DE2554771B2 - Arrangement for scanning a grid scale moved in a fixed direction - Google Patents

Description

The invention relates to an arrangement for scanning a moving in a fixed direction Grid scale for the generation of counting pulses while avoiding superimposed disruptive movements generated errors by moving against the specified direction while blocking the output from counting pulses to downstream processing elements, the counting pulses generated in a pre-, Down counters are totaled and after the transition of the disturbance movement in the specified direction the output of counting pulses is only released when the number of counting pulses that have occurred exceeds the sum of the counting pulses occurring in the opposite direction.

Such an arrangement is known. In this arrangement, the up and down counters have separate Inputs for the pulses assigned to the upward or downward counting direction. The well-known The arrangement is therefore only suitable for grid scales that are different for the two directions of movement Give impulses. Wrong path pulses are generated in the known arrangement by a gate circuit and flip-flops suppressed existing circuit. If more than two incorrect path pulses are suppressed should, the circuit complexity is high (DE-AS 12 71 413).

Also known is a circuit arrangement for eliminating interference pulses when scanning a Material measure incurred. The arrangement also only processes pulses, each in one counting direction assigned. The pulses corresponding to the two directions of movement are each assigned to a counter input an up and down counter via an interference signal suppression circuit and the other input supplied immediately. With this arrangement, only false counts due to brief glitches are avoided prevented (DE-AS 18 14 745).

Finally, there is also a discriminator circuit for forming the directional decision from two against each other phase-shifted pulse series known. (DD-PS 72 289).

The invention is based on the object of providing an arrangement of the type mentioned at the beginning to be further developed so that it eliminates errors even with larger disturbing movements of the grid scale Grid scales with different numbers of marks and different deflections of the disturbing movements can be easily adapted and still has a simple structure.

According to the invention, this object is achieved by combining the following features:

a) the up and down counter, whose predeterminable counting capacity is smaller than that when the The total length of the grid scale is the number of pulses, is designed to be preset and provided with only one counter input, the one with the values that occur in both directions of rotation Counting pulses can be applied,

b) The direction of counting is up and down counting

via a direction discriminator monitoring the direction of movement of the grid scale Moves in the specified direction to count up and reverse switchable to counting down,

c) with a sum of pulses corresponding to the preset value, the display is that of Counting pulses derived from the grid scale can be controlled via a gate circuit.

10

By increasing the counting capacity, this arrangement can be implemented without changing the circuit structure Adapt larger disturbance fluctuations with numerous counting impulses occurring for each excursion. the Setting can be done on the spot, e.g. B. at the '5 Commissioning. The preset value can be based on the size of a The maximum deflections arising in the system are adjusted with the addition of a safety value.

The counting capacity or the preset value of the up / down counter is preferably set to the size of the Game of a drive device set. Such a game occurs e.g. B. between tension spindles and spindle nuts on. There may also be play in gears. When the direction of rotation is reversed then the spindle nut or the output shaft of the gear will only settle after it has been winched of the game in motion. The grid scale that is predominantly connected directly to the drive element on the other hand begins to move immediately. By setting the counting capacity or the preset value depending on the size of the game, the delivery of counting pulses is blocked until the game is overcome is. The arrangement works without specifying its own control command to which the direction of movement J5 assigned. Furthermore, the arrangement has the advantage that not only is the game balanced, but also the delivery of counting pulses in the event of disruptive vibrations until they die out Vibrations is prevented. * n

In an expedient embodiment it is provided that from the grid scale two signals phase-shifted by 90 ° from one another can be generated, which can be fed to the direction discriminator, in which one signal can trigger two monostable flip-flops, each with the positive or negative signal edge, so that the flip-flops each have two Feed NAND gates, two of which can be supplied with the second signal and two with the inverted second signal and that the NAND gates acted upon by the non-inverted and inverted signal are connected to a further NAND gate, the further NAND gates having inputs an ftS flip-flop are connected downstream, with the output of which the presetting of the counter is connected. This v direction discriminator contains two monostable flip-flops and some NAND gates. The cost of components is therefore low. In addition to the signals indicating the direction of movement, the arrangement also supplies impulses which are passed on to downstream devices for counting when the to grid scale is running smoothly.

The arrangement described above also works properly if a directional discriminator is used which instead of a pulse doubling one of the κ division of the marks of the grid scale corresponding Number of counting pulses or a pulse quadrupling caused.

A favorable embodiment is that the Counter input of the counter via an OR gate with the inverted signal of the carry output and with Counting pulses of the grid scale .can be applied, that the carry output of the counter is still connected to a NOR gate, at whose output the Counting pulses can be removed, and that the second input of the NOR element receives the counting pulses via a negative pulse edges delaying circuit can be supplied. The training of the counting pulses downstream devices depends on the level of the carry signal, which is at the maximum count changes with the switchover from up to down counting. With the help of the time delay, achieve that a countdown pulse following the countdown pulses the counter to count down switches over, the count is reduced by one and against the forwarding to downstream facilities Is blocked.

The invention is described below with reference to an embodiment shown in a drawing explained in more detail, from which further features and advantages result. It shows

F i g. 1 shows an overview circuit diagram of an arrangement for scanning a grid scale and for generating it of counting pulses,

F i g. 2 further details of the in F i g. 1 shown circuit arrangement,

3 shows a diagram of the time course of Signals at certain points of the in F i g. 2 arrangement shown.

A grid scale 1 in the form of a disk, which is positively connected to a shaft of a machine, not shown in detail, contains a number of optically, electrically or magnetically scannable elements 2 evenly distributed over the circumference. Two probes 3, 4 are close to the disk 1 arranged for the scanning of the elements 2. The distance between the probes 3, 4 is selected so that two signals, which are phase-shifted by 90 ° with respect to one another, occur at the probe outputs and are fed to pulse shaping stages 5, 6. The pulse shaping stages 5, 6 give at their outputs 7, 8 two square-wave signals A, flab which are phase-shifted by 90 ° with respect to one another, the time course of which is shown in FIG. 3 is shown.

A direction discriminator 9, with which the direction of movement of the disk 1 is monitored, is connected to the outputs 7, 8. It is assumed that the disk 1, when the shaft connected to the disk 1 is running properly, is in the position shown in FIG. 1 with 33 designated direction of rotation moves. The direction of movement detection circuit 9 contains two outputs 10, 11. A signal V is available at output 10, the binary value of which indicates the direction of rotation of disk 1. Take that in Fig. 3 signal V represented a binary "1", then the disc 1 rotates in the direction 33. When the Signa! If a binary “0” leads, the disk 1 rotates in the opposite direction to the direction 33. The counting pulses obtained by scanning the elements 2 appear at the output U. A counting and blocking circuit 12 is connected to the outputs 10, 11. If the disk 1 rotates in the direction indicated by 33 without vibrations being superimposed on the rotary movement, then the counting and blocking circuit 12 forwards the counting pulses specified via the connection 11 to its output 13. As soon as the disk 1 rotates in the opposite direction to 33,

transfer. However, during this time the counting pulses occurring at connection 11 are added up and saved. If the movement of the superimposed oscillation is reversed again, then it will indeed rotate Disk 1 again in direction 33, but the forwarding of the counting pulses remains blocked until a The number of pulses corresponding to the sum of the counted pulses has arisen. Exceeds the number If the accumulated pulses change the saved value, the counting pulses are again sent to the output

13 transferred.

The direction of movement detection circuit 9 contains two monostable flip-flops 14, 15, which with the Output 7 are connected. The monostable multivibrator

14 is stimulated to emit a pulse by a positive signal edge at its input. the Trigger stage 15 emits a pulse when the signal edge goes negative. The non-inverting outcome of the Trigger stage 14 feeds two NAND elements 16, 17. Another two NAND gates 18, 19 are connected to the non-inverting one Output of flip-flop 15 connected. While the NAND gates 16, 19 directly to the output 8 are placed, the NAND gates 17, 18 are connected to the output 8 via an inverter element 20. the NAND elements 16, 18 feed a NAND element 21. A NAND element 22 is connected to the NAND elements 17, 19 tied together. In the case of the NAND elements 21, 22, inverting elements 23, 24 are connected downstream to the AND gate 25 is connected, which feeds the output 11. The inverters 23, 24 are each with one The input of an AES flip-flop consisting of two NAND gates 26, 27 is connected, its non-inverting Output is applied to terminal 10.

The output 10 is applied to the control input for upward and downward counting of a counter 28. Of the The counter input of the counter 28 is connected to an OR gate 29, which is supplied by an inverter 30 and the output Ii is fed. The counter 28 responds to positive signal edges am Counting input on. The carry output of the counter 28 is connected to the inverter 30 and one input NOR gate 31 connected, which feeds the output 13. The second input of the NOR gate 31 is via a Pulse delay circuit 32 is applied to output 11. The pulse delay circuit 32 includes unspecified elements, e.g. B. a resistor, a capacitor and a diode in parallel is put to resistance. The series connection of resistor and capacitor forms an integrating element. With the aid of the diode, the positive signal edges are instantaneously transmitted via the delay circuit 32 headed.

In the one shown in FIG. 3 shown time diagram of Signaiesi tier in F ι g. The circuits shown in i and 2 show the time t in the abscissa direction and the two binary values "0" and "1" for each signal in the ordinate direction. In the NAND gates 16 and 19 are emitted by the monostable multivibrators 14, 15 pulses are with the signal generated by the pulse shaper 6 square-wave signal B associated Assume that the signal is shifted in phase B relative to A by 90 ° lagging when the Disk 1 rotates in direction 33 Since the short-term impulses of flip-flop 14 have decayed before the transition of signal B to the binary value "1", the binary value "1" is available at the output of NAND element 16. Likewise, the short-term pulses emitted by flip-flop 15 have already decayed before the transition of signal B to a binary "0", so that the output of NAND element 18 also has a binary "1". In contrast, the pulses generated by the flip-flops 14, 15 at the NAND gates 17, 19 meet with the signal B or the inverted signal from B. This means that the outputs of the NAND elements 17, 19 assume the binary values "0" for the duration of these pulses The pulse of the flip-flops 14, Ii has the binary value "1" and otherwise corresponds to the binary "0". The signal output by the NAND gate 2Ά , which is shown in FIG. 3 is denoted by Iv, the direction of rotation 33 of the disk 1 is assigned. There; NAND element 21 has binary "1" signals applied to both inputs and therefore emits a binary "0". The output signal of the NAND element 21, to which the direction opposite to the direction 33 is assigned, corresponds to a binary "0". Di (after inversion in element 24, counting pulses of signal Iv reach AND gate 25, whose output signal Z is transmitted to output 11. which sets the counter 28 to count up via the output 10. The signal at the overflow output of the up / down counter is denoted by £ 7 in Fig. 3. As long as the counter 2i has not reached its maximum count, ei indicates its overflow output therefore has a binary “1” at one input of the OR element 29. The counting pulses at output 11 are therefore sent via the OR element 29 as a signal CL to the counter 28 and increase its count Due to the binary "1" at the overflow output de: counter 28, the NOR element 31 is caused to output a binary "0". The formation of the count pulses to output 13 is therefore blocked Sign al therefore has a binary "0".

When the content of the counter 28 has reached the maximum counting capacity, the signal C changes from a binary “1” to a binary “0”. The time of this change is shown in FIG. 3 denoted by t \ The transition takes place with a certain signal delay after the positive edge of the counting pulse. The signal delay is caused by the transit times in the counter 28. The counting pulse that has increased the count to the maximum value cannot pass the NOR element 31 due to the delay in running time. After the signal L has been switched to a binary "0", the OR element 29 and the counting input of the counter 28 are constantly subjected to a binary "1". The counter 28 is thus blocked. The pulses of the signal Z reach the NOR element 31, one input of which is acted upon by the binary "0" of the overflow output of the counter 28. The NOR element 31 therefore forwards the pulses at its input in an inverted manner to the output 13. After the time fi, counting pulses appear at the output 13, the downstream ones , not shown devices are supplied. The maximum count of the counter 28 is smaller than the number of pulses occurring when scanning a full revolution of the disk 1.

If the disk 1 starts up at the beginning of an operation, the counting pulses of the signal T

to downstream facilities at time t \ .

It is assumed that the direction of rotation of the disk 1 is reversed at the point in time fc due to a superimposed oscillation. In this case, signal B leads signal A by 90 °. When the signal B is combined with the pulses generated by the flip-flops 14, 15, the signal Iv at the NAND element 22 is a binary “0”. On the other hand, pulses now appear at the output of the NAND element 21 as signal Ir , the first of which resets the flip-flop via the inverter 23. The reset takes place with the positive edge of this pulse. Therefore the signal V at the preset input of the counter 28 changes from a binary “1” to a binary “0”. This causes a switchover of the signal Ü from a binary “0” to a binary “1”, since a different maximum count is decisive for the overflow display when counting down

Since the switching of the signal Ü is triggered by the negative going edge of the counting pulse Z, the binary "0" is present at the OR element 29 when the positive going edge of the counting pulse on the OR gate 29 arrives. The counting pulse is therefore used at the same time to reduce the count of the counter 28. By the signal delay in the element 32, the negative going edge of the count arrives at a time to the NOR gate 31 to which the signal Ü already has a binary "1", the count is thus not forwarded to the output 13 reduce all counts of signal Ir the content of the counter 28, while at the output 13 no counting pulse occurs.

At time h , the direction of the superimposed oscillation is reversed and runs according to direction 32. The counting pulses therefore occur again at the output of NAND element 22 and switch counter 28 to count up via the flip-flop. However, since the content of the counter 28 is less than the maximum count, the binary "1" is still present at the daytime output, with which the NOR element 31 is blocked against the forwarding of counting pulses. The counting pulses increase the count. As soon as the maximum count is reached, the processes described above in connection with time fi occur and the counting pulses then reach output 13.

In the case of superimposed vibrations, counting pulses are generated from the time the direction of movement is reversed to not forwarded at the point in time when the disk 1 returned to before the start of the fault assumed position has arrived. This prevents post-filtering devices Receive counting pulses that have been caused by disruptive vibrations.

The device of the type described above can advantageously be used in machine tool controls can be used with incremental measurement of the actual position values. The Use device when capturing the

! 5 angles of rotation! by means of a rotating disk 1 the increment method takes place.

It is sufficient if the circuits connected to the output 13, in which z. B. Actual value counter are used for position control devices, only work in one counting direction. By using this Elements result in considerable savings in terms of circuitry. Since the superimposed disturbance movements in usually only have small amplitudes, the counting capacity of the up / down counter 28 can be small.

This means a further reduction in effort.

The arrangement described above works both

when moving in the direction 33 as well as when the disk 1 moves in the opposite direction. With the switchover of the directions of movement becomes one that corresponds to the counting capacity or the preset value Number of pulses blocked. This property can be exploited to get the correct number of counting pulses despite play in the drive elements. The counting capacity or the The preset value is set to a value that corresponds to the clearance. There are several Advantages. Despite the reversal of the direction of movement and play in the drives, the position of the is always closed The corresponding number of counting pulses is output for the controlling element. A separate signal that the Switching of the direction of movement reports to the downstream position control loops, is already in the direction discriminator contain. This signal can be sent to the control inputs for the counting direction of the actual value counter the position control loops are placed.

1 sheet of drawings

Claims (4)

Patent claims: I. Arrangement for scanning a grid scale moved in a fixed direction for the generation of counting pulses while avoiding those generated by superimposed perturbing movements Errors by moving against the specified direction while disabling the output of counting pulses to downstream processing elements ι ο the counting pulses incurred in an up, down counter are added up and the output of counting pulses only after the disturbance movement has passed in the specified direction is released when the number of counting pulses occurred is opposite to the sum of the Direction of counting pulses incurred, marked by the union following features: a) the up, down counter (28), its predeterminable Counting capacity less than that when scanning the entire length of the grid scale The number of pulses incurred is designed to be pre-settable and with only one counter input provided, which can be acted upon with the counting pulses occurring in both directions of rotation is, b) the counting direction of the up and down counter (28) is the direction of movement of the Directional discriminator (9) monitoring the grid scale when moving in the specified area Direction (33) to count up and in the opposite direction to count down switchable; c) with a sum of pulses corresponding to the preset value, the display is that of Counting pulses derived from the grid scale (1) can be controlled via a gate circuit (31). 2. Arrangement according to claim 1, characterized in that the counting capacity or the presetting «ο value of the up, down counter (28) is set to the size of the game of a drive device. 3. Arrangement according to claim 1 or 2, characterized in that from the grid scale (1) two 90 ° phase-shifted signals (A, B) can be generated, which can be fed to the direction discriminator (9), in which a signal (A) two monostable multivibrators (14, 15) can each be triggered with the positive or negative signal edge that the multivibrators (14, 15) each feed two NAND elements (16, 17, 18, 19), two of which (16, 19 ) with the second signal (B) and two (17, 18) are acted upon by the inverted second signal (B) and that in each case by the non-inverted and inverted signal (B) applied NAND gates (16, 19 and 17, 18 ) are connected to a further NAND element (22, 21), the further NAND elements (22, 21) being followed by inputs of an Ä5 flip-flop (26, 27), with its output (10) of the counting direction device output of the counter (28) is connected. 4. Arrangement according to claim 1 or one of the following, characterized in that the counting input of the counter (28) via an OR gate (29) with the inverted signal (Ü) of the carry output and counting pulses of the grid scale (1) can be acted upon is that the carry output of the counter (28) is still connected to a NOR element (31), at whose output (13) the counting pulses can be removed, and that the second input of the NOR element (31) transfers the counting pulses a circuit (32) delaying negative pulse edges can be supplied.