Method for controlling sewing machine to sew cloth at low speed without throwing thread

Abstract

The invention relates to a low-speed non-throwing control method for sewing cloth by a sewing machine, a needle and a take-up lever of the sewing machine are driven by a main shaft, and the method comprises the following steps: S1, determining a non-throwing safe aperture D1; determining the time tD required from the time when the machine needle upwards leaves the cloth to the time when the needle eye hole shrinks to the non-throwing thread safe aperture D1; s2, recording AT / T = omega n; in one operation cycle, determining an angle A1 corresponding to the main shaft when a machine needle upwards leaves the cloth, and determining an angle A2 corresponding to the main shaft when the take-up lever finishes the take-up action; s3, setting a function omega = f (A) of the angular velocity of the main shaft with respect to the angle of the main shaft in one operation cycle, and satisfying the following conditions: f (0) = f (AT), f (A) is continuously derivable, and f '(0) = f' (AT); in the interval of 0-A1, omega is increased to omega n and continues to be increased; when t1 = A1 / omega n, the angle of the main shaft is A1; the time t2 for rotating to A2 meets the condition that t2-t1 < = tD; the main shaft angle is AT at the time T; and S4, in one operation cycle, the angle of the main shaft is obtained in real time, and the main shaft is controlled to rotate through the function relation omega = f (A).

Description

Technical Field

[0001] The invention relates to the technical field of sewing, and in particular to a method for controlling a sewing machine to prevent thread from being thrown off at low speed when sewing cloth. Background Art

[0002] High-density fabric generally refers to a dense fabric with a total warp and weft density exceeding 800 threads / 10cm. The yarns are dense and the gaps between the fibers are small. High-density fabric thread loss is a common process defect in the sewing process, manifesting as loose stitches, especially when sewing at low speeds. However, when the angular velocity exceeds a certain level, the thread loss phenomenon will disappear. Specifically, during the sewing process, when the needle penetrates the fabric and then withdraws, it will leave a needle-sized eyelet on the fabric. See the attached Figure 2 As shown in the figure, the size of the eyelet of ordinary fabric caused by needle punching basically does not change over time (or shrinks very slightly), but due to the characteristics of high-density fabric, the density of warp and weft yarns is high and the fabric is tight, the eyelet of the needle will gradually become smaller over time. The higher the density, the faster the eyelet shrinks. In the subsequent lockstitch formation process, the bottom thread and the top thread are successfully hooked under the fabric through the rotary hook structure, the thread section is completed, and the thread take-up rod begins to reel in the thread. See the attached figure. Figure 3 As shown in the figure, when the thread take-up lever moves upward to take up the upper thread on the right, the thread section moves to the middle of the fabric (i.e., the needle eye hole). Figure 4 As shown, the thread winding is completed. When the thread take-up rod is taking up the upper thread on the right, if the eyelet is larger, the upper thread on the right will not carry the upper thread on the left upwards, and if the eyelet is too small, it will squeeze the upper threads on both sides, causing the upper threads on both sides to be close together and with a certain pressure, and the upper thread on the right will carry the upper thread on the left upwards, bringing out the upper thread on the left as well. For the sake of convenience, in this application, this phenomenon is referred to as the phenomenon of incorrect upper thread pulling out when taking up the thread. Since the thread take-up rod is taking up the thread while feeding the material, the fabric moves to the left, and the upper thread brought out on the left may be pressed by the presser foot. The lower thread tension cannot pull out the upper thread pressed by the presser foot, so after the feeding is completed, there will be extra upper thread (that is, the part of the upper thread pressed by the presser foot), see the attached Figure 5 As shown, this creates a thread throw. For ease of explanation, in this application, the maximum eyelet diameter at which the upward movement of the right upper thread in the eyelet causes the left upper thread to move is referred to as the thread throw critical diameter D0. This critical diameter D0 is determined by the characteristics of the sewing machine, primarily due to factors such as the thread take-up force and the thickness of the upper thread. Therefore, after the needle lifts off the fabric and the thread take-up lever begins to reel in the upper thread, if the eyelet diameter is less than or equal to D0, the thread throw problem described above will occur.

[0003] For high-density fabrics, the eyelet gradually retracts after the needle exits the needle plate. During low-speed sewing, if the eyelet retracts too quickly, it may already be smaller than or equal to the critical thread throw diameter D0 by the time the thread take-up lever begins to reel in the thread. Consequently, the take-up lever may pull out the left upper thread as it reels in the right upper thread. Sewing with a sewing machine inevitably requires reducing the speed at certain critical points. This can easily cause thread throw with high-density fabrics, impacting garment quality. Currently, when sewing with high-density fabrics, increasing thread tension is often used to mitigate thread throw. However, this increases the probability of thread breakage, impacting both sewing quality and garment quality. Summary of the Invention

[0004] In view of the shortcomings of the prior art mentioned above, the technical problem to be solved by the present invention is to provide a control method for a sewing machine to prevent thread throwing when sewing fabrics at low speed. By controlling the angular velocity of the main shaft, the thread picking action is completed before the needle eye shrinks to a certain extent, thereby avoiding the occurrence of thread throwing.

[0005] To achieve the above object, the present invention provides a control method for a sewing machine to sew fabric at low speed without thread throwing, wherein the needle and thread take-up lever of the sewing machine are driven by a main shaft, and the main shaft rotates at an angle of 0 to A in one operation cycle of the needle. T , the starting time of the operation cycle is recorded as 0~T, and the control method includes the following steps:

[0006] S1. Determine the safe hole diameter D1 of the needle eyelet when the fabric is sewn in the sewing machine. Under the safe hole diameter D1, the needle eyelet will not be accidentally pulled out when the thread is picked up. Determine the time t required from the needle leaving the fabric to the needle eyelet shrinking to the safe hole diameter D1. D ;

[0007] S2, remember A T / T=ω n During one operating cycle, according to the thickness of the fabric to be sewn, determine the spindle angle A1 when the needle moves upward away from the fabric, and determine the spindle angle A2 when the thread take-up action is completed;

[0008] S3. Spindle angular velocity setting: Set the spindle angular velocity function of the spindle angle in a running cycle as ω = f(A), and satisfy the following conditions: f(0) = f(A T ), f(A) is continuously differentiable, and f′(0)=f′(A T ); in the range of 0 to A1, ω increases to ω n And continue to grow, t1=A1 / ω n ; t2-t1≤t D ;

[0009] S4. Sewing operation control: In one operation cycle, the main shaft angle is obtained in real time, and the main shaft rotation is controlled by the function relationship ω=f(A).

[0010] Furthermore, in the step S1, the thread throwing critical diameter D0 of the needle eyelet when the cloth is sewn in the sewing machine is first determined, and the thread-free safety aperture D1 is determined according to the thread throwing critical diameter D0, and D1 ≥ D0.

[0011] Furthermore, in step S1, the critical diameter D0 of the parabolic line and the time t D Obtained through multiple simulation tests.

[0012] Furthermore, in step S1, the method for determining the critical thread throwing diameter D0 is as follows: in the sewing machine, a plurality of eyelet holes of different diameters are drilled on the fabric according to a certain diameter gradient, and the action of the thread take-up rod picking up the upper thread after the needle moves upward during normal sewing operation is simulated in the eyelet holes of each diameter, and it is observed whether the upper thread is incorrectly pulled out during thread picking up. The diameter of the smallest eyelet hole in which this phenomenon does not occur is taken as the critical thread throwing diameter D0.

[0013] Furthermore, in step S1, time t D The method for determining t is as follows: in a sewing machine, use the needle to drill into the fabric to be sewn, then move the needle upwards, and record the changes in the eyelet. The time from the needle leaving the fabric to the eyelet shrinking to the safe aperture D1 without thread throwing is determined, which is the time t D .

[0014] Furthermore, in step S3, in the range 0 to A1, the angular acceleration of the main shaft first increases and then decreases.

[0015] Furthermore, in step S3, in the interval A1 to A2, the angular velocity ω of the main shaft first increases and then decreases.

[0016] Furthermore, in step S3, in the interval A1 to A2, the angular acceleration of the main shaft is gradually reduced.

[0017] Furthermore, in step S3, between A2 and A T In the interval, the angular velocity ω of the main axis gradually decreases, and the angular acceleration first decreases and then increases.

[0018] Furthermore, step S4 includes: obtaining the angle of the spindle, obtaining the theoretical angular velocity of the spindle according to the functional relationship ω=f(A), and obtaining the actual angular velocity of the spindle by measurement, judging the error between the actual angular velocity and the theoretical angular velocity; if the error meets the requirements, the spindle continues to rotate; if it does not meet the requirements, adjusting the driving source of the spindle, correcting the actual angular velocity of the spindle, so that the error meets the requirements to match the theoretical angular velocity.

[0019] As can be seen from the above, the control method of the present invention has the following beneficial effects:

[0020] 1. By changing the spindle speed within the cycle, the spindle speed in the angular range from the needle out of the fabric to the end of the thread take-up is increased, the time for thread take-up is reduced, and the phenomenon of incorrect pulling out of the upper thread during thread take-up caused by fabric shrinkage is avoided, thereby avoiding the phenomenon of thread throwing; the angular velocity of the spindle changes more evenly, which is more conducive to electronic control debugging and reduces vibration and noise.

[0021] 2. It can be used well for sewing high-density fabrics, overcoming the problem of thread throwing that is prone to occur in high-density fabrics, and can broaden the adaptability to fabrics of different thicknesses and densities.

[0022] 3. There is no need to adjust the structure of the sewing machine. It can adapt to different types of fabrics by simply changing the control method, and the improvement cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of the main shaft, thread take-up lever and needle of the sewing machine in the present invention.

[0024] Figure 2 Schematic diagram of the needle in a sewing machine moving upwards and away from the fabric, leaving a needle eye.

[0025] Figure 3 This is a diagram showing the thread take-up lever in a sewing machine starting to take up the thread.

[0026] Figure 4 This is a schematic diagram of the thread take-up work of the thread take-up lever in a sewing machine.

[0027] Figure 5 Schematic diagram of the sewing machine's presser foot pressing the upper thread to produce the thread throw.

[0028] Figure 6 Schematic diagram of the relationship curve between the angular velocity and angle of the main shaft in the present invention.

[0029] Figure 7 Schematic diagram of a curve showing the change of the angular velocity of the main shaft with time in the present invention.

[0030] Figure 8 Schematic diagram of the curve of the main shaft angle in one operating cycle in the present invention.

[0031] Figure 9 Schematic diagram of the curve of the spindle angular acceleration in one operating cycle in the present invention.

[0032] Figure 10 Schematic diagram of the control logic of the spindle angular velocity in the present invention.

[0033] Explanation of Figure Numbers

[0034] 1 spindle

[0035] 2 thread take-up lever

[0036] 3 needles

[0037] 4. Fabric

[0038] 5 needle holes

[0039] 6. Noodles

[0040] 7. Bottom Line DETAILED DESCRIPTION

[0041] The following describes the implementation of the present invention through specific embodiments. People skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0042] It should be noted that the structures, proportions, sizes, etc. depicted in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the conditions for the implementation of the present invention. Therefore, they have no substantial technical significance. Any modification of the structure, change in the proportional relationship, or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the efficacy and purpose of the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle", etc. quoted in this specification are only for the convenience of description and are not used to limit the scope of the implementation of the present invention. Changes or adjustments in their relative relationships should also be regarded as the scope of the implementation of the present invention without substantially changing the technical content.

[0043] See also Figures 1 to 10 The present invention provides a control method for a sewing machine to sew fabric at low speed without thread throwing. The sewing machine needle 3 and thread take-up rod 2 are driven by the main shaft 1. During normal sewing operation, the main shaft 1 rotates, driving the needle 3 and thread take-up rod 2 to circulate along a certain motion trajectory. In the present invention, the movement process of the needle 3 starting from the lowest position and then moving downward to the lowest position can be recorded as an operation cycle. The angle of rotation of the main shaft 1 during one operation cycle of the needle 3 is A. T , where A TGenerally, it is 360°. Preferably, the movement of the main shaft 1 is controlled by the electronic control system of the sewing machine. The main shaft 1 is controlled by a motor. The electronic control system is connected to the motor control, and the rotation speed of the main shaft 1 is controlled by controlling the rotation speed of the motor, and the rotation angle of the main shaft 1 can be recorded.

[0044] The control method of the present invention comprises the following steps:

[0045] S1. Determine the thread-free safety aperture D1 of the eyelet 5 when the fabric 4 is sewn in the sewing machine. Under the thread-free safety aperture D1, the upper thread 6 will not be pulled out when the thread is picked up. Determine the time t required from the needle 3 leaving the fabric 4 to the eyelet 5 shrinking to the thread-free safety aperture D1. D Time t D Input into the electronic control system, preferably, the electronic control system includes a control panel, and the time t is set by the control panel D And input it into the electronic control system. When sewing different fabrics 4, modify and input the corresponding time t through the control panel D .

[0046] In this embodiment, the no-thread-throwing safety aperture D1 is determined according to the critical thread-throwing diameter D0, and D1 ≥ D0. The critical thread-throwing diameter D0 can be determined by multiple simulation tests on fabric 4 in a sewing machine. Specifically, low-density fabric 4 (for example, fabric 4 with a total warp and weft density of less than 500 yarns / 10 cm) can be used in the sewing machine. It is required that the eyelet 5 drilled on the fabric 4 will not shrink, or the shrinkage degree is less than the required value and can be ignored. A plurality of eyelet holes 5 of different diameters are drilled in the low-density fabric 4. The eyelet holes 5 are set from small to large according to a certain diameter gradient, for example, the diameter gradient can be 0.1 mm. The action of the thread take-up rod 2 picking up the upper thread 6 after the needle 3 leaves upward during normal sewing is simulated in the eyelet holes 5 of each diameter, and it is observed whether the upper thread 6 is pulled out incorrectly during thread picking. The diameter of the minimum eyelet hole 5 where this phenomenon does not occur is taken as the critical thread-throwing diameter D0. In order to leave a safety factor, the non-casting line safety aperture diameter D1 can also be selected to be an appropriate value larger than the cast-line critical diameter D0. In other embodiments, other suitable methods can also be used to determine, for example, it can be obtained through simulation calculation.

[0047] In this embodiment, time t D The determination of the time interval t can be determined by multiple simulation tests on the fabric 4 in the sewing machine. Specifically, for the fabric 4 to be sewn, the needle 3 is used to drill into the fabric 4, and then the needle 3 is moved upward. At the same time, the changes in the eyelet 5 can be recorded by taking pictures with a high-frequency camera. According to the shooting picture and time, the time from the time the needle 3 leaves the fabric 4 to the time the eyelet 5 shrinks to the safety aperture D1 without thread throwing is determined, which is the time t. DIn other embodiments, it may be determined in other appropriate ways, for example, by simulation calculation.

[0048] S2, remember A T / T=ω n , is the average angular velocity of the main shaft 1; within one operating cycle, according to the thickness of the fabric 4 to be sewn, determine the angle A1 corresponding to the main shaft 1 when the needle 3 moves upward away from the fabric 4, and determine the angle A2 corresponding to the main shaft 1 when the thread take-up action is completed by the thread take-up lever 2.

[0049] In the conventional technology, uniform rotation is generally used during sewing, and the average angular velocity of the main shaft 1 in one operating cycle is denoted as ω n , the average angular velocity ω n It is also the operating design speed set on the control panel of the sewing machine panel. During the sewing process, the electronic control system needs to control the average angular velocity of the main shaft 1 in one operating cycle to be ω n The average angular velocity ω n The angles A1 and A2 are set according to the sewing working conditions of the specific sewing machine and are pre-set in the control system. After the angles A1 and A2 are determined, they are also set through the control panel and input into the electronic control system.

[0050] S3, spindle 1 angular velocity setting: see Figures 6 to 9 , set the function of the angular velocity of spindle 1 with respect to the angle of spindle 1 within an operating cycle as ω = f(A), and satisfy the following conditions:

[0051] (a)f(0)=f(A T ), f(A) is continuously differentiable, and f′(0)=f′(A T Since the needle 3, thread take-up lever 2 and spindle 1 in the sewing machine all operate continuously in sequence according to the operating cycle, the starting angular velocity and angular acceleration of the spindle 1 in each operating cycle must be the same, and the angular velocity curve of the spindle 1 also changes smoothly, that is, it is continuously differentiable.

[0052] (b) In the range of 0 to A1, ω increases from ω0 to ω n , and continues to increase to ω1, the corresponding time is recorded as 0~t1, see Figure 7 , t1=A1 / ω n , that is, the time corresponding to the angle of the main axis 1 being A1 is t1=A1 / ω n The integral of the angular velocity with respect to time is the angle of rotation of the main shaft 1, and A(t) is the function relationship between the angle and time.

[0053] (c) t2-t1≤t D, that is, when the spindle rotates to angle A1, this condition is used to ensure that there will be no problem of no line. When the spindle 1 rotates to angle A1, the corresponding time is t1, the angular velocity is ω1, which is greater than ω n , the needle 3 leaves the fabric 4. In the subsequent rotation, the spindle 1 will be faster than the normal uniform speed operation mode, so it will drive the thread take-up rod 2 to take up the thread at a faster speed. The time to reach the angle A2 is t2, which is longer than the time A2 / ω required in the uniform speed mode. n Much earlier, at this time, the thread take-up rod 2 has finished taking up the thread, and the time spent during this period is t2-t1≤t D That is, before the diameter of the needle eye 5 is reduced to the safe aperture D1 without thread throwing, the thread take-up rod 2 has finished taking up the thread, ensuring that the upper thread 6 will not be pulled out incorrectly during thread taking up, thereby avoiding the formation of thread throwing.

[0054] (d) That is, the spindle 1 rotates to angle A T The time spent is exactly T; this condition is used to meet the setting requirements of the normal working cycle of the sewing machine.

[0055] See also Figures 6 to 9 As a preferred design, in this embodiment, in the range of 0 to A1, as the angle A of the main shaft 1 increases, the angular acceleration of the main shaft 1 first increases and then decreases, and correspondingly, the angular acceleration of the main shaft 1 changes with time t also first increases and then decreases. In the range of A1 to A2, as the angle A of the main shaft 1 increases, the angular velocity ω of the main shaft 1 first increases and then decreases, and correspondingly, the angular acceleration of the main shaft 1 changes with time t also first increases and then decreases, and the angular acceleration of the main shaft 1 gradually decreases, from a positive number to a negative number. In the range of A2 to A T In the interval, as the angle A of the main shaft 1 increases, the angular velocity ω of the main shaft 1 gradually decreases. Correspondingly, the angular acceleration of the main shaft 1 also increases first and then decreases with time t, and the angular acceleration first decreases and then increases, gradually becomes flat and becomes 0.

[0056] As a preferred design, t D 、A T 、ω n , A1, A2 and other parameters are input into the electronic control system, and the constraints of the above-mentioned function ω=f(A) are set, and the electronic control system automatically generates a suitable specific function.

[0057] S4. Sewing operation control: In one operation cycle, the angle of the main shaft 1 is obtained in real time, and the rotation of the main shaft 1 is controlled by the function relationship ω=f(A).

[0058] See also Figure 10In this embodiment, preferably, the angle of the spindle 1 is obtained through the electronic control system, the theoretical angular velocity of the spindle 1 is obtained according to the functional relationship ω = f(A), and the actual angular velocity of the spindle 1 is measured by an angle meter to obtain the actual angular velocity of the spindle 1. The error between the actual angular velocity and the theoretical angular velocity is determined. If the error meets the requirements (for example, the actual angular velocity = the theoretical angular velocity), the spindle 1 continues to rotate. If it does not meet the requirements, the drive source (motor) of the spindle 1 is adjusted. Specifically, the motor speed is adjusted by adjusting the current, and the actual angular velocity of the spindle 1 is corrected so that the error meets the requirements to match the theoretical angular velocity. The angle of the spindle 1 can be determined by the electronic control system by cumulatively calculating the operating conditions of the motor driving the spindle 1, or it can be measured by an additional sensor.

[0059] After the spindle 1 completes one operating cycle, it enters the next operating cycle. In each operating cycle, the spindle 1 rotates in the same way, the thread take-up lever 2 and the needle 3 move in the same way, and they move continuously in a cycle.

[0060] The control method of the present invention can be used for sewing high-density fabrics 4 , and based on its principle, can also be used for sewing low-density fabrics 4 .

[0061] As can be seen from the above, the control method of the present invention has the following beneficial effects:

[0062] 1. By changing the spindle 1 speed within the cycle, the spindle 1 speed is increased in the angular range from when the needle 3 exits the fabric 4 to when the thread take-up is completed, the time for thread take-up is reduced, and the phenomenon of incorrect pulling out of the upper thread 6 during thread take-up caused by the contraction of the fabric 4 is avoided, thereby avoiding the thread throwing phenomenon; the angular velocity change of the spindle 1 is more uniform, which is more conducive to electronic control debugging and reduces vibration and noise.

[0063] 2. It can be well used for sewing high-density fabrics 4, overcoming the problem of thread throwing easily occurring in high-density fabrics 4, and can broaden the adaptability to fabrics 4 of different thicknesses and densities.

[0064] 3. There is no need to adjust the structure of the sewing machine. It can adapt to different types of fabrics by simply changing the control method. 4. The improvement cost is low.

[0065] In summary, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

[0066] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A method for controlling a sewing machine to prevent thread loss at low speed when sewing fabric. The sewing machine needle and thread take-up lever are driven by a main shaft. The main shaft rotates at an angle of 0 to A during one operation cycle of the needle. T The starting time of the operation cycle is recorded as 0~T, which is characterized by: The control method comprises the following steps: S1. Determine the safe hole diameter D1 of the needle eyelet when the fabric is sewn in the sewing machine. Under the safe hole diameter D1, the needle eyelet will not be accidentally pulled out when the thread is picked up. Determine the time t required from the needle leaving the fabric to the needle eyelet shrinking to the safe hole diameter D1. D ; S2, remember A T / T=ω n During one operating cycle, according to the thickness of the fabric to be sewn, determine the spindle angle A1 when the needle moves upward away from the fabric, and determine the spindle angle A2 when the thread take-up action is completed; S3. Spindle angular velocity setting: Set the spindle angular velocity function of the spindle angle in a running cycle as ω = f(A), and satisfy the following conditions: f(0) = f(A T ), f(A) is continuously differentiable, and f′(0)=f′(A T ); in the range of 0 to A1, ω increases to ω n And continue to grow, t1=A1 / ω n ; t2-t1≤t D ; S4. Sewing operation control: In one operation cycle, the main shaft angle is obtained in real time, and the main shaft rotation is controlled by the function relationship ω=f(A).

2. The control method according to claim 1, wherein: In the step S1, the thread throwing critical diameter D0 of the needle eyelet when the cloth is sewn in the sewing machine is first determined, and the thread-free safety aperture D1 is determined according to the thread throwing critical diameter D0, and D1≥D0.

3. The control method according to claim 2, wherein: In step S1, the critical diameter D0 of the parabolic line and the time t D Obtained through multiple simulation tests.

4. The control method according to claim 3, wherein: In step S1, the method for determining the critical thread throwing diameter D0 is as follows: in a sewing machine, a plurality of eyelets of different diameters are drilled on the fabric according to a certain diameter gradient, and the action of the thread take-up rod picking up the upper thread after the needle moves upward during normal sewing operation is simulated in the eyelets of each diameter, and whether the upper thread is incorrectly pulled out during thread picking up occurs, and the diameter of the smallest eyelet where this phenomenon does not occur is taken as the critical thread throwing diameter D0.

5. The control method according to claim 3, wherein: In step S1, time t D The method for determining t is as follows: in a sewing machine, use the needle to drill into the fabric to be sewn, then move the needle upwards, and record the changes in the eyelet. The time from the needle leaving the fabric to the eyelet shrinking to the safe aperture D1 without thread throwing is determined, which is the time t D .

6. The control method according to claim 1, wherein: In step S3, in the range 0 to A1, the angular acceleration of the main shaft first increases and then decreases.

7. The control method according to claim 1, wherein: In step S3, in the interval A1 to A2, the angular velocity ω of the main shaft first increases and then decreases.

8. The control method according to claim 7, wherein: In step S3, in the interval A1 to A2, the angular acceleration of the main shaft is gradually reduced.

9. The control method according to claim 1, wherein: In the step S3, between A2 and A T In the interval, the angular velocity ω of the main axis gradually decreases, and the angular acceleration first decreases and then increases.

10. The control method according to claim 1, wherein: The step S4 includes: obtaining the angle of the main shaft, obtaining the theoretical angular velocity of the main shaft according to the functional relationship ω=f(A), and obtaining the actual angular velocity of the main shaft by measurement, and determining the error between the actual angular velocity and the theoretical angular velocity. If the error meets the requirements, the main shaft continues to rotate; if not, the driving source of the main shaft is adjusted to correct the actual angular velocity of the main shaft so that the error meets the requirements to match the theoretical angular velocity.

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