SU1524176A1 - Method and apparatus for displacement-to-code conversion - Google Patents

Abstract

The invention relates to automation and computer technology and can be used in software systems for controlling machine tools, in robotic systems. The aim of the invention is to improve the accuracy of conversion of movement to code. To this end, in the method of converting the displacement into a code, based on converting the displacement of the quantized element 1 into two analog signals, shifted relative to each other by ϕ / 2 at the outputs of blocks 4, 8 photodetectors, comparing them with the signal of the corresponding level, shaping the outputs of the threshold drivers 12-1, 12-2 of two square-wave signals, the formation in the block of 13 pulses on the fronts of these signals and their counting of counters 16, as a result of which the output code is formed, the comparison is carried out t with the reference voltage obtained as a result of conversion using the digital-to-analog converter 17 of the output code to positive voltages (at the output of the converter 17) and negative (at the output of the inverting amplifier) polarity, depending on the values (zero or one) of the signals of a rectangular shape at the outputs of the threshold formers 12.1, 12.2, the comparison is made with a reference voltage of positive or negative polarity, respectively, which is supplied through the switches 20, 21. Thus, in The transformation process eliminates the influence of errors arising in the manufacture of the quantized element 1. 2 Il.

Description

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shifted relative to each other by / 2 at the outputs of blocks 4, 8 of photodetectors, comparing them with a signal of the appropriate level, forming the results of comparison of the outputs of the threshold formers 12.1, 12.2 of two rectangular signals, forming in block 13 pulses on the edges of these signals and their counting by the counter 16, as a result of which the output code is formed, the comparison is made with the reference voltage obtained as a result of the conversion by the digital-to-analog converter 17 of the code to the reference

The invention relates to automation and computing and can be used in software systems for controlling machine tools, in robotic systems.

The aim of the invention is to improve the accuracy of conversion of movement to code.

Fig. 1 shows a block diagram of a movement-to-code conversion device; figure 2 - diagrams, in accordance with the method of transforming the principle of operation of the device.

A device for converting movement into a code used for unidirectional movement contains a quantized element 1 with uniformly alternating transparent and opaque portions, slot apertures 2, a radiation source 3, a unit 4 of photodetectors containing photodetectors 5 and 6 and a differential amplifier 7, unit 8 photodetectors containing photodetectors 9 and 10 and differential amplifier 11, threshold drivers

12.1 and 12.2, a pulse shaping unit 13 containing drivers 14.

14.2fronts and element 15 OR, counter 16, digital-to-analog converter (D / A converter) 17, voltage source 18 inverting amplifier 19 and switches 20 and 21.

The movement-to-code conversion device operates as follows.

In the initial (rightmost position) of the quantized element I counter

positive voltage (at the output of the converter 17) and negative (at the output of the inverting amplifier) polarity, depending on the values (zero or single) of square-wave signals at the outputs of the threshold drivers 12.1, .12.2, the comparison is made with a positive voltage or negative polarities, respectively, that flow through the switches 20, 21. In this way, the transformation process eliminates the influence of errors that occur when the quantized element 1 is produced. 2 Il.

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16 is set to the zero state. Resetting the counter 16 to zero can be done either by using a pulse generated at the output of an additional photodetector placed opposite a special 1g; spruce-marker (not shown), or by supplying an external pulse, Reset.

When the quantized element 1 is moved relative to the fixed slit diaphragms 2, the radiation source 3, modulated by the junction of the quantized element 1 and the slit diaphragms 2, gets into the photodetectors 5, 6, 9 and 10, the outputs of which form triangular signals. Since the slit diaphragms 2 in front of the photodetectors 5, 6, 9 and 10 are shifted relative to each other by I / 4 W, where W is the track pitch of the quantized element 1, the triangular signals are shifted relative to each other by n / 2. Thus, at the outputs of photodetectors 5, 6 and 9, 10, antiphase signals are generated to the inputs of differential amplifiers 7 and 11, respectively, at the outputs of which analog signals symmetrical relative to zero are formed (Fig. 2a, b), also shifted relative to each other by if / 2. These signals are sent to the first inputs of the threshold drivers 12.1, 12.2, the outputs of which are connected to the inputs of the pulse shaping unit 13. Due to the fact that in the initial state with a fixed quantized element 1 at the outputs of the formers 14.1,

14.2 of the fronts and the element OR 15 pulses are not formed and the counter 16 is in the zero state, the input voltage of the D / A converter J7

WatsAn Uon NRX, where Up - source voltage 18

stress; Ngji - code for digital inputs

DAC 17.

Therefore, the zero voltage is also present at the output of the inverting amplifier 19.

Thus, at the beginning of the displacement zero potentials from the outputs of the DAC

17 and inverting amplifier 19 through switches 20 and 21, controlled by levels from the outputs of threshold drivers 12.1, 12.2, are fed to the second inputs of these drivers.

Voltage U Source

18 is determined by the formula

Uon where and

 and

W

- amplitude of signals at the outputs of differential amplifiers 7 and 1 I; L1 - the maximum error

quantized element i. So, for example, if the error A1 of a quantized element 1 with a length of 1 m and with a quantization step of W 40 µm, a wound of 5 µm (M 5 µm), and the amplitude and signals is 2 V, then the value of the reference voltage should be equal to, t . 1 V.

Thus, at the beginning of the measurement range, the analog signals (Fig. 2a b) are compared with the zero level and, at the outputs of the threshold formers 12.1, 12.2, rectangular signals (Fig. 2c, d) are shifted relative to each other by Г / 2 the inputs of the pulse shaping unit 13. At the outputs of the formers 14.1, 14.2 of the fronts, short-term pulses are generated along the leading and trailing edges, arriving at the inputs of the OR element 15, at the output of which a sequence of counting pulses is formed (FIG. 2 d). Thus, four counting pulses are formed in one signal period. The pulses from the output of the block 13 are fed to the counting input of the counter 16, the code at the outputs of which is the digital equivalent of the movement. At the same time, the output voltage.CAP 17 when moving the quantized element)

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The entire measurement range L linearly increases from O to Vdn (Fig. 2e). So, in the case of a queuing element quantized by L / 2, the output voltage of the DAC 17 will be U (, / 2. The error D of the quantized element 1 is equal to D1 / 2. Therefore, the initial phases of the signals (Fig. 2) shifted relative to the signals at the beginning of the measurement range by an amount proportional to & 1/2. Direct U (and inverted voltage U (figure 2 g) from the outputs of the DAC 17 and inverting amplifier 19 arrive at the inputs of switches 20 and 21, the outputs of which connected to the second inputs of the threshold drivers 12.1, 12.2, respectively. At zero s In the case of a rectangular signal at the output of the threshold shaper 12.2 (FIG. 2 g), the switch 21 passes to the second input of the shaper 12.1 a voltage 1 of positive polarity 5 from the output of the DAC 17. With a single value of the rectangular signal at the output of the shaper 12.2, the switch 21 passes the voltage negative polarity from the output of the inverting amplifier 19.

Based on the results of comparing the analog signal with the voltages U and U (Fig. 2 g), a first square wave signal is formed (Fig. 2 h). As can be seen from the diagrams (fit.2 g, h), the error L1 / 2 does not lead to an error in reproducing the quantization levels and, consequently, to the perturbation of the converter as a whole.

In the diagram (Fig. 2 g), the magnitudes of the voltages U and U for two periods of the analog signal are shown unchanged, since the output voltage of the D / A converter 17 changes very little when the quantized element 1 is moved by 2 W. So, in the case of using a quantized element 1 with a quantization step of 40 µm and a length of 1 m, the voltage at the output of the D / A converter 17 is changed to 5

on U / 125000.

Similarly, a second rectangular waveform is generated.

Claims (2)

1. A method of converting a movement into a code based on converting the movement of the R first and second analog signals, shifted relative to each other by IV / Z, comparing these signals with a signal of a corresponding level, forming the first and second rectangular signals by comparing the results, generating pulses on the edges of the rectangular signals, generating the output code by counting the number of signals va pulses, distinguished by the fact that, in order to increase the accuracy of the conversion, in it the output code is converted into positive and negative polarity reference voltages, the comparison of the first analog signal It is carried out with a reference voltage of positive polarity with one value of the second rectangular signal and with a reference voltage of negative polarity with a different value of the second rectangular signal, and the comparison of the second analog signal with a positive voltage - polarity with one value of the first signal of rectangular shape and with a reference voltage of negative polarity with another value of the first rectangular waveform. . I 2. An apparatus for converting motion into a code containing a quantized element with a quantization step W, slot apertures shifted one relative to another by the value W (K + 1/4), where K is an integer, a radiation source optically coupled through a quantized element and slotted diaphragms to the inputs of photodetector blocks, the outputs of which are connected to the first inputs of the first and second threshold formers, the upper threshold formers are connected to the inputs pulse shaping unit, the output of which is connected to the counter input of the counter, characterized in that, in order to increase the accuracy of the device, a digital converter, an inverting amplifier, two switches and a source The meter outputs are connected to digital inputs of a digital-to-analog converter, the analog input of which is connected to the output of a voltage source, the output of a digital-to-analog converter connects to the first information inputs of the switches and the input of an inverting amplifier whose output is connected to the second information inputs of the switches, the output of the first threshold shaper is connected with the control input of the first switch, the output of which is connected to the second input of the second threshold driver, output v cerned threshold shaper coupled to the control input of the second switch, whose output is connected to a second input of the first threshold shaper. WITH Well tI IX I t7f / 2 Ji g