Presser foot pressure control method, system and device and electronic buttonholing machine

Abstract

The invention discloses a presser foot pressure control method, system and device and an electronic buttonholing machine, and relates to the technical field of electronic buttonholing machines.The presser foot pressure control method comprises the steps that a motor controls a presser foot to press downwards, and when the presser foot presses downwards to the fabric position, the rotation angle of the motor is obtained; obtaining the fabric thickness according to the rotation angle; according to the thickness of the fabric, the driving current of the presser foot pressure required by the thickness of the fabric is calculated; and the current of the motor is regulated to drive current, so that the pressure of the presser foot can adapt to the fabric thickness. According to the presser foot pressure control method, cloth pressing pressure self-adaption of fabrics with different thicknesses is achieved, particularly when thick fabrics are replaced, pressure loss caused by the structure of the presser foot can be compensated, and therefore the pressure of the presser foot is adjusted to the cloth pressing stability capable of meeting the fabric thickness, and the fabric pressing stability is improved. The problem of unstable cloth pressing caused by pressure change of the presser foot due to fabric thickness difference is solved, and the adaptability of the electronic buttonholing machine to the fabric thickness change is greatly improved.

Description

Technical Field

[0001] This application relates to the technical field of electronic lockhole machines, and particularly to a presser foot pressure control method, a presser foot pressure control system, a presser foot pressure control device, and an electronic lockhole machine. Background Art

[0002] In the existing system, the main method for the presser foot lifting and lowering mechanism of an electronic lockhole machine is: a closed-loop stepper motor drives and controls the lifting and lowering action of the lifting and pressing mechanism to press the presser foot against the fabric.

[0003] Specifically, as Figure 1 and Figure 2 shown, the rotation of the motor shaft drives the pull rod 1, thereby causing the lifting swing plate 2 to rotate. One end of the lifting swing plate 2 is fixedly connected to the slider 3, that is, the rotation of the lifting swing plate 2 drives the slider 3 to move up and down. The slider 3 is embedded in the slider groove of the presser foot support block 4, and the slider groove of the presser foot support block 4 is fixed on the vertically arranged presser foot shaft. In this way, the up and down lifting of the presser foot is realized with the up and down movement of the slider 3.

[0004] However, in the process of implementing the present invention, the inventors found that there are at least the following problems in the prior art:

[0005] With the above control method, as the thickness of the pressed material increases, the lifting swing plate will deflect upward, and the decomposition of the motor force changes, resulting in a decrease in the downward pressure, so that it is impossible to keep the pressing pressure of the thick and thin materials constant. Especially for thin and thick materials, it is easy to cause insufficient pressing of the material, and it is impossible to adapt to both thin and thick materials at the same time when changing styles and materials. During the sewing process, slippage, insufficient pressing, etc. occur. In the light case, it affects the flatness of the lockhole and the beauty of the stitch. In the heavy case, it causes cloth swallowing, cloth jamming, and even thread breakage, needle breakage, mechanical failure, and electronic control alarm, etc., seriously affecting the use of customers and reducing the fabric adaptability.

[0006] Therefore, it is necessary for those skilled in the art to timely provide a presser foot pressure control method that can adapt to both thin and thick materials at the same time. Summary of the Invention

[0007] The purpose of this application is to provide a presser foot pressure control method, a presser foot pressure control system, a presser foot pressure control device, and an electronic lockhole machine, which can meet the pressing stability of different fabric thicknesses, thereby solving the problem of unstable pressing caused by the change of presser foot pressure due to the change of fabric thickness.

[0008] To achieve the above purpose, this application provides a presser foot pressure control method, which is applied to a presser foot pressure control device. The presser foot pressure control device includes a presser foot and a motor for controlling the lifting and lowering of the presser foot. The presser foot pressure control method includes:

[0009] Controlling the presser foot to press down by the motor, and when the presser foot presses down to the fabric position, obtaining the rotation angle of the motor;

[0010] Obtain the fabric thickness based on the rotation angle;

[0011] Calculate the drive current required for the presser foot pressure according to the fabric thickness;

[0012] Adjust the current of the motor to the drive current so that the presser foot pressure can adapt to the fabric thickness.

[0013] In some embodiments, before the step of obtaining the rotation angle of the motor, it further includes:

[0014] Change the current of the motor to the initial current;

[0015] The step of calculating the drive current required for the presser foot pressure according to the fabric thickness includes:

[0016] Determine the interval where the fabric thickness is located;

[0017] Obtain the compensation current required for the fabric thickness according to the interval where the fabric thickness is located;

[0018] Calculate the drive current according to the compensation current and the initial current.

[0019] In some embodiments, the step of obtaining the compensation current required for the fabric thickness according to the interval where the fabric thickness is located includes:

[0020] Obtain a preset relation table, which includes the relationship between the compensation current, the fabric thickness, and the pressure setting value, and the pressure setting value is the same as the presser foot pressure required for the fabric thickness;

[0021] Obtain the compensation current required for the fabric thickness according to the preset relation table.

[0022] In some embodiments, the step of obtaining the fabric thickness based on the rotation angle includes:

[0023] Judge whether the rotation angle is within the permitted interval;

[0024] If the rotation angle is not within the permitted interval, alarm and return to the step of controlling the presser foot to press down by the motor again;

[0025] If the rotation angle is within the permitted interval, calculate the fabric thickness according to L = 11.5 - 23sin(30 - a + 50), where L is the fabric thickness and a is the rotation angle.

[0026] In some embodiments, after the step of controlling the presser foot to press down by the motor, it further includes:

[0027] During the process of pressing the presser foot down to the fabric position, obtain the preset detection value of the presser foot;

[0028] Determine whether the preset detection value reaches the preset condition;

[0029] If the preset detection value does not reach the preset condition, return to the step of controlling the presser foot to press down by the motor;

[0030] If the preset detection value reaches the preset condition, it is determined that the presser foot presses down to the fabric position.

[0031] In some embodiments, the preset detection value includes a detection force value. The step of obtaining the preset detection value of the presser foot includes:

[0032] Detect the force on the presser foot to obtain the detection force value;

[0033] The step of determining whether the preset detection value reaches the preset condition includes:

[0034] Determine whether the detection force value reaches the set detection force threshold; or

[0035] Determine whether the detection force value is within the set detection force value range.

[0036] In some embodiments, the step of controlling the presser foot to press down by the motor includes:

[0037] Obtain the category of the fabric and determine the output current of the motor according to the category of the fabric;

[0038] Control the presser foot to press down with the output current.

[0039] This application also provides a presser foot pressure control system, which adopts the presser foot pressure control method of any one of the above, and includes:

[0040] A motor rotation angle acquisition module, which is used to control the presser foot to press down by the motor and acquire the rotation angle of the motor when the presser foot presses down to the fabric position;

[0041] A fabric thickness acquisition module, which is used to obtain the fabric thickness according to the rotation angle;

[0042] A calculation module, which is used to calculate the drive current required for the presser foot pressure according to the fabric thickness;

[0043] A regulation module, which is used to regulate the current of the motor to the drive current so that the presser foot pressure can adapt to the fabric thickness.

[0044] This application also provides a presser foot pressure control device, including:

[0045] A memory, which is used to store a computer program;

[0046] A processor, which is used to implement the steps of the presser foot pressure control method of any one of the above when executing the computer program.

[0047] The present application also provides an electronic keyhole machine, including the presser foot pressure control device described above.

[0048] Compared with the above background art, the presser foot pressure control method provided by the embodiments of the present application is applied to a presser foot pressure control device. The presser foot pressure control device includes a presser foot and a motor for controlling the lifting and lowering of the presser foot. It can be seen that the presser foot pressure control method provided by the embodiments of the present application automatically detects the rotation angle of the motor when the presser foot presses down to the fabric position, calculates the fabric thickness based on the rotation angle of the motor, then calculates the drive current required for the presser foot pressure corresponding to the fabric thickness, and finally adjusts the current of the motor to the drive current, so that the presser foot pressure can adapt to the fabric thickness. Compared with the traditional control method, the presser foot pressure control method provided by the embodiments of the present application realizes the self - adaptation of the pressing pressure for fabrics of different thicknesses, makes the presser foot pressure stable, can adapt to both thin and thick fabrics at the same time. Especially when changing to thick fabrics, it can compensate for the pressure loss caused by the structure of the presser foot itself, thereby adjusting the presser foot pressure to meet the pressing stability of the fabric thickness, solving the problem of unstable fabric pressing caused by the change of the presser foot pressure due to the difference in fabric thickness, and greatly improving the adaptability of the electronic keyhole machine to the change of fabric thickness. Description of the Drawings

[0049] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings described below are only the embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the provided drawings.

[0050] Figure 1 It is the front view of the presser foot lifting mechanism of the electronic keyhole machine in the prior art;

[0051] Figure 2 It is the side view of the presser foot lifting mechanism of the electronic keyhole machine in the prior art;

[0052] Figure 3 It is the flow chart of the presser foot pressure control method in the embodiments of the present application;

[0053] Figure 4 It is the structural block diagram of the presser foot pressure control system in the embodiments of the present application.

[0054] Wherein:

[0055] 1 - pull rod, 2 - lifting swing plate, 3 - slider, 4 - presser foot support block;

[0056] 10 - motor rotation angle acquisition module, 20 - fabric thickness acquisition module, 30 - calculation module, 40 - regulation module. Detailed Embodiments

[0057] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the protection scope of the present application.

[0058] In order to enable those skilled in the art of this technology to better understand the solution of the present application, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0059] Please refer to Figure 1 , the presser foot pressure control method provided by the embodiments of the present application is applied to a presser foot pressure control device. The presser foot pressure control device includes a presser foot and a motor for controlling the lifting and lowering of the presser foot. The presser foot pressure control method includes:

[0060] S1: Control the presser foot to press down through the motor, and when the presser foot presses down to the fabric position, obtain the rotation angle of the motor;

[0061] S2: Obtain the fabric thickness according to the rotation angle;

[0062] S3: Calculate the drive current required for the presser foot pressure according to the fabric thickness;

[0063] S4: Adjust the current of the motor to the drive current so that the presser foot pressure can adapt to the fabric thickness.

[0064] It can be seen that the presser foot pressure control method provided by the embodiments of the present application automatically detects the rotation angle of the motor when the presser foot presses down to the fabric position, calculates the fabric thickness according to the rotation angle of the motor, then calculates the drive current required for the presser foot pressure according to the fabric thickness, and finally adjusts the current of the motor to the drive current so that the presser foot pressure can adapt to the fabric thickness.

[0065] Compared with the traditional control, the presser foot pressure control method provided by the embodiments of the present application realizes the self - adaptation of the pressing pressure for fabrics of different thicknesses, makes the presser foot pressure stable, can adapt to both thin and thick fabrics at the same time. Especially when changing to thick fabrics, it can compensate for the pressure loss caused by the structure of the presser foot itself, so as to adjust the presser foot pressure to meet the pressing stability of the fabric thickness, solves the problem of unstable fabric pressing caused by the change of the presser foot pressure due to the difference in fabric thickness, and greatly improves the adaptability of the electronic buttonholing machine to the change of fabric thickness.

[0066] In some embodiments, before the step of obtaining the rotation angle of the motor, it further includes:

[0067] Change the current of the motor to the initial current;

[0068] The steps of calculating the drive current of the presser foot pressure required for the fabric thickness include:

[0069] Determine the interval where the fabric thickness is located;

[0070] Obtain the compensation current required for the fabric thickness according to the interval where the fabric thickness is located;

[0071] Calculate the drive current based on the compensation current and the initial current.

[0072] It should be noted that the value of the above initial current is generally 0.5A. When the presser foot presses down to the fabric position, the presser foot stops pressing down and automatically changes the motor current to the initial current, that is, 0.5A, and then obtains the rotation angle of the motor.

[0073] It can be understood that the drive current required for the fabric thickness is obtained by adding the compensation current of the fabric thickness L to the initial current, and then the current of the motor is adjusted by the electronic control to the drive current to realize the self - adaptation of the presser foot pressure, and the next sewing action is executed.

[0074] In some embodiments, the steps of obtaining the compensation current required for the fabric thickness according to the interval where the fabric thickness is located include:

[0075] Obtain a preset relation table, which includes the relationship between the compensation current, the fabric thickness, and the pressure setting value. Among them, the pressure setting value is the same as the presser foot pressure required for the fabric thickness;

[0076] Obtain the compensation current required for the fabric thickness according to the preset relation table.

[0077] It should be noted that the above preset relation table is shown in Table 1 below. Through the fabric thickness L and the pressure setting value (this value is the presser foot pressure value required when sewing the fabric thickness L), the compensation current required for the fabric thickness L (also called the pressure current compensation value) can be obtained:

[0078] Table 1

[0079]

[0080] In addition, in order to adapt to the pressing material adaptation of the presser foot in the 0 - 8mm thickness range, the origin of the presser foot is lifted by re - defining the origin of the mechanical lifting and pressing gear meshing and the adjustment of the electronic control. The following specifically describes the control flow of the presser foot pressure control method provided by the embodiments of the present application (the motor that controls the presser foot to press down is controlled by the controller):

[0081] When the controller receives the signal of the presser foot pressing down (i.e., stepping on the foot pedal switch), it outputs a stable current of a certain magnitude to drive the closed-loop stepper motor to work. Through the corresponding linkage mechanism, the presser foot is pressed down. When the controller outputs a current of 2A to press down the presser foot, and the fabric is pressed down by the presser foot to reach the driving load value (system preset value) of the motor or the preset detection value of the presser foot, feedback information is sent to the controller to stop the presser foot from pressing down, and the output current of the motor is automatically adjusted to 0.5A. Then, the encoder identifies and determines the rotation angle of the motor during this process, and calculates the corresponding fabric thickness L. When 0mm ≤ L ≤ Pmm, the driving current required for this fabric thickness is obtained by adding the compensation current of this fabric thickness L to the initial current (0.5A). Then, the controller adjusts the current of the motor to achieve the self-adaptation of the presser foot pressure and executes the next sewing action. When am m ≤ L ≤ Qmm, the action of the motor pressing down to find the origin is cancelled to avoid the situation of the motor lifting and pressing error caused by too thick sewing material. Then, the driving current required for this fabric thickness is obtained by adding the compensation current of this fabric thickness L to the initial current (0.5A). Then, the controller adjusts the current to achieve the self-adaptation of the presser foot pressure and executes the next sewing action.

[0082] Of course, according to actual needs, the values of P and Q can be set as required, and this embodiment does not make specific limitations on this.

[0083] In some embodiments, the step of obtaining the fabric thickness according to the rotation angle includes:

[0084] Judge whether the rotation angle is within the permitted range;

[0085] If the rotation angle is not within the permitted range, an alarm is given, and the process returns to the step of controlling the presser foot to press down by the motor;

[0086] If the rotation angle is within the permitted range, the fabric thickness is calculated according to L = 11.5 - 23sin(30 - a + 50), where L is the fabric thickness and a is the rotation angle.

[0087] It should be noted that the above permitted range can be 0 ≤ a ≤ 70°.

[0088] That is to say, when the value of the rotation angle a is within the permitted range [0, 70°], the fabric thickness L is calculated according to the formula L = 11.5 - 23sin(30 - a + 50). Otherwise, an alarm is given, and the process returns to the step of controlling the presser foot to press down by the motor until the value of the rotation angle a is within the permitted range [0, 70°], and then the calculation of the fabric thickness L can be carried out.

[0089] In some embodiments, after the step of controlling the presser foot to press down by the motor, it further includes:

[0090] During the process of the presser foot pressing down to the fabric position, obtain the preset detection value of the presser foot;

[0091] Determine whether a preset detection value reaches a preset condition;

[0092] If the preset detection value does not reach the preset condition, return to the step of controlling the presser foot to press down by the motor;

[0093] If the preset detection value reaches the preset condition, it is determined that the presser foot presses down to the fabric position.

[0094] It should be noted that the preset detection value used to represent that the presser foot presses down to the fabric position can be a force value used to represent the force on the presser foot, a deformation value used to represent the force on the presser foot, a current value used to represent the force on the presser foot, or other values used to represent the force on the presser foot. This application does not make special limitations on this.

[0095] In some embodiments, the preset detection value includes a detected force value. The step of obtaining the preset detection value of the presser foot includes:

[0096] Detect the force on the presser foot to obtain a detected force value;

[0097] The step of determining whether the preset detection value reaches the preset condition includes:

[0098] Determine whether the detected force value reaches a set detected force threshold; or

[0099] Determine whether the detected force value is within a set detected force value range.

[0100] Specifically, the detected force value can be a detected force value detected by a force sensor installed on the presser foot. For example, the force sensor is installed on the presser foot. The force sensor can adopt a resistance strain type sensor. Of course, other sensors can also be adopted. The resistance strain type sensor is a force sensor that can convert the deformation amount caused by the force on the presser foot into a corresponding resistance value. The resistance strain type sensor is electrically connected to the control system of the electronic keyholing machine. For example, the resistance strain type sensor includes a strain gauge and a signal processing circuit. The signal processing circuit is used to process the signal sensed by the strain gauge.

[0101] It should be noted that when the detected force value reaches the set detection force threshold, it is determined that the presser foot has pressed down to the fabric position. The set detection force threshold is the threshold value that the detected force value will reach when the presser foot contacts the fabric. Of course, it can also be determined that the presser foot has pressed down to the fabric position when the detected force value is within the set detection force value range, and the set detection force threshold can be within the set detection force value range. For example, the set detection force threshold can be the median value of the set detection force value range. Or, the set detection force value range can also be other value ranges that include the set detection force threshold. The set detection force threshold can be calculated according to the motion model of the presser foot contacting the fabric, or the magnitude of the set detection force threshold can be determined through the analysis of the experimental results of the presser foot contacting the fabric.

[0102] In some embodiments, the step of controlling the downward pressing of the presser foot by the motor includes:

[0103] Obtain the category of the fabric and determine the output current of the motor according to the category of the fabric;

[0104] Control the downward pressing of the presser foot with the output current.

[0105] It can be understood that taking thin materials and thick materials as examples, the thicknesses of different categories of fabrics are different. Therefore, for different categories of fabrics, the output current of the motor can be determined according to the fabric of this category.

[0106] It should be emphasized that the structure of the electronic keyhole machine adopted in the embodiments of the present application will cause the downward pressure of the presser foot to become smaller as the thickness of the pressed material increases, and it is impossible to keep the pressing pressure of the thin and thick materials constant. Therefore, for thin and thick materials, it is easy to cause insufficient pressing of the material, and it is impossible to adapt to both thin and thick materials at the same time when changing styles and materials. In this way, the output current of the motor is determined according to the corresponding category of fabric, so that the motor outputs a constant current, keeps the torque output stable, and meets the pressing stability of the corresponding category of fabric.

[0107] Adopting the above-mentioned presser foot pressure control method can bring the following beneficial effects:

[0108] First, the lifting and lowering actions of the presser foot are all realized by the closed-loop motor drive. On the one hand, the motor drives the lifting and pressing actions, and the corresponding beat is improved and optimized on the existing basis, which is more in line with the user scenario requirements of the post-stage dedicated machine market. On the other hand, the motor adopts a constant current output, the torque output is stable, and in terms of control, the required drive current is smaller, reducing the demand for drive current, making the control more stable, improving the life and performance of the motor, and making the motor more durable.

[0109] Second, by adopting the control method of the present application, it is possible to achieve the adaptive and stable output of the presser foot pressure for different fabric thicknesses, conveniently improve the pressing stability, so as to meet customer requirements, especially for the improvement of the pressing performance in the two extreme scenarios of thin fabrics and thick fabrics. Specifically: for thin fabrics and thick fabrics, the fabric is pressed more tightly during the sewing process, the stitch appearance is better, and the probabilities of fabric swallowing, fabric jamming, thread breakage, and needle breakage are reduced, resulting in a significant improvement in fabric adaptability; for thick fabrics (fluffy fabrics, cotton-padded fabrics, etc.), the fabric is pressed more tightly during the sewing process, and the sewing effect is better, which can effectively reduce the failure rates such as mechanical jamming of the scissors advancing and retreating and the electric control alarm fault code, resulting in a significant improvement in fabric adaptability.

[0110] Third, when switching between thick and thin fabrics, there will be no phenomenon of change in the presser foot pressure caused by the fabric thickness, avoiding the situation of unstable fabric pressing, and there is no need to adjust the machine, so the experience of the end user is better.

[0111] Fourth, without an additional sensor, the present application presets and calculates the pressing thickness when the presser foot presses the fabric through a built-in formula in the program, and then compensates the current in different pressing thickness ranges to achieve the stability of the presser foot pressure for different thicknesses.

[0112] Fifth, by adopting the control method of the present application, it can adapt to a pressing thickness of 0-8 mm, and the electric control will not have problems such as alarm and crashing.

[0113] Please refer to Figure 2 together. A presser foot pressure control system provided by the present application adopts the presser foot pressure control method described in the above specific embodiments, including:

[0114] A motor rotation angle acquisition module 10, which is used to control the presser foot to press down through the motor and acquire the rotation angle of the motor when the presser foot presses down to the fabric position;

[0115] A fabric thickness acquisition module 20, which is used to obtain the fabric thickness according to the rotation angle;

[0116] A calculation module 30, which is used to calculate the drive current required for the presser foot pressure according to the fabric thickness;

[0117] A regulation module 40, which is used to regulate the current of the motor to the drive current so that the presser foot pressure can adapt to the fabric thickness.

[0118] A presser foot pressure control device provided by the present application includes:

[0119] A memory, which is used to store a computer program;

[0120] A processor, which is used to implement the steps of the presser foot pressure control method described in the above specific embodiments when executing the computer program.

[0121] An electronic keyhole machine provided by the present application includes the presser foot pressure control device described in the above specific embodiments. Other parts of the electronic keyhole machine can refer to the prior art and will not be elaborated herein.

[0122] It should be noted that in this specification, relational terms such as first and second are only used to distinguish one entity from several other entities, and do not necessarily require or imply any actual relationship or order between these entities.

[0123] The above has introduced in detail the presser foot pressure control method, the presser foot pressure control system, the presser foot pressure control device and the electronic keyhole machine provided by the present application. Specific examples are used in this article to elaborate on the principle and implementation manner of the present application. The description of the above embodiments is only used to help understand the solution and its core idea of the present application. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. A presser foot pressure control method, characterized in that, Applied to a presser foot pressure control device, the presser foot pressure control device includes a presser foot and a motor for controlling the lifting and pressing of the presser foot. The presser foot pressure control method includes: Controlling the downward pressing of the presser foot by the motor, and when the presser foot presses down to the fabric position, obtaining the rotation angle of the motor; Obtaining the fabric thickness according to the rotation angle; Calculating the drive current required for the presser foot pressure corresponding to the fabric thickness according to the fabric thickness; Adjusting the current of the motor to the drive current so that the presser foot pressure can adapt to the fabric thickness.

2. The presser foot pressure control method according to claim 1, characterized in that, Before the step of obtaining the rotation angle of the motor, it further includes: Changing the current of the motor to the initial current; The step of calculating the drive current required for the presser foot pressure corresponding to the fabric thickness according to the fabric thickness includes: Determining the interval where the fabric thickness is located; Obtaining the compensation current required for the fabric thickness according to the interval where the fabric thickness is located; Calculating the drive current according to the compensation current and the initial current.

3. The presser foot pressure control method according to claim 2, characterized in that, The step of obtaining the compensation current required for the fabric thickness according to the interval where the fabric thickness is located includes: Obtaining a preset relation table, which includes the relationship between the compensation current, the fabric thickness and the pressure setting value, and the pressure setting value is the same as the presser foot pressure required for the fabric thickness; Obtaining the compensation current required for the fabric thickness according to the preset relation table.

4. The presser foot pressure control method according to claim 1, wherein, The step of obtaining the fabric thickness according to the rotation angle includes: Judging whether the rotation angle is within the permitted interval; If the rotation angle is not within the permitted interval, then alarm and return to the step of controlling the downward pressing of the presser foot by the motor; If the rotation angle is within the permitted interval, then calculate the fabric thickness according to L = 11.5 - 23sin(30 - a + 50), where L is the fabric thickness and a is the rotation angle.

5. The presser foot pressure control method according to claim 1, characterized in that, After the step of controlling the downward pressing of the presser foot by the motor, it further includes: During the process of the presser foot pressing down to the fabric position, obtaining a preset detection value of the presser foot; Judging whether the preset detection value reaches a preset condition; If the preset detection value does not reach the preset condition, then return to the step of controlling the downward pressing of the presser foot by the motor; If the preset detection value reaches the preset condition, then determine that the presser foot has pressed down to the fabric position.

6. The presser foot pressure control method according to claim 5, wherein, The preset detection value includes a detected force value. The step of obtaining the preset detection value of the presser foot includes: Detecting the force on the presser foot to obtain the detected force value; The step of judging whether the preset detection value reaches a preset condition includes: Judging whether the detected force value reaches a set detected force threshold; or Judging whether the detected force value is within a set detected force value range.

7. The presser foot pressure control method according to any one of claims 1-6, characterized in that, The step of controlling the downward pressing of the presser foot by the motor includes: Obtaining the type of the fabric and determining the output current of the motor according to the type of the fabric; Controlling the downward pressing of the presser foot with the output current.

8. A presser foot pressure control system, adopting the presser foot pressure control method according to any one of claims 1-7, characterized in that, Includes: A motor rotation angle acquisition module, configured to control the downward pressing of the presser foot by the motor, and when the presser foot presses down to the fabric position, obtain the rotation angle of the motor; A fabric thickness acquisition module, configured to obtain the fabric thickness according to the rotation angle; A calculation module, configured to calculate a drive current required for the presser foot pressure according to the fabric thickness; A regulation module, configured to regulate the current of the motor to the drive current, so that the presser foot pressure can adapt to the fabric thickness.

9. A presser foot pressure control device, characterized in that, Comprising: A memory, configured to store a computer program; A processor, configured to implement the steps of the presser foot pressure control method according to any one of claims 1-7 when executing the computer program.

10. An electronic keyhole machine, characterized in that, Comprising the presser foot pressure control device according to claim 9.

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