JPH11112319A - Detection device and its threshold setting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform sampling in an optimum time only by the input of a teaching start and to set a threshold value by allowing the detection device to automatically detect the passage cycle of an object of detection and determining the time for sampling. SOLUTION: A measurement part 5 in a control part 4 drives a light projection part 2, decides the received light level from a photodetection part 3, and outputs a body detection signal. At the control part 4A, a data comparison part 7 compares a received light quantity as an initial value with an obtained received light quantity and a threshold setting process part 8 performs a threshold value setting process according to the comparison result. The maximum and minimum values of the received light level are updated during a sampling process and their data are held in a memory part 10. When a set cycle number is reached, a specific threshold value setting process is performed and, for example, the median between the maximum and minimum values in the sampling process is regarded as a threshold value. After this threshold value is set, an external output part 12 outputs a signal indicating teaching process completion to make an advance to a measuring process routine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a detecting device having a feature in setting a threshold value of a photoelectric sensor, a proximity sensor, or the like, and a method of setting the threshold value.

[0002]

2. Description of the Related Art Conventionally, when an object to be detected (hereinafter also referred to as a work) passing through a transport line or the like is detected using a photoelectric sensor, it is necessary to set a threshold value for the photoelectric sensor or the like. When setting the threshold value, a method of sampling the light reception level in a state where the work is arranged at a predetermined position, sampling the light reception amount in a background state after removing the work, and setting the threshold value based on each light reception amount ( Two-point teaching). Further, a method of setting a threshold value only in a state where a work is arranged at a predetermined position (one-point teaching) is also used.

[0003] As a method for teaching without such manual intervention, auto-teaching is used. When a work is sequentially conveyed on a conveyance line or the like, a teaching signal is input to the photoelectric sensor for a certain period of time as shown in FIG. In this method, while the teaching signal is being input, the photoelectric sensor performs sampling at regular intervals, and sets a threshold based on the maximum and minimum values of the amount of received light during this period.

[0004]

However, according to such a conventional teaching method, when performing one-point teaching or two-point teaching, the user stops the transport line in order to sample the amount of received light. Then, it is necessary to arrange a work at a predetermined position, and to perform teaching as a background state without arranging the work. In the case of auto teaching, it is not necessary to stop the transport line, but the user must recognize the input time and timing of the optimum teaching signal and control the teaching input. Since no output is obtained from the photoelectric sensor during sampling, the work during this time is wasted. Further, there is a drawback that a teaching input is required for a certain period of time, and a large amount of work is wasted when the conveying line is at a high speed.

The present invention has been made in view of such a conventional problem. When setting a threshold value of an object to be detected passing through a transport line, teaching is started without stopping the transport line. It is an object of the present invention to be able to automatically set a threshold just by inputting.

[0006]

According to a first aspect of the present invention, there is provided a detection unit for outputting a detection signal according to an external physical state, and a detection obtained by the detection unit when a teaching start signal is input. An initial value acquisition unit having a predetermined range including a signal level as an initial range, and after the detection signal changes from the initial range, a detection signal within the initial range is obtained again, and when the detection signal changes without crossing the initial range, And after the detection signal changes from the initial range, the detection signal within the initial range is obtained again, and after changing across the initial range, one of the cases where the detection signal within the initial range is obtained three times is detected. A data comparing unit that determines one cycle of the passage of the target; and a threshold setting process that sets a threshold based on the maximum value and the minimum value obtained when the detection target of at least one cycle detected by the data comparing unit passes. Parts and is characterized in that it has a, a measuring unit for discriminating the output obtained from said detecting unit on the basis of the threshold set by the threshold setting section.

According to a second aspect of the present invention, there is provided a threshold value setting method in a detection apparatus for detecting detection targets sequentially passing by comparing a detection signal corresponding to an external physical state with a threshold value and outputting a detection result signal. A predetermined range including the level of the detection signal obtained when the teaching start signal is input is set as the initial range, and after the detection signal changes from the initial range, a detection signal within the initial range is obtained again. When the detection signal changes without crossing the initial range, and after the detection signal changes from the initial range, a detection signal within the initial range is obtained again.After the detection signal changes across the initial range, the detection signal within the initial range is repeated three times. Is determined as one cycle of the passage of the detection target, and the maximum value and the minimum value of the detection signal obtained during the passage of the detection target of at least one cycle are determined. It is characterized in that the threshold value is set Zui.

According to a third aspect of the present invention, there is provided a detection unit for outputting a detection signal according to an external physical state, and a predetermined signal including a level of the detection signal obtained from the detection unit when a teaching start signal is input. An initial value acquisition unit that sets the range as the initial range, and after the detection signal changes from the initial range, a detection signal within the initial range is obtained again, and after changing across the initial range, the detection signal within the initial range is repeated three times. A data comparing unit that determines a case in which is obtained as one cycle of passage of the detection target;
A threshold setting processing unit that sets a threshold based on a maximum value and a minimum value obtained when the detection target of at least one cycle detected by the data comparison unit passes, based on the threshold set by the threshold setting processing unit A measuring unit for discriminating an output obtained from the detecting unit.

According to a fourth aspect of the present invention, there is provided a threshold value setting method in a detection apparatus for detecting detection targets sequentially passing by comparing a detection signal corresponding to an external physical state with a threshold value and outputting a detection result signal. A predetermined range including the level of the detection signal obtained when the teaching start signal is input is set as the initial range, and after the detection signal changes from the initial range, a detection signal within the initial range is obtained again, After changing across the initial range, a case where a detection signal within the initial range is obtained three times is determined as one cycle of passage of the detection target, and the detection signal obtained during at least one cycle of passage of the detection target is determined. The threshold value is set based on the maximum value and the minimum value of.

According to a fifth aspect of the present invention, there is provided a detecting unit for outputting a detecting signal corresponding to an external physical state, and a predetermined signal including a level of the detecting signal obtained from the detecting unit when a teaching start signal is input. An initial value acquisition unit that sets the range as an initial range, and a detection signal within the initial range is obtained again after the detection signal changes from the initial range, and a change in the detection target when the detection signal changes without crossing the initial range. A data comparison unit that determines a cycle, a threshold setting processing unit that sets a threshold based on the maximum value and the minimum value obtained when the detection target of at least one cycle detected by the data comparison unit passes,
A measurement unit that discriminates an output obtained from the detection unit based on a threshold value set by the threshold value setting processing unit.

According to a sixth aspect of the present invention, there is provided a threshold value setting method in a detection apparatus for detecting a detection target sequentially passing by comparing a detection signal according to an external physical state with a threshold value and outputting a detection result signal. A predetermined range including the level of the detection signal obtained when the teaching start signal is input is set as the initial range, and after the detection signal changes from the initial range, a detection signal within the initial range is obtained again. Determining that a change has occurred without crossing the initial range as one cycle of passage of the detection target, and setting a threshold based on the maximum value and the minimum value of the detection signal obtained during at least one cycle of passage of the detection target. It is characterized by doing.

According to a seventh aspect of the present invention, there is provided a detecting section for outputting a detection signal corresponding to an external physical state at predetermined intervals, and a detecting section for outputting a detecting signal when the teaching start signal is inputted. A difference value calculation unit for calculating a difference value between the detection signals, and when the absolute value of the difference value obtained from the difference value calculation unit is within a predetermined range, the detection signal is held, and the absolute value of the difference value is calculated. And a threshold value is set based on a detection signal held while at least one cycle of the passage of the detection target is determined by the cycle determination unit. A threshold setting processing unit; and a measuring unit that discriminates an output obtained from the detection unit based on the threshold set by the threshold setting processing unit.

The invention according to claim 8 of the present application is directed to a threshold setting method in a detection device for detecting a detection target sequentially passing by comparing a detection signal according to an external physical state with a threshold and outputting a detection result signal. Thereupon, sampling is performed every predetermined period after the teaching start signal is input, and a difference value between the detection signals obtained at each sampling is calculated, and when the absolute value of the difference value is within a predetermined range, Holding the data of the detection signal, determining one cycle of the passage of the detection target based on a change state of the absolute value of the difference value, and determining a threshold based on the detection signal held during at least one cycle of the passage of the detection target. Is set.

According to a ninth aspect of the present invention, there is provided a detection unit for outputting a detection signal according to an external physical state, and a detection signal for each detection signal obtained from the detection unit when a teaching start signal is input. A differential value calculator for calculating a differential value,
A cycle determination unit that holds the data of the detection signal when the absolute value of the level of the differential value is within a predetermined range, and that determines one cycle of passing the detection target based on a state of a change in the absolute value of the differential value; A threshold setting unit configured to set a threshold based on a detection signal held during at least one cycle of passage of a detection target by the cycle determination unit; and a detection unit configured to set the threshold based on a threshold set by the threshold setting unit. A measuring unit that discriminates the output obtained from the
It is characterized by having.

According to a tenth aspect of the present invention, there is provided a threshold value setting method for a detection apparatus for detecting detection targets sequentially passing by comparing a detection signal according to an external physical state with a threshold value and outputting a detection result signal. A sampling is performed intermittently when a teaching start signal is input, a differential value is calculated for each detection signal obtained for each sampling, and the absolute value of the differential value is within a predetermined range. Holding the data of the detection signal, determining one cycle of the detection target passage according to the state of the change of the absolute value of the differential value, and setting a threshold based on the detection signal held during at least one cycle of the detection target passage. It is characterized by setting.

[0016] The invention according to claim 11 of the present application is a detecting section for outputting a detection signal according to an external physical state at predetermined intervals,
A maximum value determining unit that determines the maximum value of the detection signal obtained from the detection unit when the teaching start signal is input, and the minimum value of the detection signal obtained from the detection unit when the teaching start signal is input. A minimum value determining unit for determining, and determining whether a detection signal obtained from the detection unit continuously updates a maximum value and a minimum value. If the detection signal is not continuously updated a predetermined number of times, one cycle of passing the detection target is determined. A cycle determining unit for determining, a threshold setting processing unit for setting a threshold based on a maximum value and a minimum value obtained during the passage of the detection target in at least one cycle, and a threshold set by the threshold setting processing unit. And a measuring unit for discriminating an output obtained from the detecting unit based on the measuring unit.

According to a twelfth aspect of the present invention, there is provided a threshold value setting method in a detection apparatus for detecting detection targets sequentially passing by comparing a detection signal according to an external physical state with a threshold value and outputting a detection result signal. Thereupon, when the teaching start signal is input, sampling is performed every predetermined period, the maximum value of the detection signal obtained at each sampling is determined, and the minimum value of the detection signal obtained at each sampling is determined, Determine whether the detection signal obtained from the detection unit does not continuously update the maximum value and the minimum value,
In the case where the update is not performed continuously for a predetermined number of times, one cycle of the passage of the detection target is determined, and the threshold is set based on the maximum value and the minimum value obtained at least during the passage of one cycle.

[0018]

FIG. 1 is a block diagram showing a configuration of a photoelectric sensor according to a first embodiment of the present invention. In the photoelectric sensor 1A according to the present embodiment, the light projecting unit 2 drives a light projecting element that emits light at a single cycle or a plurality of wavelengths at a fixed cycle, and the light receiving unit 3 emits light reflected from the object detection area. The light is received, converted into an electric signal, and output to the control unit 4A. The control unit 4A is constituted by, for example, a microcomputer and has the following functions. The measuring unit 5 in the control unit 4A generates a light emitting pulse at regular intervals, drives the light emitting unit 2, determines a light receiving level from the light receiving unit 3, and outputs an object detection signal. The control unit 4A includes, in addition to the measurement unit 5, an initial value acquisition unit 6 for acquiring an initial light reception amount required for recognizing a work passage cycle. The initial value light reception amount and the acquired light reception amount are described later. A data comparing unit 7 for detecting one cycle of work passage, a threshold setting processing unit 8 for setting a threshold from the maximum and minimum values of the received light level held based on the comparison result, and sampling the amount of received light. A sampling processing unit 9 for transmitting and receiving light to perform
It is configured to include a memory unit 10 for holding data of the amount of received light. The external input unit 11 outputs a teaching input directly input from another device or a user to the control unit 4A as described later.
Numeral 2 outputs an answerback signal at the end of teaching and an object detection signal from the measuring unit 5 to the outside.

FIGS. 2A and 2B are diagrams showing the configuration of an external device connected to the photoelectric sensor. As shown in this figure, a programmable controller 20 or a manual input switch means or the like is alternatively connected to the photoelectric sensor. FIG.
When the programmable controller 20 is connected as shown in FIG.
1 is an external input unit 1 on the photoelectric sensor side via the output unit 22.
1 is input with a trigger signal for starting teaching. When the photoelectric sensor 1 has successfully completed the teaching,
An answerback signal is output from the external output unit 12.
The input unit 23 of the programmable controller 20 is connected to the external output unit 12 of the photoelectric sensor 1, and upon receiving this signal, the programmable controller 20 can determine that the threshold has been updated. Further, the presence or absence of an object can be identified on the programmable controller side by the object detection signal transmitted thereafter. After outputting the teaching signal, the programmable controller determines that the measurement information from the photoelectric sensor is invalid until the answerback signal is detected, and that the measurement output after outputting the answerback signal is valid.

In the photoelectric sensor 1A, a manual input switch 24 is connected to the external input unit 11 as shown in FIG.
A display 25 for confirmation may be connected to the external output unit 12. When a trigger signal for starting the teaching is input from the manual input switch 24 by connecting in this manner, an answer back signal after the end of the teaching is input to the display 25 for confirmation, and the end of the teaching can be confirmed.

Next, a threshold value setting process according to the first embodiment of the present invention will be described with reference to flowcharts and time charts. In the photoelectric sensor 1A according to this embodiment, as shown in FIG. 3A, the workpieces 26 are sequentially transported at substantially constant intervals on a transport line such as a conveyor.
It is assumed that the work 26 is used for detection. When a threshold value is set for the photoelectric sensor 1A when such a workpiece is detected, a trigger signal for starting teaching is input to the photoelectric sensor 1A from the programmable controller 20 or the manual input switch 24 as described above.

FIG. 4 is a flowchart showing a teaching process after a teaching signal is input. When teaching is started, a sampling process is first performed in step S1, and a constant light amount is set in step S2 with respect to the received light amount at that time. The width range is set up and down to be the initial range. For example, when a teaching input is given at time t ₁ in the background state as shown in FIG.
As shown in the figure, the time t _{2 in} the intermediate state of work detection from the background.
When a teaching input is given to the user and FIG. 5 (c)
When the teaching input is given at time t ₃ of the detection state of the workpiece as shown in, the region indicated by hatching in each illustrated as the initial range. And steps S3 and S4
The sampling process is repeated until the value falls outside the initial range. If the value falls outside the initial range, the process proceeds to steps S5 and S6 to return to the initial range again, and thereafter, it is determined whether or not the value falls outside the initial range. For example, in the state shown in FIG. 5A, when the workpiece detection state is reached, the initial range is deviated, and the background state is restored. When the time t ₅ the next work close to the light receiving level rises, the step S for outside this initial range
Go to 7. Also, as shown in FIG. 5B, when teaching is started from a state intermediate between the background and the work, the light receiving level decreases again after the work reaches the work detection state.
Therefore, at time t ₄ , the process returns to the initial range and goes out of the initial range again. Further, when teaching is started in the work detection state, as shown in FIG. 5C, once the background is detected, and then the next work is detected again, so that the signal from the work decreases. out of the initial range at time t _7, the process proceeds to step S7.
In step S7, it is determined whether or not the light receiving level has changed across the initial range when it has deviated from the initial range. If it does not change across the initial range, it is determined that the teaching input has been made on the work or the background as shown in FIG. 5A or 5C, and one cycle has been recognized so far (step S8). . On the other hand, in step S7,
When crossing the initial range and out of the initial range (time t ₄ )
In step S9, as shown in FIG. 5B, it is determined that a teaching input has been made at a light receiving level intermediate between the background and the work (step S9). In this case, step S10,
After returning to the initial range by proceeding to S11, it is determined whether or not the initial range has been exceeded. In the case of FIG. 5B, time t ₆
After returning to the initial range again, it goes out of the initial range.
At this time, it is determined that one cycle period has elapsed.

If it is determined that the cycle is one cycle, the process proceeds from step S8 or S10 to step S12, where it is determined whether or not a predetermined number of cycles has been reached.
If the set cycle has not been reached, the process returns to the loop of steps S5 and S6 to repeat the same processing. Step S
During the sampling processing of steps S4, S6 and S11, the maximum and minimum values of the light receiving level obtained at that time are updated and held. When the number of set cycles has been reached in step S12, the process proceeds to step S13, and the threshold setting processing unit 8 performs threshold setting processing. In the threshold setting process, for example, the median of the maximum value and the minimum value during the sampling process is set as the threshold. After ending the threshold setting process in this way, the process proceeds to step S14, at which time the answerback signal indicating the completion of the teaching process is output from the external output unit 12 to the programmable controller 20 or the like. This allows the programmable controller to recognize that the teaching process has been completed normally. After setting the threshold, the process proceeds to the measurement processing routine.

In the flowchart shown in FIG. 4, steps S1, S4, S6 and S11 achieve the function of the sampling processing unit 9, steps S1 and S2 achieve the function of the initial value acquisition unit 6, and Steps S3 to S1
0 achieves the function of a data comparison unit that determines one cycle of passage of the detection target based on the change state from the initial range. Steps S12 and S13 include the maximum value obtained when the detection target passes at least one cycle and The function of the threshold value setting processing unit 8 for setting a threshold value based on the minimum value is achieved.

FIG. 6 is a flowchart showing the measuring process. When the measuring process is started, first, in step S21, an external input is monitored to determine whether there is a teaching input. If there is a teaching input, the process proceeds from step S22 to step S1 to perform the above-described teaching process. When the teaching input is detected, the light is projected from the light projecting unit 2 to the object detection area in step S23, and the light receiving level from the light receiving unit 3 is detected. And step S25
The presence or absence of a workpiece is determined based on whether or not the light receiving level has been exceeded in step (1). Then, the process proceeds to step S26, in which the determination result is output from the external output unit 12 to the outside. This allows the programmable controller 20 to recognize the signal output from the external output unit 12 as an object detection signal.

Next, a photoelectric sensor according to a second embodiment of the present invention will be described. FIG. 7 is a block diagram of a photoelectric sensor according to the second embodiment. The same parts as those in the above-described first embodiment are denoted by the same reference numerals, and detailed description is omitted. The photoelectric sensor 1B according to the present embodiment is different from the photoelectric sensor 1B in part of the configuration of the control unit 4B. That is, the control unit 4B has a difference value calculation unit 31 that calculates a difference between light reception levels by two consecutive samplings, and a light reception cycle determination unit 32 that determines one cycle of work passage based on the level of the difference value. ing. The threshold setting unit 8 sets a threshold based on the light receiving level held during at least one cycle of the light receiving state.

Next, a teaching process according to the second embodiment will be described with reference to flowcharts and time charts. In this embodiment, when the teaching process is started, the sampling process is first performed in step S31, and the first received light amount is stored in the area of the previous sampling value in the memory unit 10 in step S32. Then, the process proceeds to steps S33 and S34, where the sampling process is performed at a fixed period, and the next received light amount obtained by the sampling process is stored in the current sampling value area. Next, in step S35, a difference value (= current sampling value−previous sampling value) is calculated from the previous and current sampling values. Then, the process proceeds to step S36 to move the current sampling value to the area of the previous sampling value. Next, the routine proceeds to step S37, where it is determined whether or not the difference value is within a predetermined range ± α. FIG. 9 is a time chart showing the light receiving level, the difference value, and the state determination result. Since the change in the threshold value is small within the range of ± α, the work can be determined to be state 1, that is, the state where the work is detected in this time and the state where the work is detected in the previous time or the light reception in the background state. Therefore, the received light amount is held as threshold setting data. If the difference value does not fall within this range in step S37, it is determined as state 2, that is, a change state between the workpiece and the background, and is not stored as threshold setting data (step S39). Then, in step S40, it is determined whether or not the number of transitions from state 1 to state 2 has reached the set value, and if not, the flow returns to step S33 to repeat the same processing. This set number must be two or more. State 1
When the number of transitions from “1” to “2” has reached the set number, step S41
To set a threshold using the threshold setting data. For example, the threshold value is set to an intermediate value between the maximum value and the minimum value of the threshold value setting data. Then, the process proceeds to step S42 to output an answer back signal to the controller 20 side, and proceeds to the measurement processing of FIG. In this way, teaching can be easily performed, and the threshold setting process can be performed even while the workpiece is passing.

Here, the control section 4B determines in step S3
In steps S32, S34, and S36, the function of the difference value calculating section 31 that calculates the difference value between the detection signals is achieved in steps S32, S34, and S36. In steps S37 to S39, the function of the light receiving cycle determination unit 32 for determining one cycle of passing the detection target based on the state of the change in the absolute value of the difference value is achieved. Steps S40 and S41 perform at least one cycle of the detection target. The function of the threshold value setting processing unit 8 for setting a threshold value based on the maximum value and the minimum value of the detection signal obtained while the passage is determined is achieved.

Next, a third embodiment of the present invention will be described with reference to the block diagram of FIG. In the present embodiment, the second embodiment can be applied to a photoelectric sensor in which the sampling period is randomized in order to prevent disturbance light and to prevent mutual interference. This embodiment is different from the second embodiment in that the difference value calculating unit 3
The only difference is that a differential value calculation unit 41 for calculating a differential value is provided in place of 1, and the other points are the same as in the second embodiment. In this embodiment, when the sampling interval is T in step S35 of the flowchart shown in FIG. 8, a differential value is calculated by the following equation instead of the difference value between the previous and current sampling. Differential value = | previous sample value |-| current sample value | ÷ T In this manner, the differential value is obtained. In step S37, states 1 and 2 are determined based on the differential value, and a threshold value is set as in FIG.

In this way, for a photoelectric sensor having a non-constant sampling interval, the teaching input can be triggered in the same manner as in the second embodiment by using the differential value instead of the difference value according to the second embodiment. The threshold setting can be performed automatically.

Next, a fourth embodiment of the present invention will be described. FIG. 11 shows a photoelectric sensor 1 according to a fourth embodiment.
FIG. 3 is a block diagram showing the configuration of D, and the same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description is omitted. In this embodiment, the control unit 4D includes a maximum value calculation unit 51, a minimum value calculation unit 52, and a cycle determination unit 53 that determines whether a predetermined number of cycles has been completed. Other configurations are the same as those of the above-described embodiment.

Next, the operation of this embodiment will be described with reference to FIG.
A description will be given with reference to the flowchart of FIG. In this embodiment, when the teaching process is started, the sampling process is first performed in step S51, and the first received light amount is stored in the MIN buffer and the MAX buffer of the memory in step S52. Next, a sampling process is performed in step S53, and the obtained amount of received light is MAX.
It is determined whether the value exceeds the buffer value and whether the value is less than the MIN buffer value (steps S54 and S5).
5). If it exceeds the MAX value, the process proceeds to step S56 to update the MAX buffer and clear the MAX counter flag and the MAX counter (step S57).
If the value is less than the value of the MIN buffer, the flow advances to step S58 to update the MIN buffer, and the flow advances to step S59 to clear the MIN flag and the MIN counter. Then, returning to step S53, the sampling process is performed, and the same process is repeated.

If the amount of received light is a value between the MAX and MIN buffers, the process proceeds from steps S54 and S55 to step S60 to check whether the value of the MAX buffer was updated last time. If it has been updated, the flow advances to step S61 to set the MAX counter flag, and returns to the loop of step 53. If it is determined in step S60 that the MAX value has not been updated last time, the process proceeds to step S62, where M
Check whether the value of the IN buffer has been updated. If the MIN buffer has been updated, step S63
To set the MIN counter flag, and
Return to 53. If the MAX buffer and the MIN buffer have not been updated in steps S60 and S62, FIG.
The process proceeds to step S64 of 3 to check whether the MAX counter flag is set. If the counter flag is set, the process proceeds to step S65 to increment the MAX counter. If the flag is not set, the process proceeds to step S66 without performing the process of step S65 and the MIN counter flag is set. To determine if it has been done. If this flag has been set, the flow proceeds to step S67 to increment the MIN counter. If the flag has not been set, the flow proceeds to step S68 without performing this processing, and whether or not both the MAX counter and the MIN counter have reached predetermined values. Check. This predetermined value is set to an appropriate value that can detect that there is no change because the light reception level continuously changes before and after the work detection, and then stops changing multiple times based on the sampling timing and the moving speed of the work. Shall be kept.

In this way, when both counter values reach the specified values, the maximum value and the minimum value include both the light receiving levels of the presence or absence of the object, and that one workpiece has passed (one cycle). I understand. Therefore, the process proceeds to step S69 to determine whether or not a predetermined number of cycles has been reached. If the predetermined number of cycles has not been reached, the flow returns to step S53 to repeat the same processing. If the predetermined number of cycles has been reached, threshold setting processing is performed in step S70. The threshold value setting process is set based on the maximum value and the minimum value held in the MAX buffer and the MIN buffer that have already been obtained. For example, the threshold value is set to an intermediate value between them. Then, the process proceeds to step S71 to output an answer back signal to the controller side, and then proceeds to the measurement process of FIG. In this way, the threshold can be automatically set using the teaching input as a trigger.

Here, the control unit 4D determines in step S5
1 and S53, the function of the sampling processor 9 is achieved. The functions of the maximum value calculator 51 for calculating the maximum value in steps S54 and S56, and the function of the minimum value calculator 52 for calculating the minimum value in steps S55 and S58. Have achieved. Steps S57 and S59 and step S60
In steps 68 to 68, it is determined whether the detection signal does not continuously update the maximum value and the minimum value. ing. Step S6
9. In S70, the function of the threshold value setting processing unit 8 for setting the threshold value based on the maximum value and the minimum value obtained during at least one cycle is achieved.

Next, a fifth embodiment of the present invention will be described. In this embodiment, as in the fourth embodiment, after the maximum value and the minimum value are once calculated, a predetermined range from the maximum value and the minimum value is defined as a MAX range and a MIN range, and the output state is defined by the stay time. It is made possible. FIG. 14 shows a photoelectric sensor 1E according to the fifth embodiment.
FIG. 4 is a block diagram showing a configuration of a control unit 4E of FIG.
The same parts as those in the above-described fourth embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. In this embodiment, the control unit 4E includes a maximum value calculation unit 51, a minimum value calculation unit 52, and a cycle determination unit 53 of the fourth embodiment, and a MAX.
It has a light receiving amount data measuring unit 54 for measuring light receiving amount data in the range and the MIN range, a stay time data measuring unit 55 staying in the MAX range and the MIN range, and an output setting unit 56. The received light amount data measurement unit 54 measures the average value of the data of the received light amount in the MAX range and the MIN range.
The stay time data measuring unit 55 measures the time in the MAX range and the MIN range, and the output setting unit 56 identifies and sets which output is to be output at which output level based on the data. It is.

Next, the operation of this embodiment will be described with reference to FIG.
Will be described with reference to the flowchart of FIG. After setting the threshold value by the above-described teaching process, in step S81, the MAX range and the MIN range are obtained from the maximum value stored in the MAX buffer and the minimum value stored in the MIN buffer. MAX range, MI
The N range is a predetermined range including the maximum value and the minimum value as shown in FIG. 16, and is set so as not to overlap each other. Then, the process proceeds to step S82 to perform a sampling process to obtain the amount of received light. Then, in a step S83, it is determined whether or not the light receiving amount is within the MAX range and the MIN range. M
If it is within the AX range, in steps S85 and S86, M
The received light amount data and stay time data in the AX range are accumulated. Similarly, if the received light amount is within the MIN range, step S
At 87 and 88, received light amount data and stay time data in the MIN range are accumulated. At this time, the stay time data holds the integrated value, and the received light amount data indicates the MAX range and M
It is assumed that the average value within the stay time in the IN range is held. If it is not the MAX range or the MIN range, the process proceeds to step S89 without performing these processes, and it is determined whether the change from the MAX range to the MIN range has reached the set number of times. If the number has not reached the set number, the process returns to step S82 and the same processing is repeated. In this way, only when the light receiving level is in the MAX range and the MIN range as shown in FIG. 16, the average value of the light receiving amount and the stay time can be measured.
The data as shown in FIGS. 17A and 17B is held. For example, when data in the MAX range and the MIN range is obtained five times, the data is totaled, and FIG.
On the maximum value side shown in (a), the minimum value of V _{MAX and} the minimum value of T _MAX are used as final decision data. Similarly, FIG.
On the other hand, the maximum value of V _MIN of the received light amount and the minimum value of V _MIN as the stay time are determined as the final determination data on the minimum value side shown in FIG.

Next, it is determined which of the T _MAX minimum value and the T _MIN minimum value is shorter. For example the smaller the time T _MAX, can be determined MAX-side light-receiving level is higher as shown in FIG. 16 (a) is that the detection state of the workpiece, a low light level MIN side it can be determined that the background. Accordingly, the output is such that the object detection signal is turned on when the light receiving level becomes higher than the threshold value. Further, if the time during which the value is within the MAX value is long as shown in FIG. 16B, the output is set so that the workpiece is detected in the time zone where the light receiving level is low.

This eliminates the need for the user to select either dark-on or light-on again, and can output an object detection signal desired by the user, thus enabling complete auto-teaching. The above-mentioned threshold value may be corrected based on the minimum value of V _{MAX and} the maximum value of V _MIN obtained at this time, and the output is set by merely measuring the stay time without accumulating the received light amount. You may make it. In the fifth embodiment, the output is set based on the stay time in the MAX range and the MIN range in order to set the output after the processing of the fourth embodiment.
In any of the embodiments, the maximum value and the minimum value obtained when the workpiece passes the predetermined number of cycles are calculated, and thereafter, the stay time is accumulated and the output setting process is performed as in the fifth embodiment. be able to.

In this embodiment, a photoelectric sensor for determining the presence or absence of a normal object has been described. However, the present invention is not limited to a sensor for detecting a normal object, and the present invention is not limited thereto.
Mark 2 attached to the object on the line as shown in (b)
Needless to say, the present invention can be applied to a mark sensor that detects 7 as a workpiece. In each of the embodiments described above, the photoelectric sensor is described. However, the present invention is not limited to the photoelectric sensor, but can be applied to various other types of detectors such as a proximity sensor, a pressure sensor, and an ultrasonic sensor. In the case of a photoelectric sensor, a light receiving signal is used as a detection signal. However, in a proximity sensor, a signal indicating a change in the oscillation state, for example, an oscillation amplitude signal is used as a detection signal. In the mark sensor, a detection signal is a light reception signal of reflected light from the mark, in the pressure sensor, a pressure signal introduced into the sensor, and in an ultrasonic sensor, an ultrasonic reception signal is a detection signal. Also, in each embodiment, the threshold value is set based on the maximum value and the minimum value, but a representative value near the maximum value may be used instead of the strict maximum value,
Also, a value obtained by subtracting the margin level from the maximum value, and the maximum value is 1
The maximum value may be obtained by using a value obtained by multiplying a smaller constant. Similarly, the minimum value may be a representative value near the minimum value, a value obtained by adding a margin level to the minimum value, or a value obtained by multiplying the minimum value by a constant slightly larger than 1. Further, the threshold value is set at the median of the maximum value and the minimum value in each of the above-described embodiments, but is not limited to the median value, and a value between them can be set as appropriate.

When the detection signal does not show a change expected in advance when setting the threshold value, for example, in the first embodiment, when the detection signal does not change from the initial range within a predetermined time or returns to the initial range within a predetermined time. A threshold setting error may be reported when there is no such error. When the state determination cannot be performed accurately, such as when the difference value is not appropriate in the second embodiment and the differential value is not appropriate in the third embodiment,
In the fifth embodiment, when the MAX range and the MIN range are not appropriate and a normal operation cannot be performed, an error process may be performed as a threshold setting error.

[0042]

As described above in detail, according to the first to twelfth aspects of the present invention, it is possible for the detecting device to automatically recognize the passage cycle of the detection target and determine the time for sampling. Since the threshold can be set based on a plurality of cycles, sampling can be performed for an optimum time by simply inputting the teaching start without stopping the transport line, and the threshold can be set. Therefore, generation of useless work can be reduced as much as possible. Also, there is no need to stop the transport line, and even when the transport speed of the transport line is not constant, it is possible to set a detection cycle and set a threshold value by sampling according to the transport state only by giving a teaching input from the outside. Is obtained. According to the ninth and tenth aspects,
In order to prevent mutual interference, the present invention can also be applied to a detector having a random sampling period,
The effect is obtained that the threshold value can be automatically set.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a photoelectric sensor according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a photoelectric sensor according to the first embodiment of the present invention and a controller connected to the photoelectric sensor.

FIG. 3 is a schematic diagram showing a usage state of the photoelectric sensor according to the first embodiment of the present invention.

FIG. 4 is a flowchart illustrating a threshold setting method according to the first embodiment of the present invention.

FIG. 5 is a graph showing a change in a light receiving level in a threshold setting process according to the first embodiment of the present invention.

FIG. 6 is a flowchart illustrating measurement processing of the photoelectric sensor according to the first embodiment of the present invention.

FIG. 7 is a block diagram of a photoelectric sensor according to a second embodiment of the present invention.

FIG. 8 is a flowchart illustrating a threshold setting method according to a second embodiment of the present invention.

FIG. 9 is a graph showing a change in a light receiving level in a threshold value setting process of the photoelectric sensor according to the second embodiment of the present invention.

FIG. 10 is a block diagram showing a configuration of a photoelectric sensor according to a third embodiment of the present invention.

FIG. 11 is a block diagram showing a configuration of a photoelectric sensor according to a fourth embodiment of the present invention.

FIG. 12 is a flowchart (part 1) illustrating a threshold setting process of the photoelectric sensor according to the fourth embodiment of the present invention.

FIG. 13 is a flowchart (part 2) illustrating a threshold setting process of the photoelectric sensor according to the fourth embodiment of the present invention.

FIG. 14 is a block diagram showing a configuration of a photoelectric sensor according to a fifth embodiment of the present invention.

FIG. 15 is a flowchart showing an operation of the photoelectric sensor according to the fifth embodiment of the present invention.

FIG. 16 is a time chart showing changes in a light receiving level and a stay time of a photoelectric sensor according to a fifth embodiment of the present invention.

FIG. 17 is a diagram illustrating an average light reception amount and a stay time in a MAX range and a MIN range of the photoelectric sensor according to the fifth embodiment of the present invention.

FIG. 18 is a diagram showing a light receiving level and a teaching input obtained by a conventional photoelectric sensor.

[Explanation of symbols]

 1A, 1B, 1C, 1D, 1E Photoelectric sensor 2 Light emitting unit 3 Light receiving unit 4A, 4B, 4C, 4D, 4E Control unit 5 Measurement unit 6 Initial value acquisition unit 7 Data comparison unit 8 Threshold setting processing unit 9 Sampling processing unit DESCRIPTION OF SYMBOLS 10 Memory part 11 External input part 12 External output part 20 Programmable controller 21 Programmable controller main body 22 Input part 23 Output part 24 Manual input switch 25 Display 31 Difference value calculation part 32 Light receiving cycle determination part 41 Differentiation value calculation part 51 Maximum value calculation Unit 51 minimum value calculation unit 53 cycle determination unit 54 stay time data measurement unit 55 received light amount data measurement unit 56 output setting unit

Claims (12)

[Claims] 1. A detection unit that outputs a detection signal according to an external physical state, and a predetermined range including a level of a detection signal obtained from the detection unit when a teaching start signal is input is set as an initial range. The value acquisition unit, after the detection signal changes from the initial range, a detection signal within the initial range is obtained again, and when the detection signal changes without crossing the initial range, and after the detection signal changes from the initial range, the initial value is reset again. A data comparison unit that determines that one of the cases where the detection signal within the initial range is obtained and the detection signal within the initial range is obtained three times after the detection signal within the initial range is obtained after changing across the initial range; A threshold setting processing unit configured to set a threshold based on a maximum value and a minimum value obtained when the detection target of at least one cycle detected by the data comparison unit passes, and a threshold setting processing unit. Sensing apparatus characterized by having a measuring unit for discriminating the output obtained from said detecting unit on the basis of the threshold. 2. A threshold setting method in a detection device for detecting a detection object sequentially passing by comparing a detection signal according to an external physical state with a threshold and outputting a detection result signal, wherein the teaching start signal is A predetermined range including the level of the detection signal obtained when input is set as an initial range, and after the detection signal changes from the initial range, a detection signal within the initial range is obtained again, without crossing the initial range. In either case, after the detection signal changes from the initial range, a detection signal within the initial range is obtained again, and after changing across the initial range, a detection signal within the initial range is obtained three times. One is determined as one cycle of the passage of the detection target, and a threshold is set based on the maximum value and the minimum value of the detection signal obtained during at least one cycle of the passage of the detection target. A threshold setting method. 3. A detection unit for outputting a detection signal according to an external physical state, and a predetermined range including a level of the detection signal obtained from the detection unit when a teaching start signal is input, as an initial range. The value acquisition unit detects the detection signal within the initial range again after the detection signal has changed from the initial range, and detects the detection signal within the initial range three times after changing across the initial range. A data comparison unit that determines one cycle of the passage of the target; a threshold setting processing unit that sets a threshold based on a maximum value and a minimum value obtained when the detection target of at least one cycle detected by the data comparison unit passes. And a measurement unit that discriminates an output obtained from the detection unit based on a threshold value set by the threshold value setting processing unit. 4. A threshold setting method for a detection device for detecting a detection target sequentially passing by comparing a detection signal according to an external physical state with a threshold and outputting a detection result signal, wherein the teaching start signal is A predetermined range including the level of the detection signal obtained when input is set as the initial range. After the detection signal changes from the initial range, a detection signal within the initial range is obtained again, and the detection signal changes across the initial range. Thereafter, a case where a detection signal within the initial range is obtained three times is determined as one cycle of passage of the detection target, and the maximum value and the minimum value of the detection signal obtained during the passage of the detection target of at least one cycle are determined. A threshold setting method based on the threshold value. 5. A detection section for outputting a detection signal according to an external physical state, and a predetermined range including a level of a detection signal obtained from the detection section when a teaching start signal is input as an initial range. A value acquisition unit, and a data comparison unit that, after the detection signal changes from the initial range, obtains a detection signal within the initial range again, and determines that the detection signal changes without crossing the initial range as one cycle of passage of the detection target. A threshold setting processing unit that sets a threshold based on a maximum value and a minimum value obtained when the detection target of at least one cycle detected by the data comparison unit passes, and a threshold set by the threshold setting processing unit. A measuring unit for discriminating an output obtained from the detecting unit based on the detecting unit. 6. A threshold value setting method in a detection device for detecting a detection target sequentially passing by comparing a detection signal according to an external physical state with a threshold value and outputting a detection result signal, wherein the teaching start signal is A predetermined range including the level of the detection signal obtained when input is set as an initial range, and after the detection signal changes from the initial range, a detection signal within the initial range is obtained again, without crossing the initial range. A threshold value is determined based on a maximum value and a minimum value of the detection signal obtained during at least one cycle of the passage of the detection target. Setting method. 7. A detection unit that outputs a detection signal according to an external physical state at predetermined intervals, and a difference value between the detection signals for each detection signal obtained from the detection unit when a teaching start signal is input. A difference value calculation unit that calculates the detection signal when the absolute value of the difference value obtained from the difference value calculation unit is within a predetermined range, and detects a detection target based on a change state of the absolute value of the difference value. A cycle determination unit configured to determine one cycle of passage, a threshold setting processing unit configured to set a threshold based on a detection signal held while the passage of the detection target in at least one cycle is determined by the cycle determination unit; A detection device comprising: a measurement unit that discriminates an output obtained from the detection unit based on a threshold value set by a threshold value setting processing unit. 8. A threshold setting method for a detection device for detecting a detection object sequentially passing by comparing a detection signal according to an external physical state with a threshold and outputting a detection result signal, wherein the teaching start signal is Sampling is performed every predetermined period after the input, a difference value between the detection signals obtained at each sampling is calculated, and the data of the detection signal is held when the absolute value of the difference value is within a predetermined range. Determining one cycle of the detection target passage based on a state of a change in the absolute value of the difference value, and setting a threshold based on a detection signal held during at least one cycle of the detection target passage. Threshold setting method. 9. A detection unit that outputs a detection signal according to an external physical state, and a differential value that calculates a differential value of the detection signal for each detection signal obtained from the detection unit when a teaching start signal is input. A calculating unit for holding data of the detection signal when the absolute value of the level of the differential value is within a predetermined range, and determining one cycle of passing through the detection target based on a change state of the absolute value of the differential value A threshold setting unit configured to set a threshold based on a detection signal held during the passage of the detection target in at least one cycle by the cycle determining unit; and a threshold set by the threshold setting unit. And a measuring unit for discriminating an output obtained from the detecting unit. 10. A threshold setting method for a detection device for detecting a detection target sequentially passing by comparing a detection signal according to an external physical state with a threshold and outputting a detection result signal, wherein the teaching start signal is Sampling is performed intermittently when input, the differential value is calculated for each detection signal obtained for each sampling, and the data of the detection signal is held when the absolute value of the differential value is within a predetermined range. Determining one cycle of passage of the detection target based on a state of a change in the absolute value of the differential value, and setting a threshold based on a detection signal held during at least one cycle of passage of the detection target. Threshold setting method. 11. A detection unit that outputs a detection signal according to an external physical state at predetermined intervals, and a maximum value that determines a maximum value of the detection signal obtained from the detection unit when a teaching start signal is input. A determination unit; a minimum value determination unit configured to determine a minimum value of the detection signal obtained from the detection unit when a teaching start signal is input; and a maximum value and a minimum value of the detection signal obtained from the detection unit continuously. A cycle discriminator for discriminating whether or not to update the data, and discriminating one cycle of passage of the detection target when the update is not performed continuously for a predetermined number of times; a maximum value and a minimum value obtained during the passage of the detection target for at least one cycle A threshold setting processing unit that sets a threshold based on the threshold value, and a measurement unit that discriminates an output obtained from the detection unit based on the threshold set by the threshold setting processing unit. Sensing apparatus according to claim and. 12. A threshold setting method in a detection device for detecting a detection object sequentially passing by comparing a detection signal according to an external physical state with a threshold and outputting a detection result signal, wherein the teaching start signal is Sampling is performed every predetermined period when input, and the maximum value of the detection signal obtained at each sampling is determined. The minimum value of the detection signal obtained at each sampling is determined. It is determined whether the signal does not continuously update the maximum value and the minimum value. If the signal is not updated continuously for a predetermined number of times, one cycle of the detection target passage is determined, and the maximum value obtained when at least one cycle passes. And setting a threshold based on the minimum value.