RU2240566C1 - Pendulum acceleration meter - Google Patents

Abstract

FIELD: measuring equipment engineering.

SUBSTANCE: device has pendulum fixed in hermetical body filled with working liquid, which pendulum is displaced from balanced position by effect from acceleration. Position of pendulum is tracked by two coordinates by two optical detectors, made in form of two couples of filament coils fixed on four sides of pendulum in pairs relatively to each other. Filament coils are optically matched in pairs to two coherent light sources and two photo-detectors in two interferometers. Effect from acceleration produces phase change of interfering beams of interferometers, which is measured by electronic system.

EFFECT: higher precision.

3 cl, 2 dwg

Description

The invention relates to measuring equipment and can be used in inertial navigation systems.

Known pendulum accelerometer, in which the position of the pendulum is tracked by a photoelectronic tracking system [1].

The disadvantage of the analogue is the influence on the results of measurements of the position of the pendulum, and hence the magnitude of acceleration, amplitude factors (measuring the brightness of the light source, aging of the photodetector, misalignment of the device, etc.).

Known pendulum accelerometer with a disk metal pendulum and damping device. The angle of rotation of the pendulum is measured using an optical device containing a code disk mounted with a pendulum with radial through slots, a light source and three photodetectors optically matched through a code disk [2].

The output signal of the accelerometer is of a frequency nature here, so this accelerometer is free from the lack of analog.

However, analogue [2] has inherent disadvantages associated with the discretization error of the pendulum deviation, which is especially significant for small values of the pendulum deviation under the action of acceleration. This is due to the fact that the number of slots of the code disk at a certain angle of deviation of the pendulum is, of course.

A pendulum accelerometer is known, comprising a housing and a pendulum fixed inside the housing, as well as two optical sensors of the pendulum displacement from the equilibrium position oriented in two orthogonal directions and made in the form of pairwise optically matched two pairs of light sources and photodetectors connected by outputs to the inputs of amplifiers, the outputs of which are connected to a microprocessor connected by an input to the recorder [3].

This accelerometer [3] is adopted as a prototype.

The advantage of the prototype compared with analogues [1, 2] is the ability to measure the magnitude of the acceleration in two coordinates x, y.

The disadvantage of the prototype is the influence on the measurement results of acceleration of amplitude factors, as in the analogue [1].

The technical result obtained from the implementation of the invention is to eliminate the disadvantage of the prototype by measuring not the amplitude but the phase of the optical signal.

This technical result is obtained due to the fact that in the well-known pendulum accelerometer containing a housing and a pendulum fixed inside the housing, as well as two optical sensors of the pendulum displacement from the equilibrium position, oriented in two orthogonal directions, and made in the form of pairwise optically matched two pairs of sources light and photodetectors connected by outputs to the inputs of amplifiers, the outputs of which are connected to a microprocessor, connected by outputs to a recorder, are fixed in the gonal system, two pairs of fiber coils coordinate pairs optically coupled in two interferometer with light sources and photodetectors, with the light sources are made coherent, body - sealed and filled with hydraulic fluid, and the registrar - a frequency counter.

The accelerometer may also contain two sensors of the sign (direction) of the deviation of the pendulum in a rectangular coordinate system, connected outputs to the microprocessor.

The accelerometer may contain a phase-shifting device installed in one of the fiber coils, while the outputs of the amplifiers are connected to the microprocessor through analog-to-digital converters (ADCs).

Distilled water is used as the working fluid, while the accelerometer case is made of stainless steel.

The invention is illustrated by the drawing, in Fig.1 which presents a structural diagram of the accelerometer, and in Fig.2 - its optical-electronic circuit.

The pendulum accelerometer comprises a housing 1 (FIG. 1) and a pendulum 3 fixed inside the housing on a hinge 2. The housing 1 is made of stainless steel and sealed. Case 1 is filled with distilled water 4.

There are two optical sensors for the displacement of the pendulum from the equilibrium position in the x, y direction under the action of acceleration.

The optical sensors are made in the form of two pairs of fiber coils 5, 6 and 7, 8 of optical fiber located on the pendulum 3 from its different sides in a rectangular coordinate system x, y. (In Fig. 1, the fiber coils 7 and 8 are merged in the drawing).

There are also two coherent light sources 9, 10 (figure 2), made in the form of LEDs, and two photodetectors 11, 12, made in the form of photodiodes.

Light sources 9, 10 and photodetectors 11, 12 are optically coupled through fiber coils 5, 6 and 7, 8 into two interferometers.

Fiber coils 6, 8 of interferometers may contain phase-shifting devices 13, 14.

The outputs of the photodetectors 11, 12 are connected through series-connected amplifiers 15, 16 and the ADC 17, 18 to two inputs of the microprocessor 19, the output of which is connected to the recorder 20, made in the form of a frequency meter.

When the main claim is implemented to simplify the microprocessor 19's program of work, it is advisable to introduce two sensors of the pendulum deviation sign 3 at the x, y coordinates, made according to any known scheme. For example, in the form of a cylindrical capsule with two pairs of electrical contacts at the base of the capsule, closed by an electrically conductive ball located inside the capsule when the latter is tilted. Capsules are fixed at the end of the pendulum 3 (not shown).

Wires to the capsules and optical fibers to the light sources 9, 10 and photodetectors 11, 12 pass inside the pendulum 3 and go outside the housing 1. (In Fig. 1, this optical and electrical connection is not shown).

The outputs of the amplifiers 15, 16 can be connected to the actuators of the product on which the accelerometer is used (for example, a rocket, a dashboard, a mobile craft, etc.) to adjust the magnitude of the speed and direction of its movement.

The pendulum accelerometer operates in two modes: in the mode of large deviations of the pendulum (the first two claims) and small (paragraphs 1, 2, 3 of the claims).

In the first mode of operation, the accelerometer does not have a phase shifter 13, 14 and ADC 17, 18. And the output signals of the photodetectors 11, 12 look like interference peaks.

In the second mode, interferometers operate within a quarter of the interference band in the quasilinear portion of the interference band. Previously, using phase shifting devices 13, 14, the initial phase difference of the interfering rays is set equal to 90 °. The analog output signal using the ADC 17, 18 is converted to digital for normal operation of the microprocessor 19.

Sometimes it is advisable to use two pairs of the considered interferometers: for each of the x, y coordinates, use an interferometer to measure small and large deviations of the pendulum 3. In this case, the program of operation of the microprocessor 19 is complicated.

The accelerometer works as follows.

A pre-calibrated accelerometer is attached to the product. The initial position of the pendulum 3 may be vertical or inclined.

When exposed to acceleration, the pendulum 3, and with it the fiber coils 5, 6 and 7, 8, will come into motion. In this case, the dynamic pressure on one of the coils (bow) will be greater than on the other (stern). For example, when the pendulum 3 moves in the x direction, the pressure on the fiber spool 6 will be greater than on the fiber spool 5 (Fig. 1).

In the first mode of operation of interferometers, a frequency output signal will appear at their outputs. The signal frequency carries information about the rate of change of the measured value, and the number of peaks - about its value. Information is supplied to the microprocessor 19 and the frequency counter 20.

In the second mode, the nature of the output signal is analog. After conversion to the ADC 17, 18, it also enters the microprocessor 19 and the recorder 20.

To implement inertial automatic navigation of the product (rocket, torpedo), the signal from the output of amplifiers 15, 16 or ADC 17, 18 is fed to the corresponding coordinate actuators equipped with corresponding electronic units for converting incoming signals (not shown).

Moreover, all fiber coils 5, 6 and 7, 8 of interferometers are in the same conditions in temperature, depth, etc., so the amplitude factors will not affect the measurement results. How is the technical result achieved.

Sources of information

1. Japanese application No. 62 - 157574, cl. G 01 P 15/02, G 01 P 15/11, 1987.

2. Application of Germany No. 4124031, class G 01 P 15/03, 1993.

3. Japanese application No. 62 - 233769, cl. G 01 P 15/11, 1987 - prototype.

Claims (3)

1. A pendulum accelerometer comprising a housing and a pendulum fixed inside the housing, as well as two optical sensors of the pendulum displacement from the equilibrium position oriented in two orthogonal directions and made in the form of pairwise optically matched two pairs of light sources and photodetectors connected by outputs to the inputs of amplifiers the outputs of which are connected to a microprocessor connected to the output of the registrar, characterized in that it further comprises two sensors of the sign of the deviation of the pendulum into the orthogonal coordinate system connected by the outputs to the microprocessor, and two pairs of fiber coils optically coupled in two interferometers with light sources and photodetectors fixed to the pendulum in an orthogonal coordinate system, while the light sources are made coherent, and the case is sealed mainly from stainless steel and filled with a working liquid, mainly distilled water, and the recorder is made in the form of a frequency meter, with optical fibers from fiber coils and electric wires from pendulum deviation sign sensors pass inside the pendulum and exit the housing. 2. The pendulum accelerometer according to claim 1, characterized in that it further comprises a phase-shifting device installed in one of the fiber coils, and the outputs of the amplifiers are connected to the microprocessor through analog-to-digital converters. 3. The pendulum accelerometer according to claim 1 or 2, characterized in that each pendulum deviation sign sensor is made in the form of a cylindrical capsule fixed to the end of the pendulum, with two pairs of electrical contacts at the base of the capsule and an electrically conductive ball located inside the pendulum and closing the capsule contacts when tilting the latter.

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