CN111857231B - Device and method for controlling rotating magnetic field by using capacitor charging and discharging time sequence - Google Patents
Device and method for controlling rotating magnetic field by using capacitor charging and discharging time sequence Download PDFInfo
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Abstract
The invention relates to a device and a method for controlling a rotating magnetic field by utilizing a capacitor charging and discharging time sequence, wherein the device comprises: the system comprises a plurality of groups of coils, a plurality of high-voltage direct-current power supplies, a plurality of high-voltage capacitors, a plurality of groups of switch switching circuits and a microcontroller; each group of coils is connected with a controllable high-voltage direct-current power supply and two high-voltage capacitors, and the high-voltage direct-current power supply connected with each group of coils is used for charging the two high-voltage capacitors; the microcontroller realizes the charging of a plurality of groups of middle and high voltage capacitors and the discharging time sequence of the high voltage capacitors to the coils by controlling the switch switching circuit, thereby controlling the rotating magnetic field generated in the plurality of groups of coils; the two high-voltage capacitors discharge each group of coils in turn, namely when one capacitor discharges, the other capacitor charges and is switched circularly, and the process is executed by a plurality of groups of coil circuits in turn.
Description
Technical Field
The invention relates to a rotating magnetic field generating device, in particular to a device and a method for controlling a rotating magnetic field by using a capacitor charging and discharging time sequence in a biological experiment and driving a magnetic micro-robot.
Background
With the development of society, rotating magnetic fields are applied more and more, and the application of various rotating magnetic fields in biomedicine has important value. At present, the realization of a rotating magnetic field has a plurality of methods, and is realized by using a rotating permanent magnet with a mechanical structure, three pairs of coils which are vertical to each other are used, a sinusoidal signal output by a signal source is driven by a power amplifier, and the device is more complex in structure. In addition, the existing rotating magnetic field scheme is difficult to realize high magnetic field amplitude in a large space and simultaneously realizes the quick switching of the rotating axial direction.
Disclosure of Invention
The invention aims to solve the problems that the existing rotating magnetic field generating system is complex in structure and is difficult to realize rapid adjustment of the orientation of a rotating shaft and the amplitude value of a high field, and provides a device and a method for controlling a rotating magnetic field by using a capacitor charging and discharging time sequence. The invention can realize the generation of the rotating magnetic field, and the microcontroller is adopted to control the amplitude, the frequency and the axial direction of the rotating magnetic field so as to realize the rotating magnetic field in any axial direction.
The invention adopts the technical scheme that a device for controlling a rotating magnetic field by utilizing a capacitor charging and discharging time sequence comprises: the system comprises a plurality of groups of coils, a plurality of high-voltage direct-current power supplies, a plurality of high-voltage capacitors, a plurality of groups of switch switching circuits and a microcontroller;
the high-voltage direct-current power supply is provided with a voltage control port or a serial communication interface, and the output voltage of the high-voltage direct-current power supply is controlled by the microprocessor through the voltage control port or the serial communication interface;
the coils are two, three or more groups, and each group of coils is correspondingly provided with a group of switch switching circuits;
each group of coils is connected with a high-voltage direct-current power supply and two high-voltage capacitors, and the high-voltage direct-current power supply connected with each group of coils is used for charging the two high-voltage capacitors; the microcontroller realizes the charging of high-voltage capacitors in the multiple groups of coil circuits and the discharging time sequence of the high-voltage capacitors to the coils by controlling the switch switching circuit, thereby controlling the time sequence of current generated in the multiple groups of coils and generating a rotating magnetic field; and the two high-voltage capacitors discharge each group of coils in turn, namely when one capacitor is discharged, the other capacitor is charged and is switched circularly.
Further, the method comprises the following steps: the voltage values of the high-voltage power supply and the high-voltage capacitor are 3-20kV, the voltage of the high-voltage power supply is controllable, the high-voltage capacitor discharges to the coil, the discharge loop works in a critical damping or underdamping state, and the oscillation frequencies of the discharge loops are the same during discharging.
Further, the method comprises the following steps: when the number of the coils is three, the three groups of coils are three pairs of Helmholtz coils which are perpendicular to each other pairwise, the three pairs of Helmholtz coils are sequentially increased in size and are nested and installed from small size to large size, the axial directions of the three pairs of Helmholtz coils respectively correspond to X, Y and Z axes of the magnetic field generating device, the axial centers of the three pairs of Helmholtz coils are intersected with a coordinate origin O, and the OXYZ forms a Cartesian coordinate system; three pairs of Helmholtz coils are electrified with positive current to generate magnetic fields along the positive direction of the coordinate axis; each pair of Helmholtz coils is connected with one direct-current high-voltage current source and two high-voltage capacitors, and the charging and discharging of the high-voltage direct-current power source and the two high-voltage capacitors between the Helmholtz coils are correspondingly controlled by a group of switch switching circuits; under the action of the microcontroller, the charging of the high-voltage direct-current power supply to the high-voltage capacitor is realized, and the trigger circuit triggers the silicon controlled rectifier to control the time sequence that the high-voltage capacitor starts to discharge to the three coils.
Further, the circuit specifically includes:
the positive pole of the high-voltage direct current power supply U1 is connected to one pole of a high-voltage capacitor C2, namely a node b, through a switch S1 and then connected to a node d through a switch S4, and the other pole of C2 is connected to the negative pole of the high-voltage direct current power supply U1, wherein the negative pole is a node f; the positive pole of the high-voltage direct current power supply U1 is connected to one pole of a high-voltage capacitor C1, namely a node C, through a switch S2 and then connected to a node d through a switch S3, and the other pole of C1 is connected to the negative pole of a high-voltage direct current power supply U1, namely a node f; the negative electrode of the high-voltage direct-current power supply U1 is connected with a node f; the rear ends of the bleeder resistor R1 connected in series with the switch S5 are respectively connected with nodes d and f; the anode of the thyristor Q1 and the cathode of the diode D1 are connected to a node D, the cathode of the thyristor Q1 and the anode of the diode D1 are connected to a node e, two ends of the X-axis coil L1 are respectively connected to a node e and a node f, and the node f is connected to GND; the connection between the Y-axis coil L2 and the Z-axis coil L3 is the same as that of the X-axis coil L1.
According to another aspect of the present invention, a method for controlling a rotating magnetic field by using a capacitor charging and discharging sequence is provided, which is used for the above device, and comprises the following steps:
the quantity of coil is two sets of, and the output of the high voltage power supply that two sets of coils correspond, the charging voltage of the electric capacity that also is connected of two sets of coils is: vx＝B0/kx，Vy＝B0/kyWhen the circuit frequency is ω, the time when the two capacitors start to discharge is: t is t1＝kT，t2K is kT + pi/2, k is a natural number, and T is a sine wave period; b is0To achieve the amplitude, k, of the rotating magnetic fieldx,kyVoltage values V of discharge capacitors in the two groups of coils respectivelyx，VyAnd the maximum value B of the magnetic field generated in the two coilsxmax,BymaxOf proportionality coefficient, i.e. Bxmax＝Vxkx,Bymax＝Vyky(ii) a If the direction is rotated in the opposite direction, only two paths of capacitors need to be exchanged at the moment of discharging; when the rotation frequency needs to be changed, the value of the capacitor or the inductance value connected into the circuit is changed simultaneously, so that the oscillation frequency of the two discharge circuits is equal to the set valueA fixed frequency.
According to another aspect of the present invention, a method for controlling a rotating magnetic field by using a capacitor charging/discharging sequence is provided, which is applied to the aforementioned apparatus, and specifically includes the following steps:
the number of the coils is three, when the rotating shaft of the rotating magnetic field is in any direction in a three-dimensional space, three groups of mutually orthogonal parallel coil pairs are made, the central axes of the three groups of mutually orthogonal parallel coil pairs are OX, OY and OZ, and the three groups of mutually orthogonal parallel coil pairs are orthogonal to an origin O; let the azimuth angle of the magnetic field rotation axis direction n be
Wherein theta is an included angle between the direction of the magnetic field rotating shaft and the positive direction of the OZ shaft,
the included angle between the projection of the rotating shaft direction of the magnetic field on the XOY plane and the positive direction of OX is obtained, and the amplitude is B0Three components [ B ] of rotating magnetic field with rotation frequency of omega in rectangular coordinate systemx By Bz]Expressed as:
where η ═ ω t, t is time;
the output of the high-voltage power supply corresponding to the three coils, that is, the charging voltage of the capacitor connected with the three coils is:
B0to achieve the amplitude, k, of the rotating magnetic fieldx,ky,kzThe voltage value of the discharge capacitor in the three-way coil and the proportionality coefficient of the maximum value of the magnetic field generated in the three-way coil, namely Bxmax＝Vxkx,Bymax＝Vyky,Bzmax＝Vzkz(ii) a When the circuit angular frequency is omega, the moment when the three high-voltage capacitors start to discharge is as follows:
wherein T is the period of the rotating magnetic field, i.e. T is 2 pi/omega, k is a natural number, theta is the included angle between the direction of the rotating shaft of the magnetic field and the positive direction of the OZ shaft,
is an included angle between the projection of the rotating shaft direction of the magnetic field on an XOY plane and the positive direction of OX;
the following equation was used:
furthermore, when the direction of the rotating magnetic field needs to be changed, the azimuth angle of the rotating shaft direction of the magnetic field is correspondingly changed
The discharge time of the high-voltage capacitor of the three-way coil is changed, and the rotating magnetic field can be rapidly changed;
when the magnetic field intensity needs to be changed, the output voltage of the three high-voltage power supplies is changed, namely the charging voltage of a high-voltage capacitor connected with the three coils is changed;
when the rotation frequency needs to be changed, the value of the capacitor or the inductance value connected into the circuit is changed at the same time, so that the oscillation frequency of the three discharge loops is equal to the set frequency.
Further, the method comprises the following steps:
when the magnetic field rotation axis is represented by direction cosine (cos α, cos β, cos γ), the output of the high-voltage power supply corresponding to the three coils, that is, the charging voltage of the capacitor connected to the three coils, is:
B0in order to realize the amplitude of the rotating magnetic field, alpha, beta and gamma are direction angles of the rotating shaft of the rotating magnetic field, and kx,ky,kzThe voltage value of the discharge capacitor in the three-way coil and the proportionality coefficient of the maximum value of the magnetic field generated in the three-way coil, namely Bxmax＝Vxkx,Bymax＝Vyky,Bzmax＝Vzkz(ii) a When the circuit angular frequency is omega, the time for the three high-voltage capacitors to start discharging is as follows:
wherein T is the period of the rotating magnetic field, namely T is 2 pi/omega, and k is a natural number. Wherein
Can be obtained from the following equation,
according to another aspect of the present invention, a method for controlling a rotating magnetic field by using a capacitor charging and discharging sequence is provided, which is used for the above device, and comprises the following steps:
when the magnetic field rotation axis is represented by direction cosine (cos α, cos β, cos γ), the output of the high-voltage power supply corresponding to the three coils, that is, the charging voltage of the capacitor connected to the three coils, is:
B0in order to realize the amplitude of the rotating magnetic field, alpha, beta and gamma are direction angles of the rotating shaft of the rotating magnetic field, and kx,ky,kzThe voltage value of the discharge capacitor in the three-way coil and the proportionality coefficient of the maximum value of the magnetic field generated in the three-way coil, namely Bxmax＝Vxkx,Bymax＝Vyky,Bzmax＝Vzkz(ii) a When the circuit angular frequency is omega, the time for the three high-voltage capacitors to start discharging is as follows:
wherein T is the period of the rotating magnetic field, namely T is 2 pi/omega, k is a natural number; wherein
It can be obtained from the following equation,
furthermore, when the direction of the rotating magnetic field needs to be changed, the direction angles alpha, beta and gamma of the rotating shaft of the magnetic field are correspondingly changed, and the discharge time of the high-voltage capacitors of the three coils is changed;
when the magnetic field intensity needs to be changed, the output voltage of the three high-voltage power supplies is changed, namely the charging voltage of a high-voltage capacitor connected with the three coils is changed;
when the rotation frequency needs to be changed, the value of the capacitor or the inductance value connected into the circuit is changed at the same time, so that the oscillation frequency of the three discharge loops is equal to the set frequency.
According to another aspect of the present invention, there is also provided a method of controlling a rotating magnetic field by the aforementioned apparatus, wherein the process of generating the sine wave in the coil L1 includes the steps of:
in the initial state, the circuits from S1 to S5 are all open; s1 is closed under the action of the microcontroller, U1 charges C2 to a given voltage Vx, S1 is opened, S4 is closed, and at a given moment
The microcontroller triggers the thyristor Q1 to be conducted through the trigger circuit, the C2 and the L1 form an oscillation circuit to complete a positive half wave, and when the circuit current is zero, namely the circuit current is zero
At the moment, the controlled silicon Q1 is automatically switched off, and the voltage on the C2 is negative; then C2, L1 completes the negative half wave through D1; thereby forming a sine wave of period T in L1; at the same time, at the moment of time
The microcontroller controls S2 to close to charge C1 until a given voltage Vx is reached, and opens S2;
at the moment of time
The switch-off S4 and the switch-on S3 are realized, the microcontroller triggers the conduction of the controllable silicon Q1 through the trigger circuit, the C1 and the L1 form an oscillation loop to complete a positive half-wave, and when the circuit current is zero, namely the circuit current is zero
At the moment, the controlled silicon Q1 is automatically switched off, and the voltage on the C1 is negative; then C1, L1 completes the negative half wave through D1; thus, another sine wave of period T is formed in L1; also at a given moment
The microcontroller controls S1 to close to charge C2 until a given voltage Vx is reached, and opens S1;
and then is on
Time off S3 on S4; in this cycle, U1 alternately charges C1 and C2, and C2 and C1 alternately discharges L1, thereby forming a sine wave magnetic field in L1;
and controlling other two-way switch switching circuits according to the control time sequence to respectively carry out charging and discharging processes on the L2 and the L3.
Has the advantages that:
the invention utilizes the time sequence matching of the high-voltage capacitor and the switch switching circuit to discharge and switch the coil, thereby realizing the improvement of the amplitude of the rotating magnetic field of the coil and the quick switching of the direction of the rotating shaft. The microcontroller realizes the charging of the high-voltage capacitor and the discharging time sequence of the high-voltage capacitor to the coils by controlling the switch switching circuit, thereby controlling the current generated in the multiple groups of coils and generating a rotating magnetic field. The technical scheme of the invention is easy to realize the precise control of the amplitude, the frequency and the axial direction of the rotating magnetic field, and provides a convenient way for the driving and the guiding of the magnetic micro-robot in the biological experiment and the body.
Drawings
FIG. 1 is a schematic view of a rotating magnetic field apparatus;
FIG. 2 is a circuit diagram of a rotating magnetic field;
FIG. 3 is a circuit control timing diagram.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments, and all other embodiments obtained by a person skilled in the art based on the embodiments of the present invention belong to the protection scope of the present invention without creative efforts.
The magnetic field generating device mainly comprises a plurality of groups of coils, a plurality of high-voltage direct-current power supplies, a plurality of high-voltage capacitors, a plurality of groups of switch switching circuits and a microcontroller. For simplicity of presentation, the microcontroller is not shown.
The high-voltage direct-current power supply part comprises 3 paths of controllable high-voltage direct-current power supplies, the 3 paths of controllable high-voltage direct-current power supplies are provided with voltage control ports or serial communication interfaces, and the output voltage of the high-voltage direct-current power supplies can be controlled by the microprocessor through the 3 paths of voltage control ports or the serial communication interfaces. The voltage values of the high-voltage power supply and the high-voltage capacitor can be 3-20 kV;
the coils in the invention can be two groups, three groups or more groups, each group of coils is correspondingly provided with a group of switching circuits, for example, when the coils are two groups, two groups of switch switching circuits are correspondingly arranged; when the coils are in three groups, three groups of switching circuits are correspondingly arranged; and so on.
Preferably, when the number of the coils is three, the three pairs of coils are three pairs of helmholtz coils perpendicular to each other in pairs, and are nested and installed from small size to large size, the axial directions of the three pairs of helmholtz coils correspond to the X, Y and Z axes of the magnetic field generating device, the axial centers of the three pairs of helmholtz coils intersect at the coordinate origin O, and the xyz forms a cartesian coordinate system. The magnetic field generated by the positive current introduced into the three pairs of coils is along the positive direction of the coordinate axis. Each pair of coils is connected with one path of controllable direct-current high-voltage current source and two high-voltage capacitors, and the high-voltage direct-current power source, the high-voltage capacitors and the pair of coils are correspondingly controlled through a group of switch switching circuits. Under the action of the microcontroller, the charging of the high-voltage direct-current power supply to the high-voltage capacitor can be realized, the thyristor can be triggered by the trigger circuit to control the time sequence of the high-voltage capacitor to discharge the three coils, and the specific circuit connection is shown in fig. 2.
Fig. 2 is a schematic diagram showing the circuit connection of the rotating magnetic field generating system according to the present invention, and the connection manner of the circuit is illustrated by taking the X-axis coil L1 as an example. The connection mode of the connection circuit of the Y-axis coil and the Z-axis coil is the same as that of the X-axis coil. The positive pole of the high-voltage direct current power supply U1 is connected to one pole of a high-voltage capacitor C2, namely a node b, through a switch S1 and then connected to a node d through a switch S4, and the other pole of C2 is connected to the negative pole of the high-voltage direct current power supply U1, wherein the negative pole is a node f; the positive pole of the high-voltage direct current power supply U1 is connected to one pole of a high-voltage capacitor C1, namely a node C, through a switch S2 and then connected to a node d through a switch S3, and the other pole of C1 is connected to the negative pole of a high-voltage direct current power supply U1, namely a node f; the negative electrode of the high-voltage direct-current power supply U1 is connected with a node f; the rear ends of the bleeder resistor R1 connected in series with the switch S5 are respectively connected with nodes d and f; the anode of thyristor Q1 and the cathode of diode D1 are connected to node D, the cathode of thyristor Q1 and the anode of diode D1 are connected to node e, the two ends of X-axis coil L1 are connected to node e and node f, and node f is connected to GND.
The process of using the microcontroller to control the charging and discharging and switching of the high voltage capacitor to generate a one-cycle sinusoidal waveform in the X-axis coil L1 is described as follows: as shown in figure 3 of the drawings,
in the initial state, the circuits from S1 to S5 are all open; s1 is closed under the action of the microcontroller, U1 charges C2 to a given voltage Vx, S1 is opened, S4 is closed, and at a given moment
The microcontroller triggers the controlled silicon Q1 to be conducted through the trigger circuit, the C2 and the L1 form an oscillation loop to complete a positive half-wave, and when the circuit current is zero, namely the circuit current is zero
At the moment, the controlled silicon Q1 is automatically switched off, and the voltage on the C2 is negative; then C2, L1 completes the negative half wave through D1; thereby forming a sine wave of period T in L1; at the same time, at the moment
The microcontroller controls S2 to close to charge C1 until a given voltage Vx is reached, and opens S2;
at the moment of time
The switch-off S4 and the switch-on S3 are realized, the microcontroller triggers the conduction of the controllable silicon Q1 through the trigger circuit, the C1 and the L1 form an oscillation loop to complete a positive half-wave, and when the circuit current is zero, namely the circuit current is zero
At the moment, the controlled silicon Q1 is automatically switched off, and the voltage on the C1 is negative; then C1, L1 through D1Forming a negative half wave; thus, another sine wave of period T is formed in L1; also at a given moment
The microcontroller controls S1 to close to charge C2 until a given voltage Vx is reached, and opens S1;
and then is on
Time off S3 on S4; in this cycle, U1 alternately charges C1 and C2, and C2 and C1 alternately discharges L1, thereby forming a sine wave magnetic field in L1;
and controlling other two-way switch switching circuits according to the control time sequence to respectively carry out charging and discharging processes on the L2 and the L3. The other two switch switching circuits have the same structure as the first switch circuit.
The two capacitors C1 and C2 are used for alternately charging and discharging, so that on one hand, the defect that the waveform of the current L1 is discontinuous due to the fact that continuous discharging cannot be realized by a single capacitor can be overcome, and the continuous discharging of the capacitor to the coil L1 is realized; on the other hand, when one capacitor is charged, the other capacitor is discharged, so that the charging time is saved, and the frequency of the rotating magnetic field can be improved.
The precise time required for the invention to control the rotating magnetic field is calculated and explained further below.
Suppose that a high-voltage DC power supply charges a high-voltage capacitor C to a voltage uC(0)Then, the coil L is discharged, and when the discharge loop works in a critical damping or under-damping state, the attenuation constant a and the natural oscillation frequency omega are0Frequency of oscillation omegad：
The current in the loop is:
wherein
R is the resistance in the loop and t is time. The maximum value of the current is:
it can be seen that when the circuit is determined, the maximum value of the current in the discharge circuit is proportional to the initial voltage of the high voltage capacitor, i.e. the maximum value of the magnetic field in the coil is proportional to the initial voltage of the capacitor. The high voltage capacitor discharge form can generate a magnetic field with higher amplitude. After the first capacitor discharges an oscillation period, the invention switches to the second capacitor whose voltage in the coil has been charged to a given value, and then completes an oscillation period. When the first capacitor is discharged, the second capacitor is charged to a given voltage; the first capacitor will be charged to a given voltage while the second capacitor is discharged. And then according to the basic principle of generating the space rotating magnetic field, the implementation method of the rotating magnetic field can be obtained.
When the axis of the rotating magnetic field is fixed, the rotating magnetic field may be composed of two mutually perpendicular coils or coil pairs. The initial values of the capacitances to which the two pairs of coils are connected are set so that the maximum value of the magnetic field generated in the two coils is equal to the given magnitude of the magnetic field. The difference of discharge time T/4, namely the phase difference of two sine waves is pi/2, namely the rotating magnetic field on the plane can be realized. When the rotating shaft needs to be reversed, the discharging time of the two coils only needs to be changed.
When the axis of rotation of the rotating magnetic field is in any direction in three dimensions, three sets of mutually orthogonal parallel coil pairs, typically Helmholtz coil pairs, with their central axes OX, OY, OZ, are made orthogonal to the origin O. As known from the space resolution geometry, the vector in space can be represented by azimuth. Let the azimuth angle of the magnetic field rotation axis direction n be
Wherein θ is a magnetic fieldThe included angle between the direction of the rotating shaft and the positive direction of the OZ shaft,
the included angle between the projection of the rotating shaft direction of the magnetic field on the XOY plane and the positive direction of OX is obtained, and the amplitude is B0Three components [ B ] of rotating magnetic field with rotation frequency of omega in rectangular coordinate systemx By Bz]Can be expressed as:
where η ═ ω t, t is time.
Let kx,ky,kzThe voltage value of the discharge capacitor in the three-way coil and the proportionality coefficient of the maximum value of the magnetic field generated in the three-way coil, namely Bxmax＝Vxkx,Bymax＝Vyky,Bzmax＝Vzkz. The reason is that:
wherein
Wherein
That is, the magnetic fields in the three groups of coils are the same-frequency sine waves with a certain phase difference, and the magnetic fields in the three coils have the phase
In practical application, the output of the high-voltage power supply corresponding to the three coilsThat is, the charging voltage of the capacitor connected with the three coils is:
the moment when the three high-voltage capacitors are switched on and the coil starts to discharge is as follows:
t is the oscillation period of the circuit, T is 2 pi/omega, and k is a natural number. A rotating magnetic field can be obtained.
When the rotating axis of the magnetic field is represented by direction cosine (cos α, cos β, cos γ), α, β, γ are included angles between the rotating axis direction and the coordinate axes OX, OY, OZ, the magnetic fields generated in the three sets of coils required for generating the rotating magnetic field are:
wherein
Can be obtained from the following equation,
the output of the high-voltage power supply corresponding to the three coils, namely the charging voltage value of the capacitor connected with the three coils is
The moment when the high-voltage capacitor switch-on circuit in the three-way circuit starts to discharge is as follows:
t is the oscillation period of the circuit, T is 2 pi/omega, and k is a natural number.
The implementation process of the rotating magnetic field is as follows:
setting the magnetic field intensity B generated by three pairs of Helmholtz coils in the X, Y and Z axial directionsx,By,BzInitial voltage V of high-voltage capacitor connected with three pairs of coilsx,Vy,VzCoefficient of proportionality kx,ky,kzI.e. Bxmax＝Vxkx，Bymax＝Vyky，Bzmax＝Vzkz. When it is desired to produce an azimuth angle of the axis of rotation of
Amplitude of B0When the rotating magnetic field has a rotating frequency ω, assuming that the magnetic field rotation angle is η, η ═ ω t, and t is time, the magnetic fields generated in the three pairs of helmholtz coils are:
and due to
Wherein
Wherein
The output of the high-voltage power supply corresponding to the three coils, that is, the charging voltage of the capacitor connected with the three coils is:
the moment when the three high-voltage capacitors are switched on and the coil starts to discharge is as follows:
t is the oscillation period of the circuit, T is 2 pi/omega, and k is a natural number.
The microcontroller sets the output of the high voltage power supply connected to the three pairs of Helmholtz coil coils according to equation (10) so that the corresponding high voltage capacitor is charged to Vx,Vy,VzAnd then triggering three thyristors according to the corresponding time of the formula (11) to obtain the required rotating magnetic field.
When the magnetic field amplitude needs to be changed, the amplitude B in the formula (10) is changed0Then the method is finished; when the direction of the rotating shaft of the magnetic field needs to be changed, the corresponding azimuth angle in the formula (10) is changed
And (4) finishing. Thus, the rotating magnetic field in any axial direction can be realized. When the rotation frequency needs to be changed, the value or inductance of the capacitor obtained in the connection circuit is changed at the same time, so that the oscillation frequency of the three discharge circuits is equal to the set frequency.
Although illustrative embodiments of the present invention have been described above to facilitate the understanding of the present invention by those skilled in the art, it should be understood that the present invention is not limited to the scope of the embodiments, but various changes may be apparent to those skilled in the art, and it is intended that all inventive concepts utilizing the inventive concepts set forth herein be protected without departing from the spirit and scope of the present invention as defined and limited by the appended claims.
Claims (7)
1. A method of controlling a rotating magnetic field using a capacitor charging and discharging sequence, for use in an apparatus for controlling a rotating magnetic field using a capacitor charging and discharging sequence, the apparatus comprising: the device comprises a plurality of groups of coils, a plurality of high-voltage direct-current power supplies, a plurality of high-voltage capacitors, a plurality of groups of switch switching circuits and a microcontroller;
the high-voltage direct-current power supply is provided with a voltage control port or a serial communication interface, and the output voltage of the high-voltage direct-current power supply is controlled by the microprocessor through the voltage control port or the serial communication interface;
the coils are two, three or more groups, and each group of coils is correspondingly provided with a group of switch switching circuits;
each group of coils is connected with a high-voltage direct-current power supply and two high-voltage capacitors, and the high-voltage direct-current power supply connected with each group of coils is used for charging the two high-voltage capacitors; the microcontroller realizes the charging of high-voltage capacitors in the multiple groups of coil circuits and the discharging time sequence of the high-voltage capacitors to the coils by controlling the switch switching circuit, thereby controlling the time sequence of current generated in the multiple groups of coils and generating a rotating magnetic field; the two high-voltage capacitors sequentially discharge each group of coils in turn, namely when one capacitor is discharged, the other capacitor is charged and circularly switched, and the method is characterized by comprising the following steps:
the number of the coils is three, when the rotating shaft of the rotating magnetic field is in any direction in a three-dimensional space, three groups of mutually orthogonal parallel coil pairs are made, the central axes of the three groups of mutually orthogonal parallel coil pairs are OX, OY and OZ, and the three groups of mutually orthogonal parallel coil pairs are orthogonal to an origin O; let the azimuth angle of the magnetic field rotation axis direction n be
Wherein theta is an included angle between the direction of the magnetic field rotating shaft and the positive direction of the OZ shaft,
for rotating the axis of the magnetic fieldThe projection of the direction on the XOY plane forms an included angle with the positive direction of OX, and the amplitude is B0Three components [ B ] of rotating magnetic field with rotation frequency of omega in rectangular coordinate systemx By Bz]Expressed as:
where η ═ ω t, t is time;
the output of the high-voltage power supply corresponding to the three coils, that is, the charging voltage of the capacitor connected with the three coils is:
B0to achieve the amplitude, k, of the rotating magnetic fieldx,ky,kzThe voltage value of the discharge capacitor in the three-way coil and the proportionality coefficient of the maximum value of the magnetic field generated in the three-way coil, namely Bxmax＝Vxkx,Bymax＝Vyky,Bzmax＝Vzkz(ii) a When the circuit angular frequency is omega, the moment when the three high-voltage capacitors start to discharge is as follows:
wherein T is the period of the rotating magnetic field, i.e. T is 2 pi/omega, k is a natural number, theta is the included angle between the direction of the rotating shaft of the magnetic field and the positive direction of the OZ shaft,
is an included angle between the projection of the rotating shaft direction of the magnetic field on an XOY plane and the positive direction of OX;
the following equation was used:
2. the method according to claim 1, wherein the rotating magnetic field is controlled by a capacitor charging and discharging sequence, and the method comprises the following steps:
when the direction of the rotating magnetic field needs to be changed, the azimuth angle of the rotating shaft direction of the magnetic field is correspondingly changed
The discharge time of the high-voltage capacitor of the three-way coil is changed, and the rotating magnetic field can be rapidly changed;
when the magnetic field intensity needs to be changed, the output voltage of the three high-voltage power supplies is changed, namely the charging voltage of a high-voltage capacitor connected with the three coils is changed;
when the rotation frequency needs to be changed, the value of the capacitor connected into the circuit or the inductance value is changed at the same time, so that the oscillation frequency of the three discharge loops is equal to the set frequency.
3. A method of controlling a rotating magnetic field using a capacitor charging and discharging sequence, for use in an apparatus for controlling a rotating magnetic field using a capacitor charging and discharging sequence, the apparatus comprising: the system comprises a plurality of groups of coils, a plurality of high-voltage direct-current power supplies, a plurality of high-voltage capacitors, a plurality of groups of switch switching circuits and a microcontroller;
the high-voltage direct-current power supply is provided with a voltage control port or a serial communication interface, and the output voltage of the high-voltage direct-current power supply is controlled by the microprocessor through the voltage control port or the serial communication interface;
the coils are two, three or more groups, and each group of coils is correspondingly provided with a group of switch switching circuits;
each group of coils is connected with a high-voltage direct-current power supply and two high-voltage capacitors, and the high-voltage direct-current power supply connected with each group of coils is used for charging the two high-voltage capacitors; the microcontroller realizes the charging of high-voltage capacitors in the multiple groups of coil circuits and the discharging time sequence of the high-voltage capacitors to the coils by controlling the switch switching circuit, thereby controlling the time sequence of current generated in the multiple groups of coils and generating a rotating magnetic field; the method is characterized in that when a magnetic field rotating shaft is expressed by direction cosine as (cos alpha, cos beta, cos gamma), the output of the high-voltage power supply corresponding to the three-way coil, namely the charging voltage of the capacitor connected with the three-way coil is as follows:
B0in order to realize the amplitude of the rotating magnetic field, alpha, beta and gamma are direction angles of the rotating shaft of the rotating magnetic field, and kx,ky,kzThe voltage value of the discharge capacitor in the three-way coil and the proportionality coefficient of the maximum value of the magnetic field generated in the three-way coil, namely Bxmax＝Vxkx,Bymax＝Vyky,Bzmax＝Vzkz(ii) a When the circuit angular frequency is omega, the time for the three high-voltage capacitors to start discharging is as follows:
wherein T is the period of the rotating magnetic field, namely T is 2 pi/omega, k is a natural number; wherein
Can be obtained from the following equation,
4. the method according to claim 3, wherein the rotating magnetic field is controlled by a capacitor charging and discharging sequence, and the method comprises the following steps:
when the direction of the rotating magnetic field needs to be changed, the direction angles alpha, beta and gamma of the rotating shaft of the magnetic field are correspondingly changed, and the discharge time of the high-voltage capacitors of the three paths of coils is changed;
when the magnetic field intensity needs to be changed, the output voltage of the three high-voltage power supplies is changed, namely the charging voltage of a high-voltage capacitor connected with the three coils is changed;
when the rotation frequency needs to be changed, the value of the capacitor connected into the circuit or the inductance value is changed at the same time, so that the oscillation frequency of the three discharge loops is equal to the set frequency.
5. A method according to claim 1 or 3, characterized in that:
the voltage values of the high-voltage direct-current power supply and the high-voltage capacitor are 3-20kV, the voltage of the high-voltage power supply is controllable, the high-voltage capacitor discharges to the coil, the discharge loop works in a critical damping or under-damping state, and the oscillation frequencies of the discharge loops are the same during discharging.
6. A method according to claim 1 or 3, comprising:
when the number of the coils is three, the three groups of coils are three pairs of Helmholtz coils which are perpendicular to each other pairwise, the three pairs of Helmholtz coils are sequentially increased in size and are nested and installed from small size to large size, the axial directions of the three pairs of Helmholtz coils respectively correspond to X, Y and Z axes of the magnetic field generating device, the axial centers of the three pairs of Helmholtz coils are intersected with a coordinate origin O, and the OXYZ forms a Cartesian coordinate system; three pairs of Helmholtz coils are electrified with positive current to generate magnetic fields along the positive direction of the coordinate axis; each pair of Helmholtz coils is connected with one direct-current high-voltage current source and two high-voltage capacitors, and the charging and discharging of the direct-current high-voltage current source and the two high-voltage capacitors between the Helmholtz coils are correspondingly controlled by a group of switch switching circuits; under the action of the microcontroller, the charging of the high-voltage direct-current power supply to the high-voltage capacitor is realized, and the trigger circuit triggers the silicon controlled rectifier to control the time sequence that the high-voltage capacitor starts to discharge to the three coils.
7. The method according to claim 1 or 3, characterized in that the device comprises in particular:
the positive pole of the high-voltage direct current power supply U1 is connected to one pole of a high-voltage capacitor C2, namely a node b, through a switch S1 and then connected to a node d through a switch S4, and the other pole of C2 is connected to the negative pole of the high-voltage direct current power supply U1, wherein the negative pole is a node f; the positive pole of the high-voltage direct current power supply U1 is connected to one pole of a high-voltage capacitor C1, namely a node C, through a switch S2 and then connected to a node d through a switch S3, and the other pole of the C1 is connected to the negative pole of a high-voltage direct current power supply U1, namely a node f; the negative electrode of the high-voltage direct-current power supply U1 is connected with a node f; the rear ends of the bleeder resistor R1 connected in series with the switch S5 are respectively connected with nodes d and f; the anode of the thyristor Q1 and the cathode of the diode D1 are connected to a node D, the cathode of the thyristor Q1 and the anode of the diode D1 are connected to a node e, two ends of the X-axis coil L1 are respectively connected to a node e and a node f, and the node f is connected to GND; the Y-axis coil L2 and the Z-axis coil L3 are connected to the X-axis coil L1.
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