RU2423668C1 - Detecting element of micromechanical gyroscope - Google Patents

Abstract

FIELD: physics. ^ SUBSTANCE: detecting element of the micromechanical gyroscope has a base, a rectangular inner frame, a centre joined by four rigid tie-rods with an inner frame, four movable masses, each joined to the centre by two elastic inverted L shaped suspensions, and with the inner frame by six elastic inverted L shaped suspensions, an inner frame joined with the inner frame by four joints. The element also has jumpers which join the inverted L shaped suspensions with the inner frame and rigid tie-rods lying at corners where the inverted L shaped suspensions are interfaced with the inner frame and rigid tie-rods. The inner frame with four rigid tie-rods has an X shaped cross section. ^ EFFECT: high accuracy of the gyroscope. ^ 2 dwg

Description

The invention relates to measuring technique and can be used in vibration-type integrated gyroscopes.

A known element of a microelectromechanical gyroscope containing four moving masses made on a silicon plate [1]. The elastic suspensions of the moving masses are located crosswise and are fixed at the intersection point on the string along which the measured angular velocity acts. Forced vibrations of the moving masses are set in the plane of the plate, and the directions of motion are carried out in pairwise opposite directions. As a result of oscillations, the mechanical stresses at the fixing point are always zero, which increases the quality factor of the sensitive element. The arising alternating Coriolis forces act on the moving masses in the direction perpendicular to the plane of the plate.

A disadvantage of the known device is its low accuracy, due to the fact that the excited oscillations occur in the plane of the sensing element, and the measuring oscillations are perpendicular to this plane, therefore, it is difficult to ensure the condition of the resonant tuning in both vibration planes, because stiffnesses are determined by different technological factors, and for many materials (for example, silicon) and various physical properties.

Also known is a sensitive element of a micromechanical gyroscope, which contains a rigid outer frame and a center connected to a fixed base and frame by four supporting rigid stretch marks located crosswise [2]. Between the frame and the center, on thirty-two L-shaped suspensions, four identical moving masses are suspended, each of which consists of five square plates. The elastic suspensions are elongated in cross section, their elongated directions are perpendicular to the plane of the moving masses. On one side of each of the suspensions and stretch marks are conductors that are welded to the electrical pads located in the center of fixing the sensing element to a fixed base. Moving masses can fluctuate only in one plane, which excludes the influence of cross angular velocities.

The disadvantage of this device is that this fixing system requires careful balancing of the sensitive element, since during the manufacturing process of the latter, due to the heterogeneity of the etching, as well as due to the uneven thickness of the single-crystal silicon wafers from which sensitive elements of micromechanical gyroscopes are made, mass imbalance and heterogeneous stiffness of suspensions of the corresponding masses, which leads to a sharp decrease in the quality factor of the system. And only a very time-consuming balancing can allow to reduce to zero all undesirable moments. The closest in technical essence is a sensitive element of a micromechanical gyroscope containing a base, a rectangular inner frame, a center connected by four rigid stretch marks with an internal frame, four movable masses, each of which is connected to the center by two elastic L-shaped suspensions, and six by an internal frame elastic L-shaped suspensions, the sensing element further comprises an external frame connected to the internal frame by four jumpers located along the axes of symmetry of the senses an active element, one jumper on each side of the frames, and connected to the base through four mounting pads located in the corners of the outer frame [3]. The disadvantage of this device is that a rectangular frame with four stretch marks is a source of energy loss for this oscillatory system, since the deformation forces at the fastening point of the L-shaped suspensions and the inner frame and stretch marks are not completely zero and deform the frame and stretch marks. Increasing the width of the inner frame and stretch marks can reduce stress to zero. However, this significantly increases the dimensions of the sensitive element, that is, it is impossible to ensure the maximum quality factor of the oscillatory system, which determines the accuracy of the device as a whole.

Another significant drawback is that in the prototype there is no balancing. And since due to the heterogeneity of the etching, an imbalance of masses and heterogeneity of the stiffness of the suspensions of the corresponding masses occur, which leads to a different frequency of the oscillatory circuits and an additional decrease in the quality factor of the system.

The problem to which the invention is directed, is to increase the accuracy of the micromechanical gyroscope.

This problem is solved due to the fact that the sensitive element of the micromechanical gyroscope contains a base, a rectangular inner frame, a center connected by four rigid extensions with an internal frame, four movable masses, each of which is connected to the center by two elastic L-shaped suspensions, and with the inner frame with six elastic L-shaped suspensions, the outer frame connected to the inner frame by four jumpers, the inner frame with four rigid extensions is made with an X-shaped cross section and up to additionally contains jumpers connecting the L-shaped suspensions with the inner frame and rigid extensions located in the corners, the places of interfacing of the L-shaped suspensions with the internal frame and rigid extensions.

The quality factor of the oscillatory system of the sensitive element is enhanced by the fact that the claimed sensitive element has an internal frame with four rigid stretch marks in the form of an X-shaped profile oriented in the direction (111) of the crystallographic lattice of single-crystal silicon. This orientation of the torsion with respect to the axes of the crystallographic lattice of silicon provides the greatest rigidity to bending deformations in comparison with other profiles with the same overall dimensions. Thus, the energy loss of this oscillatory system is zero, the quality factor of the proposed sensitive element is quite high compared to the prototype, which, of course, increases the measurement accuracy.

The increase in accuracy is due to the fact that in the places where the G-hangers are interfaced with the inner frame and extensions, jumpers are additionally made connecting the L-shaped suspensions with the internal frame and extensions. Jumpers bypass the L-shaped suspensions, increasing their rigidity. By measuring the eigenfrequencies of the individual loops of the oscillatory system in various directions in a known manner, by removing the jumpers, the different frequencies of both loops are regulated and reduced to zero. Thus, natural frequencies are reduced with great accuracy, providing high sensitivity and accuracy.

Figure 1 shows a top view of the sensitive element of the micromechanical gyroscope. Digital positions in the drawings have the following notation:

1 - outer frame;

2 - moving mass (total 4 masses);

3 - inner frame of the sensing element;

4 - jumpers for balancing;

5 - center;

6 - rigid stretching (four stretches in total);

7 - L-shaped elastic suspension (thirty-two in total).

All four movable masses 2 are the same and each consists of five square plates, as shown in the drawing of figure 1. The outer frame 1 is connected to the inner frame 3 by hard transitions, which are located along the symmetry axes of the sensing element. All 32 elastic suspensions are the same, have great rigidity in the direction perpendicular to the plane of the sensing element (z axis), and low rigidity in the direction of the x and y axes. In this regard, the moving masses 2 have the ability to move only in the plane of the plate. At the corners of the outer frame 1 there are four pads for rigidly fastening the outer frame 1 to a fixed glass base (not shown in the drawing). Stretch marks 6 connect the center 5 of the sensing element to each of the four sides of the inner frame 3. Shunt jumpers 4 connect the L-shaped suspensions 7 to the inner frame 3 and rigid stretch marks 6 located in the corners of the junctions of the G-suspensions 7 with the inner frame 3 and rigid stretch marks 6. Figure 2 shows the profile of the inner frame and stretch marks.

The sensitive element of the micromechanical gyroscope works as follows.

When applying to the power device, the moving masses 2 begin to oscillate in pairs along the X axis in antiphase to each other at the resonant frequency. When the sensitive element rotates about the Z axis, Coriolis acceleration begins to act on the moving masses 2, the direction of which depends on the direction of the linear velocity direction, and the value is determined by the magnitude of the angular velocity. Coriolis acceleration is converted into an alternating Coriolis force, which moves each moving mass 2 in the direction perpendicular to the current linear excitation velocity and the external angular velocity acting, while an emf proportional to the external angular velocity is induced in the displacement transducer.

Information sources

1. US Patent No. 5952572, issued September 14, 1999, IPC G01P 9/00,

2. RF patent No. 2222780, published on January 27, 2004. IPC G01C 19/56, G01P 9/04.

3. RF patent No. 2301969, published on June 27, 2007. IPC G01C 19/56, G01P 9/04 (prototype)

Claims (1)

A micromechanical gyroscope sensitive element containing a base, a rectangular inner frame, a center connected by four rigid extensions to the inner frame, four movable masses, each of which is connected to the center by two elastic L-shaped suspensions, and with an internal frame - six elastic L-shaped suspensions , an outer frame connected to the inner frame by four transitions, characterized in that it further comprises jumpers connecting the L-shaped suspensions with the inner frame and rigid extensions, ra laid in the corners of the ground mating T-shaped hangers with the inner frame and rigid extensions and the inner frame with four rigid braces made with an X-shaped cross section.

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