Data transmission system for motion trajectory planning of single-steering-wheel AGV

Abstract

The present invention relates to the technical field of path planning data. Disclosed is a data transmission system for motion trajectory planning of a single-steering-wheel AGV. The system comprises an AGV autonomous navigation control system, wherein the AGV autonomous navigation control system comprises a localization and mapping function module, a decision-making and scheduling module, and a planning and control module, and the planning and control module comprises a motion planning module, a physical model module, and a tracking control module. The data transmission system for motion trajectory planning of the single-steering-wheel AGV used by the present invention provides an autonomous navigation motion framework for the single-steering-wheel AGV. The framework not only can guide the technology research and development of a path planning algorithm for a project involved in the present invention, but also can ensure the consistency of upstream and downstream technical requirements, thus improving the project development efficiency, and providing a basis and foundation for autonomous navigation research and development projects in other logistics scenarios.

Description

A data transmission system for single-steering wheel AGV motion trajectory planning Technical Field

[0001] The present invention relates to the field of data technology for path planning, and in particular to a data transmission system for single-steering-wheel AGV motion trajectory planning. Background Art

[0002] As an unmanned intelligent handling device, AGV plays an important role in manufacturing production, warehousing and logistics, and other operational links. Among them, single-steering-wheel AGVs have the advantages of a simple chassis structure, a straightforward drive method, and low cost, and are widely used in the field of industrial logistics. However, when planning the path and controlling the motion of this type of AGV, it is necessary to additionally consider the non-holonomic constraints of the wheels. This ensures that the robot can always maintain a non-slip rolling state of the wheels within a given motion path, thereby ensuring a high degree of controllable motion accuracy during autonomous navigation. If a reasonable, reachable, and collision-free global path can be planned for the autonomous navigation of a single-steering-wheel AGV, the difficulty of trajectory tracking control can be reduced, and the operating efficiency and trajectory tracking accuracy of the AGV can be significantly improved, thereby providing technical support for the accurate movement of the AGV's autonomous navigation. Summary of the Invention

[0003] The purpose of the present invention is to provide a data transmission system for motion trajectory planning of a single-steering-wheel AGV, and proposes an autonomous navigation motion framework for a single-steering-wheel AGV. This framework can not only guide the technical research and development of path planning algorithms for the projects involved in the present invention, but also ensure the consistency of upstream and downstream technical requirements, thereby improving the efficiency of project development and providing a basis and foundation for autonomous navigation R&D projects in other logistics scenarios.

[0004] To achieve the above objectives, the present invention provides a data transmission system for single-steering wheel AGV motion trajectory planning, including an AGV autonomous navigation control system, the AGV autonomous navigation control system including a positioning and mapping function module, a decision-making and scheduling module, and a planning and control module, the planning and control module including a motion planning module, a physical model module, and a tracking control module.

[0005] Preferably, the data information in the planning and control module includes starting point information, end point information, environmental information, reference path, model information, vehicle information and control quantity.

[0006] Preferably, the motion planning module receives the planning starting point information and end point information transmitted by the decision-making and scheduling module and the environmental information transmitted by the positioning and mapping function module, and plans a non-holonomic constrained reference path suitable for the single-steering wheel AGV to travel and meet the structural conditions of the single-steering wheel AGV based on the constraints of the physical model module.

[0007] Preferably, the tracking control module calculates and outputs the control quantity according to the reference path and the vehicle information transmitted from the positioning and mapping function module, and performs real-time control on the two motors of the single-steering wheel AGV.

[0008] Preferably, the starting point and end point information provided by the decision and scheduling function module are generally the coordinates and orientation of the starting point and the target point;

[0009] Environmental information, which is provided by the positioning and mapping function module, is generally divided into three types according to its data type: feature map, topological map and raster map;

[0010] Reference path: The reference path can be understood as a guideline for the AGV's autonomous movement. The tracking control module will perform real-time closed-loop control of the AGV based on the difference between the vehicle's actual position and the reference path, so that it can travel along the reference path. Due to the discrete nature of computer systems, the reference path consists of a series of discrete path points.

[0011] Model information is determined by the physical model module and provides description information of constraint conditions to the motion planning module and tracking control module. The specific implementation of the motion planning module and tracking control module depends on the physical model module. Model information includes kinematic model and dynamic model.

[0012] The ego vehicle information is the real-time motion information of the AGV provided by the positioning and mapping function module, including the position, orientation, speed and front wheel angle of the ego vehicle in the world coordinate system;

[0013] The control quantity is the information output by the tracking control module to the specific actuator of the AGV. For a single-steering wheel AGV, the control quantity should output the front wheel target angle δ and the front wheel target speed ω.

[0014] Preferably, the kinematic model is as follows:

[0015] In the world coordinate system, the motion of the single-steering wheel AGV is described as follows:

[0016] (1)

[0017] in, is the direction of the world coordinate system; is the center of mass velocity; is the vehicle body yaw angle; is the AGV turning radius; is the sideslip angle of the center of mass;

[0018] The above differential equation cannot describe the front wheel angle The influence of AGV motion state is further established based on the principle of instantaneous center of velocity. Assuming that the wheel is a rigid body and the actual rotation angle of the rear wheel of the single-steering wheel AGV is zero, according to the sine theorem,

[0019] (2)

[0020] in, are the distances from the front and rear wheels to the center of mass respectively;

[0021] The above formula can represent the turning radius R and the front wheel angle Considering the different positions of the center of mass under no load and different load conditions, the sizes of a and b may change, but the wheelbase L of the AGV is usually a fixed value, so further simplification is obtained

[0022] (3)

[0023] Where L is the wheelbase ( );

[0024] Substituting formula (3) into formula (1) we get

[0025] (4)

[0026] In order to meet the non-holonomic constraints of AGV, the wheels of AGV should maintain a non-slip rolling state, and the body of AGV should not slide sideways. Under this assumption, the lateral speed of the body ≈0, then the center of mass side slip angle It is also approximately 0; therefore, the motion state model of the single steering wheel AGV is simplified to

[0027] (5)

[0028] Simplify equation (3) to get the turning radius: Front wheel angle The relationship between:

[0029] (6)

[0030] Consider the front wheel turning angle of a single steering wheel AGV and front wheel speed As the input space, let the front wheel radius be , then

[0031] (7)

[0032] Finally, the kinematic constraint equations of the single-steering-wheel AGV are obtained:

[0033] (8).

[0034] Preferably, the kinetic model is as follows:

[0035] In the kinematic model, the front and rear wheels of the AGV are considered to be rigid bodies, and their true speed direction is equal to the pointing direction of the front and rear wheels. Considering that the tires are not rigid bodies, the AGV generates lateral force due to the centrifugal force during the turning process, causing the contact surface between the tire and the ground to deform laterally. The true driving direction of the wheel will deviate from the original direction of the tire. At a small slip angle, the lateral force is proportional to the slip angle. The proportional coefficient of this relationship is defined as the cornering stiffness. , then the wheel lateral force is expressed as

[0036] (9)

[0037] Taking into account the cornering force, the dynamic analysis of the two-degree-of-freedom AGV model is carried out based on Newton's second law, and the following formula is established:

[0038] (10)

[0039] Where I is the moment of inertia;

[0040] Assuming that the front wheel angle is always controlled within a small range, ≈ 1, then after substituting into formula (9), we have

[0041] (11)

[0042] For the unknown quantity in the above formula , , Further deduction:

[0043] It is the acceleration component of the center of mass of the AGV along the y-axis in its own coordinate system. Since the AGV moves in a curve, it is also accelerated by the motion acceleration along the y-axis. and centripetal acceleration impact, so there is

[0044] (12)

[0045] Analyze the center of mass and the front wheel. According to the principle of rigid body plane motion, we have

[0046] (13)

[0047] in, is the heading angle ; They are the AGV lateral speed and longitudinal speed respectively;

[0048] but

[0049] (14)

[0050] Similarly, we can analyze the relationship between the center of mass and the rear wheel.

[0051] (15)

[0052] Considering the positive and negative relationship in the right-hand coordinate system, when turning left should be less than 0, so it will eventually Expressed as

[0053] (16)

[0054] Substituting, we have

[0055] (17)

[0056] make , the above formula is expressed in the form of state equation matrix,

[0057] (18)

[0058] in, is the direction of the AGV coordinate system.

[0059] Therefore, the present invention adopts the above-mentioned data transmission system for single-steering wheel AGV motion trajectory planning, and based on the product development model, proposes an autonomous navigation motion framework for single-steering wheel AGV. This framework can not only guide the technical development of path planning algorithms for the projects involved in the present invention, but also ensure the consistency of upstream and downstream technical requirements, thereby improving the efficiency of project development, and providing a basis and laying the foundation for autonomous navigation R&D projects in other logistics scenarios.

[0060] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] FIG1 is a functional architecture diagram of a single-steering-wheel AGV autonomous navigation technology system according to an embodiment of the present invention;

[0062] FIG2 is a schematic diagram of a method for expressing start and end point information according to an embodiment of the present invention;

[0063] FIG3 is a schematic diagram of a grid map representation method according to an embodiment of the present invention;

[0064] FIG4 is a schematic diagram of a reference line according to an embodiment of the present invention;

[0065] FIG5 is a kinematic model of a single steering wheel AGV according to an embodiment of the present invention;

[0066] FIG6 is a schematic diagram of tire deformation according to an embodiment of the present invention;

[0067] FIG. 7 is a diagram showing a dynamic force analysis of an embodiment of the present invention. DETAILED DESCRIPTION

[0068] Example

[0069] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0070] This embodiment performs a functional analysis of the single-steering-wheel AGV autonomous navigation technology system based on the German Pahl / Beitz product development model according to the technical research and development requirements for the single-steering-wheel AGV autonomous navigation technology system in the application scenario. Referring to Figure 1, the present invention discloses a data transmission system for single-steering-wheel AGV motion trajectory planning, including an AGV autonomous navigation control system. The AGV autonomous navigation control system includes a positioning and mapping function module, a decision-making and scheduling module, and a planning and control module. The planning and control module includes a motion planning module, a physical model module, and a tracking control module. The physical model module provides a basis for the motion planning module and the tracking control module.

[0071] The data information in the planning and control module includes starting point information, end point information, environmental information, reference path, model information, vehicle information and control quantity.

[0072] The motion planning module receives the planning starting point information and end point information transmitted by the decision-making and scheduling module and the environmental information transmitted by the positioning and mapping function module, and plans a non-holonomic constraint reference path suitable for the single-steering-wheel AGV to travel and meet the structural conditions of the single-steering-wheel AGV based on the constraints of the physical model module.

[0073] The tracking control module calculates and outputs the control quantity based on the reference path and the vehicle information transmitted by the positioning and mapping function module, and controls the two motors of the single-steering wheel AGV in real time.

[0074] The starting point and end point information provided by the decision and scheduling function module are generally the coordinates and orientation of the starting point and the target point, that is, , which is a three-dimensional variable in the world coordinate system, as shown in Figure 2.

[0075] Environmental information is provided by the positioning and mapping module and is generally categorized into three types based on data type: feature maps, topology maps, and raster maps. The principle of raster maps is to divide environmental information into a finite number of discrete grids. Each grid corresponds to a value obtained by the perception fusion algorithm, and the size of the value determines the grid's status, i.e., whether it is occupied or unoccupied, as shown in Figure 3.

[0076] Reference path, the reference path can be understood as the guide line that guides the AGV's autonomous movement. A high-quality reference path should be able to directly become the trajectory of the AGV's actual movement. The tracking control module will perform real-time closed-loop control of the AGV based on the gap between the vehicle's actual position and the reference path, so that it can travel along the reference path. Due to the discrete nature of computer systems, the reference path is generally composed of a series of discrete path points, as shown in Figure 4. Each path point contains its coordinates in the world coordinate system. and angular position and other information.

[0077] The model information is determined by the physical model module and provides descriptive information of the constraints to the motion planning module and the tracking control module. The specific implementation of the motion planning module and the tracking control module depends on the physical model module. The model information generally includes the kinematic model and the dynamic model.

[0078] The kinematic model is as follows:

[0079] As shown in Figure 5, the motion of a single-steering wheel AGV is described in the world coordinate system:

[0080] (1)

[0081] in, is the direction of the world coordinate system; is the center of mass velocity; is the vehicle body yaw angle; is the AGV turning radius; is the sideslip angle of the center of mass;

[0082] The above differential equation cannot describe the front wheel angle The influence of AGV motion state is further established based on the principle of instantaneous center of velocity. Assuming that the wheel is a rigid body and the actual rotation angle of the rear wheel of the single-steering wheel AGV is zero, according to the sine theorem,

[0083] (2)

[0084] in, are the distances from the front and rear wheels to the center of mass respectively;

[0085] The above formula can represent the turning radius R and the front wheel angle Considering the different positions of the center of mass under no load and different load conditions, the sizes of a and b may change, but the wheelbase L of the AGV is usually a fixed value, so further simplification is obtained

[0086] (3)

[0087] Where L is the wheelbase ( );

[0088] Substituting formula (3) into formula (1) we get

[0089] (4)

[0090] In order to meet the non-holonomic constraints of AGV, the wheels of AGV should maintain a non-slip rolling state, and the body of AGV should not slide sideways. Under this assumption, the lateral speed of the body ≈0, then the center of mass side slip angle It is also approximately 0; therefore, the motion state model of the single steering wheel AGV is simplified to

[0091] (5)

[0092] Simplify equation (3) to get the turning radius: Front wheel angle The relationship between:

[0093] (6)

[0094] Consider the front wheel turning angle of a single steering wheel AGV and front wheel speed As the input space, let the front wheel radius be , then

[0095] (7)

[0096] Finally, the kinematic constraint equations of the single-steering-wheel AGV are obtained:

[0097] (8)

[0098] The kinetic model is as follows:

[0099] In the kinematic model, the front and rear wheels of the AGV are considered to be rigid bodies, and their true speed direction is equal to the pointing direction of the front and rear wheels. Considering that the tires are not rigid bodies, the AGV generates lateral force due to the centrifugal force during the turning process, causing the contact surface between the tire and the ground to deform laterally. The true driving direction of the wheel will deviate from the original direction of the tire, as shown in Figure 6. At a small slip angle, the lateral force is proportional to the slip angle. The proportional coefficient of this relationship is defined as the cornering stiffness. , then the wheel lateral force is expressed as

[0100] (9)

[0101] Taking into account the cornering force, a dynamic analysis of the two-DOF AGV model is performed based on Newton's second law. The force analysis diagram is shown in Figure 7, and the following formula is established:

[0102] (10)

[0103] Where I is the moment of inertia;

[0104] Assuming that the front wheel angle is always controlled within a small range, ≈ 1, then after substituting into formula (9), we have

[0105] (11)

[0106] For the unknown quantity in the above formula , , Further deduction:

[0107] It is the acceleration component of the center of mass of the AGV along the y-axis in its own coordinate system. Since the AGV moves in a curve, it is also accelerated by the motion acceleration along the y-axis. and centripetal acceleration impact, so there is

[0108] (12)

[0109] Analyze the center of mass and the front wheel. According to the principle of rigid body plane motion, we have

[0110] (13)

[0111] in, is the heading angle ; They are the AGV lateral speed and longitudinal speed respectively;

[0112] but

[0113] (14)

[0114] Similarly, we can analyze the relationship between the center of mass and the rear wheel.

[0115] (15)

[0116] Considering the positive and negative relationship in the right-hand coordinate system, when turning left should be less than 0, so it will eventually Expressed as

[0117] (16)

[0118] Substituting, we have

[0119] (17)

[0120] make , the above formula is expressed in the form of state equation matrix,

[0121] (18)

[0122] in, is the direction of the AGV coordinate system.

[0123] The ego vehicle information is the real-time motion information of the AGV provided by the positioning and mapping function module, including the position, orientation, speed and front wheel angle of the ego vehicle in the world coordinate system.

[0124] The control quantity is the information output by the tracking control module to the specific actuator of the AGV. For a single-steering wheel AGV, the control quantity should output the front wheel target angle δ and the front wheel target speed ω.

[0125] Therefore, the present invention adopts the above-mentioned data transmission system for single-steering wheel AGV motion trajectory planning and proposes an autonomous navigation motion framework for single-steering wheel AGV. This framework can not only guide the technical research and development of path planning algorithms for the projects involved in the present invention, but also ensure the consistency of upstream and downstream technical requirements, thereby improving the efficiency of project development and providing a basis and laying the foundation for autonomous navigation research and development projects in other logistics scenarios.

[0126] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A data transmission system for single-steering-wheel AGV motion trajectory planning, characterized by: It includes an AGV autonomous navigation control system, which includes a positioning and mapping function module, a decision-making and scheduling module, and a planning and control module. The planning and control module includes a motion planning module, a physical model module, and a tracking control module.

2. The data transmission system for single-steering-wheel AGV motion trajectory planning according to claim 1, characterized in that: The data information in the planning and control module includes starting point information, end point information, environmental information, reference path, model information, vehicle information and control quantity.

3. The data transmission system for single-steering-wheel AGV motion trajectory planning according to claim 1 is characterized by: The motion planning module receives the starting point information and the end point information transmitted by the decision-making and scheduling module and the environmental information transmitted by the positioning and mapping function module, and plans the non-holonomic constraint reference path suitable for the single-steering wheel AGV to travel and meet the structural conditions of the single-steering wheel AGV based on the constraints of the physical model module.

4. The data transmission system for single-steering-wheel AGV motion trajectory planning according to claim 1, characterized in that: The tracking control module calculates and outputs the control quantity based on the reference path and the vehicle information transmitted from the positioning and mapping function module, and performs real-time control on the two motors of the single-steering wheel AGV.

5. The data transmission system for single-steering-wheel AGV motion trajectory planning according to claim 1, characterized in that: The starting point information and the end point information provided by the decision-making and scheduling function module are the coordinates and orientation of the starting point and the target point; The environmental information is provided by the positioning and mapping function module and is divided into feature maps, topological maps and raster maps according to its data type; The reference path is a guideline for the autonomous movement of the AGV. The tracking control module will perform real-time closed-loop control on the AGV based on the difference between the actual position of the AGV and the reference path, so that the AGV will travel along the reference path. Due to the discrete nature of the computer system, the reference path consists of a series of discrete path points. The model information is determined by the physical model module and is used to describe the constraint conditions provided to the motion planning module and the tracking control module. The specific implementation of the motion planning module and the tracking control module depends on the physical model module. The model information includes a kinematic model and a dynamic model. The ego vehicle information is the real-time motion information of the AGV provided by the positioning and mapping function module, including the position, orientation, speed and front wheel angle of the ego vehicle in the world coordinate system; The control quantity is information output by the tracking control module to the specific actuator of the AGV. For a single-steering wheel AGV, the control quantity should output the front wheel target angle δ and the front wheel target speed ω.

6. The data transmission system for single-steering wheel AGV motion trajectory planning according to claim 5 is characterized in that: The kinematic model is as follows: In the world coordinate system, the motion of a single-steering-wheel AGV is described as follows: (1) in, is the direction of the world coordinate system; is the center of mass velocity; is the vehicle body yaw angle; is the AGV turning radius; is the sideslip angle of the center of mass; The above differential equation cannot describe the front wheel angle The influence of AGV motion state is further established based on the principle of instantaneous center of velocity. Assuming that the wheel is a rigid body and the actual rotation angle of the rear wheel of the single-steering wheel AGV is zero, according to the sine theorem, (2) in, are the distances from the front and rear wheels to the center of mass respectively; The above formula can represent the turning radius R and the front wheel angle Considering the different positions of the center of mass under no load and different loads, the sizes of a and b will change, but the wheelbase L of the AGV is usually a fixed value, so further simplification is obtained (3) Where L is the wheelbase ( )； Substituting formula (3) into formula (1) we get (4) In order to meet the non-holonomic constraints of AGV, the wheels of AGV should maintain a non-slip rolling state, and the body of AGV should not slide sideways. Under this assumption, the lateral speed of the body ≈0, then the center of mass side slip angle It is also approximately 0; therefore, the motion state model of the single steering wheel AGV is simplified to (5) Simplify equation (3) to get the turning radius: Front wheel angle The relationship between: (6) The front wheel turning angle of a single steering wheel AGV and front wheel speed As the input space, let the front wheel radius be , then (7) Finally, the kinematic constraint equation of the single-steering wheel AGV is obtained: (8)。 7. The data transmission system for single-steering wheel AGV motion trajectory planning according to claim 5 is characterized in that: The kinetic model is as follows: In the kinematic model, the front and rear wheels of the AGV are considered to be rigid bodies, and their true speed direction is equal to the pointing direction of the front and rear wheels. Considering that the tires are not rigid bodies, the AGV generates lateral force due to the centrifugal force during the turning process, causing the contact surface between the tire and the ground to deform laterally. The true driving direction of the wheel will deviate from the original direction of the tire. At a small slip angle, the lateral force is proportional to the slip angle. The proportional coefficient of this relationship is defined as the cornering stiffness. , then the wheel lateral force is expressed as (9) Taking into account the cornering force, the dynamic analysis of the two-degree-of-freedom AGV model is carried out based on Newton's second law, and the following formula is established: (10) Where I is the moment of inertia; Assuming that the front wheel angle is always controlled within a small range, ≈ 1, then after substituting into formula (9), we have (11) For the unknown quantity in the above formula ， ， Further deduction: It is the acceleration component of the center of mass of the AGV along the y-axis in its own coordinate system. Since the AGV moves in a curve, it is also accelerated by the motion acceleration along the y-axis. and centripetal acceleration impact, so there is (12) Analyze the center of mass and the front wheel. According to the principle of rigid body plane motion, we have (13) in, is the heading angle ; They are the AGV lateral speed and longitudinal speed respectively; but (14) Similarly, we can analyze the relationship between the center of mass and the rear wheel. (15) Due to the positive and negative relationship in the right-hand coordinate system, when turning left should be less than 0, so it will eventually Expressed as (16) Substituting, we have (17) make , the above formula is expressed in the form of state equation matrix, (18) Where I is the moment of inertia.

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