is input into the telescope motion control unit.

[0054] Step 5: Confirm whether the tracking mission should continue. If yes, repeat steps 2 to 4. If no, end the mission and turn off the telescope control system.

[0055] It should be noted that the optical telescope is equipped with an optical camera and a grating encoder, which are used to measure the miss distance of the tracking target and the telescope rotation angle respectively.

[0056] Figure 2 The optical camera sampling time of the present invention is T c , the sampling time of the grating encoder is T e , the camera sampling time is an integer multiple of the encoder sampling time, that is, T c = mT e , m is a positive integer. The telescope control system sampling time T s Same as encoder sampling time, that is, T s = T e The time between two imaging times of the optical camera is called the blind time. During this period, the system cannot obtain camera image information, but the encoder and motion control system still measure and control at the above-mentioned system sampling frequency. Therefore, the non-cooperative target trajectory prediction algorithm proposed in this invention, which integrates the camera miss distance and grating encoder information, can be used to calculate the actual trajectory sequence of the non-cooperative target, further predict the target motion trajectory, and interpolate the predicted trajectory during the blind time.

[0057] It should be noted that step 1 specifically includes starting the telescope motion control system and setting parameter initialization, inputting initial guidance information, and controlling the telescope to track the target so that it appears in the field of view of the optical camera. The actual trajectory sequence of the initial target in step 1 is R a (0), R e (0) selects the data corresponding to the last four camera sampling moments in the guidance information, where R a Indicates azimuth data, R e Indicates pitch angle data.

[0058] It should be noted that step 2 specifically involves, at the kth optical camera sampling moment, exposing and imaging the tracked target, identifying image pixels, and calculating the miss distance. Furthermore, the miss distance is converted into the telescope's angular errors in azimuth and elevation, which are input into the telescope motion control unit. Simultaneously, the current grating encoder measurement value is read.

[0059] Figure 3 The following is a schematic diagram of optical camera imaging and miss distance calculation. The specific implementation steps of step 2 for converting miss distance and rotation angle error are as follows: Assume that the miss distance on the horizontal axis of the imaging is Δx c , the miss distance on the vertical axis is Δy c , the focal length of the camera is f c , then at the kth optical camera sampling moment, that is, the kmth system sampling moment, the azimuth angle error e ca , pitch angle error e ce The calculations can be described by the following formulas:

[0060]

[0061]

[0062] The position error calculated according to the above formula is input into the telescope motion control unit.

[0063] It should be noted that the current grating encoder measurement value is read in step 2, that is, the rotation angle of the telescope in the azimuth and pitch directions, which are recorded as y and ea (km), y ee (km).

[0064] It should be noted that step 3 specifically involves: after completing an optical imaging and miss distance reading, the telescope tracks the time it enters the blind zone. The camera miss distance obtained at the camera sampling time is integrated with the grating encoder information to calculate the actual target position and update the actual trajectory sequence. Based on this actual trajectory sequence, a polynomial fitting algorithm is used to predict the motion trajectory of the non-cooperative target before the next optical imaging is completed. Interpolation is performed based on the encoder sampling time to obtain a predicted trajectory sequence.

[0065] It should be noted that the specific implementation of step 3 is as follows: After completing the k-th optical imaging and miss distance reading, the telescope enters the k-th blind zone time. The camera miss distance obtained at the camera sampling moment and the grating encoder information are integrated to calculate the actual position of the target, as shown in the following formula

[0066]

[0067]

[0068] Furthermore, the actual trajectory sequence is updated, i.e.

[0069]

[0070]

[0071] According to the updated actual trajectory sequence R a 、Re , a third-order polynomial fitting algorithm is used to predict the motion trajectory P of the non-cooperative target before the next optical imaging is completed a 、P e , the third-order polynomial model is shown in the following formula

[0072]

[0073] The actual trajectory sequence R a 、R e Substitute the data points into the polynomial model to obtain the matrix equation, as shown in the following formula

[0074]

[0075] Simplified to Xa = P. The least square method is used to solve the optimal coefficient a = (X T X) -1 X T P, obtain the third-order polynomial model parameters a0, a1, a2, a3, that is, the motion trajectory model is predicted based on the actual trajectory sequence. Substitute the updated model parameters into the polynomial model to complete the update of the prediction model. Interpolate according to the encoder sampling time, specifically, select , substitute into the updated polynomial model, and calculate the interpolated predicted trajectory sequence according to the third-order polynomial model formula.

[0076] It should be noted that step 4 specifically involves reading the grating encoder measurement value at the nth encoder sampling moment (n = 1, 2, …, m) during the kth blind time. Simultaneously, the corresponding value of the interpolated predicted trajectory sequence at the current moment is subtracted from the current encoder measurement value to calculate the telescope's angular position error during the blind time, which is then input into the telescope motion control unit.

[0077] It should be noted that step 5 specifically includes: confirming whether the tracking mission is to continue, if so, repeating steps 2 to 4; if not, ending the mission and sending a control command to shut down the telescope control system.

[0078] This embodiment constructs a telescope motion control system, whose sensors specifically include the aforementioned optical camera and grating encoder. The optical camera can image non-cooperative targets and calculate their miss distance and tracking error. The grating encoder can measure the telescope's rotation angle. The calculated tracking error can be directly input into the telescope motion control system to control the telescope's rotation and track the non-cooperative target.

[0079] In this embodiment, a traditional optical feedback method is compared with the non-cooperative target trajectory prediction algorithm proposed in the present invention that integrates the camera miss distance and the grating encoder information. Figure 4By comparing the reference trajectory of direct optical camera sampling and the method proposed in the present invention, it can be seen that the target trajectory predicted by the method proposed in the present invention is closer to the actual trajectory of the non-cooperative target, and is also beneficial to improving the closed-loop control frequency of the system.

[0080] Figure 5 This is the tracking performance of the telescope for non-cooperative targets. It can be seen that compared with the traditional optical feedback tracking method, the method proposed in this invention improves the closed-loop tracking accuracy and effectively reduces the tracking error, making the telescope's tracking performance for non-cooperative targets meet the expected requirements.

[0081] In summary, the present invention provides a non-cooperative target trajectory prediction method that integrates camera miss distance and encoder information. By integrating the camera miss distance and grating encoder information of an optical telescope, the present invention obtains the actual trajectory sequence of the non-cooperative target. Using a prediction algorithm, the motion trajectory of the tracking target within the blind time is predicted. At the camera sampling moment, the telescope motion is directly controlled through optical feedback. At the encoder sampling moment, the corresponding predicted value is subtracted from the encoder measured value to obtain the tracking error within the blind time. This error is input into the telescope motion control system. This increases the control frequency and closed-loop bandwidth of the telescope motion control system, reduces the error between the reference trajectory and the actual trajectory of the tracking target, and thus improves the optical telescope's tracking capability for non-cooperative targets.

[0082] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A non-cooperative target trajectory prediction method that integrates camera miss distance and encoder information, characterized in that: The steps include: Step 1: System initialization, including obtaining initial guidance information and initializing the telescope settings. Step 1 specifically includes: Step 1.1: Start the telescope motion control system and initialize the parameters. The optical telescope is equipped with an optical camera and a grating encoder, which are used to measure the target miss distance and the telescope rotation angle respectively. The sampling time of the optical camera is T c , the sampling time of the grating encoder is T e , the camera sampling time is an integer multiple of the encoder sampling time; the telescope control system sampling time T s The same as the encoder sampling time; the time between two imaging of the optical camera is called the blind time. During this period of time, the system cannot obtain camera image information, but the encoder and motion control system still measure and control at the above system sampling frequency; Step 1.2: Input the guidance information, i.e. the initial trajectory of the tracking target, and set the initial target actual trajectory sequence; the initial target actual trajectory sequence R of the system a (0), R e (0) The data corresponding to the last several camera sampling moments in the guidance information are selected, where R a Indicates azimuth data, R e Indicates pitch angle data; Step 1.3: The telescope motion control system controls the telescope to track the target based on the guidance information, so that the target appears in the field of view of the optical camera; Step 2: At the camera sampling moment, the optical camera exposes and images the tracking target, recognizes the image, and calculates the miss distance. This is further converted into the angular position error of the telescope in the azimuth and pitch directions and input into the telescope motion control unit. At the same time, the grating encoder samples and reads the encoder measurement value at the current moment. Step 3: After completing an optical imaging and miss distance reading, the telescope tracks the time it enters the blind zone. The camera miss distance obtained at the camera sampling moment is integrated with the grating encoder information to calculate the actual position of the target and update the actual trajectory sequence. Based on this actual trajectory sequence, a trajectory prediction algorithm is used to predict the motion trajectory of the non-cooperative target before the next optical imaging is completed. At the same time, interpolation is performed according to the encoder sampling moment to obtain a predicted trajectory sequence. Step 4: At the encoder sampling moment, read the grating encoder measurement value; at the same time, read the predicted value corresponding to the current moment in the predicted trajectory sequence, subtract it from the encoder measurement value, and obtain the angular position error, which is input into the telescope motion control unit; Step 5: Confirm whether to continue the tracking mission. If yes, repeat steps 2 to 4. If no, end the mission and turn off the telescope control system.

2. The non-cooperative target trajectory prediction method of fusion camera miss distance and encoder information according to claim 1, wherein Step 2 specifically includes: Step 2.1: At the kth optical camera sampling moment, the camera exposes and images the tracking target, identifies the image pixels and calculates the miss distance; Step 2.2: Convert the miss distance into the angular error of the telescope in azimuth and elevation directions; let the miss distance on the horizontal axis of the imaging be Δx c , the miss distance on the vertical axis is Δy c , the focal length of the camera is f c , then at the kth optical camera sampling moment, that is, the kmth system sampling moment, calculate the azimuth angle error e ca , pitch angle error e ce and input the position error into the telescope motion control unit; Step 2.3: Simultaneously read the current grating encoder measurement values, i.e. the rotation angles of the telescope in the azimuth and elevation directions.

3. The non-cooperative target trajectory prediction method of fusion camera miss distance and encoder information according to claim 1, characterized in that, Step 3 specifically includes: Step 3.1: After completing the k-th optical imaging and miss distance reading, the telescope tracks the time when it enters the k-th blind zone; the camera miss distance obtained at the camera sampling moment and the grating encoder information are integrated to calculate the actual position of the target and further update the actual trajectory sequence; Step 3.2: Based on the updated actual trajectory sequence, a polynomial fitting algorithm is used to predict the trajectory of the non-cooperative target before the next optical imaging is completed. The actual trajectory sequence data points are substituted into the polynomial model to obtain a matrix equation. The least squares method is used to solve the optimal coefficients and obtain the polynomial model parameters, thus predicting the trajectory model based on the actual trajectory sequence. Step 3.3: Substitute the model parameters updated in step 3.2 into the polynomial model to complete the update of the prediction model; interpolate according to the encoder sampling time, substitute it into the updated polynomial model, and calculate the interpolated prediction trajectory sequence.

4. The non-cooperative target trajectory prediction method of fusion camera miss distance and encoder information according to claim 1, wherein Step 4 specifically includes: Step 4.1: At the nth encoder sampling moment (n=1, 2, ..., m) in the kth blind time, read the grating encoder measurement value; Step 4.2: Subtract the corresponding value of the interpolated predicted trajectory sequence at the current moment from the current encoder measurement value to calculate the angular position error of the telescope during the blind time and input it into the telescope motion control unit.

5. The non-cooperative target trajectory prediction method of fusion camera miss distance and encoder information according to claim 1, characterized in that, Step 5 specifically includes: confirming whether the tracking mission is to continue, if so, repeating steps 2 to 4; if not, ending the mission and sending a control command to shut down the telescope control system.

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