A forklift AGV path tracking control method and device, and a storage medium

Abstract

This invention discloses a path tracking control method, device, and storage medium for forklift AGVs. The method includes: determining the transformation relationship between the driving speed of the left drive wheel, the driving speed of the right drive wheel, and the turning angle of the steering wheel through a drive mechanism; establishing a follower coordinate system on the tracking path; establishing the kinematic equations of the forklift AGV in the follower coordinate system; transforming the path tracking problem into finding a bounded control input problem, and calculating the control quantity formula for the target angular velocity based on the kinematic equations; setting a target linear velocity, and using the set target linear velocity, the transformation relationship, and the control quantity formula for the target angular velocity, calculating the corresponding driving speed of the left drive wheel, the driving speed of the right drive wheel, and the target turning angle of the steering wheel according to the driving mode corresponding to the steering wheel. This invention provides a simple, reliable, versatile, and easy-to-debug path tracking control method for forklift AGVs with two drive wheels and one steering wheel.

Description

Technical Field

[0001] This invention relates to the field of AGV control technology, and in particular to a path tracking control method, device, and storage medium for forklift AGVs. Background Technology

[0002] In industrial AGVs, forklift AGVs have become a widely used type of unmanned material handling equipment. Most forklift AGVs currently on the market are single-steering-wheel structures, consisting of a drive unit that functions as both driver and steer, and several unpowered fixed or swivel wheels that only provide support or balance. Due to their small wheel diameter and the prevalence of polyurethane-coated wheels, these forklift AGVs are primarily used for indoor material handling.

[0003] The drive unit consists of two independently driven directional wheels and a steering wheel with only steering function; its wheels are rubber tires. Forklift AGVs using this drive unit are mainly used for outdoor material handling. Currently, there is limited research on path tracking control for this type of forklift AGV, and the tracking control methods used for traditional single-steering-wheel forklift AGVs are not suitable for this type of forklift AGV. Summary of the Invention

[0004] The purpose of this invention is to provide a path tracking control method, device, and storage medium for forklift AGVs, in order to solve one or more technical problems existing in the prior art, or at least provide a beneficial option or create conditions.

[0005] The solution to the technical problem of this invention is to provide a path tracking control method and device for forklift AGVs, as well as a storage medium.

[0006] According to a first aspect of the present invention, a path tracking control method for a forklift AGV is provided, comprising the following steps:

[0007] The driving mechanism, consisting of the left drive wheel, the right drive wheel, and the steering wheel, determines the conversion relationship between the driving speed of the left drive wheel, the driving speed of the right drive wheel, and the steering angle of the steering wheel.

[0008] Obtain the tracking path of the forklift AGV, establish a global coordinate system, and establish a follow-up coordinate system on the tracking path based on the posture of the forklift AGV in the global coordinate system.

[0009] Based on the servo coordinate system, the distance deviation and angular deviation between the current forklift AGV and the tracking path are obtained, and the target linear velocity and target angular velocity of the forklift AGV are used as input control quantities to establish the kinematic equations of the forklift AGV in the servo coordinate system.

[0010] By transforming the path tracking problem of the forklift AGV into a problem of finding a bounded control input, the control formula for the target angular velocity is calculated based on the kinematic equations.

[0011] The target linear velocity is set, and using the control formula of the target linear velocity, the conversion relationship and the target angular velocity, the driving speed of the left drive wheel, the driving speed of the right drive wheel and the target steering angle of the steering wheel are calculated according to the driving mode of the steering wheel.

[0012] Furthermore, the process of determining the transformation relationship specifically includes:

[0013] The drive mechanism consists of a steering wheel mounted on the central axis of the forklift AGV, with the midpoint of the straight-line distance between the left and right drive wheels coinciding with the central axis.

[0014] Based on the aforementioned drive mechanism and rigid body motion constraints, the driving speed v of the left drive wheel is obtained. L The driving speed v of the right drive wheel R The conversion relationship between the steering wheel angle φ and the steering wheel angle:

[0015]

[0016] Where L is the distance from the steering wheel to the midpoint of the straight line distance, and D is the wheel distance from the center of the left drive wheel to the center of the right drive wheel.

[0017] Furthermore, the follower coordinate system established on the tracking path specifically includes:

[0018] Establish a global coordinate system XOY, and select the midpoint of the straight-line distance as the AGV reference point;

[0019] Obtain the tracking path C of the forklift AGV, and set the orthogonal projection point of the AGV reference point on the tracking path C as the origin.

[0020] According to the origin Establish a moving coordinate system Where the i-axis is parallel to the origin The tangents on the tracking path C coincide and have the same direction. The j-axis is obtained by rotating the i-axis counterclockwise by 90°.

[0021] Furthermore, the process of establishing the kinematic equations of the forklift AGV in the follower coordinate system specifically includes:

[0022] Obtain the distance deviation d between the current forklift AGV and the tracking path C. e and angular deviation θ e ;

[0023] According to the distance deviation d e and angular deviation θ e The target linear velocity v and target angular velocity ω of the forklift AGV are used as input control variables, and a follower coordinate system is established. Lower kinematic equations:

[0024]

[0025] Where s is the distance traveled by the forklift AGV along the tracking path C, and k is the moving coordinate system. The origin The curvature at that point.

[0026] Furthermore, the path tracking problem of the forklift AGV is transformed into finding a bounded control input [v,ω]. T question;

[0027] Introduce new control variables [u1, u2] T Replace [v,ω] T Introduce new state variables [z1, z2, z3] T Replace [s,d] e ,θ e ] T ,make

[0028]

[0029] The kinematic equations are then transformed into a three-dimensional chain system:

[0030]

[0031] Taking z2 and z3 to form a second-order subsystem, setting proportional feedback, and converging the second-order subsystem according to the proportional feedback:

[0032] Based on the aforementioned proportional feedback, kinematic equations, three-dimensional chain system, and z3=(1-d e k)tanθ e The formula for controlling the target angular velocity is obtained as follows:

[0033]

[0034] Furthermore, the calculation process for the corresponding driving speed of the left drive wheel, the driving speed of the right drive wheel, and the steering wheel angle specifically includes:

[0035] When the corresponding driving method is motor drive, the target angular velocity is calculated according to the control formulas for the target linear velocity and the target angular velocity.

[0036] Based on the target angular velocity ω, wheel track D, and the set target linear velocity v, the first velocity is calculated using the following formula:

[0037]

[0038] , obtain the driving speed v of the left drive wheel L and the drive speed v of the right drive wheel R ;

[0039] Based on the driving speed v of the left drive wheel L and the drive speed v of the right drive wheel R Using the aforementioned transformation relationship, the target steering angle φ of the steering wheel is calculated.

[0040] Furthermore, the calculation process for the corresponding driving speed of the left drive wheel, the driving speed of the right drive wheel, and the steering wheel angle specifically includes:

[0041] When the corresponding driving method is hydraulic drive, the target angular velocity is calculated according to the control formulas for the target linear velocity and the target angular velocity.

[0042] Based on the target angular velocity ω, distance L, and set target linear velocity v, the target rotation angle is calculated using the following formula:

[0043]

[0044] The target steering angle φ of the steering wheel is calculated.

[0045] Real-time acquisition of the steering wheel's rotation angle φ s According to the aforementioned angle φ s The wheelbase D, distance L, and the set target linear velocity v are used to calculate the second velocity using the formula:

[0046]

[0047] , obtain the driving speed v of the left drive wheel L and the drive speed v of the right drive wheel R .

[0048] According to a second aspect of the present invention, an electronic device is provided, comprising:

[0049] A memory for storing a program; a processor for executing the program stored in the memory, wherein when the processor executes the program stored in the memory, the processor is configured to execute a path tracking control method for a forklift AGV as described in any one of the first aspects.

[0050] According to a third aspect of the present invention, a storage medium is provided, comprising: storing computer-executable instructions for performing a path tracking control method for a forklift AGV as described in any one of the first aspects.

[0051] The beneficial effects of this invention are as follows: This invention provides a simple, reliable, versatile, and easy-to-debug path tracking control method for forklift AGVs with a drive mechanism consisting of two drive wheels and one steering wheel. Establishing a follower coordinate system facilitates a more intuitive description of the forklift AGV's position relative to the tracking path, and compared to a Cartesian coordinate system, it can naturally and directly track curves. Based on the driving method of the steering wheel, the driving speeds of the left and right drive wheels and the steering wheel angle are calculated specifically to achieve coordinated movement of the forklift AGV, better reflecting actual AGV working scenarios and expanding the application range of the path tracking control method. Attached Figure Description

[0052] Figure 1 This is a schematic flowchart of a path tracking control method for a forklift AGV provided by the present invention;

[0053] Figure 2 This is a schematic diagram of the control quantity relationship of the drive mechanism in a path tracking control method for a forklift AGV provided by the present invention;

[0054] Figure 3 This is a schematic diagram of the servo coordinate system construction for a path tracking control method for a forklift AGV provided by the present invention. Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and should not be construed as limiting the scope of the invention.

[0056] It should be noted that although functional modules are divided in the system diagram, in some cases, the steps shown or described may be executed in a different order than the module division or flowchart shown in the system. The terms "first," "second," etc., in the specification, claims, and the aforementioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0057] In the description of this invention, it should be noted that, unless otherwise explicitly defined, terms such as "setting," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0058] According to an embodiment of the first aspect of the present invention, referring to Figure 1 In some embodiments of the present invention, a path tracking control method for a forklift AGV includes the following steps:

[0059] S100, through a drive mechanism consisting of a left drive wheel, a right drive wheel, and a steering wheel, determines the conversion relationship between the driving speed of the left drive wheel, the driving speed of the right drive wheel, and the steering angle of the steering wheel.

[0060] In this embodiment, the steering wheel is a wheel with steering function, located at the front end of the forklift AGV and on the central axis of the forklift AGV body. The left drive wheel and the right drive wheel are fixedly located at the rear end of the forklift AGV, and both the left drive wheel and the right drive wheel are independently driven wheels.

[0061] The forklift AGV, driven by the aforementioned three wheels, has three control variables: the driving speed of the left drive wheel, the driving speed of the right drive wheel, and the steering angle of the steering wheel. These three control variables must satisfy the planar rigid body motion constraints; otherwise, phenomena such as dragging and pushing will occur between the wheels of the forklift AGV, indicating a lack of coordination in their movements.

[0062] Based on the constructed drive mechanism, determine the relationship between the control quantities corresponding to the three wheels.

[0063] S200: Obtain the tracking path of the forklift AGV, establish a global coordinate system, and establish a follow-up coordinate system on the tracking path based on the posture of the forklift AGV in the global coordinate system.

[0064] In this embodiment, the path that the forklift AGV is currently tracking is obtained, and a global coordinate system is established. Under the global coordinate system, a follow-up coordinate system on the path that the forklift AGV needs to track is established based on the current posture of the forklift AGV.

[0065] Establishing a moving coordinate system makes it easier to describe the position of the forklift AGV relative to the tracking path more intuitively. Compared with the Cartesian coordinate system, it can naturally and directly track curves.

[0066] S300: Based on the servo coordinate system, obtain the distance deviation and angular deviation between the current forklift AGV and the tracking path, and use the target linear velocity and target angular velocity of the forklift AGV as input control variables to establish the kinematic equations of the forklift AGV in the servo coordinate system.

[0067] In this embodiment, the current distance deviation and current angle deviation between the forklift AGV and the tracking path are detected in real time through the follow-up coordinate system established in S200 and the navigation and positioning module.

[0068] Based on the current distance deviation and current angle deviation, and using the target linear velocity and target angular velocity of the forklift AGV as control inputs, the kinematic equations of the forklift AGV are obtained in the servo coordinate system.

[0069] S400 transforms the path tracking problem of forklift AGVs into a problem of finding bounded control inputs, and calculates the control formula for the target angular velocity based on kinematic equations.

[0070] In this embodiment, the method for solving the kinematic equations is as follows: the path tracking problem of the forklift AGV is equivalent to finding a bounded control input. This ensures that the output converges to zero within a finite time, achieving efficient and precise path tracking control of the forklift AGV. By solving the kinematic equations, the control formula for the target angular velocity is obtained.

[0071] S500 sets the target linear velocity. Using the set target linear velocity, the conversion relationship, and the control formula for the target angular velocity, it calculates the corresponding drive speed of the left drive wheel, the drive speed of the right drive wheel, and the target steering angle of the steering wheel according to the drive mode corresponding to the steering wheel.

[0072] In this embodiment, the target linear velocity is set based on the path conditions of the tracking path or based on the forklift AGV itself.

[0073] Since the drive wheels of forklift AGVs are usually directly driven by servo motors, resulting in a fast response speed, the steering wheels can be directly driven by a motor or by a hydraulic cylinder. In other words, the steering wheels can be driven by either a motor or a hydraulic cylinder.

[0074] Motor-driven steering wheels have a sufficiently high angular velocity, and their response time is basically synchronized with that of the drive wheels, with no obvious lag. However, hydraulically driven steering wheels have a lower angular velocity than motor-driven steering wheels, and their response time is significantly slower than that of the drive wheels, exhibiting noticeable lag. They are mainly used in heavy-duty forklift AGVs.

[0075] Therefore, for the two driving methods mentioned above, the present invention designs corresponding control strategies based on the corresponding driving methods, and calculates the corresponding control quantities.

[0076] By using the pre-defined target linear velocity, the conversion relationship determined in S100, and the control formula for the target angular velocity obtained in S400, the driving speed of the corresponding left drive wheel, the steering wheel angle, and the driving speed of the right drive wheel are calculated according to the driving mode of the drive wheel.

[0077] This invention establishes a following coordinate system, which facilitates a more intuitive description of the forklift AGV's position relative to the tracking path. Compared to the Cartesian coordinate system, it can naturally and directly track curves. Based on the driving method of the steering wheels, the rotation angle of the steering wheels, the driving speed of the right drive wheel, and the driving speed of the left drive wheel are calculated specifically to achieve coordinated movement of the forklift AGV. This better fits the actual working scenario of the AGV, expanding the application range of the path tracking control method. Furthermore, this invention provides a simple, reliable, versatile, and easy-to-debug path tracking control method for forklift AGVs with a drive mechanism having two drive wheels and one steering wheel.

[0078] Reference Figure 2 In some embodiments of the present invention, S100 specifically includes the following steps:

[0079] S110, the midpoint of the straight-line distance between the central axis and the left drive wheel and the right drive wheel coincides, and the steering wheel is set on the central axis of the vehicle body. The drive mechanism is formed by the above positional relationship.

[0080] In this embodiment, reference is made to Figure 2 The steering wheels are wheels with steering function, located at the front end of the forklift AGV and on the central axis of the forklift AGV body. The left and right drive wheels are fixedly located at the rear end of the forklift AGV, and both the left and right drive wheels are independently driven.

[0081] The forklift AGV, driven by the aforementioned three wheels, has three control variables: the driving speed of the left drive wheel, the driving speed of the right drive wheel, and the steering angle of the steering wheel. These three control variables must satisfy the planar rigid body motion constraints; otherwise, phenomena such as dragging and pushing will occur between the wheels of the forklift AGV, indicating a lack of coordination in their movements.

[0082] S120, based on the drive mechanism constructed in S110, using rigid body motion constraints, obtain the driving speed v of the left drive wheel. L The steering wheel angle φ and the driving speed v of the right drive wheel. R The transformation relationship between them:

[0083]

[0084] In this embodiment, reference is made to Figure 2 Let point p be the midpoint of the straight-line distance between the left and right drive wheels, and let v be the velocity at point p. Let ICR be the instantaneous rotation center of the forklift AGV, and let r be the instantaneous rotation radius of the steering wheels. f The speed of the steering wheel is v f .

[0085] According to the constraints of planar rigid body motion, the velocity components along the central axis of the vehicle should be equal.

[0086]

[0087] The angular velocities of the forklift AGV around its instantaneous rotation center ICR are equal:

[0088]

[0089] Where D is the wheelbase between the center of the left drive wheel and the center of the right drive wheel, obtained from trigonometric relationships:

[0090]

[0091] Where L is the distance from the steering wheel to point p, combining the above three formulas, we can obtain:

[0092]

[0093] Thus, v was determined. L v R The conversion relationship between φ and φ.

[0094] Reference Figure 3 In some embodiments of the present invention, S200 specifically includes the following steps:

[0095] S210, establish a global coordinate system XOY, with the AGV reference point being the midpoint of the straight-line distance between the left and right drive wheels.

[0096] In this embodiment, reference is made to Figure 3 XOY is the global coordinate system. The midpoint p of the straight-line distance between the left drive wheel and the right drive wheel is set as the reference point for the forklift AGV path tracking control. That is, point p is set as the AGV reference point.

[0097] S220, obtain the current tracking path of the forklift AGV, and set the orthogonal projection point of the AGV reference point on the tracking path C as the origin.

[0098] In this embodiment, reference is made to Figure 3 Curve C represents the path that the AGV is tracking. The orthogonal projection point of the AGV reference point p onto the tracking path C is obtained, and this orthogonal projection point is set as... Point, then The point is the origin of the moving coordinate system.

[0099] S230, based on the origin Set the i-axis by the tangent on the tracking path, and obtain the j-axis by rotating counterclockwise based on the i-axis.

[0100] In this embodiment, reference is made to Figure 3 Using the origin obtained in S320 Draw a tangent line on the tracking path C. The i-axis of the servo coordinate system coincides with the tangent line, and the i-axis and the tangent line are in the same direction. Rotate the i-axis counterclockwise by 90° to obtain the j-axis. Thus, a servo coordinate system is established on the tracking path C.

[0101] Compared with the Cartesian coordinate system used in existing technologies, the servo coordinate system can more conveniently and intuitively describe the position of the forklift AGV relative to the curved path.

[0102] Reference Figure 3 In some embodiments of the present invention, S300 specifically includes the following steps:

[0103] S310, Obtain the distance deviation d between the current forklift AGV and the tracking path C. e and angular deviation θ e .

[0104] In this embodiment, the AGV reference point p and the origin on the tracking path C are obtained in real time through the navigation and positioning module using the follower coordinate system established in S200. The distance between them is the distance deviation d between the current forklift AGV and the tracking path C. e .

[0105] The navigation and positioning module detects in real time the relationship between the AGV reference point p and the origin on the tracking path C. The distance between them is the distance deviation d between the current forklift AGV and the tracking path C. e In other words, the AGV reference point p is moved to... The distance between the points is taken as the distance deviation d between the current forklift AGV and the tracking path C. e Distance deviation d e The value is equal to the value of point p in the moving coordinate system. The vertical axis below.

[0106] The navigation and positioning module monitors in real time to obtain the orientation angle θ of the forklift AGV in the global coordinate system, and obtains the orientation angle θ of the i-axis of the following coordinate system based on the tracking path C. s .

[0107] Using the i-axis as the reference, define the direction angle θ of the forklift AGV and the direction angle θ of the i-axis of the follower coordinate system. s The difference is the angular deviation θ between the current forklift AGV and the tracking path C. e In other words, θ e =θ-θ sIn this system, the sign is positive when rotated counterclockwise and negative when rotated clockwise.

[0108] S320, the target linear velocity v and target angular velocity ω of the forklift AGV are used as input control quantities, based on the distance deviation d obtained in S310. e and angular deviation θ e Established in a moving coordinate system The following are the kinematic equations:

[0109]

[0110] Where the travel distance of the forklift AGV on the tracking path C is s, and k is the following coordinate system. The origin The curvature at that point.

[0111] In this embodiment, the angle deviation θ obtained through S310 e and distance deviation d e , refer to Figure 3 The following coordinate system The instantaneous velocity of the tracking path C is set to v. s That is, set the origin. Instantaneous velocity is v s .

[0112] In the global coordinate system XOY, let the orientation angle of the forklift AGV in the global coordinate system be... If the target linear velocity v and target angular velocity ω of the forklift AGV are known, then the formula for calculating the first velocity is:

[0113]

[0114] Let C O To track path C at the origin The instantaneous rotation center, k is the origin. The curvature at a given point is determined by the direction of movement of the forklift AGV; counterclockwise is positive, and clockwise is negative. s Origin Given the radius of curvature, we have:

[0115]

[0116] The motion of the forklift AGV can be decomposed into motion around the instantaneous center of rotation C. O Rotation, translation along the j-axis, and rotation around the following coordinate system Rotation. The forklift AGV rotates around its instantaneous rotation center C. O Should be related to the following coordinate system The angular velocities of rotation are equal:

[0117]

[0118] Therefore:

[0119]

[0120] The forklift AGV translates along the j-axis and satisfies the following kinematic relationship:

[0121]

[0122] , by θ e =θ-θ s get:

[0123]

[0124] Let the distance traveled by the forklift AGV along the tracking path C be s, then we have:

[0125]

[0126] The forklift AGV in the following coordinate system is obtained through the above equations. The kinematic equations are as follows:

[0127]

[0128] In some embodiments of the present invention, S400 specifically includes the following steps:

[0129] S410, the forklift path tracking problem is equivalent to finding the bounded control input [v,ω] T question.

[0130] In this embodiment, the path tracking problem of the forklift AGV is equivalent to finding the bounded control input [v, ω]. T , so that [d e ,θ e ] T It converges to zero.

[0131] S420, using [u1, u2] T Replace [v,ω] T And using [z1,z2,z3] T Replace [s,d] e ,θ e ] T ,make

[0132]

[0133] Transforming the kinematic equations into a three-dimensional chain system:

[0134]

[0135] In this embodiment, new control variables [u1,u2] are introduced. T And the new state variables [z1, z2, z3] T Use [u1, u2] T Replace [v,ω] T Use [z1, z2, z3] T Replace [s,d] e ,θ e ] T And make:

[0136]

[0137] This transforms the kinematic equations into a three-dimensional chain system:

[0138]

[0139] S430, take z2 and z3 from the three-dimensional chain equation to construct a second-order subsystem, set proportional feedback, and make the second-order subsystem converge to the origin through the set proportional feedback.

[0140] In this embodiment, based on the three-dimensional chain system in S420, z2 and z3 are selected to form a second-order subsystem:

[0141]

[0142] The second-order subsystem is a single-input linear time-varying system. Based on linear system theory, a feedback proportional control is designed:

[0143] u2=-u2k1z2-|u1|k2z3

[0144] This causes the second-order subsystem to converge to the origin, where parameters k1 and k2 are both positive numbers greater than 0.

[0145] It should be noted that, according to the pole placement theory of linear systems, k1 can be taken as λ. 2 And k2 = 2λ, where λ > 0, thus reducing the two control parameters k1 and k2 to one control parameter λ.

[0146] S440, based on S320, yields the kinematic equations; S430 sets the proportional feedback; S420 yields the three-dimensional chain system and z3=(1-d e k)tanθ e The formula for controlling the target angular velocity is obtained as follows:

[0147]

[0148] In this embodiment, for z3=(1-de k)tanθ e Differentiate both sides of the equation, and simultaneously use the three-dimensional chain system... and kinematic equations We can obtain:

[0149]

[0150] This is the formula for the control quantity of the target angular velocity ω, where, To track the rate of change of curvature of path C, which is a known quantity, u2 is obtained from the proportional feedback set by S430, and the kinematic equations are obtained from S320.

[0151] Since the drive wheels of forklift AGVs are usually directly driven by servo motors, resulting in a fast response speed, the steering wheels can be directly driven by a motor or by a hydraulic cylinder. In other words, the steering wheels can be driven by either a motor or a hydraulic cylinder.

[0152] In some embodiments of the present invention, S500 specifically includes the following steps:

[0153] S510, when the driving mode is motor drive, calculates the target angular velocity according to the set control formulas for the target linear velocity and target angular velocity.

[0154] In this embodiment, the speed v of the AGV reference point p is taken as the target linear speed. When the steering wheel is directly driven by the motor, the corresponding driving method can be considered as motor drive.

[0155] Based on the set target linear velocity v, the target angular velocity ω is obtained by calculating using the control formula for the target angular velocity.

[0156] S511, based on the wheelbase D, the set target linear velocity v, and the target angular velocity ω obtained in S510, the first velocity calculation formula is used for calculation:

[0157]

[0158] The driving speeds v corresponding to the two drive wheels are obtained. R v L .

[0159] In this embodiment, the wheelbase D, the target angular velocity ω obtained in S510, and the set target linear velocity v are substituted into the first velocity calculation formula to calculate the driving speed v corresponding to the two drive wheels. R v L .

[0160] S512, based on the two driving speeds v obtained in S511R v L The target steering angle φ of the steering wheel is obtained by using the transformation relationship in S100.

[0161] In this embodiment, based on the two driving speeds v obtained in S511 R v L And the transformation relationships in S100:

[0162]

[0163] The target steering angle φ of the steering wheel is obtained through calculation.

[0164] It should be noted that the obtained drive speed v of the left drive wheel L The driving speed v of the right drive wheel R The target steering angle φ of the steering wheel is input to the corresponding actuator, thus forming a closed loop to achieve path tracking control.

[0165] In some embodiments of the present invention, S500 specifically includes the following steps:

[0166] S520, when the driving method is hydraulic drive, calculates the target angular velocity according to the set control formulas for the target linear velocity and target angular velocity.

[0167] In this embodiment, the speed v of the AGV reference point p is taken as the target linear speed. When the steering wheel is driven by a hydraulic cylinder, the corresponding driving method can be considered as hydraulic drive.

[0168] Based on the set target linear velocity, the target angular velocity ω is obtained by calculating using the control formula for the target angular velocity.

[0169] S521, based on the set target linear velocity v, distance L, and target angular velocity ω obtained in S520, the target rotation angle is calculated using the following formula:

[0170]

[0171] The target steering angle φ of the steering wheel is obtained.

[0172] In this embodiment, in the global coordinate system XOY, the angular velocity of the AGV and the rotation angle of the steering wheels have the following kinematic relationship:

[0173]

[0174] Based on the above kinematic relationships, the formula for calculating the target steering angle of the steering wheel is derived as follows:

[0175]

[0176] The target angular velocity ω, the set target linear velocity v, and the distance L obtained in S520 are input into the target rotation angle calculation formula to obtain the target rotation angle φ of the steering wheel.

[0177] S522, based on distance L, wheel track D, the set target linear velocity v, and the detected real-time turning angle φ s The second velocity is calculated using the formula for calculating the second velocity:

[0178]

[0179] This gives the driving speeds corresponding to the two drive wheels.

[0180] In this embodiment, the steering angle φ of the steering wheel is detected in real time as the steering wheel rotates toward the target steering angle φ. s Based on the distance L, wheel track D, the set target linear velocity v, and the real-time detected turning angle φ s The second velocity is calculated using the following formula:

[0181]

[0182] Real-time calculations are performed to obtain the driving speeds v corresponding to the two drive wheels. R v L .

[0183] It should be noted that the obtained drive speed v of the left drive wheel L The driving speed v of the right drive wheel R The target steering angle φ of the steering wheel is input to the corresponding actuator, thus forming a closed loop to achieve path tracking control.

[0184] Because the steering wheel response is slow, the target position cannot be reached quickly after the target steering angle φ is issued. Therefore, the passive control quantity v is not calculated based on the target steering angle φ. R v L Instead, it is based on the real-time rotation angle φ. s Calculations are performed to enable the faster-responding drive wheels to follow the slower-responding steering wheels, thereby achieving coordinated movement of the forklift AGV.

[0185] Motor-driven steering wheels have a sufficiently high angular velocity, and their response time is basically synchronized with that of the drive wheels, with no obvious lag. However, hydraulically driven steering wheels have a lower angular velocity than motor-driven steering wheels, and their response time is significantly slower than that of the drive wheels, exhibiting noticeable lag. They are mainly used in heavy-duty forklift AGVs.

[0186] Therefore, for the two driving methods mentioned above, the present invention designs corresponding control strategies based on the corresponding driving methods, and calculates the corresponding control quantities.

[0187] The control method of the first aspect of the present invention can also be extended to forklift AGVs with two independent steering wheels, whose steering wheels are directly driven by a motor; and extended to forklift AGVs with a trapezoidal Ackermann steering structure, whose steering wheels are hydraulically driven.

[0188] For the two types of forklift AGVs mentioned above, a virtual steering wheel can be introduced first. This virtual steering wheel is located on the line connecting the vehicle's central axis and the two front wheels. Using the control method for a single-steering-wheel forklift as described in the first aspect of this invention, the target control angle of the virtual steering wheel is obtained. Then, they are distributed to the two steering wheels according to the corresponding geometric relationship.

[0189] According to an embodiment of a second aspect of the present invention, an electronic device includes: a memory for storing a program; and a processor for executing the program stored in the memory, wherein when the processor executes the program stored in the memory, the processor is configured to execute a path tracking control method for a forklift AGV according to the first aspect.

[0190] The processor and memory can be connected via a bus or other means.

[0191] Memory, as a non-transitory computer-readable storage medium, can be used to store non-transitory software programs and non-transitory computer-executable programs, such as the AGV dual-radar installation error calibration method described in the embodiments of the present invention. The processor implements the path tracking control method for the forklift AGV according to the first aspect of the present invention by running the non-transitory software program and instructions stored in the memory.

[0192] The memory may include a program storage area and a parameter storage area. The program storage area may store the operating system and application programs required for at least one function. The parameter storage area may store the above-described method for calibrating the installation error of the AGV dual radar. Furthermore, the memory may include high-speed random access memory and non-transitory memory, such as at least one disk storage device, flash memory device, or other non-transitory solid-state storage device. In some embodiments, the memory may optionally include memory remotely located relative to the processor, which can be connected to the processor via a network. Examples of such networks include, but are not limited to, the Internet, intranets, local area networks, mobile communication networks, and combinations thereof.

[0193] The non-transient software program and instructions required to implement the above-described terminal selection method are stored in memory. When executed by one or more processors, they are used to implement the path tracking control method of the forklift AGV of the first aspect of the present invention.

[0194] According to an embodiment of a third aspect of the present invention, the present invention also provides a storage medium storing computer-executable instructions for executing a path tracking control method for a forklift AGV according to the first aspect.

[0195] It will be understood by those skilled in the art that all or some of the steps and systems in the methods disclosed above can be implemented as software, firmware, hardware, and suitable combinations thereof. Some or all of the physical components can be implemented as software executed by a processor, such as a central processing unit, digital signal processor, or microprocessor, or as hardware, or as an integrated circuit, such as an application-specific integrated circuit. Such software can be distributed on a computer-readable medium, which can include computer storage media (or non-transitory media) and communication media (or transient media). As is known to those skilled in the art, the term computer storage media includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, parameter structures, program modules, or other parameters). Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technologies, CD-ROM, digital versatile disc (DVD) or other optical disc storage, magnetic cartridges, magnetic tape, disk storage or other magnetic storage devices, or any other medium that can be used to store desired information and is accessible to a computer. Furthermore, as is known to those skilled in the art, communication media typically include computer-readable instructions, parameter structures, program modules, or other parameters in modulation parameter signals such as carrier waves or other transmission mechanisms, and may include any information delivery medium.

[0196] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention, and these equivalent modifications or substitutions are all included within the scope defined by the claims of this application.

Claims

1. A path tracking control method for a forklift AGV, characterized in that, include: The driving mechanism, consisting of the left drive wheel, the right drive wheel, and the steering wheel, determines the conversion relationship between the driving speed of the left drive wheel, the driving speed of the right drive wheel, and the steering angle of the steering wheel. Obtain the tracking path of the forklift AGV, establish a global coordinate system, and establish a follow-up coordinate system on the tracking path based on the posture of the forklift AGV in the global coordinate system. Based on the servo coordinate system, the distance deviation and angular deviation between the current forklift AGV and the tracking path are obtained, and the target linear velocity and target angular velocity of the forklift AGV are used as input control quantities to establish the kinematic equations of the forklift AGV in the servo coordinate system. By transforming the path tracking problem of the forklift AGV into a problem of finding a bounded control input, the control formula for the target angular velocity is calculated based on the kinematic equations. The target linear velocity is set, and using the control formula of the target linear velocity, the conversion relationship and the target angular velocity, the driving speed of the left drive wheel, the driving speed of the right drive wheel and the target turning angle of the steering wheel are calculated according to the driving mode of the steering wheel. The process of establishing the kinematic equations of the forklift AGV in the follower coordinate system specifically includes: Get the current forklift AGV and its tracking path Distance deviation between and angle deviation ; According to the distance deviation and angle deviation The target linear velocity of the forklift AGV and target angular velocity The input control quantity is established in the servo coordinate system. Lower kinematic equations: in, For forklift AGVs to track paths The driving distance on the road For a moving coordinate system The origin Curvature at that point; The process of obtaining the control formula for the target angular velocity specifically includes: The path tracking problem of forklift AGVs is transformed into finding bounded control inputs. question; Introducing new control variables replace Introducing new state variables replace ,make The kinematic equations are then transformed into a three-dimensional chain system: ； Pick , A second-order subsystem is constructed, and proportional feedback is set. The second-order subsystem is then converged based on the proportional feedback. Based on the aforementioned proportional feedback, kinematic equations, three-dimensional chain system, and The formula for controlling the target angular velocity is obtained as follows: 。 2. The path tracking control method for a forklift AGV according to claim 1, characterized in that, The process of determining the transformation relationship specifically includes: The drive mechanism consists of a steering wheel mounted on the central axis of the forklift AGV, with the midpoint of the straight-line distance between the left and right drive wheels coinciding with the central axis. Based on the aforementioned drive mechanism and rigid body motion constraints, the driving speed of the left drive wheel is obtained. Drive speed of the right drive wheel and the angle of the steering wheel The transformation relationship between them: in, The distance is the midpoint between the steering wheel and the straight-line distance. The distance between the center of the left drive wheel and the center of the right drive wheel is the wheel distance.

3. The path tracking control method for a forklift AGV according to claim 2, characterized in that, The following specific coordinate system established on the tracking path includes: Establish a global coordinate system XOY, and select the midpoint of the straight-line distance as the AGV reference point; Obtain the tracking path of the forklift AGV The AGV reference point is placed on the tracking path. The orthogonal projection point on the origin is set as the origin. , According to the origin Establish a moving coordinate system ,in, axis and origin In the tracking path The tangents on the surface coincide and have the same direction, by Rotate the axis 90° counterclockwise to obtain axis.

4. The path tracking control method for a forklift AGV according to claim 2, characterized in that, The driving methods corresponding to the steering wheels include: electric motor drive and hydraulic drive.

5. The path tracking control method for a forklift AGV according to claim 4, characterized in that, The calculation process for the corresponding driving speed of the left drive wheel, driving speed of the right drive wheel, and steering wheel angle specifically includes: When the corresponding driving method is motor drive, the target angular velocity is calculated according to the control formulas for the target linear velocity and the target angular velocity. According to the target angular velocity Wheelbase and the set target linear velocity The first velocity is calculated using the following formula: Obtain the driving speed of the left drive wheel. and the drive speed of the right drive wheel ; Based on the driving speed of the left drive wheel and the drive speed of the right drive wheel Using the aforementioned transformation relationship, the target steering angle of the steering wheel is calculated. .

6. The path tracking control method for a forklift AGV according to claim 4, characterized in that, The calculation process for the corresponding driving speed of the left drive wheel, driving speed of the right drive wheel, and steering wheel angle also includes: When the corresponding driving method is hydraulic drive, the target angular velocity is calculated according to the control formulas for the target linear velocity and the target angular velocity. According to the target angular velocity ,distance and the set target linear velocity The target turning angle is calculated using the following formula: The target steering angle of the steering wheel is calculated. ; Real-time acquisition of the steering wheel angle According to the angle Wheelbase ,distance and setting the target linear velocity The second velocity is calculated using the following formula: Obtain the driving speed of the left drive wheel. and the drive speed of the right drive wheel .

7. An electronic device, characterized in that, include: Memory, used to store programs; A processor is configured to execute a program stored in the memory, wherein when the processor executes the program stored in the memory, the processor is configured to perform a path tracking control method for a forklift AGV as described in any one of claims 1 to 6.

8. A storage medium, characterized in that, include: The device stores computer-executable instructions for performing a path tracking control method for a forklift AGV as described in any one of claims 1 to 6.

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