CN110779640B - Shaft torque measuring system and method based on Malus law - Google Patents
Shaft torque measuring system and method based on Malus law Download PDFInfo
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- CN110779640B CN110779640B CN201911149795.1A CN201911149795A CN110779640B CN 110779640 B CN110779640 B CN 110779640B CN 201911149795 A CN201911149795 A CN 201911149795A CN 110779640 B CN110779640 B CN 110779640B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L3/00—Measuring torque, work, mechanical power, or mechanical efficiency, in general
- G01L3/02—Rotary-transmission dynamometers
- G01L3/04—Rotary-transmission dynamometers wherein the torque-transmitting element comprises a torsionally-flexible shaft
- G01L3/08—Rotary-transmission dynamometers wherein the torque-transmitting element comprises a torsionally-flexible shaft involving optical means for indicating
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L3/00—Measuring torque, work, mechanical power, or mechanical efficiency, in general
- G01L3/24—Devices for determining the value of power, e.g. by measuring and simultaneously multiplying the values of torque and revolutions per unit of time, by multiplying the values of tractive or propulsive force and velocity
- G01L3/242—Devices for determining the value of power, e.g. by measuring and simultaneously multiplying the values of torque and revolutions per unit of time, by multiplying the values of tractive or propulsive force and velocity by measuring and simultaneously multiplying torque and velocity
Abstract
The invention provides a shaft torque measuring system based on Malus law, wherein a black box is detachably sleeved on a shaft to be measured, a closed and light-tight space is formed in the black box and is used as a measuring area, a measuring device in the shaft torque measuring system is arranged in the measuring area, and the structure is as follows: the supporting platform sleeved on the shaft to be measured through the first connecting sleeve is suspended outside the shaft to be measured, a laser, a first light-transmitting element and a light intensity detection element are arranged on the supporting platform from front to back at intervals along the axial direction of the shaft to be measured and the radial direction of the shaft to be measured with a gap, and a second light-transmitting element is supported by a second connecting sleeve detachably sleeved on the shaft to be measured, suspended outside the shaft to be measured and positioned between the first light-transmitting element and the light intensity detection element along the axial direction; the wireless data transmission device further comprises a wireless data transmission module, an output module and a display module, wherein the output module and the display module are electrically connected with the processor. The invention can solve the problems of low resolution, low sensitivity and high installation difficulty of the existing shaft torque measurement technology.
Description
Technical Field
The invention relates to the technical field of shaft torque measurement, in particular to a shaft torque measurement system and a shaft torque measurement method based on Malus law.
Background
The torque is a very important physical quantity in the field of mechanical transmission, can reflect the running condition of the whole mechanical system, and is one of typical parameters for ensuring the stable running of the transmission system. The measurement and analysis of the torque are also important means for ensuring the normal operation of various production equipment and auxiliary equipment, reducing energy consumption and improving efficiency, so that the occurrence of accidents can be reduced and the utilization rate of the production equipment can be increased inevitably by improving the accuracy of torque measurement, the real-time performance of torque monitoring and control and the reliability of torque abnormity analysis. In other words, online torque monitoring is of great significance to reduce unplanned maintenance time and accident rate, to analyze the efficiency of the accident or cause of the fault, and to improve production efficiency and economic efficiency.
With the progress of scientific technology and the development of production, the application field of torque measurement is more and more extensive, such as airplanes, ships, drilling, power generation equipment, metallurgical mining equipment and the like, and such as micromotors, household appliances, clock hairsprings and the like. Torque measurement is an indispensable content for development, quality inspection, optimal control, working condition monitoring, fault diagnosis and the like of various mechanical products. Accurate torque measurement plays an important role in shortening the development period of modern ship equipment, improving the performance of weapon equipment and reducing the use and guarantee cost. With the great improvement of the economic strength and the technical level of China, in the fields of civil use and national defense, on one hand, the number of the requirements of equipment such as automobiles, ships, airplanes and well drilling is greatly increased, and on the other hand, the requirement levels (including speed, tonnage, dynamic characteristics, safety and the like) of the equipment are greatly changed, so that more and higher requirements are also provided for torque measurement, and the development of a high-accuracy torque sensor is one of key technologies for improving the torque measurement precision.
For example, as ships are becoming larger, faster and more automated, the rapidity, efficiency and economy of ships have become important indexes for ship building, and as an important means for calculating conversion efficiency, the measurement of shaft power is a main parameter for newly built ships accepted by shipyards and shipowners. The running conditions of the ship are very complex, the matching of ship-machine-propeller has great influence on the performance of the main machine, when the ship is not matched with the propeller, the main machine may not reach the rated power, the ship cannot reach the designed navigational speed, or the main machine runs over the rated power, so that the main machine is overloaded and the service life is greatly shortened. The system for measuring the shaft power and the torque of the ship can know and detect the matching condition between the ship body, the host and the propeller by measuring the shaft power of the host under different working conditions, monitors the running state of the ship body in real time, and can diagnose the working state and faults of the old ship, the engine and the propeller. As one of the most important performance parameters of the marine main engine, the shaft power is generally obtained by indirectly measuring the torque and the rotating speed, and then the output power is compared with the oil consumption to avoid the excessive use of the engine, so that the speed of the ship can be kept or reasonably increased, a large amount of fuel oil can be saved, and the emission of carbon dioxide and nitrogen oxides can be reduced.
With respect to the measurement of the shaft power, the development trend is that the static test is developed to the dynamic test, the contact measurement is developed to the non-contact measurement, along with the deep technical research, the test system is also developed to the direction of volume miniaturization, display digitization, system intellectualization and monitoring real-time, and meanwhile, the requirements on the measurement precision, accuracy and resolution are continuously improved along with the market demand.
At present, torque sensors researched and developed at home and abroad are various, but mainly comprise strain type torque sensors and photoelectric type torque sensors. The strain type torque sensor is the most used torque sensor at home and abroad at present, and adopts the traditional method of sticking a strain gauge on the surface of a rotating shaft, and utilizes a proper circuit to obtain signals, and then carries out analysis processing; the photoelectric torque sensor mainly comprises a light source and a photoelectric element, when a transmission shaft is stressed, the photoelectric element converts light intensity change obtained by the light source into change of output pulse current, and torque measurement is realized through measurement of the change of the current.
Although the strain type torque sensor is simple and easy to operate, the caused error is large, certain error is caused by the patch operation, and the obtained result cannot accurately reflect the actual situation; for the shaft torque measuring system based on the photoelectric technology, the measurement accuracy depends on the accurate installation of the reading head to a certain extent, so the installation requirement is high when the shaft torque measuring system is used, an installer needs to have enough experience, the installation is difficult, and meanwhile, the performance of the shaft torque measuring system in terms of resolution and sensitivity cannot meet the actual use requirement gradually.
Disclosure of Invention
The present invention aims to solve the above technical problem at least to some extent. Therefore, the invention provides a shaft torque measuring system and a measuring method based on the Malus law, so as to solve the problems of low resolution, low sensitivity and high installation difficulty in the existing shaft torque measuring technology.
In order to achieve the purpose, the invention adopts the following technical scheme:
a kind of axle torque measurement system based on Malus' law, the black box is mounted on the axle to be measured detachably, form the airtight, opaque space in the box, as the measuring area, the measuring device in the said axle torque measurement system is set up in the measuring area, the structure of the said measuring device is set up as:
the device comprises a supporting platform detachably sleeved on a shaft to be measured through a first connecting lantern ring, a laser, a first light-transmitting element and a light intensity detection element, wherein the supporting platform is hung on the outer side of the shaft to be measured in a hanging mode, a laser, the first light-transmitting element and the light intensity detection element are arranged on the supporting platform from front to back at intervals along the axial direction of the shaft to be measured and in a radial direction of the shaft to be measured with a gap, and a second light-transmitting element is supported by a second connecting lantern ring detachably sleeved on the shaft to be measured, is hung on the outer side of the shaft to be measured and is located between the first light-transmitting element and the light intensity detection element along the axial direction;
the first light-transmitting element is close to the laser and is provided with a first polaroid; the second light-transmitting element is far away from the laser and is provided with a second polaroid; the planes of the first polaroid and the second polaroid are perpendicular to the axis of the shaft to be measured, the centers of the first polaroid and the second polaroid are arranged in a collinear manner, and the included angle between the initial polarization directions is 45 degrees; the radial gap between the part of the supporting platform provided with the light intensity detection module and the shaft to be detected is larger than the thickness of the second connecting lantern ring; the laser beam emitted by the laser is parallel to the axis of the shaft to be detected, can sequentially penetrate through the centers of the first polaroid and the second polaroid, and the light intensity data signal of the laser penetrating through the second polaroid is detected by the light intensity detection module;
the shaft torque measuring system further comprises a wireless transmission data module, an output module and a display module, wherein the output module and the display module are electrically connected with the processor, the light intensity data signals detected by the light intensity detection module are transmitted to the processor through the wireless transmission data module, the processor analyzes and processes the received light intensity data signals to obtain shaft torque data signals, and the display module receives and displays the shaft torque data signals through the output module.
The invention also has the structural characteristics that:
in the second light-transmitting element, an installation block is formed by extending the outer circular surface of the second connection sleeve ring along the radial direction, a counter bore is formed in the installation block, a through hole is formed in the center of the bottom of the counter bore, and the second polarizer is embedded in the counter bore in a matching mode.
And the radial gap between the bottoms of the first polaroid and the second polaroid and the axial wall of the shaft to be measured is 4-5 mm.
And a gap is reserved between the whole outer edge of the measuring device and the inner wall of the black box.
The black box comprises an upper box body and a lower box body, and is symmetrically sleeved on the upper side and the lower side of the shaft to be measured by taking the axis of the shaft to be measured as the center.
The laser is a small semiconductor laser, the light intensity detection module is BH1750fvi, and the wireless transmission data module is RF 2401.
The invention also provides a measuring method of the shaft torque measuring system based on the Malus law, which comprises the following steps:
1) installing a supporting platform provided with a laser, a first light-transmitting element and a light intensity detection module on a shaft to be detected through a first connecting lantern ring;
2) a second connecting lantern ring axially penetrates through a gap between the shaft to be measured and the end part of the supporting platform and is sleeved on the shaft to be measured, so that a second light-transmitting element is positioned between the first light-transmitting element and the light intensity detection module, and the position of the second light-transmitting element is adjusted until the second polaroid and the first polaroid are parallel and have collinear centers;
3) taking down the second polaroid, starting the laser under the condition that the measuring area is in a dark environment, starting a light intensity measuring program, detecting a first light intensity data signal passing through the center of the first polaroid by a light intensity detecting module, and transmitting the first light intensity data signal to the processor through a wireless transmission data module;
4) installing a second polaroid, starting the laser again under the condition that the measuring area is in a dark environment, starting a light intensity measuring program, detecting a second light intensity data signal passing through the second polaroid by a light intensity detection module, and transmitting the second light intensity data signal to the processor through a wireless transmission data module;
5) the position of the second light-transmitting element on the shaft to be measured is adjusted slightly one by one, the measurement is carried out according to the step 4) after each adjustment, until the light intensity of the second light intensity data signal received by the processor is half of the light intensity of the first light intensity data signal, the second connecting lantern ring is fastened on the shaft to be measured, and the axial distance between the second light-transmitting element and the first light-transmitting element at the mounting position on the shaft to be measured is measured through the distance meter;
6) the black box is installed on the shaft to be measured, after a sealed and lightproof environment is formed in the measuring area, the driving device is utilized to drive the shaft to be measured to rotate around the central axis, the laser is started, the light intensity detection module detects a second light intensity data signal in real time and transmits the second light intensity data signal to the processor through the wireless transmission data module, the processor analyzes and compares the received real-time second light intensity data signal with the first light intensity data signal, the shaft torque data signal of the shaft to be measured is obtained through processing, and the display module receives and displays the current shaft torque data signal through the output module.
Compared with the prior art, the invention has the beneficial effects that:
according to the invention, the supporting platform with the laser, the first light-transmitting element and the light intensity detection module, the second light-transmitting element and the black box are arranged on the surface of the shaft to be measured, so that the supporting platform, the second light-transmitting element and the black box rotate along with the shaft to be measured, the light intensity of the laser passing through the second light-transmitting element is detected by the light intensity detection module, the light intensity data is wirelessly transmitted to the processor, and then the processor processes the data to obtain the torque of the shaft to be measured. The shaft torque measuring system and the measuring method have strong innovativeness, are a brand new method, are simple to install, have high resolution and high measuring precision, can effectively monitor the shaft power of mechanical equipment in real time, further reasonably adjust the output power of the mechanical equipment while controlling the normal operation of the mechanical equipment so as to improve the working efficiency, and can be used for quickly diagnosing the fault of the mechanical equipment and improving the maintenance efficiency.
Drawings
FIG. 1 is a schematic structural diagram of a black box sleeved on a shaft to be measured;
FIG. 2 is a schematic view of the measuring device when mounted on a shaft to be measured;
fig. 3 is a schematic structural view of a mounting block for mounting a second polarizing plate;
fig. 4 is a flow chart of the measurement system of the present invention.
In the figure, 1 axis to be measured; 2, black box; 3, putting the box body on the box body; 4, discharging the box body; 5 a first connecting collar; 6 supporting the platform; 7, a laser; 8 a first light-transmitting element; 9 a light intensity detection module; 10 a second connecting collar; 11 a second light-transmitting element; 12, mounting a block; 13 counter bore; 14 through holes; 15 semi-circular collar.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments. 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.
Referring to fig. 1 to 4, in the shaft torque measuring system based on the malus law of the present embodiment, a black box 2 is detachably sleeved on a shaft 1 to be measured, a closed and opaque space is formed in the black box to serve as a measuring area for eliminating interference of natural light to the torque measuring system, a measuring device in the shaft torque measuring system is arranged in the measuring area, and the structure of the measuring device is as follows:
a supporting platform 6 detachably sleeved on the shaft 1 to be measured through a first connecting lantern ring 5 is suspended outside the shaft 1 to be measured, a laser 7, a first light-transmitting element 8 and a light intensity detection element are arranged on the supporting platform 6 from front to back at intervals along the axial direction of the shaft 1 to be measured and the radial direction of the shaft 1 to be measured with a gap, and a second light-transmitting element 11 is supported by a second connecting lantern ring 10 detachably sleeved on the shaft 1 to be measured, is suspended outside the shaft 1 to be measured and is positioned between the first light-transmitting element 8 and the light intensity detection element along the axial direction;
the first light-transmitting element 8 should be as close as possible to the laser 7 when mounted, and is provided with a first polarizer; the second light-transmitting element 11 should be mounted as far away from the laser 7 as possible and be equipped with a second polarizer; the planes of the first polaroid and the second polaroid are perpendicular to the axis of the shaft 1 to be measured, the centers of the first polaroid and the second polaroid are arranged in a collinear manner, and the included angle between the initial polarization directions is 45 degrees; the radial gap between the part of the supporting platform 6 provided with the light intensity detection module 9 and the shaft 1 to be detected is larger than the thickness of the second connecting lantern ring 10; the laser beam emitted by the laser 7 is parallel to the axis of the shaft 1 to be measured, and can sequentially penetrate through the centers of the first polarizer and the second polarizer, and then vertically irradiate a photosensitive element (such as an illumination diode) of the light intensity detection module 9, and the light intensity data signal of the laser penetrating through the second polarizer is detected by the light intensity detection module 9;
the shaft torque measuring system further comprises a wireless transmission data module, an output module and a display module, wherein the output module and the display module are electrically connected with the processor, light intensity data signals detected by the light intensity detection module 9 are transmitted to the processor through the wireless transmission data module, the processor analyzes and processes the received light intensity data signals according to programs, shaft torque data signals are obtained through calculation, the display module receives the light intensity data signals through the output module, and the display signals are converted into shaft torque quantities to be displayed. Therefore, the torque of the shaft 1 to be measured can be intuitively displayed according to the display signal.
In specific implementation, the corresponding structural arrangement also includes:
the first polaroid and the second polaroid are in circular sheet structures.
In the second light-transmitting element 11, an installation block 12 is formed on the outer circumferential surface of the second connection collar 10 in a radially extending manner, a counter bore 13 is formed in the installation block 12, a through hole 14 is formed in the center of the bottom of the counter bore 13, and the second polarizer is fittingly embedded in the counter bore 13. The counter bored hole 13 has an aperture 0.5mm larger than the diameter of the second polarizer, a hole depth 0.5mm more than the thickness of the second polarizer, and the through hole 14 has an aperture 1.5-2.5mm smaller than the diameter of the second polarizer, so that the second polarizer can be removed by applying a light force to the second polarizer at one side of the through hole 14.
The first light transmitting element 8 is provided with a first polarizing plate in an embedded manner in the same configuration as the second light transmitting element 11.
The radial gap between the bottoms of the first polaroid and the second polaroid and the axial wall of the shaft to be measured 1 is 4-5 mm. The inner diameters of the first connecting lantern ring 5 and the second connecting lantern ring 10 are slightly larger than the outer diameter of the shaft 1 to be measured, and the first connecting lantern ring and the second connecting lantern ring are respectively sleeved on the shaft 1 to be measured through a plurality of radial screws distributed at equal intervals along the circumferential direction. In this embodiment, the thickness of the two connecting collars and the support platform 6 in the shape of a long plate is set between 2.5mm and 3.5 mm.
Considering that when the shaft 1 to be measured rotates, unstable runout may occur due to the precision problem, especially under the condition that the diameter of the shaft 1 to be measured is large, friction may be generated between the supporting platform 6 and the black box 2 and between the second light-transmitting element 11 and the light intensity detection module 9, and the supporting platform 6, the black box 2, the second light-transmitting element 11, the light intensity detection module 9, and the like are damaged, therefore, in order to avoid accidental damage, when the measuring device is installed, a gap should be ensured to be left between the whole outer edge of the measuring device and the inner wall of the black box 2. Specifically, the gap between the outer edge of the supporting platform 6 and the inner wall of the black box 2 should be greater than 4.5mm (5 mm in this embodiment), and the distance between the second light-transmitting element 11 and the light intensity detecting module 9 should be between 2-3mm (2.5 mm in this embodiment).
The black box 2 comprises an upper box body 3 and a lower box body 4, and is symmetrically sleeved on the upper side and the lower side of the shaft 1 to be measured by taking the axis of the shaft 1 to be measured as the center. The upper box body 3 and the semicircular lantern rings 15 at two ends of the lower box body 4 are fixedly connected through screws to form a whole, and are fixedly arranged on the shaft to be measured 1 through screws respectively. The thickness of the semicircular lantern ring 15 is 3-4mm, and the inner diameter of the semicircular lantern ring is matched with the outer diameter of the shaft 1 to be measured.
The laser 7 is a small semiconductor laser 7 and can be fixed on the supporting platform 6 in a sticking way; the light intensity detection module 9 is BH1750fvi and can be fixed on the supporting platform 6 in a sticking way; the wireless transmission data module is RF 2401.
The installation of the shaft torque measuring system of the present embodiment may be performed as follows:
the shaft 1 to be measured is first inserted into the first coupling collar 5 and then fastened with radial screws. Then the second connection sleeve ring 10 is sleeved on the shaft 1 to be measured, the second connection sleeve ring 10 is rotated to enable the second light-transmitting element 11 to rotate to a position 180 degrees different from the position in the figure 2, then the second connection sleeve ring 10 is moved along the axial direction to enable the second connection sleeve ring 10 to penetrate through a gap between the end part of the supporting platform 6 and the shaft 1 to be measured and move to a position between the first light-transmitting element 8 and the light intensity detection module 9, then the second connection sleeve ring 10 is rotated to enable the second light-transmitting element 11 to reset to the position shown in the figure 2, and then the second light-transmitting element 11 is fastened on the shaft 1 to be measured by utilizing radial screws.
Then, under the condition of ensuring that the measurement area is in a dark environment, the second polarizer is removed, then the light intensity measuring program is started, and the first light intensity data signal which is detected by the light intensity detection module 9 and penetrates through the first polarizer at the moment is recorded. And then a second polaroid is installed and the position of the second light-transmitting element 11 is adjusted until the light intensity of the second light intensity data signal which penetrates through the second polaroid and is detected by the light intensity detection module 9 is half of the light intensity of the first light intensity data signal.
Fig. 1 shows a schematic structure of a nested black box 2. After the above operation is completed, the black box 2 can be installed.
To sum up, the embodiment of the present invention also provides a measurement method based on the above shaft torque measurement system, which is performed according to the following steps:
1) installing a supporting platform provided with a laser, a first light-transmitting element and a light intensity detection module on a shaft to be detected through a first connecting lantern ring;
2) a second connecting lantern ring axially penetrates through a gap between the shaft to be measured and the end part of the supporting platform and is sleeved on the shaft to be measured, so that a second light-transmitting element is positioned between the first light-transmitting element and the light intensity detection module, and the position of the second light-transmitting element is adjusted until the second polaroid and the first polaroid are parallel and have collinear centers;
3) taking down the second polaroid, starting the laser under the condition that the measuring area is in a dark environment, starting a light intensity measuring program, detecting a first light intensity data signal passing through the center of the first polaroid by a light intensity detecting module, and transmitting the first light intensity data signal to the processor through a wireless transmission data module;
4) installing a second polaroid, starting the laser again under the condition that the measuring area is in a dark environment, starting a light intensity measuring program, detecting a second light intensity data signal passing through the second polaroid by a light intensity detection module, and transmitting the second light intensity data signal to the processor through a wireless transmission data module;
5) the position of the second light-transmitting element on the shaft to be measured is adjusted slightly one by one, the measurement is carried out according to the step 4) after each adjustment, until the light intensity of the second light intensity data signal received by the processor is half of the light intensity of the first light intensity data signal, the second connecting lantern ring is fastened on the shaft to be measured, and the axial distance between the second light-transmitting element and the first light-transmitting element at the mounting position on the shaft to be measured is measured through the distance meter;
6) the black box is installed on the shaft to be measured, after a sealed and lightproof environment is formed in the measuring area, the driving device is utilized to drive the shaft to be measured to rotate around the central axis, the laser is started, the light intensity detection module detects a second light intensity data signal in real time and transmits the second light intensity data signal to the processor through the wireless transmission data module, the processor analyzes and compares the received real-time second light intensity data signal with the first light intensity data signal, the shaft torque data signal of the shaft to be measured is obtained through processing, and the display module receives and displays the current shaft torque data signal through the output module.
As described above, the processor continuously receives the light intensity data wirelessly transmitted by the light intensity detection module, writes the distance between two points on the shaft to be measured by the distance meter and the light intensity of the laser beam passing through the first polarizer into the running program, calculates the torque of the rotating shaft to be measured in real time, and displays the torque of the shaft to be measured through the display module.
In step 5), the range finder may adopt a laser range finder, an ultrasonic range finder or other range finders capable of realizing tight range finding.
In practical application, on the basis of the invention, the position angle of the shaft to be measured, and the position angle difference or the rotating speed between two points on the shaft to be measured, which correspond to the first light-transmitting element and the second light-transmitting element, can be further output, so that various measurement functions of the shaft torque measurement system are enriched and expanded.
The method for calculating the torque of the shaft to be measured by the processor is described in detail below, when the shaft to be measured rotates around the central axis, the maximum stress of the shaft to be measured is distributed on the surface of the shaft to be measured, and the stress expression is as follows:
in the formula:
mx is the torque on the cross section of the shaft 2 to be measured;
rho is the distance from any point to the circle center;
Ip-polar moment of inertia.
The expression of the stress and strain of the shaft 2 to be measured is:
τ＝G·r
in the formula:
g-shear modulus of elasticity, generally 80GPa for steel G,
in the formula:
mu-Poisson's ratio
When the shaft to be measured rotates along the axis direction, the strain is as follows:
in the formula:
i.e. when G is 80GPa,
or
In this embodiment, the following steps are performed
The intensity is I according to the Malus law by utilizing the Malus law0After passing through the polarizing plate, the intensity of transmitted light is:
I＝I0(cosα)2
in the formula:
I0illumination intensity of incident front linearly polarized light
I-illumination intensity of outgoing linearly polarized light
Angle between vibration direction of alpha-incident light and polarization direction of polarizing plate
In this embodiment, the laser emitted from the laser does not exhibit polarization, and when the light intensity is I0After the laser light of (1) passes through the polarizing plate of the first light transmitting element, the light intensity of the transmitted light becomes:
I1＝I0/2
in the formula:
I0illumination intensity of laser
I1Intensity of laser light transmitted through the first polarizer
The polarization direction of I is the same as the polarization direction of the first polarizer.
After the laser passes through the first polarizer, the laser emits to the second light-transmitting element, and as can be seen from the malus law, the intensity of the laser after passing through the second polarizer becomes:
I'＝I1(cosα)2＝I0(cosα)2/2
in the formula:
intensity of laser light transmitted through the second polarizing plate
Angle between the first and second polarizing plates
When the bearing to be tested is subjected to torque, the supporting platform and the first stageThe cross section of the two light-transmitting elements generates a relative torsion angle
(
Possibly negative), the angle between the first and second polarizer becomes:
the laser light intensity received by the second polaroid and the light intensity detection module is as follows:
in the range of 0-2 PI, from I1α, I is available
There are four:
in this embodiment, α ═ pi/4 is α < pi/4 in practical cases, so that:
substituting the above equation into the previous relation between torque and rotation angle includes:
Therefore, based on the calculation mode, the processor can process the received light intensity data to obtain the torque of the shaft to be measured. The accuracy of the measured torque is inversely proportional to the distance between two points on the shaft to be measured corresponding to the first light-transmitting element and the second light-transmitting element. The larger the distance setting, the higher the measurement accuracy of the present invention.
In summary, the invention derives the relationship between the relative torsion angle of the two sections of the shaft to be measured and the variation of the light intensity by using the Malus law, measures the light intensity by using the light intensity detection module, and calculates the torque by using the processor. Since the second light-transmitting element is firmly fastened to the shaft, the cross-sections of the second polarizer and the second connecting collar do not twist relative to each other. The supporting platform is also fastened on the shaft, and the first light-transmitting element and the supporting platform are relatively static, so that the section where the first polarizing film and the first connecting lantern ring of the supporting platform are located does not twist relatively, and after the shaft receives torque, the relative twisting angle of the first polarizing film and the second polarizing film is equal to the relative twisting angle of the section where the first connecting lantern ring is located and the section where the second connecting lantern ring is located. By comparing the illumination intensity before and after twisting, the relative twisting angle can be calculated, and further the torque value can be obtained.
While embodiments of the invention have been shown and described, it will be understood by those of ordinary skill in the art that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.
Claims (6)
1. A shaft torque measuring method based on the Malus law is characterized in that a shaft torque measuring system based on the Malus law is utilized, a black box is detachably sleeved on a shaft to be measured in the shaft torque measuring system, a closed and light-tight space is formed in the black box and is used as a measuring area, a measuring device in the shaft torque measuring system is arranged in the measuring area, and the structure of the measuring device is as follows:
the device comprises a supporting platform detachably sleeved on a shaft to be measured through a first connecting lantern ring, a laser, a first light-transmitting element and a light intensity detection element, wherein the supporting platform is hung on the outer side of the shaft to be measured in a hanging mode, a laser, the first light-transmitting element and the light intensity detection element are arranged on the supporting platform from front to back at intervals along the axial direction of the shaft to be measured and in a radial direction of the shaft to be measured with a gap, and a second light-transmitting element is supported by a second connecting lantern ring detachably sleeved on the shaft to be measured, is hung on the outer side of the shaft to be measured and is located between the first light-transmitting element and the light intensity detection element along the axial direction;
the first light-transmitting element is close to the laser and is provided with a first polaroid; the second light-transmitting element is far away from the laser and is provided with a second polaroid; the planes of the first polaroid and the second polaroid are perpendicular to the axis of the shaft to be measured, the centers of the first polaroid and the second polaroid are arranged in a collinear manner, and the included angle between the initial polarization directions is 45 degrees; the radial gap between the part of the supporting platform provided with the light intensity detection module and the shaft to be detected is larger than the thickness of the second connecting lantern ring; the laser beam emitted by the laser is parallel to the axis of the shaft to be detected, can sequentially penetrate through the centers of the first polaroid and the second polaroid, and the light intensity data signal of the laser penetrating through the second polaroid is detected by the light intensity detection module;
the shaft torque measuring system also comprises a wireless transmission data module, an output module and a display module, wherein the output module and the display module are electrically connected with the processor;
the shaft torque measuring method comprises the following steps:
1) installing a supporting platform provided with a laser, a first light-transmitting element and a light intensity detection module on a shaft to be detected through a first connecting lantern ring;
2) a second connecting lantern ring axially penetrates through a gap between the shaft to be measured and the end part of the supporting platform and is sleeved on the shaft to be measured, so that a second light-transmitting element is positioned between the first light-transmitting element and the light intensity detection module, and the position of the second light-transmitting element is adjusted until the second polaroid and the first polaroid are parallel and have collinear centers;
3) taking down the second polaroid, starting the laser under the condition that the measuring area is in a dark environment, starting a light intensity measuring program, detecting a first light intensity data signal passing through the center of the first polaroid by a light intensity detecting module, and transmitting the first light intensity data signal to the processor through a wireless transmission data module;
4) installing a second polaroid, starting the laser again under the condition that the measuring area is in a dark environment, starting a light intensity measuring program, detecting a second light intensity data signal passing through the second polaroid by a light intensity detection module, and transmitting the second light intensity data signal to the processor through a wireless transmission data module;
5) the position of the second light-transmitting element on the shaft to be measured is adjusted slightly one by one, the measurement is carried out according to the step 4) after each adjustment, until the light intensity of the second light intensity data signal received by the processor is half of the light intensity of the first light intensity data signal, the second connecting lantern ring is fastened on the shaft to be measured, and the axial distance between the second light-transmitting element and the first light-transmitting element at the mounting position on the shaft to be measured is measured through the distance meter;
6) the black box is installed on the shaft to be measured, after a sealed and lightproof environment is formed in the measuring area, the driving device is utilized to drive the shaft to be measured to rotate around the central axis, the laser is started, the light intensity detection module detects a second light intensity data signal in real time and transmits the second light intensity data signal to the processor through the wireless transmission data module, the processor analyzes and compares the received real-time second light intensity data signal with the first light intensity data signal, the shaft torque data signal of the shaft to be measured is obtained through processing, and the display module receives and displays the current shaft torque data signal through the output module.
2. A method of measuring shaft torque based on malus law as claimed in claim 1, wherein: in the second light-transmitting element, an installation block is formed by extending the outer circular surface of the second connection sleeve ring along the radial direction, a counter bore is formed in the installation block, a through hole is formed in the center of the bottom of the counter bore, and the second polarizer is embedded in the counter bore in a matching mode.
3. A method of measuring shaft torque based on malus law as claimed in claim 1, wherein: and the radial gap between the bottoms of the first polaroid and the second polaroid and the axial wall of the shaft to be measured is 4-5 mm.
4. A method of measuring shaft torque based on malus law as claimed in claim 1, wherein: and a gap is reserved between the whole outer edge of the measuring device and the inner wall of the black box.
5. A method of measuring shaft torque based on malus law as claimed in claim 1, wherein: the black box comprises an upper box body and a lower box body, and is symmetrically sleeved on the upper side and the lower side of the shaft to be measured by taking the axis of the shaft to be measured as the center.
6. A method of measuring shaft torque based on malus law as claimed in claim 1, wherein: the laser is a small semiconductor laser, the light intensity detection module is BH1750fvi, and the wireless transmission data module is RF 2401.
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