CN116578160B - Magnetic field intensity control device - Google Patents

Magnetic field intensity control device Download PDF

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Publication number
CN116578160B
CN116578160B CN202310856606.4A CN202310856606A CN116578160B CN 116578160 B CN116578160 B CN 116578160B CN 202310856606 A CN202310856606 A CN 202310856606A CN 116578160 B CN116578160 B CN 116578160B
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magnetic field
value
driving signal
pid
digital
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CN116578160A (en
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束鹏飞
张守玉
唐有利
袁强
石致富
许克标
贺羽
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Guoyi Quantum Technology Hefei Co ltd
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Chinainstru and Quantumtech Hefei Co Ltd
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    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
    • G05F7/00—Regulating magnetic variables
    • G—PHYSICS
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
    • Y02A90/30—Assessment of water resources
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

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  • Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Automation & Control Theory (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • Measuring Magnetic Variables (AREA)

Abstract

The invention discloses a magnetic field intensity control device, which comprises: the magnetic field detection module is used for acquiring a magnetic field intensity actual measurement value of the magnetic field generated by the magnetic field generator; the PID control module is used for performing PID adjustment on a first difference value between the measured magnetic field intensity value and the initial scanning field value to obtain a first PID signal output value; the steady field DAC module includes: the first digital-to-analog conversion sub-module is used for outputting a first magnetic field driving signal according to the output value of the first PID signal; the second digital-to-analog conversion sub-module is used for outputting a second magnetic field driving signal according to the output value of the first PID signal; the first control module is used for stabilizing the magnetic field intensity of the magnetic field generated by the magnetic field generator at a scanning start value according to the first magnetic field driving signal and the second magnetic field driving signal. Therefore, the adjusting efficiency of the PID control module can be improved, the magnetic field intensity is enabled to be close to the initial value of the sweeping field rapidly, the convergence efficiency of the PID control module can be improved, and the magnetic field intensity is enabled to be stabilized near the initial value of the sweeping field rapidly.

Description

Magnetic field intensity control device
Technical Field
The invention relates to the technical field of magnetic field intensity control, in particular to a magnetic field intensity control device.
Background
Scientific research detection instruments such as EPR (Electron Paramagnetic Resonance ), ODMR (Optically Detected Magnetic Resonance, magnetic resonance), QDAFM (Quantum Diamond Atomic Force Microscope ) and the like all relate to magnetic field generation equipment and a magnetic field intensity accurate control system. The conventional magnetic field strength control system mainly comprises a DAC (Digital to Analog Converter, digital-to-analog converter) for outputting a magnetic field driving control signal, and a PID (Proportional-Integral-Derivative) first control module for adjusting the DAC signal by monitoring an actual magnetic field strength value versus a target magnetic field strength value.
Disclosure of Invention
The present invention aims to solve at least one of the technical problems in the related art to some extent. Therefore, a first object of the present invention is to provide a magnetic field strength control device, which can accelerate the adjustment efficiency of the PID control module, make the magnetic field strength rapidly approach to the start value of the sweeping field, and accelerate the convergence efficiency of the PID control module, so as to rapidly stabilize the magnetic field strength near the start value of the sweeping field, thereby improving the control precision and the stabilization efficiency of the magnetic field strength.
To achieve the above object, an embodiment of a first aspect of the present invention provides a magnetic field strength control device, including: the magnetic field detection module is used for acquiring a magnetic field intensity actual measurement value of the magnetic field generated by the magnetic field generator; the PID control module is used for calculating a first difference value between the magnetic field strength actual measurement value and the scanning initial value, and performing PID adjustment on the first difference value to obtain a first PID signal output value; the stable-field DAC module comprises a first digital-to-analog conversion sub-module, a second digital-to-analog conversion sub-module and a first control module, wherein the resolution of the first digital-to-analog conversion sub-module is larger than that of the second digital-to-analog conversion sub-module; the first PID signal output value outputs a first magnetic field driving signal through the first digital-to-analog conversion sub-module, where s1= (S/M1) '×m1, S1 is the first magnetic field driving signal, S is the first PID signal output value, M1 is the resolution of the first digital-to-analog conversion sub-module, and (S/M1)' is the rounding value of S/M1; the first PID signal output value outputs a second magnetic field driving signal through the second digital-to-analog conversion sub-module, where s2= { (S-S1)/M2 } 'x M2, S2 is the second magnetic field driving signal, M2 is the resolution of the second digital-to-analog conversion sub-module, { (S-S1)/M2 }' is the rounded value of (S-S1)/M2, and the resolution of the first magnetic field driving signal is different from the resolution of the second magnetic field driving signal; the first control module is used for controlling the magnetic field generator according to the first magnetic field driving signal and the second magnetic field driving signal so as to enable the magnetic field intensity of the magnetic field generated by the magnetic field generator to be stabilized at a scanning start value.
According to the magnetic field intensity control device provided by the embodiment of the invention, the adjusting efficiency of the PID control module can be improved, the magnetic field intensity is enabled to be fast close to the initial value of the sweeping field, the convergence efficiency of the PID control module is improved, and the magnetic field intensity is enabled to be fast stabilized near the initial value of the sweeping field, so that the magnetic field intensity control precision and the field stabilizing efficiency are improved.
In addition, the magnetic field strength control device of the embodiment of the invention can also have the following additional technical characteristics:
according to one embodiment of the present invention, the PID control module is further configured to: when the first difference value is smaller than a first preset value, setting the upper limit of the output value of the first PID signal as a first threshold value; when the first difference value is larger than or equal to a first preset value and smaller than or equal to a second preset value, setting the upper limit of the output value of the first PID signal as a second threshold value, wherein the second threshold value is larger than the first threshold value; and when the first difference value is larger than a second preset value, setting the upper limit of the output value of the first PID signal as a third threshold value, wherein the third threshold value is larger than the second threshold value.
According to one embodiment of the invention, the first digital-to-analog conversion submodule comprises a first digital-to-analog converter, the second digital-to-analog conversion submodule comprises a second digital-to-analog converter and an attenuator which are sequentially connected, and the resolution of the second digital-to-analog converter is the same as that of the first digital-to-analog converter; wherein the first PID signal output value outputs a first magnetic field driving signal through the first digital-to-analog converter, wherein S1= (S/M1) 1 )’×M1 1 ，M1 1 Is the firstResolution of a D/A converter, (S/M1) 1 ) ' S/M1 1 Is the rounding value of (2); the first PID signal output value outputs a second magnetic field driving signal through a second digital-analog converter and an attenuator which are connected in sequence, wherein S2= { (S-S1) N/M1 1 }’×M2 1 N is the attenuation multiple of the attenuator, M2 1 For the ratio of the resolution of the second D/A converter to the attenuation factor of the attenuator, { (S-S1) N/M1 1 The expression (S-S1) N/M1 1 Is a rounded value of (c).
According to one embodiment of the invention, the attenuation multiple n=d/M of the attenuator, where D is the range of the second digital-to-analog converter.
According to one embodiment of the invention, the first PID signal output value outputs a signal value through the second digital-to-analog converter; the first control module is specifically configured to: when the sum of the second magnetic field driving signal and the signal value is greater than or equal to the measuring range of the second digital-to-analog converter, calculating the sum of the first magnetic field driving signal and the resolution of the first digital-to-analog converter to obtain an adjusted first magnetic field driving signal, and calculating the sum of the second magnetic field driving signal and a first adjusting value to obtain an adjusted second magnetic field driving signal, wherein the first adjusting value is the difference between the signal value and the measuring range of the second digital-to-analog converter.
According to one embodiment of the present invention, the first control module is specifically configured to, when controlling the magnetic field generator according to the first magnetic field driving signal and the second magnetic field driving signal: adding the first magnetic field driving signal and the second magnetic field driving signal to obtain a total driving signal; the magnetic field generator is controlled in dependence on the total drive signal.
According to one embodiment of the present invention, the PID control module is configured to calculate a second difference between a scan field termination value and the scan field start value, obtain n unit field stability periods according to the second difference, determine a first magnetic field strength target value of the x unit field stability period in the x unit field stability period, and obtain a second PID signal output value according to the magnetic field strength actual measurement value and the first magnetic field strength target value, where n is an integer greater than 1; and the sweeping DAC module is used for obtaining a third magnetic field driving signal according to the second PID signal output value in the x-th unit field stabilizing period, and controlling the magnetic field generator according to the first magnetic field driving signal, the second magnetic field driving signal and the third magnetic field driving signal, wherein x is more than or equal to 1 and less than or equal to n.
According to an embodiment of the present invention, when the PID control module obtains n unit steady-state periods according to the second difference value, the PID control module is specifically configured to: dividing the second difference into n parts; and obtaining a unit stable field period according to the second difference value, n and the target magnetic field intensity change rate.
According to one embodiment of the present invention, the PID control module is specifically configured to, when determining the first magnetic field strength target value of the x-th unit steady-field period: and determining a first magnetic field strength target value of an x-th unit stable field period according to the scanning initial value and the second difference value.
According to one embodiment of the present invention, the PID control module is specifically configured to, when obtaining the second PID signal output value according to the measured magnetic field strength value and the first magnetic field strength target value: and calculating a third difference value between the measured magnetic field intensity value and the target value of the first magnetic field intensity, and performing PID (proportion integration differentiation) adjustment on the third difference value to obtain a second PID signal output value.
According to one embodiment of the present invention, the scan DAC module includes: a range DAC, configured to obtain a first reference signal according to the second difference value; and the sweeping DAC is used for obtaining the third magnetic field driving signal according to the second PID signal output value and the first reference signal.
According to one embodiment of the invention, the first reference signal is obtained by:
kxi 1/i0= (T2-T1)/B, where k is a first coefficient, I1 is the first reference signal, I0 is a second reference signal for full-scale output of the range DAC, T1 is a scan start value, T2 is a scan end value, and B is a magnetic field strength calibration value when the range DAC and the scan DAC are both full-scale output.
According to one embodiment of the present invention, the scan DAC module further comprises: and the bias DAC is used for obtaining a bias signal according to the third magnetic field driving signal, the first reference signal, the second reference signal and the first coefficient, and obtaining an updated third magnetic field driving signal according to the third magnetic field driving signal and the bias signal.
According to one embodiment of the invention, the bias signal I3 is obtained by:
I3=I1×I2×wherein I2 is the third magnetic field driving signal.
According to one embodiment of the invention, 0.99.gtoreq.k.gtoreq.0.67.
According to one embodiment of the present invention, the PID control module is further configured to: when the third difference value is smaller than the first preset difference value, setting the upper limit of the output value of the second PID signal as a first upper limit value; when the third difference value is larger than or equal to the first preset difference value and smaller than or equal to the second preset difference value, setting the upper limit of the second PID signal output value as a second upper limit value, wherein the second upper limit value is larger than the first upper limit value; and when the third difference value is larger than a second preset difference value, setting the upper limit of the output value of the second PID signal as a third upper limit value, wherein the third upper limit value is larger than the second upper limit value.
According to one embodiment of the present invention, the PID control module is further configured to set, in n unit field stabilization periods, a maximum time taken by the scan DAC module to make the measured value of the magnetic field strength coincide with the first target value of the magnetic field strength to be a first preset time, and then t0> t1, where t0 is the unit field stabilization period, and t1 is the first preset time; the PID control module is also used for sending out test data acquisition instructions at a second preset time after the start of each unit steady-state period, wherein t0> t2> t1, and t2 is the second preset time.
According to one embodiment of the invention, the steady-field DAC module, the sweeping DAC and the bias DAC are bipolar outputs, wherein the output polarities of the steady-field DAC module and the sweeping DAC are the same, and the output polarities of the bias DAC and the sweeping DAC are opposite.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
FIG. 1 is a schematic diagram of a magnetic field strength control device according to an embodiment of the present invention;
FIG. 2 is a schematic view showing the structure of a magnetic field strength control device according to a first embodiment of the present invention;
fig. 3 is a schematic structural view of a magnetic field strength control device according to a second embodiment of the present invention.
Detailed Description
Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative and intended to explain the present invention and should not be construed as limiting the invention.
A magnetic field strength control device according to an embodiment of the present invention will be described below with reference to fig. 1 to 3.
Fig. 1 is a schematic view of a magnetic field strength control device according to an embodiment of the present invention. As shown in fig. 1, the magnetic field strength control device 100 includes: a magnetic field detection module 10, a PID control module 20 and a steady field DAC module 30.
The magnetic field detection module 10 is used for acquiring a magnetic field intensity actual measurement value of a magnetic field generated by the magnetic field generator; the PID control module 20 is configured to calculate a first difference between the measured magnetic field strength value and the start value of the sweeping field, and perform PID adjustment on the first difference to obtain a first PID signal output value; the steady-state DAC module 30 includes a first digital-to-analog conversion sub-module 31, a second digital-to-analog conversion sub-module 32, and a first control module 33, where the resolution of the first digital-to-analog conversion sub-module 31 is greater than the resolution of the second digital-to-analog conversion sub-module 32; wherein the first PID signal output value outputs a first magnetic field driving signal through the first digital-to-analog conversion sub-module 31, where s1= (S/M1) '×m1, S1 is the first magnetic field driving signal, S is the first PID signal output value, M1 is the resolution of the first digital-to-analog conversion sub-module 31, and (S/M1)' is the rounded value of S/M1; the first PID signal output value outputs a second magnetic field driving signal through the second digital-to-analog conversion sub-module 32, where s2= { (S-S1)/M2 } 'x M2, S2 is the second magnetic field driving signal, M2 is the resolution of the second digital-to-analog conversion sub-module 32, { (S-S1)/M2 }' is the rounded value of (S-S1)/M2, and the resolution of the first magnetic field driving signal is different from the resolution of the second magnetic field driving signal; the first control module 33 is configured to control the magnetic field generator according to the first magnetic field driving signal and the second magnetic field driving signal, so that the magnetic field strength of the magnetic field generated by the magnetic field generator is stabilized at a start value of the sweeping field.
Specifically, the magnetic field detection module 10 acquires the measured value T of the magnetic field intensity of the magnetic field generated by the magnetic field generator.
The PID control module 20 calculates a first difference between the measured magnetic field strength value T and the scan start value T1, i.e. Δ1= |t-T1|, and performs PID adjustment on the first difference Δ1 to obtain a first PID signal output value S. When the first difference Δ1 is smaller than the first preset value a1, the PID control module 20 sets the upper limit of the first PID signal output value S as a first threshold L1; when the first difference value delta 1 is larger than or equal to a first preset value a1 and smaller than or equal to a second preset value b1, setting the upper limit of the first PID signal output value S as a second threshold value K1, wherein the second threshold value K1 is larger than the first threshold value L1; when the first difference Δ1 is greater than the second preset value b1, the upper limit of the first PID signal output value S is set to a third threshold J1, where the third threshold J1 is greater than the second threshold K1. Therefore, through a three-section adjusting method, on one hand, the adjusting efficiency of the PID control module can be improved, and the magnetic field intensity is enabled to be fast close to a scanning initial value; on the other hand, the convergence efficiency of the PID control module can be improved, so that the magnetic field intensity is quickly stabilized near the initial value of the sweeping field. It should be noted that, the upper limit of the output value of the first PID signal may also be set by a multi-stage adjustment method.
For example: the first preset value a1 and the second preset value b1 are respectively 1Gs and 10Gs, and the first threshold L1, the second threshold K1 and the third threshold J1 are respectively 0.034Gs, 0.9Gs and 9Gs. When the first difference delta 1<1Gs, setting the upper limit of the first PID signal output value S to be 0.034Gs; when the Gs is less than or equal to 1Gs and less than or equal to 10Gs, setting the upper limit of the output value S of the first PID signal to be 0.9Gs; at the first difference Δ1>10Gs, the upper limit of the first PID signal output value S is set to 9Gs.
It should be noted that, assuming that the overall strength of the magnetic field is adjustable within the range of 0-9000Gs, the magnetic field strength can be precisely controlled to be 2 in theory -18 9000 Gs.apprxeq.0.034 Gs. Since the magnetization characteristic of the electromagnet determines that the magnitude of the magnetic field driving current is not linearly related to the magnetic field strength once, the magnetic field driving output increases by a current corresponding to 0.034Gs, and the measured magnetic field strength does not change by 0.034Gs, so that the magnetic field driving output needs to be regulated and controlled by the PID control module 20. The "first PID signal output value S" refers to magnetic field driving: the set current variation value, which approximately varies the magnetic field by the first PID signal output value S, can be adjusted each time.
Further, the first PID signal output value S outputs the first magnetic field driving signal through the first digital-to-analog conversion sub-module 31, where s1= (S/M1) '×m1, S1 is the first magnetic field driving signal, S is the first PID signal output value, M1 is the resolution of the first digital-to-analog conversion sub-module 31, and (S/M1)' is the rounded value of S/M1; the first PID signal output value S outputs a second magnetic field driving signal through the second digital-to-analog conversion sub-module 32, where s2= { (S-S1)/M2 } '×m2, S2 is the second magnetic field driving signal, M2 is the resolution of the second digital-to-analog conversion sub-module 32, { (S-S1)/M2 }' is the rounded value of (S-S1)/M2, and the resolution of the first magnetic field driving signal is different from the resolution of the second magnetic field driving signal. It should be noted that, in the embodiment of the present invention, the resolution is the precision. In addition, the resolution of the first digital-to-analog conversion sub-module 31 is equal to the range of the second digital-to-analog conversion sub-module 32. Therefore, the magnetic field driving signal generating module combined by the first digital-to-analog conversion sub-module and the second digital-to-analog conversion sub-module can realize the original range of the DAC on one hand and finer resolution on the other hand.
For example: first digital-to-analog converterResolution M1 of module 31 is 2 -9 X 11v, the resolution M of the second DAC sub-module 32 is 2 -18 X 11v, the first PID signal output value S is input to the first magnetic field driving signal S1 output by the first digital-to-analog conversion sub-module 31, where: s/(2) -9 X 11 v) and then multiplying by 2 -9 X 11v; the first PID signal output value S is input to the second magnetic field driving signal S2 output by the second digital-to-analog conversion sub-module 32 as follows: (S-S1)/(2) -18 X 11 v) (where rounding may be rounded or the remainder may be directly rounded) and multiplied by 2 -18 ×11v。
Further, the first control module 33 sums the first magnetic field driving signal S1 and the second magnetic field driving signal S2 to obtain a total driving signal; the magnetic field generator is controlled according to the total driving signal so that the magnetic field strength of the magnetic field generated by the magnetic field generator is stabilized at a scan start value T1.
As an example, referring to fig. 2, the first digital-to-analog conversion sub-module 31 may include a first digital-to-analog converter 311, and the second digital-to-analog conversion sub-module 32 may include a second digital-to-analog converter 321 and an attenuator 322 connected in sequence, the resolution of the second digital-to-analog converter 321 being the same as the resolution of the first digital-to-analog converter 311; wherein,,
the first PID signal output value outputs a first magnetic field driving signal through the first digital-to-analog converter 311, wherein s1= (S/M1) 1 )’×M1 1 ，M1 1 For the resolution of the first digital-to-analog converter 311, (S/M1) 1 ) ' S/M1 1 Is the rounding value of (2);
the first PID signal output value outputs a second magnetic field driving signal through a second digital-to-analog converter 321 and an attenuator 322 which are sequentially connected, wherein s2= { (S-S1) N/M1 1 }’×M2 1 N is the attenuation multiple of the attenuator 322, M2 1 Is the ratio of the resolution of the second DAC 321 to the attenuation multiple of the attenuator 322, { (S-S1) N/M1 1 The expression (S-S1) N/M1 1 The integer n=d/M1 of the attenuation factor of the attenuator 322 1 Where D is the range of the second digital to analog converter 321. It should be noted that, the range of the first dac 311 and the second dacThe range of the device 321 is the same. Therefore, the magnetic field driving signal generating module combined by the first digital-to-analog conversion sub-module and the second digital-to-analog conversion sub-module can realize the original range of the DAC on one hand and finer resolution on the other hand.
For example: the measuring range D of the first digital-to-analog converter 311 and the second digital-to-analog converter 321 is 11v, and the sampling code bit numbers of the first digital-to-analog converter 311 and the second digital-to-analog converter 321 are 9 (i.e. 2 9 A number of sample codes), the resolution of the first digital-to-analog converter 311 and the resolution M1 of the second digital-to-analog converter 321 1 Are all 2 -9 X 11v, the attenuation factor N of the attenuator 322 is 512, the resolution M2 of the second DAC sub-module 32 1 Is the ratio of the resolution of the second digital-to-analog converter 321 to the attenuation multiple N of the attenuator 322, i.e. 2 -18 X 11v. The first magnetic field driving signal S1 output from the first digital-to-analog converter 311 as the first PID signal output value S is: s/(2) -9 X 11 v) and then multiplying by 2 -9 X 11v, the sampling code of the first digital-to-analog converter 311 is S1/(2) -9 X 11 v); the first PID signal output value S inputs the second magnetic field driving signal S2 output by the second digital-to-analog converter 321 and the attenuator 322, which are sequentially connected, as follows: (S-S1) x 512/(2) -9 X 11 v) (where rounding may be rounded or the remainder may be directly rounded) and multiplied by 2 -18 X 11v, the sampling code of the second digital-to-analog converter 321 is S2×N/(2) -9 ×11v）。
It should be noted that, the first PID signal output value outputs a signal value through the second digital-to-analog converter 321; the first control module 33 is specifically configured to: when the sum of the second magnetic field driving signal and the signal value is greater than or equal to the measuring range of the second digital-to-analog converter 321, calculating the sum of the first magnetic field driving signal and the resolution of the first digital-to-analog converter 311 to obtain an adjusted first magnetic field driving signal, and calculating the sum of the second magnetic field driving signal and the first adjusting value to obtain an adjusted second magnetic field driving signal, wherein the first adjusting value is the difference between the signal value and the measuring range of the second digital-to-analog converter 321.
Specifically, the firstA PID signal output value outputs a signal value S0 through the second digital-to-analog converter 321. The first control module 33 calculates the resolution M1 of the first magnetic field driving signal S1 and the first digital-to-analog converter 311 when the sum of the second magnetic field driving signal S2 and the signal value S0 is greater than or equal to the measurement range D of the second digital-to-analog converter 321, that is, S2+S0 is greater than or equal to D 1 The sum of the two values to obtain an adjusted first magnetic field driving signal, namely S1' =S1+M1 1 And calculates the sum of the second magnetic field driving signal S2 and the first adjustment value I, to obtain an adjusted second magnetic field driving signal, where the first adjustment value I is the difference between the signal value S0 and the range D of the second digital-to-analog converter 321, i.e., i=s0-D, that is, the adjusted second magnetic field driving signal S2' =s2+s0-D. Therefore, the first control module updates the first magnetic field driving signal and the second magnetic field driving signal when the sum of the second magnetic field driving signal and the signal value is larger than or equal to the measuring range of the second digital-to-analog converter.
In summary, a first PID signal output value is obtained by PID adjustment of a first difference value between the measured magnetic field intensity value and the initial sweeping value; according to the PID signal output value, two magnetic field driving signals with different resolutions, namely a first magnetic field driving signal and a second magnetic field driving signal, are obtained, and then, the magnetic field generator is controlled according to the first magnetic field driving signal and the second magnetic field driving signal, so that the adjusting efficiency of the PID control module can be accelerated, the magnetic field intensity is enabled to be fast close to a scanning initial value, the convergence efficiency of the PID control module is accelerated, the magnetic field intensity is enabled to be fast stabilized near the scanning initial value, and the magnetic field intensity control precision and the field stabilizing efficiency are improved.
As an example, the PID control module 20 calculates a second difference between the scan field end value and the scan field start value, obtains n unit field stability periods according to the second difference, and determines a first magnetic field strength target value of the x unit field stability period in the x unit field stability period, and obtains a second PID signal output value according to the magnetic field strength actual measurement value and the first magnetic field strength target value, where n is an integer greater than 1.
Specifically, the PID control module 20 calculates a second difference Δ2 between the scan end value T2 and the scan start value T1, divides the second difference Δ2 into n (n may be set according to the test requirement), and obtains a unit field stabilization period, i.e., Δ2/(nv) according to the second difference, n, and the target magnetic field strength change rate v (i.e., the magnetic field strength change rate requirement of the scan). For example: when the scanning is performed in a 3000Gs-4000 Gs interval, 1000 data are required to be acquired in a group of scanning tests according to the requirement of test data acquisition precision, and the time of the whole scanning test is 100 seconds, then the change rate v of the target magnetic field strength is 1000Gs/100 seconds=10 Gs/second, and the unit field stabilizing period is 100 milliseconds.
In addition, the PID control module 20 calculates a third difference between the measured magnetic field strength T and the first magnetic field strength target B1, i.e., Δ3= |t-b1|, with t1+xΔ2/n as the first magnetic field strength target in the x-th unit field stabilization period. For example: when the scanning is performed in the 3000Gs-4000 Gs interval, 1000 data are required to be acquired in one group of scanning tests according to the requirement of test data acquisition precision, and the time of the whole scanning test is 100 seconds, then the change rate v of the target magnetic field intensity is 1000Gs/100 seconds=10 Gs/second, and the unit field stabilizing period is 100 milliseconds. In the first unit steady-state period (0-100 ms at the beginning of the experiment), the first magnetic field strength target value of PID becomes (3000+1) Gs, the magnetic field is increased from 3000Gs to 3001Gs, and in the tail section of 100 ms (60 th ms, 70 ms, 80 ms, 90 ms, 95 ms or 99 ms), the magnetic field strength is basically stabilized at 3001Gs, and test data are collected; in the x-th unit steady-state period (100 x-100 to 100x milliseconds at the beginning of the experiment), the first magnetic field strength target value of PID becomes (3000+x) Gs, the magnetic field is increased from 3000Gs to (3000+x) Gs, and in the tail section of the x-th unit steady-state period, the magnetic field strength is basically stabilized at (3000+x) Gs, and test data are collected.
It should be noted that, the PID control module 20 is further configured to set, in n unit field stabilization periods, a maximum time taken by the scan DAC module 40 to make the measured value of the magnetic field intensity coincide with the first target value of the magnetic field intensity to be a first preset time t1, and then the unit field stabilization period t0> t1; the PID control module 20 is further configured to issue a test data acquisition command at a second preset time t2 after the start of each unit field stabilization period, where t0> t2> t1.
Further, the PID control module 20 performs PID adjustment on the third difference Δ3 to obtain a second PID signal output value S'.
When the third difference Δ3 is smaller than the first preset difference a2, the PID control module 20 sets the upper limit of the second PID signal output value S' as the first upper limit L2; when the third difference delta 3 is greater than or equal to the first preset difference a2 and less than or equal to the second preset difference b2, setting the upper limit of the second PID signal output value S' as a second upper limit value K2, wherein the second upper limit value K2 is greater than the first upper limit value L2; when the third difference Δ3 is greater than the second preset difference b2, the upper limit of the second PID signal output value S' is set to a third upper limit value J2, where the third upper limit value J2 is greater than the second upper limit value K2. Therefore, through a three-section adjusting method, on one hand, the adjusting efficiency of the PID control module can be improved, and the magnetic field intensity is enabled to be close to the end value of the sweeping field rapidly; on the other hand, the convergence efficiency of the PID control module can be improved, so that the magnetic field intensity is quickly stabilized near the end value of the sweeping field. It should be noted that, the upper limit of the output value of the second PID signal may also be set by a multi-stage adjustment method. The first upper limit value L2 is smaller than the first threshold value L1, the second upper limit value K2 is smaller than the second threshold value K1, and the third upper limit value J2 is smaller than the third threshold value J1.
Further, the scan DAC module 40 is configured to obtain a third magnetic field driving signal according to the second PID signal output value in the x-th unit field stabilization period, and control the magnetic field generator according to the first magnetic field driving signal, the second magnetic field driving signal, and the third magnetic field driving signal, where x is greater than or equal to 1 and less than or equal to n.
Specifically, referring to fig. 3, the scan DAC module 40 may include: a range DAC41 for obtaining a first reference signal according to the second difference value; and the scan DAC42 is configured to obtain a third magnetic field driving signal according to the second PID signal output value and the first reference signal.
Specifically, the range DAC41 obtains a first reference signal I1 by the formula kxi 1/i0= (T2-T1)/B, where k is a first coefficient, I1 is a first reference signal, I0 is a second reference signal for full-scale output of the range DAC41, T1 is a scan start value, T2 is a scan end value, and B is a magnetic field strength calibration value when the range DAC41 and the scan DAC42 are both full-scale output, and k is 0.99+.gtoreq.0.67. The magnetic field intensity calibration value B when the range DAC41 and the scan DAC42 are output at full scale can be obtained by a calibration correspondence relationship between the magnetic field driving control signal and the measured magnetic field intensity value. For example: when the magnetic field intensity calibration value B is 9000Gs at the time of full-scale output of the range DAC41 and the full-scale output of the scan field DAC42 (namely, the maximum range of the device scan field), the second reference signal I0 at the full-scale output of the range DAC41 is 11v, the k takes a value of 0.7, the scan start value T1 is 3000Gs, the scan end value T2 is 4000Gs, and the reference signal output by the range DAC41 is 110/63v. The scan DAC42 obtains a third magnetic field driving signal according to the product of the second PID signal output value and the first reference signal.
Referring to fig. 3, the scan DAC module 40 may further include: and a bias DAC43 for obtaining a bias signal according to the third magnetic field driving signal, the first reference signal, the second reference signal, and the first coefficient, and controlling the magnetic field generator according to the bias signal and the third magnetic field driving signal.
Specifically, the bias DAC43 performs the operation of using the formula i3=i1×i2×And obtaining a bias signal I3, wherein I1 is a first reference signal, I2 is a third magnetic field driving signal, and I0 is a second reference signal. The bias DAC43 obtains an updated third magnetic field drive signal based on the difference between the third magnetic field drive signal and the bias signal.
It should be noted that, since the magnetization characteristic of the electromagnet determines that the correspondence between the magnetic field strength and the driving current strength of the electromagnet whose magnetic field strength is in variation is not determined, taking a change from 3000Gs to 4000Gs as an example, it is possible that the magnetic field driving current needs to be changed to a strength (calibration value) corresponding to 4040Gs, the measured magnetic field strength can reach 4000Gs, and when the magnetic field is changed from 4000Gs to 3000Gs again, the magnetic field driving current may need to be changed to a strength (calibration value) corresponding to 2980 Gs, the measured magnetic field strength can reach 3000 Gs; for this purpose, a bias DAC43 is provided so that the magnetic field drive current can output an intensity range corresponding to 2950Gs-4050 Gs.
Namely: when the required scan field interval is 3000Gs-4000 Gs, the scan field range is 1000Gs, and the scan field range output by the range DAC41 is 1100Gs, the scan field DAC42 can output the third magnetic field driving signal corresponding to 3000Gs-4100 Gs, the bias DAC43 outputs the bias signal to decrease the third magnetic field driving signal by a signal value corresponding to 50Gs, and thus the total driving signal can vary the magnetic field between 2950Gs-4050Gs at a calibrated value.
In addition, the steady-field DAC module 30, the scan DAC42 and the bias DAC43 are bipolar outputs, and the output polarities of the steady-field DAC module 30 and the scan DAC42 are the same, and the output polarities of the bias DAC43 and the scan DAC42 are opposite.
Further, referring to fig. 3, the scan DAC module 40 may further include a second control module 44, where the second control module 44 is specifically configured to, when controlling the magnetic field generator according to the first magnetic field driving signal, the second magnetic field driving signal, and the third magnetic field driving signal: and superposing the first magnetic field driving signal, the second magnetic field driving signal and the third magnetic field driving signal, and controlling the magnetic field generator according to the superposed driving signals. Thus, the magnetic field intensity can be controlled to be relatively uniform and continuously variable.
It should be noted that, the correspondence between the magnetic field intensity and the driving current intensity of the electromagnet whose magnetic field intensity is in variation is not determined, so the total driving signal yH output by the scan DAC module 40 for controlling the scan range needs to be greater than the calibration signal value H corresponding to the scan range, that is: in the calibration process, the output signal value of the scan DAC module 40 is only required to be H in the specified range, but in the scan experiment, the full-scale output signal value of the scan DAC42 is required to be yH, and y >1, and the output signal value (i.e., bias signal) of the bias DAC43 is required to be 0.5 (y-1) H.
In summary, a second difference value between the scan field termination value and the scan field start value is calculated, and n unit field stabilization periods are obtained according to the second difference value; in the x-th unit stable field period, a first magnetic field strength target value of the x-th unit stable field period is determined, a third difference value between the magnetic field strength actual measurement value and the first magnetic field strength target value is calculated, a third magnetic field driving signal is obtained according to the second difference value and the third difference value, and the magnetic field generator is controlled according to the first magnetic field driving signal, the second magnetic field driving signal and the third magnetic field driving signal, so that the magnetic field strength can be controlled to be relatively uniform and continuously changed in a sweeping manner.
It should be noted that the logic and/or steps represented in the flowcharts or otherwise described herein, for example, may be considered as a ordered listing of executable instructions for implementing logical functions, and may be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. For the purposes of this description, a "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of the computer-readable medium would include the following: an electrical connection (electronic device) having one or more wires, a portable computer diskette (magnetic device), a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disc read-only memory (CDROM). In addition, the computer readable medium may even be paper or other suitable medium on which the program is printed, as the program may be electronically captured, via, for instance, optical scanning of the paper or other medium, then compiled, interpreted or otherwise processed in a suitable manner, if necessary, and then stored in a computer memory.
It is to be understood that portions of the present invention may be implemented in hardware, software, firmware, or a combination thereof. In the above-described embodiments, the various steps or methods may be implemented in software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, may be implemented using any one or combination of the following techniques, as is well known in the art: discrete logic circuits having logic gates for implementing logic functions on data signals, application specific integrated circuits having suitable combinational logic gates, programmable Gate Arrays (PGAs), field Programmable Gate Arrays (FPGAs), and the like.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the device or element being referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the present invention.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present invention, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise.
In the present invention, unless explicitly specified and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; either directly or indirectly, through intermediaries, or both, may be in communication with each other or in interaction with each other, unless expressly defined otherwise. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
In the present invention, unless expressly stated or limited otherwise, a first feature "up" or "down" a second feature may be the first and second features in direct contact, or the first and second features in indirect contact via an intervening medium. Moreover, a first feature being "above," "over" and "on" a second feature may be a first feature being directly above or obliquely above the second feature, or simply indicating that the first feature is level higher than the second feature. The first feature being "under", "below" and "beneath" the second feature may be the first feature being directly under or obliquely below the second feature, or simply indicating that the first feature is less level than the second feature.
While embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the invention, and that variations, modifications, alternatives and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the invention.

Claims (10)

1. A magnetic field strength control device, the device comprising:
the magnetic field detection module is used for acquiring a magnetic field intensity actual measurement value of the magnetic field generated by the magnetic field generator;
the PID control module is used for calculating a first difference value between the magnetic field strength actual measurement value and the scanning initial value, and performing PID adjustment on the first difference value to obtain a first PID signal output value;
the stable-field DAC module comprises a first digital-to-analog conversion sub-module, a second digital-to-analog conversion sub-module and a first control module, wherein the resolution of the first digital-to-analog conversion sub-module is larger than that of the second digital-to-analog conversion sub-module; wherein,,
the first PID signal output value outputs a first magnetic field driving signal through the first digital-to-analog conversion sub-module, where s1= (S/M1) '×m1, S1 is the first magnetic field driving signal, S is the first PID signal output value, M1 is the resolution of the first digital-to-analog conversion sub-module, and (S/M1)' is the rounding value of S/M1;
the first PID signal output value outputs a second magnetic field driving signal through the second digital-to-analog conversion sub-module, where s2= { (S-S1)/M2 } 'x M2, S2 is the second magnetic field driving signal, M2 is the resolution of the second digital-to-analog conversion sub-module, { (S-S1)/M2 }' is the rounded value of (S-S1)/M2, and the resolution of the first magnetic field driving signal is different from the resolution of the second magnetic field driving signal;
the first control module is used for controlling the magnetic field generator according to the first magnetic field driving signal and the second magnetic field driving signal so as to enable the magnetic field intensity of the magnetic field generated by the magnetic field generator to be stabilized at a scanning start value.
2. The magnetic field strength control device of claim 1, wherein the PID control module is further configured to:
when the first difference value is smaller than a first preset value, setting the upper limit of the output value of the first PID signal as a first threshold value;
when the first difference value is larger than or equal to a first preset value and smaller than or equal to a second preset value, setting the upper limit of the output value of the first PID signal as a second threshold value, wherein the second threshold value is larger than the first threshold value;
and when the first difference value is larger than a second preset value, setting the upper limit of the output value of the first PID signal as a third threshold value, wherein the third threshold value is larger than the second threshold value.
3. The magnetic field strength control device of claim 1, wherein the first digital-to-analog conversion sub-module comprises a first digital-to-analog converter, and the second digital-to-analog conversion sub-module comprises a second digital-to-analog converter and an attenuator connected in sequence, and the resolution of the second digital-to-analog converter is the same as the resolution of the first digital-to-analog converter; wherein,,
the first PID signal output value outputs a first magnetic field driving signal through the first digital-to-analog converter, wherein S1= (S/M1) 1 )’×M1 1 ，M1 1 For the resolution of the first D/A converter, (S/M1) 1 ) ' S/M1 1 Is the rounding value of (2);
the first PID signal output value outputs a second magnetic field driving signal through a second digital-analog converter and an attenuator which are connected in sequence, wherein S2= { (S-S1) N/M1 1 }’×M2 1 N is the attenuation multiple of the attenuator, M2 1 For the ratio of the resolution of the second D/A converter to the attenuation factor of the attenuator, { (S-S1) N/M1 1 The expression (S-S1) N/M1 1 Is a rounded value of (c).
4. A magnetic field strength control device according to claim 3, wherein the attenuation factor n=d/M1 of the attenuator 1 Wherein D is the range of the second digital-to-analog converter.
5. The magnetic field strength control device of claim 4, wherein the first PID signal output value outputs a signal value through the second digital-to-analog converter; the first control module is specifically configured to: when the sum of the second magnetic field driving signal and the signal value is greater than or equal to the measuring range of the second digital-to-analog converter, calculating the sum of the first magnetic field driving signal and the resolution of the first digital-to-analog converter to obtain an adjusted first magnetic field driving signal, and calculating the sum of the second magnetic field driving signal and a first adjusting value to obtain an adjusted second magnetic field driving signal, wherein the first adjusting value is the difference between the signal value and the measuring range of the second digital-to-analog converter.
6. The magnetic field strength control device according to claim 1, wherein the first control module is configured to, when controlling the magnetic field generator according to the first magnetic field driving signal and the second magnetic field driving signal:
adding the first magnetic field driving signal and the second magnetic field driving signal to obtain a total driving signal;
the magnetic field generator is controlled in dependence on the total drive signal.
7. The magnetic field strength control device according to claim 1, wherein the PID control module is configured to calculate a second difference between a scan field end value and the scan field start value, obtain n unit steady-state periods according to the second difference, determine a first magnetic field strength target value of the x-th unit steady-state period in the x-th unit steady-state period, and obtain a second PID signal output value according to the magnetic field strength actual measurement value and the first magnetic field strength target value, where n is an integer greater than 1;
the device also comprises a field sweeping DAC module which is used for obtaining a third magnetic field driving signal according to the second PID signal output value in the x-th unit field stabilizing period, and controlling the magnetic field generator according to the first magnetic field driving signal, the second magnetic field driving signal and the third magnetic field driving signal, wherein x is more than or equal to 1 and less than or equal to n.
8. The magnetic field strength control device of claim 7, wherein the PID control module is specifically configured to:
dividing the second difference into n parts;
and obtaining a unit stable field period according to the second difference value, n and the target magnetic field intensity change rate.
9. The magnetic field strength control device of claim 7, wherein the PID control module is specifically configured to:
and determining a first magnetic field strength target value of an x-th unit stable field period according to the scanning initial value and the second difference value.
10. The magnetic field strength control device of claim 7, wherein the PID control module is specifically configured to:
and calculating a third difference value between the measured magnetic field intensity value and the target value of the first magnetic field intensity, and performing PID (proportion integration differentiation) adjustment on the third difference value to obtain a second PID signal output value.
CN202310856606.4A 2023-07-13 2023-07-13 Magnetic field intensity control device Active CN116578160B (en)

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