EP2017678B2 - Method and device for transferring signals from a positioning device to an evaluation unit - Google Patents

Abstract

The transmission of rectangular position signals with reference pulses to an evaluation unit, for two moving machine tool components, the reference pulses (RI) are coupled to the position signals (P1,P2). When there is a faulty condition, a warning signal (WRN) is generated.

Description

The invention relates to a method and a device for transmitting position signals and reference pulses as well as an error condition indicating warning signals from a position-measuring device to an evaluation unit according to the preamble of claims 1 and 7.

A position measuring device is used to determine the relative position of two mutually movable objects, for example, two mutually movable machine parts of a machine tool. For this purpose, a material measure, for example in the form of a scale graduation, connected to one and a scanning unit with the other of the two objects, so that can be determined by scanning the scale division, the extent of movement of the two objects to each other along the scale division. The generation of position signals by means of the position measuring device takes place by scanning, for example by optical scanning, the scale division by means of a transducer of the position measuring device during the relative movement of the scanning unit and the scale division. By arranging the scanning unit, on the one hand, and the graduation scale, on the other hand, to one of the two mutually movable objects, the respective position of the one object can be determined with respect to the other object, either in the form of an absolute position using a scale scale formed by a code track, or in the form of relative position changes when using an incremental, periodic scale scale. The generation of the different types of position signals can be effected by using optical, magnetic, inductive or capacitive scanning units.

When using an incremental position measuring device for position measurement produced by sampling a periodic scale division by means of the sampling on the output side at least two mutually phase-shifted, periodic analog position signals that are evaluated to determine the relative position of the graduation scale and the scanning in an evaluation unit, for example, from a numerical control of a Machine tool exists.

The incremental position signals generated by the position measuring device are transmitted in parallel form to the downstream evaluation unit via two or four signal transmission lines, depending on the type of transmission. In the case of the incremental position signals during the relative movement of scale graduation and scanning unit, the position measuring device delivers two position signals which are phase-shifted by 90 ° in the case of a single-ended transmission. In a differential transmission, an inverse position signal is additionally transmitted from the position measuring device to the evaluation unit for each of the two position signals which are phase-shifted by 90 °.

In addition to the position signals and possibly inverted position signals, reference pulses are transmitted from the position measuring device to the evaluation unit, which are generated by linking reference pulse signals derived from reference marks on the graduation scale with the position signals. In a single-ended transmission, a reference pulse is transmitted via a further signal transmission line to the evaluation unit and further processed there, while in a differential transmission two further signal transmission lines are provided, via which a reference pulse and an inverted reference pulse are transmitted.

In addition to the incremental position signals and the reference pulses, the position measuring device can issue a warning signal to the evaluation unit if, for example, the permissible signal amplitudes are undershot or other events which jeopardize safe operation occur, that of a position measuring device connected to or integrated in the position measuring device Warning signal donating monitoring unit are detected. To transmit the warning signal from the position measuring device to the evaluation is transmitted via an additional output of the position measuring device and an additional warning signal transmission line, a single-ended signal to the evaluation, which assumes a high level, for example, in the normal state, when transmitting rectangular warning signals with logical high and low levels, while the warning state corresponds to a low level.

Disadvantage of this type of transmission of a warning signal is that a separate warning signal transmission line is required, which precludes the requirement to minimize the number of required signal transmission lines between the position measuring device and the downstream evaluation unit. In addition to avoiding unnecessary cabling, the compatibility with the hitherto customary number of signal transmission lines should be ensured in the transmission of possibly desired additional signals as possible.

The JP 64-50785 A proposes to transmit a plurality of position signals in a multiplex mode via a signal line. In this way signal transmission lines are saved.

Alternatively, all the outputs of the position measuring device can be switched to high impedance for warning signal output, so that in the warning state instead of the differential signals only present signals with the same level, the subsequent electronics the evaluation unit recognizes as a fault condition. This type of transmission of a warning signal has the advantage that the warning signal does not require its own warning signal transmission line and that in addition a line break the warning signal transmission line can be detected, since in this case the low-level of the subsequent electronics of the evaluation unit, which corresponds to a warning state. A major disadvantage of this type of transmission of a warning signal is that in the warning state, the transmission of all signals is interrupted and provided with the position measuring machine must be stopped immediately.

The object of the present invention is to specify a method and a device of the type mentioned above, which require no additional signal transmission line for the transmission of a warning signal and also enables a transmission of the position signals and the reference pulses in the warning state.

This object is achieved by a method having the features of claim 1 and a device having the features of claim 7.

The solutions of the invention require no additional signal transmission line for transmitting a warning signal from the position measuring device to the evaluation and thus meet the requirement to keep the cost of required signal connections as low as possible and to ensure compatibility with the usual number of signal transmission lines. In addition, the inventive method and the device according to the invention ensure that the incremental position signals and reference pulses can continue to be transmitted in the warning state, so that the machine equipped with the position measuring device does not have to be stopped immediately when a warning state occurs.

Since it is at a slow feed and at a standstill of the machine, for example, while holding an axis of a machine tool on a certain position, it may happen that over a longer period there is no possibility to transmit a warning signal from the position measuring device to the evaluation because the invalid for the transmission of the warning signal in normal operation for the output of the reference pulse RI condition combination of the position signals P1 = 0 AND P2 = 0 does not occur, the time that has elapsed since the last occurrence of the state combination invalid for the transmission of the reference pulse (RI) and when a predetermined time has elapsed and a warning signal indicating an error condition is detected is determined during slow feed or standstill of the machine transmit an alarm signal to the evaluation unit. In this case, the invalid for the transmission of the reference pulse state combination is forced to transmit the alarm signal and transmit the alarm signal as a warning signal.

Since the evaluation unit detects the slow speed or the standstill of the machine by the transmission of position signals and reference pulses, it evaluates the transmission of warning signals at slow feed or standstill of the machine as an alarm signal that leads to shutdown of the machine and / or one with appropriate programming corresponding acknowledgment of the alarm signal requires. After a manual acknowledgment and / or removal of the error state associated with the separate alarm message, the controller returns to the normal state.

The inventive solutions are based on the idea to use the warning signal using the existing signal transmission lines for the transmission of the position signals and reference pulses, preferably the signal transmission lines of the reference pulses, in a single-ended transmission or in a differential transmission, for the distinction between a reference pulse and a a warning signal indicating a warning signal in the normal operation for the output of the reference pulse invalid state combination of the position signals and reference pulses is used.

verknüpft werden. Bei Erfassung eines Fehlerzustandes wird ein Basis-Warnsignal WRN' erzeugt, das mit den Positionssignale P1 und P2 verknüpft und als Warnsignal WRN entsprechend der eine ungültige Zustandskombination darstellenden Bedingung $$\left[\mathrm{WRN}\prime \mathrm{=High}\right]\mathrm{UND}\left[\mathrm{P}1=\mathrm{P}2=\mathrm{Low}\right]$$

abgegeben wird.At least two essentially rectangular, phase-shifted, incremental position signals P1, P2 are derived from scanning signals of an incremental graduation of a scale graduation of the position measuring device, analog reference pulse signals derived from reference marks of the graduation scale and rectangular base reference pulses RI 'formed with the position signals P1 and P2 for a position signal P1 and P2 valid state combination to reference pulses RI according to the condition $$\left[\mathrm{RI}\text{'}=\mathrm{High}\right]\mathrm{AND}\left[\left[\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="imgf0001.png"\; state="\{\{state\}\}">P</figure-callout>}1\mathrm{OR\; <figure-callout\; id="2"\; label="P"\; filenames="imgf0003.png"\; state="\{\{state\}\}">P</figure-callout>}2\right]=\mathrm{High}\right]$$

be linked. Upon detection of an error condition, a base warning signal WRN 'is generated, which is associated with the position signals P1 and P2 and as a warning signal WRN corresponding to the invalid condition combination representing condition $$\left[\mathrm{WRN}\text{'}\mathrm{=\; high}\right]\mathrm{AND}\left[\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="imgf0001.png"\; state="\{\{state\}\}">P</figure-callout>}1=\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="imgf0003.png"\; state="\{\{state\}\}">P</figure-callout>}2=\mathrm{low}\right]$$

is delivered.

The output of the warning signal is possible both in a single-ended transmission and in a differential transmission, wherein in a single-ended transmission two phase-offset position signals and one with the phase-shifted position signals in error-free normal operation periodically occurring valid state combinations associated reference pulse is transmitted from the position measuring device to the evaluation, while at a differential transmission at least four incremental position signals, each with two offset by 90 ° phase first position signals and two to the first position signals inverted second position signals and one in error-free normal operation to periodically occurring valid state combinations associated with the first position signals first reference pulse and each one in error-free normal operation periodically occurring valid state combinations with the second position signals link be transmitted second reference pulse.

A device for transmitting substantially rectangular position signals and reference pulses and an error condition indicating warning signals from a position measuring device for determining the position of two relatively movable parts of a machine via signal transmission lines to an evaluation unit, wherein the position measuring device comprises a logic unit consisting of scanning signals of an incremental graduation scale graduation phase-offset incremental position signals and a reference pulse generated from reference marks of the scale graduation and the position signals is characterized in that the logic unit generates the reference pulse RI from the phase-shifted, incremental position signals P1, P2 and from the reference marks of the scale graduation such that in the error-free state in Each state valid and invalid for the output of the reference pulse RI state combinations occur, and one an error state indicating warning signal WRN during an error-free state for the output of the reference pulse RI invalid state combination of the position signals P1, P2 and the reference pulse RI in the signal transmission from the position measuring device to the evaluation unit, and that the evaluation unit has an error detection unit that during a fault-free State for the output of the reference pulse RI invalid state combination of the position signals P1, P2 and the reference pulse RI transmits transmitted warning signal WRN from the signal transmission.

In order to transmit a warning signal even at a slow feed and at standstill of the machine, although for the transmission of the warning signal in normal operation for the output of the reference pulse RI invalid state combination of the position signals P1 = 0 AND P2 = 0 does not occur, the logic unit contains a Time step, which is initiated with the occurrence of the invalid for the transmission of the reference pulse state combination and outputs a signal to a first input of an AND gate after a predetermined period of time, the second input can be acted upon by a warning signal and an alarm signal to the evaluation outputs when a signal is present at both inputs. To transmit the alarm signal invalid for the transmission of the reference pulse state combination is forced and transmit the alarm signal as a warning signal. By acknowledging the alarm signal transmitted as a warning signal on the side of the evaluation unit, the control returns to the normal state, if necessary after the elimination of a fault condition.

The condition [RI = High] AND [P1 = P2 = Low] preferably applies as an invalid state combination of the position signals P1 and P2 and of the reference pulse RI. Alternatively, however, any other state combinations of the position signals P1 and P2 and the reference pulse RI can be selected as an invalid state combination for the transmission of a warning signal, for example the combination [[P1 = Low] OR [P2 = Low]], if the reference pulse RI in normal operation at [P1 = P2 = High].

• mit einer Positionssignal-Erzeugungseinheit, die die aus den Abtastsignalen der Inkrementalteilung der Maßstabteilung phasenversetzten inkrementalen Positionssignale P1, P2 erzeugt und an die Logikeinheit abgibt,
• mit einer Referenzimpuls-Erzeugungseinheit, die die Referenzmarken der Maßstabteilung erfasst und aus dem resultierenden analogen Referenzimpulssignal einen rechteckförmigen Basis-Referenzimpuls RI' bildet und an die Logikeinheit abgibt, und
• mit einer Überwachungseinheit, die bei der Erfassung eines Fehlerzustandes ein Basis-Warnsignal WRN' erzeugt und an die Logikeinheit abgibt,

verbunden, verknüpft die Positionssignale P1 und P2 mit dem Basis-Referenzimpuls RI' und gibt einen Referenzimpuls RI ab, wenn die Bedingung $$\left[\mathrm{RI}\prime =\mathrm{High}\right]\mathrm{UND}\left[\left[\mathrm{P}1\mathrm{ODER\; P}2\right]=\mathrm{High}\right]$$

erfüllt ist, verknüpft die Positionssignale P1, P2 mit dem Basis-Warnsignal WRN' verknüpft und gibt ein Warnsignal WRN ab, wenn die Bedingung $$\left[\mathrm{WRN}\prime =\mathrm{High}\right]\mathrm{UND}\left[\mathrm{P}1=\mathrm{P}2=\mathrm{Low}\right]$$

erfüllt ist.In a preferred embodiment, the logic unit is on the input side

• with a position signal generating unit that generates and outputs to the logic unit the incremental position signals P1, P2 phase-offset from the scanning signals of the incremental graduation of scale graduation,
• with a reference pulse generating unit which detects the reference marks of the scale division and from the resulting analog reference pulse signal forms a rectangular base reference pulse RI 'and outputs to the logic unit, and
• with a monitoring unit which generates a base warning signal WRN 'when detecting an error condition and outputs it to the logic unit,

Connects the position signals P1 and P2 with the base reference pulse RI 'and outputs a reference pulse RI, if the condition $$\left[\mathrm{RI}\text{'}=\mathrm{High}\right]\mathrm{AND}\left[\left[\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="imgf0001.png"\; state="\{\{state\}\}">P</figure-callout>}1\mathrm{OR\; <figure-callout\; id="2"\; label="P"\; filenames="imgf0003.png"\; state="\{\{state\}\}">P</figure-callout>}2\right]=\mathrm{High}\right]$$

is satisfied links the position signals P1, P2 to the base warning signal WRN 'and outputs a warning signal WRN if the condition $$\left[\mathrm{WRN}\text{'}=\mathrm{High}\right]\mathrm{AND}\left[\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="imgf0001.png"\; state="\{\{state\}\}">P</figure-callout>}1=\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="imgf0003.png"\; state="\{\{state\}\}">P</figure-callout>}2=\mathrm{low}\right]$$

is satisfied.

Since the logic unit determines the valid state combinations from the combination of the position signals with the base reference pulses to the reference pulses and this link the program of the evaluation is known, the evaluation recognizes a fault condition during the occurrence of a signal during an invalid state combination and can be a preprogrammed response, for example Immediately stop the machine.

This form of information transmission from the position measuring device to the evaluation unit can be further refined by the fact that, in the event of a transmission of a warning signal exceeding a predetermined signal length, the machine is stopped immediately, while if the warning signal has a signal length which is less than the predetermined signal length, only an optical and / or acoustic signal, optionally coupled with an indicating the cause of error indicator corresponding to the respective signal length, is triggered.

On the output side, the logic unit is connected to an input of a reference pulse driver module or a differential driver.

The error detection unit is the input side with outputs of signal receivers or differential signal receivers of the evaluation unit for phase-shifted incremental position signals and reference pulses and the output connected to a signal output unit.

Depending on whether a single-shot transmission or a differential transmission of the position signals and reference pulses is provided between the position measuring device and the evaluation unit, at least three signal transmission lines are arranged between the position measuring device and the evaluation unit, on which two phase-shifted incremental position signals and one associated with the incremental position signals reference pulse of the position measuring device to the evaluation unit are transmittable or arranged at least six signal transmission lines on which two phase-shifted incremental position signals and two incremental position signals inverted thereto and each associated with the phase-shifted incremental position signals and the incremental position signals associated therewith reference pulse from the position measuring device to the evaluation are transferable.

Fig. 1

ein schematisches Blockschaltbild einer Positionsmesseinrichtung, die für eine Eintaktübertragung über drei Signalübertragungsleitungen mit einer Auswerteeinheit verbunden ist;

Fig. 2

Impulsdiagramme eines Basis-Referenzimpulses, eines BasisWarnsignals, zweier zueinander um 90° phasenversetzter inkrementaler Positionssignale und eines aus einer Verknüpfung des Basis-Referenzimpulses mit den inkrementalen Positionssignalen gebildeten Referenzimpulses sowie eines während einer im Normalbetrieb für die Ausgabe des Referenzimpulses ungültigen Zustandskombination abgegebenen Warnsignals und

Fig. 3

ein schematisches Blockschaltbild einer Positionsmesseinrichtung, die für eine differentielle Signalübertragung über sechs Signalübertragungsleitungen mit einer Auswerteeinheit verbunden ist.

On the basis of exemplary embodiments illustrated in the drawing, the idea underlying the invention and further features and variants of the invention will be explained. Show it:

Fig. 1

a schematic block diagram of a position measuring device, which is connected for a single-ended transmission via three signal transmission lines with an evaluation unit;

Fig. 2

Pulse diagrams of a base reference pulse, a base warning signal, two mutually offset by 90 ° incremental position signals and a reference pulse formed from a combination of the base reference pulse with the incremental position signals and a during a normal operation for the output of the reference pulse invalid state combination emitted warning signal and

Fig. 3

a schematic block diagram of a position measuring device, which is connected for differential signal transmission via six signal transmission lines with an evaluation unit.

Fig. 1 shows a block diagram of a position measuring system with a position measuring device 1, which comprises a scale graduation 2 and a scanning unit 3 movable relative thereto. The position measuring device 1 generates position signals P1, P2 and a reference pulse RI linked to the position signals P1, P2, which signals are transmitted via signal transmission lines 51, 53, 55 to an evaluation unit 4. The graduation scale 2 and the scanning unit 3 are connected, for example, to mutually movable parts of a machine tool whose relative position is to be determined to each other, while the evaluation unit 4 consists for example of a numerical machine tool control or integrated into it.

Alternatively to the in Fig. 1 illustrated embodiment of a linear movement of the mutually movable parts, the solution according to the invention can also be used in position measuring systems with rotational movements of the mutually movable parts.

The graduation scale 2, for example in the form of a glass scale, contains an incremental graduation 21 with a predetermined graduation period and reference marks 22. The generation of the position signals P1, P2 and reference pulses RI can be performed using optical or photoelectric, magnetic, inductive or capacitive sensing principles with appropriate graduation scale design 2 and the scanning unit 3 done. For example, when using a photoelectric measuring principle in the transmitted light method, the graduation scale of a glass scale with a graduated graduation as incremental graduation and reference mark consist, which is associated with a scanning plate at a small distance to the glass scale. A parallel light beam generated by a semiconductor light source projects a plurality of scanning fields of the scanning plate onto the glass scale, behind the scanning fields associated with the photodiodes are arranged. Since the pitch of the scanning fields is the same as that on the glass scale and aligned parallel thereto is, with a relative movement of the glass scale and the scanning the transmitted luminous flux is modulated, which is converted in the photodiodes with the light intensity due to the opaque lines on the glass scale varying light intensity in a corresponding electric current. By mutual offset of the scanning fields, the signals of the photodiodes can be phase-shifted. These signals can be converted into square-wave signals using circuit means known per se.

Alternatively, using the photoelectric measuring principle, a reflection or incident light method can be used in which the scale consists of a nontransparent material to which the graduation of a highly reflective material is applied.

The sampling unit 3 includes a position signal generation unit 5 which outputs two incremental signals 90 ° out of phase as position signals P1, P2, and a reference pulse generation unit 6 which generates a rectangular base from a reference mark 22 detected by the sampling unit 3 and the resulting analog reference pulse signal Reference pulse RI 'forms.

The position signal generation unit 5 and the reference pulse generation unit 6 comprise a plurality of light sources, scanning structures on the graduation scale 2 and optoelectronic detector elements when using the photoelectric measuring principle.

In a relative movement of graduation scale 2 and the scanning unit 3 of the position signal generating unit 5, the two phase-offset by 90 ° position signals P1, P2 at the in Fig. 1 shown single-ended transmission in parallel to two downstream first and second driver modules 31, 32, whose outputs are connected via two signal transmission lines 51, 53 to the inputs of a respective signal receiver 41, 42 of the evaluation unit 4.

erfüllt ist. Der so erzeugte Referenzimpuls RI wird von der Logikeinheit 7 über einen Treiberbaustein 33 und eine Signalübertragungsleitung 55 zu einem Signalempfänger 43 der Auswerteeinheit 4 übertragen. Gleichzeitig legt die Logikeinheit 7 damit die gültige Zustandskombination bei der Übertragung des Referenzimpulses RI fest.The reference pulse RI is formed in the logic unit 7 by a combination of the output from the reference pulse generating unit 6 base reference pulse RI 'with the two phase-shifted by 90 °, formed as rectangular pulses position signals P1 and P2, if they are at high potential or are logical high, ie if the condition $$\mathrm{RI}\text{'}=\mathrm{High\; AND}\left[\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="imgf0001.png"\; state="\{\{state\}\}">P</figure-callout>}1\mathrm{OR\; P2}=\mathrm{High}\right]$$

is satisfied. The reference pulse RI thus generated is transmitted from the logic unit 7 via a driver module 33 and a signal transmission line 55 to a signal receiver 43 of the evaluation unit 4. At the same time sets the logic unit 7 so that the valid state combination in the transmission of the reference pulse RI.

Fig. 2 shows from top to bottom timing diagrams of the base reference pulse RI ', the base warning signal WRN', the two phase-shifted by 90 ° and formed as rectangular pulses position signals P1 and P2 and from the above-described combination of the base reference pulse RI 'with the position signals P1 and P2 formed reference pulse RI over the phase angle φ.

From the combination of the base reference pulse RI 'with the phase-shifted, incremental position signals P1, P2 results as a valid state combination on the signal transmission line 55 for the transmission of the reference pulse RI the condition: $$\left[\mathrm{RI}=\mathrm{High}\right]\mathrm{AND}\left[\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="imgf0001.png"\; state="\{\{state\}\}">P</figure-callout>}1\mathrm{OR\; <figure-callout\; id="2"\; label="P"\; filenames="imgf0003.png"\; state="\{\{state\}\}">P</figure-callout>}2=\mathrm{High}\right]$$

ein Signal übertragen wird.A state combination that is invalid in normal operation or in the fault-free state of the signal generation for the output of the reference pulse RI thus results in the case of a deviation from the above condition. This invalid for the output of the reference pulse RI condition combination of the position signals P1, P2 and the reference pulse RI is used according to the invention for the transmission of a warning signal WRN, so that a warning state is detected by the evaluation unit 4, if invalid during the output of the reference pulse RI state combination $$\left[\mathrm{RI}=\mathrm{High}\right]\mathrm{AND}\left[\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="imgf0001.png"\; state="\{\{state\}\}">P</figure-callout>}1=\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="imgf0003.png"\; state="\{\{state\}\}">P</figure-callout>}2=\mathrm{low}\right]$$

a signal is transmitted.

erfüllt ist. Das rechteckförmige Warnsignal WRN wird über den weiteren Treiberbaustein 33 und die Signalübertragungsleitung 55 für den Referenzimpuls RI an die Auswerteeinheit 4 abgegeben.A monitoring unit 8 arranged in or connected to the scanning unit 3 gives a basic warning signal WRN 'when a fault condition is detected, for example when the permissible signal amplitudes are undershot. to the input side connected both to the outputs of the position signal generating unit 5 and to the output of the reference pulse generating unit 6 logic unit 7. By linking the position signals P1, P2 with the base reference pulse RI ', the logic unit 7 determines the valid and invalid for the output of the reference pulse RI condition combinations of the position signals P1, P2 and the reference pulse RI, so that the logic unit 7 in the presence of a normal operation for the output of the reference pulse RI invalid state combination and a pending at your connection with the monitoring unit 8 basic warning signal WRN 'a rectangular warning signal WRN according to Fig. 2 then spend if the condition $$\left[\mathrm{WRN}\text{'}=\mathrm{High}\right]\mathrm{AND}\left[\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="imgf0001.png"\; state="\{\{state\}\}">P</figure-callout>}1=\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="imgf0003.png"\; state="\{\{state\}\}">P</figure-callout>}2=\mathrm{low}\right]$$

is satisfied. The rectangular warning signal WRN is output to the evaluation unit 4 via the further driver module 33 and the signal transmission line 55 for the reference pulse RI.

The evaluation unit 4 comprises, in addition to the signal receivers 41, 42, 43, an error detection unit 10 which is connected on the input side to the outputs of the signal receivers 41, 42, 43 and which is connected on the output side to a signal output unit 9. The signal output unit 9 is connected, for example, to or integrated in a numerical machine tool control and has a monitor or is connected to optical and / or acoustic signal transmitters.

The error detection unit 10 is used to detect valid and for the output of the reference pulse RI invalid state combinations of the position signals P1, P2 and the reference pulse RI and indicates at a in the range of an invalid for the output of the reference pulse combination RI base warning signal WRN 'a warning signal WRN the signal output unit 9 of the evaluation unit 4, which outputs a suitable optical and / or acoustic signal or engages in the numerical machine tool control.

This in Fig. 1 schematically illustrated block diagram is essentially the explanation of the functional relationship in the detection, generation and transmission of the position signals P1 and P2, the base reference pulse RI ', the reference pulse RI, the base warning signal WRN' and the warning signal WRN. However, the individual components of the position-measuring device 1 and evaluation unit 4 can deviate from the in Fig. 1 illustrated embodiment and linked together. Thus, for example, the reference pulse generating unit 6 can be integrated into the logic unit 7, which additionally monitors the signal amplitudes of the scanning signals and reference marks in order to detect, for example, falling below predetermined signal amplitudes for an error message. In the same way, the error detection unit 10 can be integrated into the signal output unit 9 with corresponding logic modules.

The solution according to the invention can of course also be used in a position measuring system with differential signal transmission. An embodiment of this is in Fig. 3 illustrated in the form of a schematic block diagram, which substantially with the block diagram of a position measuring system with a single-ended transmission according to Fig. 1 , is consistent, so that reference is made to the above description.

In this embodiment, generated by the position signal generating unit 5, 90 ° out of phase incremental signals are output as position signals P1, P2 to downstream first and second differential drivers 34, 35 from the two position signals P1 and P2 both position signals P1 +, P2 + and this inverted position signals P1-, P2- generate and transmitted via a total of four signal transmission lines 51 to 54 in parallel to first and second differential receiver 44, 45 of the evaluation unit 4. The position measuring device 1 thus provides with a relative movement of graduation scale 2 and scanning unit 3 two phase-shifted by 90 ° incremental and to each of the two phase-shifted incremental an inverted incremental signal, which is also transmitted to the evaluation unit 4 for further processing via the signal transmission lines 51 to 54.

In the same way by means of the reference pulse generating unit 6, the generation of a base reference pulse RI 'in a known manner at one or more known relative positions of scale division 2 and scanning unit 3. The base reference pulse RI' is in the downstream logic unit 7 with the Position signals P1, P2 to the reference pulse RI as described above in connection with the description of the circuit according to Fig. 1 linked and delivered to a downstream third differential driver 36 of the sampling unit 3, which generates from the reference pulse RI a reference pulse RI + and a reference pulse RI- inverted thereto. Both reference pulses RI + and RI- are transmitted via signal transmission lines 55, 56 to the inputs of a third differential receiver 46 of the evaluation unit 4, which at its output formed from the reference pulse RI + and the inverted reference pulse RI- reference pulse RI to the signal output unit 9 and error detection unit 10th the evaluation unit 4 outputs.

der Positionssignale P1+, P1-, P2+, P2- und Referenzimpulse RI+, RI- ein Warnsignal WRN+, WRN- auf den Signalübertragungsleitungen 55, 56 der Referenzimpulse RI+, RI- an die Auswerteeinheit 4 abgibt.The monitoring unit 8 is connected to the position signal generating unit 5 and the reference pulse generating unit 6 for detecting the signal amplitudes and / or a unit outputting a fault condition and outputs, for example, when falling below allowable signal amplitudes at its output from a basic warning signal WRN 'to the logic unit 7, which in an invalid during normal operation for the output of the reference pulse RI state combination $$\left[\mathrm{RI}=\mathrm{High}\right]\mathrm{AND}\left[\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="imgf0001.png"\; state="\{\{state\}\}">P</figure-callout>}1=\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="imgf0003.png"\; state="\{\{state\}\}">P</figure-callout>}2=\mathrm{low}\right]$$

the position signals P1 +, P1-, P2 +, P2- and reference pulses RI +, RI- a warning signal WRN +, WRN- on the signal transmission lines 55, 56 of the reference pulses RI +, RI- to the evaluation unit 4 outputs.

The solution according to the invention thus makes it possible to transmit a warning signal WRN or WRN + and WRN- from the position measuring device 1 to the downstream evaluation unit 4 using only the existing signal transmission lines 51 to 53 or 51 to 56 in the case of a single-ended transmission as well as a differential signal transmission that no additional cabling is required. In addition, the compatibility with the number of previous connections between the position-measuring device 1 and the evaluation unit 4 is ensured and the warning signal WRN or the warning signals WRN + and WRN can or can in the warning state with continuous transmission of the position signals P1, P2; P1 +, P1-, P2 +, P2- and the reference pulse RI; RI +, RI-, so that the machine controlled by the position measuring system does not have to be stopped immediately when a warning condition occurs.

At a slow feed and at a standstill of the relatively movable parts of the machine, for example, when stopping an axis of a machine tool at a certain position, it may happen that for a long period of time there is no possibility to issue a warning signal, because the state P1 = 0 AND P2 = 0 does not occur.

In order to be able to issue a warning to the evaluation unit 4 in this state as well, in particular if there is an error state which requires an immediate shutdown of the machine, a time step is provided in the logic unit 7 which is initiated with the event P1 = P2 = Low and after a predetermined time period outputs a signal to a first input of an AND gate whose second input can be acted upon by the warning signal issued by the monitoring unit 8 and which emits an alarm signal to the evaluation unit 4 if a signal is present at both inputs.

After a RESET of the evaluation unit 4 after removal of the error state and acknowledgment of the alarm message, the normal control described above can be continued with, if appropriate, a transmission of warning signals.

Claims (13)

1. Method for the transmission of position signals and reference pulses together with warning signals specifying a fault state from a position measuring device for purposes of determining the position of two parts of a machine moving relative to one another to an analysis unit,
   characterized in that the reference pulses (RI; RI+, RI-) are combined with the position signals (P1, P2: P1+, P1-, P2+, P2-) such that in the fault-free state in each period valid state combinations and invalid state combinations for the output of the reference pulse (RI; RI+, RI-) occur, and in that the warning signals (WRN) specifying a fault state are transmitted during a state combination of the position signals (P1, P2; P1+, P1-, P2+, P2-) and reference pulses (RI; RI+, RI-) which is invalid in the fault-free state for the output of the reference pulse (RI; RI+, RI-) and in that with a slow feed or in the stationary state of the machine the time is determined that has elapsed since the occurrence of the state combination which is invalid for the transmission of the reference pulse (RI), and in the event of exceedance of a prescribed timespan and the occurrence of a warning signal (WRN) indicating a fault state an alarm signal is transmitted in a forced manner to the analysis unit (4) and in that for the transmission of the alarm signal the state combination which is invalid for the transmission of the reference pulse (RI) is forced, and the alarm signal is transmitted in the same manner as a warning signal.
2. Method according to Claim 1,
   characterized in that the warning signals (WRN) are transmitted on signal transmission lines (55, 56) of the reference pulse (RI) or the reference pulses (RI; RI+, RI-) .
3. Method according to at least one of the preceding claims
   characterized in that from sampling signals of an incremental scale (21) of a scale division (2) of the position measuring device (1) at least two essentially rectangular-shaped, phase-displaced, incremental position signals (P1, P2) are generated, in that analogue reference pulse signals are derived from reference marks (22) of the scale division (2) and rectangular-shaped base reference pulses (RI') are formed, in that a base warning signal (WRN') is generated in the registering of a fault state, in that the position signals (P1, P2) and base reference pulses (RI') for a valid state combination are combined into reference pulses (RI) corresponding to the condition: $$\left[\mathrm{RI}\prime =\mathrm{High}\right]\mathrm{AND}\left[\left[\mathrm{P}1\mathrm{OR\; P}2\right]=\mathrm{High}\right]$$

   

   and in that the position signals (P1, P2) are combined with the base warning signal (WRN'), and a warning signal (WRN) is delivered if the condition: $$\left[\mathrm{WRN}\prime =\mathrm{High}\right]\mathrm{AND}\left[\mathrm{P}1=\mathrm{P}2=\mathrm{Low}\right]$$

   

   is met.
4. Method according to at least one of the preceding claims,
   characterized by a single transmission of two phase-displaced position signals (P1, P2) and a reference pulse (RI) combined with the phase-displaced position signals (P1, P2) in fault-free normal operation into periodically occurring valid state combinations.
5. Method according to at least one of the preceding Claims 1 to 4,
   characterized by a differential transmission of at least four incremental position signals (P1+, P1-, P2+, P2-) with, in each case, two first position signals (P1+, P2+), phase-displaced by 90°, and two second position signals (P1-, P2-) inverted relative to the first position signals (P1+, P2+), and in each case a first reference pulse signal (RI+) combined with the first position signals (P1+, P2+) in fault-free normal operation into periodically occurring valid state combinations, and in each case a second reference pulse signal (RI-) combined with the second position signals (P1-, P2-) in fault-free normal operation into periodically occurring valid state combinations.
6. Method according to one of the preceding claims,
   characterized in that on receipt of a warning signal the analysis unit (4) requests an acknowledgement before it returns to the normal control operation.
7. Device for the transmission of essentially rectangular-shaped position signals and reference pulses together with warning signals specifying a fault state from a position measuring device via signal transmission lines to an analysis unit for purposes of determining the position of two parts of a machine moving relative to one another, wherein the position measuring device has a logic unit, which from sampling signals of an incremental scale of a scale division delivers phase-displaced, incremental position signals and a reference pulse generated from reference marks of the scale division and the position signals,
   characterized in that the logic unit (7) generates the reference pulse (RI) from the phase-displaced, incremental position signals (P1, P2) and from the reference marks of the scale division such that in the fault-free state in each period valid and invalid state combinations for the output of the reference pulse (RI) occur, and inserts a warning signal (WRN) indicating a fault state, during a state combination of the position signals (P1, P2) and the reference pulse (RI), which is invalid in the fault-free state for the output of the reference pulse (RI), into the signal transmission from the position measuring device (1) to the analysis unit (4), and in that the analysis unit (4) has a fault detection unit (10) that filters out from the signal transmission the warning signal (WRN) that is transmitted during a state combination of the position signals (P1, P2) and the reference pulse (RI) which is invalid in the fault-free state for the output of the reference pulse (R1) and in that the logic unit (7) contains a time stage, which is initiated with the occurrence of the state combination which is invalid for the transmission of the reference pulse, and after a prescribed timespan delivers a signal to a first input of an AND circuit, to whose second input can be applied a warning signal (WRN), and that delivers an alarm signal, if a signal is present at both inputs and in that for the transmission of the alarm signal the state combination which is invalid for the transmission of the reference pulse (RI) is forced, and the alarm signal is transmitted in the same manner as a warning signal.
8. Device according to Claim 7,
   characterized in that as an invalid state combination of the position signals (P1, P2) and the reference pulse (RI) the condition: $$\left[\mathrm{RI}=\mathrm{High}\right]\mathrm{AND}\left[\mathrm{P}1=\mathrm{P}2=\mathrm{Low}\right]$$

   

   applies.
9. Device according to Claim 7 or 8,
   characterized in that the logic unit (7) on the input side is connected

   - to a position signal generation unit (5), which generates phase-displaced, incremental position signals (P1, P2) from the sampling signals of the incremental scale (21) of the scale division (2) and delivers these to the logic unit (7),

   - to a reference pulse generation unit (6) which registers the reference marks (22) of the scale division (2) and from the resulting analogue reference pulse signal forms a rectangular-shaped base reference pulse (RI') and delivers this to the logic unit (7), and

   - to a monitoring unit (8), which in the event of registering a failure state generates a base warning signal (WRN') and delivers this to the logic unit (7), in that the logic unit (7) combines the position signals (P1, P2) with the base reference pulse (RI'), and delivers a reference pulse (RI), if the condition: $$\left[\mathrm{RI}\prime =\mathrm{High}\right]\mathrm{AND}\left[\left[\mathrm{P}1\mathrm{OR\; P}2\right]=\mathrm{High}\right]$$

   

   is met,

   and in that the logic unit (7) combines the position signals (P1, P2) with the base warning signal (WRN') and delivers a warning signal (WRN) if the condition: $$\left[\mathrm{WRN}\prime =\mathrm{High}\right]\mathrm{AND}\left[\mathrm{P}1=\mathrm{P}2=\mathrm{Low}\right]$$

   

   is met.
10. Device according to at least one of the preceding Claims 7 to 9,
    characterized in that on the output side the logic unit (7) is connected to an input of a reference pulse driver module (33) or a difference driver (36).
11. Device according to at least one of the preceding Claims 7 to 10,
    characterized in that the fault detection unit (10) is connected on the input side to outputs from signal receivers (41 - 43) or difference signal receivers (44 - 46) of the analysis unit (4) for the phase-displaced, incremental position signals (P1, P2; P1+, P1-, P2+, P2-) and reference pulses (RI; RI+, RI-), and on the output side to a signal output unit (9).
12. Device according to at least one of the preceding Claims 7 to 11,
    characterized in that between the position measuring device (1) and the analysis unit (4) at least three signal transmission lines (51 - 53) are arranged, on which the position signals (P1, P2) and the reference pulse (RI), or the warning signal (WRN) indicating a fault state during the state combination which is invalid for the output of the reference pulse (RI) in the fault-free state, can be transmitted from the position measuring device (1) to the analysis unit (4).
13. Device according to at least one of the preceding Claims 7 to 11,
    characterized in that between the position measuring device (1) and the analysis unit (4) at least six signal transmission lines (51 - 56) are arranged, on which two phase-displaced, incremental position signals (P1+, P2+), together with two phase-displaced, incremental position signals (P1-, P2-) inverted relative to the former, a reference pulse (RI+) and a reference pulse (RI-) inverted relative to the former, or the warning signals (and the warning signals inverted relative to the former (WRN+; WRN-)) indicating a fault state during the state combination which is invalid for the output of the reference pulses (RI+;RI-) in the fault-free state, can be transmitted from the position measuring device (1) to the analysis unit (4).

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