CN115452214A - Harmonic reducer flexible gear stress-strain measurement and method - Google Patents
Harmonic reducer flexible gear stress-strain measurement and method Download PDFInfo
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- 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
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Abstract
The invention discloses a harmonic reducer flexible gear stress-strain measuring device and method, wherein the device comprises a fiber Bragg grating sensor (FBG) arranged on a harmonic reducer flexible gear, a driving mechanism and a loading mechanism for driving the harmonic reducer, and a measurement control system for acquiring signals acquired by the fiber Bragg grating sensor and performing stress-strain measurement calculation, wherein a signal line of a sensor on a rotary flexible gear is led out by utilizing the hollow design of an output shaft of the harmonic reducer, and finally the stress-strain measurement of the harmonic reducer flexible gear 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 the structural parameters, and has important significance for intelligent operation and maintenance of the harmonic reducer and flexible gear optimization.
Description
Technical Field
The invention relates to the field of harmonic reducer measurement systems, in particular to a harmonic reducer flexible gear stress-strain measurement method.
Background
The harmonic reducer is a gear transmission mechanism which can make flexible gear produce controllable elastic deformation by means of wave generator and can utilize small tooth difference engagement of flexible gear and rigid gear to make movement and power transmission, and has the characteristics of high accuracy, large transmission ratio and small return difference, etc. so that it can be extensively used in the fields of robot, aerospace, precision machine tool and medical equipment, etc. The flexible gear is used as the most critical part in the harmonic reducer, and the large deformation generated by the joint 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 the dual actions of the wave generator and external loading in the working process, is subjected to bending stress and torsional stress in a cyclic elastic deformation state, and the deformation 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, because the flexible gear can bear periodic alternating stress for a long time in the working process, 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, stress-strain research on a flexible gear of a harmonic reducer 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 stress and strain of the flexible gear can be divided into a circular test method for a single flexible gear part and a measurement scheme for a whole harmonic reducer. The first method is to design a specific experimental device for a single flexible gear part to simulate the action of a wave generator on a flexible gear, and then measure the stress-strain state of the flexible gear through a sensor. For example, the chinese patent application No. CN 202022335562.5: a flexible gear performance testing device for a harmonic reducer. The device simulates a wave generator and is driven by a motor through a cam lever mechanism, and can carry out angle test, deformation test, cyclic stress test and fatigue life test on a single flexible gear part under different working conditions. For another example, the chinese patent application No. CN 202010789069.2: a harmonic drive flexible gear radial deformation reconfigurable measuring device. The measuring device realizes the measurement of the deformation of the flexible gear through a feedback system consisting of a high-precision turntable system, a torque motor and a circular grating, the contact cooperation of a wave generator and a flexible bearing simulation and a measuring system of a laser range finder. In addition, the invention can realize the measurement of the deformation of different flexible gears under the action of different 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 still part-level flexible gear performance testing methods essentially, and the boundary conditions of the flexible gear in the assembly state of the harmonic reducer, the boundary effect of the gear contact area, the stress distribution of the rigid gear to the flexible gear cylinder and the contact state of actual meshing teeth cannot be considered. Therefore, the method often 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 flexible gear under the complete state of the harmonic reducer. For example, the chinese patent application No. CN 202110755675.7: a device and a method for measuring radial deformation of a flexible gear tooth of a harmonic reducer are disclosed. The device forms an observation gap by processing on a rigid gear of the harmonic reducer, and utilizes a laser displacement sensor to respectively measure the radial deformation of the teeth of the flexible gear at different positions of the meshing motion of the harmonic reducer along the central shaft direction of the reducer. The device can realize the measurement of the deformation of the gear teeth of the flexible gear of the harmonic reducer in the working state, but the measurement principle of a laser displacement sensor is limited, and the measurement of the stress and strain of the flexible gear cylinder body which is concerned more cannot be realized.
Therefore, it is important to develop a measuring device and a measuring method for measuring and simulating the stress strain of the flexible gear of the harmonic reducer under multiple working conditions without damaging the structure of the reducer.
Disclosure of Invention
The invention aims to provide a stress-strain measurement method for a flexible gear of a harmonic reducer, and aims to solve the problem that the stress-strain is difficult to measure when the flexible gear of the harmonic reducer rotates in the prior art.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a stress-strain measurement method for a flexible gear of a harmonic reducer is characterized by comprising 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 provides power on the input side of the harmonic reducer; the loading mechanism is connected with an output shaft of the harmonic reducer and provides power on the output side of the harmonic reducer; the measuring assembly comprises a plurality of fiber Bragg grating sensors, the fiber Bragg grating sensors are fixed on the inner surface of a flexible gear in the harmonic reducer, and each fiber Bragg grating sensor senses stress strain when the flexible gear 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 mode, each fiber Bragg grating sensor is respectively and electrically connected with the measurement control system in a signal transmission mode, and the measurement control system obtains the stress strain quantity of the flexspline based on signals collected by the fiber Bragg grating sensors.
Furthermore, 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 mode.
Furthermore, a first rotating speed and torque sensor is mounted on the first shaft transmission mechanism and is electrically connected with the measurement control system in a signal transmission mode, and the first rotating speed and torque sensor senses rotating speed and torque on the input side of the harmonic speed reducer and generates an electric signal to be transmitted to the measurement control system.
Furthermore, the loading mechanism comprises a loading motor, a second shaft transmission mechanism, a belt wheel transmission mechanism and a third shaft transmission mechanism, the third shaft transmission mechanism of a motor shaft 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 fixing end, the slip ring rotating end and the slip ring fixing end are in relative rotating fit and keep electric contact, and the slip ring rotating end is fixed on the hollow shaft and rotates along with the hollow shaft; data wires of the optical fiber Bragg grating sensors penetrate into the hollow shaft from a hollow output shaft of the harmonic reducer respectively, penetrate out of the hollow shaft and are collected to be electrically connected to a slip ring rotating end; the slip ring fixed end does not rotate along with the hollow shaft, and the slip ring fixed end is electrically connected with a signal transmission electric connection of a measurement control system.
Furthermore, a second rotating speed and torque sensor is installed on the second shaft transmission mechanism, the second rotating speed and torque sensor is electrically connected with the measurement control system in a signal transmission mode, and the second rotating speed and torque sensor senses rotating speed and torque on the output side of the harmonic reducer and generates an electric signal to be transmitted to the measurement control system.
Furthermore, the measurement control system comprises an industrial personal computer, a computer and a fiber grating demodulator, wherein the computer is electrically connected with the industrial personal computer in a data transmission manner, the industrial personal computer is respectively and electrically connected with the driving mechanism and the loading mechanism in a control manner, each fiber bragg grating sensor is respectively and electrically connected with the fiber grating demodulator in a signal transmission manner, and the fiber grating demodulator is electrically connected with the computer in a data transmission manner.
A stress-strain measurement method for a flexible gear of a harmonic reducer comprises the following steps:
Δλ B ＝(K ε Δε+K T ΔT)，
wherein Δ λ B Is the amount of variation in pitch, K ε Is the strain sensitivity coefficient, K, of a fiber Bragg grating sensor T The temperature sensitivity coefficient of the fiber Bragg grating sensor is shown, wherein delta epsilon is the strain variation of the flexspline cylinder, and delta T is the temperature variation;
and 3, under the same temperature field, the strain changes of the plurality of fiber Bragg grating sensors can be obtained by solving the following formula:
wherein, Δ λ Bk For the kth fiber Bragg grating transmissionVariation of sensor grid pitch, K εk Is the strain sensitivity coefficient, K, of the kth fiber Bragg grating sensor Tk Temperature sensitivity coefficient of the kth fiber Bragg grating sensor, delta epsilon k Is the strain variation of the kth fiber Bragg grating sensor, delta T is the temperature variation, k =1, 2, 3 … … n;
σ c ＝E c ·Δε c ，
wherein: sigma c For cylinder stress of flexspline E c Is the elastic modulus of flexspline cylinder, delta Epsilon c Strain of flexspline cylinder.
The invention provides a device and a method for measuring stress-strain of a flexible gear of a harmonic reducer, which can realize stress-strain distribution characteristics, performance detection and fatigue life measurement 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 flexible gear of the harmonic reducer, the hollow design of the output shaft of the harmonic reducer is utilized to lead out the signal line of the sensor on the rotary flexible gear, and finally the stress strain measurement of the flexible gear of the harmonic reducer under the dynamic working condition is realized through the slip ring. The stress strain of the flexible gear of the harmonic reducer can be measured under different working conditions, effective load basis and guide parameters are provided for monitoring the internal meshing state of the harmonic reducer and optimizing the design of structural parameters, and the method has important significance for optimizing the flexible gear of the harmonic reducer.
The invention has the following difference and beneficial effects compared with the prior art:
1. the measuring device and the method provided by the invention adopt an internal measuring technology, avoid an additional flexible gear deformation generating device, can realize stress-strain measurement of the flexible gear in a working state, and have a simpler mechanical structure.
2. When the stress-strain measurement of the flexible gear of the harmonic reducer is carried out, the structure of the harmonic reducer cannot be damaged, the constraint condition of the flexible gear and the meshing condition of the gear teeth cannot be changed, the real working state of the flexible gear of the harmonic reducer can be ensured to the greatest extent, and the method has better economy.
3. According to the invention, through the design of the hollow shafts with different sizes, the harmonic reducers with different models can be replaced, so that the stress strain measurement of the flexible gears of the harmonic reducers with different sizes and models is realized, and the device has wider applicability.
Drawings
FIG. 1 is a schematic view of an embodiment of the present invention.
Fig. 2 is a schematic diagram of a strain test structure of a flexible gear of a harmonic reducer according to an embodiment of the invention.
Fig. 3 is a schematic view illustrating an installation of a flexspline fiber bragg grating sensor of the harmonic reducer according to the embodiment of the present invention.
Fig. 4 is a schematic diagram illustrating the installation of the rotational speed and torque sensor according to the embodiment of the present invention.
Fig. 5 is a schematic view of the installation of the harmonic reducer according to the embodiment of the invention.
Fig. 6 is a schematic view of the slip ring installation in the embodiment of the present invention.
Fig. 7 is a flow chart of a method for measuring stress-strain of a flexible gear of a harmonic reducer according to an embodiment of the invention.
The reference numbers in FIG. 1 illustrate: the device comprises a base 1, a driving motor 2, a coupling I3, a rotating speed and torque sensor I4, a transmission shaft I5, a coupling II 6, a reducer input shaft 7, a harmonic reducer 8, a reducer output shaft 9, a coupling III 10, a rotating speed and torque sensor II 11, a hollow shaft I12, a coupling IV 13, a hollow shaft II 14, a belt 15, a belt pulley driven wheel 16, a slip ring 17, a belt pulley driving wheel 18, a transmission shaft II 19, a coupling V20, a loading motor 21 and a signal line 22.
The designations in FIG. 2 illustrate: 2001-box, 2002-rigid wheel, 2003-wave generator, 2004-bearing, 2005-flexspline, 2006-roller bearing outer ring, 2007-hexagon socket screw, 2008-fiber Bragg grating sensor, 2009-data wire, 9-output shaft, 2011-gasket, 2012-oil seal, 2013-cover plate, 12-hollow shaft I, 14-hollow shaft II, 17-slip ring.
The designations in FIG. 3 illustrate: 2005-flexspline, 2008-fiber bragg grating.
The designations in FIG. 4 illustrate: 4-a rotating speed torque sensor, 4001-a flange plate, 4002-a fixing bolt, 4003-a sensor base and 4004-a fixing bolt.
The designations in FIG. 5 illustrate: 8-harmonic reducer, 8001-harmonic reducer support, 8002-fixing bolt.
The designations in fig. 6 illustrate: 14-hollow shaft, 1401-signal wire reserved hole, 1402-fixing screw, 1403-slip ring rotation end, 1404-slip ring rotation end lead terminal, 1405-slip ring fixing end and 1406-slip ring fixing end lead terminal.
Detailed Description
The invention is further illustrated with reference to the following figures and examples.
Referring to fig. 1, the flexible gear stress-strain measuring device of the harmonic reducer of the present 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 through foundation bolts or fixed on other stable platforms through bolts. The base module is used for providing a fixed base for the driving mechanism, the loading mechanism, the transmission mechanism and the measurement control system and ensuring specific assembly relation.
The driving mechanism comprises a driving motor 2, a first coupler 3, a first transmission shaft 5 and a second coupler 6. The driving motor 2 is fixed on the base 1 through bolts and has the function of providing constant rotating speed and torque for the experimental device of the harmonic reducer 8 together with the loading motor 21. A 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 thus outputs power to the input side of the harmonic reducer via the first shaft transmission.
The loading mechanism comprises a loading motor 21, a third coupling 10, a first hollow shaft 12, a fourth coupling 13, a second hollow shaft 14, a belt 15, a belt wheel driven wheel 16, a belt wheel driving wheel 18, a second transmission shaft 19 and a fifth coupling 20. The output shaft 9 of the harmonic reducer 8 is connected with one end of a first hollow shaft 12 through a third coupling 10, the other end of the first hollow shaft 12 is connected with one end of a second hollow shaft 14 through a fourth coupling 13, and a second shaft transmission mechanism is formed by the third coupling 10, the first hollow shaft 12, the fourth coupling 13 and the second hollow shaft 14. An output shaft of the loading motor 21 is connected with one end of the second transmission shaft 19 through a fifth coupling 20, and a third shaft transmission mechanism is formed by the fifth coupling 20 and the second transmission shaft 19. The belt wheel driving wheel 18 is coaxially fixed on the second transmission shaft 19, the belt wheel driven wheel 16 is coaxially fixed on the second hollow shaft 14, the belt wheel driving wheel 18 and the belt wheel driven wheel 16 are in transmission connection through a 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 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, the second hollow shaft 14 in the second shaft transmission mechanism is equipped with the slip ring 17, specifically as shown in fig. 6, the slip ring 17 includes a slip ring rotation end 1804 and a slip ring fixing end 1806, the slip ring rotation end 1804 and the slip ring fixing end 1806 are relatively rotationally matched and electrically contacted, and the ring rotation end 1804 is coaxially fixed on the second hollow shaft 14 and rotates with the second hollow shaft 14.
The loading mechanism and the driving mechanism together provide constant rotating speed and torque for the harmonic reducer experimental device. In the installation process, the loading motor 21, the fifth coupling 20, the second transmission shaft 19 and the belt wheel driving wheel 18 are coaxially installed. In addition, the center-to-center distance between the pulley drive pulley 18 and the pulley driven pulley 16 can be fine-tuned to ensure belt drive synchronization during installation, taking into account belt elasticity.
In order to ensure the coaxiality of the shafts, a fixed base can be arranged at the bottom of a part with a smaller shaft center height according to the shaft center heights of different parts in the assembling process. The pulley driven wheel 16 and the pulley driving wheel 18 are used for eliminating the influence of motor vibration to a certain extent, and are used for installing a slip ring 17 in a measurement control system and leading out signal wires in a speed reducer.
In the embodiment, a first rotating speed and torque sensor 4 is coaxially mounted on the first transmission shaft 5, and a second rotating speed and torque sensor 11 is coaxially mounted on the first hollow shaft, wherein the first rotating speed and torque sensor 4 senses the rotating speed and torque on the input side of the harmonic speed reducer 8, and the second rotating speed and torque sensor 11 senses the rotating speed and torque data on the output side of the harmonic speed reducer 8. The first rotating speed torque sensor 4 and the second rotating speed torque sensor 11 are respectively 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 all shafts in a transmission system, sensor mounting bases are respectively designed at the bottoms of the first rotating speed and torque sensor 4 and the second rotating speed and torque sensor 11, the lower end of each base is fixed on a base through a bolt, and the upper end of each base is connected with the corresponding torque rotating speed sensor through a bolt.
Referring to fig. 2 and 3, in the present embodiment, first, the rigid wheel 2002, the wave generator 2003, and the bearing 2004 are assembled to the case 2001, and a plurality of fiber bragg grating sensors 2008 are mounted inside the cylinder of the flexspline 2005 of the harmonic reducer, and the plurality of fiber bragg grating sensors 2008 are uniformly distributed circumferentially around the central axis of the flexspline 2005. In the installation process, because the fiber bragg grating sensor 2008 is very thin, it should be carefully arranged to achieve a higher survival rate of the sensor and to sufficiently sense the strain condition of the monitored object. A signal lead terminal of the fiber bragg grating sensor 2008 is fixed on the flexspline 2005, and a signal wire 2009 of the fiber bragg grating sensor 2008 is led out to a slip ring rotation end 1403 of a shaft end through a hollow shaft 12 and a hollow shaft 17 through a hollow shaft 9 at an output end of the harmonic reducer 8. A roller bearing outer race 2006, a washer 2011, an oil seal 2012 and a cover plate 2013 are assembled to the case 2001 at the right end of the harmonic reducer using a socket head cap screw 2007.
In the process of installing the fiber bragg grating sensor 2008 on the inner side of the flexible gear 2005 of the harmonic reducer, the gratings are very fine and should be carefully arranged, so that the high survival rate of the sensor is achieved, and the strain condition of a monitored object is fully sensed. 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 coated on an iron sheet of the fiber bragg grating sensor 2008, and the sensor is pressed on the surface of an object for a period of time, so that the bonding strength is ensured, and the sensor is adhered to a position needing distribution. Further, the lead wire of the fiber bragg grating sensor 2008 is led out through the inside of the hollow shaft.
In this embodiment, the measurement control system includes industrial computer, fiber grating demodulator, and data communication is connected between industrial computer, the industrial computer respectively with driving motor 2, loading motor 21 control electricity and be connected to rotational speed torque sensor 4, rotational speed torque sensor two 11 are connected with industrial computer signal transmission electricity respectively. The input of the fiber grating demodulator is electrically connected with the slip ring fixing end 1806 of the slip ring 17 through the signal line 22 in a signal transmission manner, and the output of the fiber grating demodulator is electrically connected with the data transmission of the 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, the embodiment is described by taking a first rotational speed and torque sensor 4 as an example, the first rotational speed and torque sensor 4 is fixed on a sensor base 4003 through a fixing bolt 4002, the sensor base 4003 is fixed on a base 1 through the fixing bolt 4004 to ensure the coaxiality of shafts, and a transmission shaft (i.e., a first transmission shaft 5) can be connected to the first rotational speed and torque sensor 4 through a flange 4001 to realize the measurement of the rotational speed and the torque of the shafts.
Referring to fig. 5, the harmonic reducer 8 is fixed to a harmonic reducer support 8001 by a bolt 8002, and a bolt hole is formed in the bottom of the harmonic reducer support 8001 and can be used for fixing the harmonic reducer support 8001 to the base 1.
Referring to fig. 6, the flexspline 2005 is always in a rotating state during the operation of the harmonic reducer 8, and a slip ring is mounted at the end of the hollow shaft 14 for leading out the signal line of the rotating component, wherein the hollow shaft 14 and the slip ring rotating end 1803 are fixedly connected through a fixing screw 1802. The sensor signal line in the second hollow shaft 14 is led out through the signal line reserved hole 1401 of the second hollow shaft 14 and is connected to the slip ring rotation end lead terminal 1404, and further, at the slip ring fixing end 1405, the signal line connected into the fiber grating demodulator can be connected with the fixing end lead terminal 1406 of the slip ring to achieve signal transmission.
As shown in fig. 7, in the stage of assembling and installing the harmonic reducer flexspline stress-strain measuring device, the power supply needs to be disconnected, 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 first torque speed sensor 4, the harmonic reducer 8, the second speed torque sensor 11 and the belt wheel driven wheel 6 are fixedly installed on the base 1 through bolts, the driving motor 2 and the input end of the harmonic reducer 8 are sequentially connected through the coupler 3, the transmission shaft 5 and the coupler 6, the output end of the harmonic reducer and the belt wheel driven wheel 16 are sequentially connected through the coupler 11 from left to right, the hollow shaft 13, the coupler 14 and the hollow shaft 15, and the output shaft of the driving motor, the transmission shaft, the hollow shaft and the shaft of the speed reducer are required to be ensured to be in the same axis 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 is prevented from slipping and being tensed excessively. The belt wheel driving wheel 18 and the loading motor 21 are arranged on the base, so that the axes of the belt wheel driving wheel 18, the transmission shaft 19, the coupler 20 and the loading motor output shaft 21 are ensured to be on the same central line.
(3) In the harmonic reducer 8, the fiber bragg grating sensor 2008 is installed on the inner side of the flexible gear 2005, and in the installation process, because the grating is very fine, the grating should be carefully arranged, so that the higher survival rate of the sensor is achieved, and the strain condition of the monitored object is fully sensed. The arrangement process comprises the following steps: the inner surface of the flexspline cup is first polished and cleaned using sandpaper and alcohol. The adhesive is coated on an iron sheet of the optical fiber sensor, and the sensor is pressed on the surface of an object for a period of time to ensure the bonding strength and is adhered to a position needing distribution.
(4) A sensor signal lead terminal is fixed on the flexible gear 2005, and a signal passes through the shaft ends of the hollow output shaft 12 and the hollow shaft 14 of the harmonic reducer. Further, a slip ring is mounted at the end of hollow shaft 14, wherein hollow shaft 14 is connected to slip ring rotating end 1403 by 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 slip ring rotation end lead terminal 1404.
(5) A lead terminal 1406 at the fixed end of the slip ring is connected with a signal wire, and the other end of the signal wire is connected with the fiber bragg grating demodulator. Further, the optical fiber demodulator is connected to the 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 and torque sensor, the fiber bragg grating demodulator, the industrial computer and the notebook computer;
(7) Starting the fiber grating monitoring system, comprising the following implementation steps: and the sensor is connected into the corresponding channel according to the requirement, and the transmission of the parameter signal is realized through the optical cable. And (3) analyzing, demodulating and storing the signals entering the demodulator in real time, and finally outputting the demodulated signals to a screen end to directly reflect the measured real-time stress strain signals.
(8) And starting the industrial personal computer and the industrial computer, and controlling the rotating speed and the torque of the driving motor and the loading motor so as to realize the stress-strain measurement of the flexible gear under different working conditions.
The stress-strain measurement method for the harmonic reducer flexible gear based on the stress-strain measurement device comprises the following steps:
Δλ B ＝(K ε Δε+K T ΔT)，
wherein Δ λ B Is the amount of variation in pitch, K ε Is the strain sensitivity coefficient, K, of a fiber Bragg grating sensor T The temperature sensitivity coefficient of the fiber Bragg grating sensor is shown, wherein delta epsilon is the strain variation of the flexspline cylinder, and delta T is the temperature variation;
and 3, under the same temperature field, the strain changes of the plurality of fiber Bragg grating sensors can be obtained by solving the following formula:
wherein, Δ λ Bk Is the variation of the pitch, K, of the kth fiber Bragg grating sensor εk Is the strain sensitivity coefficient, K, of the kth fiber Bragg grating sensor Tk Temperature sensitivity coefficient of the kth fiber Bragg grating sensor, delta epsilon k Is the strain variation of the kth fiber Bragg grating sensor, delta T is the temperature variation, k =1, 2, 3 … … n;
σ c ＝E c ·Δε c ，
wherein: sigma c For cylinder stress of flexspline E c Is the elastic modulus of flexspline cylinder, delta Epsilon c Strain of the flexspline cylinder.
The embodiments of the present invention are described only for the preferred embodiments of the present invention, and not for the limitation of the concept and scope of the present invention, and various modifications and improvements made to the technical solution of the present invention by those skilled in the art without departing from the design concept of the present invention shall fall into the protection scope of the present invention, and the technical content of the present invention which is claimed is fully set forth in the claims.
Claims (8)
1. A stress-strain measurement method for a flexible gear of a harmonic reducer is characterized by comprising 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 provides power on the input side of the harmonic reducer; the loading mechanism is connected with an output shaft of the harmonic reducer and provides power on the output side of the harmonic reducer; the measuring assembly comprises a plurality of fiber Bragg grating sensors, the fiber Bragg grating sensors are fixed on the inner surface of a flexible gear in the harmonic reducer, and each fiber Bragg grating sensor senses stress strain when the flexible gear 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 mode, each fiber Bragg grating sensor is respectively and electrically connected with the measurement control system in a signal transmission mode, and the measurement control system obtains the stress strain quantity of the flexspline based on signals collected by the fiber Bragg grating sensors.
2. The harmonic reducer flexspline stress-strain measurement of claim 1, characterized in that the drive mechanism comprises a drive motor and a first shaft transmission mechanism, a motor shaft of the drive 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 drive motor.
3. The harmonic reducer flexspline stress-strain measurement of claim 1, characterized in that a first rotation speed and torque sensor is installed on the first shaft transmission mechanism, the first rotation speed and torque sensor is electrically connected with a measurement control system in a signal transmission manner, and the first rotation speed and torque sensor senses rotation speed and torque on the input side of the harmonic reducer and generates an electric signal to be transmitted to the measurement control system.
4. The harmonic reducer flexible gear stress-strain measurement device according to claim 1, wherein the loading mechanism comprises a loading motor, a second shaft transmission mechanism, a belt pulley transmission mechanism and a third shaft transmission mechanism, the third shaft transmission mechanism of a motor shaft of the loading motor is connected with a belt pulley driving wheel in the belt pulley transmission mechanism, and a belt pulley driven wheel in the belt pulley transmission mechanism is connected with an output shaft of the harmonic reducer through the second shaft transmission mechanism.
5. The harmonic reducer flexspline stress-strain measurement according to claim 4, wherein the secondary shaft transmission 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 fixing end, the slip ring rotating end and the slip ring fixing end are in relative rotation fit and maintain electrical contact, and the slip ring rotating end is fixed on the hollow shaft and rotates with the hollow shaft; data leads of the fiber Bragg grating sensors penetrate into the hollow shaft from a hollow output shaft of the harmonic reducer respectively, penetrate out of the hollow shaft and are collected to be electrically connected to a slip ring rotating end; the slip ring fixed end does not rotate along with the hollow shaft, and the slip ring fixed end is electrically connected with a signal transmission electric connection of a measurement control system.
6. The harmonic reducer flexspline stress-strain measurement of claim 4, characterized in that a second rotational speed and torque sensor is mounted on the second shaft transmission mechanism, the second rotational speed and torque sensor is electrically connected with the measurement control system in a signal transmission manner, and the second rotational speed and torque sensor senses rotational speed and torque on the output side of the harmonic reducer and generates an electric signal to be transmitted to the measurement control system.
7. The harmonic reducer flexspline stress-strain measurement device 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 the industrial personal computer in a data transmission manner, the industrial personal computer is electrically connected with the driving mechanism and the loading mechanism respectively in a control manner, each fiber bragg grating sensor is electrically connected with the fiber grating demodulator in a signal transmission manner, and the fiber grating demodulator is electrically connected with the computer in a data transmission manner.
8. A harmonic reducer flexspline stress-strain measurement method based on the measurement device of any one of claims 1-7, characterized by comprising the following steps:
step 1, enabling a driving mechanism to drive a harmonic reducer to rotate, and acquiring data acquired by each fiber Bragg grating sensor in a flexible gear of the harmonic reducer during rotation by a control system;
step 2, obtaining strain data of the flexible wheel cylinder body by using the grating pitch change of the fiber Bragg grating sensor based on a temperature-strain demodulation algorithm; the relationship between the fiber Bragg grating sensor and the temperature and strain changes is shown as the following formula:
Δλ B ＝(K ε Δε+K T ΔT)，
wherein Δ λ B Is the amount of variation in pitch, K ε Is the strain sensitivity coefficient, K, of a fiber Bragg grating sensor T The temperature sensitivity coefficient of the fiber Bragg grating sensor is shown, wherein delta epsilon is the strain variation of the flexspline cylinder, and delta T is the temperature variation;
and 3, under the same temperature field, the strain changes of the plurality of fiber Bragg grating sensors can be obtained by solving the following formula:
wherein, Δ λ Bk (for the variation of the pitch of the kth fiber Bragg grating sensor, K εk Is the strain sensitivity coefficient, K, of the kth fiber Bragg grating sensor Tk Temperature sensitivity coefficient of the kth fiber Bragg grating sensor, delta epsilon k Is the strain variation of the kth fiber Bragg grating sensor, delta T is the temperature variation, k =1, 2, 3 … … n;
step 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 is considered to be the same as that of the flexible gear cylinder at the measuring position, namely delta epsilon c ＝Δε k And calculating the stress value of the flexible gear cylinder by using the strain data of the flexible gear cylinder obtained in the step based on a stress-strain equation of the following formula:
σ c ＝E c ·Δε c ，
wherein: sigma c For cylinder stress of flexspline E c Is the elastic modulus of flexspline cylinder, delta epsilon c Strain of the flexspline cylinder.
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