Angle correction method for rotary table

Abstract

An angle correction method for a rotary table belongs to the field of large-scene video monitoring, and comprises the following steps: determining correction point information of an unmanned aerial vehicle as a target object; the unmanned aerial vehicle flies one by one according to correction points, and a turntable is controlled to collect correction point unmanned aerial vehicle image data; calculating a rotary table horizontal angle correction value and rotary table pitching angle correction values at different horizontal positions according to the position of the unmanned aerial vehicle target object in the image; and generating a rotary table pitching angle correction value at any horizontal position by using an interpolation method. The horizontal angle of the rotary table is corrected in a multi-correction-point averaging mode, interference caused by single-position calculation errors is avoided, pitching angle correction at any position is achieved, the installation process of equipment is simplified, and the requirement for the horizontal precision of an installation face is lowered; the unmanned aerial vehicle is used as a target object, and the problems that the field environment is complex, and correction target objects with proper sizes and distances are not suitable for selection are solved. The distance between the unmanned aerial vehicle and the rotary table and the observation field angle are calculated according to the actual precision requirement, and the precision can be controlled.

Description

Technical Field

[0001] The invention belongs to the technical field of large-scene video monitoring, and in particular relates to an angle correction method for a turntable. Background Art

[0002] Accurate correction of the turntable angle is of vital importance to the accuracy and reliability of the positioning system. In complex monitoring, tracking or automated control scenarios, the turntable is a key component that carries the camera equipment or other sensors. Even a slight deviation in its angle may lead to significant errors in the target positioning information. Through meticulous turntable angle correction, the camera lens or sensor pointing position information can be accurately obtained, thereby effectively reducing the positioning inaccuracy caused by angle deviation due to installation errors and environmental factors.

[0003] Most current turntable angle correction methods are limited to correcting the horizontal zero position information, usually by identifying a target object to determine the device's true north direction. However, in actual applications, the turntable's mounting surface may be uneven, and the device's mechanical accuracy may be insufficient. Therefore, in order to obtain a more accurate correction effect, it is necessary not only to pay attention to the correction of the horizontal position, but also to measure and record the horizontal and pitch angle errors of the turntable at different horizontal positions. Such a comprehensive correction strategy can more accurately reflect the actual state of the turntable, thereby achieving more precise positioning.

[0004] Chinese patent CN113223156A discloses "a method for measuring and correcting the initial angle of the gimbal". This method calculates the absolute height of the gimbal observation lens based on the sea level and the air pressure and temperature at the bottom of the gimbal tower, searches for the position of the gimbal on the satellite map according to the longitude and latitude of the bottom of the tower, determines the longitude and latitude coordinates of the gimbal through feature recognition, selects the target object observable by the gimbal, and obtains its longitude and latitude coordinates: inputs the gimbal coordinates, absolute height and target object coordinates into the correction tool, outputs the PAN value of the true north of the gimbal, and corrects the initial angle of the gimbal according to the PAN value of the true north. This method uses a single target object to correct the true north, which is easily affected by noise, and this method does not consider the problem of differences in error values ​​of different horizontal positions caused by insufficient equipment accuracy and uneven gimbal installation surface.

[0005] Chinese patent CN102314182A discloses "a method and device for pan-tilt positioning". This method obtains the current pan-tilt horizontal position information and the local magnetic declination, calculates the number of steps the motor should rotate according to the current horizontal position information and the magnetic declination, controls the pan-tilt to point to due north and sets it as the horizontal origin according to the number of steps the motor should rotate, and establishes the relationship between the pan-tilt coordinate system and the geographic coordinate system. This method can only correct the horizontal angle, but not the pitch angle, and the drive motor generally loses steps during the rotation process, so the correction accuracy of this method is low.

[0006] In summary, the existing angle correction methods for turntables have the following disadvantages:

[0007] 1) Only correct the north direction: Most of the current turntable angle correction methods are limited to correcting the horizontal zero position information. Usually, the true north direction of the device is determined by identifying the target object, and the angle correction in the pitch direction cannot be achieved.

[0008] 2) Horizontal 360-degree pitch correction cannot be achieved: Most existing turntable angle correction methods are based on position correction at a single point. When the equipment is installed on a non-horizontal surface, pitch angle correction at any horizontal position cannot be achieved.

[0009] 3) Low correction accuracy: Existing turntable angle correction methods based on magnetic declination, checking motor steps, etc. have large angle errors, motor step loss and other phenomena, and the correction accuracy is low.

[0010] 4) The calibration target is difficult to select: The field environment is complex, and it is difficult to select a calibration target of appropriate size and distance, which makes it difficult to calibrate the turntable angle. Summary of the invention

[0011] In order to solve the problems that the existing turntable angle correction method only corrects the north direction, cannot achieve horizontal 360-degree pitch correction, has low correction accuracy, and is difficult to select a correction target, the present invention provides an angle correction method for a turntable.

[0012] The technical solution adopted by the present invention to solve the technical problem is as follows:

[0013] The present invention provides a method for calibrating an angle of a turntable, comprising the following steps:

[0014] Step S1: Determine the calibration point information of the drone as a target object;

[0015] Step S2: The UAV flies sequentially to each calibration point, and controls the turntable to collect the UAV image data of the calibration point;

[0016] Step S3: Calculate the turntable horizontal angle correction value and the turntable pitch angle correction values ​​at different horizontal positions according to the position of the drone target in the image;

[0017] Step S4: Generate a turntable pitch angle correction value at any horizontal position using an interpolation method.

[0018] Furthermore, the specific implementation process of step S1 is as follows:

[0019] S1.1: Obtain the height and position information of the turntable installation;

[0020] S1.2: Calculate the straight-line distance between the UAV and the turntable and the turntable's observation field of view during calibration based on the calibration accuracy requirements and the size of the UAV;

[0021] S1.3: Use GIS to obtain the position information of the calibration point with a straight-line distance D from the turntable.

[0022] Furthermore, in step S1.1, the installation height of the turntable is the horizontal plane height of the center point of the turntable visible light camera window, and the position information includes the latitude and longitude information of the turntable installation position.

[0023] Furthermore, in step S1.2, the calculation formula of the straight-line distance D between the drone and the turntable is:

[0024] D = ALT_ERR / tan (α)

[0025] The calculation formula of the turntable observation field angle is:

[0026] FOV=2*atan((L UVA *img_wid) / (2*N*D))

[0027] Among them, ALT_ERR represents the altitude error of the UAV; α represents the angle accuracy error limit of the correction; FOV represents the horizontal field of view angle used by the turntable to observe the UAV during correction; L UVA represents the width of the drone, img_wid represents the number of image columns of the turntable visible light camera, N represents the number of pixels of the drone's horizontal imaging; D represents the straight-line distance between the drone and the turntable.

[0028] Furthermore, in step S1.3, first obtain the position information of the turntable installation position in the north direction and at a straight-line distance D from the turntable as the first correction point; with the turntable installation position as the center and the direction with an angle β with the north direction of the turntable installation position, determine the position information at a straight-line distance D from the turntable as the second correction point; in this way, determine a correction point at a straight-line distance D from the turntable at every angle β, until the selection of M correction points in a 360-degree circle is completed.

[0029] Furthermore, the specific implementation process of step S2 is as follows:

[0030] S2.1: The coordinates of the calibration points are entered into the UAV flight trajectory in sequence;

[0031] S2.2: Control the drone to hover at the first calibration point in the flight trajectory. The flight altitude is the horizontal plane height of the center point of the turntable visible light camera window.

[0032] S2.3: Control the turntable to track the UAV according to the turntable's observation field of view;

[0033] S2.4: Repeat steps S2.2 to S2.3 to complete the acquisition of UAV target image data for M correction points.

[0034] Furthermore, in step S2.3, the pitch angle of the turntable is set to 0 degrees, and the turntable is controlled to rotate horizontally until the drone is located in the column where the horizontal center point of the turntable's visible light image is located, and the current turntable's first horizontal angle Hor1 and the first pitch pixel deviation shift_y1 of the drone's target center point from the center point of the turntable's visible light image are recorded.

[0035] Furthermore, in step S3, the calculation formula of the turntable horizontal angle correction value is:

[0036] coor i =Hor i -i*β

[0037]

[0038] Among them, Hor i Indicates the horizontal angle of the turntable corresponding to the i-th calibration point, coor i represents the turntable horizontal angle correction value calculated by the i-th correction point, M represents the number of correction points, and coor represents the final turntable horizontal angle correction value.

[0039] Furthermore, in step S3, the calculation formula of the turntable pitch angle correction value at different horizontal positions is:

[0040] pit i =atan(2*shift_y i *tan(FOV*img_hei / (2*img_wid)) / img_hei)

[0041] Among them, pit i Indicates the uncorrected turntable horizontal angle Hor i The pitch angle correction value of the turntable, shift_y i It represents the pitch pixel deviation of the UAV target center point from the center point of the turntable visible light image at the i-th calibration point, img_hei represents the number of image rows of the turntable visible light camera, img_wid represents the number of image columns of the turntable visible light camera, FOV represents the horizontal field of view used by the turntable to observe the UAV during calibration, and i represents the calibration point sequence number.

[0042] Furthermore, in step S4, the calculation formula of the turntable pitch angle correction value at any horizontal position is:

[0043]

[0044] Where Hor represents the uncorrected horizontal angle of any turntable pitch correction value to be determined, satisfying Hor k ≤Hor≤Hor k+1, 1≤k≤M, Hor k Indicates the horizontal angle of the turntable corresponding to the kth correction point, Hor k+1 represents the horizontal angle of the turntable corresponding to the k+1th correction point; pit k Indicates the horizontal angle of the turntable Hor k The turntable pitch angle correction value at k+1 Indicates the horizontal angle of the turntable Hor k+1 The turntable pitch angle correction value at ; * indicates a multiplication operation.

[0045] The beneficial effects of the present invention are:

[0046] The invention provides an angle correction method for a turntable, which is used for the horizontal and pitch angle correction of turntable equipment and can reduce the requirements for the turntable installation accuracy in the field of photoelectric measurement.

[0047] The present invention realizes the horizontal and pitch angle correction of the turntable based on the unmanned aerial vehicle. By obtaining the height and position information of the turntable installation, the straight-line distance between the unmanned aerial vehicle and the turntable during correction and the observation field angle of the turntable are calculated according to the correction accuracy requirements and the size of the unmanned aerial vehicle, and the position information of the distance correction point corresponding to the turntable is obtained by using GIS. The number of correction points is related to the positioning accuracy and is evenly distributed around the horizontal circle of the turntable. The unmanned aerial vehicle flies point by point according to the position information of the correction point, and the height is consistent with the height of the equipment. The turntable is controlled to track the unmanned aerial vehicle according to the observation field angle, and the image of the unmanned aerial vehicle and the horizontal pitch angle of the equipment at each correction point are collected. The turntable horizontal and pitch angle correction values ​​at different horizontal positions are calculated according to the position of the unmanned aerial vehicle in the image. The method of the present invention uses unmanned aerial vehicles as correction targets, which solves the problem of difficulty in selecting correction points in the field environment; unmanned aerial vehicle targets are collected at multiple different horizontal positions, and the horizontal and pitch angle corrections at different horizontal positions are realized, which reduces the requirements of the turntable for the horizontal installation surface; the appropriate straight-line distance between the unmanned aerial vehicle and the turntable can achieve high-precision angle correction.

[0048] Compared with the existing turntable angle correction method, the technical solution proposed in the present invention brings effect and convenience to the turntable angle correction in the following aspects:

[0049] 1. Both horizontal and pitch angles can be corrected: The present invention corrects the horizontal angle of the turntable by averaging multiple correction points to avoid interference caused by calculation errors at a single position; it realizes correction of the pitch angle at any position, simplifies the installation process of the equipment, and reduces the requirements for the horizontal accuracy of the installation surface.

[0050] 2. The calibration target is convenient and controllable: the present invention uses a drone as a target, which avoids the problem that a calibration target of suitable size and distance cannot be selected in a complex field environment.

[0051] 3. High correction accuracy: The present invention calculates the distance between the UAV and the turntable and the observation field angle according to the actual accuracy requirements, thereby achieving controllable accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 A flow chart of an angle correction method for a turntable provided by the present invention.

[0053] Figure 2 Example of drone target imaging when acquiring a rectified image. DETAILED DESCRIPTION

[0054] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0055] The present invention provides an angle correction method for a turntable, which uses a drone as a correction target to correct the turntable's horizontal and pitch angles at different horizontal positions. The height and position information of the turntable to be corrected are obtained, the distance information between the drone as the correction target and the turntable and the observation field angle of the turntable are determined, the position information of the correction point is determined, the drone flies point by point according to the correction point position information, and the height is consistent with the height of the equipment. The turntable is controlled to track the drone according to the observation field angle, and the image of the drone at each correction point and the horizontal pitch angle of the turntable are collected. The turntable's horizontal and pitch angle correction values ​​at different horizontal positions are calculated according to the position of the drone in the image, and the turntable pitch angle correction value at any horizontal position is calculated by the interpolation method.

[0056] Among them, the turntable in the present invention is a video surveillance device that can rotate in the horizontal and pitch directions. The video surveillance device consists of a horizontal rotation axis system, a pitch rotation axis system, a horizontal angle encoder, a pitch angle encoder, a visible light camera, etc., and is widely used in the field of large-scene video surveillance.

[0057] See also Figure 1 To illustrate, the present invention provides a method for angle correction of a turntable, and its specific implementation process is as follows:

[0058] Step S1: Determine the calibration point information of the drone as a target object;

[0059] S1.1: Obtain the height and position information of the turntable installation;

[0060] The height is the horizontal plane height of the center point of the turntable visible light camera window, and the position information includes the latitude and longitude information of the turntable installation location.

[0061] S1.2: According to the calibration accuracy requirements and the size of the UAV, calculate the straight-line distance between the UAV and the turntable and the observation field of view of the turntable during calibration; the specific calculation formula for the straight-line distance D between the UAV and the turntable is as follows:

[0062] D = ALT_ERR / tan (α)

[0063] The specific calculation formula for the turntable observation field angle is as follows:

[0064] FOV=2*atan((L UVA *img_wid) / (2*N*D))

[0065] Among them, ALT_ERR represents the altitude error of the drone, which can be obtained according to the specification provided by the drone manufacturer; α represents the angle accuracy error limit of the correction, which can be determined according to actual needs; FOV represents the horizontal field of view angle used by the turntable to observe the drone during correction; L UVA represents the width of the UAV, img_wid represents the number of image columns of the turntable visible light camera, N represents the number of pixels of the UAV in the image level, and this parameter can be determined based on experience; D represents the straight-line distance between the UAV and the turntable.

[0066] S1.3: Use GIS to obtain the position information of the calibration point with a straight-line distance D from the turntable;

[0067] First, obtain the position information of the turntable installation position in the north direction and the straight-line distance D from the turntable as the first calibration point; with the turntable installation position as the center and the angle β with the turntable installation position in the north direction, determine the position information of the turntable in the straight-line distance D as the second calibration point; in this way, determine a calibration point with a straight-line distance D from the turntable at every interval angle β until the selection of M calibration points in a circle of 360 degrees is completed; wherein the interval angle β can be determined according to actual needs,

[0068] Step S2: The UAV flies point by point along the calibration point trajectory, the turntable is controlled to track the UAV, and the UAV image and the corresponding turntable angle information are collected;

[0069] S2.1: The coordinates of the calibration points are entered into the UAV flight trajectory in sequence;

[0070] S2.2: Control the drone to hover at the first calibration point in the flight trajectory. The flight altitude is the horizontal plane height of the center point of the turntable visible light camera window.

[0071] S2.3: Control the turntable to track the UAV according to the turntable's observation field of view;

[0072] The pitch angle of the turntable is set to 0 degrees, and the turntable is controlled to rotate horizontally until the drone is located in the column (center column) where the horizontal center point of the turntable visible light image is located. Figure 2 As shown, the first horizontal angle Hor1 of the current turntable and the first pitch pixel deviation shift_y1 of the center point of the drone target from the center point of the turntable visible light image are recorded; wherein, Figure 2As shown, the direction above the center point of the visible light image of the turntable is the positive direction, and the direction below the center point of the visible light image of the turntable is the negative direction;

[0073] S2.4: Repeat steps S2.2 to S2.3 to complete the acquisition of UAV target image data for M correction points.

[0074] Step S3: Calculate the turntable horizontal angle correction value and the turntable pitch angle correction values ​​at different horizontal positions according to the position of the drone target in the image;

[0075] S3.1: Calculate the turntable horizontal angle correction value. The specific calculation formula is as follows:

[0076] coor i =Hor i -i*β

[0077]

[0078] Among them, Hor i Indicates the horizontal angle of the turntable corresponding to the i-th calibration point, coor i represents the turntable horizontal angle correction value calculated by the i-th correction point, M represents the number of correction points, and coor represents the final turntable horizontal angle correction value.

[0079] S3.2: Calculate the horizontal angle Hor of the uncorrected turntable i The pitch angle correction value of the turntable is calculated as follows:

[0080] pit i =atan(2*shift_y i *tan(FOV*img_hei / (2*img_wid)) / img_hei)

[0081] Among them, pit i Indicates the uncorrected turntable horizontal angle Hor i The pitch angle correction value of the turntable at position, shift_y i It represents the pitch pixel deviation of the UAV target center point from the center point of the turntable visible light image at the i-th calibration point, img_hei represents the number of image rows of the turntable visible light camera, img_wid represents the number of image columns of the turntable visible light camera, FOV represents the horizontal field of view used by the turntable to observe the UAV during calibration, and i represents the calibration point sequence number.

[0082] Step S4: Generate the turntable pitch angle correction value at any horizontal position using the interpolation method. The specific calculation formula is as follows:

[0083]

[0084] Where Hor represents the uncorrected horizontal angle of any turntable pitch correction value to be determined, satisfying Hor k ≤Hor≤Hor k+1 , 1≤k≤M, Hor k Indicates the horizontal angle of the turntable corresponding to the kth correction point, Hor k+1 represents the horizontal angle of the turntable corresponding to the k+1th correction point; pit k Indicates the horizontal angle of the turntable Hor k The turntable pitch angle correction value at k+1 Indicates the horizontal angle of the turntable Hor k+1 The turntable pitch angle correction value at ; * indicates a multiplication operation.

[0085] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for angle correction of a turntable, characterized in that: The following steps are involved: Step S1: Determine the calibration point information of the drone as a target object; Step S2: The UAV flies sequentially to each calibration point, and controls the turntable to collect the UAV image data of the calibration point; Step S3: Calculate the turntable horizontal angle correction value and the turntable pitch angle correction values ​​at different horizontal positions according to the position of the drone target in the image; Step S4: Generate a turntable pitch angle correction value at any horizontal position using an interpolation method.

2. The method for angle correction of a turntable according to claim 1, characterized in that: The specific implementation process of step S1 is as follows: S1.1: Obtain the height and position information of the turntable installation; S1.2: Calculate the straight-line distance between the UAV and the turntable and the turntable's observation field of view during calibration based on the calibration accuracy requirements and the size of the UAV; S1.3: Use GIS to obtain the position information of the calibration point with a straight-line distance D from the turntable.

3. The angle correction method for a turntable according to claim 2, characterized in that: In step S1.1, the installation height of the turntable is the horizontal plane height of the center point of the turntable visible light camera window, and the position information includes the latitude and longitude information of the turntable installation position.

4. The angle correction method for a turntable according to claim 2, characterized in that: In step S1.2, the calculation formula for the straight-line distance D between the drone and the turntable is: D = ALT_ERR / tan (α) The calculation formula of the turntable observation field angle is: FOV=2*wall((L UVA *img_wid) / (2*N*D)) Among them, ALT_ERR represents the altitude error of the UAV; α represents the angle accuracy error limit of the correction; FOV represents the horizontal field of view angle used by the turntable to observe the UAV during correction; L UVA represents the width of the drone, img_wid represents the number of image columns of the turntable visible light camera, N represents the number of pixels of the drone's horizontal imaging; D represents the straight-line distance between the drone and the turntable.

5. The method for angle correction of a turntable according to claim 2, characterized in that: In step S1.3, first obtain the position information of the turntable installation position in the north direction and the straight-line distance D from the turntable as the first correction point; with the turntable installation position as the center of the circle and the angle β with the north direction of the turntable installation position, determine the position information of the turntable in the straight-line distance D as the second correction point; in this way, determine a correction point with a straight-line distance D from the turntable at every interval angle β until the selection of M correction points in a circle of 360 degrees is completed.

6. The method for angle correction of a turntable according to claim 1, characterized in that: The specific implementation process of step S2 is as follows: S2.1: The coordinates of the calibration points are entered into the UAV flight trajectory in sequence; S2.2: Control the drone to hover at the first calibration point in the flight trajectory. The flight altitude is the horizontal plane height of the center point of the turntable visible light camera window. S2.3: Control the turntable to track the UAV according to the turntable's observation field of view; S2.4: Repeat steps S2.2 to S2.3 to complete the acquisition of UAV target image data for M correction points.

7. The method for angle correction of a turntable according to claim 6, characterized in that: In step S2.3, the pitch angle of the turntable is set to 0 degrees, and the turntable is controlled to rotate horizontally until the drone is located in the column where the horizontal center point of the turntable visible light image is located, and the current turntable first horizontal angle Hor1 and the first pitch pixel deviation shift_y1 of the drone target center point from the center point of the turntable visible light image are recorded.

8. The method for angle correction of a turntable according to claim 1, characterized in that: In step S3, the calculation formula of the turntable horizontal angle correction value is: coor i =Hor i -i*β Among them, Hor i Indicates the horizontal angle of the turntable corresponding to the i-th calibration point, coor i represents the turntable horizontal angle correction value calculated by the i-th correction point, M represents the number of correction points, and coor represents the final turntable horizontal angle correction value.

9. The method for angle correction of a turntable according to claim 1, characterized in that: In step S3, the calculation formula of the turntable pitch angle correction value at different horizontal positions is: pit i =atan(2*shift_y i *tan(FOV*img_hei / (2*img_wid)) / img_hei) Among them, pit i Indicates the uncorrected turntable horizontal angle Hor i The pitch angle correction value of the turntable at position, shift_y i It represents the pitch pixel deviation of the UAV target center point from the center point of the turntable visible light image at the i-th calibration point, img_hei represents the number of image rows of the turntable visible light camera, img_wid represents the number of image columns of the turntable visible light camera, FOV represents the horizontal field of view used by the turntable to observe the UAV during calibration, and i represents the calibration point sequence number.

10. The method for angle correction of a turntable according to claim 1, characterized in that: In step S4, the calculation formula of the turntable pitch angle correction value at any horizontal position is: Where Hor represents the uncorrected horizontal angle of any turntable pitch correction value to be determined, satisfying Hor k ≤Hor≤Hor k+1 , 1≤k≤M, Hor k Indicates the horizontal angle of the turntable corresponding to the kth correction point, Hor k+1 represents the horizontal angle of the turntable corresponding to the k+1th correction point; pit k Indicates the horizontal angle of the turntable Hor k The turntable pitch angle correction value at k+1 Indicates the horizontal angle of the turntable Hor k+1 The turntable pitch angle correction value at ; * indicates a multiplication operation.

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