Attitude self-adjusting chassis system and attitude leveling method and path following method thereof

Abstract

The invention relates to a posture self-adjusting chassis system and a posture leveling method and a path following method thereof. The posture self-adjusting chassis system comprises a chassis frame, four independently-arranged four-connecting-rod lifting adjusting mechanisms, an independent driving and steering system, a posture detection module, a multi-sensor fusion navigation module and a whole vehicle control unit. Lifting adjustment of each wheel is achieved through a four-connecting-rod structure and a linear driver, and the wheels are driven by a hub motor and controlled by an independent steering actuator to achieve various moving modes such as corner adjustment, pivot steering and oblique movement. The double-axis attitude sensor is combined with the VCU and the chassis domain controller to construct a closed-loop control system, and the horizontal stability of the loading platform is kept in real time. The multi-sensor module fuses sensing data, and supports path planning, obstacle recognition and automatic navigation control. The chassis system has the advantages of being high in terrain self-adaptive capacity, high in control flexibility, good in loading cooperation precision, high in unmanned operation capacity and the like, and is suitable for various task requirements of spraying, picking, transporting and the like.

Description

Technical Field

[0001] This invention relates to the field of agricultural machinery and electric operating platform technology, and in particular to a self-adjusting chassis system and its attitude leveling method and path following method. Background Technology

[0002] In recent years, with the increasing demand for intelligent agriculture, special-purpose robots, and transportation equipment for complex terrains, multi-wheeled chassis systems with terrain adaptability and posture stability have received widespread attention. Traditional agricultural or engineering transportation equipment generally adopts rigid chassis structures and passive shock absorption devices, which are difficult to adapt to unstructured terrains such as hills, terraces, and woodlands, resulting in platform tilting, severe equipment vibration, reduced operating efficiency, and even safety hazards.

[0003] To improve platform operational stability, some technical solutions propose using suspension mechanisms or active lifting devices to achieve vehicle attitude leveling. However, these solutions still face challenges such as response lag, significant coupling interference between drive and damping, and high structural complexity, making it difficult to simultaneously achieve control accuracy and structural reliability. Furthermore, in nonlinear path-following scenarios, due to changes in ground adhesion conditions and differences in the spatial positions of each wheel, wheel slippage or speed mismatch can easily occur. Traditional differential control methods are mostly based on fixed ratios or empirical adjustments, lacking integrated modeling of key parameters such as turning radius and wheel speed feedback. This results in limited path-following accuracy, failing to meet the demands of high-precision operational scenarios.

[0004] Against this backdrop, there is an urgent need to provide a self-adjusting attitude chassis system and its control method that is simple in structure, responds quickly, has high control precision, and has high terrain adaptability. In particular, it is necessary to propose optimized designs for wheel height adjustment, differential control, and path following strategies to meet the requirements of stable operation and precise control in complex working environments. Summary of the Invention

[0005] The technical problem this invention aims to solve is: addressing the common issues of existing multi-wheeled work chassis during travel on uneven terrain and curved paths, such as difficulty in real-time stability of platform posture, high coupling between wheel lifting and shock absorption control, inaccurate matching of inner and outer wheel speeds, and the resulting slippage, yaw, and decreased work accuracy. This invention provides a posture self-adjusting chassis system and method that enables independent wheel lifting, steering, and driving, combined with posture closed-loop leveling control and inner and outer differential path following control, to effectively improve platform stability, ride comfort, and path following accuracy under complex working conditions.

[0006] To solve the above-mentioned technical problems, the present invention provides a self-adjusting attitude chassis system, comprising: The chassis frame is used to support the platform and install various control and actuator devices; Four wheel assemblies are disposed below the chassis frame, each wheel assembly including: A parallel four-bar linkage lifting and adjusting mechanism, comprising an upper linkage, a lower linkage, a wheel frame, a shock-absorbing linkage, a shock absorber, and a linear actuator. The upper and lower connecting rods are each hinged at one end to the chassis frame and at the other end to the wheel frame. The upper and lower connecting rods are parallel to each other, forming a parallelogram structure. One end of the shock-absorbing linkage is hinged to the chassis frame, and the other end is hinged to both the shock absorber and the piston rod of the linear actuator. The other end of the shock absorber is connected to the middle of the lower connecting rod, and the cylinder of the linear actuator is fixed to the chassis frame; A hub motor, mounted on the wheel frame, is used to directly drive the wheel to rotate; A steering actuator, with its cylinder body fixed to the wheel frame and its piston rod hinged to the wheel's steering rod, is used to control the wheel's steering angle; wherein... All four wheel assemblies are configured with independent lifting, independent drive and independent steering structures. The linear drive indirectly drives the wheel lifting through the shock absorber linkage and is decoupled from the shock absorber to form a composite buffer structure, which enhances the vertical buffering capacity of the lifting action and improves the chassis's adaptability to complex farmland terrain.

[0007] Optionally, the linear actuator is an electric push rod or a hydraulic cylinder, and the shock absorber is a hydraulic shock absorber or a spring-hydraulic composite buffer device. The extension stroke of the linear actuator and the working stroke of the shock absorber are configured in coordination to form a parallel composite structure for absorbing vertical impacts during the lifting process.

[0008] Optionally, the upper and lower links in the parallel four-bar linkage are formed by sheet metal welding or integral casting, the wheel frame is an integral steel structure shell, and each hinge point is equipped with a self-lubricating composite copper bushing or engineering plastic bushing bearing to improve wear resistance and operational stability in muddy and sandy environments.

[0009] Optionally, the steering drive is a linear electric push rod or a hydraulic cylinder, and the steering angle of each wheel can be independently controlled and continuously adjusted within a range of ±45°. The control system can realize multiple steering modes such as diagonal wheel reverse steering, four-wheel same-direction steering, and single-wheel fine adjustment.

[0010] Optionally, the hub motor is a 10-inch brushless direct-drive motor with low-speed, high-torque output characteristics and supports electronic differential control based on motor speed feedback. The differential control is achieved by the vehicle controller adjusting the speed of each wheel in real time to match the current steering angle and driving trajectory.

[0011] Optionally, the chassis system is equipped with an attitude detection module, a vehicle control unit (VCU), and a chassis domain controller. The attitude detection module includes a dual-axis attitude sensor for detecting the pitch and roll angles of the superstructure platform. The VCU calculates the platform offset error based on real-time attitude data and generates independent compensation commands for the four wheels according to the error amount. The chassis domain controller drives the lifting actuators respectively, forming a closed-loop adjustment process of attitude detection, compensation calculation, and execution drive.

[0012] Optionally, the attitude leveling process is a closed-loop control method, with a system control response time of no more than 0.5 seconds. The roll angle and pitch angle error of the leveled platform are controlled within ±1° to ensure the stability of the platform operation and the accuracy of equipment operation on uneven terrain.

[0013] Optionally, a mechanical vibration isolation device or buffer structure is provided between the chassis system and the superstructure platform to further reduce the high-frequency vibration of the platform caused by ground excitation, thereby improving the stability of the operating equipment and the safety of material transportation.

[0014] To address the aforementioned technical problems, the present invention also provides a platform attitude leveling method, applicable to the chassis system described in any of the above claims, wherein the method includes: Step 11: Collect the pitch and roll angle attitude data of the platform in real time using a dual-axis attitude sensor installed in the middle of the upper platform. Step 12: The vehicle control unit (VCU) processes the collected attitude data and calculates the target height compensation for the four wheels. Step 13: Send the height compensation command to the chassis domain controller, which will then control the lifting actuators of each wheel to make adjustments. Step 14: By continuously collecting and feeding back the platform's attitude status, a closed-loop control is formed until the platform's attitude angle error stabilizes within the set range.

[0015] To address the aforementioned technical problems, the present invention also provides a path following method based on inner and outer differential control, applicable to any of the above-mentioned attitude self-adjusting chassis systems, wherein the method includes: Step 21: Obtain the target driving path information and perform curvature analysis on the path to obtain the turning radius R and driving direction corresponding to the current driving segment; Step 22: Real-time acquisition of the steering angle, wheel speed, and spatial position parameters of the four wheels on the chassis; Step 23: Based on the steering radius R and the chassis track L, calculate the target differential ratio between the inner and outer wheels. , Wherein, the differential ratio The following relationship must be satisfied:

[0016] in: This is the differential adjustment coefficient; R is the vehicle's current turning radius; L is the wheelbase between the front and rear axles of the vehicle; And based on the differential ratio Calculate the target linear velocity for each wheel; Step 24: The vehicle control unit outputs corresponding drive control commands to each wheel hub motor according to the target linear velocity, so that the inner and outer wheels run in coordination at different speeds to achieve continuous following of the target path; Step 25: During path following, monitor the wheel speed feedback and ground adhesion status of each wheel in real time. When wheel speed deviation or tire slippage trend is detected, adjust the differential ratio. Alternatively, the target speed of each wheel may be dynamically adjusted to suppress slippage and maintain driving stability; among which The inner and outer differential control is not limited to the above differential ratio relationship. Steering angle compensation, slip correction or dynamic amplitude limiting strategies can also be introduced on the basis of the differential model to adapt to the path following requirements under different path curvatures and working conditions.

[0017] The beneficial effects of the technical solution of this invention are: The self-adjusting chassis system of this invention enables dynamic leveling, significantly improving the stability and accuracy of the work platform. Through an independent four-bar linkage lifting mechanism for each wheel and a closed-loop attitude control system, real-time pitch and roll angle detection based on dual-axis attitude sensors is achieved. The controller automatically calculates and adjusts the height compensation of each wheel, ensuring the platform remains approximately level at all times. This structure allows the platform to maintain the stability of the superstructure even in complex terrain conditions (such as uneven farmland or muddy ground inside greenhouses), effectively preventing uneven spraying, fruit bruising, or material tilting, thus ensuring operational quality and safety.

[0018] The self-adjusting chassis system of this invention possesses strong load-bearing capacity and excellent scalability, supporting various agricultural / industrial superstructure modules. Its high-strength four-bar structure and optimized chassis layout design enable the entire machine to carry a load exceeding 400 kg, stably mounting various types of task modules such as spray tanks, multi-layer harvesting baskets, transport boxes, and robotic arms. The chassis also supports modular superstructure interfaces, providing excellent scalability and adaptability to various application scenarios including spraying, harvesting, handling, and transportation.

[0019] The self-adjusting chassis system of this invention significantly improves maneuverability in confined spaces, adapting to high-density work environments. It employs a four-wheel fully independent drive and steering structure, with each wheel supporting ±45° steering angle adjustment. Combined with electronic differential control, it can achieve multiple modes such as diagonal wheel reverse steering (steering in place) and four-wheel same-direction steering (diagonal driving), with a minimum turning radius approaching zero. It is particularly suitable for high-density work environments with limited access width, such as greenhouses, orchards, or factories, significantly improving path planning flexibility and space utilization efficiency. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the chassis system in an embodiment of the present invention; Figure 2 This is a schematic diagram showing the changing states of the four-bar linkage lifting and adjusting mechanism in an embodiment of the present invention; Figure 3 This is a top view of the chassis system in an embodiment of the present invention; Figure 4 This is a schematic diagram illustrating the steps of the platform attitude leveling method in an embodiment of the present invention; Figure 5 This is a schematic diagram of the steps of the path following method in an embodiment of the present invention. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.

[0022] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0023] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0024] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0025] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0026] See Figure 1 , Figure 2 and Figure 3 As shown, the component selection and composition structure of the attitude self-adjusting chassis system in this embodiment are as follows, including: Chassis Frame 1: As the core support structure of the entire work platform, the chassis frame is made of high-strength steel, possessing excellent rigidity and stability. It not only supports the platform itself and houses various control and actuator devices, but also provides precise mounting positions for the four-link lifting and adjusting mechanism, independent steering system, and independent wheel hub electric drive system, ensuring the relative positional accuracy between components and thus guaranteeing the normal operation of the entire chassis system.

[0027] 2. The four-bar lifting and adjusting mechanism includes: Upper Linkage 2.1 and Lower Linkage 2.2: The upper and lower linkages are made of sheet metal welded together (5mm thick). This material and process choice ensures structural strength while also considering economy. One end of the upper linkage is connected to the chassis frame via a hinge, and the other end is also connected to the wheel frame via a hinge. The lower linkage is arranged parallel to the upper linkage, and its two ends are also hinged to the chassis frame and wheel frame respectively, thus forming a parallel four-bar linkage structure. This structure ensures the stability and accuracy of the wheel during lifting.

[0028] Wheel Carrier 2.3: The wheel carrier features a one-piece steel shell structure, providing a stable mounting base for the wheels, hub motors, and steering mechanism. Its robust structure helps improve the overall load-bearing capacity of the chassis.

[0029] Shock absorber link 2.4 and shock absorber 2.5: One end of the shock absorber link is hinged to the chassis frame, and the other end is hinged to the shock absorber and the piston rod of the linear actuator. The other end of the shock absorber is connected to the middle of the lower link. When the wheel is impacted by the ground, the shock absorber can effectively absorb energy and reduce the transmission of vibration to the chassis and superstructure platform. The shock absorber can be a hydraulic shock absorber or a spring-hydraulic composite buffer device to meet different cushioning requirements.

[0030] Linear Actuator 2.6: The linear actuator uses an electric push rod or a small RO hydraulic cylinder, with the cylinder body fixed to the chassis frame and the piston rod hinged to the middle of the shock absorber connecting rod. For lifting linear actuators, the thrust must be ≥4000N and the stroke ≥40mm to ensure sufficient power to adjust the wheel height and adapt to different terrains. The extension stroke of the linear actuator and the working stroke of the shock absorber are configured in tandem to form a parallel composite structure, jointly absorbing the vertical impact during the lifting process.

[0031] Hinge points: Each hinge point is equipped with a self-lubricating composite copper bushing or engineering plastic bushing bearing. These bearings can effectively reduce friction between components and improve wear resistance. Especially in muddy and sandy environments, they can ensure stable operation of the mechanism and reduce maintenance requirements.

[0032] Independent steering system 3, the independent steering system includes: Steering actuator: A linear actuator 3.1 is installed on each wheel carrier as the steering actuator, which can be a linear electric actuator or a hydraulic cylinder. The cylinder body is fixed to the wheel carrier, and the piston rod is hinged to the wheel's steering rod 3.2. The steering actuator requires a thrust ≥2000N and a stroke ≥60mm to ensure that the wheel steering can be effectively controlled by the kingpin 3.3 connected to the steering rod.

[0033] Steering angle control: By controlling the extension and retraction of the steering drive, the steering angle of each wheel can be controlled independently and continuously adjusted within a range of ±45°. This design enables the chassis to achieve multiple steering modes, such as diagonal wheel counter-steering, four-wheel steering in the same direction, and single-wheel fine-tuning, greatly improving the chassis's maneuverability and path planning flexibility in confined spaces.

[0034] The system also includes an independent in-wheel electric drive system 4, which uses 10-inch brushless in-wheel motors as drive units, one for each wheel. These in-wheel motors feature low-speed, high-torque output characteristics, meeting the chassis's drive requirements under various operating conditions. The motors directly drive the wheels, eliminating the need for a traditional transmission system, reducing structural space requirements, and making the chassis layout more compact. Simultaneously, the in-wheel motors support electronic differential control based on motor speed feedback. The vehicle controller can adjust the output speed of the four in-wheel motors in real time according to the driving direction (straight / turning) and wheel speed feedback, ensuring coordinated movement of all wheels during cornering, preventing slippage, and achieving precise trajectory control.

[0035] The attitude self-adjusting chassis system in this embodiment also has an attitude detection and control system, which includes the following components: Attitude detection module: A dual-axis attitude sensor is installed in the middle of the upper platform to detect the pitch and roll angles of the work platform in real time. This sensor features high precision and high sensitivity, enabling it to quickly and accurately detect minute changes in the platform's attitude.

[0036] Vehicle Control Unit (VCU): As the core controller of the vehicle, the VCU acquires data from the dual-axis attitude sensors in real time and processes and analyzes it. Based on the real-time attitude data, the VCU calculates the platform's offset error and generates independent compensation commands for all four wheels according to the error amount.

[0037] Chassis Domain Controller: The chassis domain controller receives compensation commands sent by the VCU and distributes them to the corresponding actuators, which drive the height actuators (i.e., linear actuators), drive motor speeds, and steering angles of the four wheels respectively, thereby achieving precise control of the chassis attitude and forming a closed-loop adjustment process of attitude detection, compensation calculation, and execution drive.

[0038] In addition, the attitude self-adjusting chassis system of this embodiment also has a multi-sensor fusion navigation and vehicle attitude control system, including the following components: Sensors: The platform integrates a variety of sensors, including lidar, binocular cameras, millimeter-wave radar, IMU (inertial measurement unit), and RTK (real-time positioning module).

[0039] LiDAR: It can acquire high-precision point cloud data of the surrounding environment, which is used to build 3D maps and identify obstacles, providing detailed environmental information for the chassis.

[0040] Binocular camera: assists in depth perception and target recognition, supplements visual texture information, complements LiDAR data, and improves the accuracy of environmental perception.

[0041] Millimeter-wave radar: It can still provide reliable obstacle detection capabilities in harsh environments such as rain, fog, and dust, ensuring the chassis can drive safely in complex environments.

[0042] IMU: Real-time measurement of chassis acceleration and angular velocity, providing attitude information. Combined with RTK, it enables high-precision attitude and position estimation, providing basic data for precise chassis control.

[0043] RTK: Provides centimeter-level positioning accuracy, ensuring accurate positioning of the chassis within the working area.

[0044] The attitude self-adjusting chassis system in this embodiment can achieve data fusion processing. Data from various sensors is synchronously acquired and fused on the GPU and chassis domain controller through a data fusion algorithm. Using spatiotemporal fusion algorithms based on Extended Kalman Filter (EKF) or deep learning, unified coordinate alignment, time synchronization, and anomaly filtering of sensor data are achieved, generating a global environment model and providing accurate data support for intelligent decision-making.

[0045] It can also realize intelligent decision-making and control. The VCU generates corresponding control commands based on the fusion perception results, drives the various actuators of the chassis, and realizes functions such as autonomous driving and path navigation, obstacle detection and obstacle avoidance decision-making, active adjustment of vehicle posture and suspension height, and coordinated control of the movement of the superstructure and chassis.

[0046] See Figure 4 As shown, the attitude self-adjusting chassis system of this embodiment mainly has a platform attitude leveling method, which includes the following steps: Step 11: Real-time acquisition of attitude data A dual-axis attitude sensor (such as a MEM step-type tilt sensor with an accuracy ≤0.1°) is installed at the geometric center of the superstructure platform (to ensure data representativeness). It continuously collects the platform's pitch angle (tilt angle along the chassis's longitudinal direction) and roll angle (tilt angle along the chassis's lateral direction) data at a sampling frequency of 50Hz. The sensor converts the collected analog signals into digital signals, which are then transmitted in real-time to the vehicle control unit (VCU) via the CAN bus, ensuring a data delay of ≤10m steps, providing a highly timely attitude reference for subsequent control.

[0047] Step 12: Calculation of target height compensation After receiving the attitude data, the VCU first performs filtering preprocessing (using a moving average filtering method to remove high-frequency vibration interference) to obtain the platform's current actual attitude angles (denoted as "current pitch angle α1, current roll angle β1"). Then, the VCU calls a preset attitude compensation algorithm: If the current pitch angle α1 is greater than the set horizontal threshold (e.g., ±1°), then the required height compensation for the front / rear wheels is calculated based on the chassis wheelbase (distance between front and rear wheels) and the transmission ratio of the four-bar linkage (e.g., the height the front wheels need to be raised = tan(α1) × wheelbase / 2). If the current roll angle β1 is greater than the set horizontal threshold, then the required height compensation for the left / right wheel is calculated based on the chassis wheel track (distance between left and right wheels) and the transmission ratio of the four-bar linkage (e.g., the height the left wheel needs to be raised = tan(β1) × wheel track / 2). If both pitch and roll deviations exist simultaneously, the overall height compensation for each wheel is calculated by combining them (e.g., the left front wheel needs to compensate for the height corresponding to both pitch and roll).

[0048] Step 13: Execution of compensation command The VCU converts the target height compensation for each wheel into a stroke command for the lifting actuator (such as the extension / retraction length of the electric actuator rod), and sends it to the chassis domain controller via the EtherCAT bus. Based on the command, the chassis domain controller independently controls the linear actuator of the corresponding wheel: for example, when the left front wheel needs to be raised by 5cm, the controller outputs an electrical signal of "extend 5cm" to the electric actuator rod of that wheel, driving the four-bar linkage to move the wheel frame upwards; if it needs to be lowered, it outputs a signal of "shorten the corresponding length". During execution, the stroke sensor of the lifting actuator provides real-time feedback on the current position, ensuring an action accuracy of ≤0.5mm.

[0049] Step 14: Closed-loop control and stability maintenance While the lifting actuator is operating, the dual-axis attitude sensor continuously collects platform attitude data and feeds it back to the VCU. The VCU compares the real-time attitude angle with a set horizontal threshold (±1°): If the actual attitude angle is already within the threshold range, a "stop" command is sent, and the lifting actuator maintains its current position. If the actual attitude angle still exceeds the threshold, repeat the calculation and execution process of steps 12-13 until the attitude error stabilizes within ±1° (control response time ≤ 0.5 steps).

[0050] This closed-loop process runs continuously during chassis driving or operation, ensuring that the superstructure platform always remains level.

[0051] See Figure 5 As shown, the attitude self-adjusting chassis system in this embodiment also mainly has a path following method based on inner and outer differential control, which includes the following steps: Step 21: Path Information Acquisition and Curvature Analysis The VCU acquires global coordinate information of the target driving path (such as the planned path of the work area) through a multi-sensor fusion navigation system (LiDAR + RTK + IMU), and extracts local path data of the current driving segment through a path parsing algorithm. Subsequently, the VCU performs curvature analysis on the local path: by fitting the arc of three consecutive coordinate points on the path, the turning radius R corresponding to the current driving segment is calculated (R=∞ if the path is a straight line), and the driving direction (forward / backward) is determined at the same time.

[0052] Step 22: Wheel status parameter acquisition The following sensors are used to collect the dynamic parameters of the wheels in real time: Steering angle: The travel sensor of each wheel steering drive provides feedback on the current steering angle (accuracy ≤ 0.5°). Wheel speed: The encoder of the hub motor provides feedback on the current wheel speed (accuracy ≤ 1 r / min). Spatial position parameters: Displacement sensors on the chassis provide feedback on the X / Y / Z coordinates of the wheels in the chassis coordinate system (used to confirm the real-time values ​​of track width and wheelbase).

[0053] All parameters are transmitted synchronously to the VCU via the CAN bus, with a sampling frequency ≥20Hz.

[0054] Step 23: Calculation of differential ratio and target linear velocity The VCU first obtains the real-time wheelbase L (distance between the center points of the front and rear axles) of the chassis, and then calculates the differential ratio based on the steering radius R using a formula. :

[0055] in: When R=∞ (driving in a straight line), =1, the inner and outer wheels rotate at the same speed; When R is small (small radius turning). <1, the inner wheel rotates at a lower speed than the outer wheel.

[0056] Subsequently, the VCU calculates the target linear velocity of each wheel based on the current travel speed v (preset by the task or adjusted in real time): Target linear velocity of the outer wheel:

[0057] Target linear velocity of the inner wheel:

[0058] If it is a four-wheel steering mode (such as crab walking), the target linear velocity is corrected in combination with the steering angle (for example, when driving diagonally, the wheel linear velocity needs to be decomposed into the path direction component).

[0059] Step 24: Output drive control commands The VCU converts the target linear velocity of each wheel into the target speed of the hub motor (speed = linear velocity / (π × wheel diameter)) and outputs PWM drive commands to the controller of each hub motor. After receiving the commands, the hub motor controller adjusts the motor voltage and current using a vector control algorithm to make the motor output the corresponding speed, achieving differential speed operation between the inner and outer wheels. For example, when the turning radius R = 1m and the wheelbase L = 1.2m, The inner wheel speed is approximately 0.17, which is 17% of that of the outer wheel, thus achieving a small-radius steering.

[0060] Step 25: Dynamic Correction and Slippage Suppression During path following, the VCU continuously monitors the following states: Wheel speed deviation: Compare the target speed of the wheel with the actual speed fed back by the encoder. If the deviation is greater than 5%, it is judged as wheel speed abnormality. Ground adhesion status: The tire slippage trend is identified by the current feedback of the hub motor (a sudden increase in current indicates slippage) or the change in wheel acceleration (a sudden drop in acceleration indicates slippage).

[0061] When an anomaly is detected, the VCU executes a dynamic correction strategy: If it's a slight slippage, adjust the differential ratio. (such as increasing) (Increase the rotational speed of the inner wheel). In the case of severe slippage, steering angle compensation (fine-tuning the steering angle to reduce steering resistance), slip correction (reducing the speed of the outer wheel), or dynamic limiting (limiting the maximum output torque of the motor) are introduced until the wheel speed deviation is restored to within 5% to ensure driving stability.

[0062] The attitude self-adjusting chassis system in this embodiment also has other methods for realizing intelligent and unmanned operation capabilities. Its overall architecture includes a multi-sensor fusion architecture adopted by the system, which consists of three main parts: an environmental perception system, an intelligent decision-making system, and an execution control system.

[0063] The environmental perception system, which integrates environmental perception and positioning, is primarily implemented through the following technologies: LiDAR: It continuously emits laser beams and receives reflected signals to acquire point cloud data of the surrounding environment, builds high-precision 3D maps, and is used to identify the location, shape, and distance of obstacles.

[0064] Binocular camera: It acquires images with parallax through two cameras, uses image processing algorithms to calculate the depth information of the target object, and assists LiDAR in target recognition and localization. It can provide more detailed information, especially for objects with visual texture features.

[0065] Millimeter-wave radar: Utilizes electromagnetic waves in the millimeter-wave band to detect information such as the distance, speed, and angle of target objects. It can operate stably under adverse weather conditions, such as heavy rain, dense fog, and sandstorms, providing reliable obstacle detection capabilities for the chassis.

[0066] IMU and RTK: The IMU measures the chassis's acceleration and angular velocity in real time, and obtains the chassis's attitude information through integration calculations; the RTK receives satellite signals and performs differential processing with the ground base station to achieve centimeter-level high-precision positioning. By fusing the data from the IMU and RTK, the chassis's position and attitude in space can be accurately determined.

[0067] And the fusion algorithm: a spatiotemporal fusion algorithm based on extended Kalman filter (EKF) or deep learning is used to process data from different sensors. First, the data from each sensor are unified to the same coordinate system and time-synchronized. Then, noise and abnormal data are removed through filtering algorithms, and finally a global environment model containing information such as environmental features, chassis attitude and position is generated.

[0068] Intelligent decision-making systems possess intelligent decision-making and path planning capabilities, primarily achieved through the following technologies: The path planning module generates the optimal driving path based on the work area map for tasks such as spraying, harvesting, and transportation, using either the Dijkstra step algorithm or a sampling-based RRT algorithm. These algorithms consider the distribution of obstacles on the map, terrain information, and the requirements of the work task to ensure that the planned path is both safe and efficient.

[0069] Obstacle avoidance and dynamic replanning combine real-time point cloud data acquired by LiDAR and visual perception information from binocular cameras to detect dynamic obstacles within the work area. Once an obstacle is detected, a local path correction algorithm is immediately activated to replan a new path to avoid the obstacle based on its location and the current state of the chassis, ensuring the continuity and safety of the operation.

[0070] Operational strategy decisions are made based on the type of operation (ground spraying, harvesting and transportation, loading and unloading coordination, etc.), selecting different movement modes (constant speed driving, path following, in-situ turning, diagonal driving, etc.). For example, when carrying out ground spraying operations, a constant speed driving mode may be selected, and the driving speed and chassis posture may be adjusted according to the row spacing of the crops and the coverage of the nozzles; during harvesting operations, in-situ turning and diagonal driving modes may need to be used frequently to adapt to the harvesting needs of fruits in different locations.

[0071] The execution control system achieves coordination between execution control and attitude, and mainly includes the following aspects: The VCU and chassis domain controller work together for control. The VCU is responsible for scheduling and monitoring the status of high-level tasks, receiving instructions from the intelligent decision-making system, allocating resources rationally based on the priority of the tasks and the current status of the chassis, and sending control commands to the chassis domain controller. The chassis domain controller is responsible for the precise control of actuators such as drive, steering, suspension, and lifting. Based on the instructions from the VCU, it adjusts the actions of each actuator in real time to ensure that the chassis travels along the predetermined path and attitude.

[0072] The chassis height and attitude are adjusted according to operational needs (e.g., crops of different heights, or operations on slopes). The chassis domain controller controls the independent lifting actuators (linear drives in the four-bar lifting adjustment mechanism) to adjust the chassis height and level attitude. For example, when traversing high furrows or encountering significant terrain undulations, the chassis height is raised to increase maneuverability; when operating on slopes, the height of each wheel is adjusted to keep the chassis level and ensure platform stability.

[0073] Wheel dynamic and terrain-adaptive control uses independent suspension sensors (such as displacement or pressure sensors mounted on a four-bar linkage) to monitor the position and force on the wheels in real time. Combined with the speed feedback from the wheel hub motor, it compensates for wheel bounce and uneven ground in real time. When a wheel encounters a bump or dent, the system automatically adjusts the output torque of the drive motor of that wheel and the length of the linear actuator to maintain a smooth driving trajectory and reduce the impact of bumps on operational accuracy.

[0074] The superstructure equipment is controlled collaboratively by integrating chassis attitude data with sensing information from the superstructure (such as a robotic arm) via a data bus or EtherCAT real-time network. For example, when the chassis automatically levels itself on a slope, its attitude data is transmitted to the robotic arm in real time. The robotic arm automatically compensates for changes in chassis attitude, enabling precise operation. This ensures that when the chassis attitude changes, the superstructure equipment can adjust its position and movements promptly, coordinating with the chassis movement and improving overall operational accuracy and collaborative performance.

[0075] Finally, it also includes job execution and closed-loop feedback functions. During job execution, the system continuously monitors job path deviation, obstacle distance, posture changes, and execution effects (such as spray uniformity and grasping accuracy). Various sensors installed on the chassis and superstructure acquire this information in real time and feed it back to the intelligent decision-making system. The intelligent decision-making system analyzes the feedback data based on an AI model to determine whether the current job meets expectations. If deviations are detected, it adjusts job parameters such as driving speed, steering angle, chassis height, and superstructure movements in a closed-loop adjustment. Simultaneously, the system logs key data during the job process, such as sensor readings, control commands, and job time, and supports remote data transmission. This data can be used for subsequent job optimization and AI self-learning, continuously improving the chassis's performance and job quality in different work scenarios.

[0076] In summary, the attitude self-adjusting chassis system of this invention enables dynamic leveling, significantly improving the stability and accuracy of the work platform. Through an independent four-bar linkage lifting mechanism for each wheel and an attitude closed-loop control system, real-time pitch and roll angle detection based on dual-axis attitude sensors is achieved. The controller automatically calculates and adjusts the height compensation of each wheel, ensuring the platform remains approximately level at all times. This structure allows the platform to maintain the stability of the superstructure even in complex terrain conditions (such as uneven farmland or muddy ground inside greenhouses), effectively preventing uneven spraying, fruit bruising, or material tilting, thus ensuring operational quality and safety.

[0077] The self-adjusting chassis system of this invention possesses strong load-bearing capacity and excellent scalability, supporting various agricultural / industrial superstructure modules. Its high-strength four-bar structure and optimized chassis layout design enable the entire machine to carry a load exceeding 400 kg, stably mounting various types of task modules such as spray tanks, multi-layer harvesting baskets, transport boxes, and robotic arms. The chassis also supports modular superstructure interfaces, providing excellent scalability and adaptability to various application scenarios including spraying, harvesting, handling, and transportation.

[0078] The self-adjusting chassis system of this invention significantly improves maneuverability in confined spaces, adapting to high-density work environments. It employs a four-wheel fully independent drive and steering structure, with each wheel supporting ±45° steering angle adjustment. Combined with electronic differential control, it can achieve multiple modes such as diagonal wheel reverse steering (steering in place) and four-wheel same-direction steering (diagonal driving), with a minimum turning radius approaching zero. It is particularly suitable for high-density work environments with limited access width, such as greenhouses, orchards, or factories, significantly improving path planning flexibility and space utilization efficiency.

[0079] The attitude self-adjusting chassis system of this invention simplifies the mechanical structure and maintenance process, significantly reducing long-term operating costs. It eliminates the traditional driveshaft and differential, instead employing a hub motor direct drive and modular linear drive structure, effectively reducing the number of drive chains and wear parts. The four-wheel suspension and steering systems are independent modules, featuring quick assembly and disassembly and unitized maintenance, greatly extending equipment lifespan and reducing maintenance costs. It is particularly suitable for harsh environments such as humid, hot, dusty, and high-frequency operation.

[0080] The attitude self-adjusting chassis system of this invention constructs a high-precision multi-sensor fusion perception system, supporting unmanned driving and obstacle avoidance operations. The system integrates multiple types of sensors, including LiDAR, binocular cameras, millimeter-wave radar, IMU, and RTK modules, and establishes a unified environmental model through extended Kalman filtering or deep fusion algorithms. The controller can automatically perform path planning, obstacle recognition, and obstacle avoidance decisions based on the perception results, enabling autonomous operation in unstructured farmland and complex industrial scenarios.

[0081] The attitude self-adjusting chassis system of the present invention can realize coordinated adaptive control of the vehicle attitude and chassis height, enhance the passability of complex terrain, and the control system can combine attitude data from IMU and RTK to dynamically control the lifting mechanism of each wheel to adapt to terrain changes such as slopes, areas with elevation differences, and ditches, and ensure the stability of the vehicle operation; at the same time, the chassis height can be adjusted according to the needs of the operation task to adapt to different crop heights or working conditions.

[0082] The superstructure of the attitude self-adjusting chassis system of the present invention can be linked with the chassis in real time to improve the accuracy of collaborative operation. The system uses a real-time communication mechanism between the VCU and the chassis domain controller to link and match the chassis attitude adjustment data with the control system of the superstructure execution equipment (such as a robotic arm), so as to realize automatic compensation control when the chassis jumps or drives on a slope, ensuring that the robotic arm or spraying device accurately performs its tasks.

[0083] The attitude self-adjusting chassis system of this invention possesses closed-loop feedback capability and an AI self-learning mechanism, supporting long-term intelligent optimization. During operation, the system continuously monitors attitude status, path deviation, and execution effect, and performs closed-loop adjustments in conjunction with an AI model. Operation log data can be used for subsequent parameter optimization and self-learning training, enabling the platform to possess adaptive enhancement capabilities during long-term operation.

[0084] The overall platform of the attitude self-adjusting chassis system of the present invention has high environmental adaptability and promotion value. It has achieved multiple innovations in structure, control and intelligent integration, and takes into account high load-bearing capacity, strong terrain adaptability and unmanned operation capability. It has practical feasibility and economic value for promotion and application in various types of operating environments such as orchards, tea gardens, greenhouses, factories, and logistics parks.

[0085] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made based on the description and illustrations of the present invention should be included within the protection scope of the present invention.

Claims

1. A self-adjusting attitude chassis system, characterized in that, include: The chassis frame is used to support the platform and install various control and actuator devices; Four wheel assemblies are disposed below the chassis frame, each wheel assembly including: A parallel four-bar linkage lifting and adjusting mechanism, comprising an upper linkage, a lower linkage, a wheel frame, a shock-absorbing linkage, a shock absorber, and a linear actuator. The upper and lower connecting rods are each hinged at one end to the chassis frame and at the other end to the wheel frame. The upper and lower connecting rods are parallel to each other, forming a parallelogram structure. One end of the shock-absorbing linkage is hinged to the chassis frame, and the other end is hinged to both the shock absorber and the piston rod of the linear actuator. The other end of the shock absorber is connected to the middle of the lower connecting rod, and the cylinder of the linear actuator is fixed to the chassis frame; A hub motor, mounted on the wheel frame, is used to directly drive the wheel to rotate; A steering actuator, with its cylinder body fixed to the wheel frame and its piston rod hinged to the wheel's steering rod, is used to control the wheel's steering angle; wherein... All four wheel assemblies are configured with independent lifting, independent drive and independent steering structures. The linear drive indirectly drives the wheel lifting through the shock absorber linkage and is decoupled from the shock absorber to form a composite buffer structure, which enhances the vertical buffering capacity of the lifting action and improves the chassis's adaptability to complex farmland terrain.

2. The chassis system as described in claim 1, characterized in that, The linear actuator is an electric push rod or a hydraulic cylinder, and the shock absorber is a hydraulic shock absorber or a spring-hydraulic composite buffer device. The extension stroke of the linear actuator and the working stroke of the shock absorber are configured in coordination to form a parallel composite structure for absorbing vertical impacts during the lifting process.

3. The chassis system as described in claim 2, characterized in that, The upper and lower links in the parallel four-bar linkage are formed by sheet metal welding or integral casting. The wheel frame adopts an integrated steel structure shell. Each hinge point is equipped with a self-lubricating composite copper bushing or engineering plastic bushing bearing to improve wear resistance and operational stability in muddy and sandy environments.

4. The chassis system as described in claim 3, characterized in that, The steering drive is a linear electric push rod or a hydraulic cylinder. The steering angle of each wheel can be independently controlled and continuously adjusted within a range of ±45°. The control system can realize multiple steering modes such as diagonal wheel reverse steering, four-wheel same-direction steering, and single-wheel fine adjustment.

5. The chassis system as described in claim 4, characterized in that, The hub motor is a 10-inch brushless direct drive motor with low-speed, high-torque output characteristics and supports electronic differential control based on motor speed feedback. The differential control is achieved by the vehicle controller adjusting the speed of each wheel in real time to match the current steering angle and driving trajectory.

6. The chassis system as described in claim 5, characterized in that, The chassis system is equipped with an attitude detection module, a vehicle control unit (VCU), and a chassis domain controller. The attitude detection module includes a dual-axis attitude sensor for detecting the pitch and roll angles of the superstructure platform. The VCU calculates the platform offset error based on real-time attitude data and generates independent compensation commands for the four wheels according to the error amount. The chassis domain controller drives the lifting actuators respectively, forming a closed-loop adjustment process of attitude detection, compensation calculation, and execution drive.

7. The chassis system as described in claim 6, characterized in that, The attitude leveling process is a closed-loop control method, with a system control response time of no more than 0.5 seconds. The roll and pitch angle errors of the leveled platform are controlled within ±1°, which is used to ensure the stability of the platform and the accuracy of equipment operation on uneven terrain.

8. The chassis system as described in claim 7, characterized in that, The chassis system and the superstructure platform are equipped with mechanical vibration isolation devices or buffer structures to further reduce the high-frequency vibration of the platform caused by ground excitation, thereby improving the stability of the operating equipment and the safety of material transportation.

9. A platform attitude leveling method, applicable to the chassis system as described in any one of claims 1 to 8, characterized in that, The method includes: Step 11: Collect the pitch and roll angle attitude data of the platform in real time using a dual-axis attitude sensor installed in the middle of the upper platform. Step 12: The vehicle control unit (VCU) processes the collected attitude data and calculates the target height compensation for the four wheels. Step 13: Send the height compensation command to the chassis domain controller, which will then control the lifting actuators of each wheel to make adjustments. Step 14: By continuously collecting and feeding back the platform's attitude status, a closed-loop control is formed until the platform's attitude angle error stabilizes within the set range.

10. A path following method based on inner and outer differential control, applicable to the attitude self-adjusting chassis system as described in any one of claims 1 to 8, characterized in that, The method includes: Step 21: Obtain the target driving path information and perform curvature analysis on the path to obtain the turning radius R and driving direction corresponding to the current driving segment; Step 22: Real-time acquisition of the steering angle, wheel speed, and spatial position parameters of the four wheels on the chassis; Step 23: Based on the steering radius R and the chassis track L, calculate the target differential ratio between the inner and outer wheels. , Wherein, the differential ratio The following relationship must be satisfied: ; in: This is the differential adjustment coefficient; R is the vehicle's current turning radius; L is the wheelbase between the front and rear axles of the vehicle; And based on the differential ratio Calculate the target linear velocity for each wheel; Step 24: The vehicle control unit outputs corresponding drive control commands to each wheel hub motor according to the target linear velocity, so that the inner and outer wheels run in coordination at different speeds to achieve continuous following of the target path; Step 25: During path following, monitor the wheel speed feedback and ground adhesion status of each wheel in real time. When wheel speed deviation or tire slippage trend is detected, dynamically correct the differential ratio λ or the target speed of each wheel to suppress slippage and maintain driving stability; wherein The inner and outer differential control is not limited to the above differential ratio relationship. Steering angle compensation, slip correction or dynamic amplitude limiting strategies can also be introduced on the basis of the differential model to adapt to the path following requirements under different path curvatures and working conditions.

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