JP5892844B2 - Position detection device - Google Patents

Description

  The present invention relates to a position detection device installed in an industrial machine, a machine tool, or the like, and more particularly to a position detection device designed to achieve functional safety.

  In recent years, machine tools (numerical control machine tools) using a numerical control device (CNC) with a built-in computer have become widespread, and automation and labor saving have been promoted in the machining field.

  The numerically controlled machine tool includes a drive mechanism that moves an object, a position sensor that measures the current position of the object, and a CNC controller that controls the drive mechanism based on the position information.

  The position sensor includes a linear encoder that detects a linear position and a moving distance, and a rotary encoder that detects a rotation angle.

  Taking a magnetic scale as an example, a detection head provided with an MR element whose resistance value varies with the magnetic field strength is arranged and moved on the magnetic pattern of the scale material. The detection head is provided with two MR elements separated by a quarter wavelength to determine the moving direction. These two signal outputs have a relationship between a sine wave and a cosine wave, and when plotted on the XY axes, a circle that makes a round with a moving distance of one division of the magnetic pattern is drawn. The moving direction can be detected based on the rotational direction of the circle, and the moving distance can be detected based on the accumulated rotational speed.

  Further, by obtaining the current angle on the circumference by interpolation processing by digital signal processing, it becomes possible to detect more detailed positions between the scales and increase the resolution. Depending on the number of divisions in this interpolation process, the minimum resolution = the magnetic pattern 1 scale / the number of divisions is determined.

  Due to recent demands for avoiding serious danger accidents / functional safety / reliability improvement, especially position sensors (position detection devices), which are the basic information for positioning control, need to ensure detection safety and functional safety / reliability for the position information. It has become.

  Since abnormal operation of electrical equipment can lead to serious accidents, manufacturers are required to enhance safety functions. In addition, strict safety standards have been established in order to keep the danger to the human body within an acceptable range at each stage of product development, design, production, maintenance, and disposal. For example, a functional safety standard (IEC61508) established by IEC (International Electrotechnical Commission) has been established.

  Therefore, in the positioning mechanism equipped in industrial machines and machine tools, in order to ensure functional safety / reliability, the internal processing of the position sensor is duplicated, and each position detection result is compared to detect an abnormality. (For example, refer to Patent Document 1).

WO2010 / 023896

  By the way, in order to ensure functional safety / reliability in positioning mechanisms equipped in industrial machines and machine tools, when the internal processing of the position sensor is duplicated, the interpolation processing circuit, counter, and communication control from the head. It is ideal to duplicate everything up to the part, but since the interpolation control circuit to the communication control unit are large and expensive, the duplication greatly affects the size and price of the position sensor.

  Moreover, from the viewpoint of functional safety, errors in the micrometer order do not pose a danger to the human body, and detection of abnormalities in the millimeter order is sufficient.

  Therefore, the present invention has been made in view of the above-described conventional situation, and the object of the present invention is to secure functional safety and simplify the circuit configuration for detecting an abnormality. It is to provide a detection device.

  Other objects of the present invention and specific advantages obtained by the present invention will become more apparent from the description of embodiments described below.

  In the present invention, the minimum resolution obtained by interpolating one wavelength of the first wavelength from the detection signal of the first wavelength obtained by reading the first measurement scale from the first scale by the first detection head. A first position signal of the unit is generated, and a second position signal is generated from the detection signal of the second wavelength obtained by reading the second length measurement scale from the second scale by the second detection head. A third position signal is generated from the detection signal of the first wavelength obtained by the first detection head, and abnormality detection is performed by comparing the second position signal and the third position signal. Do.

  That is, the position detection apparatus according to the present invention is configured to detect 1 of the first wavelength from the detection signal of the first wavelength obtained by reading the first length measurement scale from the first scale by the first detection head. A first signal processing unit that generates and outputs a first position signal in the minimum resolution unit interpolating the wavelength, and a second measurement scale that is obtained by reading the second measurement scale from the second scale by the second detection head. A second signal processing unit that generates and outputs a second position signal from the detection signal of the second wavelength, and a third position from the detection signal of the first wavelength obtained by the first detection head. A third signal processing unit that generates and outputs a signal, a second position signal obtained from the second signal processing unit, and a third position signal obtained from the third signal processing unit are compared. And a first comparison processing unit. And detecting an abnormality based on the comparison result by parts.

  For example, the position detection device according to the present invention compares the first position signal obtained from the first signal processing unit with the third position signal obtained from the third signal processing unit. And a first position signal obtained by the first signal processor and a second position signal obtained by the second signal processor, and the first comparison processor and the second An abnormality can be detected based on both comparison results by the two comparison processing units.

  In the position detection device according to the present invention, the second signal processing unit may be a unit obtained by dividing the second wavelength by a natural number with respect to the detection signal of the second wavelength obtained by the second detection head. The second position signal is generated by cumulatively adding the first count value for each length, and the third signal processing unit detects the first wavelength obtained by the first detection head. For the signal, the third position signal is generated by accumulating and adding the second count value for each unit length obtained by dividing the first wavelength by a natural number, and the unit length corresponding to the first count value The length obtained by dividing the length by the first count value is the same as the length obtained by dividing the unit length corresponding to the second count value by the second count value. Can be.

Further, in the position detection apparatus according to the present invention, the third signal processing unit is configured so that the detection signal of the first wavelength obtained by the first detection head is a multiple of the minimum resolution unit. The third position signal is generated by cumulatively adding the natural number obtained by dividing the first wavelength for each wavelength obtained by dividing the first wavelength by the natural number, and the second comparison processing unit generates the first comparison signal. The count result of the first position signal for each minimum resolution unit by the signal processing unit and the cumulative addition result of the third position signal obtained from the third signal processing unit can be compared.
The third signal processing unit cumulatively adds a second count value for each length obtained by dividing the first wavelength by a natural number for the detection signal of the first wavelength obtained by the first detection head. The third position signal is generated, and the second comparison processing unit counts the minimum position unit of the first position signal by the first signal processing unit and the third signal. The result obtained by comparing the cumulative addition result of the third position signal obtained from the processing unit and dividing the unit length corresponding to the second count value by the second count value is the minimum It can be the same as an integral multiple of the resolution.

  Further, in the position detection device according to the present invention, each signal processing unit outputs a position signal expressed as binary position information, and the comparison unit is the highest position signal expressed as the binary position information. The position signal can be compared with a numerical value obtained by extracting only a predetermined number of digits from

  In the present invention, from the detection signal of the first wavelength obtained by reading the first length measurement scale from the first scale by the first detection head, the first signal processing unit 1 of the first wavelength is obtained. A first position signal in the minimum resolution unit in which the wavelength is interpolated is generated, and the second wavelength detection signal obtained by reading the second length measurement scale from the second scale by the second detection head is used. The second position signal is generated by the second signal processing unit, and the third position signal is generated by the third signal processing unit from the detection signal of the first wavelength obtained by the first detection head. Since abnormality detection is performed by comparing the second position signal and the third position signal with the first comparison unit, the circuit configuration for performing abnormality detection can be simplified. And a second comparison processing unit that compares the first position signal obtained from the first signal processing unit and the third position signal obtained from the third signal processing unit. Abnormalities can be detected based on both comparison results by the comparison processing unit and the second comparison processing unit, and functional safety can be improved with a simple configuration.

It is a block diagram which shows the structural example of the position detection apparatus to which this invention is applied. It is a block diagram which shows the specific structural example of the signal processing part in the said position detection apparatus. It is a block diagram which shows the other structural example of the signal processing part in the said position detection apparatus. It is a figure which shows typically the state from which the expression unit of the 2nd position signal POS2 which is the count value of 1st position signal POS1 which comes from the minimum resolution of an interpolation process, and the count value of a length measurement scale differs. It is a block diagram which shows the other structural example of the signal processing part in the said position detection apparatus. It is the block diagram which attached | subjected and showed the specific processing content in the said signal processing part. It is a figure which shows typically the state which made the binary count expression of 1st position signal POS1 which comes from the minimum resolution of an interpolation process, and the expression unit of 2nd position signal POS2 which is a count value of a length measurement scale correspond. .

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.
The present invention is applied to, for example, a position detection apparatus 100 configured as shown in the block diagram of FIG.

  The position detection device 100 reads the first length measurement scale recorded on the first scale 10A of the scale unit 10 with the first detection head 20A of the head unit 20 and reads the first position by the signal processing unit 30. A signal POS1 is generated, and the generated first position signal POS1 is sent as position information to an external CNC controller 200. The first length measurement scale is read from the first scale 10A by the first detection head 20A. A first signal for generating a first position signal POS1 having a minimum resolution unit λ1 / N by interpolating one wavelength of the first wavelength λ1 into N divisions from the detection signal S1 of the first wavelength λ1 obtained as described above. The signal processing unit 30 includes a processing unit 31A.

  The position detecting device 100 is configured to ensure functional safety by duplication, and the scale unit 10 includes a second scale 10B on which a second length measurement scale is recorded. In addition, the head unit 20 is provided with a second detection head 20B that reads a length measurement scale recorded on the second scale 10A. Further, the signal processing unit 30 receives the second detection signal S2 having the second wavelength λ2 obtained by reading the second length measurement scale from the second scale 10B by the second detection head 20B. A third position signal POS3 is generated from the second signal processing unit 31B that generates and outputs the position signal POS2 and the detection signal S1 of the first wavelength λ1 obtained by the first detection head 20A. The third signal processing unit 31C to output, the first position signal POS1 obtained by the first signal processing unit 31A, the second position signal POS2 obtained by the second signal processing unit 31B, and the third signal The position information comparison unit 32 to which the third position signal POS3 obtained by the processing unit 31C is supplied, and the generated first position signal POS1 and second position signal POS2 are converted to an external CNC controller. A communication control unit 33 for sending to the roller 200 is provided.

  In the signal processing unit 30 in the position detection device 100, the first signal processing unit 31A performs N-division interpolation processing from the detection signal S1 of the first wavelength λ1 obtained by the first detection head 20A. The first position signal POS1, which is precise position information with the minimum resolution λ1 / N, is generated, and the second wavelength λ2 obtained by the second detection head 20B by the second signal processing unit 31B. The second position signal POS2, which is rough redundant position information, is generated from the detection signal S2, and the third signal processing unit 31C detects the first wavelength λ1 obtained by the first detection head 20A. A third position signal POS3, which is rough redundant position information, is generated from the signal S1.

  Based on the generated first position signal POS1, second position signal POS2, and third position signal POS3, the position information comparison unit 32 verifies that the error range is required for functional safety. The first position signal POS1 that is precise position information and the second position signal POS2 that is redundant position information are sent to the external CNC controller 200 by serial communication via the communication control unit 33.

  The external CNC controller 200 can make an abnormality determination using the first position signal POS1 that is precise position information and the second position signal POS2 that is redundant position information.

  As the signal processing unit 30 in the position detection apparatus 100, for example, a signal processing unit 30A configured as shown in the block diagram of FIG. 2 can be used.

  In the signal processing unit 30A, the first signal processing unit 31A generates N wavelengths of the first wavelength λ1 from the detection signal S1 of the first wavelength λ1 obtained by the first detection head 20A. It comprises an interpolation processing circuit 311A that generates and outputs a first position signal POS1 having a minimum resolution unit λ1 / N by divisional interpolation.

  The second signal processing unit 31B performs the first trigger once per wavelength of the second wavelength λ2 from the detection signal S2 of the second wavelength λ2 obtained by the second detection head 20B. A first trigger signal generation unit 311B that generates and outputs a signal TG1, and a resolution of the second wavelength λ2 by counting the first trigger signal TG1 output from the first trigger signal generation unit 311B It comprises a first counter 312B that generates and outputs a second position signal POS2 as a unit.

  Further, the third signal processing unit 31C performs the second trigger once per wavelength of the first wavelength λ1 from the detection signal S1 of the first wavelength λ1 obtained by the first detection head 20A. A second trigger signal generation unit 311C that generates and outputs a signal TG2, and the second trigger signal TG2 output from the second trigger signal generation unit 311C is counted to resolve the first wavelength λ1. It comprises a second counter 32C that generates and outputs a third position signal POS3 as a unit.

  In the signal processing unit 30A, the position information comparison unit 32 includes the second position signal POS2 obtained by the second signal processing unit 31B and the third position obtained by the third signal processing unit 31C. The first comparison processing unit 321A to which the signal POS3 is supplied, the first position signal output unit 322A to which the first position signal POS1 obtained by the first signal processing unit 31A is supplied, and the second A second position signal output unit 322B to which a second position signal POS2 obtained by the signal processing unit 31B is supplied, and the second position signal POS2 obtained by the second signal processing unit 31B and the third position signal POS2 When the third position signal POS3 obtained by the signal processing unit 31C matches, the first position signal POS1 obtained by the first signal processing unit 31A is changed to the first position signal POS3. Output from the signal output section 322A.

  When the second position signal POS2 obtained by the second signal processing unit 31B and the third position signal POS3 obtained by the third signal processing unit 31C do not match, the first comparison processing unit 321A It is determined as an abnormal state, and an abnormality detection signal indicating an abnormal state is output to the first position signal output unit 322A, and the first position signal POS1 is output from the first position signal output unit 322A. To prevent.

  The first position signal output unit 322A receives the first position obtained from the first signal processing unit 31A when the abnormality detection signal obtained by the first comparison processing unit 321A does not indicate an abnormal state. The signal POS1 is output to the communication control unit 33. The second position signal output unit 322B outputs the second position signal POS2 obtained from the second signal processing unit 31B to the communication control unit 33.

  Here, when λ1 = λ2, that is, when the wavelength of each length measurement scale recorded on the first scale 10A and the second scale 10B is equal, the second counter 10B to the first counter 312B. If the system up to and the system from the first scale 10A to the second counter 312C are not abnormal, the count results of the first counter 312B and the second counter 312C match, so the first comparison The processing unit 321A directly compares the second position signal POS2 obtained from the second signal processing unit 31B with the third position signal POS3 obtained from the third signal processing unit 31C. An abnormality detection signal can be output.

  Further, when λ1 ≠ λ2, that is, when the wavelengths of the length measurement scales recorded on the first scale 10A and the second scale 10B are not equal, for example, α = λ2 / λ1, The result of multiplying the count result by the counter 312C by the coefficient α by the multiplier 313 is compared with the count result by the first counter 312B, so that an abnormality detection signal can be output in the case of mismatch.

  Further, like the signal processing unit 30B shown in FIG. 3, the second signal processing unit 31B uses a first trigger for the detection signal S2 of the second wavelength λ2 obtained by the second detection head 20B. In the signal generator 311B, the first trigger signal TG1 is generated for each unit length λ2 / m obtained by dividing the second wavelength λ2 by the natural number m, and the first count value (for each first trigger signal TG1) For example, the second position signal POS2 is generated by accumulating the natural number m), and the third signal processing unit 31C generates the detection signal S1 of the first wavelength λ1 obtained by the first detection head 20A. The second trigger signal generation unit 311C generates the second trigger signal TG2 for each unit length λ1 / n obtained by dividing the first wavelength λ1 by the natural number n, and for each second trigger signal TG2, 2 counts The second position signal POS2 obtained from the second signal processing unit 31B in the first comparison processing unit 321A is generated by accumulating values (for example, a natural number n) to generate the third position signal POS3. Can be compared with the third position signal POS3 obtained from the third signal processing unit 31C, and an abnormality detection signal can be output in the case of a mismatch.

  In the signal processing units 30A and 30B, the second wavelength λ2 that is coarser than the first position signal POS1 of the minimum resolution unit λ1 / N generated by the first signal processing unit 31A and its natural number are reduced. The first comparison processing unit 321A compares the second position signal POS2 having a resolution unit with the third position signal POS3 having the first wavelength λ1 and a natural fraction thereof as a resolution unit. Detection can be performed, functional safety can be ensured, and a configuration for detecting an abnormality can be simplified.

  Here, the multiplication processing by the multiplier 313 in the signal processing unit 30A requires an enormous number of multipliers, but the signal processing unit 30B can detect an abnormality without requiring an enormous number of multipliers. The configuration for detecting an abnormality can be further simplified.

  From a functional safety standpoint, micrometer-order errors do not pose a danger to the human body, and millimeter-order abnormality detection is sufficient. Therefore, as in the signal processing units 30A and 30B, functional safety is obtained by comparing the second position signal POS2 and the third position signal POS3 obtained by counting the change points of the length measurement scale without the interpolation circuit. Should be satisfied. In this case, in functional safety for the purpose of reducing the dangerous failure rate, it is required to simplify and simplify the generation and comparison of the second position signal POS2 and the third position signal POS3. The range is not large and in most cases the same wavelength will be employed.

  However, generally, the minimum resolution of the position sensor is required to be a good number such as 1, 2, 5, 10 and the numerical expression of the first position signal POS1 which is precise position information is a binary count in the minimum resolution unit. Since the wavelength of the length measurement scale is determined by other factors such as the position sensor method, reliability, use environment, and manufacturing convenience, the minimum resolution of the second position signal POS2 that is the count value of the length measurement scale. Is not necessarily a power relationship of the first position signal POS12.

  Therefore, as shown in FIG. 4, the binary count representation of the first position signal POS1 that comes from the minimum resolution of the interpolation process and the representation unit of the second position signal POS2 that is the count value of the length measurement scale are different. Therefore, the numerical comparison requires unification of numerical units, and mathematical processing of multiplication or division by a position sensor or a CNC controller is required.

  In the position detection apparatus 100, by using, for example, a signal processing unit 30C configured as shown in the block diagram of FIG. 5 as the signal processing unit 30, a binary count expression of the first position signal POS1 and a length measurement scale are used. The unit of expression of the second position signal POS2, which is the count value, can be unified.

  In the signal processing unit 30C, the first signal processing unit 31A subtracts one wavelength of the first wavelength λ1 within N division from the detection signal S1 of the first wavelength λ1 obtained by the first detection head 20A. And an interpolation processing circuit 311A that generates and outputs a first position signal POS1 having a minimum resolution unit λ1 / N.

  The second signal processing unit 31B performs the first trigger signal once per one wavelength of the second wavelength λ2 from the detection signal S2 of the second wavelength λ2 obtained by the second detection head 20B. For each first trigger signal TG1 output from the first trigger signal generation unit 311B that generates and outputs TG1, and for each first trigger signal TG1 output from the first trigger signal generation unit 311B, the second resolution λ2 is set to the minimum resolution unit. It comprises a first counter 312B that generates and outputs the second position signal POS2 by cumulatively adding the number K divided by the wavelength of λ1 / N as an added value.

  In the second signal processing unit 31B, the detection signal of the second wavelength λ2 obtained by the second detection head 20B is obtained by accumulating the addition value K for each first trigger signal TG1. From S2, a second position signal POS2 expressing position information by a multiple of a number K obtained by dividing the second wavelength λ2 by the wavelength of the minimum resolution unit λ1 / N is generated.

  In addition, the third signal processing unit 31C performs one second trigger signal per one wavelength of the first wavelength λ1 from the detection signal S1 of the first wavelength λ1 obtained by the first detection head 20A. For each second trigger signal generation unit 311C that generates and outputs TG3, and for each second trigger signal TG2 output from the second trigger signal generation unit 311C, the addition value N is cumulatively added to the second trigger signal generation unit 311C. And a second counter 312C that generates and outputs a third position signal POS3.

  In the third signal processing unit 31C, for each second trigger signal TG2 output from the second trigger signal generation unit 311C, the second counter 312C causes the first counter 312A to perform the first operation. The third position signal POS3 by accumulatively adding the count value N per wavelength of the first wavelength λ1, that is, the divided interpolation number N of one wavelength of the first wavelength λ1 in the first signal processing unit 31A. Is generated.

  That is, in the third signal processing unit 31C, the first wavelength λ1 is converted into the wavelength of the minimum resolution unit λ1 / N from the detection signal S1 of the first wavelength λ1 obtained by the first detection head 20A. A third position signal POS3 expressing the position information by a multiple of the number N divided by is generated.

  Further, in the signal processing unit 30A, the position information comparison unit 32 includes a second position signal POS2 obtained by the second signal processing unit 31B and a third position obtained by the third signal processing unit 31C. The first comparison processing unit 321A to which the signal POS3 is supplied, the first position signal POS1 obtained by the first signal processing unit 31A, and the third position signal POS3 obtained by the third signal processing unit 31C. Is supplied with the second comparison processing unit 321B, the first position signal output unit 322A supplied with the first position signal POS1 obtained by the first signal processing unit 31A, and the second signal processing. And a second position signal output unit 322B to which a second position signal POS2 obtained by the unit 31B is supplied, and the second position signal obtained by the second signal processing unit 31B. When the POS2 and the third position signal POS3 obtained by the third signal processing unit 31C coincide with each other, the first position signal POS1 obtained by the first signal processing unit 31A is output as the first position signal. Output from the unit 322A.

  When the second position signal POS2 obtained by the second signal processing unit 31B and the third position signal POS3 obtained by the third signal processing unit 31C do not match, the first comparison processing unit 321A It is determined as an abnormal state, and an abnormality detection signal indicating an abnormal state is output to the first position signal output unit 322A, and the first position signal POS1 is output from the first position signal output unit 322A. To prevent.

  In the position detection device 100, the length measurement scales of the first and second scales 10A and 10B cannot be completely correctly created and are created with extremely small errors. Furthermore, there is an error factor on the detection heads 20A and 20B side that a complete measurement cannot be performed due to a change in posture at the time of measurement. In the abnormality detection in the position detection apparatus 100, whether or not they are matched within an assumed range that takes into account the change factors of the configuration of the measurement mechanism and the like in terms of manufacturing is compared. Further, in the case of different examples of the wavelengths λ1 and λ2, the trigger positions at the time of comparison are different between the two wavelengths λ1 and λ2, and therefore it is normal that the values are shifted depending on the measurement location. In this case, the range is also set and abnormality is detected. However, as described at the beginning, the setting is within a sufficiently small range from the level necessary for functional safety.

  The second comparison processing unit 321B determines that the first position signal POS1 obtained by the first signal processing unit 31A and the third position signal POS3 obtained by the third signal processing unit 31C do not match. It is determined as an abnormal state, and an abnormality detection signal indicating an abnormal state is output to the first position signal output unit 322A, and the first position signal POS1 is output from the first position signal output unit 322A. To prevent.

  The first position signal output unit 322A receives the first signal when each abnormality detection signal obtained by the first comparison processing unit 321A and the second comparison processing unit 321B does not indicate an abnormal state. The first position signal POS1 obtained from the processing unit 31A is output to the communication control unit 33. The second position signal output unit 322B outputs the second position signal POS2 obtained from the second signal processing unit 31B to the communication control unit 33.

  In this signal processing unit 30C, the binary representation of the position information of the first position signal POS1 obtained by the first signal processing unit 31A and the second position signal POS2 obtained by the second signal processing unit 31B. The binary representation of location information is unified. Further, the binary representation of the position information of the first position signal POS1 obtained by the first signal processor 31A and the binary representation of the position information of the third position signal POS3 obtained by the third signal processor 31C. Are unified. The position information comparing unit 32 includes the first position signal POS1 generated by the first signal processing unit 31A, the second position signal POS2 generated by the second signal processing unit 31B, and the third position signal. Based on the third position signal POS3 generated by the signal processing unit 31C, the error range required for functional safety is verified. Then, the first position signal POS1 that is precise position information and the second position signal POS2 that is redundant position information are sent to the external CNC controller 200 by serial communication via the communication control unit 33.

Here, as shown in the block diagram of FIG. 6 with specific processing contents in the signal processing unit 30C, in the position detecting device 100, different wavelengths λ1 for the first scale 10A and the second scale 10B. , Λ2 are recorded, for example, the first wavelength λ1 is 160 μm and the second wavelength λ2 is 80 μm, and the division interpolation number N in the first signal processing unit 30A is 16000, 16000. A division interpolation process is performed to generate a first position signal POS1 with a minimum resolution of λ1 / N = 160 μm / 16000 = 10 nm from the detection signal S1 of the first wavelength λ1 obtained by the first detection head 20A. If it is supposed to
In the signal processing unit 30C, the addition values N and K are set to N = 16000.
K = 8000
As described above, the second position signal POS2 is generated by the second signal processing unit 30B, and the third position signal POS3 is generated by the third signal processing unit 30C.

  That is, in the third signal processing unit 30C, for example, the second trigger signal TG2 is output once from the second trigger signal generation unit 311C for each wavelength of the first wavelength λ1, and the first trigger signal TG2 is output once. The added value N = 16000 is cumulatively added by the second counter 312C for each wavelength of the wavelength λ1 to generate the third position signal POS3, thereby generating the third signal processing unit 30C. The unit representation of the first position signal POS1 of the minimum resolution unit generated by the third position signal POS3 and the first signal processing unit 30C can be matched, and in the second comparison processing unit 40B, The count result for each minimum resolution unit of the first position signal POS obtained as the count result in the minimum resolution unit by the first signal processing unit 30A and the third signal processing. By comparing the cumulative addition result by the unit 30C with the obtained third position signal POS3, an abnormality detection signal can be generated and output.

  The second signal processing unit 30B outputs the first trigger signal TG1 once for each wavelength of the second wavelength λ2 from the first trigger signal generation unit 311B, and outputs the second wavelength. The third value processor 30C generates the second position signal POS2 by cumulatively adding the added value K = 8000 for each wavelength of λ2 by the first counter 312B to generate the second position signal POS2. The second position signal POS2 and the third signal processing unit obtained by the second signal processing unit 30B in the first comparison processing unit 40B. An abnormality detection signal can be generated and output by comparing the third position signal POS3 obtained from 30C.

  Here, the third signal processing unit 30C outputs a second trigger signal twice for each wavelength of the first wavelength λ1 from the second signal generation unit 311C, with a multiple of 2. Even if the third position signal POS3 is generated by accumulating and adding the natural number 8000 by the second counter 312C for every half wavelength of the first wavelength λ1, the third signal processing unit 30C may generate the third position signal POS3. The unit representation of the generated third position signal POS3 and the first position signal POS1 of the minimum resolution unit generated by the first signal processing unit 30C can be matched, and the first detection head For the detection signal of the first wavelength λ1 obtained by 20A, a multiple of the minimum resolution unit is set for each wavelength obtained by dividing the first wavelength λ1 by a natural number so as to be a multiple of the minimum resolution unit. By generating the third position signal POS3 by performing product addition, the third position signal POS3 generated by the third signal processing unit 30C and the first signal processing unit 30C are generated. The unit representation of the first position signal POS1 in the minimum resolution unit is matched, and in the second comparison processing unit 40B, every minimum resolution unit of the first position signal POS by the first signal processing unit 30A. And the cumulative addition result of the third position signal POS3 obtained from the third signal processing unit 30C can be compared.

  That is, in the third signal processing unit 30C, in the position information comparison unit 40, the first position signal POS1, the second position signal POS2, and the third position signal POS3 are within an error range required for functional safety. When comparing the position signals POS1, POS2, and POS3 to verify the existence, the numerical unit of the first position signal POS1 that comes from the minimum resolution used for the original device control, and for functional safety In order to unify the units of the second position signal POS2 and the third position signal POS3 expressed by the count value of the length measurement scale, the wavelengths λ1 and λ2 themselves are counted and the second position signal POS2 and the third position signal POS2 are counted. Instead of generating the position signal POS3, the wavelength of the length measurement scale is set to a multiple K (= N × λ2 / λ1) and a multiple N (= N ×) of the first resolution of the first position signal POS1. N × λ1 / λ1), and each time a length measurement scale is detected, the position information of the second position signal POS2 and the third position signal POS3 is obtained by cumulatively adding or subtracting the multiple K or multiple N. By performing the processing, as shown in FIG. 7, the unit expressions of the first position signal POS1, the second position signal POS2, and the third position signal POS3 can be unified, and the position for determining the subsequent normal operation. Information comparison can be easily performed with a simple circuit, and functional safety can be ensured.

  As the length measuring method in the position detecting device 100, various methods such as optical / magnetic / guide / laser known in the art can be employed. The present invention can be applied to any length measurement system having a length measurement scale and interpolation processing regardless of the length measurement method. Further, in the description of the examples in the embodiment of the present invention, the description has been given using the configuration that prevents the first position signal POS1 and the second position signal POS2 from being output when an abnormality is detected. The present invention is not limited to the above-described embodiments, such as outputting an abnormality detection to the subsequent CNC controller 200 by other methods such as outputting an alarm signal separately without preventing the output of the signal. And may be determined according to communication specifications with the CNC controller. Further, the number of tracks on which the length measurement scale is recorded, that is, the number of scales provided in the scale unit 10 and the number of heads that detect the length measurement scale, that is, the number of detection heads provided in the head unit 20 are not limited. It may be determined according to the functional safety requirement specification.

  Furthermore, regarding the generation of the trigger signal, it is possible not only to generate the trigger signal once per wavelength, but also to generate a large number of triggers / wavelengths by the length measurement circuit configuration.

  For example, the third signal processing unit 30C sets the first signal so that the detection signal S1 of the first wavelength λ1 obtained by the first detection head 10A is a multiple of the minimum resolution unit λ1 / N. In the second comparison processing unit 30B, the third position signal POS3 is generated by cumulatively adding the natural number n to each wavelength λ1 / n obtained by dividing one wavelength of the wavelength λ1 by the natural number n. The count result for each minimum resolution unit of the first position signal POS1 by the first signal processing unit 30A is compared with the cumulative addition result of the third position signal POS3 obtained from the third signal processing unit 30C. be able to.

  Further, when there are a plurality of measurement scales, the wavelengths do not have to be the same, and may be a multiple of the minimum resolution unit of the first position signal POS1. What is necessary is just to add / subtract the multiple. When the multiple to be added or subtracted has the greatest common divisor of M to the power, the lower M bit of the addition / subtraction value and the lower M bit of the accumulation counter are always 0, so the addition / subtraction value and the lower N bit of the accumulation counter are May be omitted. That is, the first wavelength λ1 is a wavelength that is an integer N times the wavelength λ0 of the minimum resolution, the second wavelength λ2 is a wavelength that is an integer M times the wavelength λ0 of the minimum resolution, and N / By setting M to a power of 2, the unit expressions of the first position signal POS1, the second position signal POS2, and the third position signal POS3 can be unified and compared by a simple process. Accordingly, the first position signal POS1 and the second position signal expressed in binary as binary position information from the first signal processing unit 30A, the second signal processing unit 30B, and the third signal processing unit 30C, respectively. The POS2 and the third position signal POS3 are output, and the position information comparison unit 32 performs a predetermined comparison from the highest position of the first position signal POS1 expressed as the binary position information by the second comparison processing unit 321B. A numerical value obtained by extracting only the number of digits is compared with the third position signal POS3 expressed as the binary position information, and an abnormality detection signal can be output in the case of mismatch.

  Further, the resolution of the second position signal POS2 sent from the communication control unit 33 to the CNC controller 200 does not have to be the same as that of the first position signal POS1, and as long as ± 1 bit can be accepted as a quantization error, The lower bits of the second position signal POS2 may be omitted according to the communication load and the functional safety requirement specification.

  DESCRIPTION OF SYMBOLS 10 Scale part, 10A 1st scale, 10B 2nd scale, 20 head part, 20A 1st detection head, 20B 2nd detection head, 30, 30A, 30B, 30C Signal processing part, 31A 1st signal Processing unit, 31B second signal processing unit, 31C third signal processing unit, 32 position information comparison unit, 33 communication control unit, 100 position detection device, 200 CNC controller, 311A interpolation processing circuit, 311B first trigger Signal generation unit, 311C second trigger signal generation unit, 312B first counter, 312C second counter, 321A first comparison processing unit, 321B second comparison processing unit, 322A first position signal output unit, 322B Second position signal output unit, 313 multiplier

Claims (5)

The first of the minimum resolution units obtained by interpolating one wavelength of the first wavelength from the detection signal of the first wavelength obtained by reading the first length measurement scale from the first scale by the first detection head. A first signal processing unit that generates and outputs a position signal of
A second signal processing unit that generates and outputs a second position signal from the detection signal of the second wavelength obtained by reading the second length measurement scale from the second scale by the second detection head;
A third signal processing unit that generates and outputs a third position signal from the detection signal of the first wavelength obtained by the first detection head;
A first comparison processing unit that compares the second position signal obtained from the second signal processing unit and the third position signal obtained from the third signal processing unit;
A position detection device that detects an abnormality based on a comparison result by the first comparison processing unit. A second comparison processing unit that compares the first position signal obtained from the first signal processing unit and the third position signal obtained from the third signal processing unit;
2. The position detection apparatus according to claim 1, wherein an abnormality is detected based on both comparison results by the first comparison processing unit and the second comparison processing unit. The second signal processing unit accumulates a first count value for each unit length obtained by dividing the second wavelength by a natural number for the detection signal of the second wavelength obtained by the second detection head. The second position signal is generated by adding,
The third signal processing unit accumulates a second count value for each unit length obtained by dividing the first wavelength by a natural number with respect to the detection signal of the first wavelength obtained by the first detection head. The third position signal is generated by adding,
The length obtained by dividing the unit length corresponding to the first count value by the first count value and the unit length corresponding to the second count value are divided by the second count value. The position detection apparatus according to claim 1, wherein the obtained length is the same. The third signal processing unit cumulatively adds a second count value for each length obtained by dividing the first wavelength by a natural number for the detection signal of the first wavelength obtained by the first detection head. To generate the third position signal,
In the second comparison processing unit, a cumulative addition of the count result for each minimum resolution unit of the first position signal by the first signal processing unit and the third position signal obtained from the third signal processing unit. Compare the results with
3. The position according to claim 2, wherein a length obtained by dividing a unit length corresponding to the second count value by the second count value is the same as an integral multiple of the minimum resolution. Detection device. Each signal processing unit outputs a position signal expressed as binary position information,
5. The comparison unit according to claim 3, wherein the comparison unit compares the position signal with a numerical value obtained by extracting only a predetermined number of digits from the most significant position signal represented as the binary position information. The position detecting device according to claim 1.