Full-automatic unmanned mowing system with underwater terrain adaptive regulation of cutter depth

Abstract

The application discloses a kind of full-automatic unmanned mowing system of self-adaptive adjustment cutter depth according to underwater topography, including mowing boat, satellite positioning navigation system and cloud map, and the ship of mowing boat is equipped with cutter, conveying belt, self-adaptive adjusting mechanism, communication module, sensor and shipborne control system;Shipborne control system calculates the current coordinate of cutter according to ship size data, depth information, ship attitude elevation and the height of ship bow and stern from water surface, determines actual cutter depth according to the current coordinate of cutter, compares actual cutter depth with expected cutter depth;Cutter is adjusted to expected depth by self-adaptive adjusting mechanism.The application is based on satellite positioning navigation and underwater topography data, season, depth, the attitude of empty load of ship, other needs of user and the like parameters, self-adaptive adjustment cutter depth, complete fixed-length harvesting of aquatic grass, realize the customization harvesting for different aquatic grass, different seasons, different regions.

Description

Technical Field

[0001] This application relates to water management equipment, and more particularly to a fully automated unmanned grass mowing system that adaptively adjusts the cutting depth according to underwater topography. Background Technology

[0002] Grass cutting is the process of cutting aquatic plants that have grown to the water surface. A grass cutting boat is a modern aquatic plant and water hyacinth harvesting equipment that integrates one or more functions such as grass cutting, gathering, dredging, water filtration, transportation, and unloading.

[0003] Aquatic plants have significant value in aquaculture, ecology, and landscaping. However, excessive planting without proper management can lead to rampant growth and decay, ultimately worsening water quality. To restore healthy water circulation and protect human health, measures must be taken to manage aquatic plants. Generally, there are three methods: ecological, chemical, and physical management. Ecological management is effective but difficult, time-consuming, and slow to show results; chemical management is fast-acting but can harm other organisms and worsen water quality; physical management includes both manual and mechanical mowing, which has the least environmental impact.

[0004] The lawn mowing equipment and methods currently proposed mainly fall into the following categories:

[0005] 1. Manual harvesting. This usually involves 2-3 people working together: one person rows a boat close to the aquatic plants while the others harvest them with sickles. This method is relatively outdated, inefficient, and poses a risk to personal safety.

[0006] 2. Mechanical harvesting followed by manual stacking and unloading. This type of mowing equipment generally consists of a cutter and conveyor belt, a flat float, and a propeller. After the cutter cuts the grass, the conveyor belt scoops it up, and workers stand behind the conveyor belt to separate and stack the grass using rakes. Unloading is done manually using rakes. Due to its simple structure and low cost, this is the most commonly used mowing method.

[0007] 3. Mechanical harvesting and unloading of hay, with human operation and assistance. In addition to the components mentioned above, this type of hay cutting equipment also includes a cab, a hopper conveyor belt, and an unloading conveyor belt. It is propelled by a propeller or paddle wheels, and the operator sits in the cab and operates it via hydraulic levers or buttons.

[0008] 4. Remote unmanned automated operation. This type of lawn mowing equipment achieves unmanned and remote control, and can autonomously plan its route for operation. It is a relatively advanced method at present, but it has not yet been widely promoted and popularized.

[0009] In their research paper, "A Study on the Design of Submerged Plant Harvesting Machinery," Shang Shiyou et al. from Inner Mongolia University of Technology pointed out that in order to solve the pollution problem of aquatic plants while taking into account the actual situation of landscape, environmental protection, and work efficiency, aquatic plant management must rely on mechanical mowing.

[0010] In the field of grass cutting boats and aquatic plant harvesting machinery, there is a key technical aspect—the adjustment of the cutting depth.

[0011] Traditionally, there are two methods for adjusting the cutting depth: manual adjustment and mechanically assisted adjustment.

[0012] During manual adjustment, once the conveyor belt angle is adjusted, the cutting depth remains fixed. Furthermore, the conveyor belt angle is adjusted in fixed increments and cannot be infinitely adjusted.

[0013] The general steps for mechanically assisted adjustment are as follows:

[0014] The cutter is mounted at the bottom of an inclined conveyor belt, one side of which is hinged to the hull, and the other side is fixed by an electric or hydraulic cylinder. The electric or hydraulic cylinder has a self-locking function, such as... Figure 1 As shown;

[0015] Before harvesting, for hydraulic cylinders, the state of the valve in the hydraulic station is controlled by the hydraulic rod or button to control the extension and retraction of the hydraulic cylinder piston rod; for electric cylinders, the forward and reverse rotation of the motor is controlled to control the extension and retraction of the electric cylinder piston rod, thereby changing the inclination angle of the conveyor belt.

[0016] Measure the depth of the cutter in the water and continuously adjust the cylinder stroke to ensure the cutter reaches the required depth. Then begin the harvesting operation.

[0017] During this operation, once the conveyor belt angle is adjusted, the cutting depth remains fixed, and the cutting depth can be infinitely adjusted.

[0018] In actual harvesting operations, there are seven influencing factors: different water depths; different types of aquatic plants; different seasons; harvesting aquatic plants in shallow waters; changes in the empty and full load weight and center of gravity of the mowing boat; changes in water depth; and safety issues.

[0019] According to research by Guo Kaidi of Beijing Forestry University and Zhao Defeng of Beijing University of Technology, water depth changes have a significant impact on the fresh weight and total biomass of *Hydrilla verticillata*. In their experimental environment, the water purification capacity of submerged plants is optimal at a depth of 85–90 cm, and a coupling relationship is formed between water depth and cutting depth.

[0020] Therefore, the traditional method of harvesting aquatic plants at a fixed distance from the water surface is likely to degrade water quality. This is because it cannot guarantee adequate light intensity for the plant roots, causing the plants to die and rot. In addition, harvesting aquatic plants damages plant cells, which increases the algae content in the water and thus worsens water quality.

[0021] Secondly, a paper published by Ni Meng et al. in the November 2022 issue of *Scientia Fisheries Science* pointed out that different aquatic plants have varying purification effects on total nitrogen, total phosphorus, ammonia nitrogen, nitrate nitrogen, and chemical oxygen demand. Plants at different water depths are influenced by water depth gradients and often grow in zones, possessing different optimal growth heights and competitive advantages at different water depths. Aquatic plant growth is also seasonal; different aquatic plants have their own peak growing seasons, and the overall water body treatment effect of aquatic plants in different seasons should correspond to different cutting cycles and depths.

[0022] Traditional harvesting operations often use a "one-size-fits-all" approach, where the harvesting depth is fixed before the operation begins. This approach fails to adjust the harvesting depth according to the area where aquatic plants grow or takes into account the impact of seasonal changes, thus failing to achieve optimal harvesting results.

[0023] In addition, water depth is not constant. Generally, river levels fluctuate greatly during the rainy and dry seasons, with flood seasons and dry seasons. Traditional harvesting methods cannot overcome the harvesting difficulties caused by this influence. Summary of the Invention

[0024] Purpose of the invention: In view of the problems existing in the prior art, this application proposes a fully automatic unmanned grass mowing system that can adaptively adjust the cutting depth according to the underwater terrain.

[0025] Technical solution: The fully automatic unmanned mowing boat that adaptively adjusts the cutting depth according to underwater terrain as described in this application includes:

[0026] The grass-cutting boat is equipped with a cutter, a conveyor belt, an adaptive adjustment mechanism, a communication module, sensors, and an onboard control system. The cutter is located at the front end of the conveyor belt, which is inclined and hinged to the hull on one side. The adaptive adjustment mechanism is a servo cylinder connected to the conveyor belt. The onboard control system controls the conveyor belt's tilt angle by controlling the length of the servo cylinder's extension rod, thereby controlling the cutting depth. The sensors are electrically connected to the onboard control system and are used to obtain the boat's attitude elevation and the height of the bow and / or stern above the water surface.

[0027] Satellite positioning and navigation systems are used to obtain the current position coordinates of the ship and its time information;

[0028] A cloud-based map is connected to the grass-cutting boat. The cloud-based map stores the size of the grass-cutting boat, queries underwater terrain data through the current hull position coordinates, and sends the underwater terrain data to the onboard control system of the grass-cutting boat. The underwater terrain data includes water depth information.

[0029] The shipboard control system calculates the current coordinates of the cutter based on the size data of the mower, water depth information, ship attitude elevation, and the height of the bow and stern above the water surface. It then determines the actual cutting depth based on the current coordinates of the cutter, compares the actual cutting depth with the desired cutting depth, and adjusts the cutter to the desired depth using a servo electric cylinder.

[0030] Establish an xOy coordinate system with the bow as the origin, the length of the ship as the x-axis, and the height of the ship as the y-axis.

[0031] Define the coordinates of the cutter endpoint as A(x) A y A The connection point between the servo electric cylinder and the conveyor belt is B(x). B y B The hinge point between the conveyor belt and the hull is C(x). C y C The connection point between the servo electric cylinder and the hull is D(x). D y D ), point E(x) E y E ) is point A(x) A y A The projection point F(x) onto the current water level line along the y-axis in the xOy coordinate system. F y F () is the projection point of the stern end onto the current waterline along the y-axis.

[0032] The height h of the cutter tip from the riverbed is derived from the following system of equations:

[0033]

[0034] x A =x E

[0035]

[0036] h=H+ΔH g -|y A -y E |cosβ

[0037] Where H is the water level height measured at the historical water level, ΔH g It represents the change in elevation; α is ∠ABC; β is the bow angle of the ship; h1 is the height of the bow above the water surface; xC y C x D y D L1 and L2 are known quantities; l is determined by the servo electric cylinder; the unknown quantity is x. A y A x B y B The solution is obtained by solving the system of equations.

[0038] In one alternative embodiment, the sensor includes an ultrasonic sensor or a level sensor, mounted on the bow and / or stern, for measuring the height of the bow and / or stern above the water surface. Furthermore, the ultrasonic sensor and / or level sensor calculates the error caused by changes in water level in real time.

[0039] In one alternative embodiment, the sensor includes an attitude sensor for measuring the bow and / or stern tilt angles of the vessel. Further, the attitude sensor calculates in real-time the bow and / or stern tilt errors caused by continuous grass gathering.

[0040] In one alternative implementation, the water depth information is calculated from historical water depth and elevation changes.

[0041] In one alternative implementation, the harvesting range and / or depth requirements are planned on the cloud map, and these requirements are transmitted to the ship's onboard control system via a communication module. Preferably, the communication module uses 5G communication.

[0042] The beneficial effects of this application are as follows:

[0043] 1. Adaptive adjustment of cutting depth: The mowing boat can automatically adjust the depth of the cutting blade into the water based on the coordinates and water depth data of the current working area and the set distance from the riverbed; this ensures the optimal growth height of aquatic plants and improves the water purification efficiency of aquatic plants.

[0044] 2. Regionalized and customized adjustment of mowing depth: Because aquatic plants exhibit significantly different growth rates at varying water depths, and different aquatic plants are most competitive at different depths, and considering the combined planting of aquatic plants, the same type of aquatic plant often grows in patches or areas; the mowing boat uses cloud-based map data to divide the water area into zones, setting different mowing depths for different zones; during continuous operations traversing different zones, the mowing height is automatically adjusted; in actual operation, this avoids the predicament of users needing to adjust the cutting depth after mowing one area before moving to the next; thus maximizing the water purification efficiency of the aquatic plants and improving work efficiency; for example... Figure 2Traditional adjustment methods require stopping the boat at three points (A, B, and C) and adjusting the cutting depth before proceeding to the next area; for example... Figure 3 As shown, for the automatically adjustable mode, the cutting depth can be automatically adjusted when the route crosses areas, thereby achieving continuous operation.

[0045] 3. Prevent the cutter and the hull from hitting the bottom; the grass-cutting boat can automatically determine the current height of the cutter, hull, and propeller above the bottom and at the next destination based on the water depth data at the current coordinates. It can then automatically raise the cutter or automatically control the hull to turn to avoid obstacles, reducing the risk of hitting the bottom and running aground, thereby reducing damage to the hull and the shore.

[0046] 4. Higher cutting depth accuracy: For the changes in the cutting depth caused by the weight and center of gravity of the mower when it is empty, fully loaded, or unloading grass, the error in the cutting depth caused by the weight and center of gravity changes is eliminated by introducing real-time parameters from attitude sensors and liquid level sensors. The water level is calculated by elevation changes to ensure that the cutting depth is always accurate.

[0047] 5. Automated adjustment; using unmanned automated control, parameters are set in advance, and the operation is carried out automatically; ensuring that there are no safety hazards caused by human error or the risk of water operations caused by adjusting the cutting depth. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of a traditional mechanically assisted adjustable mowing boat.

[0049] Figure 2 A schematic diagram of the regional operation of a traditional grass-cutting boat with a fixed cutter depth;

[0050] Figure 3 This is a schematic diagram of a regional operation with automatically adjustable cutting depth according to an embodiment of this application;

[0051] Figure 4 This is a schematic diagram illustrating the principle of calculating the height of the cutter from the riverbed according to an embodiment of this application;

[0052] Explanation of reference numerals in the attached drawings: 1: cutter; 2: conveyor belt; 3: conveyor belt hinge point; 4: slot plate; 5: slot hinge point; 6: hull. Detailed Implementation

[0053] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is not intended to limit this application or its application or use in any way. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0054] A fully automated unmanned lawn mowing system that adaptively adjusts the cutting depth according to underwater terrain includes a mowing boat, a satellite positioning and navigation system, and a cloud map.

[0055] The grass-cutting boat is equipped with a cutter 1, a conveyor belt 2, an adaptive adjustment mechanism, a communication module, sensors, and an onboard control system on its hull 6. Specifically, the cutter 1 is located at the front end of the conveyor belt 2, which is arranged at an angle and hinged to the hull 6 on one side. To ensure effective communication, the communication module preferably uses 5G wireless communication.

[0056] The adaptive adjustment mechanism is electrically connected to the shipboard control system and is used to adjust the cutting depth. Specifically, the adaptive adjustment mechanism is connected to conveyor belt 2 and adjusts its tilt under the control of the shipboard control system, thereby adjusting the cutting depth at the end. The cutting depth here typically refers to the height of the cutter from the riverbed.

[0057] The sensors are electrically connected to the shipboard control system to obtain the vessel's attitude elevation and the height of the bow and stern above the water surface. Specifically, the sensors include attitude sensors for measuring the bow and / or stern heel angles, and ultrasonic or level sensors for measuring the height of the bow and stern above the water surface. These ultrasonic or level sensors are mounted on the bow and / or stern. Preferably, the sensors calculate in real time the bow and stern heel errors caused by continuous reed harvesting, as well as errors caused by water level changes.

[0058] The cloud-based map and the mower boat are connected, and the cloud-based map stores the dimensions of the mower boat. The system obtains the current position coordinates and time information of the boat through a satellite positioning and navigation system. The mower boat transmits its current position coordinates to the cloud-based map, which then queries the underwater terrain data based on the boat's position coordinates and sends the underwater terrain data to the mower boat's onboard control system. The underwater terrain data includes, but is not limited to, the water depth information at the current position coordinates. The water depth information can be calculated from historical water depth, historical elevation, and the current elevation. Preferably, the cloud-based map supports planning the harvesting range and / or depth requirements.

[0059] like Figure 4As shown, one end of the conveyor belt 2 extends into the water, and the other end is supported by a column, arranged at an angle on the hull 6. The conveyor belt 2 and the column are hinged. The adaptive adjustment mechanism uses a servo electric cylinder, which is fixed to the hull 6, and its drive rod is connected to the conveyor belt 2. When the drive rod extends, the conveyor belt 2 rotates clockwise around the support point, and the side with the cutter installed is raised; when the drive rod retracts, the conveyor belt 2 rotates counterclockwise around the support point, and the side with the cutter installed is lowered. The shipborne control system receives water depth information, ship attitude elevation, and bow and stern height above the water surface from the cloud map, calculates the current coordinates of the cutter (representing the actual cutter depth), compares the actual cutter depth with the desired cutter depth, and calculates the height difference between the actual cutter depth and the desired cutter depth. This height difference can be converted into the stroke of the servo electric cylinder, thereby realizing the adaptive adjustment of the cutter by the shipborne control system. For the bow and stern tilt of a ship, the attitude sensor can directly obtain the bow tilt angle β. At the same time, by mounting an ultrasonic sensor or a liquid level sensor on the bow and / or stern respectively, the height of the bow and / or the height of the stern above the water surface can be obtained. The liquid level sensor is vertically mounted on the hull, and the sensor will also tilt at an angle after the bow tilt of the hull.

[0060] according to Figure 1 Given that the bow angle of the ship is β and the depth of the cutter tip A in the water is AA', the formula for calculating the height h of the cutter tip A from the riverbed is:

[0061] h=H+ΔH g -AA'

[0062] Where H is the water level measured at the historical water level, i.e., the height of the water surface from the riverbed; ΔH g It is the change in elevation, used to eliminate changes in water level. For example, if the measured value is the Yellow Sea elevation, with the 1956 Yellow Sea elevation system as the reference system, if the water level changes, the measured elevation will also change.

[0063] When calculating the water depth AA' at point A, the length of AE should be calculated first. According to the principle of similar triangles and the law of cosines, ∠EAA'=β. Then AA' = AE·cosβ = |y A -y E |cosβ, which gives the depth of point A in the water, and then combined with the current water depth H+ΔH g The height h of the cutter from the riverbed can be calculated:

[0064] h=H+ΔH g -|y A -y E |cosβ Equation (1)

[0065] According to equation (1), |y| should be determined.A -y E |,|y A -y E The specific calculation process for the value of | is as follows:

[0066] With the bow as the origin O(0,0) and the length of the hull as L, establish the xOy coordinate system with the direction of the hull length as the x-axis and the direction of the hull height as the y-axis.

[0067] Define the coordinates of the cutter endpoint as A(x) A ,y A The connection point between the servo electric cylinder and the conveyor belt is B(x). B ,y B The hinge point between the conveyor belt and the hull is C(x). C ,y C The connection point between the servo electric cylinder and the hull is D(x). D ,y D ), where x C y C x D y D Determined by the mechanical structure, it is a known quantity;

[0068] Define ∠ABC = α, point E(x) E ,y E ) is point A(x) A ,y A The projection point I(x) onto the current water level line (blue line) along the y-axis in the xOy coordinate system; I (0) is the intersection of AE and the x-axis, x A =x E =x I Point F(x) F ,y F () is the projection point of the stern end onto the current waterline along the y-axis; the following relationship holds:

[0069]

[0070]

[0071] Once the mechanical mechanism is determined, α is determined, L1, L2, and l are all known quantities, and l is the length of BD, which can be obtained in real time based on the size of the servo electric cylinder and the stroke of its drive rod; the unknown quantity x is solved by the above set of equations (equation (2)-equation (5)). A y A x B y B .

[0072] Furthermore, we define the intersection of the bow extension along the x-axis and the current water level line as G. According to the principle of similar triangles, ∠OGF is the bow inclination angle β of the ship. We define the intersection of the origin O and the current water level line as O'.

[0073] In triangle OGO', OO' = h1, which is the height of the bow above the water surface.

[0074] In triangle EGI, according to the principle of similar triangles, ∠EGI = β. |EI|=|y E -y I |=|y E |, but

[0075] Therefore, it is determined Then, the height of the cutter from the riverbed is determined according to equation (1).

[0076] The following describes the lawn mowing process of this application in detail with reference to a preferred embodiment:

[0077] S1. Establish a cloud-based map and construct local geographic information data; the cloud-based map includes coordinates and parameters such as water depth at those coordinates. Map information can also be constructed by purchasing third-party data; specifically, for underwater topographic mapping data that users require to be kept confidential, it can be stored on the customer's dedicated business cloud platform service instead of a public cloud.

[0078] S2, input the size data of the mowing boat itself into the shipboard control system;

[0079] S3, through the hull's 5G communication system, uploads the size data of the mowing boat to the cloud;

[0080] S4, the mowing boat is started;

[0081] S5, Select harvesting mode; harvesting modes include but are not limited to harvesting at a fixed distance from the water surface, harvesting at a fixed distance from the bottom of the water, and harvesting according to the parameters set last time;

[0082] S6, plan the harvesting range and depth requirements on the electronic map;

[0083] S7, obtain the current hull position coordinates based on satellite positioning and navigation data;

[0084] S8 uploads the current hull position coordinates to a cloud map via the ship's 5G communication module;

[0085] S9, cloud map queries current underwater topography data based on coordinates, with a focus on the water depth at that location;

[0086] S10 transmits the planned harvesting range, depth requirements, and current underwater topographic data to the ship via a 5G communication module. The underwater topographic data includes the water depth at that location.

[0087] S11. Based on satellite positioning and navigation data, obtain the current ship time and calculate the season;

[0088] S12, the shipboard control system reads data from the attitude sensor and level sensor to obtain the ship's attitude and elevation, as well as the height of the bow and stern above the water surface;

[0089] S13, through the shipboard control system, calculates the current coordinates of the cutter based on the water depth information at that point sent down from the cloud map and the data such as the ship's attitude elevation and the height of the bow and stern from the water surface.

[0090] S14, The actual cutting depth is obtained by using the current coordinates of the cutting tool, and the actual cutting depth is compared with the expected cutting depth;

[0091] S15: By comparing the actual cutting depth with the desired cutting depth, the difference is converted into the stroke of the servo electric cylinder; the shipborne control system controls the servo electric cylinder to control the conveyor belt tilt angle, thereby controlling the cutting depth and realizing adaptive adjustment of the cutting blade.

[0092] S16 uses attitude sensors and liquid level sensors to calculate in real time the bow and stern tilt errors caused by continuous grass harvesting, as well as the errors caused by water level changes, thereby improving the accuracy of adaptive control.

[0093] This embodiment utilizes underwater topographic data, combining underwater topography with aquatic plant harvesting. Water depth information at the current hull position coordinates is obtained through underwater topographic mapping or infrastructure drawings. Simultaneously, a servo electric cylinder is used as an adaptive adjustment mechanism, controlling the conveyor belt tilt angle by controlling the length of the cylinder's drive rod. By incorporating the mower's attitude data, the onboard controller accurately calculates the cutter's entry depth in real time, and calls and compares data from the database to adjust the cutter's entry depth, thus achieving precise adaptive real-time adjustment of the mower's cutting depth.

[0094] Compared with existing technologies, this application achieves adaptive adjustment of the cutting depth based on parameters such as satellite positioning and navigation, underwater topography data, season, water depth, the empty and fully loaded attitude of the vessel, and other user requirements, to complete the harvesting of aquatic plants at a fixed length. It can perform customized harvesting for different aquatic plants, different seasons, and different regions, and realize multiple harvesting modes such as harvesting at a fixed distance from the water surface, harvesting at a fixed distance from the bottom, and harvesting according to the previously set parameters. At the same time, it can prevent the cutting blade from hitting the bottom and the vessel from hitting the bottom. The entire process is automatically adjusted without human intervention, making it more reliable and overcoming the shortcomings of traditional cutting depth adjustment such as inflexibility and low precision.

[0095] It should be noted that, through the above embodiments, it can be seen that regardless of whether the adaptive adjustment directly or indirectly controls the cutter, as long as the electromechanical transmission parameters of the adaptive adjustment mechanism are determined, a mathematical relationship can be established between the cutter depth and the electromechanical transmission parameters of the adaptive adjustment mechanism. This transforms the adjustment of the cutter's depth in water into the adjustment of the adaptive adjustment mechanism's stroke. Therefore, theoretically, the adaptive adjustment mechanism can be directly connected to the cutter, and under the control of the shipboard control system, the adaptive adjustment mechanism can directly control the cutter's depth in water. That is, the installation of the adaptive adjustment mechanism can be adaptively adjusted according to the structure of the mower boat. The specific implementation method is something that those skilled in the art can achieve based on the content disclosed in this application, and will not be elaborated here.

[0096] The embodiments described above are merely illustrative of several implementation methods of this application and should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the scope of protection of this application.

Claims

1. A fully automated unmanned lawn mowing system that adaptively adjusts the cutting depth according to underwater terrain, characterized in that, include: The grass-cutting boat is equipped with a cutter, a conveyor belt, an adaptive adjustment mechanism, a communication module, sensors, and an onboard control system. The cutter is located at the front end of the conveyor belt, which is inclined and hinged to the hull on one side. The adaptive adjustment mechanism is a servo cylinder connected to the conveyor belt. The onboard control system controls the conveyor belt's tilt angle by controlling the length of the servo cylinder's extension rod, thereby controlling the cutting depth. The sensors are electrically connected to the onboard control system and are used to obtain the boat's attitude elevation and the height of the bow and / or stern above the water surface. Satellite positioning and navigation systems are used to obtain the current position coordinates of the ship and its time information; A cloud-based map is connected to the grass-cutting boat. The cloud-based map stores the size of the grass-cutting boat, queries underwater terrain data through the current hull position coordinates, and sends the underwater terrain data to the onboard control system of the grass-cutting boat. The underwater terrain data includes water depth information. The shipboard control system calculates the current coordinates of the cutter based on the size data of the mower, water depth information, ship attitude elevation, and the height of the bow and stern above the water surface. It then determines the actual cutting depth based on the current coordinates of the cutter, compares the actual cutting depth with the desired cutting depth, and adjusts the cutter to the desired depth using a servo electric cylinder. Establish an xOy coordinate system with the bow as the origin, the length of the ship as the x-axis, and the height of the ship as the y-axis. Define the coordinates of the cutter endpoint as A(x) A y A The connection point between the servo electric cylinder and the conveyor belt is B(x). B y B The hinge point between the conveyor belt and the hull is C(x). C y C The connection point between the servo electric cylinder and the hull is D(x). D y D ), point E(x) E y E ) is point A(x) A y A The projection point F(x) onto the current water level line along the y-axis in the xOy coordinate system. F y F () is the projection point of the stern end onto the current waterline along the y-axis. The height h of the cutter tip from the riverbed is derived from the following system of equations: x A =x E h=H+ΔH g -|y A -y E |cosβ Where H is the water level height measured at the historical water level, ΔH g It represents the change in elevation; α is ∠ABC; β is the bow angle of the ship; h1 is the height of the bow above the water surface; x C y C x D y D L1 and L2 are known quantities; l is determined by the servo electric cylinder; the unknown quantity is x. A y A x B y B The solution is obtained by solving the system of equations.

2. The fully automated unmanned lawn mowing system according to claim 1, characterized in that, The sensors include ultrasonic sensors or liquid level sensors, installed at the bow and / or stern of the ship, for measuring the height of the bow and / or stern above the water surface.

3. The fully automated unmanned lawn mowing system according to claim 2, characterized in that, The sensor calculates the error caused by changes in water level in real time.

4. The fully automated unmanned lawn mowing system according to claim 1, characterized in that, The sensors include attitude sensors for measuring the bow and / or stern tilt angles of the ship.

5. The fully automated unmanned lawn mowing system according to claim 4, characterized in that, The sensor calculates in real time the bow and / or stern tilt errors caused by continuous grass harvesting.

6. The fully automated unmanned lawn mowing system according to claim 1, characterized in that, The water depth information is calculated from historical water depth and elevation changes.

7. The fully automated unmanned lawn mowing system according to claim 1, characterized in that, The harvesting range and / or depth requirements are planned on the cloud map, and the harvesting range and / or depth requirements are sent to the ship's onboard control system via a communication module.

8. The fully automated unmanned lawn mowing system according to claim 1 or 7, characterized in that, The communication module uses 5G communication.

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