CN111554162B - 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 PDFInfo
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- H—ELECTRICITY
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Abstract
The invention relates to a radial magnetic field-based eddy current braking law measuring device and a radial magnetic field-based eddy current braking law measuring method, and aims to solve the problem that a device capable of intuitively measuring the radial magnetic field-based eddy current braking law is lacking at present. The measuring device 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 measuring method is used for reading out the current magnetic field intensity by setting a preset rotating speed, measuring the gyroscope resting time, plotting by taking the rotating speed as an abscissa and the gyroscope resting time as an ordinate, plotting n-t diagrams under different magnetic field intensities under the same coordinate system, and comparing with a theoretical curve. The measuring device provided by the invention performs experiments by utilizing the eddy current braking effect, and by combining the measuring method provided by the invention, the speed-down motion law of the gyroscope under the influence of the eddy current braking effect of the radial magnetic field can be accurately predicted, and comprehensive experiments are performed, so that the experimental and teaching effects are better.
Description
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
With the continuous development of science and technology, various magnetic field intensity measuring instruments are developed on the market, wherein a tesla meter represented by a Hall element is the most prominent, and adopts a Hall effect measuring principle, so that the device has the advantages of simple structure, convenient measurement and higher precision, but the device has higher cost, insufficient measuring intuitiveness and is not beneficial to an experimenter to recognize the experimental principle; the magnetic field intensity tester manufactured by adopting a current balance method applies the principle that an electrified lead is stressed in a magnetic field, and measures the magnetic induction intensity according to the moment balance condition, but the structure of the tester manufactured by the measuring method is complex, and the tester is generally only used for qualitative experiments for enabling students to know the electromagnetic induction principle, and the precision of the tester in certain measuring intervals is relatively low due to the limitation of the design principle. The eddy current braking is widely applied in actual production and life, but a device capable of intuitively measuring the eddy current braking law, particularly a device for measuring the eddy current braking law based on a radial magnetic field is lacking at present, so that the device and the method which are capable of designing a visual phenomenon, are convenient for teaching practice and student operation practice and can accurately measure the eddy current braking law are hoped.
Disclosure of Invention
In order to solve the technical problems, the invention provides an eddy current braking law measuring 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 bracket, a gyroscope bracket and a micrometer screw bracket; the outer ring of the first bearing is fixed on the first bearing bracket, and the inner ring is provided with a sleeve; the clutch comprises a driving wheel, a driving shaft and a driven wheel, wherein the driving wheel is connected with the driving shaft, and the driven wheel is connected with a shaft lever on one side of the gyroscope; the gear shaft of the first gear passes through the sleeve and is connected with the driving shaft of the clutch, and the driving shaft of the clutch is sleeved with a toggle device; the top is erected on the top support through shaft rods at two sides, and the shaft rods are connected with the top 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 the second gear, and the second gear is meshed with the first gear; the micrometer screw is horizontally fixed on the micrometer screw bracket, the front end of the micrometer screw 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 leads.
The photoelectric speed measuring sensor is arranged on the gyro bracket, is connected with the control system through a wire, measures the revolution of the gyro and transmits the revolution 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 rod, wherein the upper fastening ring and the lower fastening ring are buckled and fixed on an outer ring of the second bearing, an inner ring of the second bearing is sleeved on a driving shaft of the clutch, two check rings are arranged on the driving shaft, and the check rings are positioned on two sides of the second bearing to play a limiting role; the shifting fork is connected with the upper fastening ring and the lower fastening ring, and the shifting rod is connected with the shifting fork; the driving lever is provided with a rotating shaft which is inserted into a shaft hole positioned on the base, and the rotating shaft enables the driving lever to form leverage; 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, the preset gyro rotating speed and the current gyro rotating speed; the keys comprise an increasing key and a decreasing key of the magnetic induction intensity of the electromagnet, an increasing key and a decreasing key of the preset gyro rotating speed, an operation key and a zero clearing key of the timer, a switching key of the motor and a power key of the instrument; the magnetic induction intensity of the electromagnet is adjusted through the increasing key and the decreasing key of the magnetic induction intensity and is displayed on the display screen, the rotating speed of the motor is controlled through the increasing key and the decreasing key of the rotating speed of the gyroscope so as to adjust the rotating speed of the gyroscope, and the revolution is measured through the photoelectric speed measuring sensor and is displayed on the display screen.
The base is provided with a shell, the shell is covered above the first gear and the clutch, and a deflector rod of the poking device extends out from 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 the bearing on the top shaft lever.
The working principle of the device is as follows:
the first gear is connected with the clutch into a whole, and a gear shaft of the first gear can radially displace in a sleeve of the first bearing; when the driving lever is shifted, the driving lever drives the upper fastening ring and the lower fastening ring to reversely move under the action of the rotating shaft through the shifting fork to push 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 top is rotated by torque of the gyro transmission motor through the second gear, the first gear and the clutch in sequence; when the driving lever is released, the driving 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 method for measuring 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 top, and fixing the top through a bearing cover on a top support;
(2) Turning on the main switch of the device to set the initial rotation speed n of the gyroscope 0 And recording; opening a motor switch to enable the motor switch to operate, and opening a photoelectric speed measuring sensor to measure the speed of the gyroscope;
(3) The driving lever is shifted to enable the driving wheel and the driven wheel of the clutch to be combined, the motor drives the top to start rotating, and when the rotating speed of the top exceeds a rotating speed preset value n 0 After that, the operation key of the timer is opened, the clutch is cut off, the gyroscope starts to decelerate, and when the gyroscope decelerates to the preset rotating speed n 0 When the gyroscope is completely static, the time is started by the timer, and the deceleration time t of the gyroscope when only friction resistance exists is recorded 0 Resetting the timer after recording;
(4) According to n 0 、t 0 And the moment of inertia I of the gyroscope, calculate the average friction resistance moment M of the gyroscope according to the angular momentum theorem f ；
(5) Rotating the micrometer screw, firstly contacting the electromagnet with the side surface of the gyroscope, then rotating backwards to enable the electromagnet to have a certain distance from the surface of the gyroscope, and recording the difference deltax between two readings; adjusting the magnetic induction intensity of the electromagnet to be a preset value B 0 The method comprises the steps of carrying out a first treatment on the surface of the Setting and recording a gyro rotating speed preset value n;
(6) The driving lever is stirred again to enable the clutch to be closed, the motor drives the gyro to start rotating, after the rotating speed of the gyro exceeds a rotating speed preset value n, an operation key of the timer is turned on, the clutch is cut off, the gyro starts to decelerate, when the gyro decelerates to the preset rotating speed n, the timer starts to count until the gyro is completely stationary, the deceleration time t of the gyro under the action of a radial magnetic field is recorded, and the timer is cleared after the record is completed;
(7) According to the rotational 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 resistance moment M f Theoretical stop time t' of the gyro geometric parameter under the preset rotating speed n is calculated theoretically, and the theoretical stop time t is compared with the actually measured time t;
(8) And establishing a coordinate system by taking the rotating speed as an abscissa and the gyro resting time as an ordinate, and drawing n-t diagrams under different magnetic field intensities under the same coordinate system.
The magnetic pole direction of the electromagnet is perpendicular to the angular velocity direction of the gyroscope, 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 perpendicular 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 dissipation power by utilizing ampere moment can be simplified.
Firstly, determining the diameter D, the gyro thickness H, the gyro mass m, the electromagnet core diameter D and the electromagnet core thickness H of a selected gyro;
the magnetic field of the electromagnet being perpendicular to the direction of the angular velocity of the gyroscope, i.eWhen the electromagnet and the gyroscope are relatively stationary, the magnetic induction of the outside of the magnet is +.>Satisfy->Thus->φ m I.e. magnetic marking, so:
therefore, it isConservation of charge:
with the center point of the gyroscope as the origin, x and y coordinate axes are set in the radial direction, and the gyroscope axis as the z coordinate axis, as shown in figure 8,representing any point on the top +.>ρ represents any point on the top +.>Charge density at; />The current density in the gyroscope is the constant current, the response time of electrons in metal is far less than the change time of angular velocity, so that the power dissipated by the joule heat at the moment is as follows:
wherein the method comprises the steps of The electric field strength, H is the thickness of the gyroscope, B 1 、B 2 、B 3 For B in inertial coordinate system 0 Components in the x, y, z axes, respectively;
calculating a parameter kappa by adopting a magnetic charge viewpoint, assuming that equal amounts of magnetic charges are uniformly distributed on the upper surface and the lower surface of a cylindrical iron core, taking the central axis of the cylindrical iron core as a z 'axis, and establishing a cylindrical coordinate system { z', r and theta }, as shown in fig. 10, the magnetic marks generated by the points (x, y and z) of the magnetic charges (comprising the upper surface and the lower surface) on the iron core are as follows:
wherein l-y is delta x, and k is a coefficient of proportionality to be determined;
the total magnetic mark potential and magnetic induction intensity of the (x, y, z) points on the gyroscope are as follows:
in the radial magnetic field, the rotating gyroscope can be subjected to ampere resistance moment and also can be subjected to friction resistance moment of a bearing, but the average friction resistance moment M can be used because the limit rotating speed of the bearing is far less than the limit rotating speed f To replace the total friction resistance moment in the spinning process of the top, the friction dissipation power is P 0 ＝-M f ω；
The moment of inertia of the gyroscope along the rotating shaft is calculated by the geometric parameters of the gyroscope to be I, and then the energy conservation is carried out:
and (3) solving to obtain:
when no magnetic field is applied, it can be simplified to
Omega is the angular velocity of the gyroscope, gamma is the electrical conductivity of the metal, omega 0 For the initial angular velocity, the average friction resistance moment M can be calculated from the above f ；
Order theTheoretical stopping time can be obtained:
wherein the method comprises the steps of
The numerical integration calculation program running on Wolfram Mathematica can calculate the parameters a, b as follows:
B1＝D[φ,x]；B2＝D[φ,y]；B3＝D[φ,z]；
the program generates a numerical integral 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, the operation and teaching practice of students are facilitated, and the speed-down motion law of the gyroscope under the influence of the eddy current braking effect of the radial magnetic field can be accurately predicted by combining the measuring method provided by the invention, so that the device is beneficial to being popularized and used as an experimental teaching instrument; 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 the material replacement of the gyroscope, and can carry out comprehensive experiments by controlling four variables, thereby having wider application range and better experimental and teaching effects.
Drawings
FIG. 1 is a schematic diagram of the overall structure of the present invention;
FIG. 2 is a schematic diagram of the whole structure of the present invention;
FIG. 3 is a third schematic diagram of the structure of the present invention;
FIG. 4 is a schematic diagram of a fourth embodiment of the present invention;
FIG. 5 is a schematic view of a base structure of the present invention;
FIG. 6 is a schematic view of the first gear, first bearing, toggle, clutch and gyroscope of the present invention;
FIG. 7 is a schematic view of a first bearing and toggle arrangement of the present invention;
FIG. 8 is a schematic view of a fork and lever structure according to the present invention;
FIG. 9 is a schematic diagram of an electromagnet and gyroscope structure according to the present invention;
FIG. 10 is a schematic diagram of an electromagnet core build-up cylinder coordinate system according to the present invention;
1. base 2, first bearing 3, clutch 4, first gear 5, top
6. The motor 7, the second gear 8, the micrometer screw 9, the electromagnet 10 and the control system
11. First bearing bracket 12, gyro bracket 13, micrometer screw bracket 14 and sleeve
15. Driving wheel 16, driving shaft 17, driven wheel 18, gear shaft 19 and toggle device
20. Bearing 21, photoelectric speed sensor 22, upper fastening ring 23 and lower fastening ring
24. Second bearing 25, shift fork 26, shift lever 27, retainer 28 and rotating shaft
29. Return spring 30, display 31, key 32, casing 33 and stop lever
34. Limit groove 35, bearing cap 36, 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 bracket 11, a gyroscope bracket 12 and a micrometer screw bracket 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 on one side of the top 5; the gear shaft 18 of the first gear 4 passes through the sleeve 14 to be connected with the driving shaft 16 of the clutch 3, and the driving shaft 16 of the clutch 3 is sleeved with a toggle device 19; the top 5 is erected on the top support 12 through shaft rods at two sides, and the shaft rods are connected with the top support 12 through bearings 20; the motor 6 is arranged at the lower part of the first bearing bracket 11, an 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 micrometer screw 8 is horizontally fixed on the micrometer screw bracket 13, the front end of the micrometer 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 accuracy of the distance of the micrometer screw 8 can be controlled to be 0.01mm.
The photoelectric speed sensor 21 is arranged on the gyro bracket 12, is connected with the control system 10 through a wire, measures the revolution of the gyro 5 and transmits the revolution to the control system 10.
The stirring device 19 comprises an upper fastening ring 22, a lower fastening ring 23, a second bearing 24, a shifting fork 25 and a stirring rod 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 check rings 27 are arranged on the driving shaft 16, and the check rings 27 are positioned on two sides of the second bearing 24 to play a limiting role; 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 positioned on the base 1, and the rotating shaft 28 enables the deflector rod 26 to form leverage; a return spring 29 is arranged between the deflector 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 deflector rod 26, a limiting rod 33 can be arranged at the lower part of the deflector rod 26, the limiting rod 33 is positioned in a limiting groove 34 fixed on the base, the stirring range and path of the deflector rod 26 are limited, 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 displays the magnetic induction intensity, time, preset gyro rotation speed and current gyro rotation speed of the electromagnet 9 respectively; the keys 31 comprise an increasing key and a decreasing key of the magnetic induction intensity of the electromagnet 9, an increasing key and a decreasing key of the preset gyro rotating speed, an operation key and a zero clearing key of a timer, a switch key of the motor 6 and a power key of an instrument; the magnetic induction intensity of the electromagnet 9 is adjusted through the increasing key and the decreasing key of the magnetic induction intensity and is displayed on the display screen 30, the rotating speed of the gyro 5 is adjusted through the increasing key and the decreasing key of the rotating speed of the gyro to control the rotating speed of the motor 6, and the rotating speed is measured through the photoelectric speed measuring sensor 21 and is displayed on the display screen 30.
The base 1 is provided with the shell 32, the shell 32 is covered above the first gear 4 and the clutch 3, and the deflector rod 26 of the poking device 19 extends out of the side opening of the shell 32, so that poking 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 a screw to fix a bearing on the shaft lever of the top 5.
The working principle of the device is as follows:
the first gear 4 is connected with the clutch 3 into a whole, and a gear shaft 18 of the first gear 4 can radially displace in a sleeve 14 of the first bearing 2; when the driving lever 26 is shifted, the driving lever 26 drives the upper fastening ring 22 and the lower fastening ring 23 to reversely move under the action of the rotating shaft 28 through the shifting fork 25 to push the driving wheel 15 of the clutch 3 to move towards the driven wheel 17 until being contacted and combined with the driven wheel 17, so that the motor 6 sequentially transmits torque to the gyroscope 5 through the second gear 7, the first gear 4 and the clutch 3 to rotate; when the deflector rod 26 is released, the deflector rod 26 is reset under the action of the return spring 29, and the driving wheel 15 of the clutch 3 is driven to be separated from the driven wheel 17.
The invention provides a method for measuring 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=49.6 mm, a thickness h= 6.578mm, a mass m=115 g, and a moment of inertia i=354 g·cm 2 A gyro 15 of copper alloy with conductivity gamma=58 mS/m, the gyro 5 is fixed by a bearing cover 35 on the gyro bracket 12; electromagnet diameter d= 6.986mm, head core thickness h=5.000 mm;
(2) Turning on the main switch of the device to set the initial rotation speed n of the top 5 0 And record, n 0 =1000 r/min; the motor 6 is turned on to operate, and the photoelectric speed sensor 21 is turned on to measure the speed of the gyroscope 5;
(3) The driving wheel 15 and the driven wheel 17 of the clutch 3 are combined by poking the poking rod 26, the motor 6 drives the top 5 to start rotating, and when the rotating speed of the top 5 exceeds the rotating speed preset value n 0 After that, the operation key of the timer is turned on, the clutch 3 is cut off, the gyro 5 starts to decelerate, and when the gyro 5 decelerates to the preset rotation speed n 0 When the top 5 is completely stationary, the time of the top 5 decelerating with friction resistance is recorded 0 =17.32 s, zero clearing the timer after recording;
(4) According to n 0 、t 0 And the moment of inertia I of the top 5, the average friction resistance moment M of the top 5 is calculated by the angular momentum theorem f ＝2.14×10 -4 N·m；
(5) Rotating the micrometer screw 8, firstly contacting the electromagnet 9 with the side surface of the gyroscope 5, then rotating backwards to enable the electromagnet 9 to have a certain distance from the surface of the gyroscope 5, and recording the difference delta x=4.000 mm between two readings; adjusting the magnetic induction intensity of the electromagnet 9 to be a preset value B 0 =144 mT; setting and recording a preset value n=4775r/min of the rotating speed of the gyroscope 5;
(6) The driving lever 26 is stirred again to enable the clutch 3 to be closed, the motor 6 drives the top 5 to start rotating, after the rotating speed of the top 5 exceeds the rotating speed preset value n, an operation key of a timer is turned on, the clutch 3 is cut off, the top 5 starts to decelerate, when the top 5 decelerates to the preset rotating speed n, the timer starts to count until the top 5 is completely static, the deceleration time t=47.56 s of the top 5 under the action of a radial magnetic field is recorded, and the timer is cleared after the record is completed;
(7) According to the moment of inertia I of the top 5, the distance delta x from the surface of the electromagnet 9 to the surface of the top 5 and the average friction resistance moment M f And theoretical stop time t '=44.77 s of the geometric parameter of the gyroscope 5 under the preset rotating speed n is calculated theoretically, and the theoretical stop time t' =44.77 s is compared with the actual measured time t;
(8) And establishing a coordinate system by taking the rotating speed as an abscissa and the rest time of the gyroscope 5 as an ordinate, and drawing n-t diagrams under different magnetic field intensities under the same coordinate system.
Claims (8)
1. An eddy current braking law measuring device based on radial magnetic field, its characterized in that: the micro-measuring device comprises a base, a first bearing, a clutch, a first gear, a gyroscope, a motor, a second gear, a micro-measuring screw, an electromagnet and a control system, wherein a first bearing bracket, a gyroscope bracket and a micro-measuring screw bracket are arranged on the base; the outer ring of the first bearing is fixed on the first bearing bracket, and the inner ring is provided with a sleeve; the clutch comprises a driving wheel, a driving shaft and a driven wheel, wherein the driving wheel is connected with the driving shaft, and the driven wheel is connected with a shaft lever on one side of the gyroscope; the gear shaft of the first gear passes through the sleeve and is connected with the driving shaft of the clutch, and the driving shaft of the clutch is sleeved with a toggle device; the top is erected on the top support through shaft rods at two sides, and the shaft rods are connected with the top 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 the second gear, and the second gear is meshed with the first gear; the micrometer screw is horizontally fixed on the micrometer screw bracket, the front end of the micrometer screw 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 leads;
the shifting device comprises an upper fastening ring, a lower fastening ring, a second bearing, a shifting fork and a shifting rod, wherein the upper fastening ring and the lower fastening ring are buckled and fixed on an outer ring of the second bearing, an inner ring of the second bearing is sleeved on a driving shaft of the clutch, two check rings are arranged on the driving shaft, and the check rings are positioned on two sides of the second bearing; the shifting fork is connected with the upper fastening ring and the lower fastening ring, and the shifting rod is connected with the shifting fork; the deflector rod is provided with a rotating shaft which is inserted into a shaft hole positioned on the base; a return spring is arranged between the deflector rod and the base.
2. The eddy current braking rule measuring device based on radial magnetic field as set forth in 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 of the gyro and transmits the revolution to the control system.
3. The eddy current braking rule measuring device based on radial magnetic field as set forth in 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.
4. The eddy current braking rule determining apparatus based on radial magnetic field as claimed in claim 3 wherein: the display screen respectively displays the magnetic induction intensity and time of the electromagnet, the preset gyro rotating speed and the current gyro rotating speed; the keys comprise an increasing key and a decreasing key of the magnetic induction intensity of the electromagnet, an increasing key and a decreasing key of the preset gyro rotating speed, an operation key and a zero clearing key of the timer, a switching key of the motor and a power key of the instrument.
5. The eddy current braking rule measuring device based on radial magnetic field as set forth in claim 1, wherein: the base is provided with a shell, the shell is covered above the first gear and the clutch, and a deflector rod of the poking device extends out from an opening at the side edge of the shell.
6. The eddy current braking rule measuring device based on radial magnetic field as set forth in 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 the bearing on the top shaft lever.
7. The method for determining an eddy current braking rule determining unit based on radial magnetic field according to any one of claims 1-6: the method is characterized in that: the method comprises the following steps:
(1) Selecting a top, and fixing the top through a bearing cover on a top support;
(2) Turning on the main switch of the device to set the initial rotation speed n of the gyroscope 0 And recording; opening a motor switch to enable the motor switch to operate, and opening a photoelectric speed measuring sensor to measure the speed of the gyroscope;
(3) The driving lever is shifted to enable the driving wheel and the driven wheel of the clutch to be combined, the motor drives the top to start rotating, and when the rotating speed of the top exceeds a rotating speed preset value n 0 After that, the operation key of the timer is opened, the clutch is cut off, the gyroscope starts to decelerate, and when the gyroscope decelerates to the preset rotating speed n 0 When the gyroscope is completely static, the time is started by the timer, and the deceleration time t of the gyroscope when only friction resistance exists is recorded 0 Resetting the timer after recording;
(4) According to n 0 、t 0 And the moment of inertia I of the gyroscope, calculate the average friction resistance moment M of the gyroscope according to the angular momentum theorem f ；
(5) Rotating the micrometer screw, firstly contacting the electromagnet with the side surface of the gyroscope, then rotating backwards to enable the electromagnet to have a certain distance from the surface of the gyroscope, and recording the difference deltax between two readings; adjusting the magnetic induction intensity of the electromagnet to be a preset value B 0 The method comprises the steps of carrying out a first treatment on the surface of the Setting and recording a gyro rotating speed preset value n;
(6) The driving lever is stirred again to enable the clutch to be closed, the motor drives the gyro to start rotating, after the rotating speed of the gyro exceeds a rotating speed preset value n, an operation key of the timer is turned on, the clutch is cut off, the gyro starts to decelerate, when the gyro decelerates to the preset rotating speed n, the timer starts to count until the gyro is completely stationary, the deceleration time t of the gyro under the action of a radial magnetic field is recorded, and the timer is cleared after the record is completed;
(7) According to the rotational 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 resistance moment M f Theoretical stop time t' of the gyro geometric parameter under the preset rotating speed n is calculated theoretically, and the theoretical stop time t is compared with the actually measured time t;
(8) And establishing a coordinate system by taking the rotating speed as an abscissa and the gyro resting time as an ordinate, and drawing n-t diagrams under different magnetic field intensities under the same coordinate system.
8. The method for determining the eddy current braking rule determining unit based on the radial magnetic field according to claim 7, wherein: the method is characterized in that:
step (1) selecting a gyroscope, and determining the diameter D, the thickness H, the mass m, the diameter D and the thickness H of an electromagnet core;
the magnetic field of the electromagnet being perpendicular to the direction of the angular velocity of the gyroscope, i.eWhen the electromagnet and the gyroscope are relatively stationary, the magnetic induction of the outside of the magnet is +.>Satisfy->Thus->φ m I.e. magnetic marking, so:
therefore, it isConservation of charge:
taking the center point of the gyroscope as an origin, setting x and y coordinate axes in the radial direction, taking the gyroscope axis as a z coordinate axis,representing any point on the topρ represents any point on the top +.>Charge density at; />The current density in the gyroscope is the current density in the gyroscope, so that the charge density in the gyroscope is not changed and is a steady current; the power dissipated by joule heat at this time is:
wherein the method comprises the steps of The electric field strength, H is the thickness of the gyroscope, B 1 、B 2 、B 3 For B in inertial coordinate system 0 Components in the x, y, z axes, respectively;
calculating a parameter kappa by adopting a magnetic charge viewpoint, assuming that equal amounts of magnetic charges are uniformly distributed on the upper surface and the lower surface of a cylindrical iron core, taking the central axis of the cylindrical iron core as a z 'axis, and establishing a cylindrical coordinate system { z', r and theta }, wherein the magnetic marks generated by (x, y and z) points of the magnetic charges (comprising the upper surface and the lower surface) on the iron core are as follows:
wherein l-y is delta x, and k is a coefficient of proportionality to be determined;
the total magnetic mark potential and magnetic induction intensity of the (x, y, z) points on the gyroscope are as follows:
in the radial magnetic field, the rotating gyroscope can be subjected to ampere resistance moment and also can be subjected to friction resistance moment of a bearing, and average friction resistance moment M can be used f To replace the total friction resistance moment in the spinning process of the top, the friction dissipation power is P 0 ＝-M f ω；
The moment of inertia of the gyroscope along the rotating shaft is calculated by the geometric parameters of the gyroscope to be I, and then the energy conservation is carried out:
and (3) solving to obtain:
when no magnetic field is applied, it can be simplified to
Omega is the angular velocity of the gyroscope, gamma is the electrical conductivity of the metal, omega 0 For the initial angular velocity, the average friction can be calculated from the aboveFriction moment M f ；
Order theTheoretical stopping time can be obtained:
wherein the method comprises the steps of
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