FI107355B - Vibration pickup - Google Patents

Description

107355

Vibration Sensor - VIBRATIONSGIVARE

The present invention relates to a vibration transducer based on an accelerometer transducer which outputs a generalized offset derivative (fractional derivative) signal having an order of magnitude less than two and an order of magnitude different from zero or one. The invention utilizes the non-linear region (6) of the acceleration sensor and integrates by means of mass, damping and spring within the sensor (Fig. 1).

Conventionally, displacement, speed and acceleration sensors have been used to measure machine vibrations [1]. Transition sensors measure the relative displacement between the sensor and the object being measured. If you want to measure the bearing housing so-called. absolute displacement, this is done by integrating the signal from the velocity or acceleration sensor measured in the linear range of the sensor. The problem then arises when using known solutions the integration has to be performed by separate analog circuits or by performing calculations while the accuracy of the results suffers. A novel solution to this problem is characterized by what appears in the characterizing part of the claim.

In the following, the invention will be described in detail with reference to the figures, in which: ··· Figure 1 shows a conventional piezoelectric accelerometer with 1 being a mass, 2 being a piezoelectric element, 3 being a spring and 4 being a body.

Figure 2 shows the response of the accelerometer obtained during the vibration tests. 5 shows the linear region of the sensor and 6 shows the non-linear region of the sensor which is above the resonance frequency of the sensor 25.

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Figure 3 shows the output of the acceleration sensor compared to the constant acceleration of the sensor, the ratio of the angular velocity ω and the specific angular velocity ωη = (klm) '12, where k is the spring constant and m is the mass, and the relative damping factor [ , KJ y-y 5 7 is related to the value of relative damping coefficient 0.7.

Figure 2 shows the normally used linear operating region (5) of the accelerometer and the non-linear region (6) above the resonant frequency. Typically, accelerators * u. * Use a value of relative damping coefficient between 0.65 and 0.7 [2], 10 to obtain the widest possible linear range, as shown in the graph (7). The Paten application [3], which relates to derivation, utilizes a nonlinear region below the sensor resonance frequency. The present invention relates to the integration of half of the signal and utilizes a non-linear region (6) at the upper end of the acceleration sensor resonance frequency. j

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I i

The output of the acceleration transducer relative to the acceleration of the transducer having a constant amplitude li i i can be calculated (Fig. 3) from the formula 1 4 j, ...... 1 ...... · oi) i-W2

J L

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The vibration measurements for maintenance allow ± 10% error [4,5]. Here are some values of relative damping coefficient that can be used to construct sensors that measure directly x, x and x (02) from an ordinary accelerometer so that the absolute value of the error is below 1%. The calculations are based on formula (1) and the values of ωη have been in the order of 0.1 Hz, 1000 Hz and 1000 Hz respectively.

.3 107355 1 Measurement Range Difference Calibration- ζ Frequency x 1 -> 1000 Hz> 1000 Hz 0.1 Hz 0.1 5 x (02) 1210 - 1560 Hz 350 Hz 1000 Hz 0.555 x 920-1090 Hz 170 Hz 1000 Hz 0.4975

Patent application [6] and source [7] deal with the concept of a generalized derivative. For example, the component x1, (02) of the spectrum of the generalized derivative jc (O2) is obtained from the component ai of the compatibility spectrum 10 using the equation ° = (2 (2), where / is the frequency associated with the component at.

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The following describes in detail the calculations related to the construction of the x-output transducer, to three decimal places, with a calibration frequency of 0.1 Hz, ω „of 0.1 Hz and a relative attenuation factor ζ of 0.1.

• »m 20 Frequency Sensor Precise x (pm) x (Jim) 1 Hz 10098.950 10000.000 5.1 Hz 384.612 384.468 10.1 Hz 98.039 98.030 25 50.1 Hz 3.984 3.984 100.1 Hz 0.998 0.998 500.1 Hz 0.040 0.040 1000.1 Hz 0.010 0.010 • <- 1073 ^ 5 4

The sensor constructions based on the ep i-linear operating range of the accelerometer have been discussed above. The signal integration technique disclosed herein can be applied to signals of any type of sensor. These include speed and pressure sensors »i * i l j! i] \ i • i '*! I.

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REFERENCES - ANFÖRDA PUBLIKATIONER

1. LAHDELMA, S., Methods and Instruments for Vibration Control. Helsinki 1988. Training Center for Insi-stringers, Publication 83-88, Systematic Use and Condition Control. 7 sec.

2. THOMSON, W.T., Theory of Vibration with Applications. Prentice-Hall, Inc., Englewood Cliffs, New Jersey 1972.467 s.

3. Patent Application No. 954151 4. VDI2056 BeurteilungnsmaBstäbe fUr mechanische Schwingungen von Maschinen. VDI-RICHTLINIEN, October 1964. 12 s.

5. ISO 2372 Mechanical vibration of machines with operating speeds from 10 to 200 rev / s-Basis for specifying evaluation standards. International Standard, Frist edition-1974-1 ΙΟΙ. 9s.

6. Patent Application No. 934137, Class G 01H.

; · * 7. SKRIVASTAVA, H.M. & OWA, S., Univalent functions, fractional calculus, and their applications. Ellis Horwood Limited, Chichester 1989. 404 s.

Claims (1)

1073ί |: 5 Patent claim Vibration sensor, characterized in that it is based on an acceleration sensor and outputs a signal of a generalized time derivative (fractional derivative) of transition less than two and an order of magnitude different from zero or one. The invention utilizes the non-linear region (6) of the accelerometer and integrates by means of mass, damping and spring within the sensor. i | i i \ · '! i j! »I t t • i <107355 Vibrationsgivare, kännetecknat därav, attdengmndarsigpäenaccelerationsgivare och frän den fas ut signalen av förskjutningens allmänna tidsderivata (bruten derivata), vil-kens grad är mindre än tvä och graden är skilt. In uppfinningen accelerationsgivarens olinjära omräde (6) och integreringen utföras med hjäp av mass, dämpning och fjäder, lively business inom givaren. «