Vertical-movement short-stroke ultra-precision positioning platform

Abstract

The invention provides a short-stroke ultra-precision positioning platform capable of moving vertically, and belongs to the technical field of manufacturing of micro positioning structure devices. According to the novel Lorentz force motor, an air-gap magnetic field similar to a hyperbolic curve shape is generated through a four-quadrant permanent magnet array structural form of the rotor assembly, the effect of reducing electromagnetic thrust fluctuation is achieved, a controlled motor controls linear changes of current and electromagnetic thrust, the control difficulty of a positioning platform is reduced, and the positioning precision is improved; the novel magnetic bearing adopts an unequal-width Halbach stator structure, the capability of gathering magnetic lines towards the rotor permanent magnets is enhanced, the radial component of an air-gap magnetic field is improved, the suspension force of the magnetic bearing is further increased, and the rigidity of the suspension force is reduced by adopting unequal widths of the permanent magnets and increasing the axial air gaps between the axial and radial magnetizing permanent magnets. And the positioning precision and low-frequency vibration isolation performance of the positioning platform are improved. According to the invention, nano-scale positioning of the positioning platform in a millimeter-scale motion stroke under high speed and high acceleration can be realized.

Description

Technical Field

[0001] The invention relates to a short-stroke ultra-precision positioning platform for vertical movement, belonging to the technical field of manufacturing microscopic positioning structure devices. Background Art

[0002] As an important part of intelligent manufacturing, ultra-precision machining and manufacturing technology is widely used in high-end CNC machine tools, semiconductor chip processing equipment, biotechnology and other fields. As one of the key equipment for ultra-precision machining, the short-stroke ultra-precision positioning platform for vertical motion is an important condition for achieving efficient machining and production.

[0003] Short-stroke ultra-precision positioning platforms are usually driven by piezoelectric ceramics, electrostrictive, magnetostrictive materials or Lorentz force motors. Among them, solid-state drives represented by piezoelectric ceramics, electrostrictive and magnetostrictive have the advantages of nanometer-level positioning accuracy and high resolution, and their typical strokes are in the range of tens to hundreds of microns. However, compared with Lorentz force motors, they also have obvious limitations: first, the stroke is more limited, and it is difficult to meet applications that require a larger stroke; second, these materials generally have nonlinear and hysteresis effects, and are prone to heat generation and cause thermal drift, requiring complex control algorithms to compensate, which increases the difficulty of control; in addition, their load-bearing capacity is usually weak, the driving voltage is high (especially piezoelectric ceramics), and they are more sensitive to the use environment. There are also challenges in terms of long-term life and reliability.

[0004] The Lorentz force motor uses the Lorentz force generated by the energized coil in a constant magnetic field as the driving force of the positioning platform. The stator component has no iron core structure and has the advantages of simple structure, fast dynamic response, no cogging torque, high linearity, etc. The magnetic bearing uses the interaction between permanent magnets to offset the mass of the moving parts of the positioning platform, reduce the driving current of the Lorentz force motor, reduce the copper loss of the motor and the increase in the ambient temperature, and has the advantages of no friction, no noise, simple control, and adaptability to vacuum environments. However, the existing Lorentz force motors and magnetic bearings have the problems of large electromagnetic thrust fluctuations and large suspension force stiffness, respectively, which affect the positioning accuracy and low-frequency vibration isolation performance of the positioning platform. The present invention relates to a new structure Lorentz force motor and a new structure magnetic bearing applied to a short-stroke ultra-precision positioning platform for vertical motion, which can realize nano-level positioning of the positioning platform at high speed and high acceleration within a millimeter-level motion stroke. Summary of the invention

[0005] The purpose of the present invention is to solve the problems existing in the above-mentioned prior art and to provide a short-stroke ultra-precision positioning platform for vertical movement.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] A short-stroke ultra-precision positioning platform for vertical motion, comprising: a new Lorentz force motor and a new magnetic bearing;

[0008] The specific structure includes: a Lorentz force motor assembly, a magnetic bearing assembly, a Lorentz force motor mover and a magnetic bearing mover connection piece, a support base, a support column, a support top plate, an air-floating shaft, an air-floating sleeve, an air-floating sleeve and a magnetic bearing mover connection piece, a load plate installation transition piece, a load plate and a grating assembly;

[0009] The Lorentz force motor assembly and the magnetic bearing assembly are connected through the Lorentz force motor mover and the magnetic bearing mover connector. The magnetic bearing assembly is arranged on the support base. The support base is connected to the support top plate through the support column. The air-floating sleeve is arranged on the air-floating shaft. The air-floating sleeve and the magnetic bearing assembly are connected through the air-floating sleeve and the magnetic bearing mover connector. The load plate is connected to the air-floating sleeve through the load plate installation transition piece and the air-floating sleeve and the magnetic bearing mover connector. The grating assembly includes: a grating scale, a grating scale connector, a reading head and a reading head connector. The grating scale and the grating scale connector of the grating assembly are installed on the support column, and the reading head and the reading head connector are connected to the air-floating sleeve.

[0010] The Lorentz force motor assembly and the magnetic bearing assembly are connected through the Lorentz force motor mover and the magnetic bearing mover connector. The stator assembly of the magnetic bearing assembly is arranged on the support base. The support base is connected to the support top plate through the support column. The air-floating sleeve is arranged on the air-floating shaft. The air-floating sleeve and the mover assembly of the magnetic bearing assembly are connected through the air-floating sleeve and the magnetic bearing mover connector. The load plate is connected to the magnetic bearing mover connector and the air-floating sleeve through the load plate installation transition piece and the air-floating sleeve. The grating assembly includes: a grating scale, a grating scale connector, a reading head and a reading head connector. The grating scale and the grating scale connector of the grating assembly are installed on the support column, and the reading head and the reading head connector are connected to the air-floating sleeve.

[0011] The motor mover assembly is composed of motor mover permanent magnets distributed in the direction of 45° in four quadrants and a motor mover yoke with a magnetic conductivity function. The motor mover permanent magnets are magnetized along the thickness direction using a rectangular structure. The permanent magnet fixing block is pressed onto two motor mover permanent magnets and connected to the mover yoke by bolts to press the motor mover permanent magnets. The above structure includes four permanent magnet fixing blocks respectively pressed onto the motor mover permanent magnets distributed in four directions.

[0012] The magnetic bearing assembly includes two parts, namely, a stator assembly and a mover assembly. The stator assembly includes: a stator inner ring radial permanent magnet, a stator inner ring axial permanent magnet, a stator inner ring frame, a stator outer ring radial permanent magnet, a stator outer ring axial permanent magnet, a stator outer ring frame and a stator base. In the stator assembly, two stator inner ring radial permanent magnets and one stator inner ring axial permanent magnet are fixed to the stator inner ring frame by structural adhesive, two stator outer ring radial permanent magnets and one stator outer ring axial permanent magnet are fixed to the stator outer ring frame by structural adhesive, and the stator inner ring frame and the stator outer ring frame are fixed to the stator base by bolts.

[0013] The mover assembly includes: a mover base, a mover coil, a mover permanent magnet and a mover frame; the mover permanent magnet in the mover assembly is fixed to the mover frame by structural adhesive, the two mover coils are fixed to the mover frame by a winding machine, and the mover frame is fixed to the mover base by bolts.

[0014] Furthermore, the permanent magnet of the motor rotor is made of neodymium iron boron N35.

[0015] Furthermore, the motor rotor yoke is made of electrical pure iron.

[0016] Furthermore, the permanent magnets in the magnetic bearing assembly are all made of neodymium iron boron N35.

[0017] Furthermore, the novel Lorentz force motor has a smaller electromagnetic thrust fluctuation with the vertical motion displacement, which can improve the positioning accuracy of the positioning platform. The formula of the electromagnetic thrust and the vertical motion displacement of the novel Lorentz force motor is as follows. Since the air gap magnetic field of the structure is close to linear distribution, that is, k3=0, the electromagnetic thrust generated by the novel Lorentz force motor is almost unaffected by the vertical motion displacement Δz;

[0018]

[0019] The air gap magnetic field B y The expression is:

[0020] B y =k1·z+k3·z 3

[0021] Among them, k1 and k3 are the polynomial fitting coefficients of the air gap magnetic field, and z is the vertical position;

[0022] J p is the coil current density, l pm is the effective length of the coil, h c1 、h c2 are the upper and lower boundary heights of the runway coil, w c1 、w c2 are the left and right boundary widths of the runway coil respectively, and Δz is the vertical motion displacement of the rotor of the Lorentz force motor.

[0023] Furthermore, the novel magnetic bearing has a smaller suspension force stiffness with vertical motion displacement, which can improve the positioning accuracy and low-frequency vibration isolation performance of the positioning platform; the formula of the suspension force and vertical motion displacement of the novel magnetic bearing is as follows:

[0024]

[0025] The expressions of J1 and J2 are as follows:

[0026]

[0027] The suspension force stiffness of the magnetic bearing is the rate of change of the vertical displacement of the suspension force follower assembly, and the expression is:

[0028]

[0029] Where r is the radial position, z is the axial position, is the suspension force of the new magnetic bearing, and Δz is the vertical displacement of the magnetic bearing.

[0030] J1 and J2 are the equivalent current densities of the upper and lower sides of the permanent magnet of the mover under the equivalent current method, R(1) and R(2) are the inner and outer diameters of the permanent magnet of the mover, respectively. r-sec is the radial component of the magnetic flux density of the magnetic bearing stator assembly in space, 2H is the height of the permanent magnet of the mover, μ r is the relative magnetic permeability of the permanent magnet, M s is the coercive force of the permanent magnet, H av1 , H av2 are the average magnetic field strengths of the attractive half-zone and repulsive half-zone of the permanent magnet of the mover, respectively.

[0031] Furthermore, the novel magnetic bearing adopts a non-uniform-width Halbach stator structure, and according to the requirements of suspension force and suspension force stiffness, the suspension force size and suspension force stiffness are adjusted by adjusting the structural parameters of the height and width of the axially magnetized permanent magnets and the height and width of the radially magnetized permanent magnets and the size of the air gap between all permanent magnets in the stator assembly (including: radial permanent magnets in the inner ring of the stator, axial permanent magnets in the inner ring of the stator, radial permanent magnets in the outer ring of the stator, and axial permanent magnets in the outer ring of the stator);

[0032] The beneficial effects of the present invention are:

[0033] The present invention provides a short-stroke ultra-precision positioning platform for vertical movement, and provides a new Lorentz force motor and a new magnetic bearing. The above-mentioned has advantages in the ultra-precision positioning platform, namely, smaller electromagnetic force fluctuation and smaller suspension force stiffness, so that the positioning platform has higher positioning accuracy and vibration isolation performance.

[0034] The novel Lorentz force motor of the present invention generates an air gap magnetic field shaped like a hyperbola through the four-quadrant permanent magnet array structure of the mover assembly, which has the effect of reducing the electromagnetic thrust fluctuation, making the controlled motor control current and electromagnetic thrust change linearly, greatly reducing the control difficulty of the positioning platform and improving the positioning accuracy.

[0035] The novel magnetic bearing of the present invention adopts a non-uniform-width Halbach stator structure, which enhances the ability of the magnetic lines of force to gather toward the permanent magnet of the mover, increases the radial component of the air gap magnetic field, and thus increases the magnitude of the suspension force of the magnetic bearing, so that it has a smaller suspension force stiffness within the vertical motion displacement while generating a larger suspension force. And according to the requirements of the suspension force and suspension force stiffness, the suspension force magnitude and suspension force stiffness can be adjusted more flexibly by adjusting the height and width of the axially magnetized permanent magnet of the stator permanent magnet, the height and width of the radially magnetized permanent magnet, and the size of the air gap between the two and other structural parameters.

[0036] Two annular coils are added to the radially magnetized permanent magnets of the rotor assembly of the novel magnetic bearing of the present invention. According to the linear distribution characteristics of the coil current and the dynamic suspension force, the synthetic suspension force can be increased and the stiffness of the synthetic suspension force can be reduced by adjusting the coil current at different vertical motion positions.

[0037] The present invention relates to a new structure Lorentz force motor and a new structure magnetic bearing applied to a short-stroke ultra-precision positioning platform for vertical motion, which can realize nanometer-level positioning of the positioning platform at high speed and high acceleration within a millimeter-level motion stroke. The vertical motion short-stroke ultra-precision positioning platform with the new structure Lorentz force motor and magnetic bearing is used in combination with a composite nonlinear feedback anti-disturbance control (NAM-CNFADRC) algorithm based on a nominal auxiliary model. In specific experimental tests, a reading head with a resolution of 10nm can achieve a maximum steady-state error of 20nm within a ±2mm motion stroke. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 The figure is a schematic structural diagram of a short-stroke ultra-precision positioning platform for vertical motion according to the present invention.

[0039] Figure 2 The schematic diagram of the structure of a novel Lorentz force motor for a short-stroke ultra-precision positioning platform for vertical motion according to the present invention.

[0040] Figure 3 This is a schematic diagram of the structure of a novel magnetic bearing for a short-stroke ultra-precision positioning platform for vertical motion according to the present invention.

[0041] Figure 4 This is a partial enlarged view of the grating component of a short-stroke ultra-precision positioning platform for vertical movement of the present invention.

[0042] Figure 5 It is a two-dimensional schematic diagram of a novel Lorentz force motor of a short-stroke ultra-precision positioning platform for vertical motion according to the present invention.

[0043] Figure 6 The figure is a schematic diagram of the magnetic field distribution of a novel Lorentz force motor of a short-stroke ultra-precision positioning platform for vertical motion according to the present invention.

[0044] Figure 7 The present invention is a schematic diagram of the air gap magnetic field and electromagnetic thrust of a novel Lorentz force motor of a short-stroke ultra-precision positioning platform for vertical motion along with vertical motion displacement.

[0045] Figure 8 It is a two-dimensional schematic diagram of a novel magnetic bearing of a short-stroke ultra-precision positioning platform for vertical motion according to the present invention.

[0046] Fig. 9 This is a schematic diagram of the magnetic field distribution of a new type of magnetic bearing of a short-stroke ultra-precision positioning platform for vertical motion in the present invention.

[0047] Fig.10 The present invention is a schematic diagram of the suspension force and suspension force stiffness of a novel magnetic bearing of a short-stroke ultra-precision positioning platform for vertical motion along with vertical motion displacement.

[0048] Fig.11 The figure is a schematic diagram of the steady-state error of a short-stroke ultra-precision positioning platform for vertical motion in accordance with the present invention in combination with a composite nonlinear feedback active disturbance rejection control (NAM-CNFADRC) algorithm based on a nominal auxiliary model.

[0049] The reference numerals in the figure are Lorentz force motor assembly 1, motor stator base 1-1, motor stator support rod 1-2, motor stator coil 1-3, motor stator coil frame 1-4, motor mover yoke 1-5, motor mover permanent magnet 1-6 and permanent magnet fixing block 1-7, magnetic bearing assembly 2, mover base 2-1, mover coil 2-2, mover permanent magnet 2-3, mover frame 2-4, stator inner ring radial permanent magnet 2-5, stator inner ring axial permanent magnet 2-6, stator inner ring frame 2-7, stator Outer ring radial permanent magnet 2-8, stator outer ring axial permanent magnet 2-9, stator outer ring frame 2-10, stator base 2-11, Lorentz force motor rotor and magnetic bearing rotor connector 3, support base 4, support column 5, support top plate 6, air floating shaft 7, air floating sleeve 8, air floating sleeve and magnetic bearing rotor connector 9, load plate mounting transition piece 10, load plate 11, grating assembly 12, including grating scale 12-1, grating scale connector 12-2, reading head 12-3, reading head connector 12-4. DETAILED DESCRIPTION

[0050] The present invention will be further described in detail below in conjunction with the accompanying drawings: This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method is given, but the protection scope of the present invention is not limited to the following embodiments.

[0051] like Figures 1 to 11 As shown, the present embodiment involves a short-stroke ultra-precision positioning platform for vertical motion, comprising:

[0052] The purpose of this invention is to design a new structural form of Lorentz force motor and a new structural form of magnetic bearing to be applied to a short-stroke ultra-precision positioning platform for vertical motion. The electromagnetic thrust fluctuation generated by the Lorentz force motor directly affects the positioning accuracy of the positioning platform. According to Newton's second law F=ma and the formula for uniformly accelerated linear motion A simple calculation shows that when the system is an open-loop system, if the load mass m is 2.5kg, the motor thrust fluctuation F is 10mN, and the thrust action time t is 10ms, then the deviation s between the actual position and the planned position is 200nm, and the positioning accuracy will not reach the nanometer level. Therefore, sufficiently small electromagnetic thrust fluctuations can achieve ultra-high precision positioning. The suspension force stiffness generated by the magnetic bearing affects the low-frequency vibration isolation performance of the positioning platform, and the natural frequency of the positioning platform The suspension stiffness K of the magnetic bearing is z The smaller the suspension force The larger it is, the smaller the natural frequency of the system is, and the better the low-frequency vibration isolation performance is. Fig.10 As shown, it can be seen that the average suspension force is 25.84N, the maximum suspension force stiffness is 75N / m, and the natural frequency of the positioning platform is Compared with traditional magnetic bearings, it has a smaller natural frequency. Therefore, when a new structure of Lorentz force motor and magnetic bearing is designed with small electromagnetic thrust fluctuation and suspension force stiffness, the positioning accuracy and low-frequency vibration isolation performance of the positioning platform can be improved.

[0053] Example 1

[0054] The present invention designs a new structural form of Lorentz force motor and a new structural form of magnetic bearing based on the goal of small electromagnetic thrust fluctuation and small suspension force stiffness, and applies them to a short-stroke ultra-precision positioning platform for vertical motion. The system composition of the short-stroke ultra-precision positioning platform for vertical motion: Lorentz force motor assembly 1, magnetic bearing assembly 2, Lorentz force motor mover and magnetic bearing mover connector 3, support base 4, support column 5, support top plate 6, air floating shaft 7, air floating sleeve 8, air floating sleeve and magnetic bearing mover connector 9, load plate installation transition piece 10, load plate 11 and grating assembly 12; grating assembly 12 includes 12-1 grating scale, 12-2 grating scale connector, 12-3 reading head, 12-4 reading head connector.

[0055] like Figure 1As shown, the Lorentz force motor assembly 1 and the magnetic bearing assembly 2 are connected through the Lorentz force motor rotor and the magnetic bearing rotor connector 3, the stator assembly of the magnetic bearing assembly 2 is arranged on the support base 4, the support base 4 is connected to the support top plate 6 through the support column 5, the air floating sleeve 8 is arranged on the air floating shaft 7, the air floating sleeve 8 and the rotor assembly of the magnetic bearing assembly 2 are connected through the air floating sleeve and the magnetic bearing rotor connector 9, the load disk 11 is connected to the air floating sleeve 8 through the load disk installation transition piece 10 and the air floating sleeve and the magnetic bearing rotor connector 9, the grating assembly 12 includes: a grating scale 12-1, a grating scale connector 12-2, a reading head 12-3 and a reading head connector 12-4; the grating scale 12-1 and the grating scale connector 12-2 of the grating assembly 12 are installed on the support column 5, and the reading head 12-3 and the reading head connector 12-4 are connected to the air floating sleeve 8;

[0056] like Figure 2 As shown, the Lorentz force motor assembly 1 includes two parts: a motor stator assembly and a motor mover assembly; the motor stator assembly includes: a motor stator base 1-1, a motor stator support rod 1-2, a motor stator coil 1-3 and a motor stator coil frame 1-4; the motor stator assembly is distributed with two runway-type motor stator coils 1-3, the two runway-type motor stators 1-3 are wound onto the motor stator coil frame 1-4 by a winding machine, the motor stator coil frame 1-4 is connected to the motor stator support rod 1-2 by bolts, and the motor stator support rod 1-2 is connected to the motor stator base 1-1 by bolts;

[0057] The motor mover assembly is composed of motor mover permanent magnets 1-6 distributed in the direction of 45° in four quadrants and a motor mover yoke 1-5 with a magnetic conductivity function. The motor mover permanent magnets 1-6 are magnetized in the thickness direction using a rectangular structure. The permanent magnet fixing blocks 1-7 are pressed onto the two motor mover permanent magnets 1-6 and connected to the mover yoke 1-5 by bolts to press the motor mover permanent magnets 1-6. The above structure includes four permanent magnet fixing blocks 1-7 respectively pressed onto the motor mover permanent magnets 1-6 distributed in four directions.

[0058] like Figure 3As shown, the magnetic bearing assembly 2 includes two parts, a stator assembly and a mover assembly. The stator assembly includes: a stator inner ring radial permanent magnet 2-5, a stator inner ring axial permanent magnet 2-6, a stator inner ring frame 2-7, a stator outer ring radial permanent magnet 2-8, a stator outer ring axial permanent magnet 2-9, a stator outer ring frame 2-10 and a stator base 2-11; two stator inner ring radial permanent magnets 2-5 and one stator inner ring axial permanent magnet 2-6 in the stator assembly are fixed to the stator inner ring frame 2-7 by structural glue, two stator outer ring radial permanent magnets 2-8 and one stator outer ring axial permanent magnet 2-9 are fixed to the stator outer ring frame 2-10 by structural glue, and the stator inner ring frame 2-7 and the stator outer ring frame 2-10 are fixed to the stator base 2-11 by bolts;

[0059] The mover assembly includes: a mover base 2-1, a mover coil 2-2, a mover permanent magnet 2-3 and a mover frame 2-4; the mover permanent magnet 2-3 in the mover assembly is fixed to the mover frame 2-4 by structural adhesive, the two mover coils 2-2 are fixed to the mover frame 2-4 by a winding machine, and the mover frame 2-4 is fixed to the mover base 2-1 by bolts.

[0060] The short-stroke ultra-precision positioning platform for vertical motion uses the vertical Lorentz force generated by the Lorentz force motor to provide driving force to drive the load plate to move up and down. In order to reduce the driving current of the Lorentz force motor, a magnetic bearing is used to generate a vertical constant suspension force to compensate for the motion mass of the moving parts of the positioning platform. In the present invention, an air bearing is used to provide constraints on the X and Y horizontal directions of the positioning platform, so that the positioning platform can only move vertically along the single degree of freedom in the Z direction, and the use of non-contact air bearings instead of traditional mechanical bearings can improve the positioning accuracy of the positioning platform, reduce mechanical friction, and increase service life. In order to achieve ultra-high precision positioning of the positioning platform, the present invention uses a high-precision, low-expansion coefficient indium steel ruler in conjunction with a high-speed and high-resolution reading head to form a feedback system.

[0061] The stator assembly of the new Lorentz force motor is distributed with two racetrack-shaped coils, and the rotor assembly is composed of permanent magnets distributed in the four quadrants at 45° and a magnetic yoke with a magnetic conductivity function. The permanent magnets are of rectangular structure and magnetized along the thickness direction. This new Lorentz force motor obtains a hyperbolic air gap magnetic field by distributing permanent magnets in the four quadrants, effectively reducing the change of the Lorentz force generated by the energized coil with the moving position, reducing the thrust fluctuation caused by the change of the relative position of the stator and the rotor, making the controlled motor control current and electromagnetic thrust change linearly, greatly reducing the control difficulty of the positioning platform and improving the positioning accuracy.

[0062] like Figure 5 and Figure 6As shown in the figure, the working principle of the new structure Lorentz force motor is that the energized coil conductor generates Lorentz force in the constant magnetic field generated by the permanent magnet. The size and direction of the Lorentz force motor can be changed by adjusting the size and direction of the coil current. The effective magnetic field of the new Lorentz force motor starts from the N poles of permanent magnets No. 1 and No. 3 respectively, passes through the air gap, reaches the S poles of permanent magnets No. 2 and No. 4, and then passes through the magnetic yoke and returns to the S poles of permanent magnets No. 1 and No. 3, forming a closed loop, in which the effective magnetic field passing through the stator coil and the energized coil generate electromagnetic thrust.

[0063] According to the magnetic field distribution of the new Lorentz force motor, it can be obtained that the air gap magnetic field and the vertical motion displacement show an approximately linear change law, and its expression is:

[0064] B y (y,z)=k1·z+k3·z 3

[0065] Among them, k1 and k3 are the polynomial fitting coefficients of the air gap magnetic field, and z is the vertical position.

[0066] Therefore, the electromagnetic thrust expression obtained by the two track coil stators within the vertical motion range is:

[0067]

[0068] Among them J p is the coil current density, l pm is the effective length of the coil, h c1 、h c2 are the heights of the upper and lower sides of the runway coil, w c1 、w c2 are the left and right widths of the runway coil respectively, and Δz is the vertical motion displacement of the rotor of the Lorentz force motor.

[0069] It can be seen from the formula that under ideal conditions, when k3 = 0, that is, when the air gap magnetic field is completely linearly distributed, the electromagnetic thrust generated by the energized coil is The electromagnetic thrust is not affected by the motion displacement Δz. The air gap magnetic field generated by the new Lorentz force motor in the present invention is closer to linear change than the traditional structure Lorentz force motor, and can provide a driving force with smaller electromagnetic thrust fluctuation for the positioning platform.

[0070] The thrust fluctuation of the Lorentz force motor is defined as the ratio of the difference between the maximum electromagnetic thrust and the minimum electromagnetic thrust within the vertical motion range and the average electromagnetic thrust within the motion range:

[0071]

[0072] like Figure 7 As shown, the electromagnetic thrust fluctuation is calculated using the formula It has smaller electromagnetic thrust fluctuation than the traditional structure Lorentz force motor;

[0073] The motor rotor permanent magnet 1-6 is made of neodymium iron boron N35, which has a large magnetic energy product. The motor rotor yoke 1-5 is made of electrical pure iron, which has good magnetic conductivity, so that it can generate a large air gap magnetic field in the spatial position. In addition, this new Lorentz force motor obtains a hyperbola-shaped air gap magnetic field by distributing permanent magnets evenly in four quadrants, which effectively reduces the change of the Lorentz force generated by the energized coil with the moving position, reduces the thrust fluctuation caused by the change of the relative position of the stator and the mover, and makes the controlled motor control current and electromagnetic thrust change linearly, greatly reducing the control difficulty of the positioning platform and improving the positioning accuracy.

[0074] The new magnetic bearing consists of two parts: a stator assembly and a mover assembly. The stator assembly is composed of a Halbach array of permanent magnets with unequal widths, including an inner ring and an outer ring, each of which consists of two radially magnetized permanent magnets, one axially magnetized permanent magnet, and a stator frame. The Halbach array permanent magnets in the stator assembly enhance the ability of the magnetic lines of force to gather toward the mover permanent magnets, increase the radial component of the air gap magnetic field, and thus increase the suspension force of the magnetic bearing. The use of unequal widths of permanent magnets and increasing the axial air gap between axially magnetized permanent magnets and radially magnetized permanent magnets is used to reduce the size of the suspension force stiffness. The mover assembly consists of a radially magnetized permanent magnet, two annular symmetrically distributed coils, and a mover frame.

[0075] The working principle of the new magnetic bearing follows the objective law that like polarities repel and opposite polarities attract. The two radial permanent magnet rings on the upper layer of the stator attract the permanent magnet ring of the rotor, the two radial permanent magnets on the lower layer of the stator repel the permanent magnet ring of the rotor, and the axial permanent magnets on the middle layer of the stator also attract the permanent magnet ring of the rotor. Therefore, when the stator assembly is fixed, the rotor assembly is subjected to a vertical upward static suspension force. Two annular coils are added to the rotor assembly of the new magnetic bearing. The rotor assembly will generate a dynamic suspension force in the vertical direction under the action of the synthetic air gap magnetic field generated by all permanent magnets of the stator and the rotor and the energized annular coil of the rotor. The magnitude and direction of the dynamic suspension force can be adjusted by adjusting the current size and direction of the coil, which is used to increase or decrease the size of the synthetic suspension force and realize the effect of dynamic suspension force compensation and reducing the stiffness of the synthetic suspension force.

[0076] like Figure 8 and Fig. 9As shown in the figure, the effective magnetic field of the new magnetic bearing starts from the N pole of permanent magnet No. 1, passes through the axial air gap to permanent magnet No. 2 and permanent magnet No. 3, then starts from permanent magnet No. 3 and passes through the radial air gap to permanent magnet No. 6, then passes through the axial permanent magnet to permanent magnet No. 5 and permanent magnet No. 4, and finally passes through the radial air gap to the S pole of permanent magnet No. 1, forming a closed loop. The radial magnetic field passing through the mover assembly acts on the mover permanent magnet to generate a vertical upward suspension force. The new magnetic bearing uses a Halbach array of permanent magnets, which adds four radially magnetized permanent magnets to participate compared to traditional magnetic bearings, enhancing the ability of magnetic lines to gather toward the mover permanent magnets, increasing the radial component of the air gap magnetic field, and thus increasing the suspension force of the magnetic bearing.

[0077] The calculation formulas for the static suspension force and suspension stiffness of the new magnetic bearing are as follows:

[0078]

[0079] The expressions of J1 and J2 are as follows:

[0080]

[0081] The suspension force stiffness of the magnetic bearing is defined as the rate of change of the vertical displacement of the suspension force follower assembly, and the expression is:

[0082]

[0083] Where r is the radial position, z is the axial position, is the suspension force of the new magnetic bearing, and Δz is the vertical displacement of the magnetic bearing.

[0084] J1 and J2 are the equivalent current densities of the upper and lower sides of the permanent magnet of the mover under the equivalent current method, R(1) and R(2) are the inner and outer diameters of the permanent magnet of the mover, respectively. r-sec is the radial component of the magnetic flux density of the magnetic bearing stator assembly in space, 2H is the height of the permanent magnet of the mover, μ r is the relative magnetic permeability of the permanent magnet, M s is the coercive force of the permanent magnet, H av1 , H av2 are the average magnetic field strengths of the attractive half-zone and repulsive half-zone of the permanent magnet of the mover, respectively.

[0085] This embodiment relates to a new structure Lorentz force motor and a new structure magnetic bearing applied to a short-stroke ultra-precision positioning platform for vertical motion, which can achieve nanometer-level positioning of the positioning platform at high speed and high acceleration within a millimeter-level motion range. Fig.11As shown, the vertical motion short-stroke ultra-precision positioning platform with the new structure Lorentz force motor and magnetic bearing is used, in conjunction with the nominal auxiliary model-based composite nonlinear feedback self-disturbance rejection control (NAM-CNFADRC) algorithm. In specific experimental tests, a 10nm resolution reading head is used to achieve a maximum steady-state error of 20nm within a ±2mm motion stroke.

[0086] The above are only preferred specific embodiments of the present invention, which are all different implementations based on the overall concept of the present invention, and the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A short-stroke ultra-precision positioning platform for vertical motion, characterized in that: include: New Lorentz force motors and new magnetic bearings; The specific structure includes: a Lorentz force motor assembly (1), a magnetic bearing assembly (2), a Lorentz force motor mover and a magnetic bearing mover connecting member (3), a support base (4), a support column (5), a support top plate (6), an air-floating shaft (7), an air-floating shaft sleeve (8), an air-floating shaft sleeve and a magnetic bearing mover connecting member (9), a load plate mounting transition member (10), a load plate (11) and a grating assembly (12); The Lorentz force motor assembly (1) and the magnetic bearing assembly (2) are connected via a Lorentz force motor mover and a magnetic bearing mover connector (3); the stator assembly of the magnetic bearing assembly (2) is arranged on a support base (4); the support base (4) and a support top plate (6) are connected via a support column (5); an air-floating shaft sleeve (8) is arranged on an air-floating shaft (7); the air-floating shaft sleeve (8) and a mover assembly of the magnetic bearing assembly (2) are connected via an air-floating shaft sleeve and a magnetic bearing mover connector (9); a load plate (11) is arranged on the load plate The transition piece (10) and the air-floating sleeve are connected to the magnetic bearing mover connecting piece (9) and the air-floating sleeve (8); the grating assembly (12) comprises: a grating ruler (12-1), a grating ruler connecting piece (12-2), a reading head (12-3) and a reading head connecting piece (12-4); the grating ruler (12-1) and the grating ruler connecting piece (12-2) of the grating assembly (12) are installed on the support column (5), and the reading head (12-3) and the reading head connecting piece (12-4) are connected to the air-floating sleeve (8); The Lorentz force motor assembly (1) comprises two parts: a motor stator assembly and a motor mover assembly; the motor stator assembly comprises: a motor stator base (1-1), a motor stator support rod (1-2), a motor stator coil (1-3) and a motor stator coil frame (1-4); the motor stator assembly is provided with two runway-shaped motor stator coils (1-3); the two runway-shaped motor stators (1-3) are wound onto the motor stator coil frame (1-4) by a winding machine; the motor stator coil frame (1-4) is connected to the motor stator support rod (1-2) by bolts; the motor stator support rod (1-2) is connected to the motor stator base (1-1) by bolts; The motor mover assembly is composed of motor mover permanent magnets (1-6) distributed in four quadrants at 45° and a motor mover yoke (1-5) with a magnetic conductivity function. The motor mover permanent magnets (1-6) are magnetized in a thickness direction using a rectangular structure. A permanent magnet fixing block (1-7) is pressed onto two motor mover permanent magnets (1-6) and connected to the mover yoke (1-5) by bolts to press the motor mover permanent magnets (1-6). The structure includes four permanent magnet fixing blocks (1-7) respectively pressed onto the motor mover permanent magnets (1-6) distributed in four directions. The magnetic bearing assembly (2) comprises two parts, namely a stator assembly and a mover assembly. The stator assembly comprises: a stator inner ring radial permanent magnet (2-5), a stator inner ring axial permanent magnet (2-6), a stator inner ring frame (2-7), a stator outer ring radial permanent magnet (2-8), a stator outer ring axial permanent magnet (2-9), a stator outer ring frame (2-10) and a stator base (2-11); in the stator assembly, two stator inner ring radial permanent magnets (2-5) and one stator inner ring axial permanent magnet (2-6) are fixed to the stator inner ring frame (2-7) by structural adhesive, two stator outer ring radial permanent magnets (2-8) and one stator outer ring axial permanent magnet (2-9) are fixed to the stator outer ring frame (2-10) by structural adhesive, and the stator inner ring frame (2-7) and the stator outer ring frame (2-10) are fixed to the stator base (2-11) by bolts; The mover assembly comprises: a mover base (2-1), a mover coil (2-2), a mover permanent magnet (2-3) and a mover frame (2-4); in the mover assembly, the mover permanent magnet (2-3) is fixed to the mover frame (2-4) by means of structural adhesive, two mover coils (2-2) are fixed to the mover frame (2-4) by means of a winding machine, and the mover frame (2-4) is fixed to the mover base (2-1) by means of bolts.

2. A short-stroke ultra-precision positioning platform for vertical motion according to claim 1, characterized in that: The motor rotor permanent magnet (1-6) is made of neodymium iron boron N35.

3. The short-stroke ultra-precision positioning platform for vertical motion according to claim 1, characterized in that: The motor mover yoke (1-5) is made of electrical pure iron.

4. The short-stroke ultra-precision positioning platform for vertical motion according to claim 1, characterized in that: The permanent magnets in the magnetic bearing assembly (2) are all made of neodymium iron boron N35.

5. The short-stroke ultra-precision positioning platform for vertical motion according to claim 1, characterized in that: The novel Lorentz force motor has a smaller electromagnetic thrust fluctuation with the vertical motion displacement, which can improve the positioning accuracy of the positioning platform. The formula of the electromagnetic thrust and the vertical motion displacement of the novel Lorentz force motor is as follows. Since the air gap magnetic field of the structure is close to linear distribution, that is, k3=0, the electromagnetic thrust generated by the novel Lorentz force motor is almost unaffected by the vertical motion displacement Δz; The air gap magnetic field B y The expression is: B y =k1·z+k3·z 3 Among them, k1 and k3 are the polynomial fitting coefficients of the air gap magnetic field, and z is the vertical position; J p is the coil current density, l pm is the effective length of the coil, h c1 、h c2 are the upper and lower boundary heights of the runway coil, w c1 、w c2 are the left and right boundary widths of the runway coil respectively, and Δz is the vertical motion displacement of the rotor of the Lorentz force motor.

6. The short-stroke ultra-precision positioning platform for vertical motion according to claim 1, characterized in that: The novel magnetic bearing has a smaller suspension force stiffness with vertical motion displacement, which can improve the positioning accuracy and low-frequency vibration isolation performance of the positioning platform; the formula of the suspension force and vertical motion displacement of the novel magnetic bearing is as follows: The expressions of J1 and J2 are as follows: The suspension force stiffness of the magnetic bearing is the rate of change of the vertical displacement of the suspension force follower assembly, and the expression is: Where r is the radial position, z is the axial position, is the suspension force of the new magnetic bearing, Δz is the vertical displacement of the magnetic bearing; J1 and J2 are the equivalent current densities of the upper and lower sides of the permanent magnet of the mover under the equivalent current method, R(1) and R(2) are the inner and outer diameters of the permanent magnet of the mover, respectively. r-sec is the radial component of the magnetic flux density of the magnetic bearing stator assembly in space, 2H is the height of the permanent magnet of the mover, μ r is the relative magnetic permeability of the permanent magnet, M s is the coercive force of the permanent magnet, H av1 , H av2 are the average magnetic field strengths of the attractive half-zone and repulsive half-zone of the permanent magnet of the mover, respectively.

7. The short-stroke ultra-precision positioning platform for vertical motion according to claim 1, characterized in that: The novel magnetic bearing adopts a non-uniform-width Halbach stator structure, and adjusts the suspension force and suspension force stiffness according to the suspension force and suspension force stiffness requirements by adjusting the structural parameters of the axially magnetized permanent magnet height and width, the radially magnetized permanent magnet height and width, and the air gap size between the two in the stator assembly.

Images