RU1775271C - Device for control over drive of dividing machine - Google Patents

Abstract

Usage: measuring technique, in dividing machines designed for the manufacture of diffraction gratings, SUMMARY OF THE INVENTION: the device comprises a fixed and movable part with coarse and precise displacement drives, a modulated differential photoelectric displacement sensor made in the form of two light sources, measuring and indicator scales with raster gratings > & l of a photodetector deposited thereon, the measuring and indicator scales being connected to the fixed parts of the dividing ma ins respectively bitmap lattice applied to a display scale as two rasters are shifted one relative to the other half raster period, and each light source optically coupled to the photodetector through one of the rasters. The device also includes a synchronous detector and a multivibrator, with the first output of the multivibrator connected to the first light source and the control input of the synchronous detector, the second output to the second light source, the output of the photodetector connected to the input of the drive of coarse movements through a series-connected detector and a reference unit of movements with the signal input of the synchronous detector through a key, the control input of which is connected with the output of the movement reference unit. The signal output of the synchronous detector is connected to the input of the drive of precise movements through the comparator, drive, switch, RC circuit and adder connected in series to the device, while the control input of the switch is connected to the output of the movement reference unit, and the second signal input is grounded, the second the adder input is connected to the output of the synchronous detector. 2 il.sls V4VJSP ^

Description

The invention relates to measuring technique and can be used in dividing machines for cutting diffraction gratings.

A control device for the drive of a splitting machine is known, comprising the movable and fixed parts of the splitting machine, a drive connected to the moving part of the splitting machine, a displacement sensor and a movement reference unit, the output of which is connected to a control input of the drive, in series.

The disadvantage of this device in relation to fission machines for the division of diffraction gratings is

the accuracy of positioning the movable part during periods of applying the next strokes is low. In these periods, the moving part undergoes a drift due to the elastic deformations of the drive accumulated when the moving part is brought into the positioning position. The magnitude of the drift is uncontrollable, depending on a number of factors, and fluctuations of this magnitude appear on the diffraction gratings as fission errors.

The closest technical solution to the invention is a control device for the drive of the dividing machine, comprising the stationary and moving parts of the dividing machine, coarse and precise movement drives sequentially kinematically coupled to the moving part of the dividing machine, a modulated differential photoelectric displacement sensor made in the form of two light sources, measuring and indicator scales with raster grids deposited on them and a photodetector, moreover, the measuring scale nene with the stationary part of the dividing machine, a modulated differential photoelectric displacement transducer made in the form of two light sources, measure the 1/1 and indicator scales with raster gratings and a photodetector applied to them, the measuring scale connected to the fixed part of the dividing machine, the raster grating is applied to an indicator scale in the form of two rasters shifted relative to each other by half the raster period and each light source is optically coupled to a photodetector. from rasters, a synchronous detector and a multivibrator, the first output of the multivibrator connected to the first light source and the control input of the synchronous detector, the second output to the second light source, the output of the photodetector connected to the input of the drive of coarse movements through a series-connected detector and a reference unit of movements and with the signal input of the synchronous detector - through a key, the control input of which is connected with the output of the reference block moves. In this device, a controlled drive of precise movements (which can be piezoelectric or agnostostrictive elements) seized in a kinematic circuit connecting a drive of rough movements with a moving part is seized, and in addition, a closed loop for automatically controlling the position of the moving part is provided. Due to this, the positioning of the movable part is carried out at certain periods of the device operation. After moving the movable part into position

its next positioning, when the movement counting unit is triggered, the key opens and closes the loop for adjusting the position of the moving part. As a result, the initial drift value, as well as

its fluctuations decreases by a factor of K + 1, where K is the gain of an open control system.

The disadvantage of this device is the limited ability to achieve positioning accuracy

moving parts. This leads to the formation of division errors and, above all, random (local errors), relatively slowly varying along the cutting width. This is related to that. that the above control system is always characterized

some (and not too large) critical value of the coefficient K (we denote it by K), above which it is impossible to increase this coefficient - self-oscillations occur in the system.

According to the theory of automatic control, the possibility of optimizing (increasing) the coefficient K is determined by the possibility of increasing the ratio of the time constants Ti and T2 in the equation of an open control system (including the control object - the moving part - and the controller)

dS

 + S () Fb,,

where S is the magnitude of the drift; t time;

Fb is the perturbation function of the position of the moving part (in our case, Q can be taken as Fb Sb, where 5b is the deformation of the drive of the moving part).

Thus, K g-. At the same time, T2 cannot be reduced, since its value is determined mainly by the inertial mass of the moving part and partly by the inertia (delay time) of the filter elements of the controller. (Although the inertia of the elements of the controller is reduced to

Q to a minimum due to the optimization of the structure of the prototype device),

An increase in the inertia of the controller (constant TI) above a certain value is impossible, since then the controller does not

5 will be able to monitor the changing magnitude of the drift and respond to its increase,

The purpose of the invention is to improve the accuracy of division. On Fig, 1 presents a block diagram of a device; in FIG. 2 - timing diagrams of signals generated at the outputs of the device blocks. The device comprises a fixed 1 and a movable 2 parts. Kinematically connected in series with the coarse 3 and precise 4 movements drives are connected to the movable part 2. The modulated differential displacement transducer 5 of the moving part 2 includes a measuring scale b mounted on the fixed part 1 and an indicator scale 7 mounted on the moving part 2. On both scales, raster gratings are applied, and the raster grating is applied to the indicator scale 7 in the form of two rasters shifted one relative to the other half the period of the raster. The displacement sensor 5 also includes two light sources 8 and 9 and a photodetector 10, each light source being optically coupled to the photodetector 10 via a corresponding raster of the indicator scale 7. The electronic circuit of the device contains a detector 11 and a movement reference unit 12 connected in series by which the output of the photodetector 10 is connected to the input of the drive of coarse movements 3. To the output of the photodetector 10 are also connected in series a key 13 and a synchronous detector 14. The control input of the key 13 is connected to the output one of the displacement counting unit 12. The device contains a multivibrator 15, both opposite inputs of which are connected to light sources 8 and 9, and one of the outputs is also connected to the control input of the synchronous detector 14. The signal output of the synchronous detector 14 is connected to the input of the exact displacement drive 4 by means of sequentially connected comparator 16, drive 17, switch 18, RC chain 19 and adder 20. The second signal input of switch 18 is grounded, its control input is connected to the unit from couple movements 12, a second input of the adder 20 is coupled to the output of the synchronous detector 14. The apparatus operates as follows. The multivibrator 15 generates rectangular pulses arriving in antiphase to the light sources 8 and 9. Measuring 6 and indicator 7 of the scale form a raster conjugation, which when moving the moving part 2 relative to the fixed part 1 modulates the light flux generated by the light sources 8 and 9. Thanks the mutual shift of the raster grids deposited on the indicator scale 7 by an amount equal to half the period of the raster, the electrical signals taken from the photodetector 10 contain two envelopes 21 and 22 (Fig. 2), shifted one o in relative to the other 180 ° C. The frequency and phase of the signals forming the envelopes, is determined frequency signals generated by the multivibrator 15 and the moiré fringes phase detector 5. The envelope detected by detector unit 11; unipolar vibrations 23 from its output goes to the input of the movement counting unit 12. In the process of supplying the moving part 2 relatively motionless 1 to the rough drive 3, block 12 calculates the specified number of vibrations 23. After that, a signal is generated at the output of block 12 that turns off the rough drive 3 (and simultaneously turning on the key 13 and the switch 18) and thereby stopping the flow of the moving part 2. Then the drift displacements 5 of the moving part 2 begin. The signal from the output of the photodetector 10 is transmitted through the key 13 to the signal the input of the synchronous detector 14. The reference signal to the control input of the synchronous detector 14 is received from the output of the multivibrator 15. The synchronous detector 14 performs synchronous (phase-sensitive) detection of the envelopes of the signal taken from the photodetector 10. At the output of the detector 14, a signal equal in magnitude is generated envelope difference, with polarity determined by the phase ratio of its input and reference signals. The synchronization detector 14 is turned on by the key 13 near point 24, where the signal amplitude is close to zero. The corrective voltage from the output of the synchronous detector 14 is supplied through the adder 20 to the input of the precise displacement actuator 4, causing it to deform. As a result, the drift value (curve 25) decreases compared to the initial one (curve 26) by a factor of K + 1. The reduced drift of the moving part 2 has (as before) an exponential time dependence t St-Si l-e-). de Si is the asymptotic drift value of the 1st division cycle; t - time: r-constant time drifts. At the output of the synchronous detector 14, a correction voltage 4 corresponding to the drift is obtained:

Ui Ui (1-ehi

where ui

asymptotic voltage value ..

It is approximately equal to the maximum voltage Ui allocated at the output of the synchronous detector 14 at the end of the division cycle (t t.

The newly introduced asymptotic pulse control loop is tuned. The comparison voltage is set from (28) of the comparator 16 to a slightly lower voltage Ui (U3 0.5, 75 Ui, and the time constant of the RC chain 19 is set to the drift constant (g RC). When the device is operating, a compensating drift voltage is generated changing exponentially, as the voltage Ui (27) increases at the output of the synchronous detector 14 at a certain point in time, it reaches the specified voltage from and the output of the comparator 16 generates a U-shaped pulse 29, which remains until the end of the division cycle (when The key 13 is turned off and the voltage Ui drops to zero.) This U-shaped pulse recharges the accumulator 17 so that the voltage UH (30) at the output of the accumulator 17 increases from cycle to cycle. At the beginning of each positioning cycle of the moving part, the switch 18 and the voltage UH is applied to the input of the RC circuit 19, at the output of which a computer begins to stand out, which exponentially increases the correction voltage t

Uk UH (1st).

This voltage, applied through the adder 20 to the input of the precise displacement actuator 4, causes its compensating deformation and, as a result, the drift value decreases. In this case, the asymptotic voltage Ui (27) at the output of the synchronous detector 14 decreases and, accordingly, the pulse duration Tn at the output of the comparator 16 decreases. Finally, a stable operation mode of the drive 17 is established when charging it with a short pulse Tk from the comparator 16 is unloading it through external circuits.

At the end of each dividing cycle, the signal from the output of the movement reference block 12 sn 1 is turned off, the key 13 is turned off, the switch 18 is switched to its original position when its input is grounded. The RC chain 19 is discharged almost instantaneously through switch 18 to zero voltage L1L.

Thus, the compensating component of the correction signal formed in the device in the form of an exponent corresponding to the nature of the drift stabilizes its value, sharply reduces it, and accordingly sharply reduces the time variations in the voltage of the correction component of the signal. Due to this, the path that forms the regulatory component of the correction signal can be made more inertial (increase the constant Ti) and thereby sharply increase the correction efficiency (along with the correction coefficient K).

Claims (1)

The claims A drive control device for a dividing machine comprising fixed and moving parts with coarse and precise displacement drives, including a modulated differential photoelectric displacement sensor made in the form of two light sources, measuring and indicator scales with raster gratings applied to them, and a photodetector, moreover, the measuring and indicator scales are connected to the stationary and moving parts of the dividing machine, respectively, the raster grid is applied to the indicator scale in the form two rasters, shifted one relative to the other by half the raster period, and each light source is optically coupled to the photodetector through one of the rasters, a synchronous detector and a multivibrator, moreover, the first output of the multivibrator is connected to the first light source and the control input of the synchronous detector, the second output is connected to the second light source, the output of the photodetector is connected to the input of the drive of coarse movements through a series-connected detector and the reference unit of movements and to the signal input of the synchronous detector through a key, whose control input is connected to the output block movement counters, characterized in that, in order to increase the accuracy of division, the signal output of the synchronous detector is connected to the input of the drive of precise movements through the series-connected comparator, accumulator, switch, RC chain and adder, while the control input of the switch connected to the output of the block of movements, and the second its signal input is grounded, the second input of the adder is connected to the output of the synchronous detector. 8 9 21 V where Jv