JP3548881B2 - Detection apparatus and threshold setting method thereof - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a detection device having a feature in threshold setting of a photoelectric sensor, a proximity sensor, and the like, and a threshold setting method thereof.
[0002]
[Prior art]
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, a threshold value needs to be set in 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]
Auto-teaching is used as a teaching method without manual intervention. 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 value based on the maximum and minimum values of the amount of received light during this period.
[0004]
[Problems to be solved by the invention]
However, according to such a conventional teaching method, when performing one-point teaching or two-point teaching, the user stops the transport line and places the work at a predetermined position so that the amount of received light can be sampled. In addition, it is necessary to perform teaching as a background state without arranging a work. In the case of auto-teaching, it is not necessary to stop the transport line, but the user must recognize the optimal input time and timing of the 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 lot of work is wasted when the conveying line is high speed.
[0005]
The present invention has been made in view of such conventional problems, and when setting a threshold value of an object to be detected passing through a transport line, simply inputting a teaching start without stopping the transport line. Therefore, an object of the present invention is to enable a threshold to be automatically set.
[0006]
[Means for Solving the Problems]
According to the first aspect of the present invention, a detection unit that outputs 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 are initialized. The initial value acquisition unit as a 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 the detection signal changes from the initial range. Thereafter, a 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 determined as one cycle of passage of the detection target. A data comparison unit, 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 the threshold setting processing unit It is characterized in that it has a, a measuring unit for discriminating the output obtained from the detection unit based on the set threshold value I.
[0007]
The invention according to claim 2 of the present application is a threshold setting method in a detection device that detects a detection target sequentially passing by comparing a detection signal according to an external physical state with a threshold, and outputs 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. After the detection signal changes from the initial range, a detection signal within the initial range is obtained again, and the initial range is obtained. If the detection signal changes within 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 detection signal within the initial range is obtained three times. Is determined as one cycle of the passage of the detection target, and a threshold is determined 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. It is characterized in that setting.
[0008]
According to the invention of claim 3 of the present application, a detection unit that outputs 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 are initialized. With the initial value acquisition unit as the range, the detection signal within the initial range is obtained again after the detection signal changes from the initial range, and after the detection signal changes across the initial range, the detection signal within the initial range is obtained three times. A data comparing unit that determines that the detection target is one cycle of passage of the detection target, and a threshold that sets a threshold based on a maximum value and a minimum value obtained when the detection target passes at least one cycle detected by the data comparison unit. It has a setting processing part and a measuring part which discriminates the output obtained from the detection part based on the threshold value set by the threshold value setting processing part.
[0009]
The invention according to claim 4 of the present application is a threshold value setting method in a detection device that detects a detection target sequentially passing by comparing a detection signal according to an external physical state with a threshold value and outputs 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. After the detection signal changes from the initial range, a detection signal within the initial range is obtained again, and the initial range is obtained. When the detection signal within the initial range is obtained three times after changing across, it is determined as one cycle of the passage of the detection target, and the maximum value of the detection signal obtained during at least one cycle of the passage of the detection target And setting the threshold value based on the minimum value.
[0010]
According to a fifth aspect of the present invention, a detection unit that outputs 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 are initialized. An initial value acquisition unit that sets a range, a detection signal within the initial range is obtained again after the detection signal changes from the initial range, and a case where the detection signal changes without crossing the initial range is determined as one cycle of passage of the detection target. A threshold value setting 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 measuring unit that discriminates an output obtained from the detecting unit based on the threshold value obtained.
[0011]
The invention according to claim 6 of the present application is a threshold setting method in a detection device that detects a detection target sequentially passing by comparing a detection signal according to an external physical state with a threshold, and outputs 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. After the detection signal changes from the initial range, a detection signal within the initial range is obtained again, and the initial range is obtained. Is determined as one cycle of 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 the passage of the detection target of at least one cycle. It is a feature.
[0012]
The invention according to claim 7 of the present application is directed to a detection unit that outputs a detection signal according to an external physical state at predetermined intervals, and a detection signal for each detection signal obtained from the detection unit when a teaching start signal is input. A difference value calculation unit that calculates a difference value between the difference value calculation unit and the detection signal, when the absolute value of the difference value obtained from the difference value calculation unit is within a predetermined range, and a change in the absolute value of the difference value. A cycle discriminator for discriminating one cycle of passage of the detection target according to the state, and a threshold setting process for setting a threshold based on a detection signal held while the cycle discrimination unit determines that at least one cycle of the detection target has passed. And a measurement unit that discriminates the output obtained from the detection unit based on the threshold value set by the threshold value setting processing unit.
[0013]
The invention according to claim 8 of the present application is a threshold setting method in a detection device that detects a detection target sequentially passing by comparing a detection signal according to an external physical state with a threshold, and outputs a detection result signal, Sampling is performed at predetermined intervals after the input of the teaching start signal, and a difference value between the detection signals obtained at each sampling is calculated. When the absolute value of the difference value is within a predetermined range, the detection signal is calculated. Is determined, and one cycle of detection object passage is determined based on the state of change in the absolute value of the difference value, and a threshold value is set based on the detection signal held during at least one cycle of the detection object passage. It is characterized by the following.
[0014]
According to a ninth aspect of the present invention, a detection unit that outputs a detection signal according to an external physical state, and a differential value of the detection signal for each detection signal obtained from the detection unit when a teaching start signal is input. A differential value calculating section for calculating, and when the absolute value of the level of the differential value is within a predetermined range, the data of the detection signal is held, and one cycle of passing through the detection target according to a change state of the absolute value of the differential value. A threshold setting processing unit that sets a threshold based on the detection signal held during the passage of the detection target in at least one cycle by the cycle determining unit; and a threshold setting processing unit that sets the threshold. And a measuring unit that discriminates the output obtained from the detecting unit based on the threshold value.
[0015]
The invention according to claim 10 of the present application is a threshold setting method in a detection device that detects a detection target sequentially passing by comparing a detection signal according to an external physical state with a threshold, and outputs a detection result signal, Sampling is performed intermittently when a teaching start signal is input, a differential value is calculated for each detection signal obtained at each sampling, and when the absolute value of the differential value is within a predetermined range, the detection signal is calculated. Holding data, determining one cycle of detection object passage based on a state of 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 detection object passage. It is characterized by the following.
[0016]
The invention according to claim 11 of the present application is directed to a detection unit that outputs a detection signal corresponding to an external physical state at predetermined intervals, and a maximum value of the detection signal obtained from the detection unit when a teaching start signal is input. A maximum value discriminator for discriminating, a minimum value discriminator for discriminating a minimum value of a detection signal obtained from the detection unit when a teaching start signal is input, and a detection signal obtained from the detection unit continuously and maximally. A cycle determining unit that determines whether the value and the minimum value are not updated, and determines one cycle of passing the detection target if the updating is not performed a predetermined number of times continuously; and a maximum value obtained during at least one cycle of passing the detection target. A threshold setting processing unit that sets a threshold based on the value and the minimum 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. It is characterized in that it has.
[0017]
The invention according to claim 12 of the present application is a threshold setting method in a detection device that detects a detection target sequentially passing by comparing a detection signal according to an external physical state with a threshold, and outputs a detection result signal, 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, the minimum value of the detection signal obtained at each sampling is determined, It is determined whether or not the obtained detection signal continuously updates the maximum value and the minimum value. If the detection signal is not continuously updated a predetermined number of times, one cycle of the detection target passage is determined. The threshold value is set based on the obtained maximum value and minimum value.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a block diagram showing the configuration of the photoelectric sensor according to the 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 period, 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 the light receiving level from the light receiving unit 3, and outputs an object detection signal. The control unit 4A includes, in addition to the measuring unit 5, an initial value acquiring unit 6 for acquiring an initial light receiving amount necessary for recognizing a work passage cycle. The initial value receiving amount and the acquired light receiving amount are described later. A data comparing section 7 for detecting one cycle of the workpiece passing, a threshold setting processing section 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. And 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, and the external output unit 12 outputs an answerback signal at the end of the teaching or a measurement unit 5 from the measuring unit 5. Is output to the outside.
[0019]
FIGS. 2A and 2B are diagrams showing a configuration of an external device connected to the photoelectric sensor. As shown in the figure, a programmable controller 20 or a manual input switch means or the like is alternatively connected to the photoelectric sensor. When the programmable controller 20 is connected as shown in FIG. 2A, the programmable controller main body 21 inputs a trigger signal for starting teaching to the external input unit 11 on the photoelectric sensor side via the output unit 22. . When the photoelectric sensor 1 has normally completed the teaching, the external output unit 12 outputs an answerback signal. 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 answer back signal is detected, and determines that the measurement output after outputting the answer back signal is valid.
[0020]
As shown in FIG. 2B, a manual input switch 24 may be connected to the external input unit 11 and a display 25 for confirmation may be connected to the external output unit 12 of the photoelectric sensor 1A. When a trigger signal for starting the teaching is input from the manual input switch 24 by connecting in this way, an answer back signal after the teaching is completed is input to the display 25 for confirmation, and the completion of the teaching can be confirmed.
[0021]
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. As shown in FIG. 3A, the photoelectric sensor 1A according to the present embodiment is used for detecting the work 26 by transferring the work 26 at substantially constant intervals on a transfer line such as a conveyor. I do. 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.
[0022]
FIG. 4 is a flowchart showing the teaching process after the teaching signal is input. When the teaching is started, first, the sampling process is performed in step S1, and in step S2, a range of a predetermined width with respect to the received light amount at that time. Is set up and down to be the initial range. For example, as shown in FIG. ₁ When a teaching input is given to the camera, a time t in the intermediate state of workpiece detection from the background as shown in FIG. ₂ When a teaching input is given to the workpiece and the time t when the workpiece is detected as shown in FIG. ₃ When a teaching input is given to the user, the regions indicated by hatching in the drawings are set as initial ranges. Then, in steps S3 and S4, the sampling process is repeated until the value falls outside the initial range. When the value falls outside the initial range, the process proceeds to steps S5 and S6 to return to the initial range again. For example, in the state shown in FIG. 5A, when the work detection state occurs, the initial range is deviated, and the state returns to the background state. And time t ₅ When the next work comes close to and the light receiving level rises, the process goes out of the initial range and the process proceeds to step S7. Also, as shown in FIG. 5B, when teaching is started from a state intermediate between the background and the work, the light receiving level is reduced again once the work is detected. Therefore, time t ₄ Then, the process returns to the initial range, and again goes out of the initial range. 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. Time t ₇ , And goes 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, if it is determined in step S7 that the current value crosses the initial range and falls outside the initial range (time ₄ 5), it is determined that a teaching input has been made at an intermediate light receiving level between the background and the work as shown in FIG. 5B (step S9). In this case, the process again proceeds to steps S10 and S11 to return to the initial range, and then it is determined whether or not the initial range has been exceeded. In the case of FIG. ₆ After returning to the initial range again, it is determined that one cycle period has elapsed since the initial range is deviated.
[0023]
If it is determined that the cycle is one cycle, the process proceeds to step S12 from step S8 or S10, and it is determined whether or not a predetermined number of cycles has been reached. If the number of cycles has not been reached, the process returns to the loop of steps S5 and S6. And repeat the same processing. During the sampling processing in steps S4, S6 and S11, the maximum and minimum values of the light reception level obtained at that time are updated and held. When the number of cycles reaches the set number in step S12, the process proceeds to step S13, and the threshold value setting processing unit 8 performs threshold value 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.
[0024]
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 S3. S10 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 determine 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 the threshold value based on the minimum value is achieved.
[0025]
FIG. 6 is a flowchart showing the measurement process. When the measurement 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, light is emitted 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. Then, in step S25, the presence or absence of a work is determined based on whether or not the light receiving level is exceeded. Then, the process proceeds to step S26 to output the determination result to the outside from the external output unit 12. This allows the programmable controller 20 to recognize the signal output from the external output unit 12 as an object detection signal.
[0026]
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 section 4B has a difference value calculating section 31 for calculating a difference between light receiving levels by two consecutive samplings, and a light receiving cycle determining section 32 for determining 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.
[0027]
Next, a teaching process according to the second embodiment will be described with reference to a flowchart and a time chart. In this embodiment, when the teaching process is started, a sampling process is first performed in step S31, and the first received light amount is held 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 to perform sampling processing at a fixed period, and stores the next received light amount obtained by the sampling processing 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 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 in the state 1, that is, the state where the work is detected in the current time and the state in which the work is detected last 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 work and the background, and is not stored as threshold setting data (step S39). Then, in step S40, it is determined whether the number of transitions from state 1 to state 2 has reached the set value, and if not, the process returns to step S33 and repeats the same processing. This set number must be two or more. When the transition from the state 1 to the state 2 has reached the set number of times, the process proceeds to step S41, and the threshold is set using the threshold setting data. For example, a threshold is set to an intermediate value between the maximum value and the minimum value of the threshold 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 in FIG. In this way, teaching can be easily performed, and the threshold setting process can be performed even while the workpiece is passing.
[0028]
Here, the control unit 4B achieves the function of the sampling processing unit 9 in steps S31 and S33, and achieves the function of the difference value calculation unit 31 that calculates the difference value between the detection signals in steps S32, S34, and S36. I have. In steps S37 to S39, the function of the light receiving cycle determining unit 32 for determining one cycle of passing the detection target according to the state of the change in the absolute value of the difference value is achieved. The function of the threshold value setting processing unit 8 that sets a threshold value based on the maximum value and the minimum value of the detection signal obtained while the passage is determined is achieved.
[0029]
Next, a third embodiment of the present invention will be described with reference to the block diagram of FIG. In this embodiment, the second embodiment can be applied to a photoelectric sensor in which a sampling period is randomized in order to prevent disturbance light and to prevent mutual interference. This embodiment is different from the above-described second embodiment only in that a differential value calculation unit 41 for calculating a differential value is provided in place of the difference value calculation unit 31, and the other points are the same as those in the second embodiment. This is the same as the embodiment. In this embodiment, in step S35 of the flowchart shown in FIG. 8, when the sampling interval is T, a differential value is calculated by the following equation instead of the difference value between the previous and current sampling.
Differential value = | previous sampling value |-| current sampling value | ÷ T
In this way, the differential value is obtained, and in step S37, states 1 and 2 are determined based on the differential value, and a threshold value is set as in FIG.
[0030]
In this way, even for a photoelectric sensor whose sampling interval is not constant, the differential value is used in place of the differential value according to the above-described second embodiment, so that the teaching input can be used as a trigger similarly to the second embodiment. Can be set for the threshold.
[0031]
Next, a fourth embodiment of the present invention will be described. FIG. 11 is a block diagram showing a configuration of a photoelectric sensor 1D according to the fourth embodiment. The same parts as those in the above-described first embodiment are denoted by the same reference numerals, and detailed description is omitted. In this embodiment, the control unit 4D has 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.
[0032]
Next, the operation of this embodiment will be described with reference to the flowcharts of FIGS. 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, in step S53, a sampling process is performed, and it is determined whether the obtained amount of received light exceeds the value of the MAX buffer and whether it is less than the value of the MIN buffer (steps S54 and S55). 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, the process returns to step S53, performs the sampling process, and repeats the same process.
[0033]
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 to check whether the value of the MIN buffer has been updated last time. If the MIN buffer has been updated, the flow advances to step S63 to set a MIN counter flag, and the flow returns to step S53. If the MAX buffer and the MIN buffer have not been updated in steps S60 and S62, the process proceeds to step S64 in FIG. 13 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 the flag has been set, the process proceeds to step S67 to increment the MIN counter. If the flag has not been set, the process proceeds to step S68 without performing this process, and whether the MAX counter and the MIN counter have reached the predetermined values. Check This predetermined value is set to an appropriate value that can detect that there is no change because the light receiving level continuously changes before and after the work detection and continuously stops after the work is detected multiple times based on the sampling timing and the moving speed of the work. Shall be kept.
[0034]
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 it can be seen that one work has passed (one cycle). 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 process returns to step S53 to repeat the same processing. If the predetermined number of cycles has been reached, a threshold setting process 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. 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.
[0035]
Here, the control unit 4D has achieved the function of the sampling processing unit 9 in steps S51 and S53, the maximum value calculation unit 51 calculating the maximum value in steps S54 and S56, and the minimum value calculating the minimum value in steps S55 and S58. The function of the value calculation unit 52 is achieved. In steps S57 and S59 and steps S60 to S68, it is determined whether or not the detection signal continuously updates the maximum value and the minimum value. If the detection signal is not continuously updated a predetermined number of times, one cycle of passing the detection target is determined. The function of the determination unit 53 is achieved. Further, the function of the threshold value setting processing unit 8 for setting a threshold value based on the maximum value and the minimum value obtained during at least one cycle in steps S69 and S70 is achieved.
[0036]
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 was made possible. FIG. 14 is a block diagram showing a configuration of a control unit 4E of a photoelectric sensor 1E according to the fifth embodiment. The same parts as those in the above-described fourth embodiment are denoted by the same reference numerals, and detailed description is 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 light reception amount for measuring light reception amount data in a MAX range and a MIN range. A data measurement unit 54, a stay time data measurement unit 55 staying in the MAX range and the MIN range, and an output setting unit 56 are provided. The received light amount data measuring unit 54 measures the average value of the received light amount data 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. The setting unit 56 identifies and sets which output is to be output at which output level based on the data.
[0037]
Next, the operation of this embodiment will be described with reference to the flowchart of FIG. 15 and the time chart 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. The MAX range and the MIN range are predetermined ranges including the maximum value and the minimum value as shown in FIG. 16, and are 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. If it is within the MAX range, the received light amount data and stay time data of the MAX range are accumulated in steps S85 and S86. Similarly, if the received light amount is within the MIN range, the received light amount data and stay time data of the MIN range are accumulated in steps S87 and S88. At this time, the stay time data holds an integrated value, and the received light amount data holds an average value within the stay time in the MAX range and the MIN range, respectively. 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 set number has not been reached, the process returns to step S82 to repeat the same processing. 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 received light amount and the stay time can be measured, as shown in FIGS. 17 (a) and (b). The data will be retained. For example, when data in the MAX range and the MIN range is obtained five times, the data is totaled. On the maximum value side shown in FIG. _MAX And T _MAX And the minimum value of are used as final decision data. Similarly, on the minimum value side shown in FIG. _MIN Maximum value of stay, V as stay time _MIN Is defined as the final decision data.
[0038]
Then T _MAX Minimum and T _MIN It is determined which of the minimum values is shorter. For example, T _MAX If the time is small, it can be determined that the MAX side with the higher light receiving level is in the work detection state, and the MIN side with the lower light receiving level is the background, as shown in FIG. Therefore, the output is such that the object detection signal is turned on when the light receiving level becomes higher than the threshold value. 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 reception level is low.
[0039]
This eliminates the need for the user to select either dark-on or light-on again, can output an object detection signal desired by the user, and enables complete auto-teaching. V obtained at this time _MAX , V _MIN The above-described threshold value may be corrected based on the maximum value, or the output may be set by merely measuring the stay time without accumulating the received light amount. 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 a predetermined number of cycles of workpieces are passed are calculated, and thereafter, the stay time is accumulated and the output setting process is performed as in the fifth embodiment. be able to.
[0040]
In this embodiment, a photoelectric sensor for determining the presence or absence of a normal object is described. However, the present invention is not limited to a sensor for detecting a normal object, and the present invention is not limited to a line sensor as shown in FIG. It goes without saying that the present invention can be applied to a mark sensor that detects the mark 27 attached to the upper object 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, and 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 an oscillation state, for example, an oscillation amplitude signal is used as a detection signal. In the mark sensor, the 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 the ultrasonic sensor, an ultrasonic reception signal is a detection signal. In each embodiment, the threshold value is set based on the maximum value and the minimum value. However, a representative value near the maximum value may be used instead of the strict maximum value, or a margin level is subtracted from the maximum value. The maximum value may be determined using a value obtained by multiplying the maximum value by a constant slightly smaller than 1. 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, in each of the above-described embodiments, the threshold value is set to the median of the maximum value and the minimum value. However, the threshold value is not limited to the median value, and a value between them can be set as appropriate.
[0041]
In addition, when the detection signal does not show a change expected in advance when setting the threshold value, for example, in the first embodiment, when there is no change from the initial range within a predetermined time, or when it does not return to the initial range within a predetermined time. For example, a threshold setting error may be notified. If 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, MAX is used in the fourth and fifth embodiments. If the 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]
【The invention's effect】
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 sampling time. Since the threshold can be set based on a plurality of cycles, sampling can be performed for an optimal 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 of the present invention, in order to prevent mutual interference, the present invention can be applied to a detector having a random sampling period, and the threshold value can be automatically set. Is obtained.
[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 illustrating 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 use 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 a measurement process 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 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 illustrating 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 teaching input obtained by a conventional photoelectric sensor.
[Explanation of symbols]
1A, 1B, 1C, 1D, 1E photoelectric sensor
2 Floodlight
3 Receiver
4A, 4B, 4C, 4D, 4E control unit
5 Measurement section
6 Initial value acquisition section
7 Data comparison section
8 Threshold setting processing section
9 Sampling processing unit
10 Memory section
11 External input section
12 External output section
20 Programmable Controller
21 Programmable controller body
22 Input section
23 Output section
24 Manual input switch
25 Display
31 Difference value calculation unit
32 Light receiving cycle discriminator
41 Differential value calculator
51 Maximum value calculation unit
51 Minimum value calculation unit
53 Cycle discriminator
54 Stay time data measurement unit
55 Received light data measurement unit
56 Output setting section

Claims (12)

A detection unit that outputs a detection signal according to an external physical state,
An initial value acquisition unit that sets a predetermined range including a level of the detection signal obtained from the detection unit when the teaching start signal is input as an initial range,
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 again within the initial range. Is obtained, and after changing across the initial range, a data comparing unit that determines one of the cases where a detection signal within the initial range is obtained three times 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,
A detector configured to distinguish an output obtained from the detector based on a threshold set by the threshold setting processor. A threshold setting method in a detection device that sequentially detects a detection target that sequentially passes by comparing a detection signal according to an external physical state with a threshold, and outputs 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 an initial range,
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 again within the initial range. Is obtained, and after changing across the initial range, one of the cases where a detection signal within the initial range is obtained three times is determined as one cycle of passage of the detection target,
A threshold setting method, comprising: setting a threshold based on a maximum value and a minimum value of the detection signal obtained during at least one cycle of passing the detection target. A detection unit that outputs a detection signal according to an external physical state,
An initial value acquisition unit that sets a predetermined range including a level of the detection signal obtained from the detection unit when the teaching start signal is input as an initial range,
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 obtained three times. A data comparison unit for determining a cycle,
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,
A detector configured to distinguish an output obtained from the detector based on a threshold set by the threshold setting processor. A threshold setting method in a detection device that sequentially detects a detection target that sequentially passes by comparing a detection signal according to an external physical state with a threshold, and outputs 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 an initial range,
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 obtained three times. Judge as a cycle,
A threshold setting method, comprising: setting a threshold based on a maximum value and a minimum value of the detection signal obtained during at least one cycle of passing the detection target. A detection unit that outputs a detection signal according to an external physical state,
An initial value acquisition unit that sets a predetermined range including a level of the detection signal obtained from the detection unit when the teaching start signal is input as an initial range,
After the detection signal has changed from the initial range, a detection signal within the initial range is obtained again, and a data comparing unit that determines that a change without crossing the initial range is 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,
A detector configured to distinguish an output obtained from the detector based on a threshold set by the threshold setting processor. A threshold setting method in a detection device that sequentially detects a detection target that sequentially passes by comparing a detection signal according to an external physical state with a threshold, and outputs 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 an initial range,
After the detection signal changes from the initial range, a detection signal within the initial range is obtained again, and a case where the detection signal changes without crossing the initial range is determined as one cycle of passage of the detection target, and at least one cycle of the detection target is detected. A threshold setting method, wherein a threshold is set based on a maximum value and a minimum value of the detection signal obtained during the passage. A detection unit that outputs a detection signal according to an external physical state at predetermined intervals,
A difference value calculation unit that calculates a difference value between detection signals for each detection signal obtained from the detection unit when a teaching start signal is input,
Cycle discrimination for holding the detection signal when the absolute value of the difference value obtained from the difference value calculation unit is within a predetermined range, and for discriminating one cycle of passing the detection target based on a change state of the absolute value of the difference value. Department and
A threshold setting processing unit that sets a threshold based on the detection signal held while the passage of the detection target in at least one cycle is determined by the cycle determination unit;
A detector configured to distinguish an output obtained from the detector based on a threshold set by the threshold setting processor. A threshold setting method in a detection device that sequentially detects a detection target that sequentially passes by comparing a detection signal according to an external physical state with a threshold, and outputs a detection result signal,
Sampling is performed every predetermined period after the teaching start signal is input, and
Calculate the difference value between the detection signals obtained for each sampling,
Holding the data of the detection signal when the absolute value of the difference value is within a predetermined range, determining one cycle of passing the detection target by the state of change of the absolute value of the difference value,
A threshold setting method, wherein the threshold is set based on a detection signal held during at least one cycle of passage of a detection target. A detection unit that outputs a detection signal according to an external physical state,
A differential value calculation unit that calculates a differential value of a detection signal for each detection signal obtained from the detection unit when a teaching start signal is input,
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 determines one cycle of passage of the detection target based on a state of a change in the absolute value of the differential value;
A threshold setting processing unit that sets a threshold based on the detection signal held during the passage of the detection target in at least one cycle by the cycle determination unit;
A detector configured to distinguish an output obtained from the detector based on a threshold set by the threshold setting processor. A threshold setting method in a detection device that sequentially detects a detection target that sequentially passes by comparing a detection signal according to an external physical state with a threshold, and outputs a detection result signal,
When the teaching start signal is input, sampling is performed intermittently.
Calculate the differential value of each detection signal obtained for each sampling,
Holding the data of the detection signal when the absolute value of the differential value is within a predetermined range,
One cycle of the detection object passage is determined based on the state of the change in the absolute value of the differential value,
A threshold setting method, wherein the threshold is set based on a detection signal held during at least one cycle of passage of a detection target. A detection unit that outputs a detection signal according to an external physical state at predetermined intervals,
A maximum value determination unit that determines a maximum value of a detection signal obtained from the detection unit when a teaching start signal is input;
A minimum value determination unit that determines a minimum value of a detection signal obtained from the detection unit when a teaching start signal is input;
A cycle determination unit that determines whether the detection signal obtained from the detection unit continuously updates the maximum value and the minimum value, and determines one cycle of the detection target passage when the update is not continuously performed a predetermined number of times;
A threshold setting processing unit that sets a threshold based on a maximum value and a minimum value obtained during the passage of the detection target in at least one cycle;
A detector configured to distinguish an output obtained from the detector based on a threshold set by the threshold setting processor. A threshold setting method in a detection device that sequentially detects a detection target that sequentially passes by comparing a detection signal according to an external physical state with a threshold, and outputs a detection result signal,
When the teaching start signal is input, sampling is performed every predetermined period,
Determine the maximum value of the detection signal obtained for each sampling,
Determine the minimum value of the detection signal obtained for each sampling,
Determine whether the detection signal obtained from the detection unit does not continuously update the maximum value and the minimum value,
When the update is not performed continuously for a predetermined number of times, one cycle of the detection target passage is determined,
A threshold setting method characterized in that a threshold is set based on a maximum value and a minimum value obtained during at least one cycle of passage.

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