DE2721136A1 - Interpolation network for discrete displacement measurement transducer - uses light source moving along axis w.r.t. photocell array producing outputs phase-shifted by discrete amounts - Google Patents

Abstract

A simple discrete displacement transducer logic interpolator produces, typically, twenty interpolated intervals in each primary interval, using only simple squaring and gating networks. The interpolator can be applied to an array of photocells arranged along an axis and subjected to an illumination of intensity varying sinusoidally w.r.t distance along that axis. The illuminating source along the axis concerned w.r.t the photocell array, producing photocell outputs shifted in phase w.r.t each other by fixed discrete amounts, depending on the velocity of the light source. The photocell outputs are fed in pairs to an array of linear comparator circuits and the square wave outputs of these are taken to an arran of AND gates. The outputs of these are in turn, fed to two OR gates to produce two square waveforms at ninety, one delayed on the other by a quarter period and both running at five times the original photocell output frequency.

Description

Title: Method and arrangement for interpolating

Field of application of the invention: The invention relates to a method and an arrangement for interpolating the division interval of a mechanical division. Graduation marks that are optically scanned are provided on the mechanical graduation will.

The optical signals are converted into electrical signals and are available in this form for interpolation. The procedure and the Arrangement are applicable wherever a measuring head and one with a mechanical Division rigidly connected measurement object are moved relative to each other. The relative movement can be done translationally or rotationally.

Characteristic of the known technical solutions: The interpolation the division interval of a mechanical division is expediently carried out after Conversion of the graduation marks into sinusoidal or quasi sinusoidal electrical Signals. In the DT-AS 1 208 087 an interpolation device is described, in which the photoelectric converter has sinusoidal electrical output signals a mutual phase shift that is the signal period divided by the Number of photoelectric converters corresponds to deliver. The sicias-shaped signals are then converted into square wave signals, and are in a logical network the impulses like that linked together that a multitude of other Pulses with a significantly shorter pulse duration arise. The shortening factor is equal to the number of photoelectric converters and corresponds to half the interpolation factor.

OE 248 717 shows an interpolation device with photoelectric Converters, whose sinusoidal output signals turn regularly over the signal period have offset phase relation to each other. The sinusoidal signals are initially amplitude weighted and then fed to a comparator. The phase position of the output signals of the comparator depends on the phase difference and the size of the amplitude weighting of the input signals. This could theoretically be an unlimited number mutually phase-shifted square-wave signals are formed.

From the sinusoidal output signals of the photoelectric converters can also, as shown in D-AS 1 231 911, transmit further sinusoidal signals Sums or differences of the primary signals are formed, so that for the further Evaluation of a larger number of phase-shifted sinusoidal signals available as photoelectric converters.

From the description of the invention in DT-AS 1 498 137 and DT-OS 1 548 692 a further possibility is known, from existing sinusoidal primary signals to gain additional phase-shifted sinusoidal signals. The primary signals will be fed into a bridge circuit, there are different in each bridge branch amplitude-weighted, and a number of others appear at the bridging paths sinusoidal signals. The zero crossing of the output signals and thus their phase shift to the primary signals depends on the amplitude weighting of the primary signals in the appropriate branches.

The DT-OS 2 106 136 discloses a method for interpolation, after which the more trapezoidal signals of the photoelectric converter once immediately are linked to one another via comparators and in which these signals are also linked still have to be linked to a signal derived from the converter signals.

The amplitude-weighted derived signals are used in a voltage divider taken, at its two inputs each two signals of the photoelectric Transducers are present.

The signals from the photo-electrical converters and the derived signals are linked to one another via comparators in such a way that the square-wave signals at their Outputs a phase shift regularly arranged over the entire signal period exhibit.

In DT-AS 1 945 206 an interpolation method is disclosed, in which the sinusoidal primary signals are first converted into sawtooth signals will. A subsequent comparison of these sawtooth signals with DC voltage signals different size provides square wave signals with correspondingly different Pulse width. By means of a logical combination, square-wave signal sequences can again be derived from them win with a shorter period.

From the description of the invention in DT-AS 1 266 989 and DT-AS 1 273 211 is also known to send two sine signals offset from one another by 900 to the To apply deflection systems of a cathode ray tube and the circulating electron beam to interpolate the signal period.

For the facilities and procedures described, either the The cost of electronic components is relatively high or the phase position of the square-wave signals is strongly dependent on the amplitude and the shape of the curve of the primary signals or the evaluated signals quasi sinusoidal Signals dependent. Stabilizing the amplitude the primary signals is problematic for all of the interpolation methods described. Such a complex stabilization circuit is described in DT-AS 1 208 087.

Most other facilities and procedures dispense with one Stabilization and take changes in the phase position of the square wave signal and ultimately changes in the measured value are accepted.

Aim of the Invention: It is the aim of the invention with little effort to reduce the measurement errors of the measured value interpolator on electronic components.

Essence of the invention: The invention is based on the object Way of generating additional signals and phase-shifted to the primary signals Fundamentally redesign sine or square wave signals.

According to the invention, in a method for interpolating the division interval a mechanical division, in which a division section at an imaging point is optically mapped and is present there in the form of intensity-modulated light signals, in which the light signals are converted into quasi sinusoidal electrical signals, in the case of n comparators from two quasi-sinusoidal electrical signals Square-wave signal sequences are generated, the pulse edges to each other by one such phase angle are offset, which results from the relationship +, and at that for evaluating the mechanical displacement of the division from the square-wave signal sequences to be obtained for an up-down counting, the object is achieved in that the two input signals for each comparator from a number a <n quasi sinusoidal and mutually phase-shifted signals, their phase relation to each other satisfies the relationship x n with x as any natural number from one to n - 1, to be selected.

It is advantageous to use as input signals for each comparator Select signals with a constant phase difference of about # / 2 to #.

The invention is expired in a favorable manner that at the use of interpolation factors according to relation 4 (2k-1), where k represents any natural number, the quasi-siniis-shaped signals Comparators are assigned in such a way that each two by the phase difference their pulse edges adjacent square wave signal sequences at the output of the comparators O / L transition on these pulse edges, while the pulse edges of the subsequent rectangular pulse sequences which are related by their phase shift have an L / 0 transition, eo that the change in the edge transitions is constant in pairs takes place alternately.

In an arrangement for interpolating the division interval one mechanical division, in which optical means for imaging a division section and to convert this section into intensity-modulated light signals at the Imaging point, photoelectric converter for converting the light signals into quasi Sim1s-shaped electrical signals and n number of comparators are provided, in order to generate square-wave signals from these sinusoidal signals, their pulse edges are offset from each other by such a phase angle that results from the Relationship # / n results and in the evaluation of the mechanical displacement of the Division a logical network is arranged to make up these square wave signal sequences To win counting impulses for a pre-RItokwärc counting, the task is according to the invention solved in that to obtain the quasi sinusoidal and phase-shifted to one another Signals at the imaging point a number a <n photoelectric converters so one after the other in the direction of movement of the Light signals on one Distance that corresponds to the period length of the intensity-modulated light signals, are arranged that the distance from the first photo-electrical converter to the other based on this period length corresponds to the relationship x 2t.

n The same applies to an arrangement for interpolating the Division interval of a mechanical division is achieved according to the invention in that to get the quasi sinusoidal and mutually phase-shifted signals a number a <n photoelectric converters in a line at the imaging point are arranged transversely to the direction of movement of the light signals and that the light signals in addition to their intensity modulation in the direction of movement of the light signals also a stepwise or continuous phase shift transversely to this direction of movement have in such a way that the phase position over two arbitrarily selected photoelectric Converters always speak from the relationship x 2 # / n.

The main advantages of the invention are the simple structure of the interpolator, its low requirement for components and, above all, its reduction the measurement error of the entire measurement system. It was achieved that the phase position of the Square-wave signals at the outputs of the comparators are independent of the curve shape of the quasi-iris-shaped signals and of amplitude fluctuations.

The output signals of the photoelectric converters (in the explanations in the prior art, they are also referred to as priority signals) always have a fixed phase relationship to each other. This phase relationship does not change either due to fluctuations in the intensity of the light source, because the phase position of the primary signals depends only on the mechanical adjustment of the photoelectric converter0 The amplitude fluctuations the use of comparators makes the pristra signals largely ineffective made.

The square-wave signal sequences arise at the output of the comparators always by comparing two primary signals. This results in the O / L or the L / O transition at the time of the same voltage values of those to be compared Primary signals, d. H. at the moment of intersecting the one shown as a sine wave line quasi sinusoidal signals. A change in light intensity can affect the time or However, this does not affect the spatial location of these interfaces. The fixed phase relationship the primary signals to each other is achieved by a one-time adjustment of the photoelectric Converter at the image point of the division section is fixed and remains then get constantly.

The interpolation method only requires a small number of photoelectric ones Converter. This is achieved because the phase relationships of the primary signals are favorable and the primary signals are therefore used several times as input signals for the comparators are used.

It is easily possible to use all components of the circuit arrangement, the evaluation of the primary signals and the further utilization of the square-wave signals concern to be integrated into a structural unit.

Working example: The invention is illustrated below with reference to the schematic Drawings explained in more detail. 1 shows an arrangement of photoelectric Converters at the mapping point of a division according to the invention, Fig. 2 the output signals the photoelectric converter according to an arrangement according to FIG. 1, FIG. 3 shows a circuit arrangement for interpolation according to the invention, FIG. 4 shows the square-wave signal sequences at the Suegkagen of the comparators according to FIG. 3, FIG. 5, the output signal sequences at the outputs of the logical network according to FIG. 3.

In Fig. 1 is the arrangement of a number of photoelectric converters A to G shown at the imaging point of a mechanical division. The photoelectric Converters A to G are fixedly mounted on a bracket 1. The sine curve 2 indicates the intensity-modulated light signal via the photoelectric converters A to G.

Fig. 2 shows the profile of the voltage U of the quasi monotonous electrical Output signals a to g of the photoelectric converters A to G depending on Q t. The output signals a to g (also referred to as primary signals) originate in each case the photoelectric converter with the same designation. The phase relationship the output signals a to g among each other is determined by the arrangement of the photoelectric converter d to G in the period space of the intensity-modulated light signals. The period of a light signal has a fixed relationship to the division period of the mechanical division. Their direction and speed of movement are the same tied to the division.

Fig. 3 shows the further electronic circuit arrangement for electrical Interpolation of the primary signals a to g. In each case two of the primary signals a to g are fed to one of the comparators 3 to 12. The selection is based on this according to the intended phase difference of the primary signals a to g. The signal selection should be demonstrated with an example. The falling pulse edge of the square wave signal k should serve as a reference phase for further considerations. As the circuit arrangement contains ten components 3 to 12, must be used in the regular displacement of the phase position of these square-wave signals k to u over the entire period, two square-wave signal sequences exist whose edge has a phase difference of 10 → 18 to the reference 0 phase. These are the square wave signal sequences 1 and u Square wave signal sequence 1 arises at the output of the comparator 8. The input signals to this comparator 8 the quasi sinusoidal primary signals a and f are supplied. According to FIG. 2 lie the points of intersection of these primary signals a and f from the reference phase exactly just this 18 ° away. The effective input voltage for the comparator 8 is the differential voltage of the primary signals a and f. The differential signal leads to a Overdrive of the comparator 8 and in this way forms the square-wave signal 1. At the point of intersection of the primary signals a and f, the polarity of the difference signal is reversed and thus a pole reversal of the square-wave signal 1 takes place.

In the same way in comparators 3 to 12 all arise Square wave signal sequences k to u.

As the phase difference of these square-wave signal sequences k to u to the selected Reference phase, all phase angles are possible that are divided by eighteen a natural Result in number.

From Fig. 2 it can be seen that for each of the in this way marked Phase angle at least one point of intersection of the primary signals a to g exists0 The respective primary signals are the basis for the formation of the square-wave signal sequences with the respectively desired phase shift and are then suitable as an input.

signals for the corresponding comparators, albeit in addition the condition of a sufficiently large phase difference between these two primary signals is satisfied. The phase difference should move approximately between # / 2 and #.

So it depends less on the number of photoelectric ones used Converter, rather than the presence of a sufficiently large number of points of intersection of their output signals with favorable phase relation to each other.

The square-wave signal sequences k to u and the phase shift of their pulse edges are shown in FIG. For further evaluation of the square wave signals k to u, it is useful if the two by the phase difference of their Impuisfianken adjacent square-wave signal sequences k and 1 on these pulse edges have an O / L transition, while the subsequent pulse flanks the Square-wave pulse trains m and n which result from the phase shift to the square-wave signals k and 1 which are adjacent have an L / O transition. In the pulse diagram after 4 shows the change in the edge transitions in the illustrated square-wave signal sequences k to u always alternate in pairs. The difference in angle between two adjacent pulses flank is 180.

The square-wave signal sequences k to u are then a logical Network fed. There are two output signal sequences z1 and Z2 with shorter Periods formed which have a phase shift of + to each other.

The output signal sequences Z1 and Z2 are shown in FIG. It it can be clearly seen that each of the output signal sequences z1 and Z2 composed of individual impulses. The individual pulses are in UKD switching elements 13 to 22 formed by logical combination of the square-wave signal sequences k to u and then combined in OR elements 23 and 24 to form the output signal sequences z1 and z2. In Fig. 5, the rectangular signal sequence are named immediately above each individual pulse, which contributed to the formation of the respective individual impulse. For education of the single impulses, the change in pairs turns out to be the change in the edge transitions of the square-wave signal sequences k to u as extremely favorable, because a direct AND link of the respective square-wave signal sequences is possible without prior inversion.

The output signal sequences z1 and Z2 become one not shown in FIG Pulse evaluation supplied. There they are used to generate counting pulses and enable the direction decision for the movement of the mechanical division and thus also the decision about the addition or subtraction operation in pulse counting. The counting pulses are formed in a known quadruple evaluation circuit. A counting pulse always appears when one of the output signal sequences Z1 or Z2 an O / L or L / O transition takes place.

The pulse period is therefore a factor of four compared to the period the output signal sequences z1 or z2 are shortened.

The interpolation factor of the entire facility is made up from a shortening factor that results from the shortening of the pulse period of the output signal sequences z1 and z2 compared to the pulse period of the square-wave signal sequences k to u, and the shortening factor of the quadruple evaluation circuit. Overall is specified in Example, an interpolation factor of twenty is achieved.

The invention is not limited to that indicated in FIG. 1 Arrangement of the photoelectric converters A to G. It is also possible to use the photoelectric To arrange transducers A to G in a line transverse to the direction of movement of the light signals. The light signals must then in addition to their intensity modulation in the direction of movement of the light signals also transversely to this direction of movement in a gradual or have constant phase shift.

The phase shift between any two selected output signals from the photoelectric converters A to G again corresponds to the relationship x nt and thus these output signals with the n are shown in FIG identical.

It is also conceivable to use the interpolation method according to the invention to be used in measuring devices in which the electrical primary signals pass through an inductive or capacitive measuring method can be obtained.

L e r s e i t e

Claims (5)

According to the invention, method for interpolating the division interval a mechanical division, in which a division cut off at an imaging point is optically mapped and generates intensity-modulated light signals in which the light signals are converted into quasi sinusoidal electrical signals that in n Eomperators from two quasi sinusoidal electrical signals Square-wave signal sequences are generated, the pulse edges of which are each by one Phase angle are offset, which results from the relationship nt, and at which to Evaluation of the mechanical shift of the graduation from these square-wave signal sequences Counting pulses for up-down counting are obtained, characterized in that that the two input signals for each comparator from a number a <n quasi sinusoidal and mutually phase-shifted signals, their phase relation to each other the relation x 22, with x being an arbitrary natural number from one to n - 1, is sufficient, to be selected. 2. The method according to item 1, characterized in that as input signals for each comparator signals with a constant phase difference of about - to t can be selected. 3. Procedure according to points 1 and 2, with the interpolation factors accordingly of the relationship 4 (2k-1), where k is any natural number, is used are, characterized in that the quasi sinusoidal signals the comparators be assigned in such a way that each two by the phase difference of their Pulse edges adjacent square-wave signal sequences at the output of the comparators O / L transition on these pulse edges, while the pulse edges of the subsequent rectangular pulses that are adjacent due to their phase shift have an L / 0-2 transition, so that the change in the edge transitions always occurs in pairs 1 change takes place. 4. Arrangement for interpolating the division interval of a mechanical Division, in which optical means for imaging a division section and for Conversion of this section into intensity-modulated light signals at the imaging point, Photoelectric converter for converting the light signals into quasi sinusoidal electrical ones Signals and a number n comparators are provided to get out of these sinusoidal Signals to generate square-wave signals, whose pulse edges to each other in each case are offset by a phase angle which results from the relationship n and where a logical network for evaluating the mechanical displacement of the division is arranged to count pulses for an up-down counting from these square-wave signal sequences to win, characterized in that to obtain the quasi sinusoidal and signals phase-shifted to one another at the imaging point have a number a c n photoelectric converter so one behind the other in the direction of movement of the light signals on a distance that corresponds to the period length of the intensity-modulated light signals corresponds, are arranged that the distance from the first photoelectric converter to the others, based on this period length, corresponds to the relationship x 2n $ t. n 5. Arrangement according to item 4, characterized in that for extraction the quasi sinusoidal and mutually phase-shifted signals at the imaging point a number a <n photoelectric converters in a line transverse to the direction of movement the light signals are arranged and that the light signals in addition to their intensity modulation in the direction of movement of the light signals transversely to this direction of movement, one step at a time or have constant phase shift in such a way that the phase position over two arbitrarily selected photoelectric converters always corresponds to the relationship x 2 # / n.