CN117601902A - Dual PID tracking control method suitable for front and rear axle independent steering AGVs - Google Patents

Dual PID tracking control method suitable for front and rear axle independent steering AGVs Download PDF

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Publication number
CN117601902A
CN117601902A CN202410019028.3A CN202410019028A CN117601902A CN 117601902 A CN117601902 A CN 117601902A CN 202410019028 A CN202410019028 A CN 202410019028A CN 117601902 A CN117601902 A CN 117601902A
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China
Prior art keywords
front wheel
error
tracking control
deflection angle
yaw
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Inventor
梁培栋
李瑞峰
王亮亮
霍光磊
吴宇雄
温宽昌
黄小春
梁凤顺
陈泰山
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Fujian Quanzhou Advanced Manufacturing Technology Research Institute
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Fujian Quanzhou Advanced Manufacturing Technology Research Institute
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Priority to CN202410019028.3A priority Critical patent/CN117601902A/en
Publication of CN117601902A publication Critical patent/CN117601902A/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W60/00—Drive control systems specially adapted for autonomous road vehicles
    • B60W60/001—Planning or execution of driving tasks

Abstract

The invention discloses a double PID tracking control method for an AGV with independent steering of a front axle and a rear axle, wherein the AGV vehicle is characterized in that the front axle of the front wheel and the rear axle of the rear wheel can respectively and independently steer, the tracking control method comprises the steps that the tracking control of a straight line path is marked as a straight line mode and/or the tracking control of a turning path is marked as a turning mode, the tracking control of the straight line mode or the turning mode is executed and comprises the tracking control of the front wheel and the rear wheel, and the tracking control method is consistent with the tracking control of the front wheel and the tracking control execution of the prognosis wheel due to the fact that the front wheel and the rear wheel can respectively steer independently. The method is an implementation method for tracking control on a path consisting of a straight line and an arc aiming at a chassis model with front wheels and rear wheels which are independently turned and can not rotate in situ.

Description

Dual PID tracking control method suitable for front and rear axle independent steering AGVs
Technical Field
The invention relates to the technical field of automatic driving tracking control.
Background
The tracking control technique of the autopilot refers to a technique for realizing vehicle tracking and control in an autopilot system. It is an important component in an autopilot system to ensure that the vehicle can accurately track a selected path and control based on real-time environment and sensor data to achieve safe, stable and efficient travel. Tracking control techniques use control algorithms to calculate control commands for the vehicle to achieve a desired trajectory tracking, common control algorithms include PID control, model Predictive Control (MPC), and the like. Model predictive control predicts vehicle behavior over a period of time in the future by building a vehicle dynamics model and an environmental model, and controls based on the prediction results to achieve a more accurate tracking effect. Tracking control techniques require control and adjustment in real time based on vehicle conditions and environmental changes. By collecting and processing the sensor data in real time, the tracking control system can continuously update the state and environment information of the vehicle and adjust the control instruction according to the feedback information so as to realize an accurate tracking effect. In general, the performance of the algorithm can be exerted to the greatest extent only by using a corresponding tracking control algorithm according to a specific scene and a vehicle, so that the optimal control effect is realized.
The existing tracking control technology is mainly oriented to a differential model chassis, has few control modes aiming at a chassis model with front and rear wheels steering independently and being unable to rotate in situ, and the existing PID tracking control method has larger tracking error for a turning scene. Aiming at the limitation, the invention provides a realization method for tracking control on a path consisting of a straight line and an arc aiming at a chassis model with independent steering of front wheels and rear wheels and non-in-situ rotation.
Disclosure of Invention
The invention aims to provide a double PID tracking control method suitable for an AGV with independent steering of front and rear axles, and provides a realization method for tracking control on a path formed by a straight line and an arc by aiming at the chassis model with independent steering of front and rear wheels and incapability of rotating in situ.
In order to achieve the above purpose, the technical scheme of the invention is as follows: the double PID tracking control method is suitable for the AGV with independent front and rear axles, wherein the front axle and the rear axle of the AGV vehicle, which are front wheels, can be respectively and independently controlled in steering, the tracking control method comprises the following steps that the tracking control of a straight line path is marked as a straight line mode and/or the tracking control of a turning path is marked as a turning mode, the tracking control of the straight line mode or the turning mode executes the tracking control comprising the front wheels and the rear wheels, and the tracking control method is described by taking the tracking control of the front wheels as an execution example, the execution method of the rear wheels can be obtained by referring to the front wheels equally, and the steps of the front wheel tracking control method of the straight line mode and/or the turning mode are as follows:
straight line mode:
1) Obtaining magnetic navigation positioning;
2) The given linear velocity is a fixed value;
3) Calculating to obtain a transverse deviation error, an accumulated transverse deviation error and a heading error of a front axle center of the front wheel to an arc path;
4) Determining a PID coefficient, and calculating a dynamic front wheel deflection angle value corresponding to the PID;
5) Determining a final front wheel deflection angle value;
6) The final front wheel deflection angle w obtained through calculation is used as an actual control value to be output to a controller, and the front wheel is controlled to deflect according to a set value;
7) Returning to step 2), the calculation is performed in a loop. Thus realizing PID tracking control on the front wheels of the vehicle;
turning mode:
s1) obtaining magnetic navigation positioning;
s2) the given linear velocity is a fixed value;
s3) calculating to obtain a transverse offset error, an accumulated transverse offset error and a heading error of a front axle center of the front wheel to an arc path;
s4) determining PID coefficients, and calculating dynamic front wheel deflection angle values corresponding to the PID;
s5) determining a static deflection angle value corresponding to the front tire;
s6) determining a final front wheel deflection angle value;
s7) outputting the final front wheel deflection angle w obtained through calculation to a controller as an actual control value, and controlling the front wheel to deflect according to a set value;
s8) returning to the step 2), and circularly performing calculation.
In the straight line mode:
step 3) is as follows:
through steps 1) and 2), first, calculate the lateral offset error of the front axle center of the front wheel to the circular arc path and record as d ef And the lateral error is set to be positive when the front wheel is outside the path and negative when the front wheel is inside the path;
next, the accumulated lateral offset error is calculated and noted as i ef The accumulated lateral offset error is the accumulated sum of the lateral offset errors calculated from the start time to the current time;
then, calculate heading error and mark as θ ef The course error is recorded as yaw by taking anticlockwise as positive and the course error as the front wheel course f The reference course is recorded as yaw rf The difference of (a), i.e. θ ef ＝yaw f -yaw rf The reference course is the corresponding tangential direction of the nearest point of the front wheel on the circular arc;
step 4) is to calculate the lateral error d in step 3) ef Cumulative lateral error i ef And heading error θ ef Then, determining PID parameters through debugging, and obtaining a corresponding dynamic front wheel deflection angle w 1 ＝Pd ef +Ii ef +Dθ ef 。
Step 5) is such that the final front wheel yaw angle for control is denoted as w, and the dynamic front wheel yaw angle w obtained in step 4) is 1 ＝Pd ef +Ii ef +Dθ ef As a final useIn the controlled front wheel yaw value, i.e. w=w 1 。
In the turning mode:
step S3) is as follows:
through steps S1) and S2), first, calculate the lateral offset error of the front axle center of the front wheel to the circular arc path and record as d ef And the lateral error is set to be positive when the front wheel is outside the path and negative when the front wheel is inside the path;
next, the accumulated lateral offset error is calculated and noted as i ef The accumulated lateral offset error is the accumulated sum of the lateral offset errors calculated from the start time to the current time;
then, calculate heading error and mark as θ ef The course error is recorded as yaw by taking anticlockwise as positive and the course error as the front wheel course f The reference course is recorded as yaw rf The difference of (a), i.e. θ ef ＝yaw f -yaw rf The reference course is the corresponding tangential direction of the nearest point of the front wheel on the circular arc;
step S4) is to calculate the lateral error d in step S3) ef Cumulative lateral error i ef And heading error θ ef Then, determining PID parameters through debugging, and obtaining a corresponding dynamic front wheel deflection angle marked as w 1 ，
w 1 ＝Pd ef +Ii ef +Dθ ef ；
Step S5) is recorded as d according to the wheelbase w The static deflection angle value corresponding to the front wheel tire is determined to be w 2 ，
Step 6) calculating the final front wheel deflection angle for control as w=w according to the dynamic front wheel deflection angle and the static front wheel deflection angle 1 +w 2 。
The AGV is characterized in that a magnetic sensor is respectively arranged at the center of a front axle of a front wheel and the center of a rear axle of a rear wheel, and the two magnetic sensors respectively sense magnetic nails on a path; step 1) and/or step 1) obtaining the magnetic navigation positioning of the two magnetic sensors; in step 3) and/or step S3), when the two magnetic sensors sense the magnetic nails at the same time, the real value of the lateral error is directly sensed by the magnetic sensors to be used as a correction value to replace the lateral offset error for calculation, and when the two magnetic sensors do not sense the magnetic nails at the same time, the sensor data of the odometer or the inertial measurement unit and the like are acquired to calculate the lateral offset error based on the latest correction value.
The AGV vehicle is controlled by selecting different modes at different road sections, selecting a straight line mode at a straight line road section, selecting a turning mode at an arc road section, and performing an automatic switching mode at the joint point of the straight line road section and the arc road section.
The rule of the switching mode is as follows: taking the center of a connecting line of a front wheel and a rear wheel shaft of the vehicle as a reference point, connecting a running track of the reference point by a straight line and an arc, taking a straight line section as an example, starting from the straight line section, and controlling in a straight line mode; when the datum point moves to the joint point of the linear track and the circular arc track, switching from the linear mode to the turning mode for control, and moving along the circular arc; when the datum point continues to run to the joint point of the circular arc and the linear track, the control is performed by switching from the turning mode to the linear mode.
By adopting the technical scheme, the invention has the beneficial effects that: the method is mainly suitable for independent steering control of a front wheel front axle and a rear wheel rear axle, and the chassis system is an AGV vehicle which can not steer in situ, and tracking control is carried out on a straight line and an arc path.
Drawings
Fig. 1 and 2 are schematic diagrams of three coordinate systems of a vehicle in different modes in a dual PID tracking control method suitable for an AGV with independent steering of front and rear axles according to the present invention.
FIG. 3 is a schematic view of the engagement points of the switching mode in a dual PID tracking control method for an independent front and rear axle steering AGV according to the invention.
Detailed Description
In order to further explain the technical scheme of the invention, the invention is explained in detail by specific examples.
The double PID tracking control method suitable for the AGV with independent front and rear axles includes that the front axle of the AGV vehicle as front wheel and the rear axle of the rear wheel can be controlled separately and independently, and the tracking control method includes that the tracking control of the straight line path is marked as a straight line mode and the tracking control of the turning path is marked as a turning mode. Since the present invention is directed to an AGV vehicle in which a front axle and a rear axle can be independently steered, front wheels and rear wheels of the vehicle can be independently steered, respectively, and in a tracking control method for the rear wheels, whether in a straight mode or a cornering mode, the method steps performed by the method can be equally obtained with reference to the front wheels, and the following description will mainly be made with reference to the front wheels as an example.
The linear mode is a common PID control mode, and the tracking control method comprises the following steps:
1) Obtaining the magnetic navigation positioning.
The tracking control mainly focuses on three coordinate systems, namely a vehicle front wheel coordinate system, a vehicle rear wheel coordinate system and a vehicle center coordinate system, and as shown in fig. 1, the positioning of the vehicle center relative to the magnetic navigation coordinate system is obtained through the relation among the coordinate systems, so that the positioning of the vehicle center in the magnetic navigation coordinate system is obtained.
2) The given linear velocity is a fixed value.
The linear speeds of the front and rear wheels of the vehicle are uniform, giving a linear speed value.
3) And calculating to obtain the transverse offset error, the accumulated transverse offset error and the heading error of the front axle center of the front wheel to the circular arc path.
Through steps 1) and 2), first, calculate the lateral offset error of the front axle center of the front wheel to the circular arc path and record as d ef As shown in fig. 1, i.e., the shortest distance between the front wheel and the path, the lateral error is set to be positive when the front wheel is outside the path, and the lateral error is set to be negative when the front wheel is inside the path;
next, the accumulated lateral offset error is calculated and noted as i ef The accumulated lateral offset error is the accumulated sum of the lateral offset errors calculated from the start time to the current time;
then, calculate heading error and mark as θ ef As shown in FIG. 1, the heading error is the heading of the front wheel and is recorded as yaw f The reference course is recorded as yaw rf The difference of (a), i.e. θ ef ＝yaw f -yaw rf Wherein the reference heading is the corresponding tangential direction of the nearest point of the front wheel on the circular arc, as shown by the arrow direction in fig. 1.
4) And determining a PID coefficient, and calculating a dynamic front wheel deflection angle value corresponding to the PID.
In step 3) the lateral error d is calculated ef Cumulative lateral error i ef And heading error θ ef Then, determining PID parameters through debugging, and obtaining a corresponding dynamic front wheel deflection angle w 1 ＝Pd ef +Ii ef +Dθ ef 。
5) A final front wheel yaw angle value is determined.
The final front wheel yaw angle for control is denoted as w, and the dynamic front wheel yaw angle w obtained by step 4) is calculated as w 1 ＝Pd ef +Ii ef +Dθ ef As the front wheel yaw value finally used for control, i.e. w=w 1 . The calculation of the yaw angle of the rear wheels is identical to the calculation of the yaw angle of the front wheels.
6) And outputting the final front wheel deflection angle w obtained through calculation to a controller as an actual control value, and controlling the front wheels to deflect according to a set value.
7) Returning to step 2), the calculation is performed in a loop. Thus realizing PID tracking control on the front wheels of the vehicle.
The steps of the method for PID tracking control of the rear wheels of the vehicle are consistent with those of the method for PID tracking control of the front wheels, and can be directly substituted and deduced by a person skilled in the art through the content, so that the description is not repeated in the embodiment, and the clear understanding of the technical scheme of the invention by the person skilled in the art is not affected.
The PID control mode of static value plus dynamic adjustment is adopted in the turning mode with fixed turning radius, and the tracking control method comprises the following steps:
s1) obtaining the magnetic navigation positioning.
The tracking control mainly focuses on three coordinate systems, namely a vehicle front wheel coordinate system, a vehicle rear wheel coordinate system and a vehicle center coordinate system, and as shown in fig. 2, the positioning of the vehicle center relative to the magnetic navigation coordinate system is obtained through the relation among the coordinate systems, so that the positioning of the vehicle center in the magnetic navigation coordinate system is obtained.
S2) the given linear velocity is a fixed value.
The linear speeds of the front and rear wheels of the vehicle are uniform, giving a linear speed value.
S3) calculating to obtain the transverse offset error, the accumulated transverse offset error and the heading error of the front axle center of the front wheel to the circular arc path.
Through steps S1) and S2), first, calculate the lateral offset error of the front axle center of the front wheel to the circular arc path and record as d ef As shown in fig. 2, i.e., the shortest distance between the front wheel and the path, the lateral error is set to be positive when the front wheel is outside the path, and the lateral error is set to be negative when the front wheel is inside the path;
next, the accumulated lateral offset error is calculated and noted as i ef The accumulated lateral offset error is the accumulated sum of the lateral offset errors calculated from the start time to the current time;
then, calculate heading error and mark as θ ef As shown in FIG. 2, the heading error is the heading of the front wheel and is recorded as yaw f The reference course is recorded as yaw rf The difference of (a), i.e. θ ef ＝yaw f -yaw rf Wherein the reference heading is the corresponding tangential direction of the nearest point of the front wheel on the circular arc, as indicated by the arrow direction in fig. 2.
S4) determining PID coefficients, and calculating dynamic front wheel deflection angle values corresponding to the PID.
In step S3) a lateral error d is calculated ef Cumulative lateral error i ef And heading error θ ef Then, determining PID parameters through debugging, and obtaining a corresponding dynamic front wheel deflection angle marked as w 1 。
w 1 ＝Pd ef +Ii ef +Dθ ef 。
S5) is marked as d according to the wheelbase w The static deflection angle value corresponding to the front wheel tire is determined to be w 2 。
S6) calculating a final front wheel deflection angle value.
From the dynamic front wheel yaw angle and the static front wheel yaw angle, the front wheel yaw angle finally used for control is calculated to be w=w 1 +w 2 . The calculation of the yaw angle of the rear wheels is identical to the calculation of the yaw angle of the front wheels.
S7) outputting the final front wheel deflection angle w obtained through calculation to a controller as an actual control value, and controlling the front wheels to deflect according to a set value.
S8) back to step S2), the calculation is performed cyclically. Thus realizing PID tracking control on the front wheels of the vehicle.
The steps of the method for PID tracking control of the rear wheels of the vehicle are consistent with those of the method for PID tracking control of the front wheels, and can be directly substituted and deduced by a person skilled in the art through the content, so that the description is not repeated in the embodiment, and the clear understanding of the technical scheme of the invention by the person skilled in the art is not affected.
In the using process of the AGV, different modes are selected for control on different road sections, namely, the straight line mode control is adopted on the straight line road section, the turning mode control is adopted on the arc road section, the switching is stopped at the connecting point, and the switching is stopped again so as to avoid excessive deviation of the vehicle from the track. As shown in fig. 3, when traveling straight from the left, the vehicle is in the straight mode control, and when moving to the engagement point 1, the vehicle is switched from the straight mode to the turning mode control, and when the vehicle continues to move to the engagement point 2, the vehicle is switched from the turning mode to the straight mode control. The specific description is as follows: taking the center of the connecting line of the front wheel and the rear wheel axle of the vehicle as a reference point, the running track of the reference point is formed by connecting a straight line and an arc, and taking a straight line road section as an example, the mode switching rule is as follows: starting from the straight line section, controlling in a straight line mode; when the datum point moves to the joint point of the linear track and the circular arc track (namely, the joint point 1 is shown as a figure, a circular arc road section is to be entered), the datum point is controlled from a linear mode to a turning mode, and moves along the circular arc; when the reference point continues to move to the point where the arc and the straight line track are connected (i.e. the straight line section is to be entered as shown in the connection point 2), the control is performed by switching from the turning mode to the straight line mode, and the process returns to the step 2 of the straight line mode.
In addition, if the AGV vehicle in the embodiment is that the center of a front axle of a front wheel and the center of a rear axle of a rear wheel are respectively provided with a magnetic sensor, the two magnetic sensors respectively sense magnetic nails on a path; step 1) and step 1) are to obtain the magnetic navigation positioning of two magnetic sensors; in step 3) and step 3), when both magnetic sensors sense magnetic nails at the same time, the actual value of the transverse error is directly sensed by the magnetic sensors to be used as a correction value to replace the transverse offset error for calculation, and when both magnetic sensors do not sense magnetic nails at the same time, the data of any sensor capable of carrying out relative motion estimation such as an odometer or an inertial measurement unit are acquired, and the calculation of the transverse offset error is carried out based on the latest correction value, namely, the data of both magnetic sensors are used as correction values, and the data of other sensors such as the odometer or the inertial measurement unit are used as prediction values to calculate the transverse error of the front wheel or the rear wheel relative to a reference path.
The above examples and drawings are not intended to limit the form or form of the present invention, and any suitable variations or modifications thereof by those skilled in the art should be construed as not departing from the scope of the present invention.

Claims (10)

1. A double PID tracking control method suitable for a front and rear axle independent steering AGV is characterized in that a front axle of an AGV vehicle which is a front wheel and a rear axle of a rear wheel can be respectively and independently steered, the tracking control method comprises the following steps of marking the tracking control of a straight line path as a straight line mode, the tracking control of the tracking control comprises the tracking control of the front wheel and the rear wheel, the tracking control method is described by taking the tracking control of the front wheel as an execution example, the execution method steps of the rear wheel can be obtained by referring to the front wheel equally, and the tracking control method of the front wheel comprises the following steps:
1) Obtaining magnetic navigation positioning;
2) The given linear velocity is a fixed value;
3) Calculating to obtain a transverse deviation error, an accumulated transverse deviation error and a heading error of a front axle center of the front wheel to an arc path;
4) Determining a PID coefficient, and calculating a dynamic front wheel deflection angle value corresponding to the PID;
5) Determining a final front wheel deflection angle value;
6) The final front wheel deflection angle w obtained through calculation is used as an actual control value to be output to a controller, and the front wheel is controlled to deflect according to a set value;
7) Returning to step 2), the calculation is performed in a loop. Thus realizing PID tracking control on the front wheels of the vehicle.
2. The dual PID tracking control method for an independent front and rear axle steering AGV of claim 1 wherein step 3) is:
through steps 1) and 2), first, calculate the lateral offset error of the front axle center of the front wheel to the circular arc path and record as d ef And the lateral error is set to be positive when the front wheel is outside the path and negative when the front wheel is inside the path;
next, the accumulated lateral offset error is calculated and noted as i ef The accumulated lateral offset error is the accumulated sum of the lateral offset errors calculated from the start time to the current time;
then, calculate heading error and mark as θ ef In a counterclockwise directionFor positive, the course error is that the course of the front wheel is recorded as yaw f The reference course is recorded as yaw rf The difference of (a), i.e. θ ef ＝yaw f -yaw rf The reference course is the corresponding tangential direction of the nearest point of the front wheel on the circular arc;
step 4) is to calculate the lateral error d in step 3) ef Cumulative lateral error i ef And heading error θ ef Then, determining PID parameters through debugging, and obtaining a corresponding dynamic front wheel deflection angle w 1 ＝Pd ef +Ii ef +Dθ ef 。
Step 5) is such that the final front wheel yaw angle for control is denoted as w, and the dynamic front wheel yaw angle w obtained in step 4) is 1 ＝Pd ef +Ii ef +Dθ ef As the front wheel yaw value finally used for control, i.e. w=w 1 。
3. The dual PID tracking control method for an AGV with independent front and rear axle steering as claimed in claim 1 or 2, wherein the AGV is a front axle center of front wheels and a rear axle center of rear wheels, respectively, provided with magnetic sensors, which respectively sense magnetic nails on paths; step 1), acquiring magnetic navigation positioning of two magnetic sensors; in the step 3), when the two magnetic sensors sense the magnetic nails at the same time, the real value of the transverse error is directly sensed by the magnetic sensors to be used as a correction value to replace the transverse offset error for calculation, and when the two magnetic sensors do not sense the magnetic nails at the same time, the sensor data of the odometer or the inertial measurement unit are acquired to calculate the transverse offset error based on the latest correction value.
4. A double PID tracking control method suitable for a front-rear axle independent steering AGV is characterized in that a front axle of an AGV vehicle which is a front wheel and a rear axle of a rear wheel can be respectively and independently steered, the tracking control method comprises tracking control of a turning path which is recorded as a turning mode, the tracking control of the tracking control comprises tracking control of the front wheel and the rear wheel, the tracking control method is described by taking the tracking control of the front wheel as an execution example, the execution method steps of the rear wheel can be obtained by referring to the front wheel equally, and the tracking control method of the front wheel comprises the following steps:
s1) obtaining magnetic navigation positioning;
s2) the given linear velocity is a fixed value;
s3) calculating to obtain a transverse offset error, an accumulated transverse offset error and a heading error of a front axle center of the front wheel to an arc path;
s4) determining PID coefficients, and calculating dynamic front wheel deflection angle values corresponding to the PID;
s5) determining a static deflection angle value corresponding to the front tire;
s6) determining a final front wheel deflection angle value;
s7) outputting the final front wheel deflection angle w obtained through calculation to a controller as an actual control value, and controlling the front wheel to deflect according to a set value;
s8) returning to the step 2), and circularly performing calculation.
5. The dual PID tracking control method for an AGV with independent front and rear axle steering as claimed in claim 4, wherein the step S3) is as follows:
through steps S1) and S2), first, calculate the lateral offset error of the front axle center of the front wheel to the circular arc path and record as d ef And the lateral error is set to be positive when the front wheel is outside the path and negative when the front wheel is inside the path;
next, the accumulated lateral offset error is calculated and noted as i ef The accumulated lateral offset error is the accumulated sum of the lateral offset errors calculated from the start time to the current time;
then, calculate heading error and mark as θ ef The course error is recorded as yaw by taking anticlockwise as positive and the course error as the front wheel course f The reference course is recorded as yaw rf The difference of (a), i.e. θ ef ＝yaw f -yaw rf The reference course is the corresponding tangential direction of the nearest point of the front wheel on the circular arc;
step S4) is to calculate the lateral error d in step S3) ef Cumulative lateral error i ef And heading error θ ef After that, the processing unit is configured to,determining PID parameters through debugging, and obtaining a corresponding dynamic front wheel deflection angle marked as w 1 ，
w 1 ＝Pd ef +Ii ef +Dθ ef ；
Step S5) is recorded as d according to the wheelbase w The static deflection angle value corresponding to the front wheel tire is determined to be w 2 ，
Step 6) calculating the final front wheel deflection angle for control as w=w according to the dynamic front wheel deflection angle and the static front wheel deflection angle 1 +w 2 。
6. The dual PID tracking control method for an AGV with independent front and rear axle steering as claimed in claim 4 or 5, wherein the AGV is a front axle center of front wheels and a rear axle center of rear wheels, respectively, provided with magnetic sensors, which respectively sense magnetic nails on paths; step 1), acquiring magnetic navigation positioning of two magnetic sensors; in the step 3), when the two magnetic sensors sense the magnetic nails at the same time, the real value of the transverse error is directly sensed by the magnetic sensors to be used as a correction value to replace the transverse offset error for calculation, and when the two magnetic sensors do not sense the magnetic nails at the same time, the sensor data of the odometer or the inertial measurement unit are acquired to calculate the transverse offset error based on the latest correction value.
7. A double PID tracking control method suitable for a front-rear axle independent steering AGV is characterized in that a front axle of an AGV vehicle which is a front wheel and a rear axle of a rear wheel can be respectively and independently steered, the tracking control method comprises the following steps that the tracking control of a straight line path is marked as a straight line mode and the tracking control of a turning path is marked as a turning mode, the tracking control of the straight line mode and the turning mode is carried out and comprises the tracking control of the front wheel and the rear wheel, the front wheel and the rear wheel can be respectively and independently steered, the tracking control method is described by taking the tracking control of the front wheel as an example, the execution method steps of the rear wheel can be obtained by referring to the front wheel equally, and the front wheel tracking control method of the straight line mode and/or the turning mode comprises the following steps:
straight line mode:
1) Obtaining magnetic navigation positioning;
2) The given linear velocity is a fixed value;
3) Calculating to obtain a transverse deviation error, an accumulated transverse deviation error and a heading error of a front axle center of the front wheel to an arc path;
4) Determining a PID coefficient, and calculating a dynamic front wheel deflection angle value corresponding to the PID;
5) Determining a final front wheel deflection angle value;
6) The final front wheel deflection angle w obtained through calculation is used as an actual control value to be output to a controller, and the front wheel is controlled to deflect according to a set value;
7) Returning to step 2), the calculation is performed in a loop. Thus realizing PID tracking control on the front wheels of the vehicle;
turning mode:
s1) obtaining magnetic navigation positioning;
s2) the given linear velocity is a fixed value;
s3) calculating to obtain a transverse offset error, an accumulated transverse offset error and a heading error of a front axle center of the front wheel to an arc path;
s4) determining PID coefficients, and calculating dynamic front wheel deflection angle values corresponding to the PID;
s5) determining a static deflection angle value corresponding to the front tire;
s6) determining a final front wheel deflection angle value;
s7) outputting the final front wheel deflection angle w obtained through calculation to a controller as an actual control value, and controlling the front wheel to deflect according to a set value;
s8) returning to the step 2), and circularly performing calculation.
8. The dual PID tracking control method for an independent front and rear axle steering AGV of claim 7 wherein in the straight line mode:
step 3) is as follows:
through steps 1) and 2), first, calculate the lateral offset error of the front axle center of the front wheel to the circular arc path and record as d ef And the lateral error is set to be positive when the front wheel is outside the path and negative when the front wheel is inside the path;
next, the accumulated lateral offset error is calculated and noted as i ef The accumulated lateral offset error is the accumulated sum of the lateral offset errors calculated from the start time to the current time;
then, calculate heading error and mark as θ ef The course error is recorded as yaw by taking anticlockwise as positive and the course error as the front wheel course f The reference course is recorded as yaw rf The difference of (a), i.e. θ ef ＝yaw f -yaw rf The reference course is the corresponding tangential direction of the nearest point of the front wheel on the circular arc;
step 4) is to calculate the lateral error d in step 3) ef Cumulative lateral error i ef And heading error θ ef Then, determining PID parameters through debugging, and obtaining a corresponding dynamic front wheel deflection angle w 1 ＝Pd ef +Ii ef +Dθ ef 。
Step 5) is such that the final front wheel yaw angle for control is denoted as w, and the dynamic front wheel yaw angle w obtained in step 4) is 1 ＝Pd ef +Ii ef +Dθ ef As the front wheel yaw value finally used for control, i.e. w=w 1 ；
And/or, in the turning mode:
step S3) is as follows:
through steps S1) and S2), first, calculate the lateral offset error of the front axle center of the front wheel to the circular arc path and record as d ef And the lateral error is set to be positive when the front wheel is outside the path and negative when the front wheel is inside the path;
next, the accumulated lateral offset error is calculated and noted as i ef The accumulated lateral offset error is the accumulated sum of the lateral offset errors calculated from the start time to the current time;
then, calculate heading error and mark as θ ef Heading with anticlockwise direction as positiveThe error is the heading of the front wheel recorded as yaw f The reference course is recorded as yaw rf The difference of (a), i.e. θ ef ＝yaw f -yaw rf The reference course is the corresponding tangential direction of the nearest point of the front wheel on the circular arc;
step S4) is to calculate the lateral error d in step S3) ef Cumulative lateral error i ef And heading error θ ef Then, determining PID parameters through debugging, and obtaining a corresponding dynamic front wheel deflection angle marked as w 1 ，
w 1 ＝Pd ef +Ii ef +Dθ ef ；
Step S5) is recorded as d according to the wheelbase w The static deflection angle value corresponding to the front wheel tire is determined to be w 2 ，
Step 6) calculating the final front wheel deflection angle for control as w=w according to the dynamic front wheel deflection angle and the static front wheel deflection angle 1 +w 2 。
9. The dual PID tracking control method for an AGV with independent front and rear axle steering as claimed in claim 7 or 8, wherein the AGV is a front axle center of front wheels and a rear axle center of rear wheels, respectively, provided with magnetic sensors, which respectively sense magnetic nails on paths; step 1) and step 1) are to obtain the magnetic navigation positioning of two magnetic sensors; in the step 3) and the step 3), when the two magnetic sensors sense the magnetic nails at the same time, the real value of the transverse error is directly sensed by the magnetic sensors to be used as a correction value to replace the transverse offset error for calculation, and when the two magnetic sensors do not sense the magnetic nails at the same time, the sensor data of the odometer or the inertial measurement unit are acquired to calculate the transverse offset error based on the latest correction value.
10. The dual PID tracking control method for an AGV with independent front and rear axle steering as claimed in any one of claims 7 to 9, wherein the AGV vehicle is controlled in different modes in different road segments, in a straight line mode in a straight line segment, in a turning mode in a circular arc segment, and in an automatic switching mode at the junction point between the straight line segment and the circular arc segment, the switching mode is as follows: taking the center of a connecting line of a front wheel and a rear wheel shaft of the vehicle as a reference point, connecting a running track of the reference point by a straight line and an arc, taking a straight line section as an example, starting from the straight line section, and controlling in a straight line mode; when the datum point moves to the joint point of the linear track and the circular arc track, switching from the linear mode to the turning mode for control, and moving along the circular arc; when the datum point continues to run to the joint point of the circular arc and the linear track, the control is performed by switching from the turning mode to the linear mode.
CN202410019028.3A 2024-01-05 2024-01-05 Dual PID tracking control method suitable for front and rear axle independent steering AGVs Pending CN117601902A (en)

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CN202410019028.3A CN117601902A (en) 2024-01-05 2024-01-05 Dual PID tracking control method suitable for front and rear axle independent steering AGVs

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CN202410019028.3A CN117601902A (en) 2024-01-05 2024-01-05 Dual PID tracking control method suitable for front and rear axle independent steering AGVs

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