CN111554162A - Eddy current braking law measuring device and method based on radial magnetic field - Google Patents

Eddy current braking law measuring device and method based on radial magnetic field Download PDF

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CN111554162A
CN111554162A CN202010547822.7A CN202010547822A CN111554162A CN 111554162 A CN111554162 A CN 111554162A CN 202010547822 A CN202010547822 A CN 202010547822A CN 111554162 A CN111554162 A CN 111554162A
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gyroscope
magnetic field
electromagnet
gyro
eddy current
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CN111554162B (en
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段彬
翟猛
崔笑仙
陈少康
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Jilin University
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    • G09B23/187—Models for scientific, medical, or mathematical purposes, e.g. full-sized devices for demonstration purposes for physics for electricity or magnetism for measuring instruments
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    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/34—Testing dynamo-electric machines
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/12—Measuring magnetic properties of articles or specimens of solids or fluids
    • G01R33/1253—Measuring galvano-magnetic properties
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
    • H02K7/10—Structural association with clutches, brakes, gears, pulleys or mechanical starters
    • H02K7/104—Structural association with clutches, brakes, gears, pulleys or mechanical starters with eddy-current brakes
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
    • H02K7/10—Structural association with clutches, brakes, gears, pulleys or mechanical starters
    • H02K7/116—Structural association with clutches, brakes, gears, pulleys or mechanical starters with gears
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
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Abstract

The invention relates to a device and a method for measuring an eddy current braking law based on a radial magnetic field, and aims to solve the problem that a device capable of visually measuring the eddy current braking law based on the radial magnetic field is lacked at present. The measuring device comprises a base, a first bearing, a clutch, a first gear, a gyroscope, a motor, a second gear, a micrometric screw, an electromagnet and a control system, wherein the measuring method comprises the steps of reading out the current magnetic field intensity by setting a preset rotating speed, measuring the static time of the gyroscope, drawing a graph by taking the rotating speed as an abscissa and the static time of the gyroscope as an ordinate, drawing n-t graphs under different magnetic field intensities in the same coordinate system, and comparing the n-t graphs with a theoretical curve. The measuring device provided by the invention utilizes the eddy current braking effect to carry out experiments, and can accurately predict the deceleration movement rule of the gyroscope under the influence of the eddy current braking effect of the radial magnetic field by combining the measuring method provided by the invention, so that comprehensive experiments are carried out, and the experimental and teaching effects are better.

Description

Eddy current braking law measuring device and method based on radial magnetic field
Technical Field
The invention relates to an eddy current braking law measuring device, in particular to an eddy current braking law measuring device and method based on a radial magnetic field.
Background
Along with the continuous development of scientific technology, various magnetic field intensity measuring instruments emerge on the market, wherein a teslameter represented by a Hall element is the most outstanding, the Hall effect measuring instrument adopts a Hall effect measuring principle, and has the advantages of simple structure, convenience in measurement and higher precision, but the device has higher cost and insufficient measurement intuition, and is not beneficial to enabling an experimenter to clearly identify the experimental principle; the magnetic field intensity measuring instrument manufactured by the current balance method applies the principle that an electrified lead is stressed in a magnetic field, measures the magnetic induction intensity according to the moment balance condition, but the instrument manufactured by the measuring method has a complex structure, is generally only used for qualitative experiments that students know the electromagnetic induction principle, and has relatively low measuring precision in certain measuring intervals due to the limitation of the design principle. Eddy current braking is widely applied in actual production and life, but at present, a device capable of visually measuring the eddy current braking law, particularly a device for measuring the eddy current braking law based on a radial magnetic field, is lacked, so that a device and a method which have visual and vivid phenomena, are convenient for teaching practice and student operation practice and can accurately measure the eddy current braking law are expected to be designed.
Disclosure of Invention
In order to solve the technical problems, the invention provides an eddy current braking law determination device based on a radial magnetic field, which comprises a base, a first bearing, a clutch, a first gear, a gyroscope, a motor, a second gear, a micrometer screw, an electromagnet and a control system, wherein the base is provided with a first bearing support, a gyroscope support and a micrometer screw support; the outer ring of the first bearing is fixed on the first bearing support, and the inner ring of the first bearing is provided with a sleeve; the clutch comprises a driving wheel, a driving shaft and a driven wheel, the driving wheel is connected with the driving shaft, and the driven wheel is connected with a shaft lever at one side of the gyroscope; a gear shaft of the first gear penetrates through the sleeve to be connected with a driving shaft of the clutch, and a shifting device is sleeved on the driving shaft of the clutch; the gyroscope is erected on the gyroscope support through shaft levers on two sides, and the shaft levers are connected with the gyroscope support through bearings; the motor is arranged at the lower part of the first bearing bracket, an output shaft of the motor is connected with a second gear, and the second gear is meshed with the first gear; the micrometer screw rod is horizontally fixed on the micrometer screw rod bracket, the front end of the micrometer screw rod is connected with the electromagnet, and the axis of the electromagnet is opposite to the radial direction of the gyroscope; the control system is arranged on the base and is connected with the motor, the power supply and the electromagnet through wires.
The photoelectric speed measuring sensor is arranged on the gyro bracket, is connected with the control system through a wire, measures the revolution number of the gyro and transmits the revolution number to the control system.
The shifting device comprises an upper fastening ring, a lower fastening ring, a second bearing, a shifting fork and a shifting lever, wherein the upper fastening ring and the lower fastening ring are fastened and fixed on the outer ring of the second bearing; the shifting fork is connected with the upper fastening ring and the lower fastening ring, and the shifting lever is connected with the shifting fork; the deflector rod is provided with a rotating shaft which is inserted into a shaft hole on the base, and the rotating shaft enables the deflector rod to form lever action; a return spring is arranged between the deflector rod and the base.
The control system comprises a processor, a motor driver, a display screen and keys, wherein the motor driver, the display screen and the keys are respectively connected with the processor, and the motor driver is also connected with the motor.
The display screen respectively displays the magnetic induction intensity and time of the electromagnet, a preset gyro rotating speed and a current gyro rotating speed; the keys comprise an increase key and a decrease key of the magnetic induction intensity of the electromagnet, an increase key and a decrease key of the preset gyro rotation speed, an operation key and a clear key of a timer, an on-off key of a motor and a power key of an instrument; the magnetic induction intensity of the electromagnet is adjusted through the increase key and the decrease key of the magnetic induction intensity, the magnetic induction intensity is displayed on the display screen, the rotating speed of the motor is controlled through the increase key and the decrease key of the rotating speed of the gyroscope, the rotating speed of the gyroscope is adjusted, and the revolution is measured through the photoelectric speed measuring sensor and displayed on the display screen.
The base is provided with a shell, the shell covers the first gear and the clutch, and a shifting rod of the shifting device extends out of an opening at the side edge of the shell.
The upper end of the top support is provided with a bearing cover, and the bearing cover is connected with the top support through a screw to fix a bearing on the top shaft lever.
The working principle of the device of the invention is as follows:
the first gear and the clutch are connected into a whole, and a gear shaft of the first gear can radially displace in a sleeve of the first bearing; when the shifting lever is shifted, the shifting lever drives the upper fastening ring and the lower fastening ring to move reversely through the shifting fork under the action of the rotating shaft, and pushes the driving wheel of the clutch to move towards the driven wheel until the driving wheel is contacted and combined with the driven wheel, so that the gyroscope rotates through the second gear, the first gear and the clutch to the torque of the gyroscope transmission motor; when the shifting lever is released, the shifting lever is reset under the action of the return spring, and the driving wheel and the driven wheel of the clutch are driven to be separated.
The invention provides a measuring method of an eddy current braking law measuring device based on a radial magnetic field, which comprises the following steps: the method comprises the following steps:
(1) selecting a gyroscope, and fixing the gyroscope through a bearing cover on a gyroscope support;
(2) opening the main switch of the device and setting the initial rotation speed n of the gyro0And recording; turning on a motor switch to enable the motor switch to operate, and turning on a photoelectric speed measuring sensor to measure the speed of the gyroscope;
(3) the driving wheel and the driven wheel of the clutch are combined by shifting the deflector rod, the motor drives the gyroscope to start rotating, and the rotating speed of the gyroscope exceeds a preset rotating speed value n0Then, the running key of the timer is turned on, the clutch is cut off, the spinning top starts to decelerate, and when the spinning top decelerates to a preset rotating speed n0The time is counted by the timer until the gyro is completely static, and the deceleration time t of the gyro under the condition of only friction resistance is recorded0Resetting the timer after recording;
(4) according to n0、t0And moment of inertia I of gyro, from the theorem of angular momentumCalculating average friction resistance moment M of gyrof；
(5) Rotating the micrometer screw rod, firstly contacting the electromagnet with the side surface of the gyroscope, then rotating backwards to enable the electromagnet to have a certain distance with the surface of the gyroscope, and recording the difference delta x between the two readings; adjusting the magnetic induction intensity of the electromagnet to a preset value B0(ii) a Setting and recording a gyro rotation speed preset value n;
(6) shifting the deflector rod again to close the clutch, driving the gyroscope to start rotating by the motor, opening a running key of the timer after the rotating speed of the gyroscope exceeds a preset rotating speed value n, cutting off the clutch, starting the deceleration of the gyroscope, starting timing by the timer when the gyroscope decelerates to the preset rotating speed n until the gyroscope is completely static, recording the deceleration time t of the gyroscope under the action of a radial magnetic field, and resetting the timer after recording;
(7) according to the moment of inertia I of the gyroscope, the distance delta x from the surface of the electromagnet to the surface of the gyroscope and the average friction resisting moment MfCalculating theoretical stop time t 'of the geometrical parameters of the gyroscope at a preset rotating speed n by theory, and comparing the theoretical stop time t' with the actually measured time t;
(8) and establishing a coordinate system by taking the rotating speed as an abscissa and the gyro stationary time as an ordinate, and drawing an n-t diagram under different magnetic field strengths in the same coordinate system.
The magnetic pole direction of the electromagnet is vertical to the angular velocity direction of the gyroscope, and if the magnetic field generated by the electromagnet is decomposed into an axial magnetic field consistent with the angular velocity direction of the gyroscope and a radial magnetic field vertical to the angular velocity direction, the radial magnetic field greatly influences the change of the electronic charge distribution on the gyroscope, so that the calculation of generating the dissipation power by using the ampere moment can be simplified.
Firstly, determining the diameter D, the thickness H, the mass m, the diameter D and the thickness H of an electromagnet core of a selected gyroscope;
the magnetic field of the electromagnet being perpendicular to the direction of the gyro angular velocity, i.e.
Figure BDA0002541362320000041
When the electromagnet and the top are relatively static, the magnetic induction intensity outside the magnet
Figure BDA0002541362320000042
Satisfy the requirement of
Figure BDA0002541362320000043
Thus, it is possible to provide
Figure BDA0002541362320000044
φmI.e., magnetic label potential, so:
Figure BDA0002541362320000045
therefore, it is
Figure BDA0002541362320000046
From conservation of charge:
Figure BDA0002541362320000047
taking the central point of the gyroscope as the origin, setting x and y coordinate axes in the radial direction, taking the gyroscope axis as the z coordinate axis, as shown in figure 8,
Figure BDA0002541362320000048
representing any point on the top
Figure BDA0002541362320000049
Rho represents any point on the gyroscope
Figure BDA00025413623200000410
The charge density of (d);
Figure BDA0002541362320000051
the current density in the gyroscope is shown, therefore, the charge density in the gyroscope does not change and is a steady current, the response time of electrons in metal is far shorter than the angular velocity change time, and therefore, the power dissipated by joule heat at this time is as follows:
Figure BDA0002541362320000052
wherein
Figure BDA0002541362320000053
Figure BDA0002541362320000054
Electric field intensity, H is gyro thickness, B1、B2、B3In an inertial coordinate system of B0Components in the x, y, z axes, respectively;
calculating a parameter kappa by adopting a magnetic charge viewpoint, assuming that equal amounts of magnetic charges with different signs are uniformly distributed on the upper ground and the lower ground of the cylindrical iron core, and taking the central axis of the cylindrical iron core as a z 'axis to establish a cylindrical coordinate system { z', r, theta }, wherein as shown in fig. 10, the magnetic standard potential generated by the magnetic charges at (r, theta) positions (including the upper surface and the lower surface) on the iron core at (x, y, z) points on the gyroscope is as follows:
Figure BDA0002541362320000055
l-y in the formula is delta x, k is undetermined proportionality coefficient;
the total magnetic index potential and magnetic induction at (x, y, z) points on the gyroscope are:
Figure BDA0002541362320000056
Figure BDA0002541362320000057
in a radial magnetic field, the spinning top will experience a friction drag torque of the bearing in addition to the ampere drag torque, but since the bearing's limit speed is not reached far, the average friction drag torque M can be usedfInstead of the total friction drag torque during rotation of the gyroscope, the power dissipated by friction is P0＝-Mfω；
Calculating the geometrical parameters of the gyroscope to obtain the moment of inertia of the gyroscope along the rotating shaft as I, and then carrying out energy conservation:
Figure BDA0002541362320000061
obtaining by solution:
Figure BDA0002541362320000062
when no magnetic field is applied, it can be simplified to
Figure BDA0002541362320000063
Omega is the angular velocity of the gyroscope, gamma is the conductivity of the metal, omega0For the initial angular velocity, the average frictional drag torque M can be calculated from the above equationf；
Order to
Figure BDA0002541362320000064
Theoretical stopping times can be obtained:
Figure BDA0002541362320000065
wherein
Figure BDA0002541362320000066
The parameters a, b can be calculated by a numerical integration calculation program running on Wolfram Mathematica, as follows:
Figure BDA0002541362320000067
B1＝D[φ,x]；B2＝D[φ,y]；B3＝D[φ,z]；
Figure BDA0002541362320000071
the program generates a numerical integration parameter table, and a and b can be calculated according to the known parameters calculated by the program in the table; the calculation process here involves only the conversion of parameters.
The invention has the beneficial effects that:
the measuring device provided by the invention utilizes the eddy current braking effect to carry out experiments, the experimental phenomenon is visual and vivid, and the operation and teaching practice of students are facilitated; the invention can adjust the magnetic induction intensity of the electromagnet, the distance between the electromagnet and the gyroscope, the rotating speed of the gyroscope and change the material of the gyroscope, carries out comprehensive experiments by controlling four variables, and has wider application range and better experimental and teaching effects.
Drawings
FIG. 1 is a first general structural diagram of the present invention;
FIG. 2 is a schematic view of the overall structure of the present invention;
FIG. 3 is a third schematic structural view of the present invention;
FIG. 4 is a fourth schematic structural view of the present invention;
FIG. 5 is a schematic view of a base structure according to the present invention;
FIG. 6 is a schematic view of the structure of a first gear, a first bearing, a toggle device, a clutch and a gyroscope according to the present invention;
FIG. 7 is a schematic structural view of a first bearing and a toggle device according to the present invention;
FIG. 8 is a schematic view of the structure of the shift fork and the shift lever of the present invention;
FIG. 9 is a schematic view of an electromagnet and a top according to the present invention;
FIG. 10 is a schematic diagram of a cylindrical coordinate system established for the electromagnet core according to the present invention;
1. base 2, first bearing 3, clutch 4, first gear 5, top
6. Motor 7, second gear 8, micrometer screw 9, electromagnet 10 and control system
11. First bearing support 12, gyro support 13, micrometer screw rod support 14, sleeve
15. Driving wheel 16, driving shaft 17, driven wheel 18, gear shaft 19 and toggle device
20. Bearing 21, photoelectric speed measuring sensor 22, upper fastening ring 23 and lower fastening ring
24. Second bearing 25, shifting fork 26, shift lever 27, retainer ring 28 and rotating shaft
29. Return spring 30, display screen 31, button 32, casing 33, gag lever post
34. Limiting groove 35, bearing cover 36 and shaft hole.
Detailed Description
As shown in fig. 1-10:
the invention provides an eddy current braking law measuring device based on a radial magnetic field, which comprises a base 1, a first bearing 2, a clutch 3, a first gear 4, a gyroscope 5, a motor 6, a second gear 7, a micrometer screw 8, an electromagnet 9 and a control system 10, wherein the base 1 is provided with a first bearing support 11, a gyroscope support 12 and a micrometer screw support 13; the outer ring of the first bearing 2 is fixed on the first bearing bracket 11, and the inner ring is provided with a sleeve 14; the clutch 3 comprises a driving wheel 15, a driving shaft 16 and a driven wheel 17, wherein the driving wheel 15 is connected with the driving shaft 16, and the driven wheel 17 is connected with a shaft lever at one side of the gyroscope 5; a gear shaft 18 of the first gear 4 passes through the sleeve 14 to be connected with a driving shaft 16 of the clutch 3, and a toggle device 19 is sleeved on the driving shaft 16 of the clutch 3; the gyroscope 5 is erected on the gyroscope support 12 through shaft rods on two sides, and the shaft rods are connected with the gyroscope support 12 through bearings 20; the motor 6 is arranged at the lower part of the first bearing bracket 11, the output shaft of the motor 6 is connected with the second gear 7, and the second gear 7 is meshed with the first gear 4; the micrometric screw 8 is horizontally fixed on the micrometric screw bracket 13, the front end of the micrometric screw 8 is connected with the electromagnet 9, and the axis of the electromagnet 9 is opposite to the radial direction of the gyroscope 5; the control system 10 is arranged on the base 1 and is connected with the motor 6, the power supply and the electromagnet 9 through leads; the precision of the micrometer screw 8 distance can be controlled at 0.01 mm.
The photoelectric speed measuring sensor 21 is arranged on the gyro bracket 12, is connected with the control system 10 through a lead, measures the revolution number of the gyro 5 and transmits the revolution number to the control system 10.
The shifting device 19 comprises an upper fastening ring 22, a lower fastening ring 23, a second bearing 24, a shifting fork 25 and a shifting lever 26, wherein the upper fastening ring 22 and the lower fastening ring 23 are fastened and fixed on the outer ring of the second bearing 24 through bolts, the inner ring of the second bearing 24 is sleeved on the driving shaft 16 of the clutch 3, two retaining rings 27 are arranged on the driving shaft 16, and the retaining rings 27 are positioned on two sides of the second bearing 24 and play a role in limiting; the shifting fork 25 is connected with the upper fastening ring 22 and the lower fastening ring 23, and the shifting rod 26 is connected with the shifting fork 25; the deflector rod 26 is provided with a rotating shaft 28, the rotating shaft 28 is inserted into a shaft hole 36 on the base 1, and the rotating shaft 28 enables the deflector rod 26 to form a lever effect; a return spring 29 is arranged between the shifting rod 26 and the base 1, one end of the return spring 29 is fixed on the base, the other end of the return spring 29 is abutted against the shifting rod 26, a limiting rod 33 can be arranged at the lower part of the shifting rod 26, the limiting rod 33 is positioned in a limiting groove 34 fixed on the base to limit the shifting range and the shifting path of the shifting rod 26, and the return spring 29 can be abutted against the limiting rod 33.
The control system 10 comprises a processor, a motor driver, a display screen 30 and keys 31, wherein the motor driver, the display screen 30 and the keys 31 are respectively connected with the processor, the motor driver is also connected with the motor 6, and the processor outputs control signals to drive the motor to rotate and control the rotating speed through the motor driver.
The display screen 30 respectively displays the magnetic induction intensity and time of the electromagnet 9, the preset gyro rotating speed and the current gyro rotating speed; the key 31 comprises an increase key and a decrease key of the magnetic induction intensity of the electromagnet 9, an increase key and a decrease key of the preset gyro rotation speed, an operation key and a clear key of a timer, an on-off key of the motor 6 and a power key of an instrument; the magnetic induction intensity of the electromagnet 9 is adjusted through an increase key and a decrease key of the magnetic induction intensity and is displayed on the display screen 30, the rotating speed of the gyro 5 is adjusted by controlling the rotating speed of the motor 6 through the increase key and the decrease key of the rotating speed of the gyro, and the revolution number is measured through the photoelectric speed measuring sensor 21 and is displayed on the display screen 30.
The base 1 is provided with a shell 32, the shell 32 covers the first gear 4 to the clutch 3, and the shifting lever 26 of the shifting device 19 extends out of an opening at the side edge of the shell 32, so that shifting is facilitated.
The upper end of the top support 12 is provided with a bearing cover 35, and the bearing cover 35 is connected with the top support 12 through screws to fix a bearing on a shaft rod of the top 5.
The working principle of the device of the invention is as follows:
the first gear 4 and the clutch 3 are connected into a whole, and a gear shaft 18 of the first gear 4 can radially displace in the sleeve 14 of the first bearing 2; when the shift lever 26 is shifted, the shift lever 26 drives the upper fastening ring 22 and the lower fastening ring 23 to move in reverse directions through the shift fork 25 under the action of the rotating shaft 28, the driving wheel 15 of the clutch 3 is pushed to move towards the driven wheel 17 to be in contact combination with the driven wheel 17, and therefore the motor 6 drives the torque to the gyroscope 5 through the second gear 7, the first gear 4 and the clutch 3 in sequence to rotate; when the shift lever 26 is released, the shift lever 26 is reset by the return spring 29, and the driving pulley 15 of the clutch 3 is driven to separate from the driven pulley 17.
The invention provides a measuring method of an eddy current braking law measuring device based on a radial magnetic field, which comprises the following steps: the method comprises the following steps:
(1) selecting a diameter D of 49.6mm, a thickness H of 6.578mm, a mass m of 115g and a moment of inertia I of 354g cm2A copper alloy gyroscope 15 with a conductivity γ of 58mS/m, wherein the gyroscope 5 is fixed through a bearing cover 35 on the gyroscope support 12; the diameter d of the electromagnet is 6.986mm, and the thickness h of the head iron core is 5.000 mm;
(2) the main switch of the device is turned on, and the initial rotating speed n of the gyro 5 is set0And record n01000 r/min; turning on a switch of the motor 6 to operate, and turning on the photoelectric speed measuring sensor 21 to measure the speed of the gyroscope 5;
(3) the deflector rod 26 is pulled to enable the driving wheel 15 of the clutch 3 to be combined with the driven wheel 17, the motor 6 drives the spinning top 5 to start to rotate, and the spinning top 5 is waited to rotate at the speed exceeding the preset rotating speed value n0Then, the running key of the timer is turned on, the clutch 3 is cut off, the spinning top 5 starts to decelerate, and when the spinning top 5 decelerates to the preset rotating speed n0In the meantime, the timer starts to time until the spinning top 5 is completely static, and the deceleration time t of the spinning top 5 under the condition of only friction resistance is recorded0After recording, resetting the timer for 17.32 s;
(4) according to n0、t0And the moment of inertia I of the gyro 5, and the average friction resisting moment M of the gyro 5 is calculated by the theorem of angular momentumf＝2.14×10-4N·m；
(5) Rotating micrometer screw 8, contacting electromagnet 9 with the side surface of gyroscope 5, rotating backwards to make electromagnet 9 spaced from gyroscope 5, and recording twoThe difference Δ x between the sub-readings is 4.000 mm; adjusting the magnetic induction intensity of the electromagnet 9 to a preset value B0144 mT; setting and recording a preset value n of the rotating speed of the gyroscope 5 as 4775 r/min;
(6) shifting the shift lever 26 again to close the clutch 3, driving the gyroscope 5 to rotate by the motor 6, opening a running key of the timer after the rotating speed of the gyroscope 5 exceeds a rotating speed preset value n, cutting off the clutch 3, starting deceleration of the gyroscope 5, starting timing by the timer when the gyroscope 5 decelerates to the preset rotating speed n until the gyroscope 5 is completely static, recording the deceleration time t of the gyroscope 5 under the action of a radial magnetic field as 47.56s, and resetting the timer after recording;
(7) according to the moment of inertia I of the gyroscope 5, the distance delta x from the surface of the electromagnet 9 to the surface of the gyroscope 5 and the average friction resisting moment MfCalculating theoretical stop time t 'of the geometrical parameters of the gyroscope 5 at a preset rotating speed n in a theoretical way to be 44.77s, and comparing the theoretical stop time t' with the actually measured time t;
(8) and establishing a coordinate system by taking the rotating speed as an abscissa and the static time of the gyroscope 5 as an ordinate, and drawing an n-t diagram under different magnetic field strengths in the same coordinate system.

Claims (10)

1. The utility model provides an eddy current braking law survey device based on radial magnetic field which characterized in that: the device comprises a base, a first bearing, a clutch, a first gear, a gyroscope, a motor, a second gear, a micrometric screw, an electromagnet and a control system, wherein a first bearing support, a gyroscope support and a micrometric screw support are arranged on the base; the outer ring of the first bearing is fixed on the first bearing support, and the inner ring of the first bearing is provided with a sleeve; the clutch comprises a driving wheel, a driving shaft and a driven wheel, the driving wheel is connected with the driving shaft, and the driven wheel is connected with a shaft lever at one side of the gyroscope; a gear shaft of the first gear penetrates through the sleeve to be connected with a driving shaft of the clutch, and a shifting device is sleeved on the driving shaft of the clutch; the gyroscope is erected on the gyroscope support through shaft levers on two sides, and the shaft levers are connected with the gyroscope support through bearings; the motor is arranged at the lower part of the first bearing bracket, an output shaft of the motor is connected with a second gear, and the second gear is meshed with the first gear; the micrometer screw rod is horizontally fixed on the micrometer screw rod bracket, the front end of the micrometer screw rod is connected with the electromagnet, and the axis of the electromagnet is opposite to the radial direction of the gyroscope; the control system is arranged on the base and is connected with the motor, the power supply and the electromagnet through wires.
2. An eddy current braking law measuring device based on a radial magnetic field according to claim 1, wherein: the photoelectric speed measuring sensor is arranged on the gyro bracket, is connected with the control system through a wire, measures the revolution number of the gyro and transmits the revolution number to the control system.
3. An eddy current braking law measuring device based on a radial magnetic field according to claim 1, wherein: the shifting device comprises an upper fastening ring, a lower fastening ring, a second bearing, a shifting fork and a shifting lever, wherein the upper fastening ring and the lower fastening ring are fastened and fixed on the outer ring of the second bearing; the shifting fork is connected with the upper fastening ring and the lower fastening ring, and the shifting lever is connected with the shifting fork; the deflector rod is provided with a rotating shaft which is inserted in a shaft hole on the base; a return spring is arranged between the deflector rod and the base.
4. An eddy current braking law measuring device based on a radial magnetic field according to claim 1, wherein: the control system comprises a processor, a motor driver, a display screen and keys, wherein the motor driver, the display screen and the keys are respectively connected with the processor, and the motor driver is also connected with the motor.
5. An eddy current braking law measurement apparatus based on a radial magnetic field according to claim 4, wherein: the display screen respectively displays the magnetic induction intensity and time of the electromagnet, a preset gyro rotating speed and a current gyro rotating speed; the keys comprise an increase key and a decrease key of the magnetic induction intensity of the electromagnet, an increase key and a decrease key of the preset gyro rotation speed, an operation key and a clear key of the timer, an on-off key of the motor and a power key of the instrument.
6. An eddy current braking law measuring device based on a radial magnetic field according to claim 1, wherein: the base is provided with a shell, the shell covers the first gear and the clutch, and a shifting rod of the shifting device extends out of an opening at the side edge of the shell.
7. An eddy current braking law measuring device based on a radial magnetic field according to claim 1, wherein: the upper end of the top support is provided with a bearing cover, and the bearing cover is connected with the top support through a screw to fix a bearing on the top shaft lever.
8. A measuring method of an eddy current braking law measuring device based on a radial magnetic field comprises the following steps: the method is characterized in that: the method comprises the following steps:
(1) selecting a gyroscope, and fixing the gyroscope through a bearing cover on a gyroscope support;
(2) opening the main switch of the device and setting the initial rotation speed n of the gyro0And recording; turning on a motor switch to enable the motor switch to operate, and turning on a photoelectric speed measuring sensor to measure the speed of the gyroscope;
(3) the driving wheel and the driven wheel of the clutch are combined by shifting the deflector rod, the motor drives the gyroscope to start rotating, and the rotating speed of the gyroscope exceeds a preset rotating speed value n0Then, the running key of the timer is turned on, the clutch is cut off, the spinning top starts to decelerate, and when the spinning top decelerates to a preset rotating speed n0The time is counted by the timer until the gyro is completely static, and the deceleration time t of the gyro under the condition of only friction resistance is recorded0Resetting the timer after recording;
(4) according to n0、t0And the gyro moment of inertia I, the average friction resisting moment M of the gyro is calculated by the theorem of angular momentumf；
(5) Rotating the micrometer screw rod, firstly contacting the electromagnet with the side surface of the gyroscope, then rotating backwards to enable the electromagnet to have a certain distance with the surface of the gyroscope, and recording the difference delta x between the two readings; adjusting the magnetic induction intensity of the electromagnet to a preset value B0(ii) a Setting and recording a gyro rotation speed preset value n;
(6) shifting the deflector rod again to close the clutch, driving the gyroscope to start rotating by the motor, opening a running key of the timer after the rotating speed of the gyroscope exceeds a preset rotating speed value n, cutting off the clutch, starting the deceleration of the gyroscope, starting timing by the timer when the gyroscope decelerates to the preset rotating speed n until the gyroscope is completely static, recording the deceleration time t of the gyroscope under the action of a radial magnetic field, and resetting the timer after recording;
(7) according to the moment of inertia I of the gyroscope, the distance delta x from the surface of the electromagnet to the surface of the gyroscope and the average friction resisting moment MfCalculating theoretical stop time t 'of the geometrical parameters of the gyroscope at a preset rotating speed n by theory, and comparing the theoretical stop time t' with the actually measured time t;
(8) and establishing a coordinate system by taking the rotating speed as an abscissa and the gyro stationary time as an ordinate, and drawing an n-t diagram under different magnetic field strengths in the same coordinate system.
9. The method according to claim 8, wherein the eddy current braking law determining apparatus based on the radial magnetic field comprises: the method is characterized in that:
selecting a gyroscope, and determining the diameter D of the gyroscope, the thickness H of the gyroscope, the mass m of the gyroscope, the diameter D of an electromagnet iron core and the thickness H of the electromagnet iron core;
the magnetic field of the electromagnet being perpendicular to the direction of the gyro angular velocity, i.e.
Figure FDA0002541362310000031
When the electromagnet and the top are relatively static, the magnetic induction intensity outside the magnet
Figure FDA0002541362310000032
Satisfy the requirement of
Figure FDA0002541362310000033
Thus, it is possible to provide
Figure FDA0002541362310000034
φmI.e., magnetic label potential, so:
Figure FDA0002541362310000035
therefore, it is
Figure FDA0002541362310000036
From conservation of charge:
Figure FDA0002541362310000037
taking the central point of the gyroscope as the origin, setting x and y coordinate axes in the radial direction, taking the gyroscope axis as the z coordinate axis,
Figure FDA0002541362310000038
representing any point on the top
Figure FDA0002541362310000039
Rho represents any point on the gyroscope
Figure FDA00025413623100000310
The charge density of (d);
Figure FDA00025413623100000311
the current density in the gyroscope is shown, so that the charge density in the gyroscope does not change and is a constant current; the power dissipated by joule heating at this time is:
Figure FDA0002541362310000041
wherein
Figure FDA0002541362310000042
Figure FDA0002541362310000043
Electric field intensity, H is gyro thickness, B1、B2、B3In an inertial coordinate system of B0Components in the x, y, z axes, respectively;
calculating a parameter k by adopting a magnetic charge viewpoint, assuming that the upper ground and the lower ground of the cylindrical iron core are uniformly distributed with equal amounts of magnetic charges with different signs, and taking the central axis of the cylindrical iron core as a z 'axis to establish a cylindrical coordinate system { z', r, theta }, wherein the magnetic standard potential generated by the magnetic charges at the (r, theta) position (including the upper surface and the lower surface) on the iron core at the (x, y, z) point on the gyroscope is as follows:
Figure FDA0002541362310000044
l-y in the formula is delta x, k is undetermined proportionality coefficient;
the total magnetic index potential and magnetic induction at (x, y, z) points on the gyroscope are:
Figure FDA0002541362310000045
Figure FDA0002541362310000046
in a radial magnetic field, the spinning top is subjected to an ampere resistance torque and also to a friction resistance torque of the bearing, and an average friction resistance torque M can be usedfInstead of the total friction drag torque during rotation of the gyroscope, the power dissipated by friction is P0＝-Mfω；
Calculating the geometrical parameters of the gyroscope to obtain the moment of inertia of the gyroscope along the rotating shaft as I, and then carrying out energy conservation:
Figure FDA0002541362310000051
obtaining by solution:
Figure FDA0002541362310000052
when no magnetic field is applied, it can be simplified to
Figure FDA0002541362310000053
Omega is the angular velocity of the gyroscope, gamma is the conductivity of the metal, omega0For the initial angular velocity, the average frictional drag torque M can be calculated from the above equationf；
Order to
Figure FDA0002541362310000054
Theoretical stopping times can be obtained:
Figure FDA0002541362310000055
wherein
Figure FDA0002541362310000056
10. The method for determining the eddy current braking law based on the radial magnetic field according to claim 9: the method is characterized in that: the parameters a, b can be calculated by a numerical integration calculation program running on Wolfram Mathematica, as follows:
Figure FDA0002541362310000057
B1＝D[φ,x]；B2＝D[φ,y]；B3＝D[φ,z]；
Figure FDA0002541362310000061
the program generates a numerical integration parameter table, and a and b can be calculated according to the known parameters calculated by the program in the table; the calculation process here involves only the conversion of parameters.
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