CN115452214B - Harmonic reducer flexspline stress-strain measurement device and method - Google Patents
Harmonic reducer flexspline stress-strain measurement device and method Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/24—Measuring force or stress, in general by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis using infrared, visible light, ultraviolet
- G01L1/242—Measuring force or stress, in general by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis using infrared, visible light, ultraviolet the material being an optical fibre
- G01L1/246—Measuring force or stress, in general by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis using infrared, visible light, ultraviolet the material being an optical fibre using integrated gratings, e.g. Bragg gratings
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/16—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge
- G01B11/165—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge by means of a grating deformed by the object
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Abstract
The invention discloses a device and a method for measuring stress and strain of a flexible gear of a harmonic reducer, wherein the device comprises an optical fiber Bragg grating sensor (FBG) which is arranged with the flexible gear of the harmonic reducer, a driving mechanism and a loading mechanism which are used for driving the harmonic reducer, and a measurement control system which is used for acquiring signals acquired by the optical fiber Bragg grating sensor and carrying out stress and strain measurement calculation, wherein a hollow design of an output shaft of the harmonic reducer is utilized for leading out a signal wire of the sensor on the rotating flexible gear, and finally, the measurement of the stress and strain of the flexible gear of the harmonic reducer under a dynamic working condition is realized through a slip ring. The method can measure the stress strain performance of the flexible gear of the harmonic reducer under different working conditions, provides effective load basis and parameter guidance for monitoring the internal meshing state of the harmonic reducer and optimizing structural parameters, and has important significance for intelligent operation of the harmonic reducer and optimization of the flexible gear.
Description
Technical Field
The invention relates to the field of harmonic reducer measurement systems, in particular to a device and a method for measuring stress and strain of a flexible gear of a harmonic reducer.
Background
The harmonic reducer is a gear transmission mechanism which can enable a flexible gear to generate controllable elastic deformation by means of a wave generator and can conduct movement and power transmission through small tooth difference meshing of the flexible gear and a rigid gear, has the characteristics of high precision, large transmission ratio, small return difference and the like, and is widely applied to the fields of robots, aerospace, precision machine tools, medical appliances and the like. The flexible gear is used as the most critical part in the harmonic reducer, and the large deformation of the bonding wave generator is the basis for realizing the transmission of the harmonic reducer. As a thin-wall shell structure, the flexible gear is subjected to double functions of a wave generator and external loading in the working process, and is subjected to bending stress and torsional stress in a cyclic elastic deformation state, and the deformation quantity of the flexible gear directly influences the motion track of the flexible gear, the meshing contact of the flexible gear and the rigid gear and the transmission precision of the speed reducer. In addition, the flexible gear can bear periodic alternating stress for a long time in the working process, so that the service life of the flexible gear is also a key factor for limiting the service life of the harmonic reducer.
For a long time, the stress and strain research of the harmonic reducer flexspline is mostly based on numerical calculation and finite element simulation analysis, and an effective measuring device and method are lacked. The existing method for measuring the stress and strain of the flexible gear can be divided into a cyclic test method of a single flexible gear part and a measurement scheme of a complete machine of the harmonic reducer. The first method is to design a specific experimental device aiming at a single flexible gear part to simulate the action of a wave generator on the flexible gear, and then to measure the stress strain state of the flexible gear through a sensor. For example, chinese patent application number CN 202022335562.5: a flexible wheel performance testing device for a harmonic reducer. The device simulates the driving of a wave generator and a motor through a cam lever mechanism, and can perform angle test, deformation test, cyclic stress test and fatigue life test of a single part of the flexible gear under different working conditions. For another example, chinese patent No. CN 202010789069.2: a harmonic drive flexible wheel radial deformation reconfigurable measuring device. The measuring device realizes the measurement of the deformation of the flexible gear through a feedback system formed by the high-precision turntable system, the torque motor and the circular grating, the simulated contact fit of the wave generator and the flexible bearing and the measuring system of the laser range finder. In addition, the invention can realize the measurement of the deformation of different flexible gears under the action of different types of wave generators by replacing the connecting flange and the transmission shaft, and has the characteristics of convenient installation, high measurement precision and the like. However, the two devices are basically part-level flexible gear performance testing methods, and cannot consider the boundary conditions of the flexible gear in the assembly state of the harmonic speed reducer, the boundary effect of a gear contact area, the stress distribution of the rigid gear on the flexible gear cylinder body and the contact state of actual meshing teeth. Therefore, the method cannot truly reflect the stress-strain performance of the flexible gear in the working state.
The second method is to measure the performance of the flexspline in the whole state of the harmonic reducer. For example, chinese patent application number CN 202110755675.7: a device and a method for measuring radial deformation of gear teeth of a flexible gear of a harmonic reducer. The device is characterized in that observation openings are formed in the rigid gear of the harmonic reducer by processing, and radial deformation of gear teeth of the flexible gear at different positions of meshing motion of the harmonic reducer is respectively measured along the central axis direction of the reducer by utilizing a laser displacement sensor. The device can realize the gear tooth deformation measurement of the harmonic reducer flexible gear in the working state, but is limited by the measurement principle of the laser displacement sensor, the measurement of the stress strain of the flexible gear cylinder which is more concerned cannot be realized, and the original structure of the harmonic reducer needs to be destroyed in the measurement process by the method of the patent, so that the nondestructive measurement of the parts of the harmonic reducer cannot be realized.
Therefore, it is particularly important to develop a measuring device and a measuring method capable of carrying out measurement simulation of stress strain of a harmonic reducer flexspline under multiple working conditions without damaging the structure of the reducer.
Disclosure of Invention
The invention aims to provide a device and a method for measuring stress and strain of a flexible gear of a harmonic reducer, which are used for solving the problem that the stress and strain are difficult to measure when the flexible gear of the harmonic reducer rotates in the prior art.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
A harmonic reducer flexspline stress-strain measurement device comprises a driving mechanism, a loading mechanism, a measurement assembly and a measurement control system; the driving mechanism is connected with an input shaft of the harmonic reducer, and the driving mechanism provides power on the input side of the harmonic reducer; the loading mechanism is connected with an output shaft of the harmonic reducer, and the loading mechanism provides power on the output side of the harmonic reducer; the measuring assembly comprises a plurality of fiber Bragg grating sensors, wherein the fiber Bragg grating sensors are fixed on the inner surface of a flexible wheel in the harmonic reducer, and each fiber Bragg grating sensor senses stress strain when the flexible wheel rotates and generates an electric signal; the measuring control system is respectively and electrically connected with the driving mechanism and the loading mechanism in a control way, each fiber Bragg grating sensor is respectively and electrically connected with the measuring control system in a signal transmission way, and the measuring control system obtains the stress strain quantity of the flexible wheel based on signals acquired by the fiber Bragg grating sensors.
Further, the driving mechanism comprises a driving motor and a first shaft transmission mechanism, a motor shaft of the driving motor is connected with an input shaft of the harmonic reducer through the first shaft transmission mechanism, and the measurement control system is electrically connected with the driving motor in a control manner.
Further, a first rotating speed and torque sensor is arranged on the first shaft transmission mechanism, the first rotating speed and torque sensor is electrically connected with the signal transmission of the measurement control system, and the first rotating speed and torque sensor senses the rotating speed and torque of the input side of the harmonic reducer and generates an electric signal to be transmitted to the measurement control system.
Further, the loading mechanism comprises a loading motor, a second shaft transmission mechanism, a belt wheel transmission mechanism and a third shaft transmission mechanism, wherein a motor shaft third shaft transmission mechanism of the loading motor is connected with a belt wheel driving wheel in the belt wheel transmission mechanism, and a belt wheel driven wheel in the belt wheel transmission mechanism is connected with an output shaft of the harmonic reducer through the second shaft transmission mechanism.
Further, the second shaft transmission mechanism comprises a hollow shaft, the hollow shaft is provided with a slip ring, the slip ring comprises a slip ring rotating end and a slip ring fixed end, the slip ring rotating end and the slip ring fixed end are in relative rotation fit and keep electrical contact, and the slip ring rotating end is fixed on the hollow shaft to rotate along with the hollow shaft; the data wires of the fiber Bragg grating sensors respectively penetrate into the hollow shaft from the hollow output shaft of the harmonic reducer, then penetrate out of the hollow shaft and are collected and electrically connected to the slip ring rotating end; the slip ring fixed end does not rotate along with the hollow shaft, and is electrically connected with the signal transmission of the measurement control system.
Further, a second rotating speed and torque sensor is arranged on the second shaft transmission mechanism, the second rotating speed and torque sensor is electrically connected with the signal transmission of the measurement control system, and the second rotating speed and torque sensor senses the rotating speed and torque of the output side of the harmonic speed reducer and generates an electric signal to be transmitted to the measurement control system.
Further, the measurement control system comprises an industrial personal computer, a computer and a fiber bragg grating demodulator, wherein the computer is electrically connected with the industrial personal computer through data transmission, the industrial personal computer is respectively and electrically connected with the driving mechanism and the loading mechanism, each fiber bragg grating sensor is respectively and electrically connected with the fiber bragg grating demodulator through signal transmission, and the fiber bragg grating demodulator is electrically connected with the computer through data transmission.
A method for measuring stress and strain of a flexible gear of a harmonic reducer comprises the following steps:
step 1, enabling a driving mechanism to drive a harmonic reducer to rotate, and acquiring acquired data of each fiber Bragg grating sensor in a flexible gear of the harmonic reducer by a control system during rotation;
step2, obtaining strain data of the flexible gear cylinder based on a temperature-strain demodulation algorithm by utilizing grating pitch change of the fiber Bragg grating sensor; the fiber Bragg grating sensor has the following formula for temperature and strain change relation:
ΔλB＝(KεΔε+KTΔT)，
wherein Deltaλ B is the grid distance variation, K ε is the strain sensitivity coefficient of the fiber Bragg grating sensor, K T is the temperature sensitivity coefficient of the fiber Bragg grating sensor, deltaε is the flexible wheel cylinder strain variation, deltaT is the temperature variation;
and 3, under the same temperature field, the strain change of the plurality of fiber Bragg grating sensors can be obtained by solving the following formula:
wherein Δλ Bk (is the change in the pitch of the kth fiber bragg grating sensor, K εk is the strain sensitivity coefficient of the kth fiber bragg grating sensor, K Tk is the temperature sensitivity coefficient of the kth fiber bragg grating sensor, Δε k (is the change in the strain of the kth fiber bragg grating sensor, Δt is the change in temperature, k=1, 2,3 … … n;
and 4, when the fiber Bragg grating sensor is stuck on the inner side of the flexible gear cylinder, the strain of the fiber Bragg grating sensor at the measuring position is the same as the strain of the flexible gear cylinder, namely delta epsilon c＝Δεk (the strain data of the flexible gear cylinder obtained by the steps can be used for calculating the stress value of the flexible gear cylinder based on the stress-strain equation of the following formula:
σc＝Ec·Δεc，
Wherein: sigma c is the stress of the flexible gear cylinder, E c is the elastic modulus of the flexible gear cylinder, and delta epsilon c is the strain of the flexible gear cylinder.
The invention provides a device and a method for measuring the stress and strain of a flexible gear of a harmonic reducer, which can realize the measurement of the stress and strain distribution characteristics, performance detection and fatigue life of the flexible gear of the harmonic reducer in a working state.
According to the invention, the fiber Bragg grating sensor is arranged on the harmonic reducer flexible wheel, the signal line of the sensor on the rotary flexible wheel is led out by utilizing the hollow design of the output shaft of the harmonic reducer, and finally the measurement of the stress strain of the harmonic reducer flexible wheel under the dynamic working condition is realized through the slip ring. The method can measure the stress strain of the flexible gear of the harmonic reducer under different working conditions, provides effective load basis and guiding parameters for monitoring the internal meshing state of the harmonic reducer and optimizing structural parameters, and has important significance for optimizing the flexible gear of the harmonic reducer.
The invention has the following differences with the prior art:
1. According to the measuring device and the measuring method, an internal measuring technology is adopted, an additional flexible gear deformation generating device is avoided, the stress and strain measurement of the flexible gear in a working state can be realized, and the measuring device and the measuring method have a simpler mechanical structure.
2. When the method is used for measuring the stress and strain of the harmonic reducer flexible gear, the structure of the harmonic reducer is not damaged, the constraint condition of the flexible gear and the meshing condition of gear teeth are not changed, the real working state of the harmonic reducer flexible gear can be ensured to the greatest extent, and better economy is achieved.
3. According to the invention, through the design of hollow shafts with different sizes, the harmonic speed reducers with different types can be replaced, so that the measurement of the stress strain of the flexible gear of the harmonic speed reducers with different sizes and types is realized, and the applicability is wider.
Drawings
Fig. 1 is a schematic view of an apparatus according to an embodiment of the present invention.
Fig. 2 is a schematic diagram of a strain testing structure of a flexible gear of a harmonic reducer according to an embodiment of the invention.
Fig. 3 is a schematic diagram of an installation of a harmonic reducer flexspline fiber bragg grating sensor in an embodiment of the present invention.
FIG. 4 is a schematic diagram of a torque sensor installation in accordance with an embodiment of the present invention.
Fig. 5 is a schematic diagram of the installation of a harmonic reducer according to an embodiment of the invention.
FIG. 6 is a schematic view of a slip ring installation in an embodiment of the present invention.
Fig. 7 is a flowchart of a method for measuring stress and strain of a flexspline of a harmonic reducer according to an embodiment of the present invention.
The reference numerals in fig. 1 indicate: the device comprises a base, a 2-driving motor, a 3-coupling, a 4-rotating speed torque sensor, a 5-transmission shaft, a 6-coupling, a 7-speed reducer input shaft, an 8-harmonic speed reducer, a 9-speed reducer output shaft, a 10-coupling, a 11-rotating speed torque sensor, a 12-hollow shaft, a 13-coupling, a 14-hollow shaft, a 15-belt, a 16-belt wheel driven wheel, a 17-slip ring, a 18-belt wheel driving wheel, a 19-transmission shaft, a 20-coupling, a 21-loading motor and a 22-signal wire.
The reference numerals in fig. 2 indicate: 2001-box, 2002-rigid wheel, 2003-wave generator, 2004-bearing, 2005-flexible wheel, 2006-roller bearing outer ring, 2007-inner hexagonal screw, 2008-fiber Bragg grating sensor, 2009-data wire, 9-output shaft, 2011-gasket, 2012-oil seal, 2013-cover plate, 12-hollow shaft one, 14-hollow shaft two, 17-slip ring.
The reference numerals in fig. 3 indicate: 2005-flexspline, 2008-fiber bragg grating.
The reference numerals in fig. 4 indicate: 4-rotating speed torque sensor, 4001-flange plate, 4002-fixing bolt, 4003-sensor base and 4004-fixing bolt.
The reference numerals in fig. 5 indicate: 8-harmonic speed reducer, 8001-harmonic speed reducer bracket, 8002-fixing bolt.
The reference numerals in fig. 6 indicate: 14-hollow shaft 1401-signal wire preformed hole, 1402-set screw, 1403-slip ring rotating end, 1404-slip ring rotating end lead terminal, 1405-slip ring fixed end, 1406-slip ring fixed end lead terminal.
Detailed Description
The invention will be further described with reference to the drawings and examples.
Referring to fig. 1, the device for measuring stress and strain of a flexible gear of a harmonic reducer according to this embodiment is composed of a base module, a driving mechanism, a loading mechanism, a transmission mechanism and a measurement control system. The base module comprises a base 1, and the base 1 can be fixed on a foundation by foundation bolts or fixed on other stable platforms by bolts. The base module functions to provide a fixed base for the drive mechanism, loading mechanism, transmission mechanism and measurement control system and to ensure a specific assembly relationship.
The driving mechanism comprises a driving motor 2, a first coupling 3, a first transmission shaft 5 and a second coupling 6. The driving motor 2 is fixed on the base 1 through bolts, and the driving motor and the loading motor 21 are used for providing constant rotating speed and torque for the experimental device of the harmonic reducer 8. The motor shaft of the driving motor 2 is connected with one end of a first transmission shaft 5 through a first coupling 3, the other end of the first transmission shaft 5 is connected with an input shaft 7 of a harmonic reducer 8 through a second coupling 6, and a first shaft transmission mechanism is formed by the first coupling 3, the first transmission shaft 5 and the second coupling 6. The drive motor 2 thereby outputs power to the input side of the harmonic reducer through the first shaft transmission mechanism.
The loading mechanism comprises a loading motor 21, a coupling III 10, a hollow shaft I12, a coupling IV 13, a hollow shaft II 14, a belt 15, a belt wheel driven wheel 16, a belt wheel driving wheel 18, a transmission shaft II 19 and a coupling V20. The output shaft 9 of the harmonic reducer 8 is connected with one end of a hollow shaft I12 through a coupling III 10, the other end of the hollow shaft I12 is connected with one end of a hollow shaft II 14 through a coupling IV 13, and a second shaft transmission mechanism is formed by the coupling III 10, the hollow shaft I12, the coupling IV 13 and the hollow shaft II 14. An output shaft of the loading motor 21 is connected with one end of a transmission shaft II 19 through a coupling V20, and a third shaft transmission mechanism is formed by the coupling V20 and the transmission shaft II 19. The belt wheel driving wheel 18 is coaxially fixed on the transmission shaft II 19, the belt wheel driven wheel 16 is coaxially fixed on the hollow shaft II 14, the belt wheel driving wheel 18 and the belt wheel driven wheel 16 are in transmission connection through the belt 15, and a belt wheel transmission mechanism is formed by the belt wheel driving wheel 18, the belt wheel driven wheel 16 and the belt 15. The loading motor 21 thus outputs power to the output side of the harmonic reducer 8 through the third shaft transmission mechanism, the pulley transmission mechanism, and the second shaft transmission mechanism.
In the second shaft transmission mechanism, a second hollow shaft 14 in the second shaft transmission mechanism is provided with a slip ring 17, and specifically as shown in fig. 6, the slip ring 17 comprises a slip ring rotating end 1804 and a slip ring fixing end 1806, the slip ring rotating end 1804 and the slip ring fixing end 1806 are relatively in rotating fit and keep in electrical contact, and the slip ring rotating end 1804 is coaxially fixed on the second hollow shaft 14 and rotates along with the second hollow shaft 14.
The loading mechanism is used for providing constant rotating speed and torque for the harmonic reducer experimental device together with the driving mechanism. In the installation process, the loading motor 21 is coaxially installed with the fifth coupler 20, the second transmission shaft 19 and the driving wheel 18. In addition, during installation, the center-to-center distance between the pulley drive pulley 18 and the pulley driven pulley 16 may be fine-tuned to ensure belt drive synchronicity, taking into account the elasticity of the belt.
In order to ensure coaxiality among the shafts, a fixed base can be arranged at the bottom of a part with smaller axle center height according to the axle center heights of different parts in the assembly process. The function of the pulley follower 16 and the pulley follower 18 is to eliminate the influence of motor vibration to some extent, and to measure the installation of the slip ring 17 in the control system and the extraction of the signal line inside the decelerator.
In this embodiment, a first rotational speed and torque sensor 4 is coaxially installed on the first transmission shaft 5, and a second rotational speed and torque sensor 11 is coaxially installed on the first hollow shaft, wherein the first rotational speed and torque sensor 4 senses rotational speed and torque on the input side of the harmonic reducer 8, and the second rotational speed and torque sensor 11 senses rotational speed and torque data on the output side of the harmonic reducer 8. The first rotating speed torque sensor 4 and the second rotating speed torque sensor 11 are respectively and electrically connected with the measurement control system so as to transmit the generated signals to the measurement control system. In order to ensure the coaxiality of each shaft in the transmission system, sensor mounting bases are respectively designed at the bottoms of the first rotating speed torque sensor 4 and the second rotating speed torque sensor 11, the lower ends of the bases are fixed on the base through bolts, and the upper ends of the bases are connected with the torque rotating speed sensor through bolts.
As shown in fig. 2 and 3, in the present embodiment, first, a rigid gear 2002, a wave generator 2003, and a bearing 2004 are assembled to a housing 2001, and a plurality of fiber bragg grating sensors 2008 are mounted inside a cylinder of a flexspline 2005 of a harmonic reducer, and the plurality of fiber bragg grating sensors 2008 are uniformly distributed circumferentially around a central axis of the flexspline 2005. During the installation process, because the fiber bragg grating sensor 2008 is very slim, care should be taken to achieve a high sensor survival rate and to adequately sense the strain of the monitored object. The signal lead terminal of the fiber bragg grating sensor 2008 is fixed on the flexible wheel 2005, and the signal wire 2009 of the fiber bragg grating sensor 2008 is led out to the slip ring rotating end 1403 at the shaft end through the hollow shaft 12 and the hollow shaft 17 by the hollow shaft 9 at the output end of the harmonic reducer 8. The roller bearing outer race 2006, washer 2011, oil seal 2012 and cover plate 2013 are assembled to the case 2001 using socket head cap screws 2007 at the right end of the harmonic reducer.
In the process of installing the fiber bragg grating sensor 2008 on the inner side of the flexible gear 2005 of the harmonic reducer, because the grating is very fine, the fiber bragg grating sensor should be carefully arranged so as to achieve a higher sensor survival rate and fully sense the strain condition of the monitored object. The arrangement process is as follows: the inner surface of the cylinder of the flexspline 2005 is first polished and cleaned using sandpaper and alcohol. The adhesive is smeared on an iron sheet of the fiber Bragg grating sensor 2008, and then the sensor is pressed on the surface of an object for a period of time, so that the adhesive strength is ensured, and the sensor is stuck at a position where the point is required to be distributed. Further, the lead wire of the fiber Bragg grating sensor 2008 is led out from the hollow shaft.
In this embodiment, the measurement control system includes an industrial personal computer, a computer, and a fiber bragg grating demodulator, where the industrial personal computer and the computer are in data communication connection, the industrial personal computer is respectively and electrically connected with the driving motor 2 and the loading motor 21, and the first rotational speed torque sensor 4 and the second rotational speed torque sensor 11 are respectively and electrically connected with the industrial personal computer in signal transmission. The input of the fiber grating demodulator is electrically connected with the slip ring fixed end 1806 of the slip ring 17 through the signal line 22 in a signal transmission way, and the output of the fiber grating demodulator is electrically connected with the data transmission of a computer, so that the computer can acquire the data acquired by each fiber Bragg grating sensor 2008 through the fiber grating demodulator and the slip ring 17.
Referring to fig. 4, in this embodiment, a rotational speed and torque sensor 4 is taken as an example, the rotational speed and torque sensor 4 is fixed on a sensor base 4003 by a fixing bolt 4002, the sensor base 4003 is fixed on a base 1 by the fixing bolt 4004 to ensure coaxiality of each shaft, and a transmission shaft (i.e., a transmission shaft one 5) can be connected to the rotational speed and torque sensor 4 through a flange 4001 to realize measurement of rotational speed and torque of the shafts.
Referring to fig. 5, the harmonic reducer 8 is fixed to the harmonic reducer bracket 8001 by bolts 8002, and bolt holes are provided in the bottom of the harmonic reducer bracket 8001, which can be used for fixing the harmonic reducer bracket 8001 to the base 1.
Referring to fig. 6, the flexspline 2005 is always rotated during operation of the harmonic reducer 8, and a slip ring is mounted at the end of the hollow shaft 14 for the extraction of the signal line of the rotating member, wherein the hollow shaft 14 is fixedly connected to the slip ring rotating end 1803 by a fixing screw 1802. The sensor signal wire in the hollow shaft II 14 is led out through a signal wire reserved hole 1401 of the hollow shaft II 14 and is connected to a lead terminal 1404 of a rotating end of the slip ring, and further, at a fixed end 1405 of the slip ring, the signal wire connected into the fiber bragg grating demodulator can be connected with a lead terminal 1406 of the fixed end of the slip ring so as to realize signal transmission.
As shown in fig. 7, the power supply is required to be disconnected in the assembly and installation stage of the harmonic reducer flexspline stress-strain measuring device, and the specific using method comprises the following steps:
(1) The base 1 is fixed to a stable foundation or platform. The driving motor 2, the torque rotation speed sensor I4, the harmonic speed reducer 8, the rotation speed torque sensor II 11 and the belt pulley driven wheel 6 are fixedly arranged on the base 1 through bolts, the input ends of the driving motor 2 and the harmonic speed reducer 8 are sequentially connected through the coupler 3, the transmission shaft 5 and the coupler 6, the output end of the harmonic speed reducer and the belt pulley driven wheel 16 are sequentially connected through the coupler 11, the hollow shaft 13, the coupler 14 and the hollow shaft 15 from left to right, and the output shaft, the transmission shaft, the hollow shaft and the speed reducer shaft of the driving motor are required to be guaranteed to be in the same axle center in the installation process.
(2) The axes of the belt wheel driving wheel 18 and the belt wheel driven wheel 16 are arranged in parallel, and the center distance between the belt wheel driving wheel 18 and the belt wheel driven wheel 16 is adjusted, so that the belt 15 does not slip or excessively tension. The belt pulley driving wheel 18 and the loading motor 21 are arranged on the base, so that the axes of the belt pulley driving wheel 18, the transmission shaft 19, the coupler 20 and the loading motor output shaft 21 are on the same central line.
(3) In the harmonic reducer 8, the fiber bragg grating sensor 2008 is installed inside the flexspline 2005, and during the installation process, because the grating is very fine, the fiber bragg grating should be carefully arranged so as to achieve a higher sensor survival rate and fully sense the strain condition of the monitored object. The arrangement process is as follows: the inner surface of the flexspline cup was first polished and cleaned using sandpaper and alcohol. The adhesive is smeared on an iron sheet of the optical fiber sensor, and then the sensor is pressed on the surface of an object for a period of time, so that the adhesive strength is ensured, and the optical fiber sensor is adhered to a position where a point is required to be distributed.
(4) The sensor signal lead terminal is fixed on the flexible gear 2005, and signals are transmitted to the hollow output shaft 12 of the harmonic reducer and the shaft end of the hollow shaft 14. Further, a slip ring is mounted on the end of the hollow shaft 14, wherein the hollow shaft 14 is connected to a slip ring rotating end 1403 by a set screw 1402. The sensor signal wire in the hollow shaft is led out through a signal wire reserved hole 1401 of the hollow shaft and is connected to a lead terminal 1404 of the rotating end of the slip ring.
(5) The fixed end lead terminal 1406 of the slip ring is connected with a signal wire, and the other end of the signal wire is connected with a fiber bragg grating demodulator. Further, the optical fiber demodulator is connected into a data acquisition system.
(6) The power supply system is used for supplying electric energy to the industrial personal computer, the driving motor, the loading motor, the rotating speed torque sensor, the fiber bragg grating demodulator, the industrial computer and the notebook computer;
(7) Starting the fiber grating monitoring system, and implementing the following steps: and accessing the sensors into corresponding channels according to requirements, and realizing the transmission of parameter signals through optical cables. And the signals entering the demodulator are analyzed, demodulated and stored in real time, and finally the demodulated signals are output to a screen end to directly reflect the measured position real-time stress strain signals.
(8) And starting the industrial personal computer and the industrial computer to control the rotating speed and the torque of the driving motor and the loading motor so as to realize the stress and strain measurement of the flexible gear under different working conditions.
The harmonic reducer flexspline stress-strain measurement method based on the stress-strain measurement device comprises the following steps:
step 1, enabling a driving mechanism to drive a harmonic reducer to rotate, and acquiring acquired data of each fiber Bragg grating sensor in a flexible gear of the harmonic reducer by a control system during rotation;
step2, obtaining strain data of the flexible gear cylinder based on a temperature-strain demodulation algorithm by utilizing grating pitch change of the fiber Bragg grating sensor; the fiber Bragg grating sensor has the following formula for temperature and strain change relation:
ΔλB＝(KεΔε+KTΔT)，
wherein Deltaλ B is the grid distance variation, K ε is the strain sensitivity coefficient of the fiber Bragg grating sensor, K T is the temperature sensitivity coefficient of the fiber Bragg grating sensor, deltaε is the flexible wheel cylinder strain variation, deltaT is the temperature variation;
and 3, under the same temperature field, the strain change of the plurality of fiber Bragg grating sensors can be obtained by solving the following formula:
wherein Δλ Bk (is the change in the pitch of the kth fiber bragg grating sensor, K εk is the strain sensitivity coefficient of the kth fiber bragg grating sensor, K Tk is the temperature sensitivity coefficient of the kth fiber bragg grating sensor, Δε k (is the change in the strain of the kth fiber bragg grating sensor, Δt is the change in temperature, k=1, 2,3 … … n;
and 4, when the fiber Bragg grating sensor is stuck on the inner side of the flexible gear cylinder, the strain of the fiber Bragg grating sensor at the measuring position is the same as the strain of the flexible gear cylinder, namely delta epsilon c＝Δεk (the strain data of the flexible gear cylinder obtained by the steps can be used for calculating the stress value of the flexible gear cylinder based on the stress-strain equation of the following formula:
σc＝Ec·Δεc，
Wherein: sigma c is the stress of the flexible gear cylinder, E c is the elastic modulus of the flexible gear cylinder, and delta epsilon c is the strain of the flexible gear cylinder.
The embodiments of the present invention are merely described in terms of preferred embodiments of the present invention, and are not intended to limit the spirit and scope of the present invention, and various modifications and improvements made by those skilled in the art to the technical solutions of the present invention should fall within the protection scope of the present invention, and the technical content of the present invention as claimed is fully described in the claims.
Claims (8)
1. The device for measuring the stress and strain of the flexible gear of the harmonic reducer is characterized by comprising a driving mechanism, a loading mechanism, a measuring assembly and a measuring control system; the driving mechanism is connected with an input shaft of the harmonic reducer, and the driving mechanism provides power on the input side of the harmonic reducer; the loading mechanism is connected with an output shaft of the harmonic reducer, and the loading mechanism provides power on the output side of the harmonic reducer; the measuring assembly comprises a plurality of fiber Bragg grating sensors, wherein the fiber Bragg grating sensors are fixed on the inner surface of a flexible wheel in the harmonic reducer, and each fiber Bragg grating sensor senses stress strain when the flexible wheel rotates and generates an electric signal; the measurement control system is respectively and electrically connected with the driving mechanism and the loading mechanism in a control way, each fiber Bragg grating sensor is respectively and electrically connected with the measurement control system in a signal transmission way, and the measurement control system obtains the stress strain quantity of the flexible wheel based on the signals acquired by the fiber Bragg grating sensors;
obtaining strain data of the flexible gear cylinder based on a temperature-strain demodulation algorithm by utilizing grating pitch change of the fiber Bragg grating sensor; the fiber Bragg grating sensor has the following formula for temperature and strain change relation:
，
wherein the method comprises the steps of In order to be the amount of change in the pitch of the grid,Is the strain sensitivity coefficient of the fiber Bragg grating sensor,Is the temperature sensitivity coefficient of the fiber Bragg grating sensor,For the strain variation of the flexible gear cylinder,Is the temperature variation.
2. The device for measuring stress and strain of the harmonic reducer flexible gear according to claim 1, wherein the driving mechanism comprises a driving motor and a first shaft transmission mechanism, a motor shaft of the driving motor is connected with an input shaft of the harmonic reducer through the first shaft transmission mechanism, and the measurement control system is electrically connected with the driving motor in a control manner.
3. The device for measuring the stress and strain of the flexible gear of the harmonic reducer according to claim 2, wherein the first shaft transmission mechanism is provided with a first rotating speed and torque sensor, the first rotating speed and torque sensor is electrically connected with a measurement control system in a signal transmission manner, and the first rotating speed and torque sensor senses the rotating speed and torque of the input side of the harmonic reducer and generates an electric signal to be transmitted to the measurement control system.
4. The device for measuring stress and strain of a flexible gear of a harmonic reducer according to claim 1, wherein the loading mechanism comprises a loading motor, a second shaft transmission mechanism, a belt wheel transmission mechanism and a third shaft transmission mechanism, a motor shaft third shaft transmission mechanism of the loading motor is connected with a belt wheel driving wheel in the belt wheel transmission mechanism, and a belt wheel driven wheel in the belt wheel transmission mechanism is connected with an output shaft of the harmonic reducer through the second shaft transmission mechanism.
5. The device for measuring stress-strain of flexible gear of harmonic reducer according to claim 4, wherein the second shaft transmission mechanism comprises a hollow shaft, the hollow shaft is equipped with a slip ring, the slip ring comprises a slip ring rotating end and a slip ring fixed end, the slip ring rotating end and the slip ring fixed end are relatively in rotating fit and keep electrical contact, wherein the slip ring rotating end is fixed on the hollow shaft to rotate along with the hollow shaft; the data wires of the fiber Bragg grating sensors respectively penetrate into the hollow shaft from the hollow output shaft of the harmonic reducer, then penetrate out of the hollow shaft and are collected and electrically connected to the slip ring rotating end; the slip ring fixed end does not rotate along with the hollow shaft, and is electrically connected with the signal transmission of the measurement control system.
6. The device for measuring stress and strain of the flexible gear of the harmonic reducer according to claim 4, wherein the second shaft transmission mechanism is provided with a second rotating speed and torque sensor, the second rotating speed and torque sensor is electrically connected with the measurement control system through signal transmission, and the second rotating speed and torque sensor senses the rotating speed and torque of the output side of the harmonic reducer and generates an electric signal to be transmitted to the measurement control system.
7. The device for measuring stress and strain of the flexible gear of the harmonic reducer according to claim 1, wherein the measurement control system comprises an industrial personal computer, a computer and a fiber grating demodulator, wherein the computer is electrically connected with data transmission of the industrial personal computer, the industrial personal computer is electrically connected with a driving mechanism and a loading mechanism respectively, each fiber bragg grating sensor is electrically connected with signal transmission of the fiber grating demodulator respectively, and the fiber grating demodulator is electrically connected with data transmission of the computer.
8. A harmonic reducer flexspline stress-strain measurement method based on the harmonic reducer flexspline stress-strain measurement device according to any one of claims 1 to 7, characterized by comprising the steps of:
step 1, enabling a driving mechanism to drive a harmonic reducer to rotate, and acquiring acquired data of each fiber Bragg grating sensor in a flexible gear of the harmonic reducer by a control system during rotation;
step2, obtaining strain data of the flexible gear cylinder based on a temperature-strain demodulation algorithm by utilizing grating pitch change of the fiber Bragg grating sensor; the fiber Bragg grating sensor has the following formula for temperature and strain change relation:
，
wherein the method comprises the steps of In order to be the amount of change in the pitch of the grid,Is the strain sensitivity coefficient of the fiber Bragg grating sensor,Is the temperature sensitivity coefficient of the fiber Bragg grating sensor,For the strain variation of the flexible gear cylinder,Is the temperature variation;
and 3, under the same temperature field, the strain change of the plurality of fiber Bragg grating sensors can be obtained by solving the following formula:
，
wherein, Is the grid distance variation of the kth fiber Bragg grating sensor,Is the strain sensitivity coefficient of the kth fiber Bragg grating sensor,Is the temperature sensitivity coefficient of the kth fiber Bragg grating sensor,The strain variation of the kth fiber Bragg grating sensor,K=1, 2, 3 … … n as the temperature variation;
Step 4, when the fiber Bragg grating sensor is stuck on the inner side of the flexible wheel cylinder, the strain of the fiber Bragg grating sensor at the measuring position is considered to be the same as the strain of the flexible wheel cylinder, namely =By using the strain data of the flexible gear cylinder body obtained by the steps, the stress value of the flexible gear cylinder body can be calculated based on a stress-strain equation with the following formula:
，
Wherein: is the stress of the flexible gear cylinder body, Is the elastic modulus of the flexible gear cylinder body,Is a flexible gear cylinder body strain.
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| CN109271715A (en) * | 2018-09-26 | 2019-01-25 | 北京工业大学 | A kind of harmonic reducer flexible wheel structure integrated optimization method based on gradient descent method |
| CN113587833A (en) * | 2021-07-05 | 2021-11-02 | 清华大学深圳国际研究生院 | Device and method for measuring radial deformation of flexible gear teeth of harmonic reducer |
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| TWI510720B (en) * | 2013-06-19 | 2015-12-01 | Jinn Her Entpr Co Ltd | The synchronous pre-tensionable sensing screw with fiber bragg grating devices |
| CN209458371U (en) * | 2018-12-20 | 2019-10-01 | 浙江双环传动机械股份有限公司 | A kind of harmonic speed reducer for surveying torque |
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| CN113587833A (en) * | 2021-07-05 | 2021-11-02 | 清华大学深圳国际研究生院 | Device and method for measuring radial deformation of flexible gear teeth of harmonic reducer |
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