SU1374256A1 - Apparatus for reproducing dependence of friction force on velocity and predisplacement of friction couples - Google Patents

Abstract

The invention relates to the field of analog computing and is intended for use in the simulation of mechanical systems with friction pairs. The purpose of the invention is to increase accuracy. For this purpose, an integrator and a restriction setting unit are entered into the device. Applying to the device input a signal proportional to the relative speed of sliding of the pairs of friction creates the opportunity to receive at the output a signal proportional to the forces of friction, depending in motion on the direction and magnitude of the relative speed of the elements of the pair, and in relative rest from their prior displacement. 3 il. i (L

Description

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ABOUT)

The invention relates to analog computing and is intended for use in modeling mechanical systems with friction pairs, frictional forces of which depend on the direction and magnitude of the relative velocity of the elements of a pair, and in relative rest from

to The integrator is configured on an operational amplifier 36 and includes a capacitor 37 and a resistor, 38. The voltage from the input of the device 1 is fed to the input of the inverter 3 and at the same time to the inputs of the first and second blocks 4 and 5 of the limitation, to the reference inputs of which a constant reference of their preliminary bias is received taking into account the Q buckle from sources 30 and 33. From the output of the inverter 3 the voltage is applied to the first input of the integrator 20 and simultaneously to the inputs of the first and second blocks 12 and 13, to the reference inputs of which a constant reference voltage is supplied from sources 34 and 31. From the output of the integrator 20, the voltage goes to its second input directly but through the resistor 27, energy dissipation in the process of elastic-plastic deformations of the contact surfaces of the friction pair with relative micro-movements of its elements within the pre-displacement zone.

The purpose of the invention. - Improving accuracy.

FIG. 1 shows a schematic diagram. The integrator is configured on an operational amplifier 36 and includes a capacitor 37 and a resistor, 38. The voltage from the input of the device 1 is fed to the input of the inverter 3 and at the same time to the inputs of the first and second blocks 4 and 5 of the limit, the reference inputs of which receive a constant reference voltage from sources 30 and 33. From the output of the inverter 3, the voltage is applied to the first input the integrator 20 and at the same time the inputs of the first and second blocks 12 and 13, whose reference inputs receive a constant reference voltage from sources 34 and 31. From the output of the integrator 20, the voltage goes to its second input directly through the resistor 27,

roystva; in fig. 2 shows the dependences of the force20, the stability of its operation in the dynamic of movement F (V) versus the speed of the relative modes, and the first slip-on entrance of friction pairs reproduced by the device; fig. 3 - reproducible by the device through feedback through the third and fourth blocks 21 and 22 restrictions. On the pivot points of the third 21 and fourth between F (S) and S, taking into account the late 25 22 limiting blocks through the first

thirty

35

40

between them, built for the case of small changes in the relative velocity V (t); 0 elements of a pair of friction training them within the zone of preliminary displacement. The device contains an input 1 and set the relative speed of the friction pairs, output 2 according to the friction force, inverter 3, first 4 and second 5 limiting blocks that simulate the maximum amount of change in friction force on the semi-dry friction section, made on diodes 6 and 7 and resistors 8, 9 and 10, 11, the first 12 and the second O nonlinearity block of the insensitivity type, which simulate the change in the velocity of the end friction y4acTjca, performed on diodes 14, 15 and resistors 16, 17 and 18, 19, the integrator 20, the third 21 and the quarter 22d limiting blocks, modeling change Ichin frictional force resting made on diodes 23 and 24 and resistors 25 and 26, a feedback integrator 27, a resistor, resistive matching ". the tori 28 and 29, the second, first and third sources 30, 31 and 32 of the positive reference voltage, the second, the first and the third sources 33, 34 and 35 of the negative reference voltage, proportional to the maximum value of the change in friction force on the half dry friction and maximum friction strength

 the stability of its operation in dynamic modes, and the first input

feedback through third and fourth limiting blocks 21 and 22. On the reference points of the third 21 and fourth

five

0

.

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and the second matching resistors 28 and 29 are supplied with a constant reference voltage from sources 32 and 35, while the voltage is simultaneously applied to these points from the outputs of the first limiting unit 4 and the first non-linearity type 12 non-linearity unit and from the outputs of the second limiting unit 5 and the second block 13 nonlinearity type deadband.

As a result, the output of the integrator 20, i.e. At the output of the device, a voltage is formed corresponding to a family of falling characteristics such as a falling-increasing dependence of the friction force in movement on the direction and magnitude of the sliding speed of the pair elements (figure 2, graph 1), and in relative rest from their preliminary displacement taking into account the dissipation energy in the process of elastoplastic deformations of the contact surfaces of a friction pair with - relative micro displacements of its elements within the preliminary displacement zone (Fig. 3a).

To reproduce the humpback characteristics of the increasing-falling type (Fig. 2, graph 2), it is necessary to swap the first limiting block 4 with the second non-linearity block 13 of the dead band type in the source circuit (Fig. 1), and the second limiting block 5 with the first block 12 deadband type nonlinearities.

To reproduce the falling characteristics of the type of falling-falling (fig. 2, graph 3), it is necessary to install an inverter 3 immediately before the integrator 20.

For playing humpback

characteristics of the type of increasing and increasing (Fig. 2, graph 4) it is necessary to install the inverter 3 at the input of the device, connect the inputs of the first 12 and second 13 nonlinearity blocks to the output zone of the second 5 and first 4 blocks of the limit to its output. The slope of the characteristics is determined by the value of the resistors own resistance

F (V) F (SjTFnc (V) ± F, (V) with lS (t) bS, V (t) fO;

fKncV (t) with IV (t) |

Fnc (v)

JK.) AT | UN I IV (t) l;

Goprio | Y (1) and | Y, 1;

(t) - | VJsignV (t) npH IVH IV (t) l.

de K, is the stiffness coefficient of the elastic component of the preliminary displacement; - K is a coefficient characterizing the inelastic component of the preliminary displacement, proportional to the friction force, reflecting by its value 0 energy dissipation in the process of elastoplastic deformation of the contact surfaces in relative rest of the elements of the friction pair, expressed in the delay between the friction force F (S) and preliminarily displaced S (t); tS - maximum preliminary

a displacement corresponding to, eg, a limit quiescent state before the start of movement; F (S.) Is the extreme (maximum or minimum) value of the rest friction force before the start of movement; .

FHC (V) - the component of friction

on the section of semi-dry friction before the start of the boundary friction;

55

and diodes included in the device.

The device makes it possible to reproduce the following dependence of the friction force F (t): in motion, on the direction and magnitude of the relative velocity V (t) of the elements of the friction pair; in relative rest, from the preliminary displacement S (t) of these elements, taking into account the energy dissipation in the process of elastoplastic deformations of the contact surfaces of the pair at relative micro-displacements of its elements within the preliminary displacement zone:

in relative rest, the pairs F (S) (t) -KpF (S) dt, S (t) JV (t) dt, with -8 „S (t) .S V (t)« 0.

in relative motion of steam

- 0 5

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t F, (V) is the component of the friction force at the site of semi-liquid friction; tV, iVk speeds corresponding to

the beginning and the end of the boundary friction area;

K, the proportional coefficients of the linear dependences (V) and F. (V).

Claims (1)

Invention Formula A device for reproducing the dependence of friction force on speed and preliminary displacement of friction pairs containing the first and second blocks of non-linearity such as deadband, first, second and third limiting blocks, first, second and third sources of positive reference voltage, first, second and third sources of negative a reference voltage and an inverter, the input of which is connected to the input of a relative speed reference of the friction pairs of the device, and the output of the inverter is connected to the inputs of the first and second blocks nonlinearity type of dead band, the reference inputs of which are connected respectively to the outputs of the first source of negative and first sources, positive reference voltage, the inputs of the first and second limiting blocks are connected to the input of the reference speed of the device friction pairs, and the reference inputs of the first and second limiting blocks connected, respectively, to the outputs of the second source of positive and first sources of positive reference voltage, the outputs of the first and second limiting blocks Combined, respectively, with the outputs of the first and second nonlinearity blocks of the dead zone type; the reference input of the third limiting block is connected to the output FIG. /. The third source of positive reference voltage, characterized in that, in order to increase accuracy, an integrator and a fourth limiting unit are entered into it, the integrator input is connected to the inverter output and the inputs of the third and fourth limiting blocks, and the integrator output is connected to the outputs of the third and fourth blocks restriction and is the output of the device, the reference input of the third restriction block is connected to the output of the first nonlinearity block of the dead band type, the reference input of the fourth restriction block with the output of the second block of nonlinearity of the dead zone type and the output of the third source of negative voltage. FIG. five. FIG. 2 V (i)