Method for reducing cogging force of permanent magnet linear motor

Abstract

The invention discloses a method for reducing the cogging force of a permanent magnet linear motor, and the method comprises the steps: fusing an edge end tooth with a first tooth based on an air gap magnetic conductance equivalence principle, and achieving the parallel connection on a magnetic circuit. And the width of the first lengthened tooth is ensured to be the same as that of other teeth, and the length of the first lengthened tooth is changed, so that the cogging force of the linear motor can be greatly reduced without side end teeth, and the running stability of the motor is improved. Meanwhile, the method is suitable for any long-primary permanent magnet linear motor matched with a pole slot. In addition, the method has fewer motor size parameters, and compared with an edge end tooth scheme, the method greatly reduces the optimal time of the motor.

Description

Technical Field

[0001] The present invention relates to the technical field of motors, and in particular to a method for reducing the cogging force of a permanent magnet linear motor. Background Art

[0002] Because the iron core of a linear motor is broken, cogging forces are inevitable. Therefore, it is crucial to reduce cogging forces, thereby reducing motor speed fluctuations and improving linear motor performance.

[0003] In existing technologies, linear motor primary systems reduce cogging forces by adding side teeth. However, these teeth increase the length of the permanent magnet linear motor, reducing the motor's thrust density. This is especially noticeable when the motor has fewer slots, as the side teeth contribute significantly to the motor's total length. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. The present invention proposes a method for reducing the cogging force of a permanent magnet linear motor. Based on the air gap permeability equivalence principle, the side teeth are integrated with the first teeth and connected in parallel on the magnetic circuit. And the width of the first extended tooth is ensured to be the same as the width of other teeth. By changing the length of the first extended tooth, it is possible to achieve the goal of not needing side teeth and greatly reduce the cogging force of the linear motor, thereby improving the operating stability of the motor. At the same time, this method is applicable to any long primary permanent magnet linear motor with any pole slot combination. In addition, this method has fewer motor size parameters, and compared with the side tooth solution, it greatly reduces the optimal time of the motor.

[0005] A method for reducing the cogging force of a permanent magnet linear motor according to an embodiment of the present invention includes:

[0006] Step S1: Calculate the air gap permeability equivalent model of the permanent magnet linear motor;

[0007] Step S2: connecting the edge end tooth and the first tooth adjacent to the edge end tooth in parallel to form a transition edge end tooth; the edge end tooth and the first tooth are connected in parallel on the magnetic circuit;

[0008] Step S3: a first lengthened tooth is provided on the transition edge tooth, and the length of the first lengthened tooth is changed;

[0009] Step S4: Verify that the difference δ between the first extended tooth length ht and the second tooth length h satisfies the following relationship: 0.5H gap ≤δ≤0.7H gap .

[0010] According to an embodiment of the present invention, the present invention proposes a method for reducing the cogging force of a permanent magnet linear motor. Based on the air gap permeability equivalence principle, the side teeth are integrated with the first teeth and connected in parallel on the magnetic circuit. And the width of the first extended tooth is ensured to be the same as the width of other teeth. By changing the length of the first extended tooth, it is possible to achieve the goal of not needing side teeth and greatly reduce the cogging force of the linear motor, thereby improving the operating stability of the motor. At the same time, this method is applicable to any long primary permanent magnet linear motor with any pole slot combination. In addition, this method has fewer motor size parameters and greatly reduces the motor optimization time compared to the side tooth solution.

[0011] According to some embodiments of the present invention, step S1 further includes:

[0012] Ensure that the length of the side teeth remains unchanged and change the width of the side teeth;

[0013] The width w2 of the transition edge teeth can be expressed as:

[0014] Where: Λa is the air gap permeability of the side tooth, Λgap is the air gap permeability of the yoke, wa is the width of the side tooth, and w1 is the distance between the side tooth and the first tooth.

[0015] According to some embodiments of the present invention, the first lengthened tooth permeability Λ is calculated t1 =Λ a w a +Λ gap w1+Λ t w t

[0016] Where: Λt is the air gap permeability of the first tooth.

[0017] According to some embodiments of the present invention, step S2: connecting the edge end tooth and the first tooth adjacent to the edge end tooth in parallel to form a transition edge end tooth further comprises: connecting the edge end tooth and the first tooth in parallel and sharing a magnetic guide.

[0018] According to some embodiments of the present invention, according to step S3: calculating the first lengthened tooth length ht, the first lengthened tooth length ht can be expressed as:

[0019] According to some embodiments of the present invention, step S2 further includes winding a coil around the transition edge teeth.

[0020] According to some embodiments of the present invention, the first lengthened tooth width is ensured to be the same as the second tooth width wt.

[0021] According to some embodiments of the present invention, step S4 includes: calculating the first lengthened tooth length ht

[0022] Calculate the difference δ between the first extended tooth length ht and the second tooth length h:

[0023] The primary core length of the linear motor manufactured using the method of reducing the cogging force of the permanent magnet linear motor in this application is reduced by 2 (wa+w1). Similarly, this means that when the secondary length remains unchanged, the motor stroke increases by 2 (wa+w1), and the corresponding thrust density is significantly improved.

[0024] The permanent magnet linear motor using the method of the present invention has fewer dimensional parameters and greatly shortens the time required to optimize the motor.

[0025] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0027] Figure 1 This is the topology diagram of a traditional permanent magnet linear motor with edge teeth;

[0028] Figure 2 This is a topology diagram of a transition permanent magnet linear motor according to embodiment 1 of the present invention;

[0029] Figure 3 This is a topological diagram of a permanent magnet linear motor according to embodiment 1 of the present invention;

[0030] Figure 4 It is the air gap equivalent model of the traditional permanent magnet linear motor with edge teeth;

[0031] Figure 5 This is the air gap equivalent model of the transition permanent magnet linear motor according to embodiment 1 of the present invention;

[0032] Figure 6 This is the air gap equivalent model of the permanent magnet linear motor according to embodiment 1 of the present invention;

[0033] Figure 7 This is a comparison waveform of the cogging force of a 6-slot 8-pole permanent magnet linear motor used in Example 1 of the present invention.

[0034] Primary iron core 1, first tooth 1-1, second tooth 1-2, edge tooth 1-3, transition edge tooth 1-4, first extended tooth 1-5; coil 2; permanent magnet 3; secondary magnetic yoke 4. DETAILED DESCRIPTION

[0035] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0036] Reference below Figure 1 A method for reducing the cogging force of a permanent magnet linear motor according to an embodiment of the present invention is described.

[0037] A method for reducing the cogging force of a permanent magnet linear motor according to an embodiment of the present invention includes:

[0038] Step S1: Calculate the air gap permeability equivalent model of the permanent magnet linear motor;

[0039] Step S2: connecting the edge end tooth and the first tooth adjacent to the edge end tooth in parallel to form a transition edge end tooth; the edge end tooth and the first tooth are connected in parallel on the magnetic circuit;

[0040] Step S3: a first lengthened tooth is provided on the transition edge tooth, and the length of the first lengthened tooth is changed;

[0041] Step S4: Verify that the difference δ between the first extended tooth length ht and the second tooth length h satisfies the following relationship: 0.5H gap ≤δ≤0.7H gap .

[0042] Among them, H gap Indicates the air gap length; the air gap length is the size of the gap between the motor rotor and stator

[0043] In this embodiment, for the introduction of the permanent magnet linear motor provided in the present invention, please refer to the embodiment of the design method of the permanent magnet linear motor mentioned above, which will not be described in detail here.

[0044] It should also be noted that the air gap permeability equivalent model of the permanent magnet linear motor is: N motor sub-units can be arranged in sequence along one direction, and the initial rectangular teeth, intermediate rectangular teeth and ending rectangular teeth in any motor sub-unit are arranged in sequence along the x-axis, and the permanent magnets are provided on the secondary yoke 4 and arranged below the above-mentioned various teeth in the z-axis; please refer to the figure, in which N=2, that is, two motor sub-units are used as an example for explanation: the first motor sub-unit can be a pole slot unit, including an end tooth, a first tooth, a second tooth until the ending tooth, and stator slots formed by these teeth. The stator slots are used to place the motor windings. The figure directly gives the connection method of the winding phases in each stator slot and the permanent magnet (there is a permanent magnet corresponding to each stator slot in the first motor sub-unit. In order to avoid confusion in the connection lines, only the permanent magnet on the far left is used as an example for annotation);

[0045] The change in the coordinates of the calibration points on the calibration plate can be calculated based on the theoretical coordinates of the calibration points on the calibration plate and the actual coordinates of the calibration points on the calibration plate currently detected. The calibration plate will expand and contract at different temperatures. The expansion and contraction per unit length of the calibration plate in the X direction is S X Represents the change of the calibration plate in the X direction due to thermal expansion and contraction, and the expansion and contraction per unit length in the Y direction S Y Represents the change of the calibration plate in the Y direction due to thermal expansion and contraction.

[0046] The present invention proposes a method for reducing the cogging force of a permanent magnet linear motor. Based on the air gap permeability equivalence principle, the side teeth are integrated with the first teeth and connected in parallel on the magnetic circuit. The width of the first extended tooth is ensured to be the same as the width of the other teeth. By changing the length of the first extended tooth, it is possible to eliminate the need for side teeth and significantly reduce the cogging force of the linear motor, thereby improving the operating stability of the motor. At the same time, this method is applicable to any long primary permanent magnet linear motor with any pole slot combination. In addition, this method has fewer motor size parameters and greatly reduces the motor optimization time compared to the side tooth solution.

[0047] Considering that the transition edge teeth 1-4 need to be wound with coils 22, and the length of the winding ends on the second teeth 1-2 is different, it will cause different resistance, inductance and winding fixtures, thereby reducing the reliability of the motor operation. Therefore, it is necessary to ensure that the width of the first extended tooth 1-5 is the same as the width wt of the second tooth 1-2 in step S2.

[0048] According to some embodiments of the present invention, step S1 further includes: ensuring that the length of the side end teeth remains unchanged and changing the width of the side end teeth;

[0049] The width w2 of the transition edge tooth is expressed as:

[0050]

[0051] Where: Λa is the air gap permeability of the side tooth, Λgap is the air gap permeability of the yoke, wa is the width of the side tooth, and w1 is the distance between the side tooth and the first tooth.

[0052] According to some embodiments of the present invention, the first lengthened tooth permeability Λ is calculated t1 =Λ a w a +Λ gap w1+Λ t w t

[0053] Where: Λt is the air gap permeability of the first tooth.

[0054] According to some embodiments of the present invention, step S2: connecting the edge end tooth and the first tooth adjacent to the edge end tooth in parallel to form a transition edge end tooth further includes: connecting the edge end tooth and the first tooth in parallel and sharing a magnetic guide.

[0055] The main point in this application is that after two magnetic permeances are connected in parallel, the total magnetic permeance will be greater than that of any one of them. And the magnetic permeance is proportional to the width and length of the teeth.

[0056] The total width of the transition edge teeth 1-4 is w2+wt, such as Figure 2 , which is larger than the width of the second tooth 1-2, so the winding end must be longer, which means that the resistance and inductance are larger than those of the coil 2 on the second tooth, which will cause the resistance and inductance to be uneven and affect the operating stability.

[0057] Therefore, we say that to ensure that the width of the side teeth is the same as that of the second teeth 1-2, in order to ensure the same magnetic permeability, the length of the side teeth can only be increased. Therefore, changing the length of the first extended teeth 1-5 can solve the above problem.

[0058] According to some embodiments of the present invention, according to step S3: first lengthened tooth length ht, the calculation of the first lengthened tooth length ht can be expressed as:

[0059] According to some embodiments of the present invention, step S2 further includes winding the coil 2 around the transition edge teeth.

[0060] According to some embodiments of the present invention, it is ensured that the first lengthened tooth width is the same as the second tooth width wt.

[0061] According to some embodiments of the present invention, step S4 includes: calculating the first lengthened tooth length ht

[0062] Calculate the difference δ between the first extended tooth length ht and the second tooth length h:

[0063] In this embodiment, if Figure 1 The figure shows the topology of a traditional permanent magnet linear motor with edge teeth, and the primary core 1 of the motor is symmetrical on the left and right. Therefore, only the left side is analyzed here, and the right side is symmetrical and will not be repeated.

[0064] Step 1: Establish an equivalent model of the air gap magnetic permeability of a traditional permanent magnet linear motor with edge teeth, such as Figure 4 shown.

[0065] Step 2: Ensure the length of the side end teeth 1-3 remains unchanged, change the width of the side end teeth, and at the same time merge the side end teeth 1-3 with the first teeth 1-1 adjacent to the side end teeth to form transitional side end teeth 1-4. At this time, the width w2 of the transitional side end teeth 1-4 can be expressed as:

[0066]

[0067] Where: Λ a is the air gap permeability of the edge teeth 1-3, Λ gap is the yoke air gap permeability, w a is the width of the side tooth 1-3, and w1 is the distance between the side tooth 1-3 and the first tooth 1-1.

[0068] The specific topology diagram is as follows Figure 2 As shown in the figure, the air gap permeability equivalent model is as follows: Figure 5 As shown;

[0069] In the third step, considering that the transition edge teeth 1-4 need to be wound with coils 22, and the length of the winding ends on the second teeth 1-2 is different, it will cause different resistance, inductance and winding fixtures, thereby reducing the reliability of the motor operation. Therefore, based on the second step, it is necessary to ensure that the width of the first extended tooth 1-5 is the same as the width of the second tooth 1-2 w t Same, change the length of the first extended tooth 1-5, calculate the magnetic permeability Λ of the first extended tooth 1-5 t Expressed as:

[0070] Λ t1 =Λ a w a +Λ gap w1+Λ t w t

[0071] Where: t is the air gap permeability of the first tooth 1-1.

[0072] Step 4: Calculate the length h of the first extended tooth 1-5 t It can be expressed as:

[0073]

[0074] Step 5: Establish the length h of the first extended tooth 1-5 t The relationship between the length h of the second tooth 1-2 and the difference δ satisfies:

[0075]

[0076] Preferred: δ and air gap length H gap The following relationship is satisfied: 0.5H gap ≤δ≤0.7H gap

[0077] The specific topology diagram is as follows Figure 3 As shown in the figure, the air gap permeability equivalent model is as follows: Figure 6 As shown;

[0078] Compare Figure 1 and Figure 3 The permanent magnet linear motor using the method of the present invention can reduce the length of the primary core by 2 (w a +w1), similarly, it means that when the secondary length remains unchanged, the motor stroke increases by 2 (w a +w1), and the corresponding thrust density is significantly improved.

[0079] Figure 7 The cogging force comparison waveform of the 6-slot 8-pole permanent magnet linear motor in Example 1 of the present invention shows that the cogging force of the unit motor of the present invention is reduced by about 24.3% compared with the traditional solution and by about 71.1% compared with the solution without end teeth.

[0080] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, illustrative uses of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0081] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the claims and their equivalents.

Claims

1. A method for reducing the cogging force of a permanent magnet linear motor, characterized in that: include: Step S1: Calculate the air gap permeability equivalent model of the permanent magnet linear motor; Step S2: connecting the edge end tooth and the first tooth adjacent to the edge end tooth in parallel to form a transition edge end tooth; the edge end tooth and the first tooth are connected in parallel on the magnetic circuit; Step S3: a first lengthened tooth is provided on the transition edge tooth, and the length of the first lengthened tooth is changed; Step S4: Verify that the difference δ between the first extended tooth length ht and the second tooth length h satisfies the following relationship: 0.5H gap ≤δ≤0.7H gap .

2. The method for reducing the cogging force of a permanent magnet linear motor according to claim 1, wherein: The step S1 further includes: ensuring that the length of the side end teeth remains unchanged and changing the width of the side end teeth; The width w2 of the transition edge teeth is expressed as: Where: Λa is the air gap permeability of the side tooth, Λgap is the air gap permeability of the yoke, wa is the width of the side tooth, and w1 is the distance between the side tooth and the first tooth.

3. The method for reducing the cogging force of a permanent magnet linear motor according to claim 2, characterized in that: Calculate the first extended tooth permeability Λ t1 =Λ a w a +Λ gap w1+Λ t w t Where: Λt is the air gap permeability of the first tooth.

4. The method for reducing the cogging force of a permanent magnet linear motor according to claim 1, wherein: Step S2: connecting the edge end tooth and the first tooth adjacent to the edge end tooth in parallel to form a transition edge end tooth further includes: connecting the edge end tooth and the first tooth in parallel and sharing a magnetic guide.

5. The method for reducing the cogging force of a permanent magnet linear motor according to claim 2, characterized in that: According to step S3: the first lengthened tooth length ht, the calculation of the first lengthened tooth length ht can be expressed as:

6. The method for reducing the cogging force of a permanent magnet linear motor according to claim 1, wherein: The step S2 further includes winding a coil around the transition edge teeth.

7. The method for reducing the cogging force of a permanent magnet linear motor according to claim 2, characterized in that: The first lengthened tooth width is ensured to be the same as the second tooth width wt.

8. The method for reducing the cogging force of a permanent magnet linear motor according to claim 3, characterized in that: Step S4 includes: calculating the first lengthened tooth length ht Calculate the difference δ between the first extended tooth length ht and the second tooth length h:

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