RU2697442C2 - Device for determining inertial characteristics of elongated articles - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: invention relates to machine building and can be used for determining inertial characteristics of articles. Device comprises a base, a body mounted on it, a platform arranged on it, a resilient device and a platform turning assembly connecting the body and the platform. In upper part of housing there is a system for recording parameters of torsional vibrations, housing and platform are equipped with vertical groove, in plane of symmetry of which is movably arranged alignment device, installed with possibility of rotation around first axis located in plane of symmetry of slot, and around the parallel to the axis located at a given distance from the platform axis, perpendicular to the first axis. Housing is made of rock of solid rocks and is equipped with aerostatic step-bearings, interacting with platform, and alignment device is equipped with installed with possibility of movement relative to each other, in axial direction, rings with conical support platforms for placement of tested article.

EFFECT: technical result is higher accuracy of determination of unknown values and reliability of operation.

1 cl, 4 dwg

Description

The invention relates to mechanical engineering and can be used to determine the inertial characteristics of products.

A device of this type is known from the invention according to the patent of the Russian Federation No. 2017103 G01M 1/10 and contains a housing mounted on the base, an oscillating system placed in it, made in the form of a platform connected by a torsion bar with the housing, a faceplate for securing the product, a node for turning the faceplate relative to the vertical axis parallel the axis of the platform and the node of rotation of the faceplate relative to the inclined axis, and the faceplate itself is made rotatable relative to the axis coinciding with the axis of the platform. This device is taken as a prototype.

The disadvantage of this device is the low accuracy of measuring the coordinates of the center of mass relative to the longitudinal axis of extended products due to the need to place the product above the platform and cantilever fix it on the faceplate, which causes deformations of the power elements of the supporting structures and reduces the accuracy of positioning of the product. In addition, the cantilever fixing on the platform and the performed positioning scheme of the product, when determining the period of torsional vibrations, do not provide the necessary rigidity and stability of the aerostatic suspension, which also reduces the accuracy of measurements of the period of torsional vibrations and leads to additional errors in determining the inertial characteristics.

The claimed invention solves a technical problem aimed at improving the accuracy of determining the inertial characteristics of extended products and improving the reliability of the device.

The necessary technical result is obtained due to the fact that in the known device for determining the inertial characteristics of extended products in the upper part of the housing there is a system for recording torsional vibration parameters, the housing and the platform are equipped with a vertical groove in the plane of symmetry of which a centering device is mounted movably mounted for rotation around the first axis located in the plane of symmetry of the groove and around the parallel parallel to the axis of the platform axis perpendicular to the first axis, the casing is made of solid rock stone and is equipped with aerostatic thrust bearings interacting with the platform, and the centering device is provided with rings with conical supporting surfaces mounted relative to each other in axial direction to accommodate the test product.

These significant distinguishing features, together with the known features, make it possible to increase the accuracy of determining the inertial characteristics of extended products by increasing the accuracy of positioning of the product, reducing deformations of the bearing elements of the positioning system as a result of eliminating the cantilever loads on it from the test product, stabilizing torsional vibration parameters, by increasing stiffness and thermal stability of aerostatic suspension elements provided by the implementation hulls made of solid rock and the installation of separate aerostatic thrust bearings.

The analysis of publicly available sources of information on the prior art did not allow to identify a technical solution identical to the declared one, on the basis of which a conclusion is made about the unknownness of the latter, i.e. compliance presented in this application of the invention with the criterion of "novelty."

A comparative analysis of the claimed solution with known technical solutions revealed that the presented set of distinctive features is unknown to a person skilled in the art and does not follow explicitly from the prior art, on the basis of which it is concluded that the invention presented in this application meets the criterion of "inventive step" .

To explain the invention, a specific example of its implementation is given below with reference to the accompanying drawings, in which: FIG. 1 depicts the proposed device; FIG. 2 - the same, top view; FIG. 3 and FIG. 4 - the position of the projections of the center of mass on the horizontal plane at various angles of rotation and movement of the faceplate.

The device comprises a housing 2 mounted on the base 1, an oscillating system mounted on it, including a platform 3 connected by a torsion 4 with a diaphragm 5 mounted on the housing 2.

The platform 3 is supported on the casing 2 by means of three aerostatic thrust bearings 6, 7, 8 and is fixed on the torsion axis by means of a radial aerostatic bearing 9. The casing 2 and the platform 3 are provided with a vertical groove 10 in which the centering device 11 is made in the form of a cylindrical shell 12, with a fixed 13 and a movable spring-loaded ring 14, provided with a tapered bearing surfaces 15 and 16, on which the product 17 is installed. The alignment device 11 is mounted on the inner ring 18 of the support-turn the other device 19, the outer ring of which 20 is equipped with a latch of the inner ring 21. The pivoting device 19 is mounted on the slider 23 with the latch 23, equipped with a latch 24, guides 25, 26, 27 and a wedge clamp 28. In the upper part of the housing 2, both side of the U-shaped groove 10, the node of rotation of the platform 29 and the registration system of the parameters of torsional vibrations 30 are placed.

A device for determining the inertial characteristics of extended products works as follows.

In the initial position, the torsion 4 of the oscillatory system is twisted by an angle of 1 ... 3 degrees relative to the axis OX and the associated platform 3, with the help of the turning unit 29, is held cocked, the centering device 11 is installed in a vertical position and held by the latch 24, the slider 23 is in the left extreme position and fixed with a wedge clamp 28.

The product 17 is installed in the centering device 11 and fixed by a spring-loaded ring 14 relative to the axis OX so that the Z axis lies in the plane of symmetry of the groove 10 and is directed from the axis of the platform — the initial position of the product.

Compressed air is supplied to the aerostatic thrust bearings 6, 7, 8 and the radial bearing 9, they include a system for recording torsional vibration parameters 30, on command of which they supply compressed air to the rotation unit 29, which releases the platform 3. Platform 3 together with the product 17 begins to make free torsional vibrations.

The torsional vibration period T1 is measured. Next, using the rotary support device 19, the centering device 12 with the product 17 is rotated sequentially 90 °, 180 °, 270 ° clockwise, each time fixing it with the lock 21 and starting the measurement cycle, take readings of the oscillation periods of the platform with the product, respectively T2 , T3, T4.

In FIG. 3 shows the projections of the center of mass of the product and their position relative to the axis of oscillation in the four described positions.

After the described operations, the inner ring of the pivoting device 19 is rotated 90 degrees, fixed with a latch 21, while the product is in its original position, the latch 24 is opened, the centering device 11 with the product 17 is set to a horizontal position and again fixed with a latch 24, the periods are measured oscillations T5, open the wedge clamp 28, move the slider to the right extreme position, fix the clamp 28 and measure the period of oscillations T6, after which the slider is again returned to the left edge its position and fixed clamp 28. Turn the inner ring of positioner 45 and 90 degrees every time its locking retainer 21 and starting measurement cycle, take readings periods platform vibrations with the product of T7, T8. The latch 24 is opened, the centering device 11 with the product 17 is set at an angle of 45 degrees to the horizon and again fixed with the latch 24, the oscillation periods T9 are measured, then the inner ring of the slewing ring is rotated 90 degrees, fixed with the latch 21 and the oscillation period is measured T10

Using the well-known dependencies between the period of torsional vibrations of a unifilar suspension and its moment of inertia (Gernet M.M. and Ratobylsky V.F. Determination of moments of inertia. M .: Mechanical Engineering, 1969), we determine the values of the moments of inertia of the product relative to the axis of the unifilar suspension by the formulas:

Where:

J _oi is the moment of inertia of the tool, relative to the axis of oscillation of the platform;

J _ui is the moment of inertia of the product, relative to the axis of oscillation of the platform;

i - serial number of parameters corresponding to a given position of the product.

The moments of inertia of the tool relative to the axis of oscillation of the platform are constant for this device and are determined when it is verified through the periods of oscillation of the tool and the periods of oscillation of the tool with a standard, the moments of inertia of which are known by a formula similar to the previously given.

Where:

J _oi - moments of inertia of the equipment relative to the axis of oscillation of the platform;

J _{ei are the} moments of inertia of the standard about the same axis. The determination of the coordinates of the center of mass of a product is based on the use of the Huygens-Steiner theorem

Where:

J _Цi is the moment of inertia of the product relative to the central axis passing through the center of mass and parallel to the axis of torsional vibrations;

M is the mass of the product;

Lс is the distance between the central axis of the product and the axis of oscillation of the platform.

In the first four measurements, the product rotates around a fixed longitudinal axis OX parallel to the axis of the unifilar suspension defined by the reference base surfaces 15, 16 and taking into account that in accordance with FIG. 3:

Y = Y ₁ = Y ₃ , Z = Z ₂ = Z ₄ you can write:

J _u1 = J _q1 + M ((L + Z) ² + Y ² )

J _u2 = J _q1 + M ((LY) ² + Z ² )

J _u3 = J _q1 + M ((LZ) ² + Y ² )

J _u4 = J _q1 + M ((L + Y) ² + Z ² )

From the system of 4 equations we find:

In the fifth and sixth dimensions, the product moves without changing its spatial orientation relative to the axis of oscillation, therefore, we can write:

J _u5 = J _q5 + M (X ² + Y ² )

J _u5 = J _q5 + M ((X + a) ² + Y ² )

Where:

and - the value of the horizontal displacement of the slider 23

From the system of equations we get:

To determine the components of the inertia tensor, we use six moments of inertia: three relative to the coordinate axes (J _XX , J _YY , J _ZZ _-positions 1,5,8, respectively) and three relative to the bisectors of angles between the positive directions of the coordinate axes (J _YZ , J _ZX , J _XY position 7,9,10 respectively). Knowing the components of the inertia tensor, we compose a vector equation:

where J _X⋅Y , J _Z⋅X , J _Y⋅Z - centrifugal moments of inertia are determined by the formulas:

Solving the vector equation, we find three main moments of inertia:

J _Ch . ₁ , J _Ch . ₂ , J _Ch . ₃ .

The main guides of the cosines are determined from the system of equations:

together with the equation

Thus, the use of the proposed device for determining the inertial characteristics in comparison with the prototype, improves the accuracy of determining the desired values and the reliability of the device due to the fact that in the upper part of the housing there is a system for registering torsional vibration parameters, the housing and the platform are equipped with a vertical groove in the symmetry of which the centering device is movably placed, mounted to rotate around the first axis located in the plane of symmetry a groove, and around a parallel axis located at a predetermined distance from the platform axis, perpendicular to the first axis, the body is made of solid rock stone and equipped with aerostatic thrust bearings interacting with the platform, and the centering device is equipped with axial mounted to move relative to each other in axial direction, rings with tapered abutment surfaces to accommodate the test article. All this improves the positioning accuracy of the product by reducing the deformation of the bearing elements of the positioning system as a result of eliminating the cantilever loads on it from the tested product, stabilizes the torsional vibration parameters due to the increased rigidity and thermal stability of the aerostatic suspension elements provided by the implementation of the body of stone rock, and the installation of separate aerostatic thrust bearings, which creates a technical and economic effect.

Claims (1)

A device for determining the inertial characteristics of extended products, comprising a base, a housing mounted on it, a platform mounted on it, elastic means and platform connecting the body and platform, and a platform rotation unit, characterized in that the torsional vibration parameters registration system, the body and the platform are located in the upper part of the body equipped with a vertical groove, in the plane of symmetry of which a centering device is movably mounted, mounted to rotate around the first axis, located in the plane of symmetry of the groove, and around the parallel axis located at a given distance from the platform axis, perpendicular to the first axis, the body is made of solid rock stone and equipped with aerostatic thrust bearings interacting with the platform, and the centering device is equipped with movable relative to each other, in the axial direction, rings with conical bearing pads to accommodate the test product.

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