Non-contact torque real-time measurement device and method based on dispersion confocal method

Abstract

The invention discloses a non-contact torsion angle gamma, torque T, rotating speed n, angular acceleration beta and vibration characteristic multi-parameter measurement system and method based on a co-collimation double-color scattered confocal technology. The measurement system is composed of a controller, a co-collimation double-color scattered confocal module and two radius coding auxiliary rings. A wide-spectrum light source, a spectrum demodulation device, a torque and rotating speed calculation module and the like are arranged in the controller. The double-color-dispersion confocal module shares the collimation light path and the confocal small hole. The outer diameter h of the radius coding auxiliary ring linearly increases along the circumferential angle # imgabs0 #. The torque angle and the torque of the shaft are calculated by the focal light wavelength lambda i and the wavelength difference delta lambda i variation received by the double-color-dispersion confocal module, the geometric parameters of the shaft and the shear elastic modulus G, and the rotating speed, the angular acceleration and the vibration characteristic of the shaft are calculated by utilizing the rotating periodicity of the auxiliary ring. The method has the characteristics of non-contact type, high precision, no electromagnetic interference, strong environmental adaptability and the like, and is expected to be used for main shaft torque measurement and intelligent control decision of precision machinery such as motors, engines, machine tools and the like.

Description

Technical Field

[0001] The present invention belongs to the field of non-contact measurement of the torsional angle, torque, rotational speed, and angular acceleration of a precision mechanical spindle, and relates to a non-contact torsional angle, torque, rotational speed, and vibration characteristic measurement system and method based on the co-collimation bichromatic dispersion confocal technology. Background Art

[0002] Torque is the moment that causes an object to rotate, including static torque and dynamic torque. Static torque is usually applied to a shaft fixed at one end and stressed at the other end, while dynamic torque is usually on a rotating shaft, such as a motor shaft or a transmission shaft. In most mechanical fields with rotary motion or shaft parts, such as airplanes, automobiles, machine tools, and engineering machinery, the torque of static shafts and rotating shafts is an extremely important parameter, which affects system stress, structural stability, power transmission and efficiency, drive control and its accuracy. Coupled with the rapid development of motor and control technologies, more and more devices use motor drive and control to achieve automation, such as new energy vehicles, intelligent driving vehicles, turbine spindles, robots, etc.; while traditional contact torque sensing is based on coupling strain measurement, which weakens the overall stiffness and transmission accuracy of the shaft in principle. Therefore, non-contact torque measurement has become a key task for measuring and controlling the state of mechanical equipment.

[0003] For the rotating shaft in the field of the above-mentioned mechanical equipment, the requirements for the accuracy and efficiency of torque transmission are very high, and the transmitted torque and power are often fed back to the control system to achieve precise control and affect the system performance. At the same time, in order to avoid scratches, abrasions, indentations, corrosion, or to avoid inaccurate measurements caused by contact stress and vibration, it is necessary to use non-contact measurement methods for measurement. At present, the vast majority of torque measurement methods are through strain-based contact measurement methods, that is, a strain torque sensor is connected to the shaft to achieve measurement. This method not only occupies the shaft space, bringing inconvenience to installation, but also reduces the overall stiffness of the transmission shaft, thereby reducing the load capacity, accuracy and efficiency of the transmission system; and the current non-contact torque measurement methods mainly include magnetoelastic, magnetoelectric, magnetosensitive, laser Doppler, surface acoustic wave, grating and fiber optic sensing and other measurement methods. Magnetic sensors are designed based on the principle that the extrusion between the key and the keyway during the torsional deformation of the shaft causes a change in the magnetic field on the shaft. For motor shafts and live shafts, this method is extremely vulnerable to electromagnetic interference and there are measurement errors or even failures, and it is also severely interfered by vibration. At the same time, it is difficult to measure the torque of shafts without keyways. The surface acoustic wave method (SAW) measures the strain in the direction of 45° to the shaft based on the assistance of a piezoelectric substrate and wireless communication to achieve torque measurement. This method requires the piezoelectric effect of the substrate and has extremely high requirements for the environment such as temperature, humidity, and dust. At the same time, the communication is vulnerable to interference and the current technology is not yet mature. Grating measurement is based on the calculation of the bright and dark fringes generated by the misalignment of the light source and the optoelectronic device on both sides of the circular hole to achieve torque measurement. An auxiliary disc needs to be installed on the shaft. It has high sensitivity and a relatively fast response speed, but it is not suitable for measuring the torque of shafts with small deformations. At the same time, its stability is poor and it is easily interfered by vibration, shaft tilt, etc. Laser Doppler method is based on the frequency difference generated by two beams of light after the light split from the same light source beam is reflected back to the photodetector by the shaft surface at a certain distance. Its efficiency, sensitivity and accuracy are all relatively high, but due to the reflection characteristics of light, it is not suitable for measuring the torque of shafts with small diameters, nor for static torque measurement. At the same time, it is easily interfered by vibration and environmental conditions.

[0004] In summary, it is difficult for the existing relatively mature technologies to meet the torque measurement of a single method for complex working conditions; therefore, a torque measurement method based on chromatic confocal technology is proposed. Based on the analysis of optical wavelength coding, it can achieve precise torque measurement, and adopts a dual-probe method, which can achieve multi-parameter measurement such as rotational speed, vibration characteristics, and torsional deformation. At the same time, the data obtained by the two probes can achieve adaptive error correction, reduce vibration interference, and take into account static torque measurement and dynamic on-line torque measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Figure 1 It is the structure and schematic diagram of a multi-parameter non-contact measurement system for torque, rotational speed, etc. based on co-collimated dual-chromatic confocal technology of the present invention; Among them, the controller 1 integrates multi-parameter calculation modules such as a light source, a spectral demodulation system, and torque; 2 is a communication optical fiber; 3 is a beam coupler; 4 is a mirror; 5 is a collimating lens group; 6 is a beam splitter prism with a 50% splitting ratio; 7 is a dispersion lens group; 8 is a beam splitter prism with a 100% splitting ratio; 9 is a confocal pinhole, 10 is the measured shaft, 11 is the radius coding auxiliary ring 2, and 12 is the measurement auxiliary ring 1.

[0006] Figure 2 It is a schematic diagram of the torque measurement and calculation principle based on the two-dispersion confocal technology in the present invention.

[0007] Figure 3 It is the theoretical calculated value and curve of the torque measurement method proposed by the present invention. Attached Figure 3 (a) represents the relationship curve between the twist angle and torque of different selected materials; Attached Figure 3 (b) represents the minimum torque (resolution) that the dispersion confocal sensing module with a resolution of 100 nm can sense for different shear elastic moduli.

[0008] Figure 4 It is the simple experimental verification result and curve of the torque measurement method proposed by the present invention. Figure 4 (a) is the comparison curve between the experimental test value and the test value of the commercial sensor; Figure 4 (b) is the received value and curve of the two dispersion confocal sensing modules during on-line cyclic measurement. Specific embodiments

[0009] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

[0010] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and do not have to be used to describe a specific order or sequence. It should be understood that such used data can be interchanged under appropriate circumstances so that the embodiments of the present invention described here can be implemented in an order different from those illustrated or described here. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0011] The present invention will be further described in detail below with reference to the accompanying drawings: See Figure 1 , a non-contact multi-parameter measurement system and method for torsional angle, torque, rotational speed, vibration characteristics, etc. based on the chromatic confocal technology disclosed by the present invention; including a controller 1 integrating a light source, a spectral demodulation system, a multi-parameter calculation module such as torque, which emits a broadband light source in a certain wavelength band, and through an input / output optical fiber 2 and a beam coupler 3, is incident on a co-collimated dual-chromatic confocal sensing module integrating a reflecting mirror 4, a collimating lens group 5, beam split prisms 6 and 8, and a chromatic dispersion lens group 7. The light beam enters two focusing lenses through the two beam split prisms respectively. Measurement auxiliary rings 11 and 12 are arranged on the axis at the corresponding positions of the focal points of the two focusing lenses. The light beam is reflected back to the chromatic confocal sensing module by the outer surface of the auxiliary ring, passes through the reflecting mirror 4 to the confocal small hole, and then to the spectral demodulation module in the controller; the auxiliary ring HCR is made of a light-weight surface-reflective material, and after installation, there is no relative sliding or deformation with the shaft. After installation, its radial (axial cross-section) height is linearly related to the swept central angle. Therefore, when the shaft rotates or undergoes torsional deformation, the focal wavelength will change, and it is linearly related to the torsional angle. Furthermore, torque measurement is achieved through wavelength analysis, calculation, and calibration.

[0012] Among them, the co-collimated dual-chromatic confocal measurement module of the present invention is integrated with the same collimating lens group, beam split prisms with beam split ratios of 50% and 100% respectively, and two separate chromatic dispersion lens groups, which can achieve the parameter consistency of the light beams incident on the two focusing lenses, including the optical wavelength band, optical frequency spectrum, and optical noise. At the same time, the structure is compact, which helps to reduce the influence of aberration, facilitate rapid installation adjustment and calibration measurement, and can also be further improved into a measurement system integrated with micro-nano devices to further expand the application range.

[0013] The non-contact torque measurement system in the present invention can achieve multi-parameter measurement of torsional angle, torque, rotational speed, angular acceleration, and vibration characteristics. Among them, the rotational speed, angular acceleration, and vibration characteristics can be calculated from the data obtained by any one of the probes. The principle is shown in the appendix Figure 2 , when the shaft rotates, the auxiliary ring rotates accordingly, so that the focal reflection wavelength changes periodically, and further the rotational speed and angular acceleration are calculated. Moreover, by comparing the static measurement curve and the on-line measurement curve, the vibration characteristics can be reflected; for the calculation of the torsional angle and torque, the data obtained by the two probes need to participate in the calculation together. The principle is shown in the appendix Figure 2 , according to the wavelength-time curves under no-load and with torque, the wavelength difference can be calculated. The wavelength difference can linearly reflect the torsional deformation angle, and further the torque is calculated in combination with the shear modulus and cross-sectional moment of inertia of the shaft.

[0014] The torque measurement method in the present invention can take into account both static torque measurement and on-line torque measurement. The principle is shown in the appendix Figure 2, for static torque measurement, when a load torque is applied, the shaft will undergo torsional deformation, and the focal reflection wavelength will shift. The chromatic confocal technology can measure fine deformations and displacements. Since the positions of the two probes are different, the offset amounts are different. By using the wavelength difference and geometric relationship, the torsional deformation angle can be calculated, and then the torque can be calculated by combining the physical parameters of the shaft. For on-line measurement, there are periodicities on the time axis and the rotational angle axis. By analyzing the curve on the time axis, the shaft speed, angular acceleration, and vibration characteristics can be obtained. By combining the curves on the two axes, the wavelength difference at each moment can be calculated to achieve real-time torque calculation. For vibration interference, the wavelength-time curves and wavelength-difference-time curves of the two probes can be combined, and some error correction algorithms can be used to complete adaptive error correction.

[0015] The specific measurement steps are as follows: 1) Obtain the physical parameters of the shaft (density ρ or shear modulus G, shaft diameter D); 2) Install two measurement auxiliary rings according to the shaft force condition. If it is a single-end fixed shaft, install them in the reverse direction. If it is a two-end loaded shaft, install them in the same direction. Calculate and calibrate the radial height after installation. According to the maximum value, the functional relationship between it and the central angle is: Δh is the maximum radius difference of the auxiliary ring; 3) Fix the chromatic confocal measurement system. Under no-load conditions, adjust the installation position and angle according to the wavelength information received by the two probes to ensure that there is no error in the information received by the two probes when the shaft rotates due to installation deviation. The specific method is to accurately rotate the shaft half a turn under no-load conditions to make the focal wavelength curves received by the two chromatic confocal probes equal or parallel. Repeat until the two focal wavelengths at the two positions are equal, which ensures that the rotation center line of the shaft and the optical axes of the two chromatic confocal probes are in the same plane, and the distance from the rotation center line of the shaft to the two probes is equal or has a fixed value. At this time, measure the displacement ΔL of the two light spots along the shaft at the initial position; 4) Obtain the wavelength λ i and the central angle relationship curve of the two chromatic confocal probes rotating one week under no-load conditions of the shaft, as shown in the appendix Figure 2 . According to the principle of the chromatic confocal technology, the focal wavelength λ i is proportional to the radial height h i after the installation of the auxiliary ring. Therefore, λ i = u(h i ) can be calculated and calibrated; and according to step (2), h i and have been designed as a proportional function. Therefore, there is: k is a constant; 5) Perform measurements and calculations. When the shaft is subjected to a load torque, torsional deformation occurs. At this time, the function curve of the focal wavelength and the central angle (the central angle at this time can be considered as the sum of the original central angle and the torsional angle) deviates, and the degree of deviation is different. As Figure 2 shown, according to steps (2) and (3), the following relationship can be analyzed: Therefore, according to the torque calculation formula, it can be known that: Among them, I p is the moment of inertia of the cross-section, D is the shaft diameter, G is the shear modulus of elasticity of the shaft, v is the correction coefficient, which can be calibrated and corrected, and Δλ is the wavelength difference obtained by two chromatic confocal sensing modules. 6) For the online measurement mode, the eccentric rotation, vibration, and uneven rotation speed of the shaft will cause measurement errors. It can be corrected according to the characteristics of the periodicity of the shaft rotation, the speed-time curve, and the focal wavelength-time curve. According to the wavelength-time curve, the rotation speed and the characteristics of the torsional vibration of the shaft can be obtained. According to the focal wavelength-time curve, the angular acceleration can be obtained and the torque measurement error can be corrected. The calculation method of the angular acceleration β is: Among them, m represents the serial number of the rotation cycle, is the average value of the relative torsional angle of this cycle, is the average value of the focal reflection wavelength difference of the m-th cycle.

[0016] Taking aluminum alloy 6061, 45# steel, POM, and 8200Pro resin materials as examples, the feasibility of this method and the theoretical measurement accuracy are further calculated and illustrated. Table 1. Physical parameters of the test shaft The axial chromatic resolution of the used chromatic confocal lens is 100 nm. Select a radius encoding ring HCR with a maximum radius difference of 2 mm. The axial installation distance between the two light spots is 60 mm. The shaft diameter is 18 mm and the length is 120 mm. Then, the theoretical measurement accuracy calculated according to formula (2) is as follows.

[0017] According to the attachment Figure 3 (a) Calculation results and curves show that for 45# steel with a common shear modulus of 76.92 GPa, when the torque changes by 0.0043 N·m, it can be resolved by a chromatic confocal sensor with an axial resolution of 100 nm. That is, the theoretical measurement resolution of this measurement device for 45# steel is 0.0043 N·m; according to the calculation principle and attachment Figure 3(b) It can be seen that the smaller the shear modulus, the higher the measurement resolution. For the 8200Pro material with a shear elastic modulus of 0.915 GPa, the theoretical measurement resolution of the system reaches 4.93 mN·m.

[0018] Taking 8200Pro as an example, the actual measurement results are as follows, where the reference torque is the measured value of a commercial torque sensor installed on the shaft. Table 2. Actual test data of the shaft of 8200Pro material (G = 915 Mpa)

[0019] According to the appendix Figure 4 (a) From the measurement results shown, during static measurement, there is a deviation between the measured torque value and the reference value, but the deviation basically remains a small constant value, which may be caused by calibration and installation errors. This method is effective; according to the appendix Figure 4 (b) From the measurement results, during online measurement, the measurement is stable, and the curves of the measured values of the two probes always maintain a stable delay, which is caused by the twist angle and can be further calibrated and calculated to obtain accurate real-time torque.

[0020] Compared with existing non-contact technologies, the present invention uses the chromatic confocal technology and the radius-encoded auxiliary ring to establish a non-contact torque measurement mathematical model. According to the linear relationship between the focal reflection wavelength and the twist angle, the measurement accuracy, application range, and reliability are significantly improved; at the same time, an integrated dual-probe chromatic confocal module is adopted, saving installation space and reducing the calibration and measurement difficulty. Compared with the commonly used coupling strain gauge torque sensor, this method avoids installing the sensor on the shaft, which can increase the shaft stiffness and rotation accuracy; compared with other non-contact torque measurement schemes, a split-beam integrated dual-probe chromatic confocal module is adopted, saving light sources, reducing the influence of aberration and background noise, and enhancing the consistency of the beam parameters of the two probes. Based on the chromatic confocal technology, light sources of different bands can also be adapted, and the light output aperture and focal distance can be changed, etc., improving the measurement accuracy and environmental adaptability. For miniaturized precision machinery, the optical-based non-contact measurement method can also use fiber-optic and metalens integration to achieve miniaturized torque measurement. In summary, the present invention proposes a brand-new non-contact torque measurement system and detection method for the field of torque non-contact measurement, which has broad application prospects in the torque measurement and control fields of precision mechanical spindles (machine tools, intelligent driving vehicles, traction motor shafts, etc.).

[0021] The above content is only to illustrate the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A non-contact torque measurement device integrated with a co-collimated bichromatic dispersion lens and a corresponding multi-parameter real-time high-precision measurement and calculation method for torque, torsional angle, and angular acceleration based on wavelength difference. Among them, A non-contact torque measurement device integrated with a collinear bichromatic dispersion lens, characterized by comprising an integrated collinear bichromatic dispersion confocal sensing module (13), a controller (1) integrating a light source, a spectral demodulation, and a torque calculation module, and two radius coding auxiliary rings (11)(12) for assisting in the calculation of the twist angle; a torque measurement calculation method based on bichromatic dispersion confocal demodulation, characterized in that based on the optical wavelength λ received by the bichromatic dispersion confocal sensing module i , the wavelength difference Δλ, and the physical parameters of the measured shaft (density ρ, shear modulus G, shaft diameter D), calculate its twist angle γ and torque T, calculate the real-time rotational speed n, angular acceleration, and vibration characteristics according to the rotation periodicity of the auxiliary ring, and can realize static measurement and on-line real-time measurement.

2. The co-collimated two-dispersion confocal sensing module (13) according to claim 1, wherein It is integrally packaged by an optical fiber coupler (3)(9), a beam splitting prism (6)(8) with a beam splitting ratio of 50% and 100%, a collimating lens group (5) and a dispersion mirror group (7).

3. The non-contact torque measurement device integrated with a co-collimated bichromatic dispersion lens according to claim 1, further characterized in that, The two dispersion mirror groups are axially dispersive and share a collimating lens and a confocal aperture, and the three are in a conjugate relationship with each other.

4. The radius coding auxiliary rings (11)(12) according to claim 1, characterized in that, Made of lightweight reflective materials, it is installed at the position where the two light spots on the measured shaft are focused during measurement, with a distance of ΔL between them; it is further characterized in that after being installed on the shaft, there is no relative sliding or deformation with the shaft, and the radial thickness h changes linearly with the swept circumferential angle gradually changes, that is the maximum thickness does not exceed the focal depth Δf of the focusing lens; it is further characterized by the flexible adjustment of the installation angles of the two auxiliary rings, which can adapt to the shaft torque measurement under different force conditions. For a single-end fixed shaft, it can be installed reversely, and for a shaft with forces at both ends, it is installed in the same direction to increase the measurement sensitivity.

5. A torque measurement and calculation method based on chromatic confocal demodulation according to claim 1, further characterized in that It includes the following steps: (1) Obtain the physical parameters of the shaft (shear modulus G, shaft diameter D, axial spacing ΔL between the light spots of the two confocal probes); (2) Install two measurement auxiliary rings according to the working distance, focal depth, and axial force working conditions of the dispersion lens, calculate and calibrate the radial height after their installation positions, and obtain the functional relationship between it and the central angle as follows: Δh is the maximum difference between the inner and outer radii of the auxiliary ring in the radial direction; (3) Fix the dispersion confocal measurement system, adjust the installation position and angle according to the change of the focal wavelength received by the two probes under no-load conditions, and complete the static calibration; (4) Complete the calibration of the relationship between the wavelength λ and the central angle when the two-dispersion confocal probe rotates one week under no-load condition on the axis, as shown in Figure 2 of the attached drawings; i and the central angle as shown in the attached drawing 2; (5) Conduct measurement and calculation, including static torque measurement and on-line torque measurement, and analyze the following relationship according to the principle of dispersion confocal technology and geometric relationship: Furthermore, according to the torque calculation formula, it can be known that: Where, I p is the moment of inertia of the cross-section, D is the shaft diameter, G is the shear modulus of elasticity of the shaft, k is the linear correction coefficient which can be corrected by calibration, and Δλ is the wavelength difference obtained by two chromatic confocal sensing modules; 6. The real-time rotational speed and angular acceleration measurement method according to claim 1, characterized in that Based on the static measurement, calculate and correct according to the characteristics of the time periodicity of shaft rotation, the rotational speed-time curve, and the focal wavelength-time curve, and the angular acceleration can be obtained and the torque measurement error can be corrected. The calculation method of the angular acceleration β is: where m represents the serial number of the revolution cycle, is the average value of the relative twist angle of this cycle, is the average value of the focal reflection wavelength difference of the m-th cycle.

Images