Tachometer based on optics and measuring method thereof
By using an optical laser emitter and optical signal receiver, combined with a dual-channel optical signal cross-checking module, the problem of electromagnetic interference inside and outside the magnetic field in traditional tachometers is solved, enabling more accurate speed measurement and multi-channel signal acquisition, and improving the availability and data stability of the equipment.
Patent Information
- Application Number
- CN202511328983.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-17
- Publication Date
- 2026-01-16
AI Technical Summary
Traditional electromagnetic induction tachometers cannot effectively suppress electromagnetic interference inside and outside the magnetic field, resulting in inaccurate speed measurement and the inability to simultaneously acquire multiple signals.
An optical method is used, in which a laser transmitter and an optical signal receiver are connected by optical fiber. The optical signal receiver is located below the laser transmitter and its outer surface is black. A dual-channel optical signal cross-checking module is used for signal processing to achieve stable transmission of optical signals and suppress interference.
It effectively suppresses electromagnetic interference inside and outside the magnetic field, provides more accurate speed measurement results, and can simultaneously calculate multiple signals online, improving the availability and data stability of the equipment.
Smart Images
Figure CN121347844A_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of rotational speed measurement technology, and particularly relates to an optical-based tachometer and its measurement method. Background Technology
[0002] During the production and operation of large rotating equipment, it is necessary to accurately identify its rotational speed in order to accurately assess the equipment's operating performance. To achieve precise acquisition of rotational speed signals, the rotational speed monitoring sensor must be resistant to electromagnetic interference to meet the requirements of shielding against complex electromagnetic fields and enabling low-loss transmission over long distances.
[0003] Traditional tachometers often use the principle of electromagnetic induction for monitoring, employing a metal shielding layer to suppress the spread of ineffective magnetic fields. However, this can lead to unintentional cutting of magnetic field lines by metal objects, resulting in deviations in speed measurement. External electromagnetic interference can also amplify or cancel pulse signals, causing instantaneous changes in the number of effective pulses. This often requires adjusting the pulse signal judgment threshold based on experience.
[0004] Both of the above methods have limitations in application. The metal shielding layer can only suppress random electromagnetic pulses generated by metal burrs outside the effective monitoring magnetic field, but it has no effect on metal burrs inside the effective monitoring magnetic field; the empirical threshold has a certain suppressive effect on electromagnetic pulses of different amplitudes inside the magnetic field and at the protruding end of the rotating shaft, but it cannot suppress external electromagnetic interference that is at the same frequency or deviates from the pulse quantity.
[0005] Therefore, the aforementioned traditional methods cannot effectively monitor and suppress random electromagnetic pulses both inside and outside the magnetic field. Summary of the Invention
[0006] The purpose of this application is to provide an optical tachometer and its measurement method, which solves the problems of traditional electromagnetic pulse principle tachometers being susceptible to strong electromagnetic interference, metal burr interference, and pulse intensity threshold relying on empirical human interference.
[0007] To achieve the above objectives, this application provides the following technical solution:
[0008] In a first aspect, this application provides an optical tachometer, including a laser emitter, an optical signal receiving device, and a photoelectric signal conversion component. The optical signal receiving device and the photoelectric signal conversion component are connected by an optical fiber. The laser emitter is located below the optical signal receiving device and is arranged towards the gear, continuously incidenting laser light onto the surface of the gear.
[0009] As one possible implementation, the number of optical signal receiving devices is 2.
[0010] As one possible approach, the two optical signal receiving devices are arranged vertically, one above the other.
[0011] As one possible approach, the optical signal receiving device and the laser transmitter are arranged on the same vertical line.
[0012] As one possible implementation, the vertical heights of the optical signal receiving point of the optical signal receiving device and the laser output point of the laser transmitter satisfy the following:
[0013] The vertical heights H1 and H2 between the optical signal receiving points of the two optical signal receiving devices and the laser output point of the laser transmitter satisfy the following relationships:
[0014] H1 = 2 * L1 * tanθ;
[0015] H2 = 2 * L2 * tanθ;
[0016] In the formula, L1 and L2 are the horizontal distances between the optical signal receiving points of the two optical signal receiving devices and the convex and concave surfaces of the gear, respectively, and θ is the angle between the laser and the horizontal plane of the gear.
[0017] As one possible implementation, the outer surface of the optical signal receiving device is black.
[0018] In one feasible manner, the optical signal receiving device and the laser transmitter are arranged on the upper and lower sides of the gear, and the laser is blocked or propagated between the teeth when the gear rotates, generating a square wave optical signal that is collected and propagated through the optical fiber.
[0019] Secondly, this application provides an optical-based method for measuring rotational speed, comprising:
[0020] Step 1: The laser is continuously incident onto the surface of the gear on the rotating shaft through the laser emitter. The scanning signal light in the field is reflected by the smooth surface of the rotating shaft and enters the optical signal receiving device.
[0021] Step 2: The optical signal receiving device focuses the signal beam and sends it through an optical fiber to the photoelectric signal conversion component;
[0022] Step 3: The photoelectric signal conversion component analyzes the light intensity information into a 0-1 signal square wave, and performs a self-test by comparing the two sets of photoelectric signal square waves in a complementary manner;
[0023] Step 4: Calculate the instantaneous frequency of the square wave and combine it with the number of gear teeth to output a digital signal of the shaft rotation speed.
[0024] As an feasible approach, by testing the modulated light source to ensure that its input optical power is within the nominal sensitivity range, the optical power of the laser emitter is adjusted, the light enters the optical signal receiving device and is transmitted in the optical fiber, and the angle between the signal light of the optical field and the perpendicular line of the rotation axis satisfies the arrangement position of the optical signal receiving device.
[0025] As an feasible approach, two sets of photoelectric signal square waves are used for signal mutual detection, and transient interference is suppressed by dual-channel signals.
[0026] Compared with the prior art, the optical-based tachometer and its measurement method provided in this application have the following advantages:
[0027] Beneficial effects:
[0028] (1) Traditional electromagnetic induction tachometers typically use a metal shielding layer to suppress the diffusion of ineffective magnetic fields from the magnet. However, the metal shielding only works on moving metal objects outside the suppression angle and cannot eliminate irregular metal objects such as metal burrs within the tachometer's magnetic field. This application uses an optical signal component to determine the number of convex and concave parts of the gear, and the optical signal receiving device uses black shielding to block stray light interference from other directions, which can effectively suppress external interference. Furthermore, the uniqueness of the optical path can also solve the interference caused by irregular objects obstructing the optical field.
[0029] (2) Traditional electromagnetic induction tachometers require empirically determined thresholds to judge the effectiveness of electromagnetic pulses. Moreover, complex external electromagnetic environments, such as the 50Hz voltage signal from power cables, often amplify or cancel the pulse voltage signal of the tachometer, causing instantaneous changes in the number of effective pulses. This can easily lead to other interlocking logic accidents, which cannot be effectively investigated and resolved in a short time. The theory of this application uses an optical system for signal acquisition and transmission, which is almost unaffected by electromagnetic interference.
[0030] (3) Traditional electromagnetic induction principle tachometers can only add delay filtering function, and data accuracy, stability and response cannot be satisfied at the same time. The redundant cross-checking module of dual optical signals in this application can suppress the influence of instantaneous signal interference and provide more accurate measurement data.
[0031] (4) Traditional tachometers cannot collect multiple signals simultaneously. To ensure redundancy, multiple units must be installed. Due to gear burrs and electromagnetic interference, no matter how many hot spare parts are added, accurate signal acquisition is impossible. The dual-group optical signal receiving device of this application performs calculations and self-tests online simultaneously, which can effectively reduce the number of devices installed and ensure the availability of the equipment. At the same time, the design of a multi-level tooth depth structure of the gear, matched with the optical signal receiving device on the corresponding level optical path, can realize the simultaneous acquisition of multiple signals, greatly improving its data stability and availability. Attached Figure Description
[0032] To more clearly illustrate the technical solution of this application, the accompanying drawings used in the technical description will be briefly introduced below.
[0033] Figure 1 A schematic diagram of the optical-based tachometer provided in this application;
[0034] Figure 2 for Figure 1 A magnified view of a portion of the image;
[0035] Figure 3 A flowchart of the optical-based rotational speed measurement method provided in this application.
[0036] Explanation of reference numerals in the attached figures:
[0037] 1. Laser transmitter; 2. Optical signal receiver; 3. Photoelectric signal conversion component; 4. Gear; 5. Optical fiber. Detailed Implementation
[0038] The following detailed description provides further details on specific implementation methods.
[0039] like Figure 1 and Figure 2 As shown, this application provides an optical-based tachometer, including a laser emitter 1, an optical signal receiving device 2, a photoelectric signal conversion component 3, a gear 4, and an optical fiber 5. The optical signal receiving device 2 and the photoelectric signal conversion component 3 are connected via the optical fiber 5, and the laser emitter 1 is arranged vertically directly below the optical signal receiving device 2. There are two optical signal receiving devices 2, arranged vertically.
[0040] Laser emitter 1 is positioned facing gear 4. Laser emitter 1 continuously incidents laser light onto the surface of the regular gear 4 on the rotating shaft. The scanning signal light in the field is first reflected by the smooth surface of the rotating shaft and enters the optical signal receiving device 2. The optical signal receiving device 2 focuses the signal light and reaches the photoelectric signal conversion component 3 through the internal optical fiber 5. The photoelectric signal conversion component 3 interprets the light intensity information into a 0-1 signal square wave. By performing complementary comparison and self-check on the two sets of photoelectric signal square waves, the instantaneous frequency of the square wave is calculated, and combined with the number of gear teeth, the digital signal of the rotating shaft speed is output.
[0041] Laser emitter 1 is an optical system. By testing, the light source can be modulated so that its input light power is near the nominal sensitivity. The light power of the scanning signal light adapted to laser emitter 1 is adjusted so that the signal light can be reflected on the smooth surface of the rotating shaft gear. The light can enter the optical signal receiving device 2 and be successfully transmitted in the optical fiber 5. The angle between the signal light of the light field and the perpendicular line of the rotating shaft should meet the arrangement position of the optical signal receiving device 2.
[0042] Two optical signal receivers 2 are located on the same vertical line as the laser transmitter 1. The outer surface of the optical signal receivers 2 is black, which can effectively suppress stray light illuminating their surface. The height of the two optical signal receivers 2 is adjustable and can be fixed to ensure that the light reflected from the uneven surface of their matching gears is at different horizontal heights.
[0043] This application uses two sets of photoelectric signal square waves for signal mutual detection. The dual-channel signal can suppress transient interference and provide stable output. In the event of a single failure, the other can serve as a hot spare to acquire and output signals.
[0044] The horizontal distances between the receiving surfaces of the two optical signal receiving devices 2 and the convex and concave surfaces of gear 4 are L1 and L2, respectively. The angle between the laser and the horizontal plane of gear 4 (see details) Figure 2 ).
[0045] The vertical heights H1 and H2 between the optical signal receiving points of the two optical signal receiving devices 2 and the laser output point of the laser transmitter 1 satisfy the following relationships:
[0046] H1 = 2 * L1 * tanθ
[0047] H2=2*L2*tanθ
[0048] For example, the horizontal distances between the receiving surfaces of the two optical signal receiving devices 2 and the convex and concave surfaces of the gear 4 are 50 mm and 70 mm, respectively; the angle between the signal light and the vertical line of the rotating shaft is 45°.
[0049] The vertical heights H1 and H2 between the optical signal receiving points of the two optical signal receiving devices 2 and the signal light output point of the laser transmitter 1 satisfy the following relationships:
[0050] H1 = 2 * 50 * tan45° = 100 mm
[0051] H2 = 2 * 70 * tan45° = 140 mm
[0052] The laser transmitter 1 and the optical signal receiving device 2 can also be located on the upper and lower sides of the gear 4. The laser is intermittently reflected by the convex and concave surfaces of the gear 4 as it rotates to the two optical signal receiving devices 2, generating two sets of square wave optical signals that are collected and propagated through two sets of optical fibers 5.
[0053] The photoelectric signal conversion component 3 can convert the optical signals received in the two sets of optical fibers 5 into electrical signals. It has built-in electrical signal square wave frequency calculation module and two sets of photoelectric signal square wave complementary comparison self-test module to realize functions such as speed calculation and instantaneous interference suppression.
[0054] This application provides a signal acquisition mode based on light reflection and signal transmission through optical fiber, offering more diverse methods for speed measurement.
[0055] In complex electromagnetic interference environments, the optical signal is almost unaffected, effectively overcoming the disadvantages of existing electromagnetic induction principle tachometers.
[0056] In addition, such as Figure 3As shown, based on the aforementioned optical-based tachometer, this application also provides an optical-based speed measurement method, comprising:
[0057] Step 1: Continuously incident the laser beam through laser emitter 1 (incident direction is the center of the gear, see details). Figure 2 The laser light is first reflected off the smooth surface of the gear 4 on the rotating shaft of the rotating equipment and then enters the optical signal receiving device 2.
[0058] Step 2: Two optical signal receiving devices focus the laser reflected from the convex and concave surfaces of the gear respectively, and the laser reaches the photoelectric signal conversion component 3 through the internal optical fiber 5;
[0059] Step 3: The photoelectric signal conversion component 3 analyzes the light intensity information collected by the two sets of optical fibers 5 into two sets of 0-1 signal square waves. The two sets of photoelectric signal square waves are compared and self-checked by complementary comparison (at any time, the values of the two sets of square waves are 0 and 1 respectively, and the sum of the values of the two sets of square waves is 1).
[0060] Step 4: Calculate the instantaneous frequency f of the square wave, and combine it with the number of gear teeth s to output the digital signal of the shaft rotation speed (n = f / s).
[0061] In step 1, the light source is tested and its input optical power is made to be near the nominal sensitivity. The optical power of the laser transmitter 1 is adjusted to match the laser. The signal light needs to be reflected on the smooth surface of the rotating gear. The light enters the optical signal receiving device 2 and is successfully transmitted in the optical fiber 5. The angle between the laser and the horizontal plane of the gear 4 should meet the arrangement position of the optical signal receiving device 2.
[0062] This application uses two sets of photoelectric signal square waves for signal mutual detection. The dual-channel signal can suppress transient interference and provide stable output. In the event of a single failure, the other can serve as a hot spare to acquire and output signals.
[0063] The horizontal distances between the receiving surface of the optical signal receiving device 2 and the concave and convex surfaces of the gear 4 are L1 and L2, respectively, and the angle between the signal ray and the perpendicular line of the rotating shaft is θ.
[0064] The vertical heights H1 and H2 between the optical signal receiving points of the two optical signal receiving devices 2 and the signal light output point of the laser transmitter 1 satisfy the following relationships:
[0065] H1 = 2 * L1 * tanθ
[0066] H2=2*L2*tanθ
[0067] The laser transmitter 1 and the optical signal receiver 2 are arranged on the upper and lower sides of the gear 4. The laser is intermittently reflected by the convex and concave surfaces of the gear 4 as it rotates to the two optical signal receivers 2, generating square wave optical signals that are collected and propagated through the optical fiber 5.
[0068] The above description is only a specific embodiment of this application, but the protection scope of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the protection scope of this application.
Claims
1. An optical-based tachometer, characterized by, The application relates to a laser signal receiving device, which comprises a laser emitter (1), a light signal receiving device (2) and a photoelectric signal conversion assembly (3), wherein the light signal receiving device (2) and the photoelectric signal conversion assembly (3) are connected through an optical fiber (5), the laser emitter (1) is arranged below the light signal receiving device (2), and the laser emitter (1) is arranged towards a gear (4) and continuously emits laser to the surface of the gear (4).
2. The optical-based tachometer of claim 1, wherein, The number of the light signal receiving devices (2) is two.
3. The optical-based tachometer of claim 2, wherein, The two light signal receiving devices (2) are vertically arranged.
4. The optical-based tachometer of claim 1, wherein, The light signal receiving device (2) and the laser emitter (1) are arranged on the same vertical line.
5. The optical-based tachometer of claim 1, wherein, The vertical heights H1 and H2 of the light signal receiving points of the two light signal receiving devices (2) and the laser output point of the laser emitter (1) satisfy the following conditions: H1 = 2*L1*tan theta; H2 = 2*L2*tan theta; In the formula, L1 and L2 are the horizontal distances between the light signal receiving points of the two light signal receiving devices (2) and the convex and concave surfaces of the gear (4) respectively, and theta is the included angle between the laser and the horizontal plane of the gear (4).
6. The optical-based tachometer of claim 1, wherein, The outer surface of the light signal receiving device (2) is black.
7. The optical-based tachometer of claim 1, wherein, The light signal receiving device (2) and the laser emitter (1) are arranged on the upper and lower sides of the gear (4), the laser is interrupted or propagated between the gear teeth when the gear rotates, and a square wave light signal is generated and collected and propagated through the optical fiber (5).
8. An optical-based rotational speed measurement method, characterized in that The application comprises the following steps: Step 1: continuously emitting laser to the surface of the gear (4) of a rotating shaft through the laser emitter (1), and reflecting the scanning signal light in the field into the light signal receiving device (2) through the smooth surface of the rotating shaft; Step 2: focusing the signal light in the light signal receiving device (2) and transmitting the signal light to the photoelectric signal conversion assembly (3) through the optical fiber (5); Step 3: converting the light intensity information into a 0-1 signal square wave through the photoelectric signal conversion assembly (3), and performing self-checking through complementary comparison of the two groups of photoelectric signal square waves; Step 4: calculating the instantaneous frequency of the square wave, and combining the gear tooth number to output a rotating shaft rotating speed digital signal.
9. The optical-based rotational speed measurement method according to claim 8, characterized in that, Through testing a modulated light source, adjusting the light power of the laser emitter (1), transmitting the light into the light signal receiving device (2) and the optical fiber (5), and making the included angle between the signal light of the light field and the vertical line of the rotating shaft meet the arrangement position of the light signal receiving device (2).
10. The optical-based rotational speed measurement method of claim 8, wherein, Two groups of photoelectric signal square waves are used for signal mutual checking, and instantaneous interference is suppressed through double-channel signals.