Harvesting platform terrain following and terrain hovering control system and method based on four-wheel independent drive chassis

Abstract

A kind of based on four-wheel independent drive chassis's harvesting platform terrain simulation adjusting system and method belong to intelligent agricultural machinery technical field.Aiming at the problem that existing platform is difficult to adapt to complex terrain, the mapping relationship of vehicle pose, terrain elevation function and platform space posture is constructed in unified ground coordinate system, data is acquired in real time by terrain information acquisition module and vehicle posture measurement unit, three degrees of freedom adjustment of platform lifting, pitching and roll are realized by double independent electric push rod through coordinate transformation and geometric inverse solution.The system includes mobile platform, hanging module, harvesting and conveying module, collecting device and controller.The invention realizes high-precision profiling control under complex terrain such as hills and slopes, maintains constant ground clearance and set posture angle, significantly improves harvesting quality and operation safety.

Description

Technical Field

[0001] This invention belongs to the field of intelligent agricultural machinery technology, and relates to a harvesting platform terrain-following adjustment system and method, specifically a harvesting platform terrain-following adjustment system and method based on the relationship between terrain elevation function and spatial geometric mapping. Background Technology

[0002] With the continuous improvement of the operational efficiency of agricultural machinery such as combine harvesters and reapers, the working width of the front-mounted harvesting platform is gradually increasing. Its ground clearance and spatial posture have a direct impact on the quality of operation and equipment safety. If the harvesting platform is too low off the ground, it is prone to collision with hard objects on the ground, causing damage to the blades or abnormal structural stress; if the ground clearance is too high, it will lead to unstable stubble height, missed cutting, or increased crop entrainment, affecting the harvest quality.

[0003] In hilly, ravine, and undulating farmland environments, the terrain exhibits not only longitudinal slope changes in the direction of vehicle travel but also transverse slope changes in the lateral direction. When vehicles travel on such complex terrain, their spatial posture continuously changes. If the harvesting platform cannot adjust its height and posture in sync with these terrain changes, it is easy for one side of the platform to "eat the ground" while the other side "hangs in the air," which not only affects the operational efficiency but may also lead to uneven stress on the platform or even structural damage.

[0004] In existing technologies, most harvesting platform height adjustment solutions rely primarily on ground proximity sensors, floating mechanisms, or manual experience for adjustment. These solutions typically only achieve overall platform lifting control, failing to coordinate adjustments to the platform's pitch and lateral tilt. Some methods based on single-axis tilt angle or unidirectional slope compensation fail to describe the relationship between vehicle position, terrain elevation, and platform spatial attitude within a unified coordinate system, making it difficult to handle conditions with combined longitudinal and transverse slope variations. Furthermore, some control strategies do not adequately consider constraints such as platform geometry, actuator travel range, and the continuity of attitude changes. When terrain slopes change abruptly or undulate significantly, this can easily lead to frequent actuator movements, impacts, and vibrations, affecting system stability and operational safety.

[0005] Therefore, it is necessary to propose an automatic adjustment system and method to achieve continuous contour control of the harvesting platform under complex terrain conditions. Summary of the Invention

[0006] This invention addresses the problems in existing technologies, such as the difficulty in simultaneously adapting to longitudinal and lateral terrain slope contours, insufficient platform attitude freedom, and the susceptibility of actuators to impacts at abrupt terrain changes. It proposes a terrain-following adjustment system and method for harvesting platforms based on a four-wheel independent drive chassis. By constructing a continuous mapping relationship between vehicle pose, terrain elevation function, and the spatial position and attitude of the harvesting platform within a unified ground coordinate system, and introducing geometric and physical constraints into this mapping relationship, the automatic contouring adjustment of the harvesting platform's height and attitude according to terrain changes is achieved.

[0007] The terrain-adaptive adjustment system for the harvesting platform based on a four-wheel independent drive chassis provided in this application adopts the following technical solution:

[0008] A terrain-adaptive adjustment system for a harvesting platform based on a four-wheel independent drive chassis, characterized in that the adjustment system includes:

[0009] The mobile platform is used to provide an installation reference and load-bearing support for other modules;

[0010] A mounting module is connected and installed to the mobile platform for adjusting the angle of the harvesting and conveying module.

[0011] A harvesting and conveying module is connected and installed to the mobile platform for harvesting and conveying.

[0012] A collection device, connected and installed with the mounting module, is used to transfer the harvested materials.

[0013] A terrain information acquisition module is connected and installed with the mobile platform to provide terrain elevation functions or their discrete elevation data.

[0014] A vehicle attitude and position measurement unit, built into the mobile platform, is used to obtain the position of the mobile platform in the ground coordinate system and the vehicle's forward angle;

[0015] The controller, built into the mobile platform, is connected to the harvesting and conveying module, the collection device, the terrain information acquisition module, and the vehicle attitude and position measurement unit.

[0016] By adopting the above technical solution, terrain elevation data and vehicle posture are acquired in real time through the terrain information acquisition module and the vehicle posture and position measurement unit. Based on this information, the controller drives the harvesting and conveying module and the collection device to achieve adaptive adjustment of the harvesting platform's posture relative to the ground. This solves the problem that traditional harvesting platforms are rigidly connected to the chassis, making it impossible to adjust their posture in real time according to changes in terrain undulations when operating in complex terrains such as hills and slopes. This results in inconsistent harvesting heights, high crop loss rates, and even rigid collisions between the chassis and the ground. The solution achieves decoupled control between the harvesting platform and the vehicle chassis, enabling the platform to actively conform to terrain changes and maintain a constant ground clearance, significantly improving harvesting quality and operational safety under complex terrain conditions.

[0017] Furthermore, the mounting module consists of a mounting bracket, a lateral support, a fisheye connector, a longitudinal support, and a hinge seat; the mounting bracket is connected and fixed to the front end of the mobile platform, the lateral support is connected and fixed to the mounting bracket, and the fisheye connector is adjustablely connected to the lateral support and then locked and fixed thereto, which is used to provide a universal swing connection so that it can follow the platform's posture changes.

[0018] By adopting the above technical solution and utilizing the omnidirectional swing characteristics of the fisheye joint, passive servoing is achieved during platform attitude adjustment, providing multi-degree-of-freedom attachment points for the harvesting and conveying module. This realizes omnidirectional servoing of the attachment points, eliminates mechanical interference during attitude adjustment, reduces the drive load on the actuator, and improves the system's mechanical life and adjustment flexibility.

[0019] Furthermore, the harvesting and conveying module consists of a harvesting platform, a conveying platform, a first electric push rod, a second electric push rod, and a hinged seat; the harvesting platform and the conveying platform are connected and fixed to form the follower platform body; the first electric push rod and the second electric push rod are arranged symmetrically on the left and right and are independent of each other; one end of each electric push rod is hinged to the moving platform and the other end is hinged to the follower platform body; the extension and retraction of the first electric push rod and the second electric push rod cooperate with the rotation of the hinged seat to enable the follower platform body to achieve overall lifting, pitching, and tilting attitude adjustment.

[0020] By adopting the above technical solution and using a parallel drive method with two electric actuators, the attitude adjustment of the servo platform body, which consists of the harvesting platform and the conveying platform, in three degrees of freedom (lifting, pitching, and tilting) is achieved through the independent extension and retraction length combination of the two electric actuators and the rotation of the hinge seat. Only two linear actuators are used to realize the three-degree-of-freedom attitude control of the platform. The mechanism is simple, the control decoupling is straightforward, the response speed is fast, and the independent left and right drives facilitate differential control to adapt to sloping terrain.

[0021] Furthermore, the collecting device consists of a collecting box, a connecting plate, a mounting plate, a hinge seat, and a third electric push rod; the connecting plate is fixedly connected to the collecting box and rotatably connected to the longitudinal support, so that the collecting box can flip relative to the hanging module; the mounting plate is fixedly connected to the collecting box, the hinge seat is mounted on the mounting plate, one end of the third electric push rod is rotatably connected to the first hinge seat, and the other end is rotatably connected to the hinge seat. When the third electric push rod extends or retracts, it drives the collecting box to flip to achieve unloading or transfer.

[0022] By adopting the above technical solution, the collection box is rotatably connected to the longitudinal support via a connecting plate, forming a degree of freedom for tilting; the two ends of the third electric actuator are respectively hinged to the hinge seat, and the collection box is tilted around the hanging module through telescopic drive, realizing the adjustment of the unloading or transfer posture. Active tilting control of the collection box is realized, which can complete fixed-point unloading or docking with transfer vehicles without moving the vehicle, improving the continuity of operation and transfer efficiency.

[0023] The terrain-adjusting method for a harvesting platform based on a four-wheel independent drive chassis provided in this application adopts the following technical solution:

[0024] A method for terrain-following adjustment of a harvesting platform based on a four-wheel independent drive chassis, characterized by the following steps:

[0025] S1: In the ground coordinate system, based on the vehicle position (x v y v ) and the vehicle's forward angle φ, calculate the planar position (x) of the harvesting platform center. c y c );

[0026] S2: Based on the above planar position (x) c y c Using the terrain elevation function h(x, y), the elevation is mapped to the center of the harvesting platform, and the ground height at the platform center is calculated.

[0027] ;

[0028] S3: Set the target ground clearance Δh of the harvesting platform relative to the ground, and superimpose the target ground clearance constraint on the ground height at the center of the platform to determine the target height at the center of the harvesting platform:

[0029]

[0030] Thus, the coordinates of the platform's center target are obtained.

[0031] ;

[0032] S4: Calculate the terrain slope s based on the gradient or difference approximation of the terrain elevation function. fand lateral slope s y This is used to subsequently determine the target tilt angle ϕ of the platform;

[0033] S5: The above transverse slope s y Converted to ground tilt angle ϕ ground And determine the target tilt angle ϕ of the harvesting platform according to the set lateral target angle Δϕ, so as to achieve cross slope contour control;

[0034] S6: Set the center target coordinates P of the above-mentioned harvesting platform c Combined with the attitude matrix R(φ, θ, ϕ) formed by the vehicle's forward angle φ, the harvesting platform's forward and backward tilt angles θ, and the target's side tilt angle ϕ, a spatial transformation relationship from the platform coordinate system to the ground coordinate system is established. The left and right endpoints of the platform are mapped to the ground coordinate system to obtain the target coordinates of the left and right endpoints:

[0035] ;

[0036] S7: Obtain the coordinates of the left and right actuator hinge points on the vehicle body side in the ground coordinate system. , Based on the spatial geometric relationship between the platform endpoints and the corresponding hinge points, the target extension length L of the left and right actuators is solved inversely. L L R ;

[0037] S8: The target length L mentioned above... L and L R As control commands are issued to the first electric actuator (303) and the second electric actuator (304) of the left and right actuators, the harvesting platform maintains the set ground clearance Δh and the target angle Δθ with the ground slope during the vehicle's movement, so that the harvesting platform can achieve terrain-based ground clearance and posture contour adjustment during the vehicle's movement.

[0038] By adopting the above technical solution, a complete closed-loop control chain was established, encompassing vehicle pose → terrain elevation mapping → target height constraint → slope calculation and attitude planning → spatial coordinate transformation → inverse kinematics calculation of the actuator → drive control. This transforms terrain geometric information into physical control quantities for the actuator. A complete mathematical mapping relationship between terrain, vehicle, platform, and actuator was constructed, enabling proactive predictive control based on prior terrain information, rather than traditional passive ground-contact sensing control. This significantly improves the real-time performance and predictability of terrain tracking.

[0039] Furthermore, the planar position (x) of the center of the harvesting platform described in step S1 c y c The specific calculation method is as follows:

[0040]

[0041] Where, d rf This refers to the nominal front overhang distance of the harvesting platform center relative to the vehicle reference point.

[0042] By adopting the above technical solution, based on the vehicle reference point coordinates (x... v y v ), vehicle forward angle φ and nominal front overhang distance d rf The platform's center plane position is calculated using rigid body planar kinematics equations. This eliminates lever arm errors between the vehicle reference point and the work point, improves the accuracy of terrain elevation mapping, and provides a foundation for precise contour control.

[0043] Furthermore, the terrain elevation function h(x, y) described in step S2 is obtained by any of the following methods or a combination thereof:

[0044] (1) A digital elevation model obtained by prior surveying of the work area;

[0045] (2) Terrain function constructed by online scanning of vehicle-mounted lidar, millimeter-wave radar or depth camera and interpolation algorithm;

[0046] (3) Terrain model obtained by fitting RTK-GNSS and ground calibration points;

[0047] (4) The terrain database pre-stored in the farmland operation management system.

[0048] By adopting the above technical solutions, multiple data sources are supported, including prior mapping DEMs, online scanning by vehicle-mounted radar, RTK-GNSS calibration and fitting, and farmland databases. A continuous terrain elevation function h(x,y) is constructed through interpolation or fitting algorithms. A multi-source heterogeneous terrain data fusion scheme is provided, which supports both global planning of high-precision prior maps and local obstacle avoidance for online perception, enhancing the system's environmental adaptability and operational planning flexibility.

[0049] Furthermore, the terrain slope s mentioned in step S4 f The specific calculation method is as follows:

[0050] Construct the unit vector for the vehicle's direction of travel:

[0051]

[0052] Based on the topographic elevation function at point (x) c y c gradient at ) Establish the projection relationship between terrain slope and vehicle travel direction, and calculate its slope along the travel direction:

[0053]

[0054] terrain slope s f An approximate calculation using a differential method is employed. This involves selecting a preset distance along the vehicle's direction of travel and establishing a correlation between slope and distance based on terrain elevation differences. Specifically, a distance 'd' is selected along the vehicle's direction of travel, and... ,but

[0055] ;

[0056] The specific method for determining the target tilt angle ϕ of the platform is as follows:

[0057] The above slope s f Converted to ground tilt angle

[0058]

[0059] And based on the target angle Δθ between the harvesting platform and the ground slope, calculate the forward and backward tilt angles of the harvesting platform:

[0060] .

[0061] By adopting the above technical solution, a unit vector of the vehicle's travel direction is constructed, and the slope s along the travel direction is calculated through terrain gradient projection or difference approximation. f This is then converted into the ground tilt angle. The target pitch angle of the platform is obtained by superimposing the target angle Δθ. This enables active planning of the platform's forward and backward tilt angles, allowing the target angle to be set according to the crop condition (such as maintaining a certain pitch angle when harvesting downhill), thus optimizing the quality of harvesting operations rather than simply following the terrain.

[0062] Furthermore, the specific steps of the cross slope contour control described in step S5 are as follows:

[0063] (1) Construct the vehicle's lateral unit vector T;

[0064] (2) Calculate the slope of the terrain along the transverse direction. ;

[0065] (3) Convert the transverse slope sy to the ground tilt angle ϕ ground =arctan(sy);

[0066] (4) Determine the target tilt angle of the harvesting platform based on the set lateral target angle Δϕ:

[0067]

[0068] This allows for contour control of the cross slope.

[0069] By employing the above technical solution, a lateral unit vector for the vehicle is constructed, and the lateral slope s is calculated. y Converted to ground tilt angle ϕ ground The target tilt angle ϕ is determined by superimposing the lateral target angle Δϕ, ensuring the platform maintains a predetermined attitude relationship with the ground in the transverse slope direction. This solves the problem that when operating on a transverse slope, if the platform is strictly level, an angle with the slope surface may result in missed cuts, while if it is strictly flush with the slope surface, it may lead to poor material conveying or tipping over. It achieves controllable attitude in the transverse slope direction, allowing adjustment of the platform's lateral tilt angle according to operational needs (such as maintaining a level position to ensure conveying stability, or flushing with the slope surface to reduce missed cuts), thus improving the safety and adaptability of transverse slope operations.

[0070] Furthermore, in step S6, the spatial transformation relationship between the platform coordinate system and the ground coordinate system is established, and the left and right endpoints of the platform are mapped to the ground coordinate system to obtain the target coordinates of the left and right endpoints. The specific method is as follows:

[0071] In the coordinate system of the harvesting platform itself, let the length of the harvesting platform be L. h The coordinates of the left and right endpoints are as follows:

[0072]

[0073] The attitude matrix is ​​constructed using the ZYX Euler angle sequence: first, rotate the vehicle's forward angle φ around the Z-axis of the ground coordinate system, then rotate the pitch angle θ around the Y-axis, and finally rotate the roll angle ϕ around the X-axis, i.e., R = R z (φ)R y (θ)R x (ϕ);

[0074]

[0075] Thus, the target coordinates of the left and right endpoints are obtained:

[0076] .

[0077] By adopting the above technical solution, the attitude matrix R(φ, θ, ϕ) is constructed using the ZYX Euler angle sequence (yaw-pitch-roll) to map the coordinates of the left and right endpoints in the platform's own coordinate system to the ground coordinate system through homogeneous transformation. This solves the problem that the platform endpoints and the vehicle body hinge points are in different coordinate systems, resulting in a lack of a unified spatial reference for direct distance calculation. A unified spatial mathematical description between the platform endpoints and the vehicle body hinge points is established, providing a precise geometric basis for subsequent inverse kinematics of actuator length.

[0078] Furthermore, in step S7, based on the spatial geometric relationship between the platform endpoints and the corresponding hinge points, the target extension length L of the left and right actuators is solved inversely. L ,L RThe specific methods are as follows:

[0079]

[0080] Where ||·| represents the Euclidean norm.

[0081] By adopting the above technical solution, and based on the Euclidean norm, the target extension length L of the left and right actuators can be solved by inversely using the target coordinates of the platform endpoint and the coordinates of the vehicle side hinge point. L ,L R It provides a closed-loop inverse kinematics algorithm, which has low computational cost and high real-time performance. It can be directly embedded into the controller to achieve millisecond-level solution and meet real-time control requirements.

[0082] Furthermore, in step S8, to improve the dynamic response performance of the actuator, a mapping relationship between the extension and retraction speeds of the actuator is constructed. The speed feedforward of the actuator is calculated based on the projection of the platform endpoint speed and the vehicle side hinge point speed onto the actuator linkage direction. This speed feedforward is then superimposed with the feedback control output based on the length error as a driving command. Specifically:

[0083] For any implementing agency Let the unit vector of its link direction be...

[0084]

[0085] If the platform endpoint velocity is vi and the vehicle side hinge point velocity is vBi, then the feedforward value of the extension / retraction speed of the actuator is:

[0086]

[0087] The VFI is then superimposed with the feedback control output based on the length error as the driving command.

[0088] By adopting the above technical solution, the unit vector in the direction of the actuator link is calculated, and the projection difference between the platform endpoint velocity and the vehicle side hinge point velocity in the link direction is used as the feedforward velocity v of the extension / retraction speed. fi And it is superimposed on the feedback control based on position error.

[0089] By introducing velocity feedforward compensation, a composite control structure of feedforward + feedback is formed, which significantly improves the dynamic response speed and tracking accuracy of the system and reduces transient errors when the terrain changes abruptly.

[0090] In summary, the present invention has at least one of the following beneficial technical effects:

[0091] (1) Through the collaborative work of the terrain information acquisition module and the vehicle attitude and position measurement unit, combined with coordinate transformation and geometric inverse algorithm, the system can calculate the target height and attitude angle of the harvesting platform center in real time. Based on the characteristics of the four-wheel independent drive chassis, the system can dynamically adjust the platform's ground clearance, front and rear tilt angles, and side tilt angles during vehicle movement, so that the harvesting platform always maintains the set target angle with the ground. This effectively solves the problem of inconsistent ground clearance and high crop loss rate of traditional harvesters when operating on complex terrains such as slopes and hills, and achieves high-precision terrain-following operation, significantly improving the adaptability to complex terrain.

[0092] (2) The present invention uses dual independent electric actuators to achieve three degrees of freedom flexible attitude adjustment, so that the harvesting and conveying module can simultaneously achieve three degrees of freedom attitude adjustment of overall lifting, pitching and tilting. Compared with the traditional single-axis adjustment mechanism, this solution can independently control the platform's pitching and tilting, and has a stronger ability to adapt to the combination of longitudinal and transverse slopes and a wider adjustment range.

[0093] (3) In this invention, the hook-up module adopts a fisheye joint to provide a universal swing connection, which forms a mechanical follow-up during the platform posture change process. The flexible connection between the harvesting and conveying module and the mobile platform can be realized without the need for a complex universal joint or ball joint structure. This structure not only simplifies the mechanical design and reduces the wear of parts, but also effectively absorbs the vibration and impact during the operation process, improving the overall reliability and service life of the system.

[0094] (4) Based on feedback control based on length error, the system of the present invention further constructs a mapping relationship of the extension and retraction speed of the actuator. By calculating the projection of the platform endpoint speed and the vehicle side hinge point speed on the actuator linkage direction, the speed feedforward is obtained and superimposed on the drive command. This control method effectively compensates for the rapid disturbance caused by terrain changes during vehicle movement, significantly improves the dynamic tracking accuracy and response speed of the actuator, and ensures that a stable contouring effect can still be maintained during high-speed operation.

[0095] (5) In this invention, the collection box can be flipped relative to the hanging module, realizing automatic unloading or transfer of the harvested material; this design works in conjunction with the terrain-adjusting system to maintain a stable connection between the collection box and the hanging module during the platform attitude adjustment process, and only drives the flipping when unloading, without the need for manual intervention, which significantly improves the work efficiency and automation level. Attached Figure Description

[0096] Figure 1 This is a flowchart of the adjustment method of the present invention.

[0097] Figure 2 This is a schematic diagram of the overall first-angle structure of the present invention.

[0098] Figure 3This is a schematic diagram of the overall second-angle structure of the present invention.

[0099] Figure 4 This is a schematic diagram of the mounting module structure in this invention.

[0100] Figure 5 This is a schematic diagram of the harvesting and conveying module in this invention.

[0101] Figure 6 This is a schematic diagram of the collection device structure in this invention.

[0102] Figure 7 This is a contour verification curve of the platform center height above the ground in this invention.

[0103] Figure 8 This is a graph showing the change in the height of the left and right ends of the platform above the ground in this invention.

[0104] Figure 9 The contour verification curve of the platform pitch angle as a function of longitudinal slope in this invention.

[0105] Figure 10 The conformal verification curve of the platform tilt angle as a function of the cross slope in this invention.

[0106] Figure 11 The target length and stroke constraint check curve of the left and right actuators in this invention.

[0107] In the diagram: mobile platform 100, mounting module 200, mounting bracket 201, lateral support 202, fisheye connector 203, longitudinal support 204, hinge seat 205, harvesting and conveying module 300, harvesting platform 301, conveying platform 302, first electric push rod 303, second electric push rod 304, hinge seat 305, collecting device 400, collecting box 401, connecting plate 402, mounting plate 403, hinge seat 404, third electric push rod 405, terrain information acquisition module 500, vehicle attitude and position measurement unit 600, controller 700. Detailed Implementation

[0108] To make the objectives, technical solutions, and advantages of this invention clearer, the embodiments of this invention will be described in detail below with reference to the accompanying drawings and specific examples. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of protection of this invention. This embodiment uses cabbage as an example, but the invention is equally applicable to other leafy vegetable crops with similar color characteristics.

[0109] Explanation of terms and symbols:

[0110] The ground coordinate system is denoted as {G}, with its Z-axis pointing vertically upwards; the platform coordinate system is denoted as {P}, with its origin located at the geometric center (i.e., the "platform center") of the servo platform body composed of the harvesting platform 301 and the conveying platform 302, and the platform length direction is defined as the x-axis direction of the {P} coordinate system.

[0111] The vehicle reference point is selected from a preset benchmark point on the mobile platform 100, and its planar coordinates in {G} are (x... v y v The vehicle's forward angle is φ. The platform center's planar coordinates in {G} are (x...). c y c The ground elevation at the center of the platform is z. c =h(x c y c The target height at the center of the platform is h. c .

[0112] Δh is the distance of the platform relative to the target on the ground; θ is the platform's pitch angle; ϕ is the platform's roll angle. ground ϕ ground These are the front and rear dip angles and the side dip angles of the ground, respectively, calculated from the terrain slope.

[0113] L h The platform length is preferably the distance between the hinge centers of the hinge seats 305 connecting the left and right sides of the follower platform body to the electric push rods 303 and 304; P L P R The target positions of the left and right endpoints of the platform in {G} are given, with the endpoints preferably taken as the hinge center of the aforementioned hinge seat 305; b L b R The position of the hinge point on the side of the electric actuator body in {G} is preferably taken as the hinge center of the hinge seat 305 on the mounting bracket 201 that connects to the electric actuator; L L L R These refer to the target / real-time extension / retraction lengths of the first electric actuator 303 and the second electric actuator 304, respectively. In one implementation, the hinge point b on the vehicle body side of the left and right actuators... L b R Within the vehicle structure, the offset vector of the vehicle reference point relative to its fixed geometric position in the vehicle reference coordinate system is obtained through assembly calibration and stored in the controller. The controller then obtains the position (x, y) of the vehicle reference point in the ground coordinate system. v y v After determining the vehicle's forward angle φ, the aforementioned offset vector is transformed by planar rotation to obtain b. L b R The coordinates in the ground coordinate system are used for the target length L of the subsequent actuator. L LR The spatial geometric inverse solution. d is the sampling distance for differential slope calculation.

[0114] In this paper, φ represents the vehicle's forward angle, and ϕ represents the platform's target roll angle; these are different physical quantities with different signs. ‖·‖ represents the Euclidean norm; P L P R These represent the target position vectors of the left and right endpoints of the platform in the ground coordinate system {G}, respectively.

[0115] Example

[0116] In this embodiment, as Figure 2-3 As shown, the automatic adjustment system for the harvesting platform is installed at the front end of the mobile platform 100, including a mounting module 200, a harvesting and conveying module 300, a collection device 400, a terrain information acquisition module 500, a vehicle attitude and position measurement unit 600, and a controller 700. The mounting module 200 is fixed to the front end of the mobile platform 100, serving as the installation reference and force transmission path for the harvesting and conveying module 300; the controller is electrically connected to electric push rod 303 and electric push rod 304, and communicatively connected to the terrain information acquisition module 500 and the vehicle attitude and position measurement unit 600, to achieve automatic adjustment of the height and attitude of the harvesting platform 301.

[0117] like Figure 4 As shown, the mounting module 200 consists of a mounting bracket 201, a transverse support 202, a fisheye connector 203, a longitudinal support 204, and a hinge seat 205. The mounting bracket 201 is fixed to the front end structure of the mobile platform 100 by welding or bolting. The mounting bracket 201 is a rigid frame structure with mounting surfaces for mounting the hinge components and actuators. The transverse support 202 is fixed to the mounting bracket 201 by welding, and a through hole is provided in the middle of the transverse support 202. A screw passes through the through hole and can move axially relative to the transverse support 202. Upper and lower fastening nuts are located on both sides of the transverse support 202 and are threaded onto the screw. The axial position of the screw is adjusted by adjusting the positions of the two fastening nuts, and then locked after adjustment, serving as a support / reference position adjustment and locking structure. The fisheye connector 203 is located at the end of the screw and provides a universal swing connection, allowing the hinge connected to it to follow the platform's posture changes. The longitudinal support 204 is fixed to the mounting bracket 201 to form a rotatable connection with the collecting device 400 and to provide support. The hinge seat 205 is fixedly mounted on the mounting bracket 201 to provide a rotatable connection point for the flipping drive or connecting components of the collecting device 400.

[0118] like Figure 5As shown, the harvesting and conveying module 300 includes a harvesting platform 301, a conveying platform 302, a first electric actuator 303, a second electric actuator 304, and a hinge seat 305. The harvesting platform 301 and the conveying platform 302 are fixedly connected or integrally formed to form the follower platform body. The hinge seat 305 includes a vehicle-side hinge seat mounted on the mounting bracket 201 and a platform-side hinge seat mounted on the follower platform body. The first electric actuator 303 and the second electric actuator 304 are arranged symmetrically on the left and right sides, and their two ends are rotatably connected to the corresponding vehicle-side hinge seat and platform-side hinge seat through pins, so that the electric actuators mainly bear axial loads during extension and retraction, and allow the follower platform body to produce changes in lifting, pitching, and tilting attitudes.

[0119] In addition, the fisheye joint 203 can be rotatably connected to the hinge seat 305 on the follower platform body or its connecting component via a pin, so that the fisheye joint 203 and its connection point form a follower rotating pair, thereby constraining the direction of platform movement and enhancing structural stability without rigidly constraining the changes in platform attitude.

[0120] like Figure 6 As shown, the collection device 400 includes a collection box 401, a connecting plate 402, a mounting plate 403, a hinge seat 404, and a third electric push rod 405. The connecting plate 402 is fixedly connected to the collection box 401 and is rotatably connected to the longitudinal support 204 or its connecting component on the hanging module 200 via a pin, allowing the collection box 401 to flip relative to the hanging module 200. The mounting plate 403 is fixedly connected to the collection box 401 and provides a mounting surface for the hinge seat 404. The hinge seat 404 is mounted on the mounting plate 403. The two ends of the third electric push rod 405 are rotatably connected to the hinge seat 205 and the hinge seat 404 via pins, respectively. When the third electric push rod 405 extends or retracts, it drives the collection box 401 to flip, thereby achieving unloading or transfer.

[0121] In the above structural assembly relationship, the first electric actuator 303 and the second electric actuator 304 are the active actuators for platform attitude adjustment, and their real-time extension and retraction lengths are denoted as L. L With L R Harvesting platform 301 and conveying platform 302 constitute the main body of the follower platform, and its geometric center is defined as the platform center; the platform length L calculated by the algorithm. h The preferred value is the distance between the hinge centers of the left and right platform hinge seats 305 of the follow-up platform body; in the algorithm, the hinge point b on the vehicle body side is... L b RThe hinge center is preferably located on the mounting bracket 201 corresponding to the hinge seat 305 on the vehicle side. The fisheye joint 203, the hinge seat 205, and all pin connections are servo rotary pairs, whose rotation angles passively change with the platform target attitude and the extension / retraction state of the push rod. Through the above-mentioned installation structure and motion relationship, a clear physical basis is provided for the subsequent terrain-based automatic height and attitude adjustment method, enabling the control system to solve the push rod target length based on the structural geometry, thereby realizing continuous terrain-based contour adjustment of the servo platform body.

[0122] The following is combined with Figure 1 This paper describes a method for automatically adjusting the height and attitude of a harvesting platform based on terrain contouring. Within a unified ground coordinate system, this method sequentially executes steps including platform center position calculation, terrain elevation acquisition, target ground clearance setting, terrain slope analysis, platform target attitude calculation, platform endpoint spatial position calculation, and inverse kinematics of the actuator target length. This establishes a continuous mapping relationship between vehicle pose and terrain elevation information and actuator control quantities, thereby enabling automatic contouring adjustment of the harvesting platform's height and attitude as the vehicle moves along changing terrain.

[0123] This invention utilizes a terrain-following-based method for automatic height and attitude adjustment of a harvesting platform to establish a geometric model of the vehicle and the harvesting platform in a unified ground coordinate system. The vehicle reference point can be selected as a structural feature point near the geometric center of the chassis or near the front axle; the position of this reference point in the ground coordinate system is denoted as (x...). v y v The angle between the vehicle's direction of travel and the x-axis of the ground coordinate system is denoted as the forward angle φ. The nominal front overhang distance between the center of the harvesting platform and the vehicle reference point in the longitudinal direction of the vehicle is denoted as d. rf Therefore, based on the vehicle's spatial position and forward angle, the relationship (x) can be used to determine the vehicle's position and forward angle. c y c )=(x v +d rf cosφ, y v +d rf (sinφ) determines the coordinates of the center of the harvesting platform in the horizontal plane.

[0124] To obtain the ground elevation of the platform center location, this embodiment introduces a terrain elevation function h(x, y). This function can be obtained by interpolation fitting from the digital elevation model of the work area, vehicle-mounted LiDAR, or online scanning data from a depth camera. Alternatively, it can be provided by a terrain model based on RTK-GNSS and ground calibration points, or a terrain database pre-stored in the farmland operation management system. The planar position (x, y) of the platform center is then determined. c y c Substituting the terrain function, we obtain the ground height z at the center of the platform. c =h(xc y c ).

[0125] During operation, the target ground clearance Δh of the harvesting platform relative to the ground is preset based on the crop type, expected stubble height, and platform structural safety requirements. In this embodiment, the target height at the platform center is set to h. c =z c +Δh, thus obtaining the target spatial coordinates (x, y) of the harvesting platform center in the ground coordinate system. c y c h c ), which is the basic position for overall platform contour control.

[0126] To enable the platform's pitch attitude to adapt to longitudinal changes in terrain, this embodiment utilizes the gradient information of the terrain elevation function at the platform's center to characterize the ground slope along the vehicle's direction of travel. This is achieved by analyzing the gradient information of the terrain elevation function at point (x...). c y c Taking the partial derivative at point (), we obtain the gradient vector ∇h = [∂h / ∂x, ∂h / ∂y, 0]. The unit vector e representing the vehicle's direction of travel... f The terrain slope s along the vehicle's direction of travel is obtained by taking the inner product of [cosφ, sinφ, 0] and the gradient vector. f =∇h·e f To facilitate correlation with the platform's pitch attitude, this slope is converted into the ground tilt angle θ. ground =arctan(s f Based on this, the target angle Δθ between the platform and the ground slope is preset according to the operational needs, and the forward and backward tilt angle of the harvesting platform is determined as θ = θ ground +Δθ enables the platform to achieve a balance between "ground-hugging contouring" and "maintaining a suitable pitch angle".

[0127] When the terrain gradient cannot be directly obtained, this embodiment can also use a difference method to approximate the terrain slope. A small distance d is selected along the vehicle's direction of travel, and δx = d·cosφ, δy = d·sinφ. Starting from the center of the platform, terrain elevation h(x) is sampled before and after the vehicle's direction of travel. c +δx, y c +δy) and h(x c −δx,y c −δy), based on the ratio of height difference to distance, s is approximately obtained. f ≈[h(x c +δx, y c +δy)−h(x c −δx,y c -δy)] / (2d), and then determine θ ground And the platform target tilt angle θ.

[0128] To maintain a reasonable distance between the left and right ends of the platform and the ground under cross slope conditions, this embodiment constructs a unit vector e along the vehicle's transverse direction at the platform's center position. y =[−sinφ,cosφ,0], where the projection of the terrain gradient in this direction is taken as the lateral slope s. y =∇h·e y And obtain the ground dip angle ϕ ground =arctan(s y Based on the requirements of crop harvesting for the platform's lateral attitude, the lateral target angle Δϕ is set, and the target side tilt angle of the harvesting platform is determined as ϕ=ϕ. ground +Δϕ allows for reasonable control of the height difference between the left and right ends of the platform on the transverse slope terrain.

[0129] When describing the platform endpoint positions, this embodiment sets the platform length as Lh in the platform's own coordinate system, and the coordinates of the left and right endpoints in the platform coordinate system are (−Lh, L ... h / 2,0,0) and (L h / 2, 0, 0). In the mechanical structure of this embodiment, the left and right endpoints preferably correspond to the hinge centers of the platform-side hinge seats 305 on the left and right sides of the follow-up platform body (i.e., the connection points between the first electric push rod 303, the second electric push rod 304 and the platform). The vehicle forward angle φ, the platform tilt angle θ, and the platform side tilt angle ϕ are combined into an attitude matrix R(φ, θ, ϕ), which is used to transform points in the platform coordinate system to the ground coordinate system. The target coordinates of the platform center in the ground coordinate system are marked as P. c =[x c y c h c ] T Then the target positions of the left and right endpoints of the platform in the ground coordinate system can be represented as P. i =P c +R(φ, θ, ϕ)·r i Where i represents the left endpoint and the right endpoint respectively, and r i Let P be the position vector of the corresponding endpoint in the platform coordinate system. The target coordinates P of the left and right endpoints can be obtained through the above relationship. L and P R The distance between the two endpoints is calculated from the Euclidean distance between these two coordinates.

[0130] To convert the platform's target position and attitude into specific actuator actions, this embodiment uses the first electric actuator 303 and the second electric actuator 304 as left and right linear actuators. Their vehicle-side connections are rotatably linked via vehicle-side hinge seats 305 on the mounting bracket 201, and their platform-side connections are rotatably linked via platform-side hinge seats 305 on the follower platform body. Assume the coordinates of the vehicle-side hinge points of the left and right actuators in the ground coordinate system are b... L and b R The spatial distance between the left and right endpoints of the harvesting platform and the corresponding hinge points can be obtained by the magnitude of the vector difference, i.e., L. L =‖P L -b L ‖, L R =‖P R -b R ‖. L L and L R As the target length of the corresponding actuator, the servo controller or drive device of the actuator is input to drive the electric push rod to extend and retract, so that the harvesting platform can reach the expected height and attitude in the ground coordinate system. The fisheye joint 203 and its connection point, and the hinge seat 205 and its connection point are follower rotating pairs in the above adjustment process, and their rotation angles passively change with the target attitude of the platform and the extension and retraction state of the push rod.

[0131] In situations where the terrain is highly undulating or the vehicle's attitude changes rapidly, directly using the slope and target attitude calculated from the terrain function to output the target length of the actuator may cause frequent acceleration and deceleration of the actuator due to the high-frequency components of the input signal, resulting in shocks and noise. This embodiment uses θ in the controller... ground ϕ ground The platform's target tilt angles θ and yaw angle ϕ, derived from these parameters, are filtered. Low-pass filtering, moving average, or first-order hysteresis can be used to limit the rate of attitude change, making platform attitude changes smoother, thereby reducing mechanical shock to the actuators and improving ride comfort. The controller operates at a fixed period T. s Run, T s The timeframe can be 10ms to 50ms. In differential slope calculation, the sampling distance d can be 0.1m to 1.0m, and can be adaptively set according to vehicle speed to balance noise suppression and slope response. For θ... ground ϕ ground The θ and ϕ derived therefrom are subjected to low-pass filtering or first-order hysteresis filtering. The filter cutoff frequency can be taken as 0.5Hz to 3Hz, and an upper limit is set on the attitude change rate to avoid impact on the actuator. When outliers are detected in the terrain data, the sliding window mean or surface fitting method is used to perform spatial smoothing before calculating the slope.

[0132] To further improve the dynamic response performance of the actuator, this embodiment can also be used in conjunction with position closed-loop control to calculate the velocity feedforward of the actuator. Based on the vehicle speed, the change in the platform center position, and the rate of change of attitude angle, the linear velocity vectors v of the left and right endpoints of the platform in the ground coordinate system can be obtained. L and v R Simultaneously, based on the kinematic relationship of the hinge point on the side of the vehicle body, the velocity vector v of the hinge point is obtained. BL and v BR For any actuator, the unit vector in the link direction can be represented as e. i =(P i -b i ) / ‖P i -b i If ||, then the feedforward value of the extension speed of the actuator can be approximately set as v. fi =e i ·[(v i -v Bi [)], which is the projection of "the linear velocity at the platform endpoint minus the linear velocity at the vehicle hinge point" onto the link direction. v fi When superimposed with the feedback control output formed by the difference between the target length and the actual length, the system phase lag can be reduced, and the actuator's ability to track changes in the target length can be improved.

[0133] In practical applications, the actuator has a limited physical travel range. When the target length L is calculated based on the terrain and target attitude... L or L R When the travel exceeds the minimum or maximum allowable travel of the corresponding actuator, this embodiment sets travel constraint processing logic in the controller. Prioritizes reducing the nominal front overhang distance d of the harvesting platform. rf Alternatively, the target angle Δθ between the platform and the ground slope can be appropriately relaxed, and the target position and attitude of the platform can be recalculated to ensure that the new target length falls within the feasible travel range of the actuator. Only in extreme cases where the travel constraints still cannot be met after adjustment will the controller limit the target length to the travel boundary and remind the operator to pay attention to the working environment or working method through the host computer interface or warning device. The travel constraint processing prioritizes ensuring the safe distance Δh between the platform and the ground, then the pitch angle θ, and then the roll angle ϕ; when recalculating parameters, the control output is kept continuous, and the rate of change of the target length is limited to avoid sudden jumps in the actuator.

[0134] To avoid excessive impact on the platform and actuators from abrupt terrain changes, this embodiment can also perform preprocessing at the terrain data level. Spatial filtering is applied to the slope values ​​calculated from terrain elevation functions or discrete elevation points to remove isolated outliers or noisy data. Furthermore, multi-point interpolation or surface fitting is used to smooth the terrain, making the platform's target attitude change present a continuous trend, thereby further improving the stability of contour control.

[0135] In a typical application scenario, the method and system of this invention are installed on a self-propelled combine harvester with a front-mounted harvesting platform. The terrain information acquisition module can obtain terrain elevation data online using a combination of vehicle-mounted lidar and GNSS. The vehicle attitude and position measurement unit outputs the vehicle's position and forward angle in the ground coordinate system. The controller collects the above information at fixed intervals and sequentially completes the calculation of the platform's center position and height, the calculation of terrain slope and platform target attitude, the transformation of platform endpoint coordinates, and the determination of the target length and velocity feedforward of the left and right actuators according to the method of this invention. Control commands are then sent to the actuator drive device via the CAN bus or other communication interfaces. Testing shows that when the platform operates in hilly terrain with varying longitudinal and transverse slopes, the ground clearance remains within a preset range, the platform's pitch and tilt attitudes smoothly follow terrain changes, the minimum safe distance between the blades and the ground is effectively guaranteed, the stubble height is stable, and the crop loss rate is significantly reduced.

[0136] Those skilled in the art will understand that various improvements or substitutions made to the vehicle reference point selection method, actuator arrangement, terrain elevation function construction method, and controller implementation method without altering the basic idea of ​​this invention should not be considered beyond the scope of protection of this invention. This invention, based on a terrain-following method and system for automatically adjusting the height and attitude of a harvesting platform, is also applicable to other forms of pre-harvesting devices or similar agricultural machinery that requires automatic adjustment of height and attitude according to terrain.

[0137] Simulation Verification Examples

[0138] To verify the feasibility and effectiveness of the automatic height and attitude adjustment method of the harvesting platform based on terrain contouring in this invention under structural conditions, this embodiment establishes a geometric model in the MATLAB environment that is consistent with the spatial arrangement of the harvesting platform, the attachment module and the left and right linear actuators, and constructs a terrain elevation function h(x, y) to describe the undulation characteristics of the working terrain, so as to simulate the complex terrain working condition where the longitudinal slope and the cross slope change simultaneously.

[0139] During the simulation, the control system acquires the vehicle's position (x, y) in the ground coordinate system at fixed intervals. v y v The angle φ between the vehicle's direction of travel and the ground coordinate system, combined with the nominal front overhang distance d of the harvesting platform center relative to the vehicle reference point.rf The position of the center of the computing platform in the horizontal plane (x c y c ). (x c y c Substituting the terrain elevation function h(x, y), we obtain the ground height h(x) at the center of the platform. c y c The target height at the center of the platform is obtained by superimposing a pre-set target distance Δh on the data.

[0140] h c =h(x c y c )+Δh

[0141] To enable the platform's attitude to adaptively adjust to changes in terrain, this embodiment characterizes the slope change at the platform's center location based on the gradient information of the terrain elevation function: the projection of the terrain gradient vector onto the vehicle's direction of travel is used as the longitudinal slope, which is then converted into a ground pitch reference angle. Combined with a preset attitude offset Δθ, the target platform pitch angle θ is obtained. ref The projection of the terrain gradient onto the vehicle's lateral direction is used as the lateral slope, which is then converted into a ground roll reference angle. Combined with a preset attitude offset Δϕ, the target roll angle ϕ of the platform is obtained. ref .

[0142] After obtaining the target height and attitude at the center of the platform, the target spatial position of the left and right endpoints of the platform in the ground coordinate system is calculated based on the attitude transformation relationship between the platform coordinate system and the ground coordinate system. Furthermore, based on the spatial geometric relationship between the platform endpoints and the corresponding hinge points on the vehicle structure, the target extension length of the left and right linear actuators is obtained by inverse solution, which serves as the control command input for the actuators.

[0143] (1) Platform center height above the ground simulation effect

[0144] like Figure 7 As shown, the ground height h(x) c y c The height of the platform center varies significantly with the terrain, while the actual height h is... c Able to closely follow the target center height h ref The trends of both are consistent. As can be seen from the out-of-limit statistics in the figure, under the center height tracking error threshold set in this embodiment, the platform center height did not exceed the limit during the entire simulation process (0 / 1251 out-of-limit points), and the maximum error was 0. This indicates that the center height planning method based on terrain elevation superposition Δh can effectively offset the influence of terrain undulation on the platform center height and achieve stable and reliable height contour control.

[0145] (2) Safety verification of the left and right ends of the platform above the ground

[0146] like Figure 8 As shown, the height of the platform's left and right ends above the ground changes continuously and smoothly with the terrain, and remains above the preset safety threshold h throughout the entire simulation process. min The statistics show that the number of points exceeding the limit in terms of the height of the endpoint above the ground is 0 / 1251, and the maximum exceedance is 0. This indicates that under the combined effect of longitudinal and transverse slopes, by jointly adjusting the platform height and attitude, the safety margin of the platform endpoint above the ground can be effectively guaranteed, avoiding the risk of ground contact or excessive suspension.

[0147] (3) Platform pitch and tilt attitude simulation effect

[0148] like Figure 9 and Figure 10 As shown, the actual platform pitch angle θ and the target pitch angle θ ref And the actual roll angle ϕ and the target roll angle ϕ of the platform ref All curves can continuously follow changes in the longitudinal and transverse slopes of the terrain, and the actual curves maintain a high degree of consistency with the target curves. The corresponding out-of-limit statistics are all 0 / 1251, with a maximum out-of-limit of 0, indicating that the attitude planning method based on terrain gradient information has good following consistency under the working conditions of this embodiment, can achieve stable contour adjustment of the platform attitude, and effectively suppress the difference in ground clearance between the left and right ends of the platform.

[0149] (4) Feasibility analysis of the target length and route of the implementing agency

[0150] like Figure 11 As shown, the target extension length of the left and right linear actuators changes continuously and smoothly over time, meeting the engineering requirements for the continuity of control commands. Simultaneously, through the interaction with the physical travel boundary [L] of the actuators... min L max The comparison shows that the target length of the left and right actuators is within the allowable range of the stroke throughout the simulation process, with 0 / 1251 exceeding the limit and a maximum exceeding the limit of 0. This indicates that under the current structural parameters, target distance from the ground, and attitude offset settings, the target length of the actuators obtained by the inverse solution has good executability.

[0151] (5) Comprehensive Analysis

[0152] In summary, simulation results systematically validated the method of this invention from four aspects: platform center height contouring, endpoint ground clearance safety, platform attitude contouring consistency, and actuator stroke feasibility. The results show that this terrain contouring-based automatic adjustment method for the height and attitude of the harvesting platform can achieve continuous and coordinated adjustment of platform height and attitude under complex undulating terrain conditions, ensuring endpoint ground clearance safety and meeting actuator stroke constraints, demonstrating good engineering feasibility and application value.

Claims

1. A terrain-adjustable harvesting platform system based on a four-wheel independent drive chassis, characterized in that, The regulating system includes: A mobile platform (100) is used to provide an installation reference and load-bearing support for other modules; A mounting module (200) is connected and installed to the mobile platform (100) for adjusting the angle of the harvesting and conveying module (300); A harvesting and conveying module (300) is connected and installed to the mobile platform (100) for harvesting and conveying. A collection device (400) is connected and installed with the mounting module (200) to realize the transfer of harvested materials; A terrain information acquisition module (500) is connected and installed with the mobile platform (100) to provide terrain elevation functions or discrete elevation data thereof; A vehicle attitude and position measurement unit (600) is built into the mobile platform (100) and is used to obtain the position of the mobile platform (100) in the ground coordinate system and the vehicle's forward angle; The controller (700), built into the mobile platform (100), is connected to the harvesting and conveying module (300), the collection device (400), the terrain information acquisition module (500), and the vehicle attitude and position measurement unit (600) for control.

2. The terrain-adjusting system for a harvesting platform based on a four-wheel independent drive chassis as described in claim 1, characterized in that: The mounting module (200) consists of a mounting bracket (201), a transverse support (202), a fisheye connector (203), a longitudinal support (204), and a hinge seat (205). The mounting bracket (201) is connected and fixed to the front end of the mobile platform (100). The transverse support (202) is connected and fixed to the mounting bracket (201). The fisheye connector (203) is adjustablely connected to the transverse support (202) and locked to it. It is used to provide a universal swing connection so that it can follow the platform's posture changes.

3. The terrain-adjusting system for a harvesting platform based on a four-wheel independent drive chassis according to claim 1, characterized in that: The harvesting and conveying module (300) consists of a harvesting platform (301), a conveying platform (302), a first electric push rod (303), a second electric push rod (304), and a hinge seat (305). The harvesting platform (301) and the conveying platform (302) are connected and fixed to form the follower platform body. The first electric push rod (303) and the second electric push rod (304) are arranged symmetrically on the left and right sides and are independent of each other. One end of each electric push rod is hinged to the moving platform and the other end is hinged to the follower platform body. The first electric push rod (303) and the second electric push rod (304) extend and retract in coordination with the rotation of the hinge seat (305) so that the follower platform body can achieve overall lifting, pitching, and tilting attitude adjustment.

4. The terrain-adjusting system for a harvesting platform based on a four-wheel independent drive chassis according to claim 1, characterized in that: The collecting device (400) consists of a collecting box (401), a connecting plate (402), a mounting plate (403), a hinge seat (404), and a third electric push rod (405); the connecting plate (402) is fixedly connected to the collecting box (401) and rotatably connected to the longitudinal support (207), so that the collecting box (401) can be flipped relative to the hanging module (200); The mounting plate (403) is fixedly connected to the collection box (401), the hinge seat (404) is mounted on the mounting plate (403), one end of the third electric push rod (405) is rotatably connected to the first hinge seat (205), and the other end is rotatably connected to the hinge seat (404). When the third electric push rod (405) extends or retracts, it drives the collection box (401) to flip over to achieve unloading or transfer.

5. A method for terrain-following adjustment of a harvesting platform based on a four-wheel independent drive chassis, characterized in that, The adjustment method involves the following steps: S1: In the ground coordinate system, based on the vehicle position (x v y v ) and the vehicle's forward angle φ, calculate the planar position (x) of the harvesting platform center. c y c ); S2: Based on the above planar position (x) c y c Using the terrain elevation function h(x, y), the elevation is mapped to the center of the harvesting platform, and the ground height at the platform center is calculated. ； S3: Set the target ground clearance Δh of the harvesting platform relative to the ground, and superimpose the target ground clearance constraint on the ground height at the center of the platform to determine the target height at the center of the harvesting platform: Thus, the coordinates of the platform's center target are obtained. ； S4: Calculate the terrain slope s based on the gradient or difference approximation of the terrain elevation function. f and lateral slope s y This is used to subsequently determine the target tilt angle ϕ of the platform; S5: The above transverse slope s y Converted to ground tilt angle ϕ ground And determine the target tilt angle ϕ of the harvesting platform according to the set lateral target angle Δϕ, so as to achieve cross slope contour control; S6: Set the center target coordinates P of the above-mentioned harvesting platform c Combined with the attitude matrix R(φ, θ, ϕ) formed by the vehicle's forward angle φ, the harvesting platform's forward and backward tilt angles θ, and the target's side tilt angle ϕ, a spatial transformation relationship from the platform coordinate system to the ground coordinate system is established. The left and right endpoints of the platform are mapped to the ground coordinate system to obtain the target coordinates of the left and right endpoints: ； S7: Obtain the coordinates of the left and right actuator hinge points on the vehicle body side in the ground coordinate system. , Based on the spatial geometric relationship between the platform endpoints and the corresponding hinge points, the target extension length L of the left and right actuators is solved inversely. L L R ; S8: The target length L is... L and L R As control commands are issued to the first electric actuator (303) and the second electric actuator (304) of the left and right actuators, the harvesting platform maintains the set ground clearance Δh and the target angle Δθ with the ground slope during the vehicle's movement, so that the harvesting platform can achieve terrain-based ground clearance and posture contour adjustment during the vehicle's movement.

6. The method for terrain-following adjustment of a harvesting platform based on a four-wheel independent drive chassis according to claim 5, characterized in that, The planar position (x) of the center of the harvesting platform in step S1 c y c The specific calculation method is as follows: Where, d rf This refers to the nominal front overhang distance of the harvesting platform center relative to the vehicle reference point.

7. The method for terrain-following adjustment of a harvesting platform based on a four-wheel independent drive chassis according to claim 5, characterized in that, The terrain elevation function h(x, y) mentioned in step S2 is obtained by any of the following methods or a combination thereof: (1) A digital elevation model obtained by prior surveying of the work area; (2) Terrain function constructed by online scanning of vehicle-mounted lidar, millimeter-wave radar or depth camera and interpolation algorithm; (3) Terrain model obtained by fitting RTK-GNSS and ground calibration points; (4) The terrain database pre-stored in the farmland operation management system.

8. The method for terrain-following adjustment of a harvesting platform based on a four-wheel independent drive chassis according to claim 5, characterized in that, The terrain slope s mentioned in step S4 f The specific calculation method is as follows: Construct the unit vector for the vehicle's direction of travel: Based on the topographic elevation function at point (x) c y c gradient at ) Establish the projection relationship between terrain slope and vehicle travel direction, and calculate its slope along the travel direction: terrain slope s f An approximate calculation using a differential method is employed. This involves selecting a preset distance along the vehicle's direction of travel and establishing a correlation between slope and distance based on terrain elevation differences. Specifically, a distance 'd' is selected along the vehicle's direction of travel, and... ,but ； The specific method for determining the target tilt angle ϕ of the platform is as follows: The above slope s f Converted to ground tilt angle And based on the target angle Δθ between the harvesting platform and the ground slope, calculate the forward and backward tilt angles of the harvesting platform: 。 9. The method for terrain-following adjustment of a harvesting platform based on a four-wheel independent drive chassis according to claim 5, characterized in that, The specific steps of the cross slope contour control described in step S5 are as follows: (1) Construct the vehicle's lateral unit vector T; (2) Calculate the slope of the terrain along the transverse direction. ; (3) Convert the transverse slope sy to the ground tilt angle ϕ ground =arctan(sy); (4) Determine the target tilt angle of the harvesting platform based on the set lateral target angle Δϕ: This allows for contour control of the cross slope.

10. The method for terrain-following adjustment of a harvesting platform based on a four-wheel independent drive chassis according to claim 5, characterized in that: In step S6, the spatial transformation relationship from the platform coordinate system to the ground coordinate system is established, and the left and right endpoints of the platform are mapped to the ground coordinate system to obtain the target coordinates of the left and right endpoints. The specific method is as follows: In the coordinate system of the harvesting platform itself, let the length of the harvesting platform be L. h The coordinates of the left and right endpoints are as follows: The attitude matrix is ​​constructed using the ZYX Euler angle sequence: first, rotate the vehicle's forward angle φ around the Z-axis of the ground coordinate system, then rotate the pitch angle θ around the Y-axis, and finally rotate the roll angle ϕ around the X-axis, i.e., R = R z (φ)R y (θ)R x (ϕ); Thus, the target coordinates of the left and right endpoints are obtained: 。 11. The method for terrain-following adjustment of a harvesting platform based on a four-wheel independent drive chassis according to claim 5, characterized in that: In step S7, based on the spatial geometric relationship between the platform endpoints and the corresponding hinge points, the target extension length L of the left and right actuators is solved inversely. L ,L R The specific methods are as follows: Where ||·| represents the Euclidean norm.

12. The method for terrain-following adjustment of a harvesting platform based on a four-wheel independent drive chassis according to claim 5, characterized in that, In step S8, to improve the dynamic response performance of the actuator, a mapping relationship between the extension and retraction speeds of the actuator is constructed. The speed feedforward of the actuator is calculated based on the projection of the platform endpoint speed and the vehicle side hinge point speed onto the actuator linkage direction. This speed feedforward is then superimposed with the feedback control output based on the length error as a drive command. Specifically: For any implementing agency Let the unit vector of its link direction be... If the platform endpoint velocity is vi and the vehicle side hinge point velocity is vBi, then the feedforward value of the extension / retraction speed of the actuator is: The VFI is then superimposed with the feedback control output based on the length error as the driving command.

Images