RU2660319C1 - Method of automatic combining of the test center of a test object with test object axis of rotation at testing on a test stand - Google Patents

Abstract

FIELD: testing equipment.

SUBSTANCE: method refers to testing equipment. When installing a test object (hereinafter referred to as TO), four strain gage load-measuring cells transmit pressure signals to the test stand to the device for reading information from sensors of load-measuring strain gage, where the difference of sums of discrete codes is calculated. Device for issuing control commands to the linear mechanism gives control signals to a linear mechanism that moves continuously or discretely, depending on the value of the difference of sums of discrete codes, a movable carriage along the central axis of the TO. As a result, the center of mass of the TO is automatically aligned with the TO axis of rotation.

EFFECT: technical result consists in simplifying the design, reducing the weight and size characteristics, reducing the loads on electric motors during testing.

1 cl, 1 dwg

Description

The method relates to testing equipment and can be used when testing a long, large-sized test object (OI) up to 7 m long and weighing up to 2 tons with flowable contents, the center of mass of which is located on the central axis of the OI.

The technical result of the proposed method for automatically aligning the center of mass of the OI with the axis of rotation of the OI when conducting tests on the test bench is to reduce the loads on the electric motors that ensure the rotation of the OI when testing on the test bench.

A search by the applicant for known patent and scientific and technical materials did not find a similar solution suitable for consideration as a prototype.

The method of automatically combining the center of mass of the test object (OI) with the axis of rotation of the test object during testing on the test bench consists in fixing the OI in the lodges of the test bench, reading information from load cell strain gauges, calculating the difference in the sums of discrete codes, comparing the difference in the sums of discrete codes with threshold values of the difference of the sums of discrete codes, setting depending on the value of the difference of the sums of discrete codes on the linear mechanism of the continuous stand the explicit or discrete principle of moving the OI along the axis of the test bench until the center of mass of the OI is aligned with the axis of rotation of the OI.

The implementation of the method of automatically combining the center of mass of the test object with the axis of rotation of the OI during testing on the test bench is shown in the drawing, which shows:

1) frame of the test bench;

2) lodgements;

3) staples;

4) load cell strain gauges;

5) mobile carriages;

6) platform;

7) supports of the test bench;

8) linear mechanism;

9) a device for issuing control commands to a linear mechanism;

10) a device for reading information from load cell strain gauge sensors;

11) test object;

The lodgements 2 are installed on the frame 1, in the brackets 3 of which the OI 11 is fixed for rotation relative to its own central axis. The platform 6, which is the stationary bearing part of the test bench, is connected to the supports of the test bench 7, on which load cells are load cells 4. The device 9 is designed to power the sensors load cell strain gauge 4, the issuance of control commands to the linear mechanism 8, which is designed for longitudinal movement of the frame 1 together with the OI 11. The device 10 is designed to read information from load cell strain gauges and issue test control commands with an electric motor stand according to the incoming information from load cell strain gauges 4.

The power of the electric motor turning OI 11 is determined by the formula [General physics course, volume I. Mechanics, vibrations and waves, molecular physics / I.V. Saveliev - M.: Publishing House "Science", Main Edition of Physics and Mathematics, 1970 - 517 p. (p. 85)]:

where P is the engine power;

M _mot - motor torque forces;

ω _mot - set engine speed.

The moment of electric motor forces is determined by the formula [Course design of machine parts: Textbook. allowance for students of engineering special technical schools / S.A. Chernavsky, K.N. Bokov, I.M. Chernin et al. - 2nd ed., Revised. and add. - M.: Mechanical Engineering, 1988 .-- 416 p.: Ill. (p. 386)]:

where M _s - the moment of forces applied to the axis of rotation of the OI;

η - engine efficiency;

n is the gear ratio of the gearbox.

The moment of forces applied to the axis of rotation of the OI 11 is determined by the formula [Physics: Textbook. HELL. Ivliev - St. Petersburg: Publishing House "Lan", 2008. - 672 pp., Ill. - (Textbook for high schools. Special literature) (p. 43)]:

where J _s - dynamic moment of inertia applied to the axis of rotation of the OI;

a _r is the radial acceleration;

M _article - static moment applied to the axis of rotation of the OI.

The static moment at the point of the axis of rotation of OI 11 is determined by the formula [General physics course, volume I. Mechanics, vibrations and waves, molecular physics / I.V. Saveliev - M.: Publishing House "Science", Main Edition of Physics and Mathematics, 1970 - 517 p. (p. 130)]:

where m is the mass of the OI;

g is the acceleration of gravity;

d is the shoulder length from the center of mass of the OI to the axis of rotation of the OI.

The dynamic moment of inertia applied to the axis of rotation of the OI 11 is determined by the formula [Physics: Textbook. HELL. Ivliev - St. Petersburg: Publishing House "Lan", 2008. - 672 pp., Ill. - (Textbook for high schools. Special literature) (p. 45)]:

where, J _cm - the moment of inertia applied to the center of mass of the OI.

Since all values, except for the length of the shoulder from the center of mass of the OI 11 to the axis of rotation of the OI 11 d, are preset, to reduce the required power of the electric motor used to rotate the OI 11, it is necessary to minimize the value of the length of the shoulder from the center of mass of the OI 11 to the axis of rotation OI d. This is achieved by combining the center of mass of OI 11 with the axis of rotation of OI 11, while the length of the shoulder from the center of mass of OI 11 to the axis of rotation of OI 11 will be infinitesimal, i.e. d tends to zero.

The combination of the center of mass of the OI 11 with the axis of rotation of the OI 11 reduces not only the loads on the electric motor during testing, but also the overall dimensions of the test bench.

After fastening the OI 11 on the cradles 2 of the stand using brackets 3, the automatic alignment of the center of mass of the OI 11 with the axis of rotation of the OI 11 is carried out as follows: the device 10 reads signals from the strain gauge load cells 4 corresponding to the pressure value of the supports 7 on the ground. By the formula (6), the difference of the sums of discrete codes is calculated:

where dN is the difference of the sums of discrete codes;

N ₁₁ - value from the front left strain gage load cell;

N ₁₂ - value from the front right strain gage load cell;

N ₂₁ - value from the rear left strain gage load cell;

N ₂₂ - value from the rear right strain gage load cell.

Mobile carriages 5 provide the movement of the OI 11 along the horizontal axis. With this movement, the fluid content of the OI 11 oscillates, displacing the center of mass of the OI 11, which greatly complicates the process of finding the center of mass of the OI 11, since the values from the strain gauge load cells continuously change until the fluid content of the OI 11 is at rest. Since OI 11 is large-sized, it is irrational to carry out the movement discretely constantly, waiting until the fluid contents are at rest, to accurately determine the difference value of the sums of discrete codes dN. In this regard, two ranges of values of the difference of the sums of discrete codes dN are used, which defines the principle of moving the OI 11 to combine the center of mass of the OI 11 with the axis of rotation of the OI 11: continuous or discrete movement of the OI 11 along the horizontal axis of the test bench. The ranges of the difference values of the sums of discrete codes dN are determined by the threshold values of the difference of the sums of discrete codes dN _por1 and dN _por2 , while the absolute value | dN _por1 | greater than | dN _por2 |. The threshold value of the difference of the sums of discrete codes dN _por1 is set for a rough search of the center of mass of the OI 11. The threshold value of the difference of the sums of discrete codes dN _por2 is set for the exact combination of the center of mass of the OI 11 with the axis of rotation of the OI 11.

The values of N ₁₁ , N ₁₂ , N ₂₁ , N ₂₂ from the strain gauge load cells 4 in the device issuing control commands 9 are received continuously. The comparison of the difference value of the sums of discrete codes dN with the threshold values of the difference of the sums of discrete codes dN _{pore 1,2} occurs in the device 9.

At the first stage of automatic alignment of the center of mass of the OI with the axis of rotation of the OI 11, the OI 11 continuously moves along the horizontal axis until the condition is satisfied:

In this case, the device 9 transmits a control signal to the linear mechanism 8, which carries out continuous movement of the OI in the horizontal axis parallel to the central axis of the OI, with dN greater than zero - the movement of the OI 11 occurs forward, with dN less than zero - backward.

In the second stage, after condition (7) is fulfilled, a discrete movement of the OI 11 along the horizontal axis occurs until the condition:

The device 9 transmits a control signal to a linear mechanism 8, which performs discrete movement of the OI in the horizontal axis parallel to the central axis of the OI 11. The control signal in this case is transmitted in a pulsed manner. The discrete movement of OI 11 is necessary to reduce the influence of fluctuations in the fluid contents of OI 11 on determining the difference value of the sums of discrete codes dN, since during a pause the fluid contents of OIs are set to rest and the value of the difference of the sums of discrete codes dN is determined with the least error. In this regard, the pulse duration of the control signal is selected less than the pause value.

When condition (8) is fulfilled, the center of mass of the OI 11 is aligned with the axis of rotation of the OI 11 and the device 9 stops transmitting the control signal to the linear mechanism 8.

By combining the center of mass of the OI with the axis of rotation of the OI, the power of the electric motors is significantly reduced, which ensures the rotation of the OI along the roll and pitch.

Claims (1)

The method of automatically combining the center of mass of the test object (OI) with the axis of rotation of the test object during testing on the test bench, which consists in fixing the OI in the lodgements of the test bench, reading information from load cell strain gauges, calculating the difference in the sums of discrete codes, comparing the difference in the sums of discrete codes with threshold values of the difference of the sums of discrete codes, setting depending on the value of the difference of the sums of discrete codes on a linear mechanism of the stand first la continuous, then the principle of the discrete movement along the axis OI test stand until alignment with the center of mass OI OI rotation axis.

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