SU1490484A1 - Displacement monitoring method - Google Patents

Abstract

This invention relates to instrumentation technology. The aim of the invention is to improve the accuracy by eliminating the influence of changes in the transmission coefficient of the photoelectric channel and changes in the initial energy flux on the result of the control. They form energy flows shifted in space in the direction of movement, modulate them in time in accordance with periodic functions that do not contain even harmonics and are shifted by a quarter period, and in space, depending on the magnitude and direction of movement, form the total energy flow that is transformed into an informational electrical signal. An additional total energy flow, obtained by diverting a part of the initial streams modulated in time, is converted into an electric reference signal. Based on the result of comparing the phases of the information and reference signals, the magnitude and direction of movement is judged. The positive effect is provided by modulating in time the energy fluxes in accordance with periodic functions that are mutually shifted by a quarter of a period. If these functions do not contain even harmonics, then the change in flux during movement causes a corresponding phase shift of the information signal, i.e. the conversion is carried out into a phase shift that does not depend on the absolute values of the flows, but depends only on their ratio, therefore does not depend on the transmission coefficient. Independence from changes in the original energy fluxes is provided by the formation of such a reference signal, the phase of which tracks the changes in the original fluxes. 1 hp f-ly, 6 ill.

Description

one

(21) 4345231 / 24-28

(22) 10/16/87

(46) 06/30/89. Bul № 24 (72) E.F.Tovkach

(53) 531 .7 (088.8

(56) USSR Author's Certificate No. 468283, cl. H 03 M 1/22, 1975.

(54) METHOD OF CONTROL OF TRANSFER - (57) The invention relates to instrumentation engineering. The aim of the invention is to improve the accuracy by eliminating the effect of changes in the transmission coefficient of the photoelectric channel and changes in the initial energy fluxes.

on the result of the control. Energy flows are shifted into space in the direction of movement, modulated in time according to periodic functions that do not contain even harmonics and shifted by a quarter of the period, and in space, depending on the magnitude and direction of movement, form the total energy flow that is transformed into an information electrical signal. An additional total energy flow, obtained by diverting a part of the initial streams modulated in time, is converted into an electric reference signal. Based on the result of comparing the phases of the information and reference signals, the magnitude and direction of movement is judged. The positive effect is provided by modulating in time the energy fluxes in accordance with periodic functions that are mutually shifted by a quarter of a period. If these functions do not contain even harmonics, then the change in flux during movement causes an appropriate phase shift of the information signal, i.e. the conversion is carried out into a phase shift that does not depend on the absolute values of the flows, but depends only on their ratio, therefore does not depend on the transmission coefficient. Independence from changes in the original energy fluxes is provided by the formation of such a reference signal, the phase of which tracks the changes in the original fluxes. 1-hp f-ly, 6 ill.

g

.

;about

about

4 00 k4

The invention relates to instrumentation technology and can be used for contactless control of linear movements by the optical method, as well as for autocollimation control of the angular deviations of objects.

The purpose of the invention is to improve accuracy by eliminating the effect of changes in the transmission coefficient.

photovoltaic channel and changes in the initial energy flux on the result of the control.

Figure 1 shows the functional diagram of the device for implementing the proposed method (for the case of autocollimation monitoring of the angular deviations of the object); Fig. 2 and Fig. 3 - cross-sections of energy flows in the plane of modulating

the diaphragm at the two last positions; in Fig, A - spatial modulating functions A, (x) and Aj (x); Fig. 5 is a positional characteristic corresponding to the proposed method; 6 shows temporary diaphragms illustrating the proposed method for the case of modulating (in time) triangular-shaped signals.

The method is carried out as follows.

The energy flows are formed mutually shifted in space in the direction of movement.

They modulate in time the energy fluxes according to the laws expressed by periodic functions that do not contain even harmonics and are mutually shifted by a quarter of the period.

The energy flows are modulated in space, depending on the magnitude and direction of movement.

Form the total energy flow of energy flows modulated in time and in space.

Form an information signal proportional to the total energy flow.

An additional total energy flux is formed by diverting the initial energy fluxes modulated in time.

Form a reference signal proportional to the additional total energy flow.

The phase of the information signal is compared with the phase of the reference signal and the magnitude and direction of movement is judged by the comparison results.

A device for carrying out the proposed method (for the case of autocollimating control of angular deviations of an object) contains a control element 1, made, for example, in the form of a mirror, rigidly connected to a controlled object (not shown) of an autocollimation optical system 2 (system 2), installed in such a way that the control element 1 is in the field of view of the system 2, the beam splitter 3, optically conjugated to the system 2, the sources 4 and 5 of the radiation and the modulating diaphragm 6, spaced respectively into two conjugate focal points System 2 planes formed by the beam splitter 3, photos

ten

IS

20

25

thirty

35

40

D5, at Q in 9048A

an information flow receiver 7, installed along the radiation information flow behind the modulating aperture 6, an optical system 8 and a reference flow photo-receiver 9, the modulating signal generator 10, the outputs of which are connected to the control inputs of the radiation sources 4 and 5, respectively, and a phase shift meter 11, the inputs of which are connected respectively to the outputs of the information flow photo-receiver 7 and the reference flow photo-receiver 9, and the output is the output of the device ..

The device operates as follows. The radiation sources 4 and 5 form energy flows that pass through the autocollimation optical system 2 (the path of the rays is shown conditionally), are reflected from the control element 1, pass through the autocollimation optical system 2 again, are reflected from the beam splitter 3 and fall onto the modulating diaphragm 6, on which an autoglow image of radiation sources 4 and 5 is built (Fig. 2). When the control element 1 deviates, the image of radiation sources 4 and 5 moves along the modulating diaphragm 6, thus achieving spatial modulation of the energy fluxes. The total energy flow enters the photodetector 7 of the information flow, which converts it into an informational electrical signal, the phase of which depends on the angular position of the control element 1. Unmodulated in space (but modulated in time by the generator of 10 modulating signals) is reflected from the beam splitter 3 and through the optical system 8, it is sent to the photodetector 9 of the reference flux, which converts the additional total energy sweat ok into the reference electrical signal with which the information signal in the phase shift meter 11 is compared.

55

The method of motion control is developed on the basis of the following principal provisions.

/ Figure 2 shows the cross sections of the energy flows P, and PJ in the plane of the modulating diaphragm 6. The flows P and P are separated in space by the distance b. The flux in space is modulated by moving the streams P and P relative to the diaphragm 6 along the X axis. The shaded parts of the streams P, and P fall inside the diaphragm 6 and form a total flux, which is converted into an informational electrical signal whose amplitude is proportional to the total flow. When reciprocating the flows P and Pj relative to the diaphragm 6, the proportion of each of the flows P and P changes into the diaphragm 6. The distribution of the flows P and P in the diaphragm 6 with mutual displacement by the value Xj is shown in FIG. With this configuration of flow sections P and P, the spatial modulating functions A (x) and A (x) (depending on the flow falling into the diffraction 6 on the magnitude of the displacement X) will have the form shown in Fig. 4, which can be seen that the fluxes P and P "within the limits of the characteristic size a vary with the movements linearly, respectively, upwards and downwards.

Consider the simplest modulating function that does not contain even harmonics sin cot. The function shifted by a quarter of the period is cos with C. In this case, the flows and P will be modulated in time in accordance with the functions of the sin cot and cos cot and in space in accordance with the functions A, (x) and A (x ),

Since the modulation of X and t is independent, the flux values are respectively

P, (x, t) A ((x) -P. Sincot; P () A, j (x) Po. CosQt,

where P is the pre-modulation streams. Total flow is

P (x, t) P, (x, t) + P ,, (x.t)

Pp A, (x) sincot + A (x) cosco t.

The signal proportional to the total flow is

S (x, t) KP (xft) -, (x) "sin cot + A, (x) cos CO t

K-P, - iA, (x

+ A, CX). -b

ALH) 1

  A -; (x) J

(3)

where K is the proportionality coefficient.

The value of K-P has the meaning of the transmission coefficient of the photoelectric channel.

As can be seen from expression (3), the summed signal S (x, t) acquires a phase shift ID arctg A (x) / A, (x), which does not depend on the transmission coefficient KPjj and is determined only by the shape of the modulating functions A, (x ) and).

If the functions A, (x) and A (x) are presented (within the characteristic size a) in the form

Oh)

Vo (l-cx);

(four)

35

1 + СХ.,.

then q arctg

with and Cf tj.

We represent the phase as (+ + uqi, then from expression (5) we get:

iC arctg CX,

TG iT

where7- ACf - (6)

50

Dependence (6) is a positional characteristic, its appearance is shown in FIG.

Thus, the method allows gg to obtain a positional characteristic that does not depend on the magnitude of the transmission coefficient of the photoelectric channel, thus providing an increase in the accuracy of motion control.

To measure phase 1 shift (or & L (), you must have a reference phase signal. This signal can be any original sin Qt signal. Or cos cot. Phase (in expression (4), t was determined relative to the signal ein Qt .

The above reasoning was based on the fact that it is unmodulated. Bath energy flows are the same and equal to P {. However, in reality these flows are equal to P. However, in reality these flows will always be unequal and, moreover, may change with time. These changes result in errors in the definition of displacement, since the phase shift Cp in this case depends on the unmodulated flows P, and

POI ®-4-arctg | tl b (7)

at the point X-0 A, (0) - - A (0), then

arctg

Pot.

(eight)

01

If we take the same parts of the streams before modulation in space and form an additional total flow P "(t), then the signal proportional to the additional total flow will be equal to

S (t) - .sinO) t h-S

+ P.coscJt - K.Jp ;, + PO I

og

n sin Oat + arctg) o

where K- is the branching factor for currents.

As can be seen from expression (9), the phase of the signal Sa (t) is equal to the phase of the signal S () at the point X 0. Thus, the signal Sa (t) can be used as a reference signal, the phase of which changes with changing fluxes PO, and Po4 synchronously with the phase of the information signal. It is obvious that the phase difference between the informational and oporno signals will not depend on

20

25

thirty

35

) 40

45, §0 of the flows of the P and P.JJ. This further improves the accuracy of motion control.

The essence of the method is considered on the example of the simplest modulating function sincOt. Nevertheless, all reasoning is also valid for periodic signals of any shape that do not contain even harmonics. Such signals when shifted by a quarter of a period occur a phase shift of all harmonics (odd) also by a quarter of a period. Figure 6 shows time diagrams for the case of triangular-modulating signals in time and displacement by the value of Hd. The dotted line shows the reference signal.

Claims (2)

1. The method of motion control, which consists in forming energy flows mutually shifted in space in the direction of movement, modulates energy flows in space depending on the magnitude and direction of movement, forms the total energy flow, which is used in determining the magnitude and direction of movement, characterized in that, in order to increase accuracy, modulate in time the energy flows according to the law, expressed by periodic functions that do not contain even harmonies IR and mutually shifted by a quarter of a period, they form an information signal proportional to the total energy flow and a reference signal, compare their phases and judge the magnitude and direction of movement by phase difference. 2. The method according to claim 1, about tl and h and y and y with the fact that they form an additional total energy flow by diverting part of the original energy flows, modulated in time, and the reference signal is formed proportional to the additional total energy flow . PI 1 N -Ho Phie.1 - FIG. 2 .J Fi9,5