Agricultural machine, steering control method and device thereof and medium

Abstract

The invention discloses an agricultural machine, a steering control method and device thereof and a medium, and belongs to the technical field of agricultural machines. The method comprises the following steps: estimating an ideal yaw velocity and an ideal side slip angle of the agricultural machine; the actual yaw velocity and the actual side slip angle of the agricultural machine are obtained; based on a first difference value between the ideal yaw velocity and the actual yaw velocity and a second difference value between the ideal side slip angle and the actual side slip angle, executing a feedback control algorithm to determine a compensation yaw moment of the agricultural machine; and based on the compensation yawing moment, adapting to the current steering working condition and carrying out rear wheel torque optimal distribution for the agricultural machinery. Smooth and stable walking and steering can be achieved, and the problem that the agricultural machine slips due to unreasonable drive torque distribution under the working condition that the adhesive force is very low is solved.

Description

Technical Field

[0001] The present application relates to the technical field of agricultural machinery, and in particular to an agricultural machinery and a steering control method, device and medium thereof. Background Art

[0002] At present, agricultural machinery with wire-controlled chassis is increasingly used in hilly and mountainous areas. The wire-controlled chassis eliminates the hydraulic steering structure, so its steering function must be achieved by controlling the differential speed of the left and right travel motors of the rear wheels, that is, to achieve rear wheel differential steering control.

[0003] In this regard, the rear-wheel differential steering control strategy adopted in the prior art is to achieve the effect of differential steering by controlling the speed of the left and right rear wheels to stabilize at the target speed. The main steps include: first, the speed of each driving wheel of the vehicle is solved by the Ackerman-Jeantand steering model, and then the required torque of each driving wheel is solved according to the steering wheel input angle, and the torque is directly controlled to adjust the rear wheel differential to achieve the target differential. This strategy makes the steering wheel input angle correspond to the rear wheel differential one by one, ensuring the consistency of the rear wheel differential. However, it has certain limitations in dynamic scenes. For example, the steering angle of the same rear wheel differential cannot be consistent on roads with different adhesion, resulting in different differential effects. For example, on a cement road, the steering wheel input angle a is used to calculate the rear wheel target differential b, and the vehicle can turn at this time. However, if the adhesion is very low (such as slippery muddy roads), the same steering wheel input angle a, the calculated rear wheel target differential is still b, and the rear wheels are very easy to slip in the mud, at this time the rear wheels slip on the spot and cannot turn, the left and right wheels also form a target differential b, but the agricultural machinery is not actually turning. Therefore, the steering wheel input angle and the actual steering of the vehicle cannot be kept consistent under various working conditions. Summary of the invention

[0004] The purpose of the embodiments of the present application is to provide an agricultural machinery and a steering control method, device and medium thereof, so as to at least partially solve the above-mentioned technical problems.

[0005] In order to achieve the above-mentioned objectives, the first aspect of the present application provides a steering control method for agricultural machinery, including: estimating the ideal yaw rate and ideal center of mass sideslip angle of the agricultural machinery; obtaining the actual yaw rate and actual center of mass sideslip angle of the agricultural machinery; based on a first difference between the ideal yaw rate and the actual yaw rate and a second difference between the ideal center of mass sideslip angle and the actual center of mass sideslip angle, executing a feedback control algorithm to determine the compensatory yaw moment of the agricultural machinery; and based on the compensatory yaw moment, optimizing the distribution of rear wheel torque for the agricultural machinery according to the current steering condition.

[0006] In an embodiment of the present application, before the estimation, the steering control method further includes: performing an initial distribution of rear wheel torque for the agricultural machinery based on a current steering wheel input angle.

[0007] In the embodiment of the present application, the estimating the ideal yaw angular velocity and the ideal center of mass sideslip angle of the agricultural machinery includes calculating the ideal yaw angular velocity ω of the agricultural machinery using the following formula: rd :

[0008]

[0009] Where, L is the wheelbase of the vehicle, V x is the longitudinal speed of the agricultural machinery, and K is the stability coefficient. The ideal center of mass side slip angle β of the agricultural machinery is estimated by the following formula: d :

[0010] β d ≈δ

[0011] Among them, δ is the real-time steering wheel input angle.

[0012] In the embodiment of the present application, the obtaining of the actual yaw angular velocity and the actual center of mass sideslip angle of the agricultural machinery comprises: reading the actual yaw angular velocity ω of the agricultural machinery from a pre-installed angular velocity sensor r ; and calculating the actual center of mass sideslip angle β of the agricultural machinery according to the following formula:

[0013]

[0014] Among them, V x is the longitudinal speed of the agricultural machinery, a y is the lateral acceleration of the agricultural machinery, and Δt is the preset processing period.

[0015] In an embodiment of the present application, the feedback control algorithm is a fuzzy PID algorithm.

[0016] In an embodiment of the present application, the optimized distribution of rear wheel torque for the agricultural machinery adapted to the current steering condition includes any one or more of the following: in an oversteering condition, controlling the inner wheel of the rear wheels to reduce the output torque; in an understeering condition, controlling the outer wheel of the rear wheels to increase the output torque; in a ramp spinning condition, controlling the outer wheel of the rear wheels to reduce the output torque; and in a driving slip condition, controlling both the inner and outer wheels of the rear wheels to reduce the output torque.

[0017] A second aspect of the present application provides a steering control device for an agricultural machinery, comprising: an ideal parameter estimation module, for estimating an ideal yaw rate and an ideal sideslip angle of the agricultural machinery in response to the steering condition of the agricultural machinery; an actual parameter acquisition module, for acquiring the actual yaw rate and the actual sideslip angle of the agricultural machinery; a control module, for executing a feedback control algorithm to determine a compensatory yaw moment of the agricultural machinery based on a first difference between the ideal yaw rate and the actual yaw rate and a second difference between the ideal sideslip angle and the actual sideslip angle of the agricultural machinery; and a compensatory torque distribution module, for optimizing the distribution of rear wheel torque of the agricultural machinery based on the compensatory yaw moment and adapted to the current steering condition.

[0018] In the embodiment of the present application, the ideal parameter estimation module is configured to calculate the ideal yaw angular velocity ω of the agricultural machinery using the following formula: rd :

[0019]

[0020] Where, L is the wheelbase of the vehicle, V x is the longitudinal speed of the agricultural machinery, and K is the stability coefficient.

[0021] Furthermore, the ideal parameter estimation module is configured to estimate the ideal center of mass sideslip angle β of the agricultural machinery using the following formula: d :

[0022] β d ≈δ

[0023] Among them, δ is the real-time steering wheel input angle.

[0024] In the embodiment of the present application, the actual parameter acquisition module is configured to: read the actual yaw angular velocity ω of the agricultural machinery from the pre-installed angular velocity sensor r ; and calculating the actual center of mass sideslip angle β of the agricultural machinery according to the following formula:

[0025]

[0026] Among them, V x is the longitudinal speed of the agricultural machinery, a y is the lateral acceleration of the agricultural machinery, and Δt is the preset processing period.

[0027] In an embodiment of the present application, the compensating torque distribution module is configured to perform any one or more of the following: in an oversteering condition, controlling the inner wheel of the rear wheels to reduce the output torque; in an understeering condition, controlling the outer wheel of the rear wheels to increase the output torque; in a ramp spinning condition, controlling the outer wheel of the rear wheels to reduce the output torque; and in a driving slip condition, controlling the inner wheel and / or the outer wheel of the rear wheels to reduce the output torque.

[0028] The third aspect of the embodiment of the present application also provides a steering control device for agricultural machinery, comprising: a memory configured to store instructions; and a processor configured to call the instructions from the memory and to implement any of the above-mentioned steering control methods when executing the instructions.

[0029] A fourth aspect of the embodiments of the present application also provides an agricultural machinery comprising any of the above-mentioned steering control devices.

[0030] A fifth aspect of an embodiment of the present application further provides a machine-readable storage medium, on which instructions are stored, and the instructions are used to enable a machine to execute any of the above-mentioned steering control methods.

[0031] Through the above technical scheme, the embodiment of the present application utilizes the relationship between the yaw moment and the yaw angular velocity and the sideslip angle of the center of mass to calculate the ideal value of the sideslip angle of the center of mass and the difference between the ideal value and the actual value of the yaw angular velocity. The compensatory yaw moment calculated by feedback control is used to redistribute the rear wheel torque in combination with the steering condition to achieve smooth and stable walking and steering, thereby solving the problem of slipping of agricultural machinery caused by unreasonable distribution of driving torque under conditions with very low adhesion.

[0032] Other features and advantages of the embodiments of the present application will be described in detail in the subsequent specific implementation section. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings are used to provide a further understanding of the embodiments of the present application and constitute a part of the specification. Together with the following specific implementations, they are used to explain the embodiments of the present application, but do not constitute a limitation on the embodiments of the present application. In the accompanying drawings:

[0034] Figure 1 A schematic diagram of a flow chart of a steering control method for agricultural machinery according to an embodiment of the present application is schematically shown;

[0035] Figure 2 A flowchart schematically shows an example of an implementation of a steering control method according to an embodiment of the present application;

[0036] Figure 3 A linear two-degree-of-freedom model of an agricultural machine is schematically shown;

[0037] Figure 4 The schematic diagram schematically shows the principle of estimating the compensation yaw moment based on the fuzzy PID control algorithm according to an example of an embodiment of the present application;

[0038] Figure 5 Schematically shows Figure 4 Schematic diagram of the principle of the fuzzy PID control algorithm;

[0039] Figure 6 A schematic diagram of a process flow of an example ramp spin control according to an embodiment of the present application is schematically shown;

[0040] Figure 7 A structural block diagram of a steering control device for agricultural machinery according to an embodiment of the present application is schematically shown; and

[0041] Figure 8 The structural block diagram of another steering control device according to an embodiment of the present application is schematically shown.

[0042] Description of Reference Numerals

[0043] 100 Ideal parameter estimation module 200 Actual parameter acquisition module

[0044] 300 control module 400 compensation torque distribution module DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. It should be understood that the specific implementation methods described herein are only used to illustrate and explain the embodiments of the present application, and are not used to limit the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0046] It should be noted that if the embodiments of the present application involve directional indications (such as up, down, left, right, front, back...), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0047] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present application, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0048] Before introducing the steering control method for agricultural machinery according to the embodiment of the present application, some terms involved in the embodiment of the present application are briefly introduced here to facilitate a better understanding of the embodiment of the present application.

[0049] 1. Wire-controlled chassis: an emerging chassis system that replaces traditional mechanical connections with wires, which greatly reduces traditional connection components such as mechanical, hydraulic, and pneumatic, and realizes vehicle travel, steering and other functions based on an electric drive system rather than mechanical control. The embodiment of the present application takes a wheel-track compound tractor equipped with a wire-controlled chassis as an example. The front wheels of the tractor are tracks, and the left and right rear wheels are conventional hinged tires. The tracks and the left and right rear wheels are independently driven by corresponding wheel-side motors. However, it should be understood that the steering control method of the embodiment of the present application is also applicable to other types of agricultural machinery with a wire-controlled chassis, such as combine harvesters.

[0050] 2. Distributed electric drive control: refers to the technology of distributing the control functions of the electric drive system to multiple control units. For example, each motor drives a wheel or track, and each motor has an independent control unit, and the vehicle controller (VCU) communicates and coordinates these control units through the vehicle communication network. The steering control method of the embodiment of the present application is based on distributed electric drive control, that is, a separate torque distribution is performed for each motor to achieve rear wheel differential steering. Distributed electric drive control can greatly reduce the turning radius and improve the maneuverability and flexibility of the wire-controlled chassis in hilly and mountainous areas. It should be noted that for the corresponding wheel or track, the driving torque it receives causes its rotation speed to change. This is common knowledge in the field and will not be repeated here.

[0051] 3. Slope spinning condition: Taking a wheel-track tractor as an example, when the gear is in the forward gear and the steering wheel input angle reaches the maximum value, the accelerator pedal is pressed at this time, the track motor does not output torque, and the left and right rear wheels output torques of equal magnitude and opposite directions according to the direction of the steering wheel, so that the left and right rear wheels rotate in opposite directions to achieve the effect of spinning. The embodiment of the present application is particularly aimed at the slope spinning condition, because the whole vehicle has only lateral driving force but no forward traction in the spinning state, so when spinning on a sloped road, the component of the whole vehicle's own gravity along the slope direction will cause the whole vehicle to slide downward (i.e., slide down the slope), and the steering control strategy based on the rear wheel target differential in the prior art cannot achieve vehicle steering under this condition.

[0052] 4. Driving slipping conditions: Agricultural machinery has very complex operating conditions in hilly and mountainous areas. When driving in the field, there are obstacles (such as ridges, etc.), ditches, and driving on slippery muddy ground, which may cause slipping and getting stuck. The present application embodiment summarizes this type of condition as a driving slipping condition, which refers to a condition where steering slipping is prone to occur. In addition, the above-mentioned slope spinning condition and the driving slipping condition here can be uniformly understood as a condition with very low adhesion in the present application embodiment.

[0053] 5. Yaw moment: When agricultural machinery performs differential steering, the left and right rear wheels output driving torques of different sizes and directions, so that the left and right wheels form a differential, thereby generating a steering torque, which is the yaw moment. Therefore, the size of the yaw moment is related to the size of the differential between the left and right wheels. Therefore, during the differential steering process, the size of the left and right wheel output torque is adjusted to control the size of the left and right wheel differential, thereby achieving the effect of increasing or decreasing the yaw moment and bringing the yaw moment closer to the expected value. Accordingly, the embodiment of the present application considers determining the compensation yaw moment and optimizing the rear wheel torque distribution based on the compensation yaw moment to achieve differential steering under various steering conditions. In addition, it should be noted that, in combination with the scenario, the terms "torque" and "torque" involved in the embodiment of the present application can be understood equivalently.

[0054] 6. Yaw angular velocity: For the vehicle coordinate system with the front direction (i.e. longitudinal direction) as the X-axis, the vertical direction (i.e. yaw direction in the embodiment of the present application) as the Z-axis, and the direction perpendicular to the X-axis and Z-axis (i.e. lateral direction) as the Y-axis, the yaw angular velocity refers to the angular velocity of the vehicle along the Z-axis when the agricultural machinery is turning or spinning.

[0055] 7. Side slip angle: refers to the angle between the vehicle's center of mass velocity direction and the above-mentioned X-axis.

[0056] 8. Inner wheel and outer wheel: For the two rear wheels, when the vehicle spins or turns, the tire on the turning direction is the inner wheel, and the tire on the other side is the outer wheel. For example, when turning left, the left rear wheel is the inner wheel, and the right rear wheel is the outer wheel, and vice versa.

[0057] Figure 1 The flowchart of a steering control method for agricultural machinery according to an embodiment of the present application is schematically shown. Figure 1 As shown, the method may include the following steps S100-S400.

[0058] Step S100, estimating the ideal yaw angular velocity and the ideal sideslip angle of the center of mass of the agricultural machinery.

[0059] In the embodiment of the present application, whether the agricultural machinery starts to turn is determined by detecting the steering wheel input angle δ, and when δ>0, it indicates that the whole vehicle is turning. At this time, the steering control method also includes: performing an initial distribution of rear wheel torque for the agricultural machinery based on the current steering wheel input angle. The initial rear wheel differential can be obtained through the initial distribution of rear wheel torque, and the subsequent steps of the present application are intended to adjust the initial rear wheel differential to adapt to the corresponding steering conditions.

[0060] In addition, the embodiment of the present application reflects the dynamic characteristics of agricultural machinery in the longitudinal, lateral and yaw directions by establishing a dynamic model of the entire vehicle operation process, and calculates the relationship between the yaw moment and the yaw angular velocity and the sideslip angle of the center of mass, and then estimates the ideal yaw angular velocity and the ideal sideslip angle of the center of mass.

[0061] The specific rear wheel torque initial distribution process and ideal value estimation process will be described below with examples and will not be elaborated here.

[0062] Step S200, obtaining the actual yaw angular velocity and the actual center of mass sideslip angle of the agricultural machinery.

[0063] In the embodiment of the present application, the actual yaw angular velocity and the actual center of mass sideslip angle of the agricultural machinery can be directly measured by pre-installing an angular velocity sensor and an angle sensor. However, due to the price and installation difficulty of the angle sensor associated with the center of mass position, a more preferred actual center of mass sideslip angle can be used, which will also be described in conjunction with examples below and will not be repeated here.

[0064] Step S300, executing a feedback control algorithm to determine a compensating yaw moment of the agricultural machinery based on a first difference between the ideal yaw rate and the actual yaw rate and a second difference between the ideal center of mass sideslip angle and the actual center of mass sideslip angle.

[0065] Among them, feedback control is one of the most common and important control strategies in automatic control systems. It measures the output signal and compares it with the expected signal to generate a difference signal, and then adjusts the input according to the difference signal to achieve the control target. Therefore, based on the known first difference and the second difference, and taking the yaw moment of the whole vehicle as the control target, this step S300 is easy to obtain the compensation yaw moment through the feedback control algorithm, so that the yaw moment of the whole vehicle approaches the set expected value. The embodiment of the present application will preferably adopt a fuzzy PID control algorithm to achieve the optimal control effect. The specific implementation scheme will also be described in conjunction with examples below, and will not be repeated here.

[0066] Step S400: Based on the compensated yaw moment, the rear wheel torque of the agricultural machinery is optimally distributed according to the current steering condition.

[0067] Among them, the steering conditions include oversteering conditions, understeering conditions, ramp spinning conditions and driving slipping conditions. In order to make the yaw moment of the whole vehicle approach the set expected value, the rear wheel torque distribution can be performed according to different steering conditions based on the calculated compensation yaw moment. The specific rear wheel torque distribution scheme under each steering condition will also be described in conjunction with examples below, and will not be repeated here.

[0068] Figure 2 The flowchart of the differential steering control example implemented by the steering control method of the agricultural machinery according to the embodiment of the present application is schematically shown. Figure 2 As shown, in the example, the corresponding differential steering control process includes steps S1-S8 of the following steps.

[0069] Step S1, obtaining driving state parameters and input control parameters.

[0070] The driving state parameters include vehicle speed, etc., and the input control parameters mainly include the steering wheel input angle δ.

[0071] Step S2, determine whether the steering wheel input angle δ is greater than 0, if so, continue to step S3, otherwise mark the current steering situation.

[0072] Step S3: initial differential torque distribution.

[0073] When it is detected that the steering wheel input angle δ>0, the torque of the chassis drive motor can be initially distributed through the initial torque distribution strategy, for example, the outer wheel torque is linearly increased and the inner wheel torque is reduced according to the size of δ, so that the left and right wheels form a preliminary differential.

[0074] For the initial torque distribution strategy, for example, first, according to the current input angle δ of the steering wheel (positive to the right, negative to the left), adjust the initial torque distribution ratio of the rear wheels:

[0075]

[0076] Among them, θ L is the torque distribution coefficient of the left wheel motor, θ R is the torque distribution coefficient of the right wheel motor, δ MAX is the maximum steering wheel angle, and k is the torque distribution coefficient.

[0077] Secondly, according to the total output torque of the current drive motor, the total output torque is distributed to each drive motor according to the torque distribution coefficient.

[0078] Step S4, determining an ideal yaw rate and an ideal sideslip angle of the center of mass.

[0079] Specifically, the idea of ​​determining the ideal value is: according to the steering wheel input angle and the relevant parameters of the vehicle after the initial torque is currently allocated, the parameters are input into the theoretical model to calculate the ideal yaw rate and the ideal center of mass sideslip angle. The subsequent steps are to further compare the ideal value with the actual yaw rate and the actual center of mass sideslip angle to make steering corrections.

[0080] Based on this idea, for example, Figure 3 The linear two-degree-of-freedom model shown in FIG. 1 is a linear two-degree-of-freedom model, where Fyrl and Fxrl represent the lateral force and longitudinal force of the ground on the left rear wheel, Fyrr and Fxrr represent the lateral force and longitudinal force of the ground on the right rear wheel, Fxf and Fyf represent the lateral force and longitudinal force of the ground on the front track, V represents the vehicle speed, V represents the vehicle speed, y represents the lateral velocity (i.e., the component of the vehicle speed V on the Y axis), β represents the sideslip angle of the center of mass, ω r represents the yaw angular velocity.

[0081] according to Figure 3 The kinetic model can further obtain the following kinetic equation:

[0082]

[0083] Where m represents the vehicle mass, δ represents the steering wheel input angle, and v y represents the longitudinal velocity of the center of mass, v x represents the lateral velocity of the center of mass, γ represents the yaw angular velocity, C f , C r They represent the cornering stiffness of the front wheel (or front track) and the rear wheel, β represents the center of mass side slip angle, a and b represent the distance from the front axle to the center of mass and the distance from the rear axle to the center of mass, respectively.z Represents the vehicle's moment of inertia about the vertical axis.

[0084] Furthermore, the ideal yaw rate is calculated using a linear two-degree-of-freedom vehicle model that performs constant circular motion. Specifically, under ideal conditions, the lateral acceleration and yaw angular acceleration are all 0. According to the Ackerman equation, the ideal yaw rate of the vehicle can be obtained:

[0085]

[0086] Where L is the wheelbase of the vehicle, and L = a + b, V x is the longitudinal speed of the agricultural machinery, and K is the stability coefficient. K is related to the cornering stiffness of the front and rear wheels, and is a fixed value, which can be obtained by looking up the table.

[0087] Furthermore, according to the case of a two-degree-of-freedom vehicle model performing constant-speed circular motion, the ideal center-of-mass sideslip angle is approximately equal to the steering wheel input angle, that is:

[0088] β d ≈δ(6)

[0089] Among them, β d is the ideal sideslip angle of the center of mass, and δ is the steering wheel input angle.

[0090] Step S5, determining the actual yaw rate and the actual sideslip angle of the center of mass.

[0091] For example, the actual yaw angular velocity ω of the agricultural machine is read from an angular velocity sensor pre-adapted to be installed at the center of mass position. r Although the actual center of mass sideslip angle β can also be directly measured using an angle sensor, due to cost and installation difficulty considerations, this example considers inputting the lateral acceleration, longitudinal velocity, and yaw angular velocity into the center of mass sideslip angle calculation model to approximate the center of mass sideslip angle in real time to replace the actual center of mass sideslip angle.

[0092] For example, the method for estimating the center of mass sideslip angle based on the yaw rate sensor, that is, using the center of mass sideslip angle calculation model of the following formula to estimate the actual center of mass sideslip angle β:

[0093]

[0094] Among them, V x is the longitudinal speed of the agricultural machinery, a y is the lateral acceleration of the agricultural machinery, and Δt is the preset processing period. x and a y It can be measured by a yaw rate sensor.

[0095] For this equation (7), a can be calculated from the dynamic equations of the linear two-degree-of-freedom vehicle model shown in the above equations (3) and (4): y , the specific calculation formula is:

[0096]

[0097] Based on this, the actual center of mass sideslip angle β is calculated by integral accumulation in the actual test process:

[0098]

[0099] Wherein, Δt is the preset processing period.

[0100] Step S6, calculating the difference between the ideal value and the actual value.

[0101] Specifically, it includes calculating the ideal yaw rate ω rd and the actual yaw rate ω r The first difference between r ), and calculate the ideal center of mass sideslip angle β d and the second difference between the actual center of mass sideslip angle β (denoted as Δβ).

[0102] Step S7: Based on the calculated difference, fuzzy PID control is performed to obtain a compensation yaw moment.

[0103] For example, Figure 4 : is a schematic diagram of the principle of estimating the compensating yaw moment based on the fuzzy PID control algorithm in the example of the embodiment of the present application, and the corresponding principle can be described as: calculating the ideal yaw rate, the ideal center of mass sideslip angle and the estimated value of the center of mass sideslip angle of the vehicle under the current working condition, and then calculating the difference Δω between the ideal yaw rate and the actual yaw rate r and the difference between the ideal center of mass sideslip angle and the center of mass sideslip angle Δβ; according to Δω r The vehicle yaw moment compensation torque ΔM is calculated using the fuzzy PID algorithm.

[0104] Further, Figure 5 yes Figure 4 The principle diagram of the fuzzy PID control algorithm in Figure 5 As shown in the figure, according to the variable E and its rate of change EC, the fuzzy algorithm is used to calculate the three coefficients K of the proportional (P), integral (I) and differential (D) of the PID controller. p , K I , K D Online adjustment is performed to output torque M to meet the control requirements under different steering conditions. The fuzzy set is set as:

[0105] [NB (negative big), NM (negative middle), NS (negative small), Z (zero), PS (positive small), PM (positive middle), PB (positive big)] (10)

[0106] And the input signals of the fuzzy PID control algorithm based on yaw angular velocity are Δω r (yaw rate) and Δω r / dt (rate of change of yaw angular velocity), whose domain is [-0.15, 0.15], corresponding to the three coefficients K of the PID controller P1 , K I1 , K D1 The domain of is set to [0,1000], [0,1], [1,10]. In addition, the fuzzy PID control algorithm based on the sideslip angle of the center of mass can be set similarly.

[0107] By establishing fuzzy rules and membership functions and substituting them into the control model, the value of the compensation yaw torque is calculated:

[0108]

[0109] in, represents the weight of yaw rate in the estimation of compensation yaw moment, K P1 , K I1 , K D1 K represents the proportional, integral and differential coefficients of the PID model for yaw rate. P2 , K I2 , K D2 Represents the proportional, integral and differential coefficients of the PID model corresponding to the sideslip angle of the center of mass.

[0110] In this way, the example of the embodiment of the present application directly monitors and calculates the yaw torque associated with the vehicle steering, which can ensure the calculation accuracy of the motion state of the entire vehicle, thereby ensuring that the trajectory during steering is smooth and stable.

[0111] Step S8, optimizing the differential torque distribution based on the compensation yaw moment in combination with the current steering condition.

[0112] For example, according to the two calculated differences, two working conditions can be divided into oversteer and understeer. When compensating for yaw moment, there are generally two groups of methods. For example, to compensate for oversteer, the outer wheel drive torque can be increased or the inner wheel reverse drive torque can be reduced. However, considering the reduction of energy loss and the impact on the forward driving stability of the vehicle, it is better to sample and reduce the inner wheel reverse drive torque. Based on this, in order not to affect the forward driving effect of the vehicle, the compensation torque distribution strategy in this example may include:

[0113] 1) When oversteering, the inner wheel is controlled first to reduce the output torque.

[0114] 2) When understeering occurs, the outer wheels are preferentially controlled to increase the output torque in order to control the yaw moment of the vehicle to approach the desired value.

[0115] In other examples, a ramp spinning condition is also involved. Accordingly, the above-mentioned compensation torque distribution strategy may also include:

[0116] 3) Controlling the outer wheels among the rear wheels to reduce the output torque.

[0117] That is, the example of the embodiment of the present application proposes a method for maintaining hillside self-spin based on distributed electric drive control. The basic implementation idea is: taking a wheel-track compound tractor as an example, according to the movement trend of the whole vehicle fed back by the track motor, a torque opposite to the movement direction is output to maintain the stationary state of the track, that is, the whole vehicle. At the same time, according to the size and direction of the compensating yaw torque, the torque distribution of the rear wheels is adjusted to make the whole vehicle spin in place.

[0118] For further example, Figure 6 is a flow chart of ramp spin control in an example of an embodiment of the present application. Figure 6 In this example, the wheel-crawler tractor stops on a slope and starts to spin (equivalent to entering the spin mode), for example, the vehicle is parked vertically in the uphill direction and spins counterclockwise to the right. When the vehicle is at an angle with the vertical direction, since the rear wheel driving force acts completely on the vehicle's yaw, the component of its own weight in the slope direction is only overcome by the friction between the crawler and the ground, and the vehicle shows a downward trend, and the crawler speed is greater than 0. At this time, the crawler speed is detected and a reverse compensation torque is output, that is, a compensation torque for forward driving. The component of the driving force output by the crawler in the slope direction is used to overcome its own weight, while the component in the vertical slope direction will cause the vehicle to slide sideways, that is, to slide down the slope. At this time, in this example, by reducing the output torque of the outer wheel, that is, the right rear wheel, the force of the vehicle in the vertical slope direction is kept balanced, thereby keeping the vehicle spinning in place.

[0119] Back to the above-mentioned compensating torque distribution strategy, in other examples, it also involves a driving slip condition, so the corresponding strategy may also include:

[0120] 4) controlling the inner wheel and / or the outer wheel of the rear wheels to reduce the output torque.

[0121] That is, the example of the embodiment of the present application proposes a drive anti-skid control method based on distributed electric drive control. The basic implementation idea is: taking a wheel-track compound tractor as an example, when in the above-mentioned various driving slip conditions, the rotational speed of each drive motor is detected in real time and converted into the corresponding wheel end linear speed, and the linear speed difference is compared to determine whether slippage occurs; according to the linear speed difference, combined with the compensation of yaw torque, the output torque of each drive motor is redistributed, that is, the output torque of the slipping side (the linear speed is greater than other sides) is reduced, and the excess torque is distributed to other drive motors.

[0122] For example, the wheel-track tractor is prone to obstacle crossing during operation. For example, when the wheel-track chassis performs an obstacle crossing (such as a ridge), when the track first contacts the ridge, the resistance of the track is greater than that of the rear wheel. According to the mode of evenly distributing torque, the rear wheel may slip on the spot. However, by using the steering control method of the embodiment of the present application, when it is detected that the rear wheel speed is greater than the track, the rear wheel output torque is automatically reduced and distributed to the track motor to help the track cross the ridge. When the track goes forward and passes the ridge, the rear wheel contacts the ridge. Similarly, the front track may slip. At this time, the track torque output is reduced and distributed to the rear wheel torque, so that the whole vehicle can smoothly cross the ridge.

[0123] Back to Figure 2 Through the above steps, it can be known that on the basis of distributed electric drive control, the example of the embodiment of the present application faces a variety of steering conditions, especially slope spinning conditions and driving slipping conditions. The drive motor torque distribution is adjusted based on the compensation of the yaw moment to improve traction, so that the vehicle can quickly get out of trouble and keep the steering trajectory smooth and continuous, further improving the maneuverability and flexibility of the wire-controlled chassis in hilly and mountainous areas.

[0124] In summary, the steering control method of agricultural machinery in the embodiment of the present application first reflects the dynamic characteristics of the vehicle in the longitudinal, lateral and yaw directions by establishing a dynamic model of the whole vehicle operation process, and infers the relationship between the yaw moment and the yaw angular velocity and the sideslip angle of the center of mass. Then, by calculating the difference between the ideal value of the sideslip angle of the center of mass and the ideal value of the yaw angular velocity and the actual value, the compensation yaw moment is calculated by feedback control. Finally, according to the current steering condition and the compensation yaw moment, the drive torque allocated to the left and right rear wheels is recalculated to achieve smooth and stable walking and steering. This steering control method solves the problem of slipping of agricultural machinery caused by unreasonable distribution of drive torque under conditions with very low adhesion.

[0125] Figure 7 The structural block diagram of a steering control device for agricultural machinery according to an embodiment of the present application is schematically shown. The steering control device has the same inventive concept as the above-mentioned steering control method. Figure 7As shown, the steering control device includes: an ideal parameter estimation module 100, used to estimate the ideal yaw rate and the ideal center-of-mass sideslip angle of the agricultural machinery in response to the steering condition of the agricultural machinery; an actual parameter acquisition module 200, used to acquire the actual yaw rate and the actual center-of-mass sideslip angle of the agricultural machinery; a control module 300, used to execute a feedback control algorithm to determine the compensatory yaw moment of the agricultural machinery based on a first difference between the ideal yaw rate and the actual yaw rate and a second difference between the ideal center-of-mass sideslip angle and the actual center-of-mass sideslip angle; and a compensatory torque distribution module 400, used to optimize the distribution of rear wheel torque for the agricultural machinery based on the compensatory yaw moment and adapted to the current steering condition.

[0126] The ideal estimation module 100, for example, uses the above-mentioned formula (5) and formula (6) to calculate the ideal yaw angular velocity ω of the agricultural machinery: rd And the ideal center of mass sideslip angle β of the agricultural machinery d .

[0127] The actual parameter acquisition module 200 reads the actual yaw angular velocity ω of the agricultural machinery from a pre-installed angular velocity sensor, for example. r , and the actual center of mass sideslip angle β of the agricultural machinery is calculated according to the above formula (7).

[0128] Among them, the compensating torque distribution module 400 is, for example, configured to perform any one or more of the following: under an oversteering condition, controlling the inner wheel of the rear wheels to reduce the output torque; under an understeering condition, controlling the outer wheel of the rear wheels to increase the output torque; under a ramp spinning condition, controlling the outer wheel of the rear wheels to reduce the output torque; and under a driving slip condition, controlling the inner wheel and / or the outer wheel of the rear wheels to reduce the output torque.

[0129] It should be noted that more implementation details and effects of the steering control device can be found in the aforementioned embodiments of the steering control method, which will not be repeated here.

[0130] Figure 8 The structure block diagram of a steering control device for agricultural machinery according to an embodiment of the present application is schematically shown. Figure 8 As shown, the steering control device may include: a memory configured to store instructions; and a processor configured to call the instructions from the memory and implement the steering control method of the above embodiment when executing the instructions.

[0131] In the embodiment of the present application, the steering control device can be a separately configured controller or a vehicle controller. Taking the vehicle controller and the wheel-track tractor as an example, it executes the above-mentioned steering control method and sends instructions to the track motor controller, the left rear wheel motor controller, and the left rear wheel drive motor controller, so that the corresponding motor controller executes the instructions and controls the corresponding drive motor to move, thereby driving the whole vehicle to steer.

[0132] The present application also provides an agricultural machine, which may include any of the above-mentioned steering control devices. The agricultural machine includes but is not limited to a wheel-track tractor, and may also be a harvester, a baler, a transplanter, or other types of tractors.

[0133] An embodiment of the present application also provides a machine-readable storage medium, on which instructions are stored, and the instructions are used to enable a machine to execute the above-mentioned steering control method.

[0134] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0135] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application, wherein the arrows in the flowcharts and / or block diagrams do not imply the order of execution between the related steps or modules, and those skilled in the art may adaptively adjust the order of execution based on their understanding of the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0136] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0137] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0138] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0139] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of read-only memory (ROM) or flash RAM. The memory is an example of a computer-readable medium.

[0140] Computer readable media include permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. Information can be computer readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer readable media does not include temporary computer readable media (transitory media), such as modulated data signals and carrier waves.

[0141] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0142] The above are only embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included within the scope of the claims of the present application.

Claims

1. A steering control method for agricultural machinery, characterized in that: include: estimating an ideal yaw rate and an ideal sideslip angle of the agricultural machine; Obtaining an actual yaw angular velocity and an actual center-of-mass sideslip angle of the agricultural machinery; executing a feedback control algorithm to determine a compensating yaw moment of the agricultural machine based on a first difference between the ideal yaw rate and the actual yaw rate and a second difference between the ideal center of mass sideslip angle and the actual center of mass sideslip angle; as well as Based on the compensating yaw moment, the rear wheel torque of the agricultural machinery is optimally distributed in accordance with the current steering condition.

2. The steering control method according to claim 1, characterized in that: Before the estimating, the steering control method further includes: Based on the current steering wheel input angle, an initial distribution of rear wheel torque for the agricultural machine is performed.

3. The steering control method according to claim 1, characterized in that: The estimating the ideal yaw rate and the ideal sideslip angle of the agricultural machinery comprises: The ideal yaw angular velocity ω of the agricultural machinery is calculated using the following formula: rd : Where, L is the wheelbase of the vehicle, V x is the longitudinal speed of the agricultural machinery, K is the stability coefficient; and The ideal center of mass sideslip angle β of the agricultural machinery is estimated by the following formula: d : b d ≈d Among them, δ is the real-time steering wheel input angle.

4. The steering control method according to claim 1, characterized in that: The obtaining of the actual yaw angular velocity and the actual center of mass sideslip angle of the agricultural machinery comprises: The actual yaw angular velocity ω of the agricultural machine is read from the pre-installed angular velocity sensor r ;as well as The actual center of mass sideslip angle β of the agricultural machinery is calculated according to the following formula: Among them, V x is the longitudinal speed of the agricultural machinery, a y is the lateral acceleration of the agricultural machinery, and Δt is the preset processing period.

5. The steering control method according to claim 1, characterized in that: The feedback control algorithm is a fuzzy PID algorithm.

6. The steering control method according to claim 1, characterized in that: The optimization distribution of the rear wheel torque of the agricultural machinery adapted to the current steering condition includes any one or more of the following: Under an oversteering condition, controlling the inner wheel among the rear wheels to reduce output torque; Under an understeering condition, controlling the outer wheels among the rear wheels to increase the output torque; In a hill-spinning condition, controlling the outer wheels among the rear wheels to reduce output torque; and Under a driving slip condition, both the inner wheel and the outer wheel of the rear wheels are controlled to reduce output torque.

7. A steering control device for agricultural machinery, characterized in that: include: an ideal parameter estimation module, used for estimating an ideal yaw rate and an ideal sideslip angle of the agricultural machinery in response to a steering condition of the agricultural machinery; An actual parameter acquisition module, used to acquire an actual yaw angular velocity and an actual sideslip angle of the center of mass of the agricultural machinery; a control module for executing a feedback control algorithm to determine a compensatory yaw moment of the agricultural machine based on a first difference between the ideal yaw rate and the actual yaw rate and a second difference between the ideal center of mass sideslip angle and the actual center of mass sideslip angle; as well as The compensation torque distribution module is used to optimize the distribution of the rear wheel torque of the agricultural machinery based on the compensation yaw moment and adapt to the current steering condition.

8. The steering control device according to claim 7, characterized in that: The ideal parameter estimation module is configured as follows: The ideal yaw angular velocity ω of the agricultural machinery is calculated using the following formula: rd : Where, L is the wheelbase of the vehicle, V x is the longitudinal speed of the agricultural machinery, K is the stability coefficient; as well as The ideal center of mass sideslip angle β of the agricultural machinery is estimated by the following formula: d : b d ≈d Among them, δ is the real-time steering wheel input angle.

9. The steering control device according to claim 7, characterized in that: The actual parameter acquisition module is configured as follows: The actual yaw angular velocity ω of the agricultural machine is read from the pre-installed angular velocity sensor r ;as well as The actual center of mass sideslip angle β of the agricultural machinery is calculated according to the following formula: Among them, V x is the longitudinal speed of the agricultural machinery, a y is the lateral acceleration of the agricultural machinery, and Δt is the preset processing period.

10. The steering control device according to claim 7, characterized in that: The compensation torque distribution module is configured to perform any one or more of the following: Under an oversteering condition, controlling the inner wheel of the rear wheels to reduce the output torque; Under an understeering condition, controlling the outer wheels among the rear wheels to increase the output torque; In a hill-spinning condition, controlling the outer wheels among the rear wheels to reduce output torque; and Under a driving slip condition, the inner wheel and / or the outer wheel among the rear wheels are controlled to reduce the output torque.

11. A steering control device for agricultural machinery, characterized in that: include: a memory configured to store instructions; as well as A processor is configured to call the instructions from the memory and implement the steering control method according to any one of claims 1 to 6 when executing the instructions.

12. An agricultural machine, characterized in that: A steering control device comprising any one of claims 7 to 11.

13. A machine-readable storage medium, characterized in that: The machine-readable storage medium stores instructions, which are used to enable a machine to execute the steering control method according to any one of claims 1 to 6.

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