US3715920A
Expired / Lapsed
US
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Apparatus for determining the damping ratio of a second order vibration system
Assignee: Honeywell Inc
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Filing: 1971-04-20
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Granted: 1973-02-13
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Expires: 1991-04-20
Abstract
Abstract Apparatus for measuring the damping ratio of a second order system. The apparatus takes the form of a mass rate flow meter comprising an impact plate adapted to be inserted in a fluid flow. The plate and its mounting means forms a second order system which has a damping ratio proportional to the rate of mass flow. The plate is connected in a loop with an integrator, or a differentiator, and a multiplier. The integrator of differentiator provides, among other things, phase shifting. The loop gain is increased until the loop oscillates. Automatic gain control stabilizes the oscillations and the amplitude of the loop oscillations is compared with a reference quantity. The signal resulting from this comparison is used to adjust the gain of the multiplier such that the amplitude of the loop oscillations is kept constant. The signal used to adjust the gain of the multiplier is proportional to the damping ratio of the second order system and therefore is also proportional to the mass flow rate.
Inventors
- 👤 L Groberman
- 👤 E Wuori
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 21:55
CPC Classifications
G; G01; G01F; G01F1/00; G01F1/76; G01F1/78
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
278 words
Apparatus for determining the damping ratio of a second order system, the system having a symmetrical vane attached to a shaft mounted for oscillator movement about its longitudinal axis, the shaft including a torsional spring, the vane and shaft adapted to be mounted in a fluid flow, and the damping ratio of the second order system being a function of the mass flow rate, the second order system having a Laplace transfer function of the form omega n2/(s2+ 2 gamma omega ns+ omega n2) where omega n is the natural frequency of this system and gamma is the damping ratio, comprising: a phase shifting network with a Laplace transform of the form 1/ Tau s+1 connected in a loop with the second order system, the resulting loop system having a root locus equation of the form A'' omega n2/(( Tau s+1)(s2+2 gamma omega ns+ omega n2)) -1 where A'' is the gain of the loop and Tau is a time constant associated with the phase shifting network; means for increasing the gain of the loop system until the root locus of the loop system crosses the imaginary axis in a complex number plane and oscillations are caused to build up in the second order system; means for detecting the amplitude of the oscillations; an amplitude reference signal; means for comparing the detected amplitude with the amplitude reference signal and developing a signal proportional to the difference thereof; and, means for controlling the gain of the loop system with a difference signal, the difference signal being a measure of the damping ratio, including a motor means responsive to the difference signal and connected to the shaft for oscillating it.
Claim 2
Dependent Claim
278 words
Apparatus for determining the damping ratio of a second order system, the system having a symmetrical vane attached to a shaft mounted for oscillator movement about its longitudinal axis, the shaft including a torsional spring, the vane and shaft adapted to be mounted in a fluid flow, and the damping ratio of the second order system being a function of the mass flow rate, the second order system having a Laplace transfer function of the form omega n2/(s2+ 2 gamma omega ns+ omega n2) where omega n is the natural frequency of this system and gamma is the damping ratio, comprising: a phase shifting network with a Laplace transform of the form 1/ Tau s+1 connected in a loop with the second order system, the resulting loop system having a root locus equation of the form A'' omega n2/(( Tau s+1)(s2+2 gamma omega ns+ omega n2)) -1 where A'' is the gain of the loop and Tau is a time constant associated with the phase shifting network; means for increasing the gain of the loop system until the root locus of the loop system crosses the imaginary axis in a complex number plane and oscillations are caused to build up in the second order system; means for detecting the amplitude of the oscillations; an amplitude reference signal; means for comparing the detected amplitude with the amplitude reference signal and developing a signal proportional to the difference thereof; and, means for controlling the gain of the loop system with a difference signal, the difference signal being a measure of the damping ratio, including a motor means responsive to the difference signal and connected to the shaft for oscillating it.
Claim 3
Dependent Claim
278 words
Apparatus for determining the damping ratio of a second order system, the system having a symmetrical vane attached to a shaft mounted for oscillator movement about its longitudinal axis, the shaft including a torsional spring, the vane and shaft adapted to be mounted in a fluid flow, and the damping ratio of the second order system being a function of the mass flow rate, the second order system having a Laplace transfer function of the form omega n2/(s2+ 2 gamma omega ns+ omega n2) where omega n is the natural frequency of this system and gamma is the damping ratio, comprising: a phase shifting network with a Laplace transform of the form 1/ Tau s+1 connected in a loop with the second order system, the resulting loop system having a root locus equation of the form A'' omega n2/(( Tau s+1)(s2+2 gamma omega ns+ omega n2)) 1 where A'' is the gain of the loop and Tau is a time constant associated with the phase shifting network; means for increasing the gain of the loop system until the root locus of the loop system crosses the imaginary axis in a complex number plane and oscillations are caused to build up in the second order system; means for detecting the amplitude of the oscillations; an amplitude reference signal; means for comparing the detected amplitude with the amplitude reference signal and developing a signal proportional to the difference thereof; and, means for controlling the gain of the loop system with a difference signal, the difference signal being a measure of the damping ratio, including a motor means responsive to the difference signal and connected to the shaft for oscillating it.
Claim 4
Dependent Claim
278 words
Apparatus for determining the damping ratio of a second order system, the system having a symmetrical vane attached to a shaft mounted for oscillator movement about its longitudinal axis, the shaft including a torsional spring, the vane and shaft adapted to be mounted in a fluid flow, and the damping ratio of the second order system being a function of the mass flow rate, the second order system having a Laplace transfer function of the form omega n2/(s2+ 2 gamma omega ns+ omega n2) where omega n is the natural frequency of this system and gamma is the damping ratio, comprising: a phase shifting network with a Laplace transform of the form 1/ Tau s+1 connected in a loop with the second order system, the resulting loop system having a root locus equation of the form A'' omega n2/(( Tau s+1)(s2+2 gamma omega ns+ omega n2)) 1 where A'' is the gain of the loop and Tau is a time constant associated with the phase shifting network; means for increasing the gain of the loop system until the root locus of the loop system crosses the imaginary axis in a complex number plane and oscillations are caused to build up in the second order system; means for detecting the amplitude of the oscillations; an amplitude reference signal; means for comparing the detected amplitude with the amplitude reference signal and developing a signal proportional to the difference thereof; and, means for controlling the gain of the loop system with a difference signal, the difference signal being a measure of the damping ratio, including a motor means responsive to the difference signal and connected to the shaft for oscillating it.
Claim 5
Dependent Claim
16 words
The apparatus of claim 1 wherein the vane is a solid round disc with sharp edges.
Claim 6
Dependent Claim
232 words
Apparatus for determining the damping ratio of a second order system comprising: means for oscillating the second order system and forming a first loop with the second order system, including means for developing a signal corresponding to the position of the second order system, comprising an oscillator having a frequency which is relatively high with respect to the natural frequency of the second order system, a transducer comprising a rotor connected to the second order system and a stator associated with the rotor and having first and second windings, The first winding energized by a signal by the oscillator, and a phase-demodulator connected to the second winding, the demodulator synchronized with the oscillator; means for integrating the positional signal, the integrated positional signal being shifted in phase from the positional signal as a result of the integration; motor means energized by the integrated signal and applying a corresponding torque to the second order system; and, means forming a second loop, directly responsive to the positional signal, for controlling the gain of the motor means and hence the gain of the first loop so that oscillations of the second order system are artificially sustained at zero damping ratio, including means for developing a signal proportional to the gain of the motor means and hence the gain of the first loop, the gain being proportional to the damping ratio of the second order system.
Claim 7
Dependent Claim
232 words
Apparatus for determining the damping ratio of a second order system comprising: means for oscillating the second order system and forming a first loop with the second order system, including means for developing a signal corresponding to the position of the second order system, comprising an oscillator having a frequency which is relatively high with respect to the natural frequency of the second order system, a transducer comprising a rotor connected to the second order system and a stator associated with the rotor and having first and second windings, The first winding energized by a signal by the oscillator, and a phase-demodulator connected to the second winding, the demodulator synchronized with the oscillator; means for integrating the positional signal, the integrated positional signal being shifted in phase from the positional signal as a result of the integration; motor means energized by the integrated signal and applying a corresponding torque to the second order system; and, means forming a second loop, directly responsive to the positional signal, for controlling the gain of the motor means and hence the gain of the first loop so that oscillations of the second order system are artificially sustained at zero damping ratio, including means for developing a signal proportional to the gain of the motor means and hence the gain of the first loop, the gain being proportional to the damping ratio of the second order system.
Claim 8
Dependent Claim
95 words
The apparatus of claim 3 wherein the means forming a second loop for controlling the gain of the first loop, comprises: means for detecting the amplitude of the second order system oscillations; an amplitude reference signal source; means for comparing the detected amplitude with the reference signal and developing a control signal corresponding to the algebraic sum thereof, the control signal being applied to the motor means connected to the second order system, the motor means developing a torque and applying it to the second order system, the developed torque corresponding to the control signal.
Claim 9
Dependent Claim
22 words
The apparatus of claim 4 wherein the means for detecting the amplitude of the second order system oscillations is a rectifier circuit.
Claim 10
Dependent Claim
22 words
The apparatus of claim 4 wherein the means for detecting the amplitude of a second order system oscillations is a sample-and-hold circuit.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-02-13 | 1976-08-14 | 1977-02-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-02-13 | 1980-08-14 | 1981-02-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-02-13 | 1984-08-14 | 1985-02-13 | $7700.00 | Window Closed / Lapsed |