Contour perception and digital modeling method of paddy field hard bottom layer

Abstract

The present invention relates to a method for sensing and digitally modeling the contours of a hard substratum in a paddy field. The method comprises the following steps: S1, using GNSS and AHRS to acquire position and attitude data of a wheeled agricultural machine during travel; S2, performing coordinate transformation based on the relative positions of the installed GNSS and AHRS and the rear wheels of the agricultural machine to acquire the coordinate values of a point set in the coordinate system at the contact points between the wheel base and the hard substratum; and S3, uniformly diluting the point set and performing triangulation to construct a three-dimensional contour of the substratum; and S4, extracting specific triangles containing estimated points based on the ray method and the point-surface intersection principle to estimate the elevation of any point in the entire hard substratum. The present invention can sense the contour information of hard substratums such as paddy fields and mountainous areas, and has the characteristics of strong versatility, high efficiency, and high accuracy. It enriches topographic mapping and expression methods and belongs to the field of intelligent agricultural machinery and intelligent sensing technology.

Description

Technical Field

[0001] The present invention relates to the field of intelligent agricultural machinery and equipment and intelligent sensing technology, and in particular to a method for sensing and digitally modeling the contour of a paddy field hard bottom layer. Background Art

[0002] Paddy field hardness significantly impacts the driving and operating quality of paddy field machinery. Tractors navigate the unevenly deep, unevenly ravines and ditches of the paddy field hardness, causing frequent tractor movements and impacting both tractor driving accuracy and implement precision, leading to suboptimal operation. This, to a certain extent, restricts the widespread adoption of agricultural machinery, particularly intelligent agricultural machinery. Therefore, perceiving and constructing the three-dimensional contours of the paddy field hardness is crucial for enabling intelligent, precise, and efficient operations for paddy field machinery, providing a healthy tillage layer for rice growth and minimizing damage to the rice caused by mechanical operations.

[0003] Traditional methods primarily use a soil compaction meter to intermittently measure soil hardness at different depths, or remotely map the field surface using telemetry equipment. Lightweight, portable equipment is also available for on-site sampling and analysis of soil moisture and nutrient content. As agricultural machinery becomes more automated and intelligent, automated navigation operations are placing higher demands on the perception of hard ground and the representation of its contour characteristics.

[0004] At present, there are several research results on terrain acquisition, such as: CN102607499A discloses a vehicle-mounted three-dimensional farmland topography measurement device, which can be used to measure the surface topography of dry land and paddy fields; CN102788566B discloses a soil surface roughness measurement plate and measurement method, which uses machine vision and image processing technology to obtain the soil surface roughness by calculating the length of probes arranged on the soil surface; CN203100958U discloses a disc-type soil resistance continuous and rapid measurement device, which can continuously measure the soil resistance at a certain depth and infer the bearing capacity of soil at different depths; CN103918365B discloses a deep tillage shovel that can continuously measure the mechanical resistance of the soil and can monitor the arable land resistance of the deep tillage shovel online. If the shovel encounters foreign objects and the resistance exceeds the set threshold, the hydraulic cylinder contracts to make the shovel avoid it.

[0005] However, existing terrain information perception devices and methods still have the following technical problems:

[0006] (1) The structure of paddy fields is complex, with the hard bottom layer covered by the tillage layer and the water layer. Traditional sensing devices focus more on collecting soil surface characteristics and cannot directly sense the hard layer through the tillage layer and the water layer.

[0007] (2) Traditional contact topographic measurement devices mainly use discrete point measurement, which cannot meet the needs of rapid and continuous measurement of hard stratum contour data in large fields.

[0008] (3) Traditional soil information measures soil resistance or cultivated land resistance to indirectly infer the bearing capacity of soil at different depths, but cannot directly measure the height of the hard ground layer or express the overall terrain contour characteristics. Summary of the Invention

[0009] In response to the technical problems existing in the prior art, the purpose of the present invention is to provide a method for perceiving and digitally modeling the contours of the hard bottom layer of paddy fields, realize the mapping and digital modeling of the hard strata of paddy fields, enrich the means of terrain mapping and expression, and provide a reference map of the walking environment for agricultural machinery operating in paddy fields.

[0010] In order to achieve the above object, the present invention adopts the following technical solutions:

[0011] A method for perceiving and digitally modeling the contour of a paddy field hard bottom layer, wherein the method for perceiving the contour of a paddy field hard bottom layer comprises the following steps:

[0012] S1. Use GNSS and AHRS to obtain the position and attitude data of wheeled agricultural machinery during driving;

[0013] S2. Based on the relative positions of the installed GNSS and AHRS and the rear wheels of the agricultural machinery, coordinate transformation is performed to obtain the coordinate values of the contact points between the wheel bottom and the hard bottom layer in the coordinate system;

[0014] The digital modeling method for the paddy field hard bottom contour includes the following steps:

[0015] S3, evenly dilute the point set and perform triangulation to construct the underlying three-dimensional contour;

[0016] S4. Based on the ray method and the point-surface intersection principle, the specific triangle containing the estimated point is extracted to estimate the elevation of any point in the entire hard bottom layer.

[0017] As a preferred embodiment, step S1 is: the GNSS main antenna installed on the agricultural machinery body obtains the longitude, latitude and sea level of its center point in the geodetic coordinate system; and obtains the XYZ coordinates of the main antenna in the local tangent plane coordinate system ENU of the earth through Gaussian projection.

[0018] As a preferred embodiment, in step S1, the XYZ coordinates of the main antenna in the Earth local tangent plane coordinate system ENU are calculated using the following formula:

[0019]

[0020] Where X is the meridian arc length, m; L is the longitude of point A in the geodetic coordinate system, °; L0 is the longitude of the central meridian; B is the latitude of point A in the geodetic coordinate system, °; N is the radius of curvature of the meridian, m; N, ρ″, t, η are intermediate variables;

[0021] The calculation formula of meridian arc length X is as follows:

[0022]

[0023] a0, a2, a4, a6, and a8 are basic constants and are calculated using the following formula:

[0024]

[0025] m0, m2, m4, m6, m8 are calculated using the following formula:

[0026]

[0027] Where e is the first eccentricity of the ellipsoid, a is the major axis of the ellipsoid, and is taken as a = 6378137m; b is the minor axis of the ellipsoid, and is taken as b = a·(1-f); f is the flattening of the ellipsoid, and is taken as f = 1 / 298.257223563;

[0028] In formula (1), N, ρ″, t, and η are calculated according to the following formula:

[0029]

[0030] Where, e' is the second eccentricity of the ellipsoid,

[0031] As a preferred embodiment, in step S1, the AHRS is installed on the frame of the vehicle body to obtain the pitch and roll angles of the agricultural machinery body.

[0032] As a preference, step S2 includes:

[0033] S21. Use a high-precision total station to measure the spatial positions of the master and slave antennas relative to the power chassis, measure the heading installation error, and perform heading correction;

[0034] S22. Use a level to measure the roll and pitch angles of the power chassis, compare them with the data obtained by the AHRS to obtain the system error value, and then perform roll and pitch angle correction;

[0035] S23. Establish a three-dimensional coordinate system parallel to the power chassis with the main antenna as the coordinate origin, and obtain the coordinate values of the left and right wheel bases in the local tangent plane coordinate system ENU of the earth through Euler transformation.

[0036] As a preferred embodiment, in step S23, the calculation formula is:

[0037]

[0038] Where △x is the coordinate increment from the wheel center to the wheel base in the X-axis direction, △y is the coordinate increment from the wheel center to the wheel base in the Y-axis direction, △z is the coordinate increment from the wheel center to the wheel base in the Z-axis direction, and θ is the vehicle body pitch angle;

[0039]

[0040] Where B rp It is the contact point between the bottom of the right wheel and the ground;

[0041]

[0042]

[0043] T B =R·B rp +G d (9)

[0044] Where, T B is the coordinate of point B at the bottom of the right wheel in the local tangent plane coordinate system after Euler transformation, R is the transformation matrix from the point set of the vehicle coordinate system to the coordinate of the local tangent plane coordinate system, R z is the rotation matrix around the Z axis, R y is the rotation matrix around the Y axis, R x is the rotation matrix around the X axis.

[0045] As a preference, step S3 is:

[0046] The obtained coordinate values of the left and right wheel bottom points are used to remove noise points using the Laida criterion. Then, the left and right wheel bottom coordinate points are diluted with equal spacing. The diluted points are subjected to Delaunay triangulation using the Bowyer-Watson method to draw the digital model of the paddy field hard bottom contour. The contour triangle facet point sequence matrix T is extracted and constructed. The expression is:

[0047]

[0048] As a preference, step S4 is:

[0049] Assume that the vertices of the i-th triangle representing the hard bottom contour in the i-th row of matrix T are P i1 (x i1 ,y i1 ,z i1 ), P i2 (x i2 ,y i2 ,z i2 ) and P i3 (x i3 ,y i3 ,z i3 ), let the position of the jth point to be estimated be P j0 (x j0 ,y j0) Search for the specific triangular face where the point falls within the constructed hard bottom layer contour, and extract the vertex numbers of the specific triangular face, which are the three elements of a specific row of the T matrix. The extraction basis is:

[0050]

[0051] In the formula, k i1 is the slope of the first side of the i-th triangle, k i2 is the slope of the second side of the i-th triangle, k i3 is the slope of the third side of the i-th triangle;

[0052] When the ray drawn upward from the j-th point to be estimated intersects exactly one of the three sides of the triangle, that is, it satisfies x i1 ≤x j0 <xi2 or x i2 ≤x j0 <x i1 and y j0 ≤k i1 (x j0 -x i1 )+y i1 condition, then this triangle is the specific triangle containing the estimated point; calculate the z j0 value of this point according to the plane expression of the point in the plane, which is the elevation information of this point. The elevation information z j0 of any point calculation formula:

[0053]

[0054]

[0055] In the formula, A, B, C, a, b, c, d are all process quantities, and z j0 is the elevation of the estimated point.

[0056] The present invention has the following advantages:

[0057] 1. The present invention can sense the contour information of hard bottom layers such as paddy fields and mountains, with the characteristics of strong versatility, high efficiency, high accuracy, etc. It realizes the mapping and digital modeling of the hard bottom layer contour of paddy fields, and enriches the means of topographic mapping and expression.

[0058] 2. The method for sensing and digital modeling of the hard bottom layer contour of paddy fields in the present invention uses an unmanned wheeled agricultural machine or a traditional wheeled agricultural machine as the power walking chassis, with the characteristics of convenient sensor installation, convenient operation, strong universality, etc. It can well adapt to paddy field operations and directly sense through the tillage layer and water layer to contact the hard bottom layer.

[0059] 3. The paddy field hard bottom contour perception and digital modeling method of the present invention breaks through the limitation of low efficiency of discrete point measurement of traditional contact topographic measurement devices. The use of continuous wheel bottom perception can meet the needs of fast and continuous measurement of hard bottom contour data of large plots.

[0060] 4. The paddy field hard bottom contour perception and digital modeling method of the present invention can directly measure the hard bottom height and express the overall terrain contour characteristics, enriching the terrain surveying and mapping methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 It is a flow chart of the method of the present invention.

[0062] Figure 2 It is a schematic diagram of the installation of the agricultural machinery body and AHRS according to the method of the present invention.

[0063] Figures 3a-3c This is a relationship diagram between the wheel bottom collection point and the positioning antenna position in the method of the present invention.

[0064] Figure 4 It is a schematic diagram of the process of constructing the three-dimensional contour of the paddy field hard bottom layer according to the method of the present invention.

[0065] Figure 5a Schematic diagram of the relationship between the estimated point position and the i-th triangle position of the method of the present invention.

[0066] Figure 5b Schematic diagram of estimating the elevation of any point in the entire hard bottom layer according to the method of the present invention.

[0067] Among them, 1 is the AHRS, 2 is the wheeled power chassis, 3 is the GNSS master antenna, 4 is the GNSS slave antenna, 5 is the right wheel bottom, 6 is the left wheel bottom, 7 is the mud surface, and 8 is the hard bottom layer. DETAILED DESCRIPTION

[0068] The present invention will be further described in detail below with reference to specific implementation methods.

[0069] The method for perceiving and digitally modeling the contour of a paddy field hard bottom layer comprises a method for perceiving the contour of a paddy field hard bottom layer and a method for digitally modeling the contour of a paddy field hard bottom layer, wherein the method for perceiving the contour of a paddy field hard bottom layer comprises steps S1 and S2, such as Figure 1 、 2 , 3a-3c. The digital modeling method of the paddy field hard bottom contour includes steps S3 and S4, as shown in FIG. Figure 1 、 4 , 5a, 5b.

[0070] The wheeled agricultural machinery used in this invention is a Yanmar 2ZGQ-6G (VP6) riding rice transplanter. The GNSS (Global Navigation Satellite System) system, model Sinan K528, includes a master antenna and a slave antenna. The master antenna is mounted on the right side of the vehicle's front for positioning, while the slave antenna, connected to the master antenna, is mounted on the left side of the vehicle's front for orientation. An MTi-300 AHRS (Attitude Reference System) is fixed to the vehicle frame.

[0071] The steps are as follows:

[0072] S1. Use GNSS and AHRS to obtain the position and attitude data of the wheeled agricultural machinery during driving. Specifically:

[0073] like Figure 2 、 Figures 3a-3c As shown in the figure, the GNSS main antenna installed on the agricultural machinery body obtains the longitude, latitude and sea level of its center point in the geodetic coordinate system; the XYZ coordinates of the main antenna in the Earth's local tangent plane coordinate system (ENU) are obtained through Gaussian projection. Calculation formula:

[0074]

[0075] Wherein, X is the meridian arc length, m; L is the longitude of point A in the geodetic coordinate system, °; L0 is the longitude of the central meridian, which is 113° in this embodiment; B is the latitude of point A in the geodetic coordinate system, °; N is the meridian curvature radius, m; N, ρ″, t, and η are intermediate variables;

[0076] The calculation formula of meridian arc length X is as follows:

[0077]

[0078] a0, a2, a4, a6, and a8 are basic constants and are calculated using the following formula:

[0079]

[0080] m0, m2, m4, m6, m8 are calculated using the following formula:

[0081]

[0082] Where e is the first eccentricity of the ellipsoid, a is the semi-major axis of the ellipsoid, and is taken as a=6378137m; b is the semi-minor axis of the ellipsoid, and is taken as b=a·(1-f); f is the flattening of the ellipsoid, and is taken as f=1 / 298.257223563.

[0083] In formula (1), N, ρ″, t, and η are calculated according to the following formula:

[0084]

[0085] Where, e' is the second eccentricity of the ellipsoid,

[0086] The AHRS is installed on the frame of the vehicle body to obtain the pitch and roll angles of the agricultural machinery body.

[0087] S2. Based on the relative positions of the installed GNSS and AHRS and the rear wheels of the agricultural machinery, coordinate transformation is performed to obtain the coordinate values of the contact points between the wheel bottom and the hard bottom layer in the coordinate system. Specifically:

[0088] S21. Use a high-precision total station to measure the spatial positions of the master and slave antennas relative to the power chassis, measure the heading installation error, and perform heading correction;

[0089] S22. Use a level to measure the roll and pitch angles of the power chassis, compare them with the data obtained by the AHRS to obtain the system error value, and perform roll and pitch angle correction;

[0090] S23. Establish a three-dimensional coordinate system parallel to the power chassis with the main antenna as the coordinate origin, and obtain the coordinate values of the left and right wheel bases in the local tangent plane coordinate system (ENU) through Euler transformation. Calculation formula:

[0091]

[0092] Where △x is the coordinate increment from the wheel center to the wheel base in the X-axis direction, △y is the coordinate increment from the wheel center to the wheel base in the Y-axis direction, △z is the coordinate increment from the wheel center to the wheel base in the Z-axis direction, and θ is the vehicle body pitch angle.

[0093]

[0094] Where B rp It is the contact point between the bottom of the right wheel and the ground.

[0095]

[0096]

[0097] T B =R·B rp +G d (9)

[0098] Where, T B is the coordinate of point B at the bottom of the right wheel in the local tangent plane coordinate system after Euler transformation, R is the transformation matrix from the point set of the vehicle coordinate system to the coordinate of the local tangent plane coordinate system, R z is the rotation matrix around the Z axis, R y is the rotation matrix around the Y axis, R x is the rotation matrix around the X axis.

[0099] S3. Uniformly dilute the point set and perform triangulation to construct the underlying three-dimensional contour. Specifically:

[0100] As Figure 4 shown, using the coordinate values of the left and right wheel bottom point sets obtained, first remove the noise points through the Leida criterion, then dilute the left and right wheel bottom coordinate points at equal intervals, perform Delaunay triangulation on the diluted points through the Bowyer - watson method, draw the digital model of the paddy field hard bottom layer contour, and extract and construct the contour triangle patch point sequence matrix T. The expression form is:

[0101]

[0102] S4. Based on the ray method and the point - plane intersection principle, extract the specific triangle containing the estimated point and estimate the elevation of any point in the entire hard bottom layer area. Specifically:

[0103] As Figure 5a-5b shown, let the vertices of the i - th triangle forming the hard bottom contour represented by the i - th row of the matrix T be P i1 (x i1 , y i1 , z i1 ), P i2 (x i2 , y i2 , z i2 ), and P i3 (x i3 , y i3 , z i3 ). Let the position of the j - th point to be estimated be P j0 (x j0 , y j0 ), search for the specific triangular face in the constructed hard bottom layer contour where this point falls, extract the vertex numbers of the specific triangular face, that is, the three elements of the specific row of the T matrix. The extraction basis is:

[0104]

[0105] In the formula, k i1 is the slope of the first side of the i - th triangle, k i2 is the slope of the second side of the i - th triangle, k i3 is the slope of the third side of the i - th triangle. [[ID=​​​​​​​​​i1 (x j0 -x i1 )+y i1 Condition, the triangle is a specific triangle containing the estimated point. Calculate the z of the point according to the plane expression of the point in the plane. j0 The value is the elevation information of the point. j0 Calculation formula:

[0107]

[0108]

[0109] In the formula, A, B, C, a, b, c, d are all process quantities, z j0 Estimated point elevation.

[0110] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for perceiving and digitally modeling the contours of a paddy field hard bottom layer, characterized in that: The method for sensing the contour of the paddy field hard bottom layer includes the following steps: S1. Use GNSS and AHRS to obtain the position and attitude data of wheeled agricultural machinery during driving; S2. Based on the relative positions of the installed GNSS and AHRS and the rear wheels of the agricultural machinery, coordinate transformation is performed to obtain the coordinate values of the contact points between the wheel bottom and the hard bottom layer in the coordinate system; The digital modeling method of paddy field hard bottom contour includes the following steps: S3, evenly dilute the point set and perform triangulation to construct the underlying three-dimensional contour; S4. Based on the ray method and the point-surface intersection principle, the specific triangle containing the estimated point is extracted to estimate the elevation of any point in the entire hard bottom layer.

2. The method for sensing and digitally modeling the contour of the paddy field hard bottom layer according to claim 1, characterized in that: Step S1 is: the GNSS main antenna installed on the agricultural machinery body obtains the longitude, latitude and sea level of its center point in the geodetic coordinate system; and obtains the XYZ coordinates of the main antenna in the local tangent plane coordinate system ENU of the earth through Gaussian projection.

3. The method for sensing and digitally modeling the contour of a paddy field hard bottom layer according to claim 2, characterized in that: In step S1, the XYZ coordinates of the main antenna in the Earth's local tangent plane coordinate system ENU are calculated as follows: Where X is the meridian arc length, m; L is the longitude of point A in the geodetic coordinate system, °; L0 is the longitude of the central meridian; B is the latitude of point A in the geodetic coordinate system, °; N is the radius of curvature of the meridian, m; N, ρ″, t, η are intermediate variables; The calculation formula of meridian arc length X is as follows: a0, a2, a4, a6, and a8 are basic constants and are calculated using the following formula: m0, m2, m4, m6, m8 are calculated using the following formula: Where e is the first eccentricity of the ellipsoid, a is the major axis of the ellipsoid, and is taken as a = 6378137m; b is the minor axis of the ellipsoid, and is taken as b = a·(1-f); f is the flattening of the ellipsoid, and is taken as f = 1 / 298.257223563; In formula (1), N, ρ″, t, and η are calculated according to the following formula: Where, e' is the second eccentricity of the ellipsoid, 4. The method for sensing and digitally modeling the contour of a paddy field hard bottom layer according to claim 2, characterized in that: In step S1, the AHRS is installed on the frame of the vehicle body to obtain the pitch and roll angles of the agricultural machinery body.

5. The method for sensing and digitally modeling the contour of the paddy field hard bottom layer according to claim 1, characterized in that: Step S2 includes: S21. Use a high-precision total station to measure the spatial positions of the master and slave antennas relative to the power chassis, measure the heading installation error, and perform heading correction; S22. Use a level to measure the roll and pitch angles of the power chassis, compare them with the data obtained by the AHRS to obtain the system error value, and perform roll and pitch angle correction; S23. Establish a three-dimensional coordinate system parallel to the power chassis with the main antenna as the coordinate origin, and obtain the coordinate values of the left and right wheel bases in the local tangent plane coordinate system ENU of the earth through Euler transformation.

6. The method for sensing and digitally modeling the contour of a paddy field hard bottom layer according to claim 5, characterized in that: In step S23, the calculation formula is: Where △x is the coordinate increment from the wheel center to the wheel base in the X-axis direction, △y is the coordinate increment from the wheel center to the wheel base in the Y-axis direction, △z is the coordinate increment from the wheel center to the wheel base in the Z-axis direction, and θ is the vehicle body pitch angle; Where B rp It is the contact point between the bottom of the right wheel and the ground; T B =R·B rp +G d (9) Where, T B is the coordinate of point B at the bottom of the right wheel in the local tangent plane coordinate system after Euler transformation, R is the transformation matrix from the point set of the vehicle coordinate system to the coordinate of the local tangent plane coordinate system, R z is the rotation matrix around the Z axis, R y is the rotation matrix around the Y axis, R x is the rotation matrix around the X axis.

7. The method for sensing and digitally modeling the contour of the paddy field hard bottom layer according to claim 1, characterized in that: Step S3 is: The obtained coordinate values of the left and right wheel bottom points are used to remove noise points using the Laida criterion. Then, the left and right wheel bottom coordinate points are diluted with equal spacing. The diluted points are subjected to Delaunay triangulation using the Bowyer-Watson method to draw the digital model of the paddy field hard bottom contour. The contour triangle facet point sequence matrix T is extracted and constructed. The expression is:

8. The method for sensing and digitally modeling the contour of the paddy field hard bottom layer according to claim 7, characterized in that: Step S4 is: Assume that the vertices of the i-th triangle representing the hard bottom contour in the i-th row of matrix T are P i1 (x i1 ,y i1 ,z i1 ), P i2 (x i2 ,y i2 ,z i2 ) and P i3 (x i3 ,y i3 ,z i3 ), let the position of the jth point to be estimated be P j0 (x j0 ,y j0 ), search for the specific triangular face where the point falls within the constructed hard bottom contour, and extract the vertex number of the specific triangular face, that is, the three elements of the specific row of the T matrix. The extraction basis is: Where k i1 is the slope of the first side of the i-th triangle, k i2 is the slope of the second side of the i-th triangle, k i3 is the slope of the third side of the i-th triangle; When the ray drawn upward from the jth point to be estimated intersects with one and only one of the three sides of the triangle, it satisfies x i1 ≤x j0 < xi2 or x i2 ≤x j0 <x i1 And y j0 ≤k i1 (x j0 -x i1 )+y i1 Condition, the triangle is a specific triangle containing the estimated point; calculate the z of the point according to the plane expression of the point in the plane j0 The value is the elevation information of the point, and the elevation information of any point z j0 Calculation formula: In the formula, A, B, C, a, b, c, d are all process quantities, z j0 Estimated point elevation.

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