A method for measuring the speed of rotating parts based on proximity switches

Abstract

A method for measuring the speed of rotating components based on proximity switches is described. A stopper is fixed to the rotating component, and the proximity switch is attached to the exterior of the rotating component and connected to a programmable logic controller (PLC) via an input module. As the rotating component rotates, the stopper periodically approaches the proximity switch, generating alternating 0 / 1 signals for the PLC. A speed measurement program is written into the PLC. During speed measurement, the program performs the following steps: S1: Counts the number of revolutions of the rotating component using the 0 / 1 signals; S2: Filters the counted value using a filtering formula; and S3: Determines the rotating component's rotational speed using an approximate derivative formula. This speed measurement algorithm accurately measures the rotating component's speed without requiring a high-speed counter module, utilizing a proximity switch and a flexibly configurable stopper. This algorithm eliminates the need for expensive encoders or high-speed counter modules, significantly reducing costs. Furthermore, the stopper can be flexibly configured, offering advantages such as strong environmental adaptability, stable performance, and fast frequency response.

Description

Technical Field

[0001] The present invention relates to the field of detection and control technology, and in particular to a method for measuring the speed of a rotating component based on a proximity switch. Background Art

[0002] Encoders are commonly used on industrial equipment to accurately measure the speed of rotating equipment. However, in some applications where encoders are not available, or where the speed measurement accuracy requirements are not high, a speed measurement device with a small size, low cost, simple installation, and low hardware requirements is needed.

[0003] Proximity switches [1] are widely used in industrial control systems due to their small size, low cost, and simple installation. Many engineers and technicians have combined mechanical structures with electrical control systems to develop a series of speed meters based on proximity switches. Reference [2] discloses a ring with n notches that rotates along the output shaft of a reducer. The control system records the number of pulses per unit time, thereby calculating the speed of the output end of the reducer. However, due to the scanning cycle of the PLC controller, when the speed of the measured object is high, some pulse signals may be lost, thereby affecting the measurement accuracy of the device. Reference [3] uses a proximity switch to sense the speed measuring gear and connects the signal to the Mitsubishi PLC high-speed counter module to achieve redundant measurement of the speed of the hydro-generator. However, this method requires the use of a high-speed counter port, and ordinary I / O modules have certain limitations.

[0004] Therefore, the above-mentioned device and method need to be improved.

[0005] The documents cited in the present invention are as follows:

[0006] [1] Deng Zhongyi, Principle and Application of Proximity Switches[J], Automation Expo, 2003(05):35-38;

[0007] [2] Yang Chaowu, Bao Yongchao, Li Wen, Design of a new type of proximity switch speed meter [J], Heavy Machinery, 2018(02):43-45;

[0008] [3] Wang Zihao, Wang Xiaogang, Application of proximity switch in frequency measurement of hydro-generator based on PLC control [J], Small Hydropower, 2020(03):47-49. Summary of the Invention

[0009] In order to overcome the shortcomings of the background technology, the present invention discloses a method for measuring the speed of a rotating component based on a proximity switch, the purpose of which is to:

[0010] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0011] A method for measuring the speed of a rotating component based on a proximity switch is described. A stopper is fixed to the rotating component, and the proximity switch is fixed to the outside of the rotating component and connected to a programmable logic controller (PLC) via an input module. As the rotating component rotates, the stopper periodically approaches the proximity switch, causing the PLC to receive alternating 0 / 1 signals. A speed measurement program is written into the PLC. During speed measurement, the program performs the following steps:

[0012] S1: Counts the number of revolutions of the rotating part through 0 / 1 signals;

[0013] S2: Filter the count value using the filtering formula (1);

[0014]

[0015] Where, is the sampling time, is the sampling time of the previous moment, is the count value received by the filter at the moment, is the count value after filtering at the moment, is the program scan cycle, and is the set filtering time;

[0016] S3: The speed nk of the rotating part at the moment is obtained by formula (2);

[0017] n k =(1 / T s )×[C f (k)-C f (k-1)]. (2)

[0018] To further improve the technical solution, the rotating component is a shaft component, and the stopper is a semicircular or semi-annular stopper, which is fixed on the end face or outer cylindrical surface of the shaft component.

[0019] To further improve the technical solution, the stopper and the rotating component are fixedly connected separately or integrally formed.

[0020] To further improve the technical solution, the linear velocity Vk of the shaft component is:

[0021]

[0022] Where d is the diameter of the shaft component.

[0023] To further improve the technical solution, the stroke S of the shaft component is:

[0024]

[0025] To further improve the technical solution, when the block approaches the proximity switch, the proximity switch receives an induction signal, and the input signal received by the PLC is 1; when the block moves away from the proximity switch, the proximity switch does not receive an induction signal, and the input signal received by the PLC is 0.

[0026] To further improve the technical solution, the speed measurement program includes a speed measurement program module f, which contains the calculation program of formulas (1) and (2); assuming that the speed of the rotating part is n, then:

[0027] n=f(In,T s ,T f ) (5)

[0028] Where, is a 0 / 1 signal.

[0029] To further improve the technical solution, the speed measurement program module f also contains a counter, which increases by 1 when the counter rises.

[0030] Further improve the technical solution, repeatedly call the speed measurement program module f, and obtain the speed n of the rotating part at the rising edge of In respectively p , and the speed n of the rotating part at the falling edge of In N , then the speed n p and speed n N Find the average value and get the speed n of the rotating part.

[0031] Due to the adoption of the above technical solution, this speed measurement algorithm has the following beneficial effects:

[0032] This speed measurement algorithm uses proximity switches and flexibly configurable blocks to accurately measure the speed of rotating parts without using a high-speed counter module.

[0033] Compared with existing technologies, this speed measurement algorithm does not require expensive encoders or high-speed counter modules, significantly reducing costs. Furthermore, the stopper can be flexibly configured, offering advantages such as strong environmental adaptability, stable performance, fast frequency response, and long service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The figure shows a schematic diagram of an installation form of a stopper on a shaft component.

[0035] Figure 2 Shown is a schematic diagram of another installation form of the stopper on a shaft component.

[0036] Figure 3 Shown is a comparison chart of the speed measurement curves of various speed measurement devices.

[0037] In the figure: 1. Stop block; 2. Shaft components; 3. Proximity switch; 4. Encoder speed measurement curve; 5. Laser speed measurement curve; 6. Proximity switch speed measurement curve. DETAILED DESCRIPTION

[0038] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention. It should be noted that in the description of the present invention, the terms "front", "rear", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be understood as a limitation of the present invention. It should also be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, an indirect connection through an intermediate medium, or a communication between two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0039] Example 1:

[0040] The invention discloses a rotating component speed measurement method based on a proximity switch, which is used for measuring the speed of a shaft-type rotating component.

[0041] Figure 1 The figure shows a schematic diagram of a mounting arrangement of a stopper 1 on a shaft-like component 22. In this embodiment, the rotating component is a shaft-like component 22 having a rotational characteristic. Specifically, the shaft-like component 22 is a roller having a diameter of 240 mm. The stopper 1 is a semi-annular stopper 1, which is fixed to the end face of the shaft-like component 22 by screws. The proximity switch 3 is fixed to the exterior of the shaft-like component 22 and is disposed opposite the stopper 1. It is worth noting that the stopper 1 may also be semicircular.

[0042] Figure 2 FIG. 1 shows another schematic diagram of the installation of the stopper 1 on the shaft component 22. Figure 2 As can be seen, the stopper 1 can also be positioned on the outer circumferential surface of the shaft component 22, and the proximity switch 3 can be oriented circumferentially or axially toward the stopper 1. The specific placement of the stopper 1 depends on the structure of the shaft component 22 and the operating environment. Similarly, the stopper 1 can be fixedly connected to the rotating component by bolts or bonding, or the stopper 1 structure can be integrally machined onto the rotating component.

[0043] Proximity switches, also known as contactless proximity switches, are ideal electronic switching sensors. When a metal object enters the sensing zone, they quickly and contactlessly trigger a command, accurately reflecting the object's position and travel. In automated control systems, proximity switches can be used as limit, counting, and positioning control components.

[0044] According to the type, proximity switches 3 can be divided into inductive, capacitive, Hall effect, and AC / DC types. Proximity switches 3 have the characteristics of stable performance, fast frequency response, long service life, strong anti-interference ability, and good waterproof, shockproof, and corrosion-resistant properties.

[0045] Proximity switch 3 is connected to the PLC via an input module. Proximity switch 3 has a counting function. In this embodiment, when block 1 enters the sensing zone of proximity switch 3, a rising edge is triggered, at which point proximity switch 3 inputs a signal of 1 to the PLC via the input module. When block 1 is about to leave the sensing zone of proximity switch 3, a falling edge is triggered, at which point proximity switch 3 inputs a signal of 0 to the PLC via the input module. Thus, as shaft component 22 rotates, the PLC receives a series of alternating 0 / 1 signals, also known as pulse signals.

[0046] It is worth noting that when the stopper 1 just enters the sensing area of ​​the proximity switch 3, a rising edge is triggered, and the input signal can also be 0 at this time; when the stopper 1 is about to leave the sensing area of ​​the proximity switch 3, a falling edge is triggered, and the input signal can also be 1 at this time. Although the 0 / 1 signals obtained by the PLC are inverted, this does not affect the measurement of the rotational speed of the shaft component 22.

[0047] A speed measurement program is written into the PLC. When measuring speed, the speed measurement program performs the following steps:

[0048] S1: Counts the number of rotations of the rotating part through 0 / 1 signals.

[0049] The PLC scan cycle is 1000 / (2×n), measured in milliseconds (ms). This scan cycle ensures that even at the highest speed of the rotating component, the PLC can capture the 0 / 1 signal of proximity switch 3 in each scan cycle without losing the signal.

[0050] Each time the rotating part rotates one circle, the proximity switch 3 triggers a rising edge, and the count value at this time increases by 1. According to the differential principle, the speed of the rotating part can be obtained by calculating the rate of change of the count value.

[0051] S2: Filter the count value using the filtering formula (1).

[0052]

[0053] In the formula, k represents the sampling time, k-1 represents the sampling time of the previous moment, C(k) represents the count value received by the filter at moment k, and C f (k) is the count value after filtering at time k, T s is the program scan cycle, T f The filter time is set.

[0054] Without using the PLC interrupt function or high-speed counter module, there will be varying degrees of lag when the PLC reads external input signals, which will affect the rate of change of the count value, resulting in varying degrees of fluctuation. This fluctuation is also called noise and can seriously affect the accuracy of speed measurement.

[0055] Filtering the count value can make the change of the count value smoother, which is beneficial to reducing the fluctuation amplitude of the speed obtained by derivative.

[0056] S3: Since the data collected by PLC is a series of discrete quantities, the speed n of the rotating part at time k can only be obtained by approximate derivation formula (2): k .

[0057] n k =(1 / T s )×[C f (k)-C f (k-1)] (2)

[0058] Furthermore, for a shaft component 22 with a diameter of d, the linear velocity v of its outer surface is k for:

[0059]

[0060] Furthermore, the rotation stroke S of the outer surface of the shaft component 22 is:

[0061]

[0062] In order to verify the speed measurement accuracy of this speed measuring device, this test device, laser speed measuring device and encoder were installed on the same roller, and a comparative test was carried out. Figure 3 The figure shows the comparison of the speed curves of various speed measuring devices. Figure 3It can be seen that laser speed measurement curve 5 (shown by the dotted line) has the highest mean, encoder speed measurement curve 4 (shown by the continuous solid line) has a mean in the middle, and the proximity switch speed measurement curve 6 (shown by the dashed line) has the lowest mean. It can also be seen that encoder speed measurement curve 4 has the smallest amplitude fluctuation, laser speed measurement curve 5 has a mean amplitude fluctuation, and proximity switch speed measurement curve 6 has the largest amplitude fluctuation. However, based on the mean of encoder speed measurement curve 4, the relative error of proximity switch speed measurement curve 6 is within 0.8%. For industrial applications with low speed measurement accuracy requirements, such as machine tools and equipment where speed accuracy is only required to be in revolutions per minute (rpm), this error is well within the acceptable range.

[0063] As can be seen from the above, this speed measurement algorithm achieves accurate speed measurement of rotating components by utilizing proximity switches 3 and a flexibly configurable stopper 1, without requiring a high-speed counter module. Compared to existing technologies, this speed measurement algorithm eliminates the need for expensive encoders or high-speed counter modules, significantly reducing costs. Furthermore, the stopper 1 can be flexibly configured, offering advantages such as strong environmental adaptability, stable performance, fast frequency response, and a long service life.

[0064] Example 2:

[0065] In this embodiment, the speed measurement program includes a speed measurement program module f, which includes a counter that increases by 1 when In rises. The speed measurement program module f also includes the calculation program of formulas (1) and (2). Assuming the speed of the rotating part is n, then:

[0066] n=f(In,T s ,T f ) (5)

[0067] Where, is a 0 / 1 signal.

[0068] In this way, the speed of the rotating part can be directly obtained through the speed measurement program module f.

[0069] In order to further improve the speed measurement accuracy, the PLC calls the speed measurement program module f twice every time the rotating part rotates one circle, so as to obtain the speed n of the rotating part at the rising edge of In. p , and the speed n of the rotating part at the falling edge of In N , then the speed n p and speed n N Find the average value and get the speed n of the rotating part. Obviously, for the speed n p and speed n N Taking the average value can eliminate random interference and improve the speed measurement accuracy.

[0070] Parts not described in detail are prior art. Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for measuring the speed of a rotating component based on a proximity switch, characterized by: A stopper is fixed to the rotating component, and a proximity switch is fixed to the outside of the rotating component and connected to the PLC through an input module. When the rotating component rotates, the stopper periodically approaches the proximity switch, causing the PLC to receive alternating 0 / 1 signals. A speed measurement program is written into the PLC. When measuring speed, the speed measurement program performs the following steps: S1: Counts the number of revolutions of the rotating part through 0 / 1 signals; S2: Filter the count value using the filtering formula (1); Where k is the sampling time, k-1 is the sampling time of the previous moment, C(k) is the count value received by the filter at moment k, and C f (k) is the count value after filtering at time k, T s is the program scan cycle, T f is the set filter time; S3: The speed n of the rotating part at time k is obtained from formula (2) k ; n k =(1 / T s )×[C f (k)-C f (k-1)] (2)。 2. The method for measuring the speed of a rotating component based on a proximity switch according to claim 1, wherein: The rotating component is a shaft component, and the stopper is a semicircular or semi-annular stopper, which is fixed on the end face or outer circular surface of the shaft component.

3. The method for measuring the speed of a rotating component based on a proximity switch according to claim 1 or 2, wherein: The stopper is fixedly connected to the rotating component separately or integrally formed.

4. The method for measuring the speed of a rotating component based on a proximity switch according to claim 2, wherein: The linear velocity V of the shaft component k for: Where d is the diameter of the shaft component.

5. The method for measuring the speed of a rotating component based on a proximity switch according to claim 1, wherein: When the block approaches the proximity switch, the proximity switch receives an induction signal, and the input signal received by the PLC is 1. When the block is away from the proximity switch, the proximity switch does not receive any sensing signal, and the input signal received by the PLC is 0.

6. The method for measuring the speed of a rotating component based on a proximity switch according to claim 1, wherein: The speed measurement program includes a speed measurement program module f, which contains the calculation program of formulas (1) and (2). Assuming the speed of the rotating part is n, then: n=f(In,T s ,T f ) (5) Where In is a 0 / 1 signal.

7. The method for measuring the speed of a rotating component based on a proximity switch according to claim 6, wherein: The speed measurement program module f also contains a counter, which is incremented by 1 when In rises.

8. The method for measuring the speed of a rotating component based on a proximity switch according to claim 7, wherein: Repeatedly call the speed measurement program module f to obtain the speed n of the rotating part at the rising edge of In p , and the speed n of the rotating part at the falling edge of In N , then the speed n p and speed n N Find the average value and get the speed n of the rotating part.

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