RU2445575C2 - Sensitive element of vibration coriolis gyroscope - Google Patents

Abstract

FIELD: instrument making.

SUBSTANCE: sensitive element of a gyroscope comprises a thin-walled cylinder with a bottom, an element of its fixation to the gyroscope base and piezoelectric elements of excitation and signal pick-up. The cylinder is made with a thickened upper part - a circular resonator, the bottom and the part of the side surface of the cylinder by means of slots are broken into sectors, and inside each sector there is a slot with the possibility to place piezoelectric elements of excitation and signal pick-up in it.

EFFECT: invention makes it possible to increase sensitivity and accuracy of the gyroscope.

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Description

The invention relates to devices for gyroscopic technology and can be used as a wave resonator.

Known wave gyroscope (Ukrainian patent No. 22153), in which the resonator is made in the form of a thin-walled cylindrical shell with a bottom and a node for attaching the shell to the base along its axis.

In this device, on the free edge of the resonator, along its lateral surface around the circumference are eight piezoelectric elements designed to excite elastic standing waves in the resonator and to pick up the received signal.

An alternating excitation signal with a frequency close to the frequency of the fundamental eigenmodes of the resonator is applied to two diametrically opposite piezoelectric elements, the bending deformations of which cause radial vibrations of the resonator shell and lead to the appearance of an elastic standing wave in the resonator.

When the resonator rotates around the axis with an angular velocity Ω, Coriolis forces appear, due to which radial oscillations arise in the nodes, the amplitude of which is proportional to the angular velocity Ω.

Coriolis forces displace a standing wave with its antinodes and nodes around the circumference, which causes a change in the signals of the piezoelectric elements located in the nodes, while the signals are proportional to the angular velocity Ω.

The disadvantages of this resonator include:

1) the placement of the piezoelectric elements near the free edge of the resonator contributes to the damping of the standing wave, which leads to a decrease in its quality factor, a decrease in the scale factor of the gyroscope and its sensitivity;

2) gluing the piezoelectric elements creates an uneven distribution of stiffness around the circumference of the resonator, as a result of which the axes of the elastic wave do not coincide with the axes of arrangement of the piezoelectric elements, which leads to nonlinearity of the scale factor of the gyroscope and a decrease in its sensitivity, in particular to low angular rotational speeds.

The closest analogue of the claimed device is a sensitive element of a vibrating gyroscope (US patent No. 4644793), made in the form of a cylindrical glass, rigidly mounted on an elastic flat plate connected to a ceramic disk on which the electrode system is located.

The bending deformations of the membrane when an alternating excitation signal is applied to it are transmitted to the cylindrical cup and cause its radial vibrations around the axis, while the nodal points of radial vibrations move around the circumference of the cup due to the action of Coriolis forces.

The displacements of the nodal points are transmitted to the membrane on which the displacement sensors that record the displacement data are located.

The disadvantages of this device are:

1) the presence in the composition of the sensing element of the membrane, which is clamped along the outer contour and loaded with a cylindrical cup connected with it along its inner contour, leads to the fact that in the event of non-inertial influences (vibration, shock), membrane forms of vibrations may occur, the frequencies of which can coincide, or be close, with the main oscillation frequency of the cylindrical glass, and this, in turn, limits the sensitivity of the gyroscope during its operation and leads to significant measurement errors;

2) the installation of displacement sensors on the membrane contributes to the mismatch of the axes of the standing wave with the axes of location of the mentioned sensors, which also reduces the sensitivity of the gyroscope and the accuracy of measuring the angular velocity Ω.

The objective of the proposed solution is to increase the sensitivity and accuracy of the gyroscope by developing a new design of the sensitive element and the location of the piezoelectric elements, as well as simplifying its mechanical balancing.

The problem is solved in that in a sensitive element of a vibrating Coriolis gyroscope containing a thin-walled cylinder with a bottom, an element for attaching it to the base of the gyroscope and piezoelectric elements for exciting and picking up a signal, the cylinder is made with a thickened upper part - a ring resonator, the cylinder bottom is divided into sectors by means of many grooves located mainly symmetrically and mainly radially around the circumference from its center to the peripheral part of the bottom of the cylinder, while inside each th sector operate groove to be positioned therein a plurality of piezoelectric elements excitation and pickoff signal slots operate with the outer or inner side of the bottom, and further, the grooves forming sector, a (extend) on a side surface portion of the cylinder cavity.

The proposed design of the sensitive element makes it possible to achieve a more exact coincidence of the axes of the elastic wave with the axes of location of the piezoelectric elements (coordinate system associated with the piezoelectric elements), which simplifies the correction circuit of the standing wave and increases the sensitivity and accuracy of the gyroscope.

Mechanical balancing of the resonator is possible by reducing stiffness along the axes of the elastic suspension, since the unbalanced mass can be removed in the groove region by changing the groove width (by changing the stiffness of the sectors, the mass unbalance of the ring resonator can be compensated).

The claimed solution is illustrated by the drawings:

figure 1 presents the design of the sensing element,

figure 2 shows a cross section of the sensing element,

figure 3 presents the input and output of electrical signals supplied to the piezoelectric elements and removed from them,

figure 4 shows the distribution of the maximum nodal displacements of the sensing element during its rotation with the angular velocity Ω with the relative displacement scale.

The claimed technical solution can be implemented as follows.

The sensitive element is made of a thin-walled cylinder 1 with an annular resonator 2, made in the form of a cylindrical rim of length L with wall thickness H, and a cylindrical elastic suspension 3, consisting of a part of length l and wall thickness h and bottom 4, divided into sectors 5 by grooves 6 wide b ₂ .

The wall thickness h of the elastic suspension 3 is less than the wall thickness of the ring resonator 2, while the average radius R _{0 of the} different thickness cylinder 1 is the same.

Inside each sector 5, a groove 7 is made with a width of b ₁ to accommodate one or more piezoelectric elements 8 in it to excite the resonator and pick up the signal.

On the bottom 4, inside the cylinder 1 and coaxially with it, a pipe 9 with coaxial holes 10 and 11 is arranged, used for elastic fastening of the sensitive element to the base.

The pipe 9 is made with a hole of radius r and with an axisymmetric base surface B, necessary in the manufacture of the sensing element, and defining its axis.

The sensing element is connected to the base using a pipe 9 in a conical fit, which allows you to center the sensitive element relative to the base of the gyroscope.

The grooves 7 can be placed on both sides of the bottom 4, and the grooves 6 forming the sectors 5 can be located on a part of the side surface of the cylinder 1, in the region of the elastic suspension 3.

The proposed device can be used as follows.

From the generator block to the diametrically opposite piezoelectric elements 8A and 8E, a control signal is supplied in the form of a sinusoidal voltage Asin (ω ₀ t), where ω ₀ is the frequency of the alternating signal, equal to (or close to) the natural frequency of the main oscillation form of the sensitive element.

Due to the bending deformations of the bottom 4 of the sensing element, a bending moment occurs, which causes elliptical deformations of the elastic suspension 3 in the second mode of vibration, as a result of which a standing wave is excited in the sensing element with four nodal regions oriented along the piezoelectric elements 8A and 8E and 8G and 8C, and four nodal regions located along the piezoelectric elements 8B and 8F and 8H and 8D.

The signal is taken using piezoelectric elements 8G and 8C and 8H and 8D: the first of them are used to pick up signals from the antinodes of a standing wave, the second - to pick up signals from its nodes.

Since the piezoelectric elements 8 are arranged symmetrically around the circumference, it is possible that the axis of the nodes and the axis of the antinodes can mutually change.

When a gyroscope with an oscillating sensing element rotates around its central axis with a constant angular velocity Q, Coriolis forces arise that contribute to the displacement of the nodal regions of the standing wave around the circumference, as a result of which a signal proportional to the angular velocity appears on the piezoelectric elements 8B and 8F Ω, which enters the unit to generate a signal to compensate for the inertial displacement of the standing wave.

The compensation signal is output from the electronics unit as an output signal proportional to the measured angular velocity Ω.

With mechanical balancing of the sensitive element, its mass is changed by changing the width of the grooves.

Claims (4)

1. A sensitive element of a vibrating Coriolis gyroscope containing a thin-walled cylinder with a bottom, an element for attaching it to the base of the gyroscope and piezoelectric elements for exciting and removing information, characterized in that the cylinder is made with a thickened upper part - a ring resonator, the cylinder bottom is divided into sectors by means of many grooves while inside each sector, a groove is made with the possibility of placing the piezoelectric elements of the excitation and signal collection. 2. The sensing element according to claim 1, characterized in that the grooves are made on the outside of the cylinder bottom. 3. The sensing element according to claim 1, characterized in that the grooves are made on the inside of the cylinder bottom. 4. The sensing element according to claim 1, characterized in that the grooves are extended on the side surface of the cylinder.

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