DE1953737A1 - Circuit arrangement for increasing the resolution of an electronic angle measuring device - Google Patents

Description

Patent attorney

Applicant: Philips Patentverwaltung GmbH.
File No. PHD- 1326

Registration dated: October 22, 1969

Philips Patentverwaltung GmbH, Hamburg 1, Mönckebergstr. 7th

Circuit arrangement for increasing the resolution of an electronic Angle measuring device

The invention relates to a circuit arrangement for increasing the resolution of an electronic angle measuring device, consisting of four partial disks, which are combined in pairs are that the disks of a first pair are each the same and preferably by 1 of the number of divisions of the disks of a second pair have a different number of pitches, one disk of the one pair with a disk of the The other pair is constantly rotating together, while one of the other two disks and the fourth disk are stationary is rotatable about the angle to be measured, and wherein the angle measuring device means for deriving an alternating voltage the frequency (speed of rotation of the rotating disks times the number of divisions per pair of graduated disks) and for generation of signals that mark a zero crossing of these alternating voltages once per revolution of the rotating disks, contains.

Such an arrangement for determining and digitally displaying the angular position of shafts is already known, see above

9/0723

e.g. from French patent specification 1,316,760. It consists of four! constantly rotating auxiliary rotor are attached, while of the other two the one disc with the measuring shaft is connected and the other disc serves as a reference disc. Each of the last-mentioned pulleys forms with one of the disks attached to the auxiliary rotor, a system for inductive voltage generation. The frequency of the stresses generated is equal to the number of divisions of the graduated disks combined in pairs in this way times the speed of rotation of the auxiliary rotor.

The division numbers are different for the two pairs of pulleys selected, preferably they differ by 1, so that one of the generated per revolution of the auxiliary rotor AC voltages one period more than the other.

Using FIGS. 1 a and 1 b, it will first be explained how this is produced in the known arrangement AC voltages the angular position of shafts can be determined. To this end, FIG. 1 shows a per period of the at the reference disk pair generated alternating voltage derived pulses i ^ and in the same way from the other Pair of disks derived impulses i «. Figure 1b shows the two pulse series in a different phase position.

Are, as given in the aforementioned French patent , means are provided that one pulse per revolution

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of the auxiliary rotor, then e.g. the pulse series i .., as indicated, viewed as a scale will. In FIG. 1a, the pulse of the series i ^ marked with 0 coincides with a pulse of the series ig.

FIG. 1b shows the row ig _{shifted against the row I 1} , as is effected by rotating a measuring shaft with a graduated disk attached to it. In this case, for example, the pulse 6 is coincident with a pulse of the series ig. For the sake of simpler description, coincidence ^ should also be understood as the generalization that two impulses in the series ig follow immediately after an impulse in the series i ^.

From Pigur 1a, b it can be seen that the coincidence from Pulse 0 runs through 9 until 0 again when the pulse series Ι «is shifted by one period.

Since the frequency ratio of the pulse series 1 * and ig is fixed by the division numbers η and n + 1 of the graduated disks and two of the disks are fixed together on a rotor, the speed of the rotor has basically no influence on the measurement result and a period of the pulse series i ₂ corresponds to a division of the associated pair of graduated disks. This means that the angle of this division by counting the impulses i «. from a marked pulse to the coincidence of two pulses of the series I ₁ and ig can be resolved into η parts. The full

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circle is therefore resolved into η (n + i) parts, with the result periodically about once per revolution of the auxiliary rotor is scanned. Corresponding arrangements can also be made for linear displacements.

With this known arrangement, a satisfactory resolution can be achieved with relatively coarse mechanical divisions. It is advantageous that the measurement result is scanned periodically. In this way it is possible to determine ^{angles n absolutely "without using code disks.}

In the above-mentioned French patent specification, a block diagram is also shown that is schematic shows how the signals supplied by the known arrangement are processed and one from a coarse and one from one Peinteil be fed to the existing meter. The whole divisions, as pain units, are used as coarse units to understand the η subunits per division.

The present invention is based on the task of resolving such a known arrangement to increase significantly.

This object is achieved in that a counter is provided which, from the beginning of the measuring cycle, is cycled through - Controlled electronic means known per se, in the times between traversed with the same sign

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Zero crossings of an alternating voltage and those of the second alternating voltage, counting pulses from a frequency generator synchronized with the speed of the rotating disks are supplied until the counter no longer receives pulses during one of these time periods have been supplied than corresponds to its counting capacity, and that the heating cycle is thus ended.

In this way, the resolution is improved by a factor k___ if k is the number of pulses that the Counters can record without overflowing. You synchronization between frequency generator and speed of rotating Sheaves are not a disadvantage because the pulleys have only slight fluctuations in rotational speed suffer and on the other hand a fluctuation of 5 # in principle an increase of the resolution to the 20-fold allowed. If the number of divisions of the discs is 200 and 201, for example then already resolved for less than 2 arc seconds. The circuit arrangement according to the invention replaces; the other necessary coincidence detection, so that only one rope of the effort is additionally necessary. It is advantageous here also that the unit of measurement of this interpolation is directly determined by the choice of the counting frequency / rotational speed ratio the pulley is infinitely variable.

The limit to which the resolution can still be usefully increased by the proposed arrangement is essentially determined by the sharpness with which the

109819/0723

Zero crossings of the alternating voltages can be recognized. It is only slightly dependent on secondary parameters, such as amplitude or harmonic content of the voltages, as is the case with other methods that aim for the greatest possible resolution with coarse ropes,

The invention will now be explained in more detail with reference to FIGS. 2a, b, c and 3.

Figures 2a to 2c show excerpts from the pulse trains i, and i «in different phases while FIG. 3 shows a block diagram of an exemplary embodiment shows.

As can be seen in FIG. 2a, any pulse has passed of the series i ^ to the next impulse of the series i «a lead t = t ... This is the lead for the next pair of pulses reduced to tg and amounts to for the next but one pulse pair t ~. The lead t ~ is already smaller than the maximum lead t___ according to FIG. 2b. But the

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Advance t. = ^ mer ei »® ^{11 is a} borderline case for which the next impulses are exactly coincident. If the lead amounts to t β 0 to t = * meT », ^this means that the measuring cycle of the fine measurement has ended. The amount of advance within these limits is a hatred by which the gradation of the fine measurement is interpolated. When thinking about the lead bit 53 * uncertainty, the phase position of the pulse trains and thus the angular position of the measuring shaft is determined 20 times more precisely than is the case with a simple coincidence calculation.

109819/0723

Mood is possible,

The operation of the embodiment shown in Figure 3 is as follows. A bistable multivibrator 1 is brought into the position in which a gate 2 of a counter 3 for the counting pulses of a frequency generator 4 is opened by a pulse of the series I _1. The frequency of this generator has a sufficiently constant ratio for the desired measurement accuracy to the rotational speed of the above-mentioned rotating graduated disks and thus to the frequency of the alternating voltage generated at the reference disk pair and the pulse sequence X ₁ derived therefrom. The counter 3 is said to have been set to the 0 position before the first pulse from the frequency generator 4 arrived. The means for this are familiar to every person skilled in the art and are therefore not shown. Simultaneously with the flip-flop 1, a further bistable flip-flop 5 is also activated by the pulse of the series i. switched, so that a signal is present at an input of an AND gate 6. If the next pulse of the series i «arrives before the counter 3 k pulses (k = capacity of the counter 3; it must be chosen to be t times the frequency of the generator 4), then appears after the pulse caused by the Row I ₂ caused switching of the flip-flop 1 at the output of the AND gate 6, a signal which leads to the interruption of the measuring cycle. The level k of the counter 3 reached up to that point is a measure of the angular position of the measuring shaft within the graduation of the fine measurement. That is why the gate becomes

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2 of counter 3 closed when switching over to flip-flop 1. The counter reading can be transferred to a memory 7 and then brought to O.

If, however, before the arrival of the impulse of the series ± 2 the counter 3 is more than k___. Pulses had been supplied

IuS X

so the lead t (Fig. 2) is even greater than t___, so

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is the flip-flop 5 through the transfer signal of the counter been brought into the complementary position. If the pulse of the series ip »appears, at the output of the gate 6 no signal appears, the measuring cycle of the fine measurement continues.

The frequency generator 4 can work at the same time as a clock pulse generator for the circuit. The means known per se for ensuring proper functioning of the circuit, for example an anti-coincidence circuit for the pulses of the series 1 _Λ and i ₉ , are not shown.

It is clear that for an increase in resolution by means of the circuit arrangement according to the invention only a small one Schaltungsauiwand is required. Weave the memory 7, the counter 3 can also be used as part of the measured value display are executed. The circuit arrangement described above can also be used to increase the resolution apply to the! learning of linear displacements Instead of the partial disks, corresponding scales take the place of the rotation of two disks Longitudinal oscillations h.

~ " Claims :

SAD ORfGiNAL 109819/0773 ---,

Claims (4)

_ Q - Patent claims: Mj Circuit arrangement for increasing the resolution of an electronic angle measuring device, consisting of four partial disks, which are combined in pairs so that the disks of a first pair each have the same number of divisions and preferably deviate by 1 from the number of divisions of the disks of a second pair, one disk of the one pair constantly rotates together with a disk of the other pair, while one of the other two disks is stationary and the fourth disk can be rotated by the angle to be measured, and the angle measuring device means for deriving an alternating voltage of the frequency (rotational speed of the rotating disks times the number of divisions each sub-disk pair) and for generating signals which mark a zero crossing of these alternating voltages once per revolution of the rotating disks, characterized in that a counter (3) is provided which, from the beginning of the measuring cycle, periodically, by per se known electr are supplied in the periods between traversed in the same sign sense Kulldurchgängen of an AC voltage, and those of the second alternating voltage counting pulses from a synchronized with the speed of the ro animal discs frequency generator (4) as long as onische means controlled by the counter (3) during these periods no more pulses have been supplied than corresponds to its counting capacity, and that the measuring cycle is thus ended. ' 109819/0723 - ίο - ■ - '■■ · 2. Circuit arrangement according to claim 1, characterized in that a first pulse series (I ₁ -) at the same time one input of two bistable multivibrators (1,5) and a second pulse series (i «) a second input of the first bistable multivibrator (1) that a first output of the first bistable multivibrator (1) is connected to a first input of a gate circuit (2) and the frequency generator (4) is connected to a second input of this gate circuit (2), the output of which is connected to a memory (7) connected counter (3), the output of which is connected to the second Input of the second bistable multivibrator (5) is fed, and that the second output of the first bistable Flip-flop (1) is connected to one input of an AND gate (6), the other input of which is at the output of the second bisbable trigger stage (5). 3. Circuit arrangement according to claim 1 or 2, characterized in that that the frequency generator (4) is also effective as a clock pulse generator. 4. Circuit arrangement according to one of claims 1 to 3, characterized in that the counter (3) and / or the memory (7) are designed as measured value indicators. 1 0 9 8 1 9/0 7 ? 3 ORIGINAL BATHROOM