SU1356224A1 - Displacement-to-code converter - Google Patents

Abstract

The invention relates to automation and computing and is intended for use in linear displacement transducers in code. To increase the noise immunity, the oscillator contains a code scale 1, a block of 2 photodetectors, a block of 3 threshold elements, a block of 4 comparisons, a shift register 5, a counter 8 and a trigger 9, a voltage source, generators 6, 7 are introduced. analog adder 10 and comparator 11, and the code scale 1 is made of light and dark bands, the width and location of which are determined by the fixed part of the numerical pseudo-random sequence produced by the generator 7. When the scale 1 moves, the modulated signals from the outputs f block 2 receivers are normalized by block 3 by comparing them with a reference voltage equal to half the amplitude of the signals of the photoreceivers of block 2. The generator 7 generates a pseudo-random sequence of signals using a register 5 according to a signal from the generator 6 the outputs of blocks 3 and 5. When they are equal, the outputs of block 4 generate logical 1 signals, and when unequal - logical O. Analog adder 10 generates a voltage proportional to the number of matches and does not match The signal values at its inputs, determined by the number of logical 1 and O. When the output signal of the adder 10 exceeds the reference, the voltage of the comparator 11 triggers the trigger 9, which with its signal stops the counter 8. In the counter 8, thus, a code whose value is proportional to the movement of the code scale 1 relative to the block 2 photodetectors. 2 Il. | CO O1 about to o 4

Description

one

The invention relates to automation and computing, and is intended for use in linear transducer-to-code converters.

The purpose of the invention is to increase the noise immunity of the converter.

FIG. 1 shows a converter block diagram; in figure 2 1356224

Each pulse arriving at the clock input of the shift register 5 shifts the information contained in it (i.e. the part of the M-sequence generated by the pseudo-random sequence generator 7) by one bit. From the outputs of the register 5, electrical signals are sent to

the correlation function Q, the inputs of block 4.

Block 4 is timed, found If the bit of the first i-bit bit is the same as the first time of block 4 is set to 1, the logical outputs of block 4 are information at the direct output and inverse output is equal to

the sequence and the conjugate of the code-box.

The converter contains the code scale 1. The location and width of the light and dark bands are determined by the fixed part of the numerical pseudo-random sequence, block 2 of photodetectors, block 3 of threshold elements, block 4 of comparison, shift register 5, generator 6 of pulses, generator 7 of pseudo-random sequence, counter 8 , trigger 9, analog adder 10, comparator 11 voltage source (not shown).

The Converter operates as follows.

The invention of the code scale 1 is projected onto a block 2 of photodetectors, the number of elements m in which is larger than the size n of the shift register in generator 7, designed to form a pseudo-random sequence of maximum length L 2 - 1. At the output of the illuminated photodetectors of block 2, there appear electrical signals proportional to light level. Block 3 generates electrical signals by comparing the signals from block 2 of photodetectors with a reference voltage equal to half the amplitude value of the signals of photodetectors of block 2. From the output of block 3, the signals go to block 4 of the comparison.

According to the signal of the initial installation of the generator 6, the generator 7 of the pseudo-random sequence and the counter 8 are started, and the trigger 9 is set to the initial state. In this state, trigger 9 allows the arrival of clock pulses from generator 6 to the counting input of counter 8.

For each clock pulse of the generator 6 pulses, the generator 7 of the pseudo-random sequence generates the next information signal of the M-sequence, the input of the shift register 5.

block 4 inputs.

Block 4, bitwise, analyzes the information at its inputs. In the case of coincidence of the i-ro state of the first inputs and the i-ro state of the second inputs, the corresponding bit of the direct outputs of block 4 is set to logic level 1, otherwise - logical level O. On the inverse outputs of block 4 inverse information is set. The presence of all 1 on the direct outputs (or all O on the inverse outputs) of block 4 means a one-to-one coincidence of information on

the outputs of the block 3 threshold elements with information at the outputs of the register 5. From the outputs of block 4, the signals are fed to the corresponding inputs of the analog adder 10. The output of the analog adder 10 sets a voltage proportional to the difference between the number of matches (the number of logical 1 at the direct inputs of the block 4 matches ) and the number of discrepancies (the number of logical 1 at the inverse outputs of block 4) of the state - the research institutes of the first and second inputs of block 4 when they are equal to the same comparison. If the signal at the output of the analog adder 10, which is fed to the input of comparator 11, exceeds the value of the reference voltage, the latter will transfer the trigger. 9, which in turn will stop the counter 8.

45

Threshold voltage

is chosen equal to

and K (m-p) U, +

Kr1 / o.

where k

the transmission coefficient for the inputs of the analog adder 10; , Ug are the minimum values of logical 1 and

p is the allowable number of erroneously read bits of the code scale 1 or incorrectly generated information signals M-pic (pedagogy.

31

The digital code received in counter 8 after changing the state of trigger 9, i.e. The number of clock pulses that occurred from the beginning of the cycle until the maximum correlation peak appears at the output of analog adder 10 unambiguously determines the position of code scale 1 relative to the photoreceivers of block 2.

Separate errors in reading the code scale 1 series do not lead to an incorrect result, but only reduce the magnitude of the main correlation peak at the output of the analog adder 10 and increase the amplitudes of the side correlation peaks (Fig. 2). The difference between the values of the main and maximum lateral correlation peaks, called the distinctiveness index (OL), determines the ability to recognize the corresponding synchronization time of the code sequence with the permissible number of erroneously read bits to the code scale 1, i.e. determine the position of the code scale 1.

In each particular case of use of a displacement transducer

the code for a fixed number of m pho 30 is connected to the second output

In block 2, a compromise should be sought between the value of the range of measured object positions and the value of PR, i.e. device noise immunity.

If you use the M-code sequence of length Lt, then the value of PR 2 is maximum, and the range of measured displacements in

In this case, the limited linear size is 40; the key to the first output of the generator

rum block 2 photodetectors.

In another limiting case of using an M-sequence of length

t h

L / - I, which defines diaO

0

Claims (1)

displacement measurement area, PR value 1. Invention Formula A motion converter in a code comprising a single-track code scale optically coupled to a photodetector unit, the outputs of which are connected to the corresponding inputs of the threshold element block, the outputs of which are connected to the first group of inputs of the comparison unit, a shift register, a pulse generator, a trigger and a counter, characterized in that , in order to increase the noise immunity of the converter, an analog adder, a reference voltage source, a comparator, a pseudo-random sequence generator, and The do-not scale is made in the pseudo-random sequence code, the first output of the pulse generator is connected to the first input of the counter, and the second output is connected to the second input of the counter and the first input of the pseudo-random sequence generator, the second input of which is connected to the first output of the pulse generator, and the output is connected to the first input of the shift register, the second input of the pulse generator, the forward and inverse outputs of the comparison unit are connected to the inputs of the analog adder, the output of which is connected to the information the comparator input, the reference input of which is connected to the output of the voltage source, the comparator output is connected to the first trigger input, the second input of which is impulses, and the output is connected to the third input of the counter, the outputs of the shift register are connected to the second group of inputs of the compare block. Editor A. Dvlinich Compiled by M. Sidorov Tehred L. Serdyukova Order 5812/55 Circulation 900 Subscription VNIIPI USSR State Committee . for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab, 4/5 Production and printing company, Uzhgorod; st. Project, 4 Proofreader O. Kravtsov