KR100765407B1 - Active vibrometer system with analyzer - Google Patents

Abstract

An active vibration measuring system with a tester is provided to allow an unskilled operator to perform a nondestructive inspection and to judge a defective insulator with a crack effectively and reliably. An active vibration measuring system with a tester comprises an active vibration measuring sensor, a measuring sensor driving and amplifying unit, and a microcomputer. The active vibration measuring sensor includes a permanent magnet(13) and repulsion and attraction coils(11,12). The magnet and the coils are arranged to generate power by the current in an impacting mode applying an impact to an inspection object, and to increase sensing efficiency in a sensing mode detecting vibration. An amplifier includes a mute circuit cutting off a signal generated in the impacting mode temporarily to monitor an audio signal stably.

Description

Active Vibrometer System with Diagnostic Function

1 is a block diagram showing an active vibration measuring apparatus having a diagnosis function according to an embodiment of the present invention;

Figure 2 (a) and (b) and (c) is an arrangement and operation principle showing the operating principle of the coil and the permanent magnet of the active vibration measuring device according to an embodiment of the present invention,

3 is a component picture showing an internal component of an active vibration measuring device according to an embodiment of the present invention;

4 is a circuit diagram showing a model of the insulator-vibration measuring system according to an embodiment of the present invention;

5 is a force measurement graph showing a measured value of the force generated by the active vibration measuring device in the impact mode according to an embodiment of the present invention,

6 is a measurement device impulse response graph showing an impulse response of an active vibration measuring device system according to an embodiment of the present invention;

7 is a graph of insulator impulse response showing the impulse response of the insulator system according to an embodiment of the present invention,

8 is a simulation result graph showing simulation results of a permanent magnet and insulator vibration signal detected in an active vibration measuring system according to an embodiment of the present invention;

9 is a circuit diagram showing the configuration of a circuit of an active vibration measuring device driving and measuring signal amplifier according to an embodiment of the present invention;

10 is an experimental photograph showing an experiment for the detection of cracked insufficiency in accordance with an embodiment of the present invention;

11 is an insulator detection photograph showing a sample of cracked defective insulator detected according to an embodiment of the present invention;

12 is a comparative graph showing vibration characteristics of normal and detected defective insulators according to an embodiment of the present invention;

13 is an experimental photograph showing a state of experiment to check the assembly state of the structure according to another embodiment of the present invention,

14 is a graph illustrating vibration characteristics of normal and abnormal assembled state structures according to another embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

1: Active Vibration Measurement Device 2: Vibration Measurement Device Drive and Amplifier

3: microcomputer for signal analysis 4: object to be inspected

11: Repulsion coil 12: Suction coil

13: permanent magnet

The present invention is an active vibration measuring system having a screening function, and more particularly, has a screening function for performing a non-destructive inspection to check whether there is a defect inside the mechanical part or the connection part of the structure by measuring the mechanical vibration It relates to an active vibration measuring system.

Conventional nondestructive inspection using ultrasonic waves is useful for detecting local defects because it uses the property of going straight and reflecting the defects of ultrasonic waves, but the entire part or structure is used as a sensor to detect local defects. Since scanning and flaw detection, there was a problem that the number of the inspection object is inefficient.

In addition, in the prior art, whether the parts or structures are defective or not, the sound generated by tapping with a tool such as a small hammer (Hammer) was mainly heard. Therefore, such a manual work requires the knowledge of highly skilled professionals. Judging from the problem was difficult to quantify.

SUMMARY OF THE INVENTION The present invention has been made in view of the foregoing, and provides a nondestructive flaw detection system that inspects parts or structures to detect locally existing defects, and easily performs nondestructive flaw detection even by highly skilled professionals. It is an object to provide a system for quantification.

According to the active vibration measuring system having a diagnosis function of the present invention for achieving the object as described above, driving the active vibration measuring device and the vibration measuring device for impacting the object to be inspected and measuring the vibration signal generated accordingly And a signal analysis microcomputer for diagnosing a defect by analyzing the signal measured by the vibration measuring device driving and amplifying device and the vibration measuring device.

According to a preferred feature of the present invention, the active vibration measuring device comprises a permanent magnet and two coils and a spring of the Membrane phenomenon, the role of applying a certain amount of mechanical shock to the object to be inspected and the resultant It is characterized in that to perform the role of detecting the vibration of the object at the same time, the permanent magnet and the two coils of the active vibration measuring device generates a force with the applied current in the impact mode (impacting mode) to impact the object to be inspected In the measuring mode for sensing vibration, a repulsion coil and an suction coil are disposed to have excellent sensitivity.

In addition, the driver for driving the vibration measuring device is characterized in that it comprises a one-shot generator that can adjust the pulse width for sequential control, the measurement signal amplifier temporarily cuts off the signal generated in the shock mode to the acoustic signal ( It is characterized in that it comprises a signal circuit (Mute Circuit) so that it can stably monitor the audio signal, and the microcomputer for signal analysis is characterized by having an FFT analyzer.

In the active vibration measuring system having a diagnosis function according to the present invention configured as described above, the FFT analyzer converts 2 ⁿ (= natural numbers) of data into the frequency domain, and the signal analysis microcomputer analyzes the frequency distribution. And a diagnostic algorithm for detecting a defect.

Hereinafter, a preferred embodiment of the present invention including the above components will be described in more detail with reference to the accompanying drawings.

1 is a block diagram showing the configuration of an active vibration measuring system having a diagnosis function according to an embodiment of the present invention, Figures 2 (a), (b) and (c) is a coil and a permanent magnet of an active vibration measuring device The operation principle diagram showing the operation principle of.

Referring to Fig. 1, the system of the present invention is composed of an active vibration measuring apparatus 1, a vibration measuring apparatus driving and amplifier 2, and a signal analysis microcomputer 3.

Referring to FIGS. 1 and 2, the active vibration measuring device 1 includes a permanent magnet (PM) 13, two coils 11 and 12, and a spring (not shown) to shock an object to be inspected. An active vibration measuring device 1 for applying a vibration signal and simultaneously measuring a vibration signal, a driving and amplifier 2 for driving a vibration measuring device and amplifying the measured vibration signal, and analyzing a signal measured in the vibration measuring device. It consists of a microcomputer 3 for signal analysis.

Referring to FIG. 2, the active vibration measuring apparatus 1 includes a permanent magnet 13, two coils 11 and 12, and a spring (not shown) of the Membrane phenomenon, so that a certain amount of mechanical impact is applied to the object to be inspected. It is designed to perform the role of applying the pressure and detecting the vibration of the resultant object at the same time.It is small and light and weighs about 10g, so it is easy to carry and small robot for the automation of work. Also suitable for mounting on.

Referring to FIG. 2 (a), the active vibration measuring device 1 generates a large force by an applied current in an impact mode in which an impact is applied to the inspection object 4, and the vibration measuring mode ( In the sensing mode, the repulsion coil 11 and the suction coil 12 are arranged in series so as to have excellent sensitivity. Referring to FIG. 2 (b), when the current is applied to the coil in the shock mode, the two coils 11 and 12 connected in series are wound opposite to each other, and thus the direction of the magnetic flux is also formed to be opposite to each other. The magnetic fluxes having different directions may generate a repulsion force and an pulling force on the permanent magnet 13 inside the coil, thereby generating the maximum force even when a small current is applied to the coil. Referring to FIG. 2 (c), when the permanent magnet 13 advances to the right after the impact point, the permanent magnet 13 is held by the suction coil 12 and no longer advanced. I can't. In the measurement mode, since the current flowing through the coil is cut off, the permanent magnet 13 is returned to the stationary point by a spring, and thus is inertial, thereby preventing the permanent magnet 13 from responding to the vibration of the inspection object reaching the audible frequency of several kHz. Therefore, the coil in contact with the object to be inspected vibrates while the permanent magnet 13 is stopped, so that the coil intersects the magnetic flux of the permanent magnet 13 due to the vibration of the insulator, so that both ends of the coil have the right hand of Fleming. The organic electromotive force corresponding to the law appears. The stop point is set to the point where the sensitivity of electromotive force induced in the coil is the highest.

3 is an exploded photograph showing the internal components of the active vibration measuring apparatus 1 according to the embodiment of the present invention.

The active vibration measuring apparatus 1 includes a coil assembly incorporating the coils 11 and 12, a PM impactor 13, which is an impactor, and a spring and an active vibration measuring apparatus of the Membrane phenomenon. It consists of a cover (Cover) for sealing 1).

FIG. 4 is a circuit diagram logically showing the operation of the active vibration measuring apparatus 1 when the active vibration measuring apparatus 1 is applied and applied to the purpose of detecting cracked insulators installed on a transmission line. Referring to FIG. 4, since the active vibration measuring device 1 is attached to the surface of the insulator while checking the insulator, the insulator-vibration measuring device system can be represented by a double Spring-Mass-Damper system. In addition, M and m, K and k, B and b specified in FIG. 4 represent the mass, the spring constant, and the damping constant of the insulator and the active vibration measuring device 1, respectively.

The following is the loop and insulator system loops of an active vibration measurement system.

First, when the loop of the vibration measuring system flows a current in the coil in the impact mode, the force generated in the permanent magnet 13 is obtained by Fleming's left-hand rule as shown in Equation 1 below.

(1)

(One)

In Equation (1), the magnetic flux density of the permanent magnet 13 is represented by B _m (z) because the magnitude varies with distance along the centerline of the coil, l _c is the length of the coil, and i _c (t) is the coil. The current flowing in it. The vibration measuring system loop is represented by a differential equation such as Equation (2).

(2)

(2)

FIG. 5 is a graph showing the measurement of the force generated by the active vibration measuring device 1 in the permanent magnet 13 according to the distance when a constant current 1A flows through the coil in the impact mode.

Referring to FIG. 5 and Equation (1), it can be seen that the magnetic flux density B _m (z) of the permanent magnet is maximum at the stationary point, and thus, a large force is applied to the permanent magnet 13 at the initial stage of the impact mode. This will occur. In addition, in the measurement mode, since the permanent magnet 13 is located at the stop point, it can be seen that the sensitivity of the electromotive force induced in the coil is maximized.

FIG. 6 is a graph showing experimental data of an impulse response obtained when an impact is applied to the vertical direction of the active vibration measuring apparatus 1 in order to analyze the dynamic characteristics of the active vibration measuring apparatus system.

Referring to FIG. 6, the active vibration measuring system can obtain constants of the system by analyzing the impulse response as the secondary system. Damping rate obtained by least-squares method Damping Rate r _m = ± 0.9 · e ^{-60.0 * (t-0.086)} and oscillation frequency ω _m = 50.8Hz obtained by Fast Fourier Transform (FFT) Since the mass m of the (Impactor) is known, 3.9x10 ^-3 kg, the remaining constant can be obtained from Equation (3).

(3)

(3)

The moment the impactor of the active vibration measuring device 1 impacted the insulator surface, the velocity dx ₂ / dt of the impactor was changed to -e dx ₂ / dt by the repulsive coefficient e, which was measured as e = 0.3. The vibration signal induced in the coil of the vibration measuring device by the permanent magnet (m) can be obtained by the following equation (4) by Fleming's right hand law.

(4)

(4)

Unlike in the shock mode, the current flowing through the coil is cut off in the measurement mode, and the impactor is inertial, so that the dx ₂ / dt is hardly affected by the vibration of the insulator.

Equation (5) below is the differential equation of the insulator system loop.

(5)

(5)

Here, f ₁ exists only at the moment when the impactor of the active vibration measuring apparatus contacts the insulator surface.

FIG. 7 is a graph showing impulse response experimental data obtained when an impact is applied in the vertical direction to the surface of the insulator skirt performed to analyze the dynamic characteristics of the insulator system.

Referring to FIG. 7, since the insulator system is also a secondary system, constants of the insulator system may be obtained by analyzing the impulse response.

Damping rate obtained by least-squares method r _i = ± ^{1.95e -80.0 * (t-0.0054)} and oscillation frequency ω _i = 2.148 kHz obtained by fast fourier transform (FFT ⁾ and mass of insulator M = 5.3 Since kg is known, the remaining constant is obtained by the following equation (6).

(6)

(6)

Therefore, the equations (2) and (5) are summed to express the differential equations of the whole insulator-vibration measurement system in matrix form as shown in the following equation (7).

(7)

(7)

8 substitutes the electromagnetic characteristics of the active vibration measuring apparatus obtained from Equations (1) and (4) and FIG. 5 into Equation (7), and constants of the mechanical system obtained from Equations (3) and (6). It is a graph showing the simulation results of the vibration signal of the insulator-vibration measurement system and the simulation of the permanent magnet and insulator vibration signals detected by the active vibration measurement system.

Referring to FIG. 8, when the current flows to the coil at the start point, the impactor starts to move, the velocity of the shocker is reversed at the impact point at which the impactor collides with the insulator, and then vibrates at the insulator. This can be seen, and the vibration frequency of the insulator and the impactor shows a big difference, so by using an appropriate filtering technique, only the insulator vibration can be easily selected.

Fig. 9 is a block diagram showing the configuration of an active vibration measuring device drive and measurement signal amplifier 2. The drive of the active vibration measuring device is sequentially divided into the shock mode and the measurement mode. To start the shock mode, the start switch must be pressed or the microcomputer sends a Start signal. When the start switch is pressed, the MOSFET (Metal-Oxide Semiconductor Field Effect Transistor) is turned on and then turned off by the One-Shot Generator 1 for a period of time. During this time, voltage is applied to the coil of the active vibration measuring device. Force is generated on the impactor. Referring to FIG. 8, the impact point is inverted at the impact point at which the impactor collides with the object to be inspected as shown in the simulation, so that the impact is repeated to prevent chattering that occurs repeatedly. The One-Shot Generator 1 must be adjusted to turn the MOSFET off before it hits the self-test object. Since the vibration signal needs to be measured after the impactor stops after a certain time has passed since the impactor of the active vibration measuring device hits the object to be inspected, the One-Shot Generator 2 generates a signal to the amplifier for a certain period of time after the start. Block it. As such, when the signal is temporarily blocked, only the vibration signal of the object to be inspected can be stably heard when monitoring the audio signal. Therefore, it is necessary to adjust the pulse width of the One-Shot Generator 2 to be larger than the pulse width of the One-Shot Generator 1. The vibration signal of the object to be inspected appears as an organic electromotive force in the active vibration measuring device coil, and after passing through the coupling capacitor, the transient voltage is cut off in the clamper. This signal is fed to the filter when the mute circuit is connected, which selectively attenuates components above 5 kHz that are not necessary for signal interpretation. The signal is then amplified by the amplifier to accommodate 5V, the input range of the A / D converter whose maximum voltage is built into the microcomputer.

Preferably, referring to Figure 1, the signal analysis microcomputer 3 generates a Start signal for initializing the shock mode, and waits for a predetermined time, the signal of the One-Shot Generator 2 from logic '1' to logic '0' The measurement mode starts from the moment it falls. When the measurement mode is started, the A / D converter measures 2 ⁿ (= natural numbers) of the measured data of the signal required by the FFT at the given measurement period and sends it to the FFT analyzer. The FFT analyzer analyzes the signal of the frequency domain converted by the FFT algorithm to determine whether the insulator vibration signal is normal or abnormal. In order to efficiently detect defects of the object under test in the frequency domain, the vibration frequency of the object to be inspected should be up to 5 kHz, considering the margin, because the vibration frequency of the object is about 2-3 kHz. Applying Nyquist Theorem to this, the A / D converter should measure the signal at a period of 10 kHz, and obtain 1024 (= 2 ¹⁰ ) data considering the computational power of the microcomputer for FFT. desirable. In general, if the object to be inspected has cracked defects, it vibrates at different resonant frequencies around the gold boundary or at low frequencies as a whole. Therefore, through a diagnostic algorithm that analyzes the frequency distribution implemented in the microcomputer for signal analysis Defects can be effectively detected.

FIG. 10 is a photograph showing a cracked insulator detection experiment according to an embodiment of the present invention, and FIG. 11 is a photograph showing the cracked insulator sample.

In the measurement mode, the signal detected by the active vibration measuring apparatus 1 is converted into a frequency domain by an FFT performed by a microprocessor of the micropro computer 3 for signal analysis, and thereafter, an abnormal diagnosis algorithm determines whether or not the signal is defective. As shown in FIG. 11, an active vibration measuring system having a detector according to the present invention has been proved through experiments that it can efficiently detect finely cracked defects that are difficult to visually identify.

12 are graphs showing vibration characteristics of normal and crack insulators.

Referring to FIG. 12, it can be seen that the fine cracked insulator 1 has a vibration derived from the intrinsic frequency of the normal insulator in comparison with the natural frequency of the normal insulator. It can be seen that the magnitude of the vibration and vibration are significantly lower than normal.

Figure 13 is a picture showing the structure assembly test state of the structure according to another embodiment of the present invention.

Referring to Figure 13 shows an example of applying the active vibration measuring system equipped with a detector according to the present invention to the test structure performed to check whether it can be used to check the transmission line assembly state. The structure used in the experiment was cut into a rectangular aluminum profile of 20mm × 20mm into 2 pieces of 160mm and 2 pieces of 210mm, and firmly joined in a square shape using a 'b' shaped bracket, and then the bolts were tightened at one connection point. The loosening state was simulated.

Accordingly, Figure 14 is a graph showing the vibration characteristics of the assembled state and the assembled state slightly or a lot of loose structure.

Referring to FIG. 14, although local resonance frequencies are formed at a relatively high frequency when the tightening adjustment bolt is normally tightened, local resonance occurs at a low frequency when slightly loosened, and a large resonance frequency appears at low frequency when largely loosened. Can be. As described above, since the resonance and local resonance frequencies vary greatly according to the tightening state of the structure, it is easy to determine whether there is a defect compared to the frequency distribution of the steady state.

As described above, an embodiment of an active vibration measuring system having a diagnosis function according to the present invention is constructed. Although the present invention has been described by way of limited embodiments and drawings, the present invention is not limited thereto and is intended by those skilled in the art to which the invention pertains to the spirit and scope of the present invention. Of course, various modifications and variations are possible within the scope of equivalents.

The active vibration measuring system having a diagnosis function according to the present invention can be applied to all fields related to the inspection of train wheels, the inspection of assembly of steel towers and the ripening state of fruits and vegetables or the non-destructive inspection of parts and structures by using the resonance frequency. It is particularly effective when applied to the purpose of detecting cracked faulty transmission line insulators and checking the assembly of the structure.

In addition, the active vibration measuring system equipped with a detector according to the present invention efficiently and reliably discriminates cracked defective insulators, which could not be detected by a conventional method of measuring the electric field of the insulator or a shared voltage of the insulator. can do.

Claims (8)

The vibration is applied to the object to be inspected and the vibration signal generated according to the active vibration measuring sensor (1) and the vibration consisting of a permanent magnet (13), two coils (11, 12) and a spring of the phenomenon Membrane A vibration measurement sensor driving and amplifier device (2) for driving a measurement sensor and amplifying the measured vibration signal, and a signal analysis microcomputer (3) for diagnosing a defect by analyzing a signal measured by the active vibration measurement sensor (1). In the active vibration measuring system having a diagnosis function consisting of, The permanent magnet 13 and the two coils 11 and 12 of the active vibration measuring sensor generate a force with a given current in an impact mode in which an object to be examined is impacted, and a measurement mode that detects vibration. (Sensing Mode) active vibration measuring system having a diagnostic function, characterized in that the repulsion coil (11) and the suction (Attraction) coil (12) is disposed so that the sensitivity is excellent. delete delete delete According to claim 1, wherein the amplifier temporarily blocks the signal generated in the shock mode to provide a check function (Mute Circuit) so that it can stably monitor the audio signal (Audio Signal) Active vibration measurement system. delete delete delete

Images