AGV steering wheel control method and system based on permanent magnet motor

Abstract

A kind of AGV rudder wheel control method based on permanent magnet motor, comprising the following steps: real-time acquisition AGV's position, when AGV enters turning point, the advancing speed V of AGV and the tangent angle b of trajectory are obtained, wherein the advancing speed V includes front wheel speed V1 And rear wheel speed V2;According to the advancing speed V of unmanned carrier, front wheel steering angle θ1 And the steering angle θ2 of rear wheel are calculated respectively;According to steering angle θ1, steering angle θ2 And the tangent angle b of trajectory, the deviation angle A1 of front wheel and the deviation angle A2 of rear wheel are obtained;According to the size of deviation angle A1 and deviation angle A2, the control mode of front wheel permanent magnet motor and the control mode of rear wheel permanent magnet motor are selected respectively.The present application realizes high-precision, high-efficiency and high-safety unmanned carrier navigation and control by real-time acquisition AGV's position, speed and trajectory information, and accurate speed adjustment and steering control are carried out accordingly, and intelligent motor control selection is selected.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of steering wheel control, and in particular to an AGV steering wheel control method and system based on a permanent magnet motor. BACKGROUND

[0002] An AGV (Automated Guided Vehicles) is an automatic navigation vehicle, and a laser navigation vehicle. The AGV is characterized in that it is unmanned, and the AGV is equipped with an automatic guiding system, so that the AGV can automatically travel along a predetermined route without manual navigation, and automatically transport goods or materials from a starting point to a destination.

[0003] The AGV steering wheel refers to an integrated mechanical mechanism that inherits a driving motor and a motor. After the AGV is installed with the steering wheel, the AGV can realize simultaneous steering and translation, the AGV steering wheel has high adaptability, and can be quickly arranged on the AGV. In cooperation with the existing line navigation technology, the AGV can realize automatic navigation and obstacle avoidance. When turning, a customized trajectory is usually used to turn the AGV, and the trajectory is calculated through several points on a continuous curve. However, in this way, since the trolley is dynamically running, there is a deviation between the motion trajectory of the AGV and the given trajectory route, the motion of the vehicle is based on the response to the deviation, and in the dynamic adjustment process, the vehicle does not overlap with the trajectory, which affects the accuracy of AGV control, and in a serious case, the AGV may collide with the opposite AGV. SUMMARY

[0004] In view of the above defects, the purpose of the present application is to provide an AGV steering wheel control method and system based on a permanent magnet motor. When the AGV turns, the steering angle of the steering wheel is problematic, which causes poor AGV control accuracy.

[0005] To achieve this purpose, the application adopts the following technical scheme: an AGV steering wheel control method based on a permanent magnet motor, comprising the following steps:

[0006] Real-time acquisition of the position of the AGV, when the AGV enters a turning point, the travel speed V of the AGV and the tangent angle b of the trajectory are acquired, wherein the travel speed V includes the front wheel speed V1 and the rear wheel speed V2;

[0007] According to the travel speed V of the AGV, the front wheel steering angle θ1 and the rear wheel steering angle θ2 are calculated respectively;

[0008] According to the steering angle θ1, the steering angle θ2 and the tangent angle b of the trajectory, the deviation angle A1 of the front wheel and the deviation angle A2 of the rear wheel are acquired;

[0009] According to the size of the deviation angle A1 and the deviation angle A2, the control mode of the front wheel permanent magnet motor and the control mode of the rear wheel permanent magnet motor are selected respectively.

[0010] Preferably, the step of obtaining the steering angle θ1 and the steering angle θ2 is as follows:

[0011] A cross coordinate system is constructed, with the length direction y axis of the AGV and the width direction x axis of the AGV;

[0012] The speed component V1y of the front wheel speed V1 in the y axis direction and the speed component V2y of the rear wheel speed V2 in the y axis direction are obtained respectively;

[0013] The speed difference of the speed component V1y and the speed component V2y is obtained;

[0014] The steering angle θ1 is calculated according to the speed difference, the speed component V1y of the front wheel speed V1 in the y axis direction and the speed component V1x of the front wheel speed V1 in the x axis direction;

[0015] The steering angle θ2 is calculated according to the speed difference, the speed component V2y of the front wheel speed V2 in the y axis direction and the speed component V2x of the front wheel speed V2 in the x axis direction;

[0016] The formula for obtaining the steering angle θ1 is as follows:

[0017]

[0018] The formula for obtaining the steering angle θ2 is as follows:

[0019]

[0020] Where ΔV is the speed difference, and A is the angle of the center line of the front and rear wheels relative to the central axis of the AGV.

[0021] Preferably, the control mode includes a first control mode and a second control mode;

[0022] When the deviation angle A1 or the deviation angle A2 is less than the angle threshold, the first control mode is adopted;

[0023] When the deviation angle A1 or the deviation angle A2 is greater than the angle threshold, the first control mode is adopted to make the speed of the permanent magnet motor reach the speed threshold, and then the second control mode is adopted.

[0024] Preferably, the first control mode is a current control mode using MTPA to generate corresponding d-axis and q-axis currents, and the corresponding d-axis current and q-axis current are input into the controller to drive the front wheel or the rear wheel to rotate.

[0025] Preferably, the second control mode is:

[0026] Real-time acquisition of given current I of q-axis qRef , given current I qRef is input to a low-pass filter to obtain a first parameter I' qRef ;

[0027] Real-time acquisition of feedback current I of q-axis q , given current I q is input to a low-pass filter to obtain a second parameter I' q ;

[0028] Acquisition of difference E between the first parameter I' qRef and the second parameter I' q , the difference E is taken as an input of a PI controller to obtain a current feedback given item D1;

[0029] According to rated current I n and rated speed ω n , an amplification coefficient Kc of a feedforward given item of field-weakening current is calculated;

[0030] Acquisition of current speed increment of field-weakening, the speed increment is adjusted by the amplification coefficient Kc to obtain a current feedback given item D2;

[0031] The d-axis current I d is obtained by adding the feedback given item D1 and the feedforward given item D2;

[0032] The limit value of q-axis current is obtained by the maximum current and the d-axis current, and the current of q-axis is updated by the limit value of q-axis current;

[0033] The corresponding d-axis current and q-axis current are input to the controller to drive the front wheel or the rear wheel to rotate.

[0034] Preferably, the formula for obtaining the current feedback given item D1 is as follows:

[0035] D1(t) = K p E(t) + K i ∫E(t)dt;

[0036] Wherein t is time, K p and K i are proportional gain coefficient and integral gain coefficient in the PI controller respectively;

[0037] Wherein the formula for obtaining the amplification coefficient Kc is as follows:

[0038]

[0039] Wherein I n is rated current, ωn is a rated speed;

[0040] The acquisition formula of the feedforward given item D2 is specifically as follows:

[0041] D2 = -(S t -S z ) * Kc|; wherein S t is a target speed, and S z is a speed threshold.

[0042] The acquisition formula of the limit value of the q-axis current is as follows:

[0043]

[0044] wherein I max is a maximum output current, and I d is a d-axis current.

[0045] An AGV steering wheel control system based on a permanent magnet motor, using the AGV steering wheel control method based on the permanent magnet motor, comprises a data acquisition module, a steering angle calculation module, a deviation calculation module and a control module.

[0046] The acquisition module is used for acquiring the position of the AGV in real time, and when the AGV enters a turning point, the running speed V of the AGV and the tangent angle b of the track are acquired, wherein the running speed V comprises a front wheel speed V1 and a rear wheel speed V2.

[0047] The steering angle calculation module is used for calculating the front wheel steering angle θ1 and the rear wheel steering angle θ2 according to the running speed V of the AGV.

[0048] The deviation calculation module is used for acquiring the deviation angle A1 of the front wheel and the deviation angle A2 of the rear wheel according to the steering angle θ1, the steering angle θ2 and the tangent angle b of the track.

[0049] The control module is used for selecting the control mode of the front wheel permanent magnet motor and the control mode of the rear wheel permanent magnet motor according to the sizes of the deviation angle A1 and the deviation angle A2.

[0050] Preferably, the steering angle calculation module comprises a coordinate construction submodule, a component acquisition submodule and a calculation submodule.

[0051] The coordinate construction submodule is used for constructing a cross coordinate system, taking the length direction y of the AGV as the x axis and the width direction of the AGV as the x axis.

[0052] The component acquisition submodule is used for acquiring the speed component V1y of the front wheel speed V1 in the y axis direction and the speed component V2y of the rear wheel speed V2 in the y axis direction.

[0053] The calculating sub-module is configured to calculate the steering angle θ1 according to the speed difference value, a speed component V1y of the front wheel speed V1 in the y-axis direction, and a speed component V1x of the front wheel speed V1 in the x-axis direction;

[0054] The steering angle θ2 is calculated according to the speed difference value, a speed component V2y of the front wheel speed V2 in the y-axis direction, and a speed component V2x of the front wheel speed V2 in the x-axis direction.

[0055] Preferably, the control module comprises a first control sub-module and a second control sub-module.

[0056] The first control sub-module is configured to adopt a first control mode when the deviation angle A1 or the deviation angle A2 is less than an angle threshold value.

[0057] The second control sub-module is configured to adopt the first control mode when the deviation angle A1 or the deviation angle A2 is greater than the angle threshold value, and then adopt a second control mode after the speed of the permanent magnet motor reaches a speed threshold value.

[0058] One of the above technical solutions has the following advantages or beneficial effects: the present application realizes high-precision, high-efficiency and high-safety unmanned carrier navigation and control by real-time acquisition of the position, speed and trajectory information of the AGV, and accurate speed adjustment and steering control, and intelligent motor control selection. BRIEF DESCRIPTION OF DRAWINGS

[0059] Fig. 1 is a front wheel and rear wheel speed decomposition schematic diagram of the AGV in one embodiment of the present application.

[0060] Fig. 2 is a flowchart of one embodiment of the method of the present application.

[0061] Fig. 3 is a structural schematic diagram of one embodiment of the system of the present application. DETAILED DESCRIPTION

[0062] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as a limitation of the present application.

[0063] In the description of the embodiments of the present application, the terms "first", "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the embodiments of the present application, the meaning of "multiple" is two or more, unless otherwise specifically limited.

[0064] In addition, the terms "first", "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise stated, the meaning of "multiple" is two or more. For those skilled in the art, the specific meaning of the above terms in the present application can be understood in specific circumstances.

[0065] As shown in Figs. 1-3 A method for controlling the steering wheel of an AGV based on a permanent magnet motor, comprising the following steps:

[0066] Real-time acquisition of the position of the AGV, when the AGV enters the turning point, the running speed V and the tangent angle b of the trajectory of the AGV are acquired, wherein the running speed V includes the front wheel speed V1 and the rear wheel speed V2;

[0067] According to the running speed V of the unmanned carrier, the front wheel steering angle θ1 and the rear wheel steering angle θ2 are calculated respectively;

[0068] According to the steering angle θ1, the steering angle θ2 and the tangent angle b of the trajectory, the deviation angle A1 of the front wheel and the deviation angle A2 of the rear wheel are obtained;

[0069] According to the size of the deviation angle A1 and the deviation angle A2, the control mode of the front wheel permanent magnet motor and the control mode of the rear wheel permanent magnet motor are selected respectively.

[0070] As shown in Fig. 1As shown, the application is applied to a double-rudder AGV, which is provided with a front wheel and a rear wheel, and the front wheel and the rear wheel are controlled by separate permanent magnet motors. When planning a track, a turning point can be marked, and when the AGV travels along the track, it can be determined whether it enters the turning point according to its own position. When the turning point is reached, the current AGV speed and the tangent angle b of the track need to be obtained. Then the steering angle between the front wheel and the rear wheel is obtained, and the steering deviation of the front wheel or the rear wheel is determined according to the comparison between the steering angle and the tangent angle b of the track. When the deviation angle A1 or the deviation angle A2 is not 0, it indicates that the steering of the front wheel or the rear wheel is deviated, so that the AGV cannot effectively turn along the track. At this time, the deviation angle of the front wheel and the rear wheel needs to be compensated, so that the steering angle of the front wheel and the rear wheel is consistent with the tangent angle b of the track. Since the speed needs to be adjusted in a very short time, the permanent magnet motor needs to use a high speed to adjust the steering angle, so that the front wheel and the rear wheel can be quickly adjusted. However, when the deviation angle is too large, the permanent magnet motor will enter the stage of field weakening control, so the corresponding control mode of the permanent magnet motor needs to be selected according to the deviation angle A1 and the deviation angle A2 to realize rapid and smooth steering adjustment.

[0071] The application realizes high-precision, high-efficiency and high-safety unmanned carrier navigation and control by acquiring the position, speed and track information of the AGV in real time, and accurately adjusting the speed and steering control, and intelligently selecting the motor control.

[0072] Preferably, the steps of obtaining the steering angle θ1 and the steering angle θ2 are as follows:

[0073] A cross coordinate system is constructed, with the length direction y axis of the AGV as the x axis and the width direction of the AGV as the y axis.

[0074] The speed component V1y of the front wheel speed V1 in the y axis direction and the speed component V2y of the rear wheel speed V2 in the y axis direction are obtained respectively.

[0075] The speed difference between the speed component V1y and the speed component V2y is obtained.

[0076] The steering angle θ1 is calculated according to the speed difference, the speed component V1y of the front wheel speed V1 in the y axis direction and the speed component V1x of the front wheel speed V1 in the x axis direction.

[0077] The steering angle θ2 is calculated according to the speed difference, the speed component V2y of the front wheel speed V2 in the y axis direction and the speed component V2x of the front wheel speed V2 in the x axis direction.

[0078] The formula for obtaining the turning angle θ1 is as follows:

[0079]

[0080] The formula for obtaining the turning angle θ2 is as follows:

[0081]

[0082] where ΔV is the speed difference, and A is the angle of the center line of the front and rear wheels relative to the AGV central axis.

[0083] By directly measuring and calculating the speed difference between the front and rear wheels in the y-axis (i.e., the AGV forward direction), the dynamic behavior of the AGV during turning can be more accurately evaluated. This calculation method based on actual speed components is more directly reflective of the true situation of turning than traditional methods based on sensors such as gyroscopes or encoders, helping to improve the accuracy of turning control.

[0084] In addition, by compensating the turning angle with the speed difference, system errors caused by mechanical wear, load changes, or external environmental factors (such as uneven ground) can be compensated to some extent, thereby improving the stability and robustness of the entire AGV system.

[0085] Preferably, the control mode includes a first control mode and a second control mode.

[0086] When the deviation angle A1 or the deviation angle A2 is less than the angle threshold, the first control mode is adopted.

[0087] When the deviation angle A1 or the deviation angle A2 is greater than the angle threshold, the first control mode is adopted to make the speed of the permanent magnet motor reach the speed threshold, and then the second control mode is adopted.

[0088] In the control of the permanent magnet motor, the corresponding rotation control of the permanent magnet motor is realized by controlling the input current.

[0089] In order to adjust the deviation angle of the front wheel or the rear wheel by adjusting the rotation of the permanent magnet motor, a large current is generally used for control in order to adjust as soon as possible. At this time, the rotation speed of the permanent magnet motor is gradually increased stably, and the number of rotations of the permanent magnet motor has a linear relationship with the angle of rotation of the front wheel or the rear wheel. Therefore, in the process of gradually increasing the rotation speed stably, when the rotation speed of the permanent magnet motor reaches a rotation speed threshold, the steering angle of the front wheel or the rear wheel is fixed. When the deviation angle A1 or the deviation angle A2 is less than an angle threshold, the permanent magnet motor has not reached the rotation speed threshold in the process of gradually increasing the rotation speed, and the adjustment of the front wheel or the rear wheel can be met, so at this time, the current of the permanent magnet motor can be controlled only by the first control method. When the deviation angle A1 or the deviation angle A2 is greater than the angle threshold, it means that the deviation angle A1 or the deviation angle A2 has not been adjusted to the same as the tangent angle b of the track after the rotation speed of the permanent magnet motor reaches the threshold. However, at this time, the permanent magnet motor has entered the stage of weak magnetic control, so at this time, the second control method can only be replaced to realize the current control of the permanent magnet motor. If the first control method is continued to be used to adjust the current when the permanent magnet motor enters the stage of weak magnetic control, the permanent magnet motor cannot work stably, and at this time, the situation of shaking may occur, which affects the accuracy of angle adjustment.

[0090] Preferably, the first control method is an MTPA current control method for generating corresponding d-axis and q-axis currents, and the corresponding d-axis current and q-axis current are input into a controller to drive the front wheel or the rear wheel to rotate.

[0091] In an embodiment of the present application, the MTPA method is used to generate the current I d to 0, and then the minimum current I q is calculated to generate the largest torque as much as possible, so that the motor can quickly increase the rotation speed, thereby quickly adjusting the steering angle of the front wheel or the rear wheel.

[0092] Since the d-axis current of the motor is always zero in the control method of Id=0, the electromagnetic interference and vibration caused by the change of the d-axis current are reduced, which helps to maintain the stable operation of the permanent magnet motor.

[0093] Preferably, the second control method is:

[0094] The given current I qRef of the q-axis is obtained in real time, and the given current I qRef is input into a low-pass filter to obtain a first parameter I' qRef .

[0095] The feedback current I q of the q-axis is obtained in real time, and the given current I q is input into a low-pass filter to obtain a second parameter I' q;

[0096] By acquiring the given current and feedback current of the q-axis in real time and applying a low-pass filter for processing, more stable and accurate current parameters can be obtained. This method helps to accurately control the operation of the motor and improves stability and reliability.

[0097] acquire a first parameter I' qRef and a difference E between the second parameter I' q , take the difference E as the input of a PI controller, and obtain a current feedback given item D1;

[0098] By calculating the difference E between the given current and the feedback current and taking it as the input of a PI controller, a feedback given item D1 for adjusting the current can be obtained. The PI controller can effectively reduce errors and improve the accuracy of current control.

[0099] According to the rated current I n and the rated speed ω n , calculate the amplification coefficient Kc of the feedforward given item of the field weakening current; the determination of the calculated amplification coefficient Kc is based on the rated current and the rated speed of the motor, and the speed increment is adjusted through the amplification coefficient Kc, which can ensure the motor to run in a high-efficiency and stable state.

[0100] Obtain the speed increment of the current field weakening, adjust the speed increment through the amplification coefficient Kc, and obtain the current feedback given item D2;

[0101] Add the feedback given item D1 and the feedforward given item D2 to obtain the d-axis current I d ;

[0102] And obtain the limit value of the q-axis current through the maximum current and the d-axis current, and update the current q-axis current with the limit value of the q-axis current;

[0103] Input the corresponding d-axis current and q-axis current into the controller to drive the front wheel or rear wheel to rotate.

[0104] Selecting the maximum limit value of the q-axis current as the input of the q-axis current can ensure the stable operation of the permanent magnet motor while driving the permanent magnet motor to rotate at the fastest speed, and speeding up the adjustment speed of the front wheel or rear wheel steering angle.

[0105] Preferably, the formula for obtaining the current feedback given item D1 is as follows:

[0106] D1(t)=K p E(t)+K i ∫E(t)dt;

[0107] Where t is time, K p and Ki respectively are proportional gain coefficient and integral gain coefficient in PI controller;

[0108] The acquisition formula for obtaining the amplification coefficient Kc is specifically as follows:

[0109]

[0110] wherein I n is rated current, ω n is rated rotating speed;

[0111] The acquisition formula for obtaining the feedforward given item D2 is specifically as follows:

[0112] D2 = -(S t -S z ) * Kc |; wherein S t is target rotating speed, and S z is rotating speed threshold.

[0113] The acquisition formula for the limiting value of the q-axis current is as follows:

[0114]

[0115] wherein I max is maximum output current, I d is d-axis current.

[0116] An AGV steering wheel control system based on a permanent magnet motor, using the AGV steering wheel control method based on the permanent magnet motor, comprising a data acquisition module, a steering angle calculation module, a deviation calculation module and a control module;

[0117] The acquisition module is used for acquiring the position of the AGV in real time, and when the AGV enters a turning point, the traveling speed V of the AGV and the tangent angle b of the track are acquired, wherein the traveling speed V includes the front wheel speed V1 and the rear wheel speed V2.

[0118] The steering angle calculation module is used for calculating the front wheel steering angle θ1 and the rear wheel steering angle θ2 according to the traveling speed V of the unmanned carrier.

[0119] The deviation calculation module is used for obtaining the deviation angle A1 of the front wheel and the deviation angle A2 of the rear wheel according to the steering angle θ1, the steering angle θ2 and the tangent angle b of the track.

[0120] The control module is used for selecting the control mode of the front wheel permanent magnet motor and the control mode of the rear wheel permanent magnet motor according to the size of the deviation angle A1 and the deviation angle A2.

[0121] Preferably, the turning angle calculation module comprises a coordinate construction submodule, a component acquisition submodule and a calculation submodule.

[0122] The coordinate construction submodule is configured to construct a cross coordinate system, with a length direction y axis of the AGV and a width direction x axis of the AGV.

[0123] The component acquisition submodule is configured to acquire a speed component V1y of the front wheel speed V1 in the y axis direction and a speed component V2y of the rear wheel speed V2 in the y axis direction.

[0124] The calculation submodule is configured to calculate the turning angle θ1 according to the speed difference, the speed component V1y of the front wheel speed V1 in the y axis direction and a speed component V1x of the front wheel speed V1 in the x axis direction.

[0125] The calculation submodule is configured to calculate the turning angle θ2 according to the speed difference, the speed component V2y of the rear wheel speed V2 in the y axis direction and a speed component V2x of the rear wheel speed V2 in the x axis direction.

[0126] Preferably, the control module comprises a first control submodule and a second control submodule.

[0127] The first control submodule is configured to adopt the first control mode when the deviation angle A1 or the deviation angle A2 is less than the angle threshold value.

[0128] The second control submodule is configured to adopt the second control mode after the speed of the permanent magnet motor reaches the speed threshold value when the deviation angle A1 or the deviation angle A2 is greater than the angle threshold value.

[0129] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "exemplary embodiment", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the exemplary description of the above terms does not necessarily mean the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0130] Although the embodiments of the present application have been shown and described above, it should be understood that the above embodiments are exemplary and cannot be understood as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

Claims

1. A method for controlling the steering wheel of an AGV based on a permanent magnet motor, characterized in that, Includes the following steps: The position of the AGV is obtained in real time. When the AGV enters the turning point, the traveling speed V and the tangent angle b of the trajectory are obtained. The traveling speed V includes the front wheel speed V1 and the rear wheel speed V2. The front wheel steering angles were calculated based on the travel speed V of the automated guided vehicle. Steering angle with rear wheels ; According to the steering angle Steering angle And the tangent angle b of the trajectory, to obtain the deviation angle A1 of the front wheel and the deviation angle A2 of the rear wheel; Based on the magnitudes of deviation angles A1 and A2, select the control methods for the front wheel permanent magnet motor and the rear wheel permanent magnet motor, respectively. Among them, the steering angle is obtained With steering angle The steps are as follows: Construct a cross coordinate system with the length direction of the AGV as the y-axis and the width direction of the AGV as the x-axis; Obtain the velocity components V1y of the front wheel velocity V1 in the y-axis direction and V2y of the rear wheel velocity V2 in the y-axis direction, respectively; Obtain the velocity difference between velocity component V1y and velocity component V2y; The steering angle is calculated based on the speed difference, the velocity component V1y of the front wheel speed V1 in the y-axis direction, and the velocity component V1x of the front wheel speed V1 in the x-axis direction. ; The steering angle is calculated based on the speed difference, the velocity component V2y of the front wheel speed V2 in the y-axis direction, and the velocity component V2x of the front wheel speed V2 in the x-axis direction. ; Among them, the steering angle The formula for obtaining it is as follows: ； Among them, the steering angle The formula for obtaining it is as follows: ； in The speed difference is A, which is the angle between the line connecting the centers of the front and rear wheels and the centerline of the AGV. The control method includes a first control method and a second control method; When the deviation angle A1 or deviation angle A2 is less than the angle threshold, the first control mode is adopted; When the deviation angle A1 or deviation angle A2 is greater than the angle threshold, the first control method is used to make the speed of the permanent magnet motor reach the speed threshold, and then the second control method is used. The second control method is: Real-time acquisition of the given current along the q-axis , give current The input is fed into a low-pass filter to obtain the first parameter. ; Real-time acquisition of q-axis feedback current , give current The input is fed into a low-pass filter to obtain the second parameter. ; Get the first parameter With the second parameter The difference E is used as the input of the PI controller to obtain the current feedback setpoint D1; According to the rated current and rated speed Calculate the amplification factor Kc of the feedforward reference term for the field weakening current; obtain the rotational speed increment of the current field weakening, and adjust the rotational speed increment through the amplification factor Kc to obtain the current feedback reference term D2; The d-axis current is obtained by adding the feedback reference D1 and the feedforward reference D2. ; The limit value of the q-axis current is obtained by using the maximum current and the d-axis current, and the current q-axis current is updated with the limit value of the q-axis current. The corresponding d-axis current and q-axis current are input into the controller to drive the front or rear wheels to rotate.

2. The AGV steering wheel control method based on a permanent magnet motor according to claim 1, characterized in that, The first control method is to use the MTPA current control method to generate the corresponding d-axis and q-axis currents, and input the corresponding d-axis currents and q-axis currents into the controller to drive the front wheel or rear wheel to rotate.

3. The AGV steering wheel control method based on a permanent magnet motor according to claim 1, characterized in that, The formula for obtaining the current feedback reference term D1 is as follows: ； Where t is time, and These are the proportional gain coefficient and integral gain coefficient in the PI controller, respectively. The specific formula for obtaining the magnification factor Kc is as follows: ， in For rated current, Rated speed; The specific formula for obtaining the feedforward given term D2 is as follows: ;in For the target speed, This is the rotational speed threshold; The formula for obtaining the q-axis current limit value is as follows: ； in For maximum output current, The current is along the d-axis.

4. An AGV steering wheel control system based on a permanent magnet motor, characterized in that, The AGV steering wheel control method based on a permanent magnet motor according to any one of claims 1 to 3 includes a data acquisition module, a steering angle calculation module, a deviation calculation module, and a control module; The acquisition module is used to acquire the position of the AGV in real time. When the AGV enters the turning point, it acquires the AGV's traveling speed V and the tangent angle b of the trajectory, wherein the traveling speed V includes the front wheel speed V1 and the rear wheel speed V2. The steering angle calculation module is used to calculate the front wheel steering angle based on the travel speed V of the unmanned transport vehicle. Steering angle with rear wheels ; The deviation calculation module is used to calculate based on the steering angle. Steering angle And the tangent angle b of the trajectory, to obtain the deviation angle A1 of the front wheel and the deviation angle A2 of the rear wheel; The control module is used to select the control mode of the front wheel permanent magnet motor and the control mode of the rear wheel permanent magnet motor according to the magnitude of the deviation angles A1 and A2, respectively.

5. The AGV steering wheel control system based on a permanent magnet motor according to claim 4, characterized in that, The steering angle calculation module includes a coordinate construction submodule, a component acquisition submodule, and a calculation submodule; The coordinate construction submodule is used to construct a cross coordinate system with the length direction of the AGV as the y-axis and the width direction of the AGV as the x-axis. The component acquisition submodule is used to acquire the velocity component V1y of the front wheel speed V1 in the y-axis direction and the velocity component V2y of the rear wheel speed V2 in the y-axis direction, respectively. The calculation submodule is used to calculate the steering angle based on the speed difference, the velocity component V1y of the front wheel speed V1 in the y-axis direction, and the velocity component V1x of the front wheel speed V1 in the x-axis direction. ; The steering angle is calculated based on the speed difference, the velocity component V2y of the front wheel speed V2 in the y-axis direction, and the velocity component V2x of the front wheel speed V2 in the x-axis direction. .

6. The AGV steering wheel control system based on a permanent magnet motor according to claim 4, characterized in that, The control module includes a first control submodule and a second control submodule; The first control submodule is used to employ a first control method when the deviation angle A1 or deviation angle A2 is less than the angle threshold. The second control submodule is used to use the first control method to make the speed of the permanent magnet motor reach the speed threshold when the deviation angle A1 or deviation angle A2 is greater than the angle threshold, and then use the second control method.

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