CN114114093B - Device and method for positioning center of magnetic field of pulse magnet - Google Patents

Device and method for positioning center of magnetic field of pulse magnet Download PDF

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CN114114093B
CN114114093B CN202210098212.2A CN202210098212A CN114114093B CN 114114093 B CN114114093 B CN 114114093B CN 202210098212 A CN202210098212 A CN 202210098212A CN 114114093 B CN114114093 B CN 114114093B
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magnetic field
positioning
axis
stepping motor
moving
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CN114114093A (en
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韩小涛
魏文琦
刘沁莹
袁乐
万昊
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Huazhong University of Science and Technology
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    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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Abstract

The invention discloses a device and a method for positioning the center of a pulse magnet magnetic field, wherein the positioning device comprises an alternating current source, a measuring rod, a positioning control module, a stepping motor guide rail module and a stepping motor driver; the pulse magnet generates an alternating magnetic field with stable amplitude and frequency; the measuring rod is used for sensing alternating magnetic fields at different spatial positions in real time and generating an induced voltage signal; the stepping motor guide rail module is used for controlling the measuring rod to move in the space range of the pulse magnet magnetic field according to the driving signal; the positioning control module is used for acquiring induced voltage signals output by the measuring coils at different pulse magnet magnetic field space positions in real time, processing the induced voltage signals according to a positioning algorithm and then outputting control instruction signals for controlling the movement of the stepping motor; the stepping motor driver is used for outputting a driving signal according to the control instruction signal. The invention can quickly and accurately control the measuring coil to be positioned at the center of the magnetic field of the pulse magnet, thereby improving the positioning precision.

Description

Device and method for positioning center of magnetic field of pulse magnet
Technical Field
The invention belongs to the technical field of magnetic field measurement, and particularly relates to a device and a method for positioning the center of a pulse magnet magnetic field.
Background
With the intensive research in the fields of condensed state physics and the like, unconventional extreme experimental conditions such as extremely low temperature, strong magnetic field, ultrahigh pressure and the like become more and more important. The pulse high-intensity magnetic field experimental device can provide extreme high-intensity magnetic field experimental conditions, and the current non-destructive pulse high-intensity magnetic field technology can realize a magnetic field with the magnetic field intensity exceeding 100T, so that the exploration and the recognition of new phenomena and new rules are facilitated.
The conventional scientific experimental sample of the pulse high-intensity magnetic field is placed in the center of the magnetic field of the pulse magnet so as to obtain a magnetic field environment with high field intensity and high uniformity. Due to the defects of the actual magnet winding process, the center of the magnetic field generated by the magnet is often not coincident with the geometric center of the magnet, so that the actual center of the magnetic field of the magnet needs to be positioned before the development of scientific experiments. The current means generally determines the magnetic field center of a magnet by multiple pulse discharges and manually adjusting the position of a magnetic field sampling coil, and has the defects of complex process, low positioning accuracy and the like.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a pulse magnet magnetic field center positioning device, aiming at solving the problem of low positioning accuracy caused by the fact that the magnetic field center generated by a pulse magnet in the prior art is not coincident with the geometric center of the magnet.
The invention provides a pulse magnet magnetic field center positioning device, which comprises: the device comprises an alternating current source, a measuring rod, a positioning control module, a stepping motor guide rail module and a stepping motor driver; the alternating current source is used for outputting sinusoidal current to the pulse magnet and adjusting the amplitude and the frequency of the sinusoidal current in real time, so that the pulse magnet can generate an alternating magnetic field with stable amplitude and frequency; the measuring rod is used for inducing the alternating magnetic fields at different spatial positions in real time under the control of the spatial position control signal and generating an induced voltage signal; the stepping motor guide rail module generates the space position control signal for controlling the measuring rod to move in the space range of the pulse magnet magnetic field according to the driving signal; the positioning control module is used for acquiring induced voltage signals output by the measuring coils at different pulse magnet magnetic field space positions in real time, processing the induced voltage signals according to a positioning algorithm and then outputting control instruction signals for controlling the movement of the stepping motor; the input end of the stepping motor driver is connected to the output end of the positioning control module and used for outputting the driving signal according to the control instruction signal.
Still further, the measuring rod includes: the measuring coil is used for sensing the alternating magnetic fields at different spatial positions in real time and generating induced voltage signals; the framework is used for fixing the measuring coil.
Still further, the step motor guide rail module comprises: the device comprises an x-axis moving module, a y-axis moving module and a z-axis moving module; the x-axis moving module is used for controlling the measuring rod to move along the x-axis direction, the y-axis moving module is used for controlling the measuring rod to move along the y-axis direction, and the z-axis moving module is used for controlling the measuring rod to move along the z-axis direction.
Still further, the x-axis moving module includes: the first stepping motor, the first ball screw and the first guide rail platform; the y-axis moving module includes: the second stepping motor, a second ball screw and a second guide rail platform; the z-axis moving module includes: a third step motor, a third ball screw and a third guide rail platform; the first stepping motor is connected with a first ball screw, the first ball screw is connected with a first guide rail platform, and the first guide rail platform is connected with the y-axis moving module; the first stepping motor is used for realizing controllable rotation of a first ball screw, and the first ball screw realizes linear motion of the first guide rail platform; the second stepping motor is connected with a second ball screw, the second ball screw is connected with a second guide rail platform, and the second guide rail platform is connected with the z-axis moving module; the second stepping motor is used for realizing controllable rotation of a second ball screw, and the second ball screw realizes linear motion of the second guide rail platform; the third stepping motor is connected with a third ball screw, the third ball screw is connected with a third guide rail platform, and the third guide rail platform is connected with a framework in the measuring rod; the third stepping motor is used for realizing controllable rotation of a third ball screw, and the third ball screw realizes linear motion of a third guide rail platform.
Still further, the positioning control module includes: the device comprises an analog input unit, a controller and a digital output unit; the input end of the analog input unit is connected with the magnetic field measuring coil and is used for acquiring alternating magnetic field induction voltage signals at high speed and high resolution; the input end of the controller is connected to the output end of the analog input unit and is used for processing the sampling signal in real time, obtaining a magnetic field amplitude signal with high signal-to-noise ratio and high accuracy and generating a control instruction of a stepping motor driver according to a positioning algorithm; the input end of the digital output unit is connected with the output end of the controller, the output end of the digital output unit is used as the output end of the positioning control module, and the digital output unit is used for accurately outputting a control instruction of a stepping motor driver.
Furthermore, the alternating magnetic field induced voltage signal collected by the analog input unit is:
Figure 218167DEST_PATH_IMAGE001
whereinB m Is the magnitude of the magnetic field and,fis the frequency of the magnetic field and,
Figure 298118DEST_PATH_IMAGE002
in order to shift the phase of the signal,Nthe number of turns of the coil,SIs the coil area,RIs a coil resistance,LIs a coil inductor,CIs a capacitance of the coil and is,R g is the input resistance of the analog input unit.
Further, the localization algorithm is based on the currently obtained signal amplitude Vm(k) And previous data Vm(k-1) comparing, calculating to obtain the moving direction and distance of the stepping motor, and generating a control instruction; wherein the signal amplitude VmFitting mode by adopting least square method
Figure 651739DEST_PATH_IMAGE003
Is obtained in whichfIn order to induce the frequency of the voltage signal,
Figure 449931DEST_PATH_IMAGE002
is a phase shift.
The invention also provides a method for positioning the center of the pulsed magnet magnetic field based on the pulsed magnet magnetic field center positioning device, which comprises an x-axis direction positioning step, a y-axis direction positioning step and a z-axis direction positioning step;
the x-axis direction positioning step specifically comprises:
SX 1: setting an initial value nx=0、kx=0；
SX 2: let kx=kx+1，And according to the set moving step length Lx(nx) To a set moving direction Dx(nx) Move once so that the position of the measuring coil becomes (x (k))x)=x(kx-1)+Lx(nx)*Dx(nx) 0,0), the magnetic field amplitude V at the current position is detectedm(kx)；
Judging the currently detected magnetic field amplitude Vm(kx) Whether or not it is smaller than the last detected magnetic field amplitude Vm(kx-1), if yes, repeat SX2 step, otherwise go to step SX 3;
SX 3: let n bex=nx+1 and resetting the moving step length Lx(nx)=Lx(nx-1)/2, resetting the direction of movement Dx(nx)=-Dx(nx-1)；
Judging the reset moving step length Lx(nx) Whether it is greater than a set step threshold LTxIf so, the process is carried out according to the step SX2, otherwise, the positioning in the x-axis direction is finished, and the positioning position (x (k) of the x-axis of the magnetic field center of the magnet is obtainedx)，0，0)；
The y-axis direction positioning step specifically comprises:
SY 1: setting an initial value ny=0、ky=0；
SY 2: let ky=ky+1, and moving by a set moving step length Ly(ny) To a set moving direction Dy(ny) Move once so that the position of the measuring coil becomes (0, y (k))y)=y(ky-1)+Ly(ny)*Dy(ny) 0), the current magnetic field amplitude V is detectedm(ky)；
And judging the currently detected magnetic field amplitude Vm(ky) Whether or not it is smaller than the last detected magnetic field amplitude Vm(ky-1), if yes, continuing to repeat the SY2 step, otherwise entering a step SY 3;
SY 3: let n bey=ny+1 and resetting the moving step length to Ly(ny)=Ly(ny-1)/2Resetting the moving direction to Dy(ny)=-Dy(ny-1)；
Judging the reset moving step length Ly(ny) Whether it is greater than a set step threshold LTyIf so, the method proceeds according to a step SY2, otherwise, the positioning in the y-axis direction is finished, and a positioning position (0, y (k) of the y-axis of the magnetic field center of the magnet is obtainedy)，0)；
The z-axis direction positioning step specifically comprises:
SZ 1: setting an initial value nz=0、kz=0；
SZ 2: let kz=kz+1, and moving by a set moving step length Lz(nz) To a set moving direction Dz(nz) Move once so that the position of the measuring coil becomes (0,0, z (k)z)=z(kz-1)+Lz(nz)*Dz(nz) Detect the current magnetic field amplitude V)m(kz)；
Judging the currently detected magnetic field amplitude Vm(kz) Whether or not it is greater than the last detected magnetic field amplitude Vm(kz-1), if yes, continuing to repeat step SZ2, otherwise entering step SZ 3;
SZ 3: let n bez=nz+1 and resetting the moving step length to Lz(nz)=Lz(nz-1)/2, resetting the moving direction to Dz(nz)=-Dz(nz-1)；
Judging the reset moving step length Lz(nz) Whether it is greater than a set step threshold LTzIf so, the positioning is carried out according to the step SZ2, otherwise, the positioning in the z-axis direction is finished, and the positioning position (0,0, z (k) of the center z-axis of the magnetic field of the magnet is obtainedz))。
Still further, the step threshold LTxShould not exceed one third of the x-axis positioning error requirement; the step threshold LTyShould not exceed one third of the y-axis positioning error requirement; the step threshold LTzShould not exceed one third of the z-axis positioning error requirement.
According to the invention, the positioning control module is adopted to adjust the control instruction in real time according to the induction voltage signals acquired at different positions in real time, and the stepping motor is used to control the real-time position of the measuring coil.
Drawings
FIG. 1 is a schematic structural diagram of an automatic device for centering a magnetic field of a magnet according to an embodiment of the present invention;
fig. 2 is a schematic view illustrating a connection between a stepping motor guide rail module and a measuring rod according to an embodiment of the present invention;
FIG. 3 is a flow chart of z-axis positioning steps provided by an embodiment of the present invention;
FIG. 4 is a flowchart of the x-axis positioning steps provided by an embodiment of the present invention;
FIG. 5 is a flow chart of y-axis positioning steps provided by an embodiment of the present invention;
the same reference numbers are used throughout the drawings to refer to the same components or structures, wherein: the measuring device comprises a first stepping motor 1, a first ball screw 2, a first guide rail platform 3, a second stepping motor 4, a second ball screw 5, a second guide rail platform 6, a third stepping motor 7, a third ball screw 8, a third guide rail platform 9, a framework 10 and a measuring coil 11.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The invention provides a device and a method for positioning the center of a magnetic field of a pulse magnet, which can solve the problem of low positioning accuracy caused by the fact that the center of the magnetic field generated by the pulse magnet is not coincident with the geometric center of the magnet in the prior art.
Fig. 1 shows a structure of a device for positioning the magnetic field center of a pulsed magnet according to an embodiment of the present invention, and for convenience of description, only the parts related to the embodiment of the present invention are shown, and the details are as follows:
the pulse magnet magnetic field center positioning device comprises: the device comprises an alternating current source, a measuring rod, a positioning control module, a stepping motor guide rail module and a stepping motor driver;
the output end of the alternating current source is connected with the pulse magnet and is used for outputting sinusoidal current to the pulse magnet and adjusting the amplitude and the frequency of the sinusoidal current in real time, so that the pulse magnet can generate an alternating magnetic field with stable amplitude and frequency;
the measuring rod comprises a measuring coil and a framework, wherein the measuring coil is used for measuring an alternating magnetic field according to a Faraday electromagnetic induction principle and inducing the alternating magnetic field at different spatial positions in real time to generate an induced voltage signal;
the framework is used for fixing the measuring coil;
the output end of the stepping motor guide rail module is connected with the framework and used for controlling the measuring rod to move in the space range of the pulse magnet magnetic field according to the driving signal;
the input end of the positioning control module is used for receiving the induced voltage signals output by the measuring coil, and the positioning control module is used for acquiring the induced voltage signals output by the measuring coil at different pulse magnet magnetic field space positions in real time, processing the induced voltage signals according to a positioning algorithm and then outputting control instruction signals for controlling the movement of the stepping motor;
the input end of the stepping motor driver is connected to the output end of the positioning control module and used for outputting the driving signal according to the control instruction signal.
The alternating current source is connected with the electrodes of the pulse magnet and provides sinusoidal alternating current with a certain constant amplitude and frequency for the pulse magnet so as to generate a sinusoidal alternating magnetic field with the constant amplitude and frequency. The alternating current source provides current in the form of:
Figure 914410DEST_PATH_IMAGE004
whereinI m In order to be the magnitude of the current,fis the current frequency. The magnetic field form generated by the magnet under the action of the current form is as follows:
Figure 848868DEST_PATH_IMAGE005
whereinB m Is the magnetic field amplitude.
Wherein, measuring coil in the measuring stick can adopt the coiling of multiturn wire, measures alternating magnetic field according to Faraday electromagnetic induction principle, produces high repeatability and high sensitivity induced voltage signal, and the open circuit induced voltage signal that magnetic field measuring coil measured and obtained is:
Figure 373390DEST_PATH_IMAGE006
whereinNThe number of turns of the coil,SIs the coil area,RIs a coil resistance,LIs a coil inductor,CIs a coil capacitor,
Figure 393299DEST_PATH_IMAGE007
Is a phase shift; when the output current frequency of the AC current source is selected to be
Figure 661469DEST_PATH_IMAGE008
Then, the open circuit induction voltage amplitude with the highest sensitivity can be obtained
Figure 716013DEST_PATH_IMAGE009
。
And a coil framework 10 in the measuring rod is used for connecting the stepping motor guide rail module and fixing a measuring coil 11.
As shown in fig. 2, in the embodiment of the present invention, the stepping motor guide module includes: the device comprises an x-axis moving module, a y-axis moving module and a z-axis moving module, wherein the x-axis moving module is used for controlling the measuring rod to move along the x-axis direction, the y-axis moving module is used for controlling the measuring rod to move along the y-axis direction, and the z-axis moving module is used for controlling the measuring rod to move along the z-axis direction.
Wherein, the x-axis moving module includes: the first stepping motor 1 can controllably rotate the first ball screw 2; the first ball screw 2 is connected in the first guide rail platform 3 to realize the linear motion of the first guide rail platform 3; the first rail platform 3 is connected to the y-axis moving module.
The y-axis moving module includes: the second stepping motor 4 is used for realizing controllable rotation of the second ball screw 5; the second ball screw 5 is connected in the second guide rail platform 6 to realize the linear motion of the second guide rail platform 6; the second rail stage 6 is connected to the z-axis moving module.
The z-axis moving module includes: a third step motor 7, a third ball screw 8 and a third guide rail platform 9, wherein the third step motor 7 realizes the controllable rotation of the third ball screw 8; the third ball screw 8 is connected in the third guide rail platform 9 to realize the linear motion of the third guide rail platform; and the third guide rail platform is connected with the measuring rod framework.
In an embodiment of the present invention, the positioning control module includes: the device comprises an analog input unit, a controller and a digital output unit, wherein the analog input unit is connected with a magnetic field measuring coil and the controller and is used for acquiring alternating magnetic field induced voltage signals at high speed and high resolution and inputting sampling signals into the controller, and the analog input unit acquires the alternating magnetic field induced voltage signals as follows:
Figure 411436DEST_PATH_IMAGE010
whereinR g In order to simulate the input resistance of the input cell,
Figure 184220DEST_PATH_IMAGE011
is a phase shift; when in useR g The larger the signal is, the higher the sensitivity of sampling the alternating magnetic field induced voltage signal is, and in order to realize high-sensitivity measurement, the analog input unit is a high-input impedance ADC. The controller is connected with the analog input unit and the digital output unit, processes the sampling signal in real time, obtains a magnetic field amplitude signal with high signal-to-noise ratio and high accuracy, and generates a control instruction of the stepping motor driver according to a positioning algorithm. In order to improve the signal-to-noise ratio of the magnetic field amplitude signal, the signal average is adopted for the signal of one period for n times, and the signal-to-noise ratio
Figure 724923DEST_PATH_IMAGE012
After signal averaging, the signal-to-noise ratio is improved compared with before signal averaging
Figure 899553DEST_PATH_IMAGE013
And (4) doubling. In order to avoid signal amplitude deviation caused by sampling errors, a least square fitting mode is adopted
Figure 500298DEST_PATH_IMAGE014
Obtain the signal amplitude Vm. The positioning algorithm is based on the currently obtained signal amplitude Vm(k) And previous data VmAnd (k-1) comparing, calculating to obtain the moving direction and distance of the stepping motor, and generating a control command. And the digital output unit is connected with the controller and the stepping motor driver and is used for accurately outputting a control instruction of the stepping motor driver.
The stepping motor driver is connected with the positioning control module, receives the control instruction signal and sequentially drives the first stepping motor, the second stepping motor and the third stepping motor to move according to the control instruction.
In the pulse magnet center positioning device provided by the embodiment of the invention, the positioning control module is adopted to adjust the control instruction in real time according to the induction voltage signals acquired at different positions in real time, and the stepping motor is used for controlling the real-time position of the measuring coil.
The invention also provides a pulse magnet magnetic field center positioning method, which comprises the following steps: establishing an x-axis, y-axis and z-axis rectangular coordinate system by taking the geometric center of the pulse magnet as an origin, wherein the z-axis is along the axial direction of the magnet, the x-axis and the y-axis are respectively along the orthogonal direction of the radial plane of the magnet, and the coordinate of the geometric center of the magnet is (0,0, 0);
the x-axis direction positioning method specifically comprises the following steps:
SX 1: setting an initial value nx=0、kx=0；nxMoving steps for measuring movement of coil along x-axisNumber of changes of length and direction of movement, kxIs the number of moves; the measuring coil position is (x (k)x) 0,0), where x (k)x) Denotes the kthxAnd measuring the x-axis coordinate of the coil after the secondary movement, and if the radius of the inner hole of the magnet is R, considering that the radial distance of the magnetic field center of the magnet, which deviates from the geometric center, does not exceed R/2, and selecting the initial position x (0) of the measuring coil as R/2. Let n bexThe moving step length of x-axis movement of the secondary measuring coil is Lx(nx) Considering the set value of the moving step length to be larger first and smaller second is favorable for reducing the moving times kxIf the positioning time is shortened, the initial moving step length L can be setx(0) Is R/4, nxThe decrease in the step size of the move when increasing may be set to Lx(nx)=Lx(nx-1)/2, provided thatxThe moving direction of the x-axis movement of the secondary positioning device is Dx(nx) When it is positive in the x-axis direction, Dx(nx) =1, D when negative x-axis orientationx(nx) = -1, since x (0) is set to positive value, initial moving direction D is setx(0) Is-1. Let the moving step threshold be LTxIn order to achieve both the rapidity and the accuracy of the positioning, the step threshold LTxOptionally R/40; detecting the magnitude V of the magnetic field at the initial positionm(0) And proceeds as in step SX 2.
SX 2: let kx=kx+1, and according to the set moving step length Lx(nx) To a set moving direction Dx(nx) Move once so that the position of the measuring coil becomes (x (k))x)=x(kx-1)+Lx(nx)*Dx(nx) 0,0), the magnetic field amplitude V at the current position is detectedm(kx)；
Judging the currently detected magnetic field amplitude Vm(kx) Whether or not it is smaller than the last detected magnetic field amplitude Vm(kx-1), if yes, repeat SX2 step, otherwise go to step SX 3;
SX 3: let n bex=nx+1 and resetting the moving step length Lx(nx)=Lx(nx-1)/2, resetting the direction of movement Dx(nx)=-Dx(nx-1)；
Judging the reset moving step length Lx(nx) Whether it is greater than a set step threshold LTxIf so, the process is carried out according to the step SX2, otherwise, the positioning in the x-axis direction is finished, and the positioning position (x (k) of the x-axis of the magnetic field center of the magnet is obtainedx) 0, 0); with a maximum positioning error of
Figure 760378DEST_PATH_IMAGE015
3LTx。
The y-axis direction positioning step specifically comprises the following steps:
SY 1: setting an initial value ny=0、ky=0；nyFor measuring the step length of the movement and the number of changes in the direction of movement, k, of the y-axis movement of the coilyIs the number of moves; the measurement coil position is (0, y (k)y) 0), wherein y (k)y) Denotes the kthyAnd if the radius of the inner hole of the magnet is R and the radial distance of the magnetic field center of the magnet, which deviates from the geometric center, does not exceed R/2, the y-axis coordinate of the positioning device after the secondary movement is selected as R/2. Let n beyThe moving step length of the y-axis movement of the secondary positioning device is Ly(ny) Considering the set value of the moving step length to be larger first and smaller second is favorable for reducing the moving times kyIf the positioning time is shortened, the initial moving step length L can be sety(0) Is R/4, nyThe decrease in the step size of the move when increasing may be set to Ly(ny)=Ly(ny-1)/2, provided thatyThe moving direction of the y-axis movement of the secondary positioning device is Dy(ny) When it is in the positive y-axis direction, Dy(ny) =1, D when negative y-axis directiony(ny) = -1, since y (0) is set to a positive value, initial moving direction D is sety(0) Is-1. Let the moving step threshold be LTyIn order to achieve both the rapidity and the accuracy of the positioning, the step threshold LTyOptionally R/40. Detecting the magnitude V of the magnetic field at the initial positionm(0) And is carried out according to step SY 2;
SY 2: let ky=ky+1, and move according to the settingStep length Ly(ny) To a set moving direction Dy(ny) Move once so that the position of the measuring coil becomes (0, y (k))y)=y(ky-1)+Ly(ny)*Dy(ny) 0), the current magnetic field amplitude V is detectedm(ky)；
And judging the currently detected magnetic field amplitude Vm(ky) Whether or not it is smaller than the last detected magnetic field amplitude Vm(ky-1), if yes, continuing to repeat the SY2 step, otherwise entering a step SY 3;
SY 3: let n bey=ny+1 and resetting the moving step length to Ly(ny)=Ly(ny-1)/2, resetting the moving direction to Dy(ny)=-Dy(ny-1)；
Judging the reset moving step length Ly(ny) Whether it is greater than a set step threshold LTyIf so, the method proceeds according to a step SY2, otherwise, the positioning in the y-axis direction is finished, and a positioning position (0, y (k) of the y-axis of the magnetic field center of the magnet is obtainedy) 0); with a maximum positioning error of
Figure 373281DEST_PATH_IMAGE015
3LTy。
The z-axis direction positioning method specifically comprises the following steps:
SZ 1: setting an initial value nz=0、kz=0；nzFor measuring the step length of the movement and the number of changes in the direction of the movement of the z-axis of the coil, kzFor the number of movements, the position of the measuring coil is (0,0, z (k)z) Wherein z (k)z) Denotes the kthzAnd the z-axis coordinate of the positioning device after the secondary movement is determined, if the geometric height of the magnet is H, and the axial distance of the center of the magnetic field of the magnet, which is deviated from the geometric center, is not more than H/10, the initial position z (0) of the positioning device can be selected to be H/10. Let n bezThe moving step length of the z-axis movement of the secondary positioning device is Lz(nz) Considering the set value of the moving step length to be larger first and smaller second is favorable for reducing the moving times kzShortening the positioning time, the initial movement can be setStep length L of movementz(0) Is H/20, nzThe decrease in the step size of the move when increasing may be set to Lz(nz)=Lz(nz-1)/2, provided thatzThe moving direction of the z-axis movement of the secondary positioning device is Dz(nz) When it is the positive direction of z-axis, Dz(nz) =1, D when negative in the z-axisz(nz) = -1, since z (0) is set to a positive value, initial moving direction D is setz(0) Is-1. Let the moving step threshold be LTzIn order to achieve both the rapidity and the accuracy of the positioning, the step threshold LTzOptionally H/400. Detecting the magnitude V of the magnetic field at the initial positionm(0) And is carried out according to step SZ 2;
SZ 2: let kz=kz+1, and moving by a set moving step length Lz(nz) To a set moving direction Dz(nz) Move once so that the position of the measuring coil becomes (0,0, z (k)z)=z(kz-1)+Lz(nz)*Dz(nz) Detect the current magnetic field amplitude V)m(kz)；
Judging the currently detected magnetic field amplitude Vm(kz) Whether or not it is greater than the last detected magnetic field amplitude Vm(kz-1), if yes, continuing to repeat step SZ2, otherwise entering step SZ 3;
SZ 3: let n bez=nz+1 and resetting the moving step length to Lz(nz)=Lz(nz-1)/2, resetting the moving direction to Dz(nz)=-Dz(nz-1)；
Judging the reset moving step length Lz(nz) Whether it is greater than a set step threshold LTzIf so, the positioning is carried out according to the step SZ2, otherwise, the positioning in the z-axis direction is finished, and the positioning position (0,0, z (k) of the center z-axis of the magnetic field of the magnet is obtainedz) Maximum positioning error of)
Figure 402417DEST_PATH_IMAGE015
3LTz。
Wherein the step threshold LTxShould not exceed one third of the x-axis positioning error requirement; step threshold LTyShould not exceed one third of the y-axis positioning error requirement; step threshold LTzShould not exceed one third of the z-axis positioning error requirement.
The positioning steps in the x, y and z axis directions can be carried out in any order, and finally the coordinate of the magnetic field center of the magnet is (x (k)x)
Figure 439643DEST_PATH_IMAGE015
3LTx，y(ky)
Figure 921440DEST_PATH_IMAGE015
3LTy，z(kz)
Figure 69524DEST_PATH_IMAGE015
3LTz）。
Generally, compared with the prior art, the above technical solution conceived by the present invention has the following beneficial effects: the magnetic field center positioning process is automatic, and the manual operation cost is reduced; the time consumption for positioning the magnetic field center is short, and the positioning precision is high; the device has high compatibility and is suitable for different types of magnets; the system has simple structure and is easy to realize.
To further illustrate the device and method for positioning the magnetic field center of a pulsed magnet according to embodiments of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
in the embodiment of the invention, an x-axis, y-axis and z-axis rectangular coordinate system is established by taking the geometric center of the magnet as an origin, wherein the z-axis is along the axial direction of the magnet, the x-axis and the y-axis are along the orthogonal direction of the radial plane of the magnet, the coordinate of the geometric center of the magnet is (0,0,0), and the spatial distribution of the magnetic field generated by the pulse magnet in the geometric center area is approximately:
Figure 953167DEST_PATH_IMAGE016
wherein the content of the first and second substances,
Figure 161294DEST_PATH_IMAGE017
the direction of the main magnetic field is represented as the direction of a z axis and changes along with the changes of space coordinates x, y, z and time t; the coefficients S1 and S2 are proportional to S3 and the magnet supply current, and vary with the change in current, and since the magnet supply current is a sinusoidal alternating current in this embodiment, the coefficients S1, S2 and S3 sinusoidally alternate with time.
By
Figure 130387DEST_PATH_IMAGE018
It can be seen that the magnetic field amplitude in the z-axis direction is in the plane z = z0There is a maximum; in the direction of the x-axis, the magnetic field amplitude is in the plane x = x0There is a minimum value; in the y-axis direction, the magnetic field amplitude is in the plane y = y0There is a minimum value. Ideally, the geometric center of the magnet coincides with the center of the magnetic field generated by the magnet, i.e., x0=y0=z0=0, magnetic field center coordinates are (0,0, 0); due to the defects of the magnet winding process, the center of the magnetic field generated by the magnet is (x)0，y0，z0)。
Based on the space distribution of the magnetic field of the pulse magnet, the invention provides a method for positioning the center of the magnetic field of the pulse magnet, which comprises the following steps:
as shown in fig. 3, the step of positioning in the z-axis direction includes:
SZ 1: setting the moving step length and the changing times of the moving direction of the z-axis movement of the positioning device as nzThe number of movements is kzSetting an initial value nz=0、kzAnd = 0. The setting position of the positioning device is (0,0, z (k)z) Wherein z (k)z) Denotes the kthzAnd the z-axis coordinate of the positioning device after the secondary movement is determined, if the geometric height of the magnet is H, and the axial distance of the center of the magnetic field of the magnet, which is deviated from the geometric center, is not more than H/10, the initial position z (0) of the positioning device can be selected to be H/10. Let n bezThe moving step length of the z-axis movement of the secondary positioning device is Lz(nz) Considering the set value of the moving step length to be larger first and smaller second is favorable for reducing the moving times kzIf the positioning time is shortened, the initial moving step length L can be setz(0) Is H/20, nzIncreasing time shiftThe reduction of the moving step length can be set to Lz(nz)=Lz(nz-1)/2, provided thatzThe moving direction of the z-axis movement of the secondary positioning device is Dz(nz) When it is the positive direction of z-axis, Dz(nz) =1, D when negative in the z-axisz(nz) = -1, since z (0) is set to a positive value, initial moving direction D is setz(0) Is-1. Let the moving step threshold be LTzIn order to achieve both the rapidity and the accuracy of the positioning, the step threshold LTzOptionally H/400. Detecting the magnitude V of the magnetic field at the initial positionm(0) And is carried out according to step SZ 2;
SZ2：kz=kz+1, according to the set moving step length Lz(nz) To a set moving direction Dz(nz) Moving once, the positioner position becomes (0,0, z (k)z)=z(kz-1)+Lz(nz)*Dz(nz) Detect the current magnetic field amplitude V)m(kz) If the currently detected magnetic field amplitude V is presentm(kz) Greater than the last detected field amplitude Vm(kz-1), the step of SZ2 is repeated again, if the currently detected magnetic field amplitude V is presentm(kz) Less than or equal to the last detected magnetic field amplitude Vm(kz-1), then according to step SZ 3;
SZ3：nz=nz+1, resetting the moving step length to Lz(nz)=Lz(nz-1)/2, resetting the moving direction to Dz(nz)=-Dz(nz-1) if the set movement step length L is setz(nz) Greater than a set step threshold LTzThen, according to step SZ2, if the set moving step is less than or equal to the set threshold LTzThen, the positioning in the z-axis direction is finished, and the positioning position (0,0, z (k) of the center z-axis of the magnetic field of the magnet is obtainedz) Maximum positioning error of)
Figure 816583DEST_PATH_IMAGE019
3LTz。
As shown in fig. 4, the step of positioning in the x-axis direction includes:
SX 1: setting the moving step length and the changing times of the moving direction of the x-axis movement of the positioning device as nxThe number of movements is kxSetting an initial value nx=0、kxAnd = 0. The setting position is (x (k)x) 0,0), where x (k)x) Denotes the kthxAnd (4) selecting the x-axis coordinate of the positioning device after the secondary movement as R/2 if the radius of the inner hole of the magnet is R and the radial distance of the magnetic field center of the magnet, which deviates from the geometric center, is not more than R/2. Let n bexThe moving step length of the x-axis movement of the secondary positioning device is Lx(nx) Considering the set value of the moving step length to be larger first and smaller second is favorable for reducing the moving times kxIf the positioning time is shortened, the initial moving step length L can be setx(0) Is R/4, nxThe decrease in the step size of the move when increasing may be set to Lx(nx)=Lx(nx-1)/2, provided thatxThe moving direction of the x-axis movement of the secondary positioning device is Dx(nx) When it is positive in the x-axis direction, Dx(nx) =1, D when negative x-axis orientationx(nx) = -1, since x (0) is set to positive value, initial moving direction D is setx(0) Is-1. Let the moving step threshold be LTxIn order to achieve both the rapidity and the accuracy of the positioning, the step threshold LTxOptionally R/40. Detecting the magnitude V of the magnetic field at the initial positionm(0) And according to step SX 2;
SX2：kx=kx+1, according to the set moving step length Lx(nx) To a set moving direction Dx(nx) Once moved, the positioner position becomes (x (k))x)=x(kx-1)+Lx(nx)*Dx(nx) 0,0), the current magnetic field amplitude V is detectedm(kx) If the currently detected magnetic field amplitude V is presentm(kx) Less than the last detected field amplitude Vm(kx-1), the SX2 step is repeated again, if the currently detected magnetic field amplitude V is presentm(kx) Greater than or equal to the last detected magnetic field amplitude Vm(kx-1)，Then it is done as step SX 3;
SX3：nx=nx+1, resetting the moving step length to Lx(nx)=Lx(nx-1)/2, resetting the moving direction to Dx(nx)=-Dx(nx-1) if the set movement step length L is setx(nx) Greater than a set step threshold LTxThen, according to step SX2, if the set moving step is less than or equal to the set threshold LTxThen, the positioning in the x-axis direction is finished, and the positioning position (x (k)) of the x-axis of the magnetic field center of the magnet is obtainedx) 0,0) with a maximum positioning error of
Figure 820311DEST_PATH_IMAGE019
3LTx。
As shown in fig. 5, the step of positioning in the y-axis direction includes:
SY 1: setting the moving step length and the changing times of the moving direction of the y-axis movement of the positioning device as nyThe number of movements is kySetting an initial value ny=0、kyAnd = 0. The setting position is (0, y (k)y) 0), wherein y (k)y) Denotes the kthyAnd if the radius of the inner hole of the magnet is R and the radial distance of the magnetic field center of the magnet, which deviates from the geometric center, does not exceed R/2, the y-axis coordinate of the positioning device after the secondary movement is selected as R/2. Let n beyThe moving step length of the y-axis movement of the secondary positioning device is Ly(ny) Considering the set value of the moving step length to be larger first and smaller second is favorable for reducing the moving times kyIf the positioning time is shortened, the initial moving step length L can be sety(0) Is R/4, nyThe decrease in the step size of the move when increasing may be set to Ly(ny)=Ly(ny-1)/2, provided thatyThe moving direction of the y-axis movement of the secondary positioning device is Dy(ny) When it is in the positive y-axis direction, Dy(ny) =1, D when negative y-axis directiony(ny) = -1, since y (0) is set to a positive value, initial moving direction D is sety(0) Is-1. Let the moving step threshold be LTyTo achieve the same purposeConsidering the rapidity and accuracy of positioning, the step threshold LTyOptionally R/40. Detecting the magnitude V of the magnetic field at the initial positionm(0) And is carried out according to step SY 2;
SY2：ky=ky+1, according to the set moving step length Ly(ny) To a set moving direction Dy(ny) Moving once, the positioner position becomes (0, y (k)y)=y(ky-1)+Ly(ny)*Dy(ny) 0), the current magnetic field amplitude V is detectedm(ky) If the currently detected magnetic field amplitude V is presentm(ky) Less than the last detected field amplitude Vm(ky-1), the SY2 step is repeated continuously if the currently detected magnetic field amplitude V is presentm(ky) Greater than or equal to the last detected magnetic field amplitude Vm(ky-1), then according to step SY 3;
SY3：ny=ny+1, resetting the moving step length to Ly(ny)=Ly(ny-1)/2, resetting the moving direction to Dy(ny)=-Dy(ny-1) if the set movement step length L is sety(ny) Greater than a set step threshold LTyThen it is proceeded as step SY2 if the set moving step is less than or equal to the set threshold LTyThen the positioning in the y-axis direction is finished, and the positioning position (0, y (k)) of the y-axis of the magnetic field center of the magnet is obtainedy) 0), with a maximum positioning error of
Figure 199340DEST_PATH_IMAGE019
3LTy。
The positioning steps in the x, y and z axis directions can be carried out in any order, and finally the coordinate of the magnetic field center of the magnet is (x (k)x)
Figure 655729DEST_PATH_IMAGE019
3LTx，y(ky)
Figure 145617DEST_PATH_IMAGE019
3LTy，z(kz)
Figure 738272DEST_PATH_IMAGE019
3LTz）。
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (9)

1. A method for positioning the center of a pulse magnet magnetic field is characterized by comprising an x-axis direction positioning step, a y-axis direction positioning step and a z-axis direction positioning step;
the x-axis direction positioning step specifically comprises:
SX 1: setting an initial value nx=0、kx=0；
SX 2: let kx=kx+1, and according to the set moving step length Lx(nx) To a set moving direction Dx(nx) Move once so that the position of the measuring coil becomes (x (k))x)=x(kx-1)+Lx(nx)*Dx(nx) 0,0), the magnetic field amplitude V at the current position is detectedm(kx)；
Judging the currently detected magnetic field amplitude Vm(kx) Whether or not it is smaller than the last detected magnetic field amplitude Vm(kx-1), if yes, repeat SX2 step, otherwise go to step SX 3;
SX 3: let n bex=nx+1 and resetting the moving step length Lx(nx)=Lx(nx-1)/2, resetting the direction of movement Dx(nx)=-Dx(nx-1)；
Judging the reset moving step length Lx(nx) Whether it is greater than a set step threshold LTxIf so, the process is carried out according to the step SX2, otherwise, the positioning in the x-axis direction is finished, and the positioning position (x (k) of the x-axis of the magnetic field center of the magnet is obtainedx)，0，0)；
The y-axis direction positioning step specifically comprises:
SY 1: setting an initial value ny=0、ky=0；
SY 2: let ky=ky+1, and moving by a set moving step length Ly(ny) To a set moving direction Dy(ny) Move once so that the position of the measuring coil becomes (0, y (k))y)=y(ky-1)+Ly(ny)*Dy(ny) 0), the current magnetic field amplitude V is detectedm(ky)；
And judging the currently detected magnetic field amplitude Vm(ky) Whether or not it is smaller than the last detected magnetic field amplitude Vm(ky-1), if yes, continuing to repeat the SY2 step, otherwise entering a step SY 3;
SY 3: let n bey=ny+1 and resetting the moving step length to Ly(ny)=Ly(ny-1)/2, resetting the moving direction to Dy(ny)=-Dy(ny-1)；
Judging the reset moving step length Ly(ny) Whether it is greater than a set step threshold LTyIf so, the method proceeds according to a step SY2, otherwise, the positioning in the y-axis direction is finished, and a positioning position (0, y (k) of the y-axis of the magnetic field center of the magnet is obtainedy)，0)；
The z-axis direction positioning step specifically comprises:
SZ 1: setting an initial value nz=0、kz=0；
SZ 2: let kz=kz+1, and moving by a set moving step length Lz(nz) To a set moving direction Dz(nz) Move once so that the position of the measuring coil becomes (0,0, z (k)z)=z(kz-1)+Lz(nz)*Dz(nz) Detect the current magnetic field amplitude V)m(kz)；
Judging the currently detected magnetic field amplitude Vm(kz) Whether or not it is greater than the last detected magnetic field amplitude Vm(kz-1), if so, continuing to repeat the SZ2 stepOtherwise, entering the step SZ 3;
SZ 3: let n bez=nz+1 and resetting the moving step length to Lz(nz)=Lz(nz-1)/2, resetting the moving direction to Dz(nz)=-Dz(nz-1)；
Judging the reset moving step length Lz(nz) Whether it is greater than a set step threshold LTzIf so, the positioning is carried out according to the step SZ2, otherwise, the positioning in the z-axis direction is finished, and the positioning position (0,0, z (k) of the center z-axis of the magnetic field of the magnet is obtainedz))。
2. The pulsed magnet magnetic field center positioning method according to claim 1, characterized in that the step threshold LTxShould not exceed one third of the x-axis positioning error requirement; the step threshold LTyShould not exceed one third of the y-axis positioning error requirement; the step threshold LTzShould not exceed one third of the z-axis positioning error requirement.
3. A pulsed magnet magnetic field centering device based on the pulsed magnet magnetic field centering method according to any one of claims 1 to 2, comprising: the device comprises an alternating current source, a measuring rod, a positioning control module, a stepping motor guide rail module and a stepping motor driver;
the alternating current source is used for outputting sinusoidal current to the pulse magnet and adjusting the amplitude and the frequency of the sinusoidal current in real time, so that the pulse magnet can generate an alternating magnetic field with stable amplitude and frequency;
the measuring rod is used for inducing the alternating magnetic fields at different spatial positions in real time under the control of the spatial position control signal and generating an induced voltage signal;
the stepping motor guide rail module generates the space position control signal for controlling the measuring rod to move in the space range of the pulse magnet magnetic field according to the driving signal;
the positioning control module is used for acquiring induced voltage signals output by the measuring rods at different pulse magnet magnetic field space positions in real time, processing the induced voltage signals according to a positioning algorithm and then outputting control instruction signals for controlling the movement of the stepping motor;
the input end of the stepping motor driver is connected to the output end of the positioning control module and used for outputting the driving signal according to the control instruction signal.
4. The pulsed magnet magnetic field centering device of claim 3, wherein said measuring rod comprises: the measuring coil is used for sensing the alternating magnetic fields at different spatial positions in real time and generating induced voltage signals; the framework is used for fixing the measuring coil.
5. The pulsed magnet magnetic field centering device of claim 4, wherein the stepper motor rail module comprises: the device comprises an x-axis moving module, a y-axis moving module and a z-axis moving module;
the x-axis moving module is used for controlling the measuring rod to move along the x-axis direction, the y-axis moving module is used for controlling the measuring rod to move along the y-axis direction, and the z-axis moving module is used for controlling the measuring rod to move along the z-axis direction.
6. The pulsed magnet magnetic field centering device of claim 5, wherein the x-axis movement module comprises: the device comprises a first stepping motor (1), a first ball screw (2) and a first guide rail platform (3); the y-axis moving module includes: a second stepping motor (4), a second ball screw (5) and a second guide rail platform (6); the z-axis moving module includes: a third stepping motor (7), a third ball screw (8) and a third guide rail platform (9);
the first stepping motor (1) is connected with a first ball screw (2), the first ball screw (2) is connected with a first guide rail platform (3), and the first guide rail platform (3) is connected with a y-axis moving module; the first stepping motor (1) is used for realizing controllable rotation of the first ball screw (2), and the first ball screw (2) realizes linear motion of the first guide rail platform (3);
the second stepping motor (4) is connected with a second ball screw (5), the second ball screw (5) is connected with a second guide rail platform (6), and the second guide rail platform (6) is connected with the z-axis moving module; the second stepping motor (4) is used for realizing controllable rotation of a second ball screw (5), and the second ball screw (5) realizes linear motion of a second guide rail platform (6);
the third stepping motor (7) is connected with a third ball screw (8), the third ball screw (8) is connected with a third guide rail platform (9), and the third guide rail platform (9) is connected with a framework (10) in the measuring rod; the third stepping motor (7) is used for realizing controllable rotation of a third ball screw (8), and the third ball screw (8) realizes linear motion of a third guide rail platform (9).
7. The pulsed magnet magnetic field centering device of any one of claims 3-6, wherein said positioning control module comprises: the device comprises an analog input unit, a controller and a digital output unit;
the input end of the analog input unit is connected with the magnetic field measuring coil and is used for acquiring alternating magnetic field induction voltage signals at high speed and high resolution;
the input end of the controller is connected to the output end of the analog input unit and is used for processing the sampling signal in real time, obtaining a magnetic field amplitude signal with high signal-to-noise ratio and high accuracy and generating a control instruction of a stepping motor driver according to a positioning algorithm;
the input end of the digital output unit is connected with the output end of the controller, the output end of the digital output unit is used as the output end of the positioning control module, and the digital output unit is used for accurately outputting a control instruction of a stepping motor driver.
8. The pulsed magnet magnetic field center positioning device of claim 7, wherein the alternating magnetic field induced voltage signal collected by the analog input unit is:
Figure 929372DEST_PATH_IMAGE001
whereinB m Is the magnitude of the magnetic field and,fis the frequency of the magnetic field and,
Figure 606472DEST_PATH_IMAGE002
in order to shift the phase of the signal,Nthe number of turns of the coil,SIs the coil area,RIs a coil resistance,LIs a coil inductor,CIs a capacitance of the coil and is,R g is the input resistance of the analog input unit.
9. The apparatus of claim 7, wherein the positioning algorithm compares the current signal amplitude with the previous data to calculate the direction and distance the stepper motor needs to move and generate the control command.
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