Vibration frequency sensor based on dynamic response of acceleration

Abstract

A vibration frequency sensor based on the dynamic response of acceleration belongs to the technical field of sensor design. The sensor is composed of an accelerometer, a mass block, a damper, and a spring; the accelerometer is used to collect the acceleration signal of the mass block in real time online, and the accelerometer and the mass block together constitute the effective load of the frequency sensor; the effective load, the damper and the spring constitute a typical single-degree-of-freedom mass-spring-damper system; the vibration frequency of the system is obtained online in real time using the proposed frequency estimation algorithm. The present invention is a vibration frequency identification sensor and method based on the response signal. The device is simple, low in cost, high in measurement efficiency and precision, and is suitable for full-band vibration frequency acquisition and measurement. Through the dynamic response of acceleration, real-time online frequency identification of simple harmonic external excitation can be achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of sensor design, and in particular relates to a vibration frequency sensor based on acceleration dynamic response, which can be used for real-time measurement and monitoring of the vibration frequency of a mechanical system. Background Art

[0002] Vibration is a common phenomenon in many industrial and technological fields. Frequency is one of the key elements of vibration. By measuring the vibration frequency of equipment or structures, its performance, safety and structural integrity can be evaluated in real time. For example, in the manufacturing industry, real-time monitoring of the vibration frequency of mechanical equipment can help predict and diagnose potential failures and performance degradation, thereby reducing downtime and repair costs. In construction and civil engineering, vibration frequency measurement is used to evaluate the stability and safety of bridges, buildings and other structures. In the energy sector, monitoring the vibration frequency of wind turbines and other power generation equipment helps optimize operating efficiency and prevent failures. In addition, through real-time monitoring of vibration frequency, technicians can immediately identify abnormal vibrations and respond quickly, taking effective measures to prevent possible damage and failures. This not only ensures the safety of personnel, but also ensures the efficiency of production and operations. Therefore, vibration frequency measurement and real-time monitoring play a vital role in the industrial and technological fields.

[0003] Vibration sensors are mainly divided into two categories, non-contact sensors and contact sensors. Non-contact sensors are mainly composed of capacitors, inductors and optical components. They are very effective but have some problems. For example, sensors based on electrical components have poor anti-electromagnetic interference capabilities, and sensors based on optical components are easily affected by factors such as surface roughness and air quality. In addition, non-contact sensor systems are relatively complex and costly. Contact sensors mainly use accelerometers or probes to measure the vibration of objects. Although they bring additional mass, the impact can be ignored and better results can be obtained. Compared with non-contact sensors, contact sensors are relatively simple and cost-effective. However, whether contact or non-contact, existing vibration sensors still have the following shortcomings that need to be solved: (1) Most existing vibration sensors measure the displacement, velocity or acceleration of the vibration of an object and cannot reflect the frequency information of the vibration; (2) The acquisition of environmental excitation frequency is mostly based on the measurement signal of the vibration sensor, and is converted offline using signal processing methods such as Fourier transform. Frequency identification takes a long time, is inefficient, and has a narrow applicable bandwidth, which cannot guarantee online real-time measurement and monitoring of environmental frequencies. Summary of the invention

[0004] The purpose of the present invention is to provide a vibration frequency identification sensor based on the dynamic response signal of acceleration, which has simple device, low cost, high measurement efficiency and high precision, in order to solve the problems that the vibration sensors widely existing in the current mechanical vibration field cannot directly reflect the vibration frequency information, and the existing frequency sensors take a long time to identify, have low efficiency, lack of online real-time performance and narrow applicable bandwidth. By using the acceleration signal of the object to be measured, the online real-time measurement and monitoring of the vibration frequency of the mechanical system can be realized.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A vibration frequency sensor based on dynamic response of acceleration, the sensor comprising an accelerometer, a mass block, a damper, a spring, and a housing;

[0007] The accelerometer is used to collect the acceleration signal of the mass block in real time online. The accelerometer and the mass block together constitute the effective load of the frequency sensor; the effective load, damping and spring constitute a single-degree-of-freedom mass-spring-damper system.

[0008] Furthermore, the working principle of the sensor is:

[0009] According to the theory of single-degree-of-freedom mass-spring-damper system in structural dynamics, the dynamic model of this vibration sensor is an ordinary differential equation.

[0010]

[0011] Where m is the mass of the effective load inside the frequency sensor, d is the differential sign, t is time, x is the displacement of the mass block, c is the damping inside the frequency sensor, k is the stiffness of the spring inside the frequency sensor, u(t) = u0 sin(ωt+φ) is the displacement expression of the measured system doing simple harmonic vibration, u0 is the displacement amplitude of the vibration, ω is the frequency to be measured, and φ is the phase difference of the vibration;

[0012] Differentiate equation (1) twice with respect to time, and we get

[0013]

[0014] make represents the acceleration of the payload, and substituting it into equation (2) yields

[0015]

[0016] Differentiate equation (3) twice with respect to time, and we get

[0017]

[0018] Multiply both sides of equation (3) by ω2 ,get

[0019]

[0020] Adding equations (4) and (5) yields

[0021]

[0022] Multiply both sides of formula (6) And integrate the time t four times. After partial integration, we can get

[0023]

[0024] Where t0≥0 represents the start time of frequency estimation, and r4 and p4 are expressed as follows:

[0025]

[0026] In the formula, r1, r2, r3, p1, p2 and p3 are all intermediate parameters;

[0027] From formula (7), we can see that only a small time interval Δ t The acceleration information in can be used to explicitly calculate the simple harmonic vibration frequency ω,

[0028]

[0029] In the formula, It represents the frequency collected by this frequency sensor, γ represents the filter gain, which is usually taken as 0.01, and e is the natural base.

[0030] So far, an explicit expression for vibration frequency identification based on acceleration signals has been given, that is, a vibration frequency sensor based on acceleration response has been developed to realize online real-time acquisition and measurement of simple harmonic vibration frequency.

[0031] Furthermore, t0 is an important parameter in the sensor. By real-time regulation of t0, it is possible to effectively cope with changes in the external excitation frequency. The frequency identification process is divided into two parts, the transient stage and the steady-state stage. t1 is defined as the duration of the transient stage, and the differential value d is the difference between the frequency estimate of the current step and the frequency estimate of the previous step divided by the step length. The sensor parameter D1 is a custom value. When the frequency estimate gradually converges, the differential value d gradually tends to 0. When d<D1, the identification changes from the transient stage to the steady-state stage. Similarly, the sensor parameter D2 is also a custom value. When the excitation frequency changes, the frequency estimate will change, and the differential value d will change from 0 or a value close to 0 to a larger mutation greater than D2. At this time, t0 is reselected as the current time, and the identification changes from the steady-state stage to the transient stage. The sensor parameters t1, D1 and D2 can be selected based on experience and the characteristics of the system under test.

[0032] The beneficial effects of the present invention compared to the prior art are as follows: the present invention is a vibration frequency identification sensor and method based on the response signal. The device is simple, low-cost, high-efficiency and high-precision in measurement, and is suitable for full-band vibration frequency acquisition and measurement. Through the dynamic response of acceleration, real-time online frequency identification of simple harmonic external excitation can be achieved. It solves the shortcomings of vibration sensors in actual engineering that can only obtain time domain signals of vibration response but cannot obtain vibration frequency information in real time online, as well as the problems of a few existing frequency sensors with complex structures, high costs, slow recognition speeds, low precision, low efficiency, and narrow applicable frequency bands. The present invention has rich application prospects and practical significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the composition and principle of the frequency sensor of the present invention;

[0034] Figure 2 Flow chart of frequency identification and acquisition in frequency sensor;

[0035] Figure 3 It is the flow chart of the experimental device in implementation one;

[0036] Figure 4 is a time history curve of acceleration of the effective load of the sensor in the second embodiment under external excitation (12);

[0037] Figure 5 This is a diagram showing the frequency identification results of the effective load of the sensor in the second embodiment under external excitation (12). DETAILED DESCRIPTION

[0038] The following will refer to the attached Figure 1 To Attachment Figure 5Specific embodiments of the present invention are described in more detail. However, it should be noted that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0039] Specific implementation method 1: The experimental device of this embodiment is as shown in the attached Figure 3 As shown, it includes a data acquisition analyzer, a vibration table system, a power amplifier, a computer and the invented frequency sensor, wherein the invented frequency sensor includes a mass-spring-damper system and an accelerometer, as shown in the attached Figure 1 As shown. The computer is used to process the data input / output operation of the entire experimental system. The vibration signal is set by the computer, generated by the data acquisition analyzer, and transmitted to the power amplifier for signal amplification, and then transmitted to the vibration table to generate vibration. The frequency sensor is vertically installed on the vibration table. Under the vertical excitation force provided by the vibration table, the mass-stiffness-damping system in the frequency sensor vibrates. The acceleration signal is collected by the accelerometer, and the collected acceleration signal is transmitted to the data acquisition analyzer for analysis, and the computer is calculated to identify the frequency of the external excitation in real time online.

[0040] The vibration displacement signal set by the computer is

[0041] u(t)=u0sin(ωt+φ) (10)

[0042] In the formula, u0 is the displacement amplitude of the vibration, ω is the designed frequency, φ is the phase difference of the vibration, and t is time. It is worth noting that ω can be designed to be a constant value or change with time, and there is no upper or lower limit, which can reflect the wide versatility and high applicability of the frequency sensor of the present invention.

[0043] Under the vibration displacement excitation, the dynamic equation of the frequency sensor system is:

[0044]

[0045] Where m is the mass of the frequency sensor payload, c is the internal damping coefficient of the frequency sensor, k is the stiffness of the internal spring of the frequency sensor, and x is the displacement of the mass block.

[0046] According to formula (1) and the invented vibration frequency identification method based on acceleration information, the time series {t} and acceleration series {t} obtained by the data acquisition analyzer are converted into {t}. Pass it to the computer for the following calculations and processing:

[0047]

[0048] Where t0≥0 represents the start time of frequency estimation. The adjustment strategy is shown in the attached Figure 2 , p4 and r4 are given by the following formula.

[0049]

[0050] Where r1, r2, r3, p1, p2 and p3 are all intermediate parameters.

[0051] The present invention is arranged on a vibration table, and the vibration frequency of the vibration table can be identified in real time online. The above shows the principle and process of using the frequency sensor proposed by the present invention to measure and collect the vibration frequency in real time online.

[0052] Specific implementation method 2: Using the frequency sensor proposed in the present invention, the vibration frequency is identified based on the acceleration signal through numerical simulation. The frequency sensor used in this embodiment has an effective mass of 0.02 kg, a spring stiffness of 500 N / m, and a damping of 10 N / m. 2 , the gain is 0.01.

[0053] Under the action of simple harmonic displacement excitation, the dynamic model of the effective load inside the frequency identification sensor is:

[0054]

[0055] Wherein, m is the mass of the frequency sensor payload, k is the stiffness of the spring inside the frequency sensor, c is the damping coefficient inside the frequency sensor, u(t)=u0 sin(ωt+φ) is the displacement expression of the vibration of the measured object, u0 is the displacement amplitude of the vibration, ω is the frequency to be measured, and φ is the phase difference of the vibration. In this embodiment, the simple harmonic displacement excitation is given by the following formula:

[0056] u(t)=u o (t)sin(ωt) (12)

[0057] In the formula,

[0058]

[0059] The acceleration time history of the effective load in the frequency sensor under the above excitation is shown in the attached figure. Figure 4 shown.

[0060] From formula (1) and the invented vibration frequency identification method based on acceleration information, it can be known that the external excitation frequency ω can be explicitly expressed by the following formula:

[0061]

[0062] In the formula, is the acceleration of the system, t0≥0 indicates the start time of frequency estimation, and its adjustment strategy is shown in the attached Figure 2 , Δ t =t-t0 represents the length of the identification signal. The online real-time identification results of the frequency sensor for the simple harmonic displacement excitation (12) are shown in the attached figure. Figure 5 shown.

[0063] As shown in the second embodiment, it can be proved through simulation that for complex variable frequency simple harmonic excitation, the frequency sensor of the present invention can accurately and quickly identify the vibration frequency.

[0064] The above two implementations can provide a more thorough understanding of the present invention and its implementation, and more intuitively demonstrate the excellent frequency measurement and acquisition performance and huge engineering application potential of the present invention.

Claims

1. A vibration frequency sensor based on dynamic response of acceleration, characterized in that: The sensor comprises an accelerometer, a mass block, a damper and a spring; The accelerometer is used to collect the acceleration signal of the mass block in real time online. The accelerometer and the mass block together constitute the effective load of the frequency sensor; the effective load, the damping and the spring constitute a typical single-degree-of-freedom mass-spring-damper system; The working principle of the sensor is: According to the theory of single-degree-of-freedom mass-spring-damper system in structural dynamics, the dynamic model of this vibration sensor is an ordinary differential equation. Where m is the mass of the effective load inside the frequency sensor, d is the differential sign, t is time, x is the displacement of the mass block, c is the damping inside the frequency sensor, k is the stiffness of the spring inside the frequency sensor, u(t) = u0 sin(ωt+φ) is the displacement expression of the measured system doing simple harmonic vibration, u0 is the displacement amplitude of the vibration, ω is the frequency to be measured, and φ is the phase difference of the vibration; Differentiate equation (1) twice with respect to time, and we get make represents the acceleration of the payload, and substituting it into equation (2) yields Differentiate equation (3) twice with respect to time, and we get Multiply both sides of equation (3) by ω 2 ,get Adding equations (4) and (5) yields Multiply both sides of formula (6) And integrate the time t four times. After partial integration, we can get Where t0≥0 represents the start time of frequency estimation, and r4 and p4 are expressed as follows: In the formula, r1, r2, r3, p1, p2 and p3 are all intermediate parameters; From formula (7), we can see that only a small time interval Δ t The acceleration information in can be used to explicitly calculate the simple harmonic vibration frequency ω, In the formula, represents the frequency collected by this frequency sensor, γ represents the filter gain, and e is the natural base.

2. The vibration frequency sensor based on acceleration dynamic response according to claim 1, characterized in that: Real-time control can effectively cope with the situation of changes in external excitation frequency; the frequency identification process is divided into two parts, the transient stage and the steady-state stage. The frequency difference value is defined as the difference between the frequency estimate value of the current step and the frequency estimate value of the previous step divided by the step size. The initial process of frequency identification is a transient process. In this stage, when the frequency difference value converges, the frequency estimate value also approaches the true value, and the identification process enters the steady-state stage. In this stage, if the frequency difference value suddenly changes, it means that the excitation frequency has changed. At this time, the start time of updating the frequency estimate is the current moment. The above is the adjustment strategy for the start time of frequency estimation in response to changes in external excitation frequency.

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