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CN113719541B - Axial position detection method, device, unit and storage medium for magnetic suspension bearing - Google Patents

Axial position detection method, device, unit and storage medium for magnetic suspension bearing Download PDF

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Publication number
CN113719541B
CN113719541B CN202111152604.4A CN202111152604A CN113719541B CN 113719541 B CN113719541 B CN 113719541B CN 202111152604 A CN202111152604 A CN 202111152604A CN 113719541 B CN113719541 B CN 113719541B
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axial
bearing
radial
current
rotating shaft
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CN113719541A (en
Inventor
赵科杰
贾坤
王凡
张伦生
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Gree Electric Appliances Inc of Zhuhai
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Gree Electric Appliances Inc of Zhuhai
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C32/00—Bearings not otherwise provided for
    • F16C32/04—Bearings not otherwise provided for using magnetic or electric supporting means
    • F16C32/0406—Magnetic bearings
    • F16C32/044—Active magnetic bearings
    • F16C32/0444—Details of devices to control the actuation of the electromagnets
    • F16C32/0446—Determination of the actual position of the moving member, e.g. details of sensors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C32/00—Bearings not otherwise provided for
    • F16C32/04—Bearings not otherwise provided for using magnetic or electric supporting means
    • F16C32/0406—Magnetic bearings
    • F16C32/044—Active magnetic bearings
    • F16C32/0444—Details of devices to control the actuation of the electromagnets
    • F16C32/0451—Details of controllers, i.e. the units determining the power to be supplied, e.g. comparing elements, feedback arrangements with P.I.D. control
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
    • G01B7/003—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring position, not involving coordinate determination
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C2231/00—Running-in; Initial operation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C2360/00—Engines or pumps
    • F16C2360/44—Centrifugal pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C2362/00—Apparatus for lighting or heating
    • F16C2362/52—Compressors of refrigerators, e.g. air-conditioners

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Mechanical Engineering (AREA)
  • General Physics & Mathematics (AREA)
  • Magnetic Bearings And Hydrostatic Bearings (AREA)

Abstract

The invention discloses a method and a device for detecting the axial position of a magnetic suspension bearing, a refrigerating unit and a storage medium, wherein the method comprises the following steps: under the condition of receiving a detection instruction of an axial reference position of the axial bearing, acquiring a radial position of a rotating shaft; according to the radial position of the rotating shaft, a current is introduced to the radial bearing coil to control the radial displacement of the rotating shaft to be 0; current is introduced into the axial bearing coil, and the rotating shaft is controlled to move back and forth to the maximum moving range in the axial direction, so that the axial variation range of the rotating shaft in the axial direction is obtained; and determining the central point of the axial variation range, and determining the central point of the axial variation range as the axial reference position of the axial bearing so as to realize the detection of the axial position of the magnetic suspension bearing. According to the scheme, when the axial reference position of the magnetic suspension bearing in the refrigerating unit is detected, the friction force of the axial movement of the rotating shaft is reduced, so that the rotating shaft is convenient to move.

Description

Axial position detection method, device, unit and storage medium for magnetic suspension bearing
Technical Field
The invention belongs to the technical field of magnetic suspension, and particularly relates to a method and a device for detecting the axial position of a magnetic suspension bearing, a refrigerating unit and a storage medium.
Background
The magnetic suspension device needs to set the expected position before stable suspension, the current in the bearing coil (i.e. the stator coil of the magnetic suspension bearing) gradually changes from small to large like a sine wave, so that the position of the rotating shaft deviates by one circle, and the central point of the moving range can be used as the expected position, which is called as a detection reference position.
The detection reference position is divided into two steps, namely a radial reference position detection step and an axial reference position detection step. When the radial reference position is detected, no current passes through the axial bearing coil, and similarly, no current passes through the radial bearing coil when the axial reference position is detected. When the axial reference position is detected, the friction force between the rotating shaft and the protective bearing needs to be overcome for moving, and for a magnetic suspension centrifugal unit with small cooling capacity, the rotating shaft is relatively small in design, light in weight and relatively easy to move. For a large-cooling-capacity unit, the rotating shaft is designed to be large, the mass of the rotating shaft is large, and therefore the rotating shaft cannot move due to the action of friction force when the axial reference position is detected, or the rotating shaft is difficult to move to cause shaft grinding.
The above is only for the purpose of assisting understanding of the technical aspects of the present invention, and does not represent an admission that the above is prior art.
Disclosure of Invention
The invention aims to provide a method and a device for detecting the axial position of a magnetic suspension bearing, a refrigerating unit and a storage medium, so as to solve the problem that a rotating shaft is difficult to move when the axial reference position of the magnetic suspension bearing in the refrigerating unit is detected, and achieve the effect of reducing the friction force of the axial movement of the rotating shaft when the axial reference position of the magnetic suspension bearing in the refrigerating unit is detected, so that the rotating shaft can be conveniently moved.
The invention provides a method for detecting the axial position of a magnetic suspension bearing, wherein the magnetic suspension bearing comprises the following steps: a rotating shaft, an axial bearing and a radial bearing; the bearing coil of the magnetic suspension bearing comprises: an axial bearing coil of the axial bearing, and a radial bearing coil of the radial bearing; the axial position detection method of the magnetic suspension bearing comprises the following steps: under the condition that a detection instruction of an axial reference position of the axial bearing is received, acquiring the radial position of the rotating shaft; according to the radial position of the rotating shaft, current is introduced to the radial bearing coil to control the radial displacement of the rotating shaft to be 0; current is led into the axial bearing coil, and the rotating shaft is controlled to move back and forth to the maximum moving range in the axial direction, so that the axial variation range of the rotating shaft in the axial direction is obtained; and determining the central point of the axial variation range, and determining the central point of the axial variation range as the axial reference position of the axial bearing so as to realize the detection of the axial position of the magnetic suspension bearing.
In some embodiments, according to the radial position of the rotating shaft, applying a current to the radial bearing coil controls the displacement of the rotating shaft in the radial direction to be 0, including: determining a radial current; and introducing the radial current to the radial bearing so as to enable the radial bearing coil to generate electromagnetic force, wherein the electromagnetic force can at least offset partial gravity of the rotating shaft.
In some embodiments, determining the radial current comprises:
calculating the radial current according to the following formula:
Figure BDA0003287629770000021
wherein, mu0The magnetic field is a vacuum magnetic conductivity, A is the magnetic pole area of the radial bearing, N is the number of winding turns, I is the current in the radial bearing coil, namely the radial current, x is the distance in the equivalent vertical direction, k is a calculation coefficient smaller than 1, m is the mass of the shaft, and g is the gravitational acceleration.
In some embodiments, passing the radial current to the radial bearing comprises: determining the charging time of the radial bearing coil according to the radial current; and determining an effective duty ratio according to the ratio of the charging time to a set PWM period, and outputting current to the radial bearing coil according to the effective duty ratio.
In some embodiments, passing a current through the axial bearing coil to control the shaft to move back and forth in the axial direction to a maximum movement range includes: and introducing current to the axial bearing coil according to a current change mode of changing from small to large and then changing from large to small so as to control the rotating shaft to move back and forth to the maximum movement range in the axial direction.
In some embodiments, passing a current to the axial bearing coil in a current variation manner from small to large and then from large to small comprises: and according to a mode similar to sinusoidal curve change, the current introduced into the axial bearing coil is changed from small to large and then from large to small.
In accordance with the above method, another aspect of the present invention provides an axial position detecting apparatus for a magnetic suspension bearing, the magnetic suspension bearing comprising: a rotating shaft, an axial bearing and a radial bearing; the bearing coil of the magnetic suspension bearing comprises: an axial bearing coil of the axial bearing, and a radial bearing coil of the radial bearing; the axial position detection device of the magnetic suspension bearing comprises: an acquisition unit configured to acquire a radial position of the rotating shaft upon receiving a detection instruction of an axial reference position of the axial bearing; the control unit is configured to supply current to the radial bearing coil according to the radial position of the rotating shaft so as to control the radial displacement of the rotating shaft to be 0; the control unit is further configured to supply current to the axial bearing coil, and control the rotating shaft to move back and forth to a maximum moving range in the axial direction, so that an axial variation range of the rotating shaft in the axial direction is obtained; the control unit is further configured to determine a center point of the axial variation range, and determine the center point of the axial variation range as an axial reference position of the axial bearing, so as to realize detection of the axial position of the magnetic suspension bearing.
In some embodiments, the control unit, which controls the radial displacement of the rotating shaft to be 0 by applying a current to the radial bearing coil according to the radial position of the rotating shaft, includes: determining a radial current; and introducing the radial current to the radial bearing so as to enable the radial bearing coil to generate electromagnetic force, wherein the electromagnetic force can at least offset partial gravity of the rotating shaft.
In some embodiments, the control unit, determining the radial current, comprises: calculating the radial current according to the following formula:
Figure BDA0003287629770000031
wherein, mu0The magnetic field is a vacuum magnetic conductivity, A is the magnetic pole area of the radial bearing, N is the number of winding turns, I is the current in the radial bearing coil, namely the radial current, x is the distance in the equivalent vertical direction, k is a calculation coefficient smaller than 1, m is the mass of the shaft, and g is the gravitational acceleration.
In some embodiments, the control unit, which passes the radial current to the radial bearing, includes: determining the charging time of the radial bearing coil according to the radial current; and determining an effective duty ratio according to the ratio of the charging time to a set PWM period, and outputting current to the radial bearing coil according to the effective duty ratio.
In some embodiments, the controlling unit, which applies a current to the axial bearing coil to control the rotating shaft to move back and forth in the axial direction to the maximum moving range, includes: and introducing current to the axial bearing coil according to a current change mode of changing from small to large and then changing from large to small so as to control the rotating shaft to move back and forth to the maximum movement range in the axial direction.
In some embodiments, the controlling unit, which applies a current to the axial bearing coil in a current variation manner from small to large and then from large to small, includes: and according to a mode similar to sinusoidal curve change, the current introduced into the axial bearing coil is changed from small to large and then from large to small.
In accordance with another aspect of the present invention, there is provided a refrigeration unit comprising: the axial position detection device of the magnetic suspension bearing is described above.
In accordance with the above method, a further aspect of the present invention provides a storage medium, which includes a stored program, wherein when the program is executed, a device on which the storage medium is located is controlled to execute the above axial position detection method for a magnetic bearing.
Therefore, according to the scheme of the invention, when the axial reference position of the magnetic suspension bearing in the refrigerating unit is detected, the current which changes from small to large is introduced to the axial bearing coil, and the predetermined fixed current is introduced to the radial bearing coil, so that the rotating shaft moves along the axial direction easily, and the voltage stress of the radial bearing coil is reduced; therefore, when the axial reference position of the magnetic suspension bearing in the refrigerating unit is detected, the friction force of the axial movement of the rotating shaft is reduced, so that the rotating shaft is convenient to move.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.
Drawings
FIG. 1 is a schematic flow chart of an embodiment of the axial position detection method of a magnetic suspension bearing of the present invention;
FIG. 2 is a schematic flow chart illustrating an embodiment of controlling the radial displacement of the rotating shaft to be 0 by applying a current to the radial bearing coil in the method of the present invention;
FIG. 3 is a schematic flow chart illustrating one embodiment of applying the radial current to the radial bearing in the method of the present invention;
FIG. 4 is a schematic structural diagram of an embodiment of an axial position detecting apparatus of a magnetic suspension bearing according to the present invention;
FIG. 5 is a simplified force analysis schematic of a magnetic bearing detecting an axial reference position;
fig. 6 is a schematic flow chart of an embodiment of a method for detecting an axial position of a magnetic bearing.
The reference numbers in the embodiments of the present invention are as follows, in combination with the accompanying drawings:
102-an obtaining unit; 104-control unit.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the specific embodiments of the present invention and the accompanying drawings. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Considering that the magnetic suspension bearing generally adopts closed-loop control, when the axial reference position is detected and the axial movement is difficult, the magnetic suspension bearing controller can increase the axial current output which can reach 2 to 3 times of that in normal operation, which is undoubtedly challenging for circuit design and circuit service life. In addition, grinding the shaft may cause the center of mass of the shaft to change, which may aggravate unbalanced torque during operation of the unit and make it difficult to control.
According to an embodiment of the present invention, a method for detecting an axial position of a magnetic bearing is provided, as shown in fig. 1, which is a schematic flow chart of an embodiment of the method of the present invention. The magnetic suspension bearing comprises: a rotating shaft, an axial bearing and a radial bearing. The bearing coil of the magnetic suspension bearing comprises: an axial bearing coil of the axial bearing, and a radial bearing coil of the radial bearing. The axial position detection method of the magnetic suspension bearing comprises the following steps: step S110 to step S140.
In step S110, in a case where a detection instruction of an axial reference position of the axial bearing is received, a radial position of the rotating shaft is acquired.
In step S120, according to the radial position of the rotating shaft, a current is applied to the radial bearing coil to control the radial displacement of the rotating shaft to be 0.
In some embodiments, in step S120, a specific process of applying a current to the radial bearing coil according to the radial position of the rotating shaft to control the radial displacement of the rotating shaft to be 0 is described in the following exemplary description.
Referring to a schematic flow chart of an embodiment of the method of the present invention shown in fig. 2, in which current is supplied to the radial bearing coil to control the radial displacement of the rotating shaft to be 0, further describing a specific process of supplying current to the radial bearing coil to control the radial displacement of the rotating shaft to be 0 in step S120, the method includes: step S210 and step S220.
Step S210, a radial current is determined. The radial current is used for leading to the radial bearing coil, so that the radial bearing coil generates electromagnetic force which can counteract at least partial gravity of the rotating shaft.
In some embodiments, determining the radial current in step S210 includes: calculating the radial current according to the following formula:
Figure BDA0003287629770000061
wherein, mu0For vacuum permeability, A is the magnetic pole area of the radial bearing, N is the number of winding turns, and I is the diameterThe current into the bearing coil is radial current, x is the distance in the equivalent vertical direction, k is a calculation coefficient less than 1, m is the mass of the shaft, and g is the gravitational acceleration.
Fig. 5 is a simplified force analysis diagram of the magnetic bearing when detecting the axial reference position. As shown in fig. 5, the front and rear bearing coils of the magnetic bearing generate electromagnetic attraction force to the axial attraction disc, so that the shaft (i.e., the rotating shaft) moves back and forth in the axial direction. A simple force analysis is made below for embodiments of the inventive arrangements.
In the scheme of the invention, the function of balancing a part of gravity by utilizing electromagnetic force is utilized, a coefficient k is introduced for convenient description, and a stress equation of radial electromagnetic force F provided by a radial bearing coil is listed:
F＝kG
Figure BDA0003287629770000062
in the formula (1), F is the radial electromagnetic force provided by the radial bearing coil, G is the gravity borne by the shaft, k is a coefficient, and the value range is more than or equal to 0.5 and less than 1. The value of k is less than 1, i.e. the radial electromagnetic force is less than gravity, in order to ensure that the shaft does not move in the radial direction when detecting the axial reference position. m is the mass of the shaft. g is the gravitational acceleration. Mu.s0Is a vacuum magnetic permeability. A is the magnetic pole area. And N is the number of winding turns. x is the distance in the equivalent vertical direction. I is the current in the radial bearing coil. The parameters except the current belong to inherent parameters of the unit, and the current I can be calculated through a formula (1).
Step S220, passing the radial current to the radial bearing to enable the radial bearing coil to generate an electromagnetic force, where the electromagnetic force can at least counteract a partial gravity of the rotating shaft.
The invention relates to a scheme, in particular to a method for detecting the axial position of a bearing of a large-cooling-capacity magnetic suspension centrifugal unit.
In some embodiments, a specific process of applying the radial current to the radial bearing in step S220 is further described with reference to a schematic flow chart of an embodiment of applying the radial current to the radial bearing in the method of the present invention shown in fig. 3, including: step S310 and step S320.
Step S310, determining the charging time of the radial bearing coil according to the radial current.
Step S320, determining an effective duty ratio according to the ratio of the charging time to a set PWM period, and outputting current to the radial bearing coil according to the effective duty ratio.
In an active half-bridge power amplifier, the inductance of a coil is L, the resistance is R, and when switching tubes of upper and lower bridge arms are simultaneously turned on, the inductance L is in a charging state, and the rest is in a follow current or discharging state. During charging, a charging circuit is analyzed, and a voltage equation is listed:
Figure BDA0003287629770000071
i is the instantaneous time current in the coil, UMOSIs the voltage drop of the switching tube and U is the bus voltage. When the boundary condition I is met, the charging is finished, the switching tube is turned off, the charging time is T, the PWM period is T, and the effective duty ratio is as follows:
Figure BDA0003287629770000072
this is called the effective duty cycle in order to distinguish it from the actual PWM wave duty cycle. The upper and lower tubes are simultaneously switched on in the period of effective duty ratio, and the coil inductor is in a charging state, namely the PWM waves of the upper and lower tubes are the part with high level.
At this moment, the initial parameters and the parking position of the rotating shaft are known, and the current can be calculated by reasonably selecting a coefficient k within the range that k is more than or equal to 0.5 and less than 1. The time required for reaching the balance current is calculated by a voltage equation, then an effective duty ratio is obtained, the main control outputs a PWM wave with a fixed duty ratio, the position of the rotating shaft in the vertical direction cannot be changed, the electromagnetic force offsets a part of gravity, the supporting force Fn provided by the bearing is reduced, and further the axial friction force f is reduced, and therefore the problems that the movement is difficult and the axial current is overlarge due to overlarge friction when the reference position is axially detected are solved.
In step S130, current is applied to the axial bearing coil, and the rotating shaft is controlled to move back and forth in the axial direction to the maximum moving range, so as to obtain the axial variation range of the rotating shaft in the axial direction.
In some embodiments, the step S130 of applying a current to the axial bearing coil to control the rotating shaft to move back and forth in the axial direction to the maximum moving range includes: and introducing current to the axial bearing coil according to a current change mode of changing from small to large and then changing from large to small so as to control the rotating shaft to move back and forth to the maximum movement range in the axial direction.
In the detection mode of the related scheme, the vertical direction is gravity and supporting force, the axial friction force of the shaft is large, and the axial movement requires that a coil flows a large current to generate electromagnetic attraction. According to the detection mode of the scheme of the invention, the radial bearing coil is electrified to generate electromagnetic force opposite to the gravity direction so as to weaken the influence of gravity and reduce the supporting force, so that the axial friction force is reduced, and the axial electromagnetic force required by relative movement is reduced.
In some embodiments, passing a current to the axial bearing coil in a current variation manner from small to large and then from large to small comprises: and according to a mode similar to or similar to a sine curve change, the current introduced into the axial bearing coil is changed from small to large and then from large to small.
Fig. 6 is a schematic flow chart of an embodiment of a method for detecting an axial position of a magnetic bearing. As shown in fig. 6, the method for detecting the axial position of a magnetic bearing includes:
step 1, a main control (such as a bearing controller of a magnetic suspension bearing) sends out an instruction for starting to detect a bearing reference position.
And 2, feeding back the specific position of the rotating shaft by the radial displacement sensor.
And 3, calculating by the main control according to known parameters including physical parameters of the shaft and the position of the shaft, sending PWM waves with fixed duty ratio to the power amplifier, and enabling the radial bearing coil to flow a certain amount of current without breaking the stress balance in the vertical direction, namely, without radial displacement. The specific calculation process refers to the force analysis in fig. 5.
And 4, the current of the axial bearing coil is changed from small to large and then from large to small, the current is changed like sine, the shaft moves back and forth along the axial direction to the maximum range, and the radial current returns to zero.
And 5, setting the central point of the axial variation range as an axial reference position, and finishing the detection of the axial reference position.
At step S140, a central point of the axial variation range is determined, and the central point of the axial variation range is determined as an axial reference position of the axial bearing, so as to achieve detection of the axial position of the magnetic suspension bearing.
The scheme of the invention provides an axial position detection method of a magnetic suspension bearing, when an axial reference position is detected, a fixed current passes through the axial direction, the current of an axial bearing coil changes from large to small, the radial displacement does not change, the friction force during axial movement can be reduced, a rotor is protected, and the current of the axial bearing coil is reduced.
In the scheme of the invention, when the axial reference position is detected, aiming at the large-cooling-capacity magnetic suspension centrifugal unit, the scheme of the invention adopts a mode of balancing gravity by using radial electromagnetic force, and a mode of outputting fixed duty ratio PWM (pulse width modulation), so that the radial electromagnetic force is kept constant while the position of a shaft in the radial direction is not changed, and thus, the friction force during axial movement can be reduced, the problems of axial bearing coil overcurrent and axial movement difficulty when the large-cooling-capacity magnetic suspension centrifugal unit detects the axial reference position are solved, a bearing rotor is protected, and the service life of an axial bearing coil is prolonged.
By adopting the technical scheme of the embodiment, when the axial reference position of the magnetic suspension bearing in the refrigerating unit is detected, the current which changes from small to large is introduced to the axial bearing coil, and the predetermined fixed current is introduced to the radial bearing coil, so that the rotating shaft moves along the axial direction easily, and the voltage stress of the radial bearing coil is reduced. Therefore, when the axial reference position of the magnetic suspension bearing in the refrigerating unit is detected, the friction force of the axial movement of the rotating shaft is reduced, so that the rotating shaft is convenient to move.
According to an embodiment of the present invention, there is also provided an axial position detecting apparatus of a magnetic bearing corresponding to the axial position detecting method of a magnetic bearing. Referring to fig. 4, a schematic diagram of an embodiment of the apparatus of the present invention is shown. The magnetic suspension bearing comprises: a rotating shaft, an axial bearing and a radial bearing. The bearing coil of the magnetic suspension bearing comprises: an axial bearing coil of the axial bearing, and a radial bearing coil of the radial bearing. The axial position detection device of the magnetic suspension bearing comprises: an acquisition unit 102 and a control unit 104.
Wherein the obtaining unit 102 is configured to obtain the radial position of the rotating shaft upon receiving a detection instruction of the axial reference position of the axial bearing. The specific functions and processes of the acquiring unit 102 are referred to in step S110.
And the control unit 104 is configured to supply current to the radial bearing coil to control the radial displacement of the rotating shaft to be 0 according to the radial position of the rotating shaft. The specific function and processing of the control unit 104 are referred to in step S120.
In some embodiments, the controlling unit 104, applying a current to the radial bearing coil to control the radial displacement of the rotating shaft to be 0 according to the radial position of the rotating shaft, includes:
the control unit 104 is in particular further configured to determine a radial current. The radial current is used for leading to the radial bearing coil, so that the radial bearing coil generates electromagnetic force which can counteract at least partial gravity of the rotating shaft. The specific functions and processes of the control unit 104 are also referred to in step S210.
In some embodiments, the control unit 104, determining the radial current, includes: the control unit 104, in particular, is further configured to calculate the radial current according to the following formula:
Figure BDA0003287629770000091
wherein, mu0The magnetic field is a vacuum magnetic conductivity, A is the magnetic pole area of the radial bearing, N is the number of winding turns, I is the current in the radial bearing coil, namely the radial current, x is the distance in the equivalent vertical direction, k is a calculation coefficient smaller than 1, m is the mass of the shaft, and g is the gravitational acceleration.
Fig. 5 is a simplified force analysis diagram of the magnetic bearing when detecting the axial reference position. As shown in fig. 5, the front and rear bearing coils of the magnetic bearing generate electromagnetic attraction force to the axial attraction disc, so that the shaft (i.e., the rotating shaft) moves back and forth in the axial direction. A simple force analysis is made below for embodiments of the inventive arrangements.
In the scheme of the invention, the function of balancing a part of gravity by utilizing electromagnetic force is utilized, a coefficient k is introduced for convenient description, and a stress equation of radial electromagnetic force F provided by a radial bearing coil is listed:
F＝kG
Figure BDA0003287629770000101
in the formula (1), F is the radial electromagnetic force provided by the radial bearing coil, G is the gravity borne by the shaft, k is a coefficient, and the value range is more than or equal to 0.5 and less than 1, and can be selected according to actual requirements. The value of k is less than 1, i.e. the radial electromagnetic force is less than gravity, in order to ensure that the shaft does not move in the radial direction when detecting the axial reference position. m is the mass of the shaft. g is the acceleration of gravity. Mu.s0Is a vacuum magnetic permeability. A is the magnetic pole area. And N is the number of winding turns. x is the distance in the equivalent vertical direction. I is the current in the radial bearing coil. The parameters except the current belong to inherent parameters of the unit, and the current I can be calculated through a formula (1).
The control unit 104 is specifically further configured to supply the radial current to the radial bearing, so that the radial bearing coil generates an electromagnetic force, and the electromagnetic force can at least counteract a partial gravity of the rotating shaft. The specific functions and processes of the control unit 104 are also referred to in step S220.
The invention relates to a scheme, in particular to a detection device for the axial position of a bearing of a large-cooling-capacity magnetic suspension centrifugal unit.
In some embodiments, the control unit 104, which passes the radial current to the radial bearing, includes:
the control unit 104 is in particular further configured to determine a charging time of the radial bearing coil depending on the radial current. The specific functions and processes of the control unit 104 are also referred to in step S310.
The control unit 104 is specifically further configured to determine an effective duty ratio according to a ratio of the charging time to a set PWM period, and output a current to the radial bearing coil according to the effective duty ratio. The specific functions and processes of the control unit 104 are also referred to in step S320.
In an active half-bridge power amplifier, the inductance of a coil is L, the resistance is R, and when switching tubes of upper and lower bridge arms are simultaneously turned on, the inductance L is in a charging state, and the rest is in a follow current or discharging state. During charging, a charging circuit is analyzed, and a voltage equation is listed:
Figure BDA0003287629770000111
when the boundary condition I is equal to I, the charging is finished, the switching tube is turned off, the charging time is T, the PWM period is T, and the effective duty ratio is：
Figure BDA0003287629770000112
The effective duty cycle is referred to as a distinction from the actual PWM wave duty cycle. The upper and lower tubes are simultaneously switched on in the period of effective duty ratio, and the coil inductor is in a charging state, namely the PWM waves of the upper and lower tubes are the part with high level.
At this moment, the initial parameters and the parking position of the rotating shaft are known, and the current can be calculated by reasonably selecting a coefficient k within the range that k is more than or equal to 0.5 and less than 1. The time required for reaching the balance current is calculated by a voltage equation, then an effective duty ratio is obtained, the main control outputs a PWM wave with a fixed duty ratio, the position of the rotating shaft in the vertical direction cannot be changed, the electromagnetic force offsets a part of gravity, the supporting force Fn provided by the bearing is reduced, and further the axial friction force f is reduced, and therefore the problems that the movement is difficult and the axial current is overlarge due to overlarge friction when the reference position is axially detected are solved.
The control unit 104 is further configured to apply a current to the axial bearing coil, and control the rotating shaft to move back and forth in the axial direction to a maximum moving range, so as to obtain an axial variation range of the rotating shaft in the axial direction. The specific function and processing of the control unit 104 are also referred to in step S130.
In some embodiments, the controlling unit 104, applying a current to the axial bearing coil to control the rotating shaft to move back and forth in the axial direction to the maximum moving range, includes: the control unit 104 is further configured to supply a current to the axial bearing coil in a current change manner from small to large and then from large to small, so as to control the rotating shaft to move back and forth in the axial direction to a maximum movement range.
In the detection mode of the related scheme, the vertical direction is gravity and supporting force, the axial friction force of the shaft is large, and the axial movement requires that a coil flows a large current to generate electromagnetic attraction. According to the detection mode of the scheme of the invention, the radial bearing coil is electrified to generate electromagnetic force opposite to the gravity direction so as to weaken the influence of gravity and reduce the supporting force, so that the axial friction force is reduced, and the axial electromagnetic force required by relative movement is reduced.
In some embodiments, the controlling unit 104, which applies a current to the axial bearing coil in a current variation manner from small to large and then from large to small, includes: the control unit 104 is further configured to change the current passing through the axial bearing coil from small to large and then from large to small in a manner similar to a sinusoidal change.
Fig. 6 is a schematic flow chart of an embodiment of an axial position detecting device of a magnetic bearing. As shown in fig. 6, the axial position detecting apparatus of a magnetic bearing includes:
step 1, a main control (such as a bearing controller of a magnetic suspension bearing) sends out an instruction for starting to detect a bearing reference position.
And 2, feeding back the specific position of the rotating shaft by the radial displacement sensor.
And 3, calculating by the main control according to known parameters including physical parameters of the shaft and the position of the shaft, sending PWM waves with fixed duty ratio to the power amplifier, and enabling the radial bearing coil to flow a certain amount of current without breaking the stress balance in the vertical direction, namely, without radial displacement. The specific calculation process refers to the force analysis in fig. 5.
And 4, the current of the axial bearing coil is changed from small to large and then from large to small, the current is changed like sine, the shaft moves back and forth along the axial direction to the maximum range, and the radial current returns to zero.
And 5, setting the central point of the axial variation range as an axial reference position, and finishing the detection of the axial reference position.
The control unit 104 is further configured to determine a center point of the axial variation range, and determine the center point of the axial variation range as an axial reference position of the axial bearing, so as to achieve detection of the axial position of the magnetic bearing. The specific function and processing of the control unit 104 are also referred to in step S140.
According to the scheme, when the axial reference position is detected, the fixed current passes through the axial bearing coil in the radial direction, the current of the axial bearing coil changes from large to small, the radial displacement is not changed, the friction force during axial movement can be reduced, the rotor is protected, and the current of the axial bearing coil is reduced.
In the scheme of the invention, when the axial reference position is detected, aiming at the large-cooling-capacity magnetic suspension centrifugal unit, the scheme of the invention adopts a mode of balancing gravity by using radial electromagnetic force, and a mode of outputting fixed duty ratio PWM (pulse width modulation), so that the radial electromagnetic force is kept constant while the position of a shaft in the radial direction is not changed, and thus, the friction force during axial movement can be reduced, the problems of axial bearing coil overcurrent and axial movement difficulty when the large-cooling-capacity magnetic suspension centrifugal unit detects the axial reference position are solved, a bearing rotor is protected, and the service life of an axial bearing coil is prolonged.
Since the processes and functions implemented by the apparatus of this embodiment substantially correspond to the embodiments, principles and examples of the method, reference may be made to the related descriptions in the embodiments without being detailed in the description of this embodiment, which is not described herein again.
By adopting the technical scheme of the invention, when the axial reference position of the magnetic suspension bearing in the refrigerating unit is detected, the current which is changed from small to large is introduced to the axial bearing coil, the predetermined fixed current is introduced to the radial bearing coil, so that the rotating shaft is easy to move along the axial direction, the voltage stress of the radial bearing coil is reduced, the problems of overcurrent of the axial bearing coil and difficulty in axial movement when the axial reference position is detected by the large-cooling-capacity unit can be solved, and the convenience in detecting the axial reference position is improved.
According to the embodiment of the invention, the refrigeration unit corresponding to the axial position detection device of the magnetic suspension bearing is also provided. The refrigeration unit may include: the axial position detection device of the magnetic suspension bearing is described above.
Since the processes and functions of the refrigeration unit of this embodiment are basically corresponding to the embodiments, principles and examples of the foregoing devices, reference may be made to the related descriptions in the foregoing embodiments without being detailed in the description of this embodiment.
By adopting the technical scheme of the invention, when the axial reference position of the magnetic suspension bearing in the refrigerating unit is detected, the current which is changed from small to large is introduced to the axial bearing coil, and the predetermined fixed current is introduced to the radial bearing coil, so that the rotating shaft is easy to move along the axial direction, the voltage stress of the radial bearing coil is reduced, the bearing rotor can be protected, and the service life of the axial bearing coil can be prolonged.
According to an embodiment of the present invention, there is also provided a storage medium corresponding to the axial position detection method of a magnetic bearing, the storage medium including a stored program, wherein the program is executed to control a device on which the storage medium is located to execute the axial position detection method of a magnetic bearing.
Since the processing and functions implemented by the storage medium of this embodiment substantially correspond to the embodiments, principles, and examples of the foregoing method, reference may be made to the related descriptions in the foregoing embodiments without being detailed in the description of this embodiment.
By adopting the technical scheme of the invention, when the axial reference position of the magnetic suspension bearing in the refrigerating unit is detected, the current which is changed from small to large is introduced to the axial bearing coil, the predetermined fixed current is introduced to the radial bearing coil, so that the rotating shaft is easy to move along the axial direction, the voltage stress of the radial bearing coil is reduced, the rotating shaft is easy to move along the axial direction, the rotor is protected, and the current of the axial bearing coil is reduced.
In summary, it is readily understood by those skilled in the art that the advantageous modes described above can be freely combined and superimposed without conflict.
The above description is only an example of the present invention, and is not intended to limit the present invention, and it is obvious to those skilled in the art that various modifications and variations can be made in the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.

Claims (14)

1. A method for detecting the axial position of a magnetic suspension bearing is characterized in that the magnetic suspension bearing comprises the following steps: a rotating shaft, an axial bearing and a radial bearing; the bearing coil of the magnetic suspension bearing comprises: an axial bearing coil of the axial bearing, and a radial bearing coil of the radial bearing; the axial position detection method of the magnetic suspension bearing comprises the following steps:
under the condition that a detection instruction of an axial reference position of the axial bearing is received, acquiring the radial position of the rotating shaft;
according to the radial position of the rotating shaft, current is introduced to the radial bearing coil to control the radial displacement of the rotating shaft to be 0;
current is introduced into the axial bearing coil, and the rotating shaft is controlled to move back and forth to the maximum moving range in the axial direction, so that the axial variation range of the rotating shaft in the axial direction is obtained;
and determining the central point of the axial variation range, and determining the central point of the axial variation range as the axial reference position of the axial bearing so as to realize the detection of the axial position of the magnetic suspension bearing.
2. The method for detecting the axial position of the magnetic suspension bearing according to claim 1, wherein the step of applying a current to the radial bearing coil to control the radial displacement of the rotating shaft to be 0 according to the radial position of the rotating shaft comprises the steps of:
determining a radial current;
and introducing the radial current to the radial bearing so as to enable the radial bearing coil to generate electromagnetic force, wherein the electromagnetic force can at least offset partial gravity of the rotating shaft.
3. The method for detecting the axial position of a magnetic bearing according to claim 2, wherein determining the radial current comprises:
calculating the radial current according to the following formula:
Figure FDA0003287629760000011
wherein, mu0The magnetic field is a vacuum magnetic conductivity, A is the magnetic pole area of the radial bearing, N is the number of winding turns, I is the current in the radial bearing coil, namely the radial current, x is the distance in the equivalent vertical direction, k is a calculation coefficient smaller than 1, m is the mass of the shaft, and g is the gravitational acceleration.
4. The method for detecting the axial position of a magnetic suspension bearing according to claim 2, wherein the step of passing the radial current to the radial bearing comprises:
determining the charging time of the radial bearing coil according to the radial current;
and determining an effective duty ratio according to the ratio of the charging time to a set PWM period, and outputting current to the radial bearing coil according to the effective duty ratio.
5. The method for detecting the axial position of the magnetic suspension bearing as claimed in any one of claims 1 to 4, wherein the step of passing a current through the axial bearing coil to control the rotating shaft to move back and forth in the axial direction to the maximum moving range comprises the following steps:
and introducing current to the axial bearing coil according to a current change mode of changing from small to large and then changing from large to small so as to control the rotating shaft to move back and forth to the maximum movement range in the axial direction.
6. The method for detecting the axial position of the magnetic suspension bearing according to claim 5, wherein the step of passing a current to the axial bearing coil in a current change mode of firstly changing from small to large and then changing from large to small comprises the following steps:
and according to a mode similar to sinusoidal curve change, the current introduced into the axial bearing coil is changed from small to large and then from large to small.
7. An axial position detecting device of a magnetic suspension bearing, characterized in that the magnetic suspension bearing comprises: a rotating shaft, an axial bearing and a radial bearing; the bearing coil of the magnetic suspension bearing comprises: an axial bearing coil of the axial bearing, and a radial bearing coil of the radial bearing; the axial position detection device of the magnetic suspension bearing comprises:
an acquisition unit configured to acquire a radial position of the rotating shaft upon receiving a detection instruction of an axial reference position of the axial bearing;
the control unit is configured to supply current to the radial bearing coil according to the radial position of the rotating shaft so as to control the radial displacement of the rotating shaft to be 0;
the control unit is further configured to supply current to the axial bearing coil, and control the rotating shaft to move back and forth to a maximum moving range in the axial direction, so that an axial variation range of the rotating shaft in the axial direction is obtained;
the control unit is further configured to determine a center point of the axial variation range, and determine the center point of the axial variation range as an axial reference position of the axial bearing, so as to realize detection of the axial position of the magnetic suspension bearing.
8. The axial position detecting device of a magnetic suspension bearing as claimed in claim 7, wherein the control unit, according to the radial position of the rotating shaft, applies a current to the radial bearing coil to control the radial displacement of the rotating shaft to 0, comprising:
determining a radial current;
and introducing the radial current to the radial bearing so as to enable the radial bearing coil to generate electromagnetic force, wherein the electromagnetic force can at least offset partial gravity of the rotating shaft.
9. The axial position sensing device of a magnetic bearing as claimed in claim 8, characterized in that the control unit, determining the radial current, comprises:
calculating the radial current according to the following formula:
Figure FDA0003287629760000031
wherein, mu0The magnetic field is a vacuum magnetic conductivity, A is the magnetic pole area of the radial bearing, N is the number of winding turns, I is the current in the radial bearing coil, namely the radial current, x is the distance in the equivalent vertical direction, k is a calculation coefficient smaller than 1, m is the mass of the shaft, and g is the gravitational acceleration.
10. The axial position detecting device of a magnetic suspension bearing as claimed in claim 8, wherein the control unit, which supplies the radial current to the radial bearing, comprises:
determining the charging time of the radial bearing coil according to the radial current;
and determining an effective duty ratio according to the ratio of the charging time to a set PWM period, and outputting current to the radial bearing coil according to the effective duty ratio.
11. The device for detecting the axial position of a magnetic suspension bearing according to any one of claims 7 to 10, wherein the control unit, which applies a current to the axial bearing coil to control the rotating shaft to move back and forth in the axial direction to the maximum moving range, comprises:
and introducing current to the axial bearing coil according to a current change mode of changing from small to large and then changing from large to small so as to control the rotating shaft to move back and forth to the maximum movement range in the axial direction.
12. The device for detecting the axial position of a magnetic suspension bearing as claimed in claim 11, wherein the control unit passes the current to the axial bearing coil in a current variation mode of first changing from small to large and then changing from large to small, comprising:
and according to a mode similar to sinusoidal curve change, the current introduced into the axial bearing coil is changed from small to large and then from large to small.
13. A refrigeration unit, comprising: axial position detection apparatus for a magnetic bearing as claimed in any of claims 7 to 12.
14. A storage medium, characterized in that the storage medium comprises a stored program, wherein the program, when executed, controls an apparatus in which the storage medium is located to perform the method for detecting an axial position of a magnetic bearing as claimed in any one of claims 1 to 6.
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