A method and system for accurate control of longitudinal overlap of a pushbroom aerial camera

Abstract

The present application relates to photoelectric platform imaging control technical field, especially a kind of swing sweep type aerial camera longitudinal overlap ratio accurate control method and system thereof;The present application first utilizes the early flight trajectory and attitude of carrier aircraft to estimate the position and camera visual axis pointing of future flight;Then according to camera visual axis pointing, dynamic adjustment is carried out after camera visual axis and photographing;The present application improves the control precision of swing sweep type aerial camera longitudinal overlap ratio by estimating carrier aircraft attitude, reserving angle dynamic condition and position trigger type control, ensures that aerial camera can be more accurate and efficient in flight to complete task.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic platform imaging control technology, and in particular to a method and system for precise control of longitudinal overlap rate of a sweeping aerial camera. Background Technology

[0002] Currently, during the imaging process, the longitudinal overlap rate of the sweeping aerial camera is easily affected by factors such as changes in the flight path, attitude, and ground undulations, which can even cause gaps between different strips in the image. In order to ensure the stability of the longitudinal overlap rate of the sweeping aerial camera and avoid the phenomenon of gaps between strips, precise control of the longitudinal overlap rate is required.

[0003] Currently, longitudinal overlap rate control for aerial cameras is generally ensured through design analysis and adjusted by controlling the shooting cycle. Typically, the longitudinal overlap rate is adjusted by the shooting cycle. During the shooting cycle adjustment, the servo system performs speed control, and the position loop is in an open loop state, making the motion position uncontrollable. This makes it impossible to achieve precise control of the longitudinal overlap rate. With modern aerial cameras having increasingly longer focal lengths and smaller pixel sizes, the longitudinal field of view of the camera is becoming smaller. Given a fixed amplitude of longitudinal overlap rate fluctuations, the impact on the percentage of image overlap is becoming increasingly significant. Summary of the Invention

[0004] The main technical problem solved by this invention is to provide a precise control method for the longitudinal overlap rate of a sweeping aerial camera. By estimating the aircraft attitude, reserving dynamic angle conditions, and using position-triggered control, this method effectively improves the control accuracy of the longitudinal overlap rate of the sweeping aerial camera, ensuring that the aerial camera can complete its mission more accurately and efficiently during flight. This invention also provides a precise control system for the longitudinal overlap rate of a sweeping aerial camera.

[0005] To solve the above-mentioned technical problems, one technical solution adopted by the present invention is: to provide a method for precise control of longitudinal overlap rate of a sweeping aerial camera, comprising the following steps:

[0006] Step S1: Use the aircraft's previous flight trajectory and attitude to predict the future flight position and camera line-of-sight orientation;

[0007] Step S2: Dynamically adjust the camera's line of sight according to the camera's line of sight direction before taking the picture.

[0008] As an improvement to the present invention, step S1 includes:

[0009] Step S11: Based on the aircraft pitch angle, roll angle and heading angle at the start of the photo taking, and the aircraft pitch angle, roll angle and heading angle at the current time, obtain the angle at which the aircraft causes the camera to deviate from the initial route during the photo taking phase, and thus predict the line-of-sight pointing angle during the next photo taking cycle.

[0010] Step S12: Based on the pointing angle of the line of sight, obtain the azimuth pointing angle and the depression pointing angle of the camera;

[0011] Step S13: Send the camera's azimuth pointing angle and depression pointing angle to the azimuth and depression angle controller. The azimuth and depression angle controller will make adjustments and set a reserved angle as the actual return position.

[0012] As a further improvement of the present invention, in step S11, at the beginning of the shooting stage, the position angle controller controls the position angle reflector and the position angle body to perform speed control, while the camera controller estimates the position that the position angle reflector needs to move to in real time and sends it to the position angle controller.

[0013] As a further improvement of the present invention, in step S11, when the heading angle of the carrier aircraft deviates by more than 3° from the heading angle of the carrier aircraft at the initial time, it is determined that the carrier aircraft has not maintained stable straight flight, and the current state is taken as the new initial state, and the subsequent time calculation is based on the current time.

[0014] As a further improvement of the present invention, in step S13, the position and depression angle controller sets a reserved angle as the actual return position during the camera return segment based on the received position and depression angle information and the current flight status of the carrier aircraft.

[0015] As a further improvement of the present invention, in step S2, the position and tilt angle controller compares and judges the position and tilt angle reflector based on its own motion state collected in real time and the information sent by the camera controller. If it is determined that the position and tilt angle reflector has moved into position, the position and tilt angle controller sends a photo trigger signal to the camera controller.

[0016] As a further improvement of the present invention, in step S2, the estimated maximum time of the shooting acceleration segment is no more than 300ms. 300ms after the start of shooting, before the azimuth reflector has reached the designated position, the azimuth angle controller also sends a shooting trigger signal to the camera controller.

[0017] As a further improvement of the present invention, in step S2, 300ms after the start of the shooting, if the azimuth reflector has not yet reached the designated position, the azimuth angle controller reports the deviation to the camera controller, and the camera controller adjusts the shooting time of this cycle based on the deviation.

[0018] A precise control system for longitudinal overlap rate of a sweeping aerial camera, comprising:

[0019] A camera controller is used to control the adjustment of the camera's line of sight and to take pictures.

[0020] The pitch angle controller is used to control the pitch angle reflector and the pitch angle fuselage to adjust the speed.

[0021] The prediction module is used to predict the future flight position and the camera's line-of-sight pointing angle.

[0022] The beneficial effects of this invention are as follows: Compared with the prior art, this invention effectively improves the control accuracy of the longitudinal overlap rate of the sweep-type aerial camera by predicting the aircraft attitude, reserving dynamic angle conditions, and position-triggered control, thus ensuring that the aerial camera can complete its mission more accurately and efficiently during flight. Attached Figure Description

[0023] Figure 1 This is a flowchart illustrating the steps of the present invention;

[0024] Figure 2 For the present invention Figure 1 Step-by-step flowchart;

[0025] Figure 3 This is a schematic diagram illustrating the implementation of the sweeping-type longitudinal overlap rate control of the aeronautical phase according to the present invention;

[0026] Figure 4 This is a timing diagram of the scanning camera of the present invention.

[0027] Figure 5 This is a diagram showing the longitudinal overlap rate control results of the sweeping camera of the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0029] Please refer to Figures 1 to 5 The present invention provides a method for precise control of longitudinal overlap rate of a sweeping aerial camera, comprising the following steps:

[0030] Step S1: Use the aircraft's previous flight trajectory and attitude to predict the future flight position and camera line-of-sight orientation;

[0031] Step S2: Dynamically adjust the camera's line of sight according to the camera's line of sight direction before taking the picture.

[0032] Step S1 includes:

[0033] Step S11: Based on the aircraft pitch angle, roll angle and heading angle at the start of the photo taking, and the aircraft pitch angle, roll angle and heading angle at the current time, obtain the angle at which the aircraft causes the camera to deviate from the initial route during the photo taking phase, and thus predict the line-of-sight pointing angle during the next photo taking cycle.

[0034] Step S12: Based on the pointing angle of the line of sight, obtain the azimuth pointing angle and the depression pointing angle of the camera;

[0035] Step S13: Send the camera's azimuth pointing angle and depression pointing angle to the azimuth and depression angle controller. The azimuth and depression angle controller will make adjustments and set a reserved angle as the actual return position.

[0036] This invention uses the aircraft's previous flight trajectory and attitude to predict future flight position and camera line-of-sight, and then adjusts and adapts to changes in the aircraft's flight state by adjusting the angle of the servo's reserved acceleration segment; at the same time, it achieves precise control through position triggering, and increases the upper limit of the triggering time to avoid abnormal operation under extreme conditions.

[0037] The precise control method designed in this invention effectively improves the control accuracy of the longitudinal overlap rate of the sweep-type aerial camera by estimating the aircraft attitude, reserving dynamic angle conditions, and position-triggered control, ensuring that the aerial camera can complete its mission more accurately and efficiently during flight.

[0038] In step S11, during the initial phase of image capture, the pitch angle controller controls the pitch angle reflector and the pitch angle fuselage to perform speed control. Simultaneously, the camera controller estimates the position the pitch angle reflector needs to move to in real time and sends this information to the pitch angle controller. If the aircraft's heading angle deviates by more than 3° from its initial heading angle, it is determined that the aircraft is not maintaining stable straight flight. The current state is taken as the new initial state, and subsequent time calculations are based on this current state. Specifically, the camera controller images the aircraft's pitch angle, roll angle, and heading angle based on the initial image capture time T0, and the current time T. n The calculation of the aircraft's pitch angle, roll angle, and heading angle involves the aircraft causing the camera to deviate from its initial flight path and angle during the photo-taking phase. The line-of-sight pointing angle for the next photo-taking cycle is estimated. To avoid error accumulation leading to decreased overlap control accuracy, if the heading angle deviates by more than 3° from the initial time T0, it is considered that the aircraft has not maintained stable straight flight. The current time T... n The state is the new T0 state, and subsequent time calculations are based on the current time.

[0039] In step S13, the position and depression angle controller sets a reserved angle as the actual return position during the camera return segment based on the received position and depression angle information and the current flight status of the aircraft. Specifically, after the camera controller calculates the line of sight pointing, it converts it into the camera's position and depression angle and sends it to the position and depression angle controller. Based on these parameters and the current flight status of the aircraft, and mainly considering the aircraft's speed-to-altitude ratio, the position and depression angle controller adds a certain reserved angle as the actual return position during the camera return segment.

[0040] In step S2, the position and tilt controller compares its own motion state collected in real time with the information sent by the camera controller. If it determines that the azimuth reflector has reached the correct position, the position and tilt controller sends a photo-taking trigger signal to the camera controller. The estimated maximum time for the photo-taking acceleration phase is no more than 300ms. If the azimuth reflector has not reached the designated position 300ms after the start of the photo-taking process, the position and tilt controller also sends a photo-taking trigger signal to the camera controller. Specifically, at the beginning of the photo-taking process, the position and tilt controller controls the speed of the azimuth reflector and the tilt camera body, accelerating from a standstill to a stable speed. Simultaneously, based on the estimated position, the camera controller calculates the required position for the azimuth reflector in real time and sends this calculation to the position and tilt controller. The position and tilt controller collects its own motion state in real time through the encoder and compares it with the commanded position sent by the camera controller. Once the azimuth reflector has reached the correct position, it sends a photo-taking trigger signal to the camera controller. The estimated maximum time for the photo-taking acceleration phase is no more than 300ms. If the azimuth reflector has not reached the designated position 300ms after the start of the photo-taking process, the position and tilt controller also sends a photo-taking trigger signal to the camera controller to avoid affecting the overall timing of the camera.

[0041] In step S2, if the apex reflector has not reached the designated position 300ms after the start of the shooting, the apex angle controller reports the deviation to the camera controller. The camera controller adjusts the shooting time of the current cycle based on the deviation. Specifically, if the apex angle is not in place within 300ms, the vertical overlap rate between the current cycle image and the previous cycle image is unlikely to meet the target requirements. The apex angle controller reports the deviation to the camera controller, and the camera controller adjusts the shooting time of the current cycle based on the deviation to ensure that the vertical overlap rate between the next cycle image and the current cycle image is recalculated, avoiding error accumulation and large fluctuations in the vertical overlap rate.

[0042] The present invention also provides a longitudinal overlap rate precision control system for a sweeping aerial camera, comprising:

[0043] A camera controller is used to control the adjustment of the camera's line of sight and to take pictures.

[0044] The pitch angle controller is used to control the pitch angle reflector and the pitch angle fuselage to adjust the speed.

[0045] The prediction module is used to predict the future flight position and the camera's line-of-sight pointing angle.

[0046] This invention provides an embodiment, which includes the following specific implementation:

[0047] 1. The camera controller captures images based on the aircraft's pitch angle, roll angle, and heading angle at the start time T0 of the image capture, and the current time T. nThe calculation of the aircraft's pitch angle, roll angle, and heading angle involves the aircraft causing the camera to deviate from its initial flight path and angle during the photo-taking phase. The line-of-sight pointing angle for the next photo-taking cycle is estimated. To avoid error accumulation leading to decreased overlap control accuracy, if the heading angle deviates by more than 3° from the initial time T0, it is considered that the aircraft has not maintained stable straight flight. The current time T... n The state is the new T0 state, and subsequent time calculations are based on the current time.

[0048] 2. After the camera controller calculates the line of sight, it converts it into the camera's azimuth pointing angle and depression pointing angle, and sends it to the azimuth and depression controller. Based on these parameters and the current flight status of the aircraft, the azimuth and depression controller, mainly considering the aircraft's speed-to-altitude ratio, adds a certain reserved angle as the actual return position during the camera's return journey.

[0049] 3. At the beginning of the shooting phase, the position and tilt controller controls the speed of the position and tilt of the camera body, accelerating from a standstill to a stable speed. At the same time, the camera controller calculates the position that the position and tilt controller needs to move to in real time based on the prediction and sends it to the position and tilt controller. The position and tilt controller collects its own motion status in real time through the encoder and compares it with the position command sent by the camera controller. Once the position is reached, it sends a shooting trigger signal to the camera controller.

[0050] 4. The estimated maximum time of the photo acceleration phase is no more than 300ms. 300ms after the start of the photo capture, before the azimuth reflector reaches the designated position, the tilt controller also sends a photo capture trigger signal to the camera controller to avoid affecting the overall timing of the camera.

[0051] 5. If the 300ms apex reflector is not in position, the longitudinal overlap rate between the current cycle image and the previous cycle image is unlikely to meet the target requirements. The apex angle controller reports this deviation to the camera controller. The camera controller adjusts the current cycle shooting time based on this deviation to ensure that the longitudinal overlap rate between the next cycle image and the current cycle image is recalculated, avoiding error accumulation and causing large fluctuations in the longitudinal overlap rate.

[0052] Camera shooting sequence as follows Figure 2 As shown, the implementation steps of its technical solution are as follows:

[0053] (1) Under the assumptions of stable straight flight of the carrier aircraft, no ground undulation, and good repeatability of the servo system, calculate the shooting period of the camera for different stripes:

[0054]

[0055] In the formula: b hw —Pixel size is 24μm;

[0056] Mhw —The longitudinal pixel count of the infrared detector is 640;

[0057] f hw —The infrared optical system lens has a focal length of 1000mm;

[0058] ρ zx —Vertical overlap rate, taken as 12%;

[0059] γ—Camera's initial tilt angle for taking a picture, 0° horizontally, positive when the line of sight points to the right;

[0060] η—Aircraft speed-to-height ratio;

[0061] (2) Considering the influence of the aircraft's flight path and attitude angle, record the heading angle at the current moment. n Pitch n and roll angle n The camera's tilt and azimuth angles are calculated by comparing them with the heading angle (Heading0), pitch angle (Pitch0), and roll angle (Roll0) at the initial moment of shooting. These angles are used as a basis to compensate for attitude changes during this period. Specifically, the initial tilt angle is 16°, and the azimuth angle is 45°. The current tilt angle is 16° - (Roll0 - 45°). n -Roll0), the given angle is 16°-(Pitch) n -Pitch0)-(Heading n -Heading0) To avoid error accumulation caused by drastic changes in the aircraft's course and attitude, when the heading angle and attitude angle change by more than 3°, the current course and attitude are used as the initial attitude again.

[0062] (3) The position and tilt controller performs return position control based on the given tilt angle and the given position angle. During the initial acceleration phase of speed photography, the camera controller calculates the real-time given tilt angle and the given position angle in real time and sends them to the position and tilt controller. The camera's position and tilt controller sends a photo trigger signal when the position angle reaches the given position angle. At the end of the 300ms acceleration phase, even if the position angle has not reached the given position, a photo trigger signal is sent. The given position angle and the given tilt angle, as well as the actual position angle and the starting tilt angle, are shown in Table 3.

[0063] Table 1:

[0064]

[0065]

[0066] (4) The deviation between the given azimuth shooting angle and the actual azimuth shooting starting angle in Table 1 represents the fluctuation of the longitudinal overlap rate in this cycle. If it is not corrected, the calculation benchmark for the longitudinal overlap rate in the next cycle will be inaccurate. It is necessary to correct the shooting cycle to eliminate the influence of this deviation. The correction cycle T XIU The calculation formula is:

[0067]

[0068] In the formula:

[0069] α give —The camera angle is given;

[0070] α true —According to the actual starting angle of the photograph;

[0071] γ—Camera's initial tilt angle for taking a picture, 0° horizontally, positive when the line of sight points to the right;

[0072] η—Aircraft speed-to-height ratio;

[0073] The corrected photo time is shown in Table 4.

[0074] Table 2:

[0075] 1 45.012 44.967 36.2 2 45.018 44.971 68.2 3 44.99 44.942 56.4 4 45.038 44.993 51.9 5 45.039 44.991 87.8 6 44.997 44.949 54.6 7 45.061 45.013 32.2 8 45.049 45.003 45.6 9 44.936 44.887 83.2

[0076] (5) By predicting and correcting the aircraft's flight path and attitude, adjusting the azimuth and pitch angle starting angle in real time, and further improving the accuracy of longitudinal overlap by using trigger signals and image capture cycles, the flight performance in actual flight is as follows: Figure 5 As shown, the verification results demonstrate that the precise control method for longitudinal overlap rate of aerial cameras using the present invention effectively considers the influence of the aircraft's flight path and attitude, eliminates errors caused by servo fluctuations, and achieves precise control of the longitudinal overlap rate of the sweep-type aerial camera.

[0077] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for precise control of longitudinal overlap rate of a sweeping aerial camera, characterized in that, Includes the following steps: Step S1: Use the aircraft's previous flight trajectory and attitude to predict the future flight position and camera line-of-sight orientation; Step S2: Dynamically adjust the camera's line of sight according to its orientation before taking the picture; Step S1 includes: Step S11: Based on the aircraft pitch angle, roll angle and heading angle at the start of the photo taking, and the aircraft pitch angle, roll angle and heading angle at the current time, obtain the angle at which the aircraft causes the camera to deviate from the initial route during the photo taking phase, and thus predict the line-of-sight pointing angle during the next photo taking cycle. Step S12: Based on the pointing angle of the line of sight, obtain the azimuth pointing angle and the depression pointing angle of the camera; Step S13: Send the camera's azimuth pointing angle and depression pointing angle to the azimuth and depression angle controller, which will then adjust and set a reserved angle as the actual return position. In step S2, the position tilt controller compares and judges its own motion state collected in real time with the information sent by the camera controller. If it is determined that the position tilt reflector has moved into position, the position tilt controller sends a photo trigger signal to the camera controller.

2. The method for precise control of longitudinal overlap rate of a sweeping aerial camera according to claim 1, characterized in that, In step S11, at the beginning of the shooting phase, the position and tilt controller controls the speed of the position and tilt mirror and the camera body, while the camera controller estimates the position that the position and tilt mirror needs to move to in real time and sends it to the position and tilt controller.

3. The method for precise control of longitudinal overlap rate of a sweeping aerial camera according to claim 2, characterized in that, In step S11, if the aircraft's heading angle deviates by more than 3° from the heading angle at the initial moment, it is determined that the aircraft has not maintained stable straight flight. The current state is taken as the new initial state, and subsequent time calculations are based on the current time.

4. The method for precise control of longitudinal overlap rate of a sweeping aerial camera according to claim 3, characterized in that, In step S13, the position and depression angle controller sets a reserved angle as the actual return position during the camera return segment based on the received position and depression angle information and the current flight status of the aircraft.

5. The method for precise control of longitudinal overlap rate of a sweeping aerial camera according to claim 1, characterized in that, In step S2, the estimated maximum time of the image capture acceleration phase is no more than 300ms. 300ms after the start of image capture, before the azimuth reflector has reached the designated position, the azimuth angle controller also sends an image capture trigger signal to the camera controller.

6. The method for precise control of longitudinal overlap rate of a sweeping aerial camera according to claim 1, characterized in that, In step S2, 300ms after the start of the shooting, if the azimuth reflector has not yet reached the designated position, the azimuth angle controller reports the deviation to the camera controller, and the camera controller adjusts the shooting time of this cycle based on the deviation.

7. A precise control system for longitudinal overlap rate of a sweeping aerial camera, characterized in that, The method for precise control of longitudinal overlap rate of a sweeping aerial camera as described in any one of claims 1-6 is employed; the control system includes: A camera controller is used to control the adjustment of the camera's line of sight and to take pictures. The pitch angle controller is used to control the pitch angle reflector and the pitch angle fuselage to adjust the speed. The prediction module is used to predict the future flight position and the camera's line-of-sight pointing angle.

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