Halbach permanent magnet array with double-layer structure

Abstract

The invention provides a Halbach array with a double-layer structure. The structure can be divided into an upper layer and a lower layer; the upper layer is a rectangular permanent magnet array, and every four permanent magnet arrays are periodically arranged in a group from left to right along the horizontal direction according to the upper, right, lower and left magnetizing directions; the permanent magnets magnetized up and down are main permanent magnets, the permanent magnets magnetized left and right are secondary permanent magnets, the heights of all the rectangular permanent magnets are equal, the widths of the main permanent magnets are kept consistent, and the secondary permanent magnets are in the same way; the lower layer is a trapezoidal permanent magnet array, the shape is an isosceles trapezoid, the width of the upper bottom is the same as that of the rectangle, regular trapezoids and inverted trapezoids are arranged in a staggered mode in the horizontal direction, the trapezoids and the rectangles are in one-to-one correspondence, and the magnetizing direction is consistent with that of the rectangle in the upper layer; the heights of all the trapezoidal permanent magnets are equal, the sizes of the main permanent magnets are consistent, and the secondary permanent magnets are similar; the shape of the trapezoid main permanent magnet is not limited to be a regular trapezoid or an inverted trapezoid. The double-layer structure permanent magnet array is symmetrically and periodically distributed.

Description

Technical Field

[0001] The present invention belongs to the field of permanent magnet arrays. Taking a one-dimensional Halbach array as the research object, the thrust fluctuation, thrust constant, and no-load back electromotive force performance generated by the array as the mover of a planar motor are studied. In order to improve the motor speed-up ability and reduce harmonic interference, a double-layer structure Halbach permanent magnet array is proposed. Background Art

[0002] The Halbach array is a permanent magnet array with a special arrangement structure proposed by the American physicist Klaus Halbach in 1979. Compared with ordinary magnetic steels, it can exhibit the magnetic field characteristics of being strong on one side and weak on the other side. The magnetic induction intensity of this array shows a sine distribution in the horizontal direction and a cosine distribution in the vertical direction.

[0003] The magnetic field concentrating characteristic of the Halbach array enables it to generate a relatively large thrust density. Interacting with the energized coil can generate a thrust in the horizontal direction and a suspension force in the vertical direction. Through the establishment of a magnetic field model and the decoupling of electromagnetic force and current, the motion control of this array can be realized. Domestic and foreign scholars have developed various types of linear and planar motors based on the characteristics of this array, which are widely used in large-stroke, high-precision, and high-stability measurement and manufacturing equipment required for precision instrument processing, vision system scanning, load platform operation, and medical equipment manufacturing.

[0004] On the one hand, the magnetic induction intensity of the original Halbach array is not a standard sine-cosine distribution. Due to the existence of harmonic interference, it will inevitably bring the influence of thrust fluctuation. On the other hand, the no-load back electromotive force generated by the Halbach array will affect the speed-up performance of the array. The double-layer structure Halbach array of the present invention can maintain a relatively large thrust constant while having less harmonic interference and back electromotive force amplitude through reasonable parameter design. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a double-layer structure Halbach permanent magnet array to solve the problems in the prior art.

[0006] The technical solution adopted by the present invention is as follows:

[0007] To improve the speed-up ability and operation stability of the Halbach array, a Halbach permanent magnet array with a double-layer structure is proposed in this paper. The permanent magnet array is divided into upper and lower layers. The upper layer is a rectangular permanent magnet array, which is periodically arranged in groups of four along the horizontal direction from left to right according to the magnetization directions of up, right, down, and left. The permanent magnets magnetized up and down are the main permanent magnets, and the permanent magnets magnetized left and right are the secondary permanent magnets. The heights of all rectangular permanent magnets are equal, the widths of the main permanent magnets are consistent, and the same applies to the secondary permanent magnets. The lower layer is a trapezoidal permanent magnet array, with an isosceles trapezoid shape. The upper base is the same width as the rectangle, and the regular trapezoids and inverted trapezoids are arranged alternately along the horizontal direction. The trapezoids correspond to the rectangles one by one, and the magnetization direction is the same as that of the upper-layer rectangle. The heights of all trapezoidal permanent magnets are equal, the sizes of the main permanent magnets are consistent, and the same applies to the secondary permanent magnets. The shape of the trapezoidal main permanent magnet is not limited to a regular trapezoid or an inverted trapezoid. The double-layer structure permanent magnet array is symmetrically and periodically distributed. The length of a single period is L, and the total height of the rectangle and the trapezoid is L / 4. The width of the rectangular main permanent magnet is a, the height of the rectangular main permanent magnet is c, and the width of the lower base of the trapezoidal main permanent magnet is b.

[0008] Furthermore, the width of the rectangular secondary permanent magnet is L / 2 - a, and the height is c.

[0009] Furthermore, the upper base of the trapezoidal main permanent magnet is a, the height is L / 4 - c, the upper base of the trapezoidal secondary permanent magnet is L / 2 - a, the lower base is L / 2 - b, and the height is L / 4 - c.

[0010] Furthermore, the range of the width a of the rectangular main permanent magnet is [0, L / 2], the range of the height c is [0, L / 4], and the range of the width b of the lower base of the trapezoid is [0, L / 2].

[0011] Furthermore, there is no regulation on the range of the upper and lower bases of the trapezoid. That is, when a < b, the trapezoidal main permanent magnet is a regular trapezoid, and the secondary permanent magnet with L / 2 - a > L / 2 - b is an inverted trapezoid. Conversely, when a > b, the trapezoidal main permanent magnet is an inverted trapezoid, and the secondary permanent magnet with L / 2 - A < L / 2 - b is a regular trapezoid. Otherwise, when a = b, they are all rectangles.

[0012] Compared with the original Halbach array, the present invention has the following characteristics:

[0013] 1. The magnetic induction intensity of the double-layer structure Halbach array has better sinusoidality and cosinusoidality in the horizontal and vertical directions, less harmonic content, and a smaller thrust wave.

[0014] 2. The double-layer structure Halbach array can generate a smaller no-load back electromotive force amplitude. Description of the Drawings

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the accompanying drawings required for the description of the embodiments. Obviously, the accompanying drawings in the following description are only the preferred embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0016] Figure 1 , cross-sectional schematic diagram of a double-layer structure Halbach array with a trapezoidal main permanent magnet as a regular trapezoid;

[0017] Figure 2 , cross-sectional size schematic diagram of the main permanent magnet and the secondary permanent magnet;

[0018] Figure 3 , cross-sectional view of a planar motor composed of a symmetric single-period double-layer Halbach array;

[0019] Figure 4 , magnetic field magnetic force line distribution of a double-layer Halbach array when the air gap height is 1 mm;

[0020] Figure 5 , distribution curves of the magnetic induction intensity in the horizontal and vertical directions of the original Halbach array and the double-layer Halbach array when the air gap height is 1 mm, Figure 5 (a) is the Halbach array, Figure 5 (b) is the double-layer Halbach array;

[0021] Figure 6 , the thrust fluctuations of the two arrays when the horizontal thrust is 3 N are as Figure 6 (a) shown, the no-load back electromotive force generated by a single-phase coil at a moving speed of 1 m / s is as Figure 6 (b) shown, and the relationship curves of the thrust and the required current generated by the two arrays, that is, the thrust constant curves, are as Figure 6 (c) shown. Specific embodiments

[0022] The double-layer structure permanent magnet array proposed in this paper is as Figure 1As shown in the figure, the permanent magnet array is divided into two upper and lower layers. The upper layer is a rectangular permanent magnet array. Along the horizontal direction, every four pieces are grouped in a periodic arrangement from left to right according to the magnetization directions of up, right, down, and left. The permanent magnets magnetized up and down are the main permanent magnets, and the permanent magnets magnetized left and right are the secondary permanent magnets. The heights of all rectangular permanent magnets are equal, the widths of the main permanent magnets are consistent, and the same applies to the secondary permanent magnets. The lower layer is a trapezoidal permanent magnet array, with an isosceles trapezoidal shape. The upper base has the same width as the rectangle. Along the horizontal direction, regular trapezoids and inverted trapezoids are arranged alternately, with each trapezoid corresponding to a rectangle, and the magnetization direction is consistent with that of the upper-layer rectangle. The heights of all trapezoidal permanent magnets are equal, the sizes of the main permanent magnets are consistent, and the same applies to the secondary permanent magnets. The shape of the trapezoidal main permanent magnet is not limited to a regular trapezoid or an inverted trapezoid. The double-layer structure permanent magnet array is symmetrically and periodically distributed. The length of a single period is L, and the total height of the rectangle and the trapezoid is L / 4. The width of the rectangular main permanent magnet is a, the height of the rectangular main permanent magnet is c, and the width of the lower base of the trapezoidal main permanent magnet is b. The specific dimensions of the main permanent magnet and the secondary permanent magnet are as shown in Figure 2 shown.

[0023] Step 1: Select a symmetric single-period double-layer Halbach array as the mover of the motor according to the period length of 40 mm, as shown in Figure 3 the figure. The stator uses a total of four layers of PCB coil wires and adopts a three-phase structure.

[0024] Step 2: Establish a mathematical model of the motor. Taking the thrust ripple, thrust constant, and no-load back electromotive force as the optimization objectives, perform multi-objective optimization to select the parameters a = 6 mm, b = 18 mm, and c = 8 mm.

[0025] Step 3: Perform finite element simulation on the double-layer Halbach array of the size corresponding to the above parameters in the Maxwell simulation software. The magnetic field magnetic force line distribution at a air gap height of 1 mm is as shown in Figure 1 the figure. The magnetic induction intensity curve is as shown in Figure 4 the figure. The solid line is the magnetic induction intensity in the horizontal direction, and the dashed line is the magnetic induction intensity in the vertical direction. Figure 5 (a) is the magnetic induction intensity of the Halbach array, Figure 5 (b) is the magnetic induction intensity of the double-layer structure Halbach array. Figure 5 (b) is the magnetic induction intensity of the double-layer structure Halbach array.

[0026] Step 4: When the air gap height is 1 mm and a horizontal thrust of 3 N is given, the thrust ripple waveform is as shown in Figure 6 (a). The no-load back electromotive force waveform generated by moving the permanent magnet at a constant speed of 1 m / s without passing current is as shown in Figure 6 (b). The solid line is the double-layer structure Halbach array, and the dashed line is the original Halbach array.

[0027] It can be illustrated by the simulation waveforms that Figure 5The distortion of the waveform of the double-layer structure is significantly smaller than that of the original Halbach, and the waveform is closer to the sine and cosine curves. Except Figure 6 that the thrust constant of the double-layer structure in (c) is slightly lower than that of the original Halbach, Figure 6 the thrust fluctuation generated by the double-layer structure in (a) and Figure 6 the no-load back electromotive force amplitude in (b) are both smaller than those of the original Halbach array. Therefore, the double-layer structure array of the present invention can effectively improve the operation stability and speed-up performance of the Halbach array.

[0028] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A Halbach permanent magnet array with a double - layer structure, characterized in that: S1. The permanent magnet array is divided into upper and lower layers. The upper layer is a rectangular permanent magnet array, and the lower layer is a trapezoidal permanent magnet array; S2. The upper - layer rectangular permanent magnet array is arranged periodically in the horizontal direction. Every four permanent magnets form a group, and the magnetization directions are up, right, down, and left in sequence; among them, the permanently magnetized magnets in the up - and - down directions are the main permanent magnets, and those in the left - and - right directions are the secondary permanent magnets. All rectangular permanent magnets have the same height, the main permanent magnets have the same width, and the secondary permanent magnets have the same width; S3. The lower - layer trapezoidal permanent magnet array is an isosceles trapezoidal structure. The upper base has the same width as the upper - layer rectangular permanent magnets. The regular trapezoids and the inverted trapezoids are arranged alternately in the horizontal direction, and the magnetization direction is the same as that of the corresponding rectangular permanent magnets in the upper layer. All trapezoidal permanent magnets have the same height, the main permanent magnets have the same size, and the secondary permanent magnets have the same size; S4. The double - layer - structure permanent magnet array is symmetrically and periodically distributed. The length of a single period is L, the total height of the rectangle and the trapezoid is L / 4, the width of the upper - layer rectangular main permanent magnet is a, the height is c, and the lower - base width of the lower - layer trapezoidal main permanent magnet is b.

2. The double - layer - structure Halbach permanent magnet array according to claim 1, characterized in that: The width of the upper - layer rectangular secondary permanent magnet is L / 2 - a, and the height is c.

3. The double - layer - structure Halbach permanent magnet array according to claim 1, characterized in that: The upper - base width of the lower - layer trapezoidal main permanent magnet is a, the height is L / 4 - c, the upper - base width of the trapezoidal secondary permanent magnet is L / 2 - a, the lower - base width is L / 2 - b, and the height is L / 4 - c.

4. The double - layer - structure Halbach permanent magnet array according to claim 1, characterized in that: The value range of the width a of the rectangular main permanent magnet is [0, L / 2], the value range of the height c is [0, L / 4], and the value range of the lower - base width b of the trapezoidal main permanent magnet is [0, L / 2].

5. The double - layer - structure Halbach permanent magnet array according to claim 1, characterized in that: When a < b, the lower - layer trapezoidal main permanent magnet is a regular trapezoid, and the secondary permanent magnet is an inverted trapezoid; when a > b, the lower - layer trapezoidal main permanent magnet is an inverted trapezoid, and the secondary permanent magnet is a regular trapezoid; when a = b, the lower - layer trapezoidal permanent magnet degenerates into a rectangle.

6. The double - layer - structure Halbach permanent magnet array according to claim 1, characterized in that: The permanent magnet array is applied to the mover of a planar motor. By multi - objective optimization, the parameters a = 6mm, b = 18mm, and c = 8mm are selected to achieve a reduction in thrust ripple, a decrease in the amplitude of the no - load back - electromotive force, and an optimization of the thrust constant.

7. The double - layer - structure Halbach permanent magnet array according to claim 1, characterized in that: In the magnetic - field distribution of the permanent magnet array, the magnetic induction intensity in the horizontal direction is sinusoidally distributed, and in the vertical direction is cosinusoidally distributed, and the harmonic content is lower than that of the traditional Halbach array.

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