A positioning system for farmland mapping

Abstract

The invention discloses a positioning system for farmland mapping, comprising a chassis, a control component, a laser adjustment device, a laser emitting and receiving device and a laser signal feedback device; the positioning system comprises the following steps when performing positioning: S1: starting work, an operator sends a motion instruction and a predetermined path to the control component, the control component drives the chassis to walk in the farmland, and starts the laser emitting and receiving device and the laser adjustment device; S2: the laser adjustment device automatically adjusts the height of the laser emitting and receiving device, so that the laser emission center line of the laser emitting and receiving device is always flush with the center line of the laser signal feedback device; S3: using the Kalman filter KEF algorithm, calculating the posture and covariance matrix Q of the observation model mapping in the current state space of the chassis, so as to update the state space, thereby obtaining the posture of the current chassis to establish a two-dimensional map of the farmland.

Description

Technical Field

[0001] The present invention relates to the technical field of farmland mapping, and more specifically, to a positioning system for farmland mapping. Background Art

[0002] With the development of agricultural technology, machine labor is gradually adopted in farmland labor to replace traditional manual labor, which greatly improves productivity. However, there are still many immature technologies in machine labor. For example, most of the machine navigation and mapping positioning on the market currently use a combination of GPS and IMU technologies. However, since the GPS signal reception is relatively poor in remote mountainous areas, using GPS and IMU cannot achieve precise positioning, which limits people's use. Summary of the Invention

[0003] The present invention aims to overcome at least one defect (shortcoming) of the above-mentioned prior art, and provides a positioning system for farmland mapping, which is used to solve the precise positioning problem of generating a two-dimensional map of farmland machines on farmland, so as to be popularized and used in hilly and mountainous areas.

[0004] To solve the above technical problems, the technical solution adopted by the present invention is:

[0005] A positioning system for farmland mapping includes a chassis, a control component, a laser adjustment device, a laser emission and reception device, and a laser signal feedback device;

[0006] The chassis is used to provide support and power for the entire positioning system;

[0007] The control component is arranged in the chassis and is used to control the entire positioning system and perform information interaction;

[0008] The laser adjustment device is arranged above the chassis and is electrically connected to the control component, and is used to perform information interaction with the control component;

[0009] The laser emission and reception device is arranged above the laser adjustment device, and is used to emit or receive laser, and is electrically connected to the laser adjustment device to adjust the up and down displacement through the laser adjustment device;

[0010] The laser signal feedback device includes several and is arranged at the boundary of the farmland to be mapped, and is used to feedback the laser to the laser emission and reception device to prompt the laser height emitted by the laser emission and reception device;

[0011] When the positioning system performs positioning, it includes the following steps:

[0012] S1: Start the operation. The operator sends motion instructions and a predetermined path to the control component. The control component drives the chassis to move in the farmland and activates the laser emission and reception device and the laser adjustment device.

[0013] S2: The laser adjustment device automatically adjusts the height of the laser emission and reception device so that the laser emission center line of the laser emission and reception device is always flush with the center line of the laser signal feedback device.

[0014] S3: Use the Kalman filter KEF algorithm to calculate the pose and covariance matrix Q of the current mapping of the chassis to establish a two-dimensional map of the farmland.

[0015] In this technical solution, the operator remotely controls the chassis and activates the laser emission and reception device and the laser adjustment device to scan the point cloud of the farmland boundary with the laser emission and reception device to generate a map, and use the laser signal feedback device to obtain the current positioning of the chassis in the map to achieve mapping and positioning simultaneously.

[0016] Specifically, the setting position of the laser signal feedback device on the farmland boundary is not limited, and it can be randomly set at the farmland boundary where mapping or control is required.

[0017] Specifically, in step S1, by driving the chassis to move in the farmland and activating the laser emission and reception device and the laser adjustment device, mapping and positioning are carried out in the farmland. Specifically, the laser emission and reception device scans the surrounding environment of the farmland at a certain frequency of 360° to emit a light beam to the surrounding laser signal feedback devices and receive the laser beam reflected from the laser signal feedback devices, so as to obtain the specific coordinates and azimuths of the surrounding laser signal feedback devices, and thus carry out mapping and positioning in the farmland.

[0018] In step S3, through the positioning method obtained in step S1, the specific coordinates and azimuths of the surrounding laser signal feedback devices can be obtained, so as to calculate the coordinates and covariance matrix in the current state space of the chassis, and thus establish a farmland map.

[0019] Further, in step S2, the specific steps for the laser adjustment device to automatically adjust the height of the laser emission and reception device are as follows:

[0020] S21: The laser emission and reception device continuously emits laser to the laser signal feedback device. The laser signal feedback device reflects the laser back to the laser emission and reception device. The laser emission and reception device judges the displacement ΔZmm of the chassis in the vertical direction and the coordinate information of each laser signal feedback device relative to the chassis by detecting the positions of the emitted and received lasers, and transmits the displacement information and coordinate information to the laser adjustment device.

[0021] S22: After receiving the displacement information transmitted by the laser emission and reception device, the laser adjustment device moves upward or downward by ΔZ mm according to the displacement information. The laser emission and reception device moves along with the movement of the laser adjustment device, so that the laser emission center line of the laser emission and reception device is flush with the center line of the laser signal feedback device.

[0022] During the operation in the farmland, due to the presence of stones, small slopes or small pits in the farmland, the surface of the farmland is uneven, which may cause the laser emission and reception device to have upward and downward displacements during operation, resulting in the laser emission center line of the laser emission and reception device not being flush with the center line of the laser signal feedback device. In this technical solution, the displacement of the laser emission and reception device is automatically adjusted by the laser adjustment device, so that the laser emission center line of the laser emission and reception device always coincides with the center line of the laser signal feedback device, so that the laser is in the best reflection and reception state, thereby enabling the laser emission and reception device to more effectively receive the information of the laser signal feedback device.

[0023] Further, in step S3, the specific calculation steps for calculating the pose and covariance matrix Q of the current map building of the chassis are as follows:

[0024] S31: Obtain the initial state space parameters of the chassis and calculate the covariance prediction equation of the chassis at time t;

[0025] S32: Compile the observation model and calculate the total Jacobian matrix of the observation with respect to the state space;

[0026] S33: Calculate the gain and update the covariance and state space.

[0027] Further, in step S31, the specific steps for obtaining the initial state space parameters of the chassis and calculating the covariance prediction equation of the chassis at time t are as follows:

[0028] Establish a coordinate system with the chassis as the center, and set the current pose of the chassis as x, y, θ; where x is the coordinate of the chassis on the x-axis, y is the coordinate of the chassis on the y-axis, and θ is the rotation angle of the chassis;

[0029] Set that there are N reflective columns in the current state space, and set to be the x and y coordinates of the Nth reflective column; where N > 0. At this time, the state space coordinate set X of the N reflective columns relative to the current pose of the chassis is:

[0030]

[0031] Set the initial pose of the chassis as x 0 , y 0 , θ 0 ; then at the t-th moment, the pose of the chassis is xt , y t , θ t ; Set the linear velocity σ of the chassis wheel speedometer v and the angular velocity σ ω both follow a Gaussian distribution with a mean of 0. According to the covariance calculation formula:

[0032]

[0033] At the initial moment, the covariance ∑ controlled by the chassis wheel speedometer can be obtained ξ，0 as:

[0034]

[0035] where, set ∑ x , ∑ y , ∑ θ The initial value is 1;

[0036] At the t-th moment, the covariance ∑ of the chassis wheel speedometer control t is:

[0037]

[0038] After calculation, the covariance prediction equation ∑ of the state quantity at the t-th moment t is:

[0039]

[0040] where, G ξ，t is the Jacobian matrix of the motion model with respect to the robot pose ξ t-1 ;

[0041]

[0042] G u is the Jacobian matrix of the motion model with respect to the control (linear velocity and angular velocity of the wheel speedometer);

[0043]

[0044] Furthermore, in step S32, the specific calculation steps for writing the observation model and calculating the total Jacobian matrix of the observation with respect to the state space are as follows:

[0045] Set that there are K groups of laser signal feedback devices detected on the farmland by the current laser emission and reception device, and set the coordinate information of the K groups of laser signal feedback devices to be respectively

[0046] Determine the relevance through data association: Among them, when the coordinates of the laser signal feedback device in the state space can be displaced and rotated to obtain the coordinates of the laser signal feedback device in the current laser emission and reception device, it indicates relevance; otherwise, it is irrelevant; set the laser signal feedback device found to be relevant in the state space as group K 2 groups; there are K 3 groups of laser signal feedback devices that cannot be associated in the state space; among them, K 3 = K - K 2 ; then the equation of the observation model can be written as:

[0047]

[0048] Among them, represents the coordinates of the laser signal feedback device in the state space matched through data association;

[0049] Among them, set the i-th group of laser signal feedback devices for observation to match the j-th group of laser signal feedback devices in the state space, and the corresponding sub-Jacobi matrix of this laser signal feedback device is:

[0050]

[0051] The total Jacobi matrix of the observation with respect to the state space obtained through transformation is:

[0052]

[0053] Then update the laser signal feedback device that has been matched.

[0054] Furthermore, in step S33, the specific steps for calculating the gain and updating the covariance and the state space are:

[0055] Calculate the gain K t through the covariance matrix Q of the observation, where

[0056]

[0057] Update the covariance ∑ t , where:

[0058] ∑ t = (I - K t H t ) ∑ t

[0059] Update the state space X t , where

[0060]

[0061]

[0062] In this way, the KEF algorithm of Kalman filter is used to match the coordinates of the previously observed laser signal feedback device and the coordinates of the currently observed laser signal feedback device, completing the positioning during mapping.

[0063] Furthermore, the specific steps for establishing a two-dimensional map of the farmland are as follows:

[0064] Use the pose and covariance of the current chassis mapping obtained in step S3, and call an external mapping function to generate a local map; then, through the loop of the local map, a complete grid map is formed.

[0065] The lidar scans the boundary of the farmland and calls an external mapping function, such as a laser SLAM function, to finally generate a complete two-dimensional map of the farmland. The generated complete two-dimensional map can be used for subsequent path planning and farmland operation planning.

[0066] Furthermore, the external mapping function can be a SLAM mapping algorithm, such as the mapping matching functions and classes of the cartograph algorithm and the GMapping algorithm, to generate a local map, and then through the loop of the local map, a complete grid map is formed.

[0067] Furthermore, when the system shows that a complete map has been established, the mapping work of the farmland is completed; when the system shows that a complete map has not been established, the system repeats step S33 to perform farmland mapping again.

[0068] Furthermore, the control component includes a motor, an industrial computer, a central processor, and a communication circuit that are arranged inside the chassis and are electrically connected to each other; the communication circuit communicates with the laser adjustment device, and the industrial computer is electrically connected to the laser emission and reception device for receiving the information transmitted by the laser emission and reception device; the central processor interacts with the laser emission and reception device for processing the point cloud information received by the laser emission and reception device and generating mapping data.

[0069] Furthermore, the laser adjustment device includes an electric push rod and a connecting piece. The connecting piece is used to install the laser emission and reception device, and the electric push rod is connected to the control component for pushing the connecting piece to move up and down, thereby pushing the laser emission and reception device to perform vertical displacement.

[0070] Furthermore, the laser emission and reception device includes a two-dimensional lidar and a laser data transmission line. The two-dimensional lidar continuously emits laser light through rotation and obtains the laser feedback information of the laser signal feedback device. The laser data transmission line is used to transmit the laser feedback information to the control component for processing.

[0071] In this technical solution, the two-dimensional lidar can rotate 360° to continuously obtain the surrounding laser emission information; the laser data transmission line is interconnected with the industrial computer on the chassis and is used to transmit the laser reflection information to the industrial computer for processing.

[0072] Further, the laser signal feedback device is a reflective column fixed on the farmland boundary and is used to reflect the laser beam to the laser emission and reception device.

[0073] Further, the reflective column is provided with reflective stickers, and there are at least 3 groups of the reflective columns.

[0074] By setting at least 3 groups of reflective columns and setting reflective stickers on the reflective columns, the laser beam of the laser emission and reception device can be better reflected, so as to facilitate the laser emission and reception device to detect the displacement distance of the laser beam in the vertical direction, so that the laser adjustment device can push the laser emission and reception device to move up and down, so that the emission center line of the laser emission and reception device is always flush with the center line of the laser signal feedback device.

[0075] In the farmland, it is easy to have the situation of lost positioning signals and inaccurate positioning data. And using the lidar to generate a two-dimensional map has relatively high requirements for positioning accuracy. Therefore, the method of positioning with the laser emission and reception device and the reflective column can be used to generate the two-dimensional map of the farmland, which is convenient for subsequent path planning work on the generated two-dimensional farmland map.

[0076] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0077] The farmland mapping method provided by the present invention locates the laser emission and reception device by setting the laser signal feedback device, and then locates the chassis, so as to effectively establish the farmland map, and has the beneficial effects of high positioning accuracy and low maintenance cost.

[0078] The farmland mapping and positioning method of the present invention also sets a laser adjustment device to adjust the height of the laser emission and reception device, so that the laser signal feedback device and the laser emission and reception device are always in the best reception position, so as to more accurately and effectively perform mapping and positioning in the farmland, facilitate the rapid and accurate generation of the two-dimensional map of the farmland in the farmland of hilly and mountainous areas, and be used for subsequent path planning. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] Figure 1 is a schematic structural diagram of the positioning system of the present invention Figure 1 。

[0080] Figure 2 is a schematic structural diagram of the positioning system of the present invention Figure 2 。

[0081] Figure 3 This is the working flow chart of the positioning system of the present invention. Specific embodiments

[0082] The attached drawings of the present invention are only for illustrative purposes and should not be construed as limitations on the present invention. To better illustrate the following embodiments, some components in the attached drawings will be omitted, enlarged or reduced, which do not represent the dimensions of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the attached drawings may be omitted.

[0083] Embodiment 1

[0084] As Figure 1 and Figure 2 shown, this embodiment discloses a positioning system for farmland mapping, including a chassis 100, a control component (not shown in the figure), a laser adjustment device 300, a laser emission and reception device 200, and a laser signal feedback device 400.

[0085] Among them, the chassis 100 is located at the bottom of the entire positioning system, providing support and power for the entire positioning system and moving through the wheels on the chassis 100.

[0086] The control component is arranged inside the chassis 100 and includes a motor, an industrial computer, a central processor, and a communication circuit that are electrically connected to each other; among them, the communication circuit is used for signal communication with the laser adjustment device 300; the industrial computer is electrically connected to the laser emission and reception device 200 and is used for receiving the information transmitted by the laser emission and reception device 200; the central processor interacts with the laser emission and reception device 200 and is used for processing the point cloud information received by the laser emission and reception device 200 and generating mapping data.

[0087] The laser adjustment device 300 is arranged directly above the chassis 100 and is electrically connected to the control component, including an electric push rod and a connecting piece. The connecting piece is used for installing and fixing the laser emission and reception device 200; the electric push rod is connected to the control component, used for information interaction with the control component, and pushing the connecting piece to move up and down, thereby pushing the laser emission and reception device 200 to move up and down.

[0088] The laser emission and reception device 200 is arranged directly above the laser adjustment device 300, used for emitting or receiving laser, and is electrically connected to the laser adjustment device 300 to adjust the up and down displacement through the laser adjustment device 300.

[0089] The laser signal feedback device 400 includes at least 3 groups and is arranged at the boundary of the farmland to be mapped, used for feeding back the laser to the laser emission and reception device 200 to prompt the height of the laser emitted by the laser emission and reception device 200.

[0090] Specifically, in this embodiment, the laser signal feedback device 400 is a reflective device, which consists of three groups of reflective columns and reflective stickers of a fixed size. Among them, the reflective stickers are attached to the reflective columns and are used to reflect the laser beam of the laser transmitting and receiving device 200, so that the laser transmitting and receiving device 200 can identify and detect the displacement distance of the laser, and further facilitate the adaptive adjustment of the height of the laser transmitting and receiving device 200 by the laser adjustment device 300, so that the laser emission center line of the laser transmitting and receiving device 200 is always flush with the center line of the laser signal feedback device 400.

[0091] Specifically, in this technical solution, the specific steps for the laser adjustment device 300 to adaptively adjust the height of the laser transmitting and receiving device 200 are as follows:

[0092] S1: Start working. The operator sends a movement instruction and a predetermined path to the control component. The control component drives the chassis 100 to move in the farmland, and starts the laser transmitting and receiving device 200 and the laser adjustment device 300.

[0093] S21: The laser transmitting and receiving device 200 continuously emits laser to the laser signal feedback device 400. The laser signal feedback device 400 reflects the laser back to the laser transmitting and receiving device 200. The laser transmitting and receiving device 200 judges the displacement ΔZmm of the chassis 100 in the vertical direction and the coordinate information of each laser signal feedback device 400 relative to the chassis 100 by detecting the positions of the emitted and received lasers, and transmits the displacement information and the coordinate information to the laser adjustment device 300.

[0094] S22: After receiving the displacement information transmitted by the laser transmitting and receiving device 200, the laser adjustment device 300 moves up or down by ΔZmm according to the displacement information. The laser transmitting and receiving device 200 moves along with the movement of the laser adjustment device 300, so that the laser emission center line of the laser transmitting and receiving device 200 is flush with the center line of the laser signal feedback device 400.

[0095] Further, in the positioning system of this technical solution, it also includes the positioning for farmland mapping and the method for establishing a farmland grid map. Specifically, the positioning method for farmland mapping mainly emits laser beams from the laser transmitting and receiving device 200 to the surrounding laser signal feedback devices 400 at a fixed frequency, and then the laser signal feedback devices 400 reflect the laser beams; the laser transmitting and receiving device 200 obtains the specific coordinates and orientations of the surrounding laser signal feedback devices 400 through the reflected laser beams. Through the specific coordinates and orientations of the laser signal feedback devices 400, the coordinates and orientations of the chassis 100 can be calculated, so as to position the farmland mapping.

[0096] Furthermore, by using the above-mentioned positioning method for farmland mapping, the coordinates and covariance matrix in the current state space of the chassis 100 can be calculated, facilitating the establishment of the farmland grid map.

[0097] As Figure 3 shown, specifically, when the positioning system of the present technical solution performs positioning for farmland mapping, it includes the following steps:

[0098] S31: Obtain the initial state space parameters of the chassis 100 and calculate the covariance prediction equation of the chassis 100 at time t; among them, the initial state space parameters of the chassis 100 include the motion equation of the chassis, the initial parameters of the covariance matrix, etc.;

[0099] S32: Compile the observation model and calculate the total Jacobian matrix of the observation with respect to the state space;

[0100] S33: Calculate the gain and update the covariance and state space.

[0101] Among them, in step S31, the specific steps of obtaining the initial state space parameters of the chassis 100 and calculating the covariance prediction equation of the chassis 100 at time t are as follows:

[0102] Establish a coordinate system with the chassis 100 as the center, and set the current pose of the chassis 100 as x, y, θ; where x is the coordinate of the chassis 100 on the x-axis, y is the coordinate of the chassis 100 on the y-axis, and θ is the rotation angle of the chassis 100;

[0103] Set that there are N retroreflective columns in the current state space, and set to be the x, y coordinates of the Nth retroreflective column; where N > 0, at this time, the set X of the state space coordinates of the N retroreflective columns relative to the current pose of the chassis 100 is:

[0104]

[0105] Set the initial pose of the chassis 100 as x 0 , y 0 , θ 0 ; then at the tth moment, the pose of the chassis 100 is x t , y t , θ t ; set the linear velocity σ v and the angular velocity σ ω of the disk wheel speedometer to both follow a Gaussian distribution with a mean of 0. According to the covariance calculation formula:

[0106]

[0107] At the initial moment, the covariance ∑ controlled by the wheel speedometer of the chassis 100 can be obtained ξ，0 as follows:

[0108]

[0109] where ∑ x , ∑ y , ∑ θ has an initial value of 1;

[0110] At the t-th moment, the covariance ∑ controlled by the wheel speedometer of the chassis 100 t is as follows:

[0111]

[0112] After calculation, the covariance prediction equation ∑ of the state quantity at the t-th moment t is as follows:

[0113]

[0114] where G ξ，t is the Jacobian matrix of the motion model with respect to the robot pose ξ t-1 ;

[0115]

[0116] G u is the Jacobian matrix of the motion model with respect to the control (wheel speedometer linear velocity and angular velocity);

[0117]

[0118] In step S32, the specific calculation steps for writing the observation model and calculating the total Jacobian matrix of the observation with respect to the state space are as follows:

[0119] It is assumed that there are K groups of laser signal feedback devices 400 detected on the farmland by the current laser emission and reception device 200, and the coordinate information of the K groups of laser signal feedback devices 400 is respectively

[0120] Through data association, the relevance is judged: among them, when the coordinates of the laser signal feedback device 400 in the state space can be displaced and rotated to obtain the coordinates of the laser signal feedback device 400 in the current laser emission and reception device 200, it means there is an association; otherwise, there is no association; it is assumed that the number of laser signal feedback devices 400 found to be associated in the state space is K 2 groups; the number of laser signal feedback devices 400 that cannot be associated in the state space is K 3 groups; where K 3 =K - K 2 ; then the equation of the observation model can be written as:

[0121]

[0122] Among them, represents the coordinates of the laser signal feedback device 400 in the state space matched through data association;

[0123] Among them, it is set that the i-th group of laser signal feedback devices 400 to be observed matches the j-th group of laser signal feedback devices 400 in the state space, and the sub-Jacobi matrix corresponding to this laser signal feedback device 400 is:

[0124]

[0125] Through conversion, the total Jacobi matrix of the observation with respect to the state space is:

[0126]

[0127] In step S33, the specific steps for calculating the gain and updating the covariance and the state space are as follows:

[0128] Calculate the gain K through the covariance matrix Q of the observation t , where

[0129]

[0130] Update the covariance ∑ t , where:

[0131] ∑ t =(I - K t H t )∑ t

[0132] Update the state space X t , where

[0133]

[0134]

[0135] In this way, by using the Kalman filter KEF algorithm to match the coordinates of the previously observed retroreflective columns and the coordinates of the currently observed retroreflective columns, the positioning during mapping is completed.

[0136] Specifically, in this embodiment, the establishment of the farmland grid map can be achieved through the following method: by using the above-mentioned farmland mapping and positioning method, obtain the current coordinates and covariance of the chassis 100, and then use the mapping matching functions and classes of SLAM mapping algorithms such as the cartograph algorithm and the GMapping algorithm, and finally form a complete grid map through local map loop closure.

[0137] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the technical solutions of the present invention, rather than limitations on the specific implementation manners of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the claims of the present invention shall be included within the protection scope of the claims of the present invention.

Claims

1. A positioning system for farmland mapping, characterized in that: It includes chassis, control components, laser adjustment device, laser transmitting and receiving device and laser signal feedback device; The chassis is used to provide support and power for the entire positioning system; The control component is arranged in the chassis and is used for controlling the entire positioning system and exchanging information; The laser adjustment device is arranged above the chassis and is electrically connected to the control component for information exchange with the control component; The laser emitting and receiving device is arranged above the laser adjusting device, is used to emit or receive laser, and is electrically connected to the laser adjusting device so as to adjust the up and down displacement through the laser adjusting device; The laser signal feedback device includes a plurality of laser signal feedback devices, which are arranged at the boundary of the farmland to be mapped, and are used to feed back laser to the laser transmitting and receiving device to indicate the height of the laser emitted by the laser transmitting and receiving device; The positioning system comprises the following steps when performing positioning: S1: Start the work. The operator remotely controls the chassis and sends movement instructions to the control component. The control component drives the chassis to move in the farmland and starts the laser transmitting and receiving device and the laser adjustment device. S2: The laser adjustment device automatically adjusts the height of the laser emitting and receiving device so that the laser emitting center line of the laser emitting and receiving device is always flush with the center line of the laser signal feedback device; S3: Use the Kalman filter KEF algorithm to calculate the current mapping posture and covariance matrix Q of the chassis to build a two-dimensional map of the farmland; In step S3, the specific calculation steps for calculating the current mapping pose and covariance matrix Q of the chassis are: S31: Obtain the initial state space parameters of the chassis and calculate the covariance prediction equation of the chassis at time t, including: Establish a coordinate system with the chassis as the center, and set the current position of the chassis to x, y, θ; where x is the coordinate of the chassis on the x-axis, y is the coordinate of the chassis on the y-axis, and θ is the rotation angle of the chassis; Assume that there are N reflective columns in the current state space, and set , Refers to the x and y coordinates of the Nth reflective column; where N>0, at this time, the state space coordinate set X of the N reflective columns relative to the current position of the chassis is: ； Set the initial position of the chassis to ; Then at the tth moment, the position of the chassis is ; Set the linear speed of the wheel speedometer and angular velocity All obey the Gaussian distribution with a mean of 0. According to the calculation formula of covariance: ， At the initial moment, the covariance of the chassis wheel speedometer control can be obtained for: ； Among them, setting The initial value of is 1; At time t, the covariance of the chassis wheel speedometer control is for: ； After calculation, the covariance prediction equation of the state quantity at time t is obtained for: ； in, ; is the Jacobian matrix of the motion model regarding the linear velocity and angular velocity of the control wheel speed meter; ； S32: Write the observation model and calculate the total Jacobian matrix of the observation state space, including: It is assumed that there are K groups of laser signal feedback devices on the farmland detected by the current laser transmitting and receiving device, and the coordinate information of the K groups of laser signal feedback devices are respectively [ ]; By data association, the association is determined: when the coordinates of the laser signal feedback device in the current laser transmitting and receiving device can be obtained by displacement and rotation using the coordinates of the laser signal feedback device in the state space, it means that there is an association; otherwise, there is no association; set the corresponding associated laser signal feedback device in the state space as group; the laser signal feedback devices that cannot be associated in the state space are group; among them, ; Then the equation of the observation model can be written as: in, It means that the coordinates of the laser signal feedback device in the state space are matched through data association; Among them, it is assumed that the observed group i laser signal feedback device and the group j laser signal feedback device in the state space are matched, and the sub-Jacobi matrix corresponding to the laser signal feedback device is: The total Jacobian matrix of the observation state space obtained by transformation is: ； S33: Calculate gain and update covariance and state space.

2. A positioning system for farmland mapping according to claim 1, characterized in that: In step S2, the specific steps of the laser adjustment device automatically adjusting the height of the laser emitting and receiving devices are: S21: the laser emitting and receiving device continuously emits laser to the laser signal feedback device, and the laser signal feedback device feeds the laser back to the laser emitting and receiving device by reflection. The laser emitting and receiving device determines the vertical displacement ΔZmm of the chassis and the coordinate information of each laser signal feedback device relative to the chassis by detecting the positions of the emitted and received lasers, and transmits the displacement information and coordinate information to the laser adjustment device; S22: After the laser adjustment device receives the displacement information transmitted by the laser emitting and receiving device, it moves upward or downward by ΔZmm according to the displacement information. The laser emitting and receiving device moves with the movement of the laser adjustment device so that the laser emission center line of the laser emitting and receiving device is flush with the center line of the laser signal feedback device.

3. A positioning system for farmland mapping according to claim 1, characterized in that: In step S33, the specific steps of calculating the gain and updating the covariance and state space are: The gain K is calculated by the observed covariance matrix Q t ,in, ； Update covariance ,in: Update state space ,in, ； 。 4. A positioning system for farmland mapping according to claim 1, characterized in that: The specific steps to create a two-dimensional map of farmland are: Step S3 is used to obtain the pose and covariance of the current chassis mapping, and an external mapping function is called to generate a local map; then the local map is looped back to form a complete grid map.

5. The positioning system for farmland mapping according to claim 1, characterized in that: The control component includes a motor, an industrial computer, a central processing unit and a communication circuit which are arranged in the chassis and electrically connected to each other; the communication circuit performs signal communication with the laser adjustment device, and the industrial computer is electrically connected to the laser emitting and receiving device for receiving information transmitted by the laser emitting and receiving device; the central processing unit performs information exchange with the laser emitting and receiving device for processing the point cloud information received by the laser emitting and receiving device and generating mapping data.

6. A positioning system for farmland mapping according to claim 1, characterized in that: The laser adjustment device includes an electric push rod and a connecting piece, wherein the connecting piece is used to install the laser emitting and receiving device, and the electric push rod is connected to the control component to push the connecting piece to move up and down, thereby pushing the laser emitting and receiving device to move up and down.

7. A positioning system for farmland mapping according to claim 1, characterized in that: The laser emitting and receiving device includes a two-dimensional laser radar and a laser data transmission line. The two-dimensional laser radar continuously emits laser through rotation and obtains laser feedback information from a laser signal feedback device. The laser data transmission line is used to transmit the laser feedback information to a control component for processing.

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