SU1455390A1 - Displacement digitizer - Google Patents

Abstract

The invention relates to automation and computing and can be used in software systems for controlling machine tools in optical and radio telescope control systems. The purpose of the invention is the accuracy of the converter. To do this, a two-source radiation source, indicator and measuring disks, two main and two additional photodetectors, an output shaping unit, a first switch, an analog-to-digital converter, a digital-to-analog converter, four amplifiers, two differential amplifiers, comparator, two switches. The invention makes it possible to increase the accuracy of the converter due to the fact that the unmodulated signals from the outputs of the amplifiers are fed to the inputs of the comparator and the first switch. The switch is controlled in such a way that the input signal of the analog-to-digital converter (ADC) always receives a large voltage. The code from the ADC output is fed to the inputs of a digital-to-analog converter (DAC), to the analog input of which through the second switch receives a larger amplitude signal, which through the third switch goes to the input of the output code generation unit, to the second input of which through the second and third switches comes smaller amplitude signal. 1 il. (L SL SP OA CD

Description

one

The invention relates to automation and computing technology and can be used in software systems for controlling machine tools, in optical and radio telescope control systems. The aim of the invention is to improve the accuracy of the converter.

The drawing shows a functional converter circuit. The displacement transducer to the code contains measuring and indicator disks 1, 2, sources 3, 4 radiation, main photodetectors 5, 6, additional photoreceivers 7, 8, amplifiers 9-12, differential amplifiers 13, 14, comparator 15, switches 16-18, analog-to-digital converter (A / D converter) 19, digital-to-analog converter (D / A converter) 20, and an output code generation unit 21.

The measuring disk 1 of the converter contains an additional track in the form of a transparent ring and the main measuring track (not shown) that can be performed both raster and functional, the transmission function of which varies harmonically or linearly during one revolution of the converter shaft.

In the proposed converter, a functional track is used as the main track.

Note that the pairs of photodetectors 5, 7, and 6, 8 are made on the same crystal (i.e., are two-site). The main advantage of such photodetectors is the small deviation of the sensitivity spread between the areas from destabilizing factors. Note also that the pairs of photodetectors 5, 7 and 6, and 8 are shifted relative to each other by / 2.

The Converter operates as follows.

When the measuring disk 1 is moved relative to the indicator disk 2, the radiation of sources 3, 4 modulated by the coupling of the main measuring track and the slits of the indicator disk 2 fall on the main photocouplers 5, 6, at the outputs of which harmonic signals are generated. These signals are fed to the inputs of amplifiers 9, 12, the outputs of which form signals

and,

and

01

Ui where and

and

oi

-f- u, sine-, + Uh, /, cose;

O1

and and

Oj

and

mi

- constant signal components; and and - amplitudes of signals; 0 - shaft rotation angle

converter

Due to the fact that the additional photodetectors 7, 8 are placed opposite the transparent section of the additional annular track, constant voltages will be generated at their outputs depending on the intensities of the emitters 3, 4 and the sensitivity of the photodetectors 7, 8. Adjustment of the transducer produced in such a way that the voltage at the outputs of the amplifiers 10 and 11 would be equal to the constant component of the signals U

Uo,)

And U l respectively (i.e. U

01

and

This can be done by adjusting both the steepness of the characteristics of the photodetectors 7, 8 and the gains of the amplifiers 10, 11.

Harmonic and permanent signals from the outputs of amplifiers 9-12 are fed to the corresponding inputs of differential amplifiers 13, 14, the outputs of which form symmetrical relatively zero signals

Uj

U4

 U, sin0

about

five

0

five

0

At the same time, the constant voltages and 01 and 02 from the outputs of the amplifiers 10, 11 are fed to the inputs of the comparator 15, the output of which is connected to the control inputs of the switches 16, 17 and 18.

Assume that under normal conditions of operation of the transducer amplitude and, the TC and U signals are equal. Consequently, both the constant voltages UQ and U are equal at the inputs of the comparator 15. Therefore, at its output, an O or 1 code is formed with equal probability. It enters the control inputs of the commutators 16, 17, 18. Note that the presence of hysteresis the comparator 15 eliminates the possibility of generating signals at its output with equal input signals. Assume that the O code is generated at the output of the commander 15. In this case, the voltage input Uoi is fed through the KOMi jyTaTop 16 to the reference input A1SC 19, and the voltage from the outputs of the amplifiers 10, 11 is connected to the measuring input. At the output of the ADC 19, a code is generated equal to

N and

N,

01

where n

Max

is the maximum number equal to 1111. ... 1. Since U Uo2, then N, o (is N ,,. The signal Urn, sin in from the output of amplifier 13 through switch 17 is fed to the analog input of multiplying DAC 20, to digital inputs which code comes from the output of the MS, 19. The magnitude of the output voltage of the DAC 20. is determined by its transfer coefficient.At the maximum value of the DAC code 20, its output voltage is equal to:

and

chain block

- (1 - 2 p) Ug y,

where n -. number of bits

Since the value of / 2 is very small (so; for a 10-bit DAC, 20 is less than 0.001%), it can be ignored and

and

Mp

 UBX miSine.

Thus, signals of equal amplitude arrive at block 21

world wide code code, which is a widely known sine-cosine signal converter and code.

Note that if a code 1 was formed at the output of the comparator 15, the switches 16-18 would be switched so that the reference input of the ADC 19 received a voltage of o Lt on the analog input I of the DAC 20 - Uni- .cose. In this case, the outputs of the output code generation unit 21 contain signals that are given to the signals when the code value is at the output of the comparator 15.

Suppose that from the influence of destabilizing factors, the signals at the outputs of amplifiers 9., 10 have decreased by a factor of K. Then, the inputs of the comparator 15 receive a voltage equal to Uoi / K

analog 0

and Up4, and at the output of the comparator 15, a code 1 is generated, arriving at the control inputs of the switches 16-18. In this case, the input voltage through the switch 16 will receive a voltage, and the measured input - U, / K. Similarly, the analog input of the DAC 20 through the switch 17 will receive the signal and cos0 from the output of the amplifier 14, and the input of the switch 18 will receive the signal U, / Ksin6.

Switches 16-18 are switched in such a way that large voltage sources, i.e., are received at the reference input of the ADC 19 and the analog input of the DAC 20. U and and Sozb.

Then the code on the ADC 19 code will be

N - N X V LAOX

THAT, respectively, is reduced to a factor of K in the transmission coefficient .CAT 20. Therefore, the voltage is at

455390

during his will u

and

15

Thus, a decrease in the amplitude of the sine-wave signal by a factor of K will result in a similar decrease in the amplitude of the cosine signal at the output of the DAC 20. Equal amplitude sine and cosine signals go through the switch 18 to the inputs of unit 21.

Switching by switch 18 is carried out in such a way that a sinusoidal signal is always present at the first input of block 21, and a xinusoidal signal is present at the second input.

Claims (1)

Invention Formula 0 about five five 0 five P A displacement transducer into a code containing two radiation sources, each of which through the main and additional tracks of the indicator and measuring disks are optically connected to the respective main and additional photoreceivers, the output code generation unit, the first switch, the analog-to-digital converter, the digital-to-analog converter, which differs by the fact that, in order to increase the accuracy of the converter, two differential amplifiers, a comparator and two switches, the main outputs were introduced into it; photo receivers are connected to the first inputs of the first and second differential amplifiers, respectively; the outputs of the additional photoreceivers are connected to the second inputs of the first and second differential amplifiers, respectively, to the first and second inputs of the comparator, and to the first and second information inputs of the first switch, the outputs of which are connected to the analog-to-digital converter inputs, the outputs of which are connected to the digital inputs of the digital-analog converter, the output of which is connected to the first information the output of the second switch, the outputs of the differential amplifiers are connected to the information g inputs of the third switch, the first output of which is connected to the input of the reference signal of the digital-to-analog converter, and the second output to the second information input of the second 714553908 | switch, the outputs of which are connected to the control inputs are shifted to the inputs of the forming unit, the second and the third switching output code of the comparator.