Position detection device

Abstract

The present disclosure relates to a position detection device. The position detection device comprises: a detector that outputs a count value corresponding to the position of a detection object, the count value repeating values ​​from zero to an upper limit value; an extended data storage unit that stores extended data, the extended data corresponding to the cumulative value of the change in the count value caused by the flip; a position calculation unit that calculates the absolute position of the detection object by adding the count value output by the detector to the cumulative value represented by the extended data; a partition storage unit that stores a count partition including the count value received from the detector among three or more count partitions that are demarcated to distinguish the range of the count value; and a confirmation processing unit that confirms whether the extended data is appropriate based on the number of divisions between the count partition stored in the partition storage unit and the count partition including the count value after the start of the position detection processing when the position detection processing starts.

Description

Technical Field

[0001] The invention relates to a position detection device. Background Art

[0002] Among the position detection devices for controlling industrial machinery such as machine tools and industrial robots, there is a position detection device that uses a detector that outputs a count value corresponding to the position of the detection object to detect the absolute position of the detection object, and controls the industrial machinery based on the detected absolute position of the detection object. (For example, refer to Patent Document 1). This detector that outputs a count value is called an absolute position detector because it determines the absolute position of the detection object. The position that the absolute position detector can detect, that is, the count value, has an upper limit value.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2000-99156 Summary of the invention

[0006] Problem that the invention aims to solve

[0007] In the control device described in Patent Document 1, the detector for detecting the position has a counter for counting the number of revolutions and a counter for counting the rotational position within one revolution. In addition, the control device of Patent Document 1 has a reference data storage unit for storing the output value (number of revolutions data) of the detector corresponding to the origin position of the absolute position, and calculates the absolute position (for example, the mechanical coordinate) by the difference between the output value at the current position of the detector and the output value at the origin position.

[0008] Although it varies depending on the type of detector, there is an upper limit value (data length) for the count value of the number of revolutions of the detector. In many absolute position detectors, the count value returns to zero when it exceeds the upper limit value. In other words, the count value of a general absolute position detector repeats values ​​from zero to the upper limit value. Therefore, a technology is desired that can detect the absolute position based on the count value output from the detector even when the detection object moves to a large range exceeding the upper limit value of the detector.

[0009] Solutions for solving problems

[0010] A position detection device according to one embodiment of the present disclosure comprises: a detector which outputs a count value corresponding to the position of a detection object, the count value repeating values ​​from zero to an upper limit value; an extended data storage unit which stores extended data, the extended data being equivalent to a cumulative value of a change in the count value caused by a flip in which the count value switches between zero and the upper limit value; a position calculation unit which calculates the absolute position of the detection object by adding the count value output by the detector to the cumulative value represented by the extended data; a partition storage unit which stores a count partition including the count value received from the detector among three or more count partitions defined to distinguish the range of the count value; and a confirmation processing unit which confirms whether the extended data is appropriate based on the number of partitions between the count partition stored in the partition storage unit and the count partition including the count value after the start of the position detection processing when the position detection processing starts.

[0011] Effects of the Invention

[0012] According to the present disclosure, even when the detection object moves to a wide range exceeding the upper limit value of the detector, the absolute position can be detected based on the count value output from the detector. Even when the detection processing is stopped and the detection object moves to a position beyond the detection range of the detector, the accurate absolute position can be detected. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a block diagram showing the structure of a position detection device according to one embodiment of the present disclosure.

[0014] Figure 2 It is shown Figure 1 A diagram showing the relationship between the count value of a detector of a position detection device and the absolute position.

[0015] Figure 3 It is shown Figure 1 Flow chart of the absolute position detection process in the position detection device.

[0016] Description of Reference Numerals

[0017] 1: Position detection device; 2: Detector; 3: Origin data storage unit; 4: Extended data storage unit; 5: Position calculation unit; 6: Partition storage unit; 7: Confirmation processing unit; 71: Confirmation unit; 72: Correction unit; 73: Notification unit; T: Detection object. DETAILED DESCRIPTION

[0018] Hereinafter, the position detection device according to the present disclosure will be described with reference to the drawings. Figure 11 is a block diagram showing the structure of a position detection device 1 according to an embodiment of the present disclosure. The position detection device 1 detects the absolute position of a linearly driven detection object T. The detection object T can be, for example, a table driven by a feed screw in a machine tool.

[0019] The position detection device 1 includes a detector 2, an origin data storage unit 3, an extended data storage unit 4, a position calculation unit 5, a partition storage unit 6, and a confirmation processing unit 7. In the position detection device 1, the origin data storage unit 3, the extended data storage unit 4, and the partition storage unit 6 are composed of a non-volatile memory that can retain information even when the detection operation of the position detection device 1 is stopped. The origin data storage unit 3, the extended data storage unit 4, and the partition storage unit 6 can be composed of the same memory. In addition, the position calculation unit 5 and the confirmation processing unit 7 can be realized by, for example, making a computing device such as a CPU execute an appropriate program, and can be clearly distinguished in terms of physical structure and program structure. In addition, the origin data storage unit 3, the extended data storage unit 4, the position calculation unit 5, the partition storage unit 6, and the confirmation processing unit 7 can be, for example, a part of a numerical control device that controls a machine tool, a robot control device that controls a robot, etc.

[0020] The detector 2 outputs a count value corresponding to the position of the detection object T, and the count value repeats values ​​from zero to the upper limit value. The detector 2 can be configured to output a rotation count value that increases by 1 or decreases by 1 (increases by 1 when rotating in the positive direction, and decreases by 1 when rotating in the negative direction) for each rotation of the driving shaft driving the detection object T, and outputs the angle data within one rotation of the driving shaft as the count value. As a specific example, the detector 2 can be set to a known absolute encoder, which is configured to detect the rotation amount of a driving shaft that drives a ball screw or the like that drives the detection object T, and the driving shaft is, for example, an output shaft of a motor, a rotating shaft of a transmission mechanism that transmits the rotation of the motor to the ball screw or the like, etc.

[0021] The revolution count value output by the detector 2 is a non-negative integer, and a rollover to zero occurs when the specified upper limit value is reached. In addition, regarding the revolution count value, when the detection object T moves further in the negative direction from the position where the revolution count value is zero, the revolution count value is converted from zero to the upper limit value. In addition, the angle data output by the detector 2 is also a non-negative integer, and a rollover occurs between zero and the maximum value every time the drive shaft rotates one circle. The revolution count value increases or decreases when the angle data is rolled over.

[0022] As the upper limit value of the rotation count value of the detector 2, for example, 4095 (12-bit data), 65535 (16-bit data), etc. are assumed. The movement amount of the detection object T per one rotation of the drive shaft is generally about 1 mm to 10 mm, so it is considered that when the rotation count value of the detector 2 increases from zero to the upper limit value, the detection object T moves several meters to several hundred meters.

[0023] The origin data storage unit 3 stores the rotation count value and angle data output by the detector 2 when the detection object T is arranged at the origin determined for convenience as origin data. Thus, the position calculation unit 5 described later can calculate the absolute position of the detection object T based on the origin.

[0024] The extended data storage unit 4 stores extended data, which is equivalent to the cumulative value of the change in the number of revolutions counted value caused by the reversal when the number of revolutions counted value received from the detector 2 is reversed. The extended data can be set to the following count value: "1" is added when the number of revolutions counted value is reversed in the positive direction from the upper limit value to zero, and "-1" is added when the number of revolutions counted value is reversed in the negative direction from zero to the upper limit value. It can also be set to a value obtained by accumulating the change in the number of revolutions counted value caused by the reversal (preferably, the decrease is set to a positive value).

[0025] The position calculation unit 5 calculates the absolute position of the detection object T by adding the rotation count value and the angle data received from the detector 2 to the cumulative value of the change in the rotation count value due to the flip represented by the extended data stored in the extended data storage unit 4. In addition, the position calculation unit 5 may convert the absolute position of the detection object T into a position in a coordinate system used for controlling the detection object T by a machine tool or the like by subtracting the value of the origin data stored in the origin data storage unit 3.

[0026] The partition storage unit 6 stores counting partitions including the revolution count values ​​received from the detector 2, among the three or more counting partitions demarcated by distinguishing the range of the revolution count values ​​(from zero to the upper limit value). From the viewpoint of reducing the amount of data, reducing the computational load, and improving the judgment accuracy of the confirmation processing unit 7, it is preferred to divide the range of the revolution count values ​​into N equal parts to set the counting partitions. The number N of counting partitions needs to be set to 3 or more in order to correct the extended data, and is preferably set to 4 or more in order to detect abnormal movement of the detection object T. In addition, from the viewpoint of reducing the amount of data, it is preferred that the number N of counting partitions is small. Therefore, it is preferred to set the number N of counting partitions to 3 or 4.

[0027] The confirmation processing unit 7 confirms whether the extended data stored in the extended data storage unit 4 is appropriate based on the number of divisions between the count divisions stored by the division storage unit 6 before the start of the position detection process and the count divisions containing the rotation count values ​​received from the detector 2 after the start of the position detection process when the position detection process of the position detection device 1 starts. The confirmation processing unit 7 can be configured to include: a confirmation unit 71 that calculates the number of divisions; a correction unit 72 that corrects the extended data to an appropriate value based on the number of divisions; and a notification unit 73 that notifies when the value of the extended data is considered to be inappropriate.

[0028] In the detector 2, when the detection object T is moved beyond the position where the rotation count value is reversed during the period when the position detection device 1 stops the position detection processing, the extended data stored in the extended data storage unit 4 becomes an inaccurate value. In this case, after the position detection processing of the position detection device 1 starts, the position calculation unit 5 cannot accurately calculate the absolute position of the detection object T. Therefore, the confirmation processing unit 7 determines whether the extended data stored in the extended data storage unit 4 is appropriate when the position detection device 1 starts the position detection processing.

[0029] Figure 2 The relationship between the count value of the detector 2 and the absolute position of the detection object T is shown. Figure 2 This is an example of dividing the range of the revolution count value into four counting partitions based on the origin position P0. The counting partitions from the origin position to the positive direction are set to Ra1, Ra2...Rai (i is a positive integer), and the counting partitions from the origin position to the positive direction are set to Rb1, Rb2...Rbj (j is a positive integer). In the example shown in the figure, since the division is based on the origin position, the counting partitions Rb6, Rb2, Ra3, and Ra7 are defined as the area spanning the upper limit value of the revolution count value and the area containing zero.

[0030] exist Figure 2 In the figure, Pr is used to illustrate the absolute position of the detection object T before the position detection device 1 stops the detection process, and Pp is used to illustrate the absolute position of the detection object T when the position detection device 1 starts the position detection process. In the example shown in the figure, the following situation is shown: the revolution count value of the absolute position Pr before the detection process stops is a value close to its upper limit, and the detection object T is moved beyond the flip position during the detection process stop. In this case, the actual absolute position after the position detection process starts is Pp, but since the extended data of the extended data storage unit 4 is not updated during the detection process stop, if the position calculation unit 5 calculates the absolute position according to the original data, it is judged that the detection object T exists at the absolute position Pq.

[0031] The confirmation unit 71 determines the counting partition to which the revolution count value before the detection process stops (Ra2 in the example shown in the figure) belongs, and sets it as the reference partition. In addition, the correction unit 72 determines the counting partition to which the absolute position Pq represented by the revolution count value received after the start of the position detection control belongs (Rb2 in the example shown in the figure), and sets it as the first partition. Furthermore, the confirmation unit 71 sets the counting partition of the Nth partition in the positive direction from the first partition (Ra3 in the example shown in the figure) as the second partition, and sets the counting partition of the Nth partition in the negative direction from the first partition (Rb6 in the example shown in the figure) as the third partition. Then, the confirmation unit 71 calculates the number of partitions from the reference partition to the first partition, the second partition, and the third partition, that is, the first partition, the second partition, and the third partition are the number of counting partitions from the reference partition (the number of partitions in the example shown in the figure is 3, 1, and 7, respectively).

[0032] As described above, the range of the revolution count value is equivalent to several meters to hundreds of meters when converted into the moving distance of the detection object T, so it is difficult to imagine that the detection object T moves across many counting partitions during the detection process is stopped. Therefore, it is highly likely that the partition with the smallest number of partitions among the first partition, the second partition, and the third partition is the counting partition where the detection object T actually exists. Therefore, when the number of partitions of the second partition or the third partition is smaller than the number of partitions of the first partition, it can be determined that the value of the extended data stored in the extended data storage unit 4 is inappropriate.

[0033] The confirmation unit 71 calculates the number of divisions between the reference partition and the first partition, the second partition, and the third partition as described above. The number of divisions is a relative value and is not affected by the number of flips before the detection process stops. Therefore, the confirmation unit 71 may determine the reference partition, the first partition, the second partition, and the third partition as if no flip occurred before the detection process stops without confirming the extended data stored in the extended data storage unit 4 at the start of the position detection control. Thus, the confirmation unit 71 can confirm whether the extended data stored in the extended data storage unit 4 at the start of the position detection control is appropriate through a relatively simple calculation.

[0034] The correction unit 72 determines the counting partition with the smallest number of separations with the reference partition among the first partition, the second partition and the third partition (the second partition R2b in the illustrated example) as the counting partition corresponding to the actual absolute position of the detection object T, and corrects the extended data stored in the extended data storage unit 4 to make the counting partition of the absolute position calculated by the position calculation unit 5 consistent with it.

[0035] When the number of divisions exceeds a predetermined threshold, the notification unit 73 notifies that the appropriateness of the extended data is likely to be inappropriate. As described above, it is difficult to imagine that the detection object T moves significantly during the detection process stop period, so when the number of divisions exceeds the threshold, it can be considered that the detection object T is artificially moved significantly due to some abnormality or special circumstances, so by notifying this meaning, the operator can be urged to confirm or confirm afterwards.

[0036] The threshold of the number of partitions set in the notification unit 73 needs to be set to 1 or more to set a counting partition for judging the extended data as appropriate, and needs to be set to (N / 2-1) or less to set a value smaller than the maximum value of the number of partitions, i.e., N / 2.

[0037] Figure 3 The process of position detection processing in the position detection device 1 is shown. The position detection processing includes the following steps: first, confirm whether the count partition data is stored in the partition storage unit 6 (step S1: count partition data confirmation step); the absolute position of the detection object is calculated by the position calculation unit 5 (step S2: absolute position calculation step); confirm whether the count partition data stored in the partition storage unit 6 is consistent with the count partition to which the rotation count value received from the detector 2 belongs (step S3: count partition confirmation step); calculate the number of divisions of the first partition, the second partition, and the third partition (step S4: division number calculation step); compare the minimum value of the number of divisions of the first partition, the second partition, and the third partition with the threshold value (step S5: threshold comparison step); notify the meaning of abnormal movement of the detection object during the control stop period (step S6: notification step); confirm whether the number of divisions of the first partition is the smallest (step S7: first partition confirmation step); and correct the extended data (step S8: extended data correction step).

[0038] (Counting partition data confirmation process)

[0039] In the counting partition data confirmation process of step S1, it is confirmed whether the counting partition data is stored in the partition storage unit 6. If the counting partition data is not stored in the partition storage unit 6, since there is no information to be considered, the process directly proceeds to step S2. If the counting partition data is stored in the partition storage unit 6, the process proceeds to step S3.

[0040] (Absolute position calculation process)

[0041] In the absolute position calculation process of step S2 , the position calculation unit 5 calculates the absolute position of the detection object T based on the rotation count value and angle data received from the detector 2 , the extended data stored in the extended data storage unit 4 , and the origin data stored in the origin data storage unit 3 .

[0042] (Counting and partitioning confirmation process)

[0043] In the counting partition confirmation process of step S3, it is confirmed whether the counting partition data of the partition storage unit 6 is consistent with the counting partition to which the current number of revolutions count value belongs. If the counting partition data of the partition storage unit 6 is consistent with the counting partition to which the current number of revolutions count value belongs, it is considered that the detection object T has not been moved significantly during the control stop period, so no special processing is performed, and the absolute position of the detection object T is calculated in step S2. On the other hand, if the counting partition data of the partition storage unit 6 is different from the counting partition to which the current number of revolutions count value belongs, it is considered that the detection object T has been intentionally moved during the control stop period, so the processing after step S4 is performed.

[0044] (Partition number calculation process)

[0045] In the partition number calculation process of step S4, the confirmation unit 71 determines the reference partition (the counting partition stored in the partition storage unit 6), the first partition (the counting partition to which the current number of revolutions count value belongs), the second partition (the Nth counting partition in the positive direction from the first partition), and the third partition (the Nth counting partition in the negative direction from the first partition), and calculates the partition numbers between the first partition, the second partition, and the third partition and the reference partition, respectively.

[0046] (Threshold comparison process)

[0047] In the threshold comparison process of step S5, the minimum value of the number of divisions of the first sub-area, the second sub-area, and the third sub-area is compared with a preset threshold value. When the minimum value of the number of divisions is greater than the threshold value, it is determined that the amount of movement of the detection object T during the control stop period is abnormal, and the process of step S6 is performed. On the other hand, when the minimum value of the number of divisions is less than the threshold value, it is determined that the amount of movement of the detection object T during the control stop period is within the range that may normally occur, and the process proceeds to step S7.

[0048] (Notification process)

[0049] In the reporting process of step S6, the notification unit 73 outputs a notification signal indicating that the movement of the detection object during the control stop period is abnormal. The position detection device 1 may include a notification device that receives the notification signal output by the notification unit 73 and notifies the operator through visual information or auditory information. As such a notification device, a buzzer that emits mechanical sound, an alarm sound, a speaker that emits a voice message, a display lamp that notifies by emitting light, a display that displays a warning on a screen, etc. can be used.

[0050] In the present embodiment, the process proceeds to step S7 after the notification signal is output in the notification step. However, the process may be terminated when the notification signal is output.

[0051] (First zone confirmation process)

[0052] In the first partition confirmation process of step S7, the size relationship of the number of partitions of the first partition, the second partition, and the third partition is confirmed. When the number of partitions of the first partition is the smallest, it is considered that there is no error in the extended data stored in the extended data storage unit 4, so the process directly proceeds to step S2 to calculate the absolute position of the detection object T. On the other hand, when the number of partitions of the second partition or the third partition is smaller than the number of partitions of the first partition, the process proceeds to step 8.

[0053] (Extended Data Correction Process)

[0054] In the extended data correction process of step S8, it is considered that the revolution count value has reversed in the direction corresponding to the partition with a smaller number of divisions among the second and third partitions during the control stop period, so the following correction is performed: the value of the extended data stored in the extended data storage unit is added with the change amount when the value is reversed once in the direction corresponding to the partition with a smaller number of divisions among the second and third partitions. After the extended data is corrected, the process proceeds to step S2, and the absolute position of the detection object is calculated using the corrected extended data.

[0055] As described above, the position detection device 1 has an extended data storage unit 4 for storing extended data, and the extended data is equivalent to a value obtained by accumulating the change in the number of revolutions count value caused by the reversal. Therefore, the absolute position of the detection object T can be detected based on the number of revolutions count value output from the detector 2 within a wide range exceeding the upper limit value of the detector 2.

[0056] In addition, the position detection device 1 includes a partition storage unit 6 and a confirmation processing unit 7 having a correction unit 72, so that even when the detection object T is moved beyond the position where the rotation count value is reversed during the stop of the position detection processing, the extended data can be corrected to an appropriate value, so that the absolute position of the detection object T can be accurately calculated. In particular, the partition storage unit 6 and the confirmation processing unit 7 confirm whether the extended data is appropriate based on a small number of count partitions that are demarcated by distinguishing the range of the rotation count value, so the amount of data to be processed can be small.

[0057] In addition, in the position detection device 1, the confirmation processing unit 7 has a notification unit 73 for notifying when the number of partitions of the counting partition is too large, so that it can notify or record the fact that the movement amount of the detection object T is large during the period when the position detection processing is stopped, thereby preventing failures in advance or performing verification afterwards.

[0058] The embodiments of the present disclosure are described above, but the present invention is not limited to the above embodiments. In addition, the effects described in the embodiments are only the best effects produced by the present invention, and the effects of the present invention are not limited to the effects described in the embodiments.

[0059] In the position detection device involved in the present disclosure, the extended data storage unit can also store the extended data as the cumulative value of the change in the revolution count value caused by the flip and the sum of the revolution count value output from the detector when the detection object is located at the origin. Thereby, the calculation of the absolute position of the detection object in the position calculation unit becomes easy.

[0060] In the position detection device involved in the present disclosure, the confirmation processing unit may not include a correction unit or a notification unit. In addition, the confirmation processing unit may not perform correction of the extended data by the correction unit when the number of divisions exceeds the threshold value and is notified by the notification unit. In this way, the extended data when the reception of the count value is interrupted can be preserved, so that the reason why the number of divisions increases can be easily determined.

Claims

1. A position detection device, comprising: a detector that outputs a count value corresponding to a position of a detection object, the count value repeating values ​​from zero to an upper limit value; An extended data storage unit storing extended data corresponding to a cumulative value of a change amount of the count value caused by a flip in which the count value switches between zero and the upper limit value; a position calculation unit that calculates the absolute position of the detection object by adding the count value output by the detector to the cumulative value represented by the extended data; a division storage unit for storing the count division including the count value received from the detector, among three or more count divisions defined by distinguishing the range of the count value; as well as a confirmation processing unit that, when the position detection processing starts, confirms whether the extended data is appropriate based on the number of partitions between the count partition stored in the partition storage unit and the count partition containing the count value after the position detection processing starts, Wherein, when either of the two second partition numbers is smaller than the first partition number, the confirmation processing unit confirms that the extended data is inappropriate, wherein the first partition number is the partition number between the counting partition stored in the partition storage unit and the counting partition containing the count value after the start of the position detection processing, and the two second partition numbers are the partition numbers between the counting partition stored in the partition storage unit and the Nth counting partition in the positive direction and the negative direction respectively from the counting partition containing the count value after the start of the position detection processing, and N is the number of the counting partitions.

2. The position detection device according to claim 1, characterized in that: The confirmation processing unit includes a correction unit that adds or subtracts a change amount of the count value per the rollover from the extended data so as to reduce the number of divisions.

3. The position detection device according to claim 1, wherein: The confirmation processing unit includes a notification unit configured to perform notification when the number of divisions exceeds a predetermined threshold value.

4. The position detection device according to any one of claims 1 to 3, wherein: Each time the driving shaft driving the detection object rotates one circle, the detector increases or decreases the count value by 1, and the detector outputs the angle data within one circle of rotation of the driving shaft. The position calculation unit further calculates the absolute position by adding the angle data.

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