JP7035890B2 - Photoelectric sensor - Google Patents

Description

The present invention relates to a photoelectric sensor having a function of determining the state of an object.

Conventionally, as a sensor for detecting the presence or absence of an object, the object is irradiated with light to detect the light transmitted through the object, the shielding of light by the object is detected, and the light reflected by the object is detected. A photoelectric sensor is used. Further, when detecting the state of the object instead of the presence or absence of the object, a visual sensor that captures the object with a camera and performs image analysis may be used.

Regarding the photoelectric sensor, for example, in the following Patent Document 1, by storing the detection value corresponding to the background level as the zero reset reference value, any detection value can be displayed as a relative value with respect to the background level. The configured photoelectric sensor is described.

Further, in Patent Document 2 below, the surface of a steel sheet is scanned with a laser beam, a plurality of feature quantities representing reflected light waveforms are calculated, and the feature quantities are added to a neural network in which the feature quantities are learned in advance. The inspection method to perform no output is described.

Japanese Unexamined Patent Publication No. 2001-124594 Japanese Unexamined Patent Publication No. 2-298840

It is more difficult than the detection of the presence or absence of an object that can be done with one popular photoelectric sensor, but it is larger and more expensive than a photoelectric sensor. There is detection demand. For example, when distinguishing objects having greatly different shapes and patterns, it is not enough to simply detect the presence or absence of the object, but it is not enough to require various capabilities of a visual sensor.

Here, it is considered that the state of the object can be determined in principle by combining the conventional photoelectric sensor and the method of analyzing the received light amount waveform as shown in Patent Document 1. However, since an appropriate trigger for acquiring only the waveform of the portion necessary for determination (the portion corresponding to the size of the flaw in Patent Document 2) cannot be obtained, the waveform in a longer time range than the portion necessary for determination is not obtained. Waveform analysis is performed after the acquisition of the above is completed, and for example, it lacks real-time performance in order to apply it to an object that is carried one after another on a transport line.

Therefore, the present invention provides a photoelectric sensor that has a simple configuration, has a small time delay, and determines the state of an object.

The photoelectric sensor according to one aspect of the present disclosure has acquired a light projecting unit that emits light toward a detection range in which an object arrives, and a light receiving unit that acquires a time-series signal value based on the light reception. It is composed of a FIFO memory that stores a predetermined number of signal values in order and periodically updates a predetermined number of signal values with newly acquired signal values, and a predetermined number of signal values stored in the FIFO memory. A model storage unit that stores a judgment model that determines the rank of the degree of coincidence between the waveform and the reference waveform corresponding to a specific state of the object, and the frequency of once each time the FIFO memory is updated once or multiple times. The determination unit is provided with a determination unit that executes determination by the determination model and determines the state of the object based on the rank of the degree of coincidence.

According to this aspect, a waveform composed of signal values stored in the FIFO memory and a reference waveform corresponding to a specific state of the object are used once or once for each update of the FIFO memory. By determining the rank of the degree of coincidence with, it is possible to determine the state of the object being carried one after another on the transport line with a simple configuration and with little time delay.

In the above aspect, the determination model may be a trained model generated by machine learning.

According to this aspect, the trained model determines the rank of the degree of coincidence between the waveform composed of the signal values stored in the FIFO memory and the reference waveform corresponding to the specific state of the object. It is possible to more flexibly determine the state of the object being carried on the line one after another.

In the above embodiment, the determination model includes calculating the degree of agreement from the difference between a predetermined number of signal values stored in the FIFO memory and a reference value representing a reference waveform corresponding to each of the predetermined number of signal values. May be.

According to this aspect, a relatively simple model is used to determine the rank of the degree of agreement between the waveform composed of the signal values stored in the FIFO memory and the reference waveform corresponding to the specific state of the object. , The state of the object being carried one after another on the transport line can be determined at higher speed.

In the above aspect, the determination model is a model that determines that the degree of coincidence is high rank when the degree of coincidence is higher than a predetermined value, and the determination unit is a target when the determination result of the high rank is obtained. The state of the object may be determined to be a specific state.

In the above aspect, the determination model is a model for determining that the degree of agreement is medium rank when the degree of agreement is not higher than the predetermined value but higher than the second predetermined value smaller than the predetermined value. , Even if it is determined that an object that is not in a specific state has arrived when the object is not in the high rank but in the middle rank within the time required for the object to pass through the detection range. good.

According to this aspect, even when the state of the object is not a specific state, it can be determined that the object has arrived and that the state of the object is not a specific state.

In the above embodiment, an operation control unit that generates a determination model based on the signal value and stores the generated determination model in the model storage unit may be further provided.

According to this aspect, since the photoelectric sensor can generate the determination model by itself, the determination model generated according to the actual object can be used without acquiring the determination model from the outside.

In the above embodiment, the motion control unit is a signal belonging to the fluctuation period when a fluctuation period in which the fluctuation of the time-series signal value is relatively large appears following a stable period in which the fluctuation of the time-series signal value is relatively small. A judgment model may be generated based on the value.

According to this aspect, the determination model can be generated by selectively using the signal value generated by the object from the signal values.

In the above aspect, the motion control unit may be able to output the determination model to the outside.

According to this aspect, since the generated determination model can be used in another photoelectric sensor, it is not necessary to repeat the generation of the determination model for each of a plurality of photoelectric sensors used in the same object and installation situation.

In the above aspect, the operation control unit may be able to output a time-series signal value to the outside.

According to this aspect, the signal value can be output to the outside and the determination model can be generated by the external device. This eliminates the need for the photoelectric sensor itself to have computational resources related to the process of generating the determination model.

In the above aspect, the motion control unit may acquire the determination model from the outside and store it in the model storage unit.

According to this aspect, the generation of the determination model can be omitted by diverting the determination model generated by another device, for example, another photoelectric sensor.

According to the present invention, there is provided a photoelectric sensor that determines the state of an object with a simple configuration and with little time delay.

It is a figure which shows the outline of the detection system including the photoelectric sensor which concerns on embodiment of this invention. It is a figure which shows the structure of the photoelectric sensor which concerns on this embodiment. It is a figure which shows an example of the structure of the processing part of the photoelectric sensor which concerns on this embodiment. It is a flowchart of the process of the learning mode and the determination mode of the photoelectric sensor which concerns on this embodiment. It is a flowchart of 1st example of the process of determining the state of an object by the photoelectric sensor which concerns on this embodiment. It is a flowchart of the 2nd example of the process of determining the state of an object by the photoelectric sensor which concerns on this embodiment. It is a figure which shows an example of the signal value measured in the nth cycle of the photoelectric sensor which concerns on this embodiment. It is a figure which shows an example of the signal value measured in the n + 1th cycle of the photoelectric sensor which concerns on this embodiment. It is a figure which shows the other example of the signal value measured in the nth cycle of the photoelectric sensor which concerns on this embodiment. It is a figure which shows the other example of the structure of the processing part of the photoelectric sensor which concerns on this embodiment. It is a figure which shows the example which installs the determination model from the outside to the photoelectric sensor which concerns on this embodiment.

Hereinafter, embodiments according to one aspect of the present invention (hereinafter, referred to as “the present embodiment”) will be described with reference to the drawings. In each figure, those with the same reference numerals have the same or similar configurations.

[Configuration example]
An example of the configuration of the photoelectric sensor 10 according to the present embodiment will be described with reference to FIGS. 1 to 3. FIG. 1 is a diagram showing an outline of a detection system 1 including a photoelectric sensor 10 according to the present embodiment. The detection system 1 includes a photoelectric sensor 10, a controller 20, a computer 30, a robot 40, and a transfer device 50.

The photoelectric sensor 10 is a device that detects that the object 100 has arrived in the detection range 10a of the photoelectric sensor 10 based on the acquired signal value, and determines the state of the object 100. The photoelectric sensor 10 may be a reflective photoelectric sensor, a transmissive photoelectric sensor, or a retroreflective photoelectric sensor. Further, the photoelectric sensor 10 may be a displacement sensor that projects a laser beam onto the object 100 and obtains a signal value corresponding to the distance to the object 100 based on the principle of triangular distance measurement. Further, the photoelectric sensor 10 may be a distance measuring sensor that obtains a signal value corresponding to the distance to the object 100 based on the round-trip time of the light reflected by the object 100. In the present specification, the "signal value" includes not only the value of the received light amount but also the signal value corresponding to the distance to the object 100.

The object 100 is an object to be detected by the photoelectric sensor 10, and may be, for example, a finished product of a product to be produced or an unfinished product such as a part. The object 100 exemplified in FIG. 1 is an object having a protrusion on the base. Further, as different kinds of objects, objects having the same base but having a shape without protrusions are also mixed and transported. When the photoelectric sensor 10 is, for example, a reflection type photoelectric sensor, the amount of reflected light detected increases when the object 100 reaches the detection range 10a of the photoelectric sensor 10. Further, when the object 100 has a protrusion on the base, the amount of reflected light further increases if the object 100 has a protrusion in the detection range 10a.

The controller 20 controls the robot 40 and the transfer device 50. The controller 20 may be configured by, for example, a PLC (Programmable Logic Controller). The controller 20 detects that the object 100 has arrived by the output from the photoelectric sensor 10, and further controls the robot 40 according to the determined state of the object 100.

The computer 30 sets the photoelectric sensor 10, the controller 20, and the robot 40. Further, the computer 30 acquires the execution result of the control by the controller 20 from the controller 20. Further, the computer 30 may include a learning device that generates a determination model for determining the state of the object 100 by the photoelectric sensor 10 by machine learning. Here, the determination model may be composed of, for example, a neural network or a decision tree.

The robot 40 operates and processes the object 100 according to the control by the controller 20. The robot 40 may, for example, pick up the object 100 and move it to another place, cut the object 100, or assemble it. Further, the robot 40 may change the processing content or the moving destination depending on whether or not the object 100 has a protrusion.

The transport device 50 is a device that transports the object 100 under the control of the controller 20. The transport device 50 may be, for example, a belt conveyor, and may transport the object 100 at a speed set by the controller 20.

FIG. 2 is a diagram showing the configuration of the photoelectric sensor 10 according to the present embodiment. The photoelectric sensor 10 includes a light projecting unit 11, a light receiving unit 12, a processing unit 13, an operation unit 14, and an output unit 15.

<Light projector>
The light projecting unit 11 emits light toward the detection range 10a where the object 100 arrives. The light projecting unit 11 may include a light projecting element 11a and a drive circuit 11b. The light emitting element 11a may be composed of an LED (Light Emitting Diode) or a laser diode, and the drive circuit 11b controls a current for causing the light emitting element 11a to emit light. The drive circuit 11b may intermittently cause the light projecting element 11a to emit light in pulses, for example, at a period of 0.1 ms. The light emitted from the light projecting element 11a may be applied to the detection range 10a via a lens or an optical fiber (not shown).

<Light receiving part>
The light receiving unit 12 acquires a time-series signal value based on the light reception. The light receiving unit 12 may include a light receiving element 12a, an amplifier 12b, a sample / hold circuit 12c, and an A / D converter 12d. The light receiving element 12a may be composed of a photodiode, and converts a light receiving amount into an electrical output signal. The light receiving unit 12 may make the light reflected or transmitted in the detection range 10a incident on the light receiving element 12a via a lens or an optical fiber (not shown). The amplifier 12b amplifies the output signal of the light receiving element 12a. The sample / hold circuit 12c holds the output signal of the light receiving element 12a amplified by the amplifier 12b in synchronization with the timing of the pulse emission by the light projecting unit 11. This reduces the influence of ambient light. The A / D converter 12d converts the analog signal value held by the sample / hold circuit 12c into a light receiving amount value which is a digital value.

<Processing unit>
The processing unit 13 includes an operation control unit 13a, a FIFO (First In First Out) memory 13b, a model storage unit 13c, and a determination unit 13d. The processing unit 13 may be configured as, for example, a computer composed of a microprocessor, a memory, a program stored in the memory, and the like.

The motion control unit 13a may collectively control the motion of the entire photoelectric sensor 10 in addition to the process of handling the determination model described later.

The FIFO memory 13b stores a predetermined number of signal values in order of acquisition, and periodically updates the predetermined number of signal values with the newly acquired signal values. Here, the number of signal values stored in the FIFO memory 13b, that is, a predetermined number is arbitrary, but may be, for example, about 100. The FIFO memory 13b can be realized by dedicated hardware, or may be realized on the memory of the processing unit 13 according to the program of the processing unit 13. In that case, the shift of the signal value to the subsequent stage of the FIFO memory 13b can be performed by updating the access point on the memory, not by physically shifting the stored data.

The model storage unit 13c stores a determination model for determining the rank of the degree of coincidence between the waveform composed of a predetermined number of signal values stored in the FIFO memory 13b and the reference waveform corresponding to the specific state of the object 100. do. Here, the reference waveform may be a waveform having a typical signal value corresponding to a specific state of the object 100, and is, for example, an average of waveforms acquired for a plurality of objects 100 in the specific state. good.

The model storage unit 13c may store the trained model generated by machine learning as the determination model. The trained model is trained to determine the rank of the degree of coincidence between the waveform composed of a predetermined number of signal values stored in the FIFO memory 13b and the reference waveform corresponding to a specific state of the object 100. good. Here, the trained model may be generated by the computer 30 and stored in the model storage unit 13c.

The determination unit 13d executes the determination by the determination model once every time the FIFO memory 13b is updated once or a plurality of times, and the waveform is composed of a predetermined number of signal values stored in the FIFO memory 13b. , The state of the object 100 is determined based on the rank of the degree of coincidence with the reference waveform corresponding to the specific state of the object 100. For example, when the reference waveform is the waveform of an object having a protrusion on the base, the determination unit 13d executes the determination by the determination model, and when the degree of coincidence is sufficiently high, the object 100 has a protrusion on the base. It may be determined that the state is marked with. In this way, the waveform composed of the signal values stored in the FIFO memory 13b and the reference corresponding to the specific state of the object 100 at a frequency of once for each update of the FIFO memory 13b once or a plurality of times. By determining the rank of the degree of coincidence with the waveform, it is possible to determine the state of the object 100 being carried one after another on the transport line with a simple configuration and with little time delay. This makes it possible to determine the state of the object 100 with a simple configuration similar to that of a popular photoelectric sensor, that is, without the need for image processing or a separate triggering means, with little time delay.

The determination model is a model including calculating the degree of agreement from the difference between a predetermined number of signal values stored in the FIFO memory 13b and a reference value representing a reference waveform corresponding to each of the predetermined number of signal values. It's okay.

The determination model may be a model that determines that the degree of coincidence is high rank when the degree of coincidence is higher than a predetermined value, and the determination unit 13d may determine the object 100 when a high rank determination result is obtained. The state of may be determined to be a specific state. When the high rank determination result is obtained, the determination unit 13d may maintain the output that the state of the object 100 is a specific state for a predetermined period even after the high rank determination result disappears. Here, the predetermined period may be about the time required for the object 100 to pass through the detection range 10a. The determination unit 13d may determine the state of the object 100 a plurality of times within the time range required for the object 100 to pass through the detection range 10a. Here, the "range of time required for the object 100 to pass through the detection range 10a" may be incorporated into the determination model as the duration of the signal value fluctuation measured at the time of generation of the determination model. Further, during the determination operation, the determination result obtained from the present to the past by the number of shifts corresponding to the duration is "time required to pass through the detection range 10a" without detecting the start of the signal value fluctuation. It may be "range of". It is also conceivable to set the period from the detection of the start of the signal value fluctuation to the shift of the number of times corresponding to the duration as the "range of time required to pass through the detection range 10a". As described above, within the time required for the object 100 to pass through the detection range 10a, the waveform composed of the signal values stored in the FIFO memory 13b and the reference corresponding to the specific state of the object 100. It is possible to determine whether or not the rank of the degree of coincidence with the waveform may be higher than the predetermined value.

The determination model may be a model that further determines that the degree of agreement is medium rank when the degree of agreement is not higher than the predetermined value but higher than the second predetermined value smaller than the predetermined value, and the determination unit 13d may be used. Within the time required for the object 100 to pass through the detection range 10a, it may be determined that an object that is not in a specific state has arrived when there is a case of a medium rank and there is a case of a high rank. The determination unit 13d determines the state of the object 100 a plurality of times within the time required for the object 100 to pass through the detection range 10a, and the determination result is not high in any of the plurality of determinations. , If the determination result is the middle rank at least once out of a plurality of determinations, it may be determined that an object that is not in a specific state has arrived. The second predetermined value is a value larger than zero. The second predetermined value may be a threshold value determined based on the signal value when the object 100, which is not in a specific state, reaches the detection range 10a. Thereby, even if the state of the object 100 is not a specific state, it can be determined that the object 100 has arrived and that the state of the object 100 is not a specific state. For example, when a specific state is a state in which a protrusion is attached to a base, and an object having only a base without a protrusion arrives, the determination unit 13d may determine that the degree of matching is medium rank.

The determination unit 13d may adjust the signal value magnification in consideration of the deterioration of the amount of light due to the dirt on the window or the like, and determine whether or not the degree of coincidence is sufficiently high. That is, the determination unit 13d has a higher degree of coincidence between the waveform obtained by changing the magnification of the waveform composed of the signal values stored in the FIFO memory 13b and the reference waveform corresponding to the specific state of the object 100. The state of the object 100 may be determined depending on whether or not the object 100 is present. By doing so, even when the amount of light projected or the amount of received light changes due to dirt on the window or the like, the state of the object 100 can be stably determined.

Further, when a plurality of types of objects are mixed and conveyed, the determination model has a waveform composed of signal values stored in the FIFO memory 13b and a reference waveform corresponding to a specific state of the object 100 of any type. It may be a model that determines that the degree of agreement is high when the degree of agreement with is higher than a predetermined value. Further, when the degree of matching is high rank or medium rank, the determination unit 13d is determined to be high rank or medium rank by indicating which type of object the determination result is for the determination model itself. The type of the object 100 may be specified. Alternatively, the determination model is prepared for each type of the object 100, and the determination unit 13d identifies the type of the object 100 determined to be high rank or medium rank depending on which determination model determines the high rank or medium rank. You may.

For example, when the first-class object and the second-class object are mixed and conveyed, the determination unit 13d uses the waveform composed of the acquired signal values and the reference corresponding to the first-class object. When the degree of coincidence with the waveform is high, it may be determined that the state of the transported object is a specific state of the first type object. Further, the determination unit 13d is a state of the object being conveyed when the degree of coincidence between the waveform composed of the acquired signal values and the reference waveform corresponding to the second type object is high. May determine that it is a specific state of the second type object. Further, the determination unit 13d does not determine a high rank for any of the objects, and the degree of coincidence between the waveform composed of the acquired signal values and the reference waveform corresponding to the first type object is medium. In the case of rank, it may be determined that the transported object is a first-class object that is not in a specific state. Further, the determination unit 13d does not determine a high rank for any of the objects, and the degree of coincidence between the waveform composed of the acquired signal values and the reference waveform corresponding to the second type object is medium. In the case of rank, it may be determined that the state of the transported object is a second-class object that is not a specific state. If the first type object and the second type object are similar, or if the second predetermined value for determining the middle rank is a low value, it is composed of the acquired signal values. The degree of coincidence between the waveform to be performed and the reference waveform corresponding to the first type object and the degree of coincidence with the reference waveform corresponding to the second type object may both result in a medium rank determination result. sell. In such a case, the determination unit 13d indicates that the object being transported is a type 1 object that is not in a specific state or a type 2 object that is not in a specific state, and either object. It may be determined that it cannot be specified.

<Operation unit>
The operation unit 14 is for operating the photoelectric sensor 10, and may include an operation switch, a display, and the like. The operator of the photoelectric sensor 10 can use the operation unit 14 to input instructions such as setting the operation mode of the photoelectric sensor 10 and confirm the operating state. The photoelectric sensor 10 according to the present embodiment has, as an operation mode, a learning mode for generating a determination model and a determination mode for determining the state of the object 100 using the generated determination model. good.

<Output section>
The output unit 15 outputs various data including the determination result by the determination unit 13d. The output unit 15 may most simply output a binary value of the determination result by the determination unit 13d. The photoelectric sensor 10 may be provided with a communication unit instead of the output unit 15 so that a large amount of data can be input / output.

FIG. 3 is a diagram showing an example of the configuration of the processing unit 13 of the photoelectric sensor 10 according to the present embodiment. In the first cycle, the processing unit 13 shifts the signal value stored in each stage of the FIFO memory 13b to the stage one behind, and converts the digital value of the received light output from the A / D converter 12d into the digital value. Store in the first stage q0. In the figure, in order to explain the principle, the number of stages of the FIFO memory 13b is set to 10 stages of q0 to q9, but the number of stages of the FIFO memory 13b may be further increased, for example, about 100 stages. ..

The first cycle for updating the FIFO memory 13b may be the same as or different from the cycle of pulse emission by the light projecting unit 11. Further, the first cycle for updating the FIFO memory 13b may be the same as or different from the pulse emission of the light projecting unit 11 and the conversion cycle by the A / D converter 12d (referred to as the second cycle). May be. For example, the second period may be fixed to a value peculiar to the photoelectric sensor 10 (for example, 0.1 ms). The first cycle may be set from the computer 30 shown in FIG. 1 via the controller 20. The first period needs to be determined so that the range of the signal value waveform to be processed at the same time is within the FIFO memory 13b. The first cycle is often longer than the second cycle, and may be, for example, 1 ms.

The determination unit 13d determines the rank of the degree of coincidence between the waveform composed of the signal values stored in the plurality of stages of the FIFO memory 13b and the reference waveform corresponding to the specific state of the object by the determination model. The state of the object is determined based on the rank of the degree of coincidence, and the determination result is output to the operation control unit 13a in the first cycle.

As the determination model, the model storage unit 13c may store a trained model generated by machine learning and determining the rank of the degree of matching. Here, the determination model may be configured by, for example, a neural network or a decision tree, and may include a trained model generated by another known machine learning method. The determination unit 13d may execute the determination by the trained model once every time the FIFO memory 13b is updated once or a plurality of times, and determine the state of the object based on the rank of the degree of agreement. ..

The operation control unit 13a generates a determination model based on the signal value, and stores the generated determination model in the model storage unit 13c. For example, the motion control unit 13a may execute machine learning of the learning model based on the acquired signal value, generate a trained model, and store the generated trained model in the model storage unit 13c. In this way, the motion control unit 13a can generate the determination model. That is, since the photoelectric sensor can generate the determination model by itself, the determination model generated according to the actual object can be used without acquiring the determination model from the outside.

The motion control unit 13a may be able to output the determination model to the outside. As a result, the generated determination model can be used in another photoelectric sensor, so that it is not necessary to repeat the generation of the determination model for each of a plurality of photoelectric sensors used in the same object and installation situation. Therefore, it is possible to efficiently prepare a photoelectric sensor that determines the state of the object.

The operation control unit 13a is based on the signal value belonging to the fluctuation period when the fluctuation period in which the fluctuation of the time-series signal value is relatively large appears after the stable period in which the fluctuation of the time-series signal value is relatively small. You may generate a judgment model. Here, the stable period in which the fluctuation of the signal value in the time series is relatively small may be a period in which the fluctuation of the signal value in the time series is substantially free when the influence of noise is subtracted. Further, the fluctuation period in which the fluctuation of the signal value in the time series is relatively large may be a period in which the fluctuation of the signal value in the time series is substantially present when the influence of noise is subtracted. In this way, by generating the determination model based on the signal values belonging to the fluctuation period, the determination model can be generated by selectively using the signal value generated by the object from the signal values. Specific examples of a stable period in which the fluctuation of the signal value in the time series is relatively small and a fluctuation period in which the fluctuation of the signal value in the time series is relatively large will be described with reference to FIGS. 7a and 7b.

FIG. 4 is a flowchart of processing of the learning mode and the determination mode of the photoelectric sensor 10 according to the present embodiment. First, the photoelectric sensor 10 determines whether or not it is in the learning mode for generating the determination model (S10). The learning mode and the determination mode may be switched by the operation unit 14.

When the photoelectric sensor 10 is in the learning mode (S10: YES), the photoelectric sensor 10 acquires a time-series signal value, and the motion control unit 13a generates a determination model (S11).

On the other hand, when the photoelectric sensor 10 is not in the learning mode (S10: NO), that is, when the photoelectric sensor 10 is in the determination mode, the photoelectric sensor 10 updates the FIFO memory 13b with a new signal value (S12) and shifts to the FIFO memory 13b. By applying the determination model to the stored signal value, the state of the object is determined (S13). Here, the determination process (S13) will be described in more detail with reference to FIGS. 5 and 6.

After that, the photoelectric sensor 10 determines whether or not to terminate the determination mode (S14). The end of the determination mode may occur when the operation of the photoelectric sensor 10 is terminated or when the determination mode is switched to the learning mode. When the determination mode is not terminated (S14: NO), the photoelectric sensor 10 acquires the time-series signal value again (S12), and applies the determination model to the acquired signal value to determine the state of the object. Judgment (S13). On the other hand, when the determination mode is terminated (S14: YES), the processing of the learning mode and the determination mode is terminated.

FIG. 5 is a flowchart of a first example of a process (S13) for determining the state of an object by the photoelectric sensor 10 according to the present embodiment. First, the photoelectric sensor 10 determines the rank of the degree of coincidence between the waveform composed of the acquired signal values and the reference waveform by the determination model (S131). The rank of the degree of coincidence may be represented by discrete values such as "high rank", "medium rank", and "low rank".

When the degree of coincidence is high (S132: YES), the photoelectric sensor 10 determines that the state of the object is a specific state corresponding to the reference waveform (S133). On the other hand, when the degree of coincidence is not high rank (S132: NO), the photoelectric sensor 10 ends the determination process and determines whether or not the degree of coincidence is high rank again at the time of determination of the next cycle. This completes the first example of the determination process.

FIG. 6 is a flowchart of a second example of the process (S13) for determining the state of the object by the photoelectric sensor 10 according to the present embodiment. First, the photoelectric sensor 10 determines the rank of the degree of coincidence between the waveform composed of the acquired signal values and the reference waveform by the determination model (S134).

When the determined degree of coincidence is high rank (S135: YES), the photoelectric sensor 10 determines that the state of the object is a specific state corresponding to the reference waveform (S136). On the other hand, when the degree of matching is not high rank (S135: NO) and the degree of matching is determined to be medium rank (S137: YES), the photoelectric sensor 10 determines the state of the object without immediately determining the state. End the process.

The degree of matching is not high rank (S135: NO), the degree of matching is not medium rank (S137: NO), and there is no case where the degree of matching is high rank within the time range in which the object passes through the detection range. Moreover, when it is determined that there is a case of middle rank (S138: YES), the photoelectric sensor 10 determines that an object which is not in a specific state has arrived (S139). On the other hand, even if the degree of matching is not high rank (S135: NO) and the degree of matching is not medium rank (S137: YES), the degree of matching is high within the time range in which the object passes through the detection range. If there is no case and it is not determined that there is a case of middle rank (S138: NO), the determination process is terminated.

In order to determine whether the degree of coincidence is not high-ranked and medium-ranked within the time range in which the object passes through the detection range (S138), the photoelectric sensor 10 is used from the present time to the past. A series of determination results in which the rank of the degree of coincidence is determined by the determination model within the time required for the object to pass through the detection range may be stored in a FIFO memory (not shown) for storing the determination results. Further, the photoelectric sensor 10 does not store a series of determination results in the FIFO memory, and when the determination model determines that the degree of coincidence is medium rank, the photoelectric sensor 10 measures the time required for the object to pass through the detection range. If a high-ranked judgment result does not appear by the end of the timekeeping, it is judged that an object that is not in a specific state has arrived, and if a high-ranked judgment result appears by the end of the timekeeping. , It may be determined that an object in a specific state has arrived. This completes the second example of the determination process.

FIG. 7a is a diagram showing an example of signal values measured in the nth cycle of the photoelectric sensor 10 according to the present embodiment. Further, FIG. 7b is a diagram showing an example of signal values measured in the n + 1 cycle of the photoelectric sensor 10 according to the present embodiment. In FIGS. 7a and 7b, the vertical axis shows the value of the light receiving amount, and the horizontal axis shows the time and the corresponding stage of the FIFO memory 13b. As shown in both figures, the latest received light amount value (time t9 value) is stored in the first stage q0 of the FIFO memory 13b, and the oldest received light amount value (time t0 value) is the FIFO memory. It is stored in the final stage q9 of 13b. In this example, the FIFO memory 13b stores 10 signal values in order of acquisition.

The shape S1 of the object shown by the broken line schematically shows the shape of the object according to the timing at which the value of each light receiving amount is obtained. According to the shape S1 of the object, it can be read that the object has a shape with protrusions on the base.

The waveform W1 shown by the solid line in FIG. 7a is a waveform composed of signal values acquired in the nth cycle and stored in the FIFO memory 13b. Further, the waveform W2 shown by the solid line in FIG. 7b is a waveform composed of signal values acquired in the n + 1 cycle and stored in the FIFO memory 13b. As shown in both figures, the signal value stored in the FIFO memory 13b in the nth cycle is shifted to the next stage by one in the n + 1 cycle and stored in the FIFO memory 13b.

Since the detection range 10a has a certain spread, the reflected light from both the upper surface and the lower surface of the step is received near the timing corresponding to the step of the object 100, and the signal values constituting the waveform W1 and the waveform W2 are It is an intermediate value. The value of the amount of received light in the middle tends to fluctuate greatly with a slight difference in acquisition timing. Therefore, the value of the light receiving amount may fluctuate every time even for the object 100 having the same shape. In generating the determination model, it is preferable to transport the object 100 a certain number of times and repeat the acquisition of the value of the received light amount so that the effect of averaging can be obtained.

The operation control unit 13a is based on the signal value belonging to the fluctuation period when the fluctuation period in which the fluctuation of the time-series signal value is relatively large appears after the stable period in which the fluctuation of the time-series signal value is relatively small. You may generate a judgment model. In the case of the example of FIG. 7a, the stable period in which the fluctuation of the signal value in the time series is relatively small is from time t0 to t1, and the fluctuation period in which the fluctuation of the signal value in the time series is relatively large is from time t2 to t8. Is. Further, in the case of the example of FIG. 7b, the stable period in which the fluctuation of the signal value in the time series is relatively small is after time t8, and the fluctuation period in which the fluctuation of the signal value in the time series is relatively large is from time t2 to t7. Is. The operation control unit 13a compares the values stored in the adjacent stages from the final stage to the first stage of the FIFO memory 13b, and when there is an adjacent stage whose difference is equal to or larger than the threshold value, the operation control unit 13a of the adjacent stages It is determined that the signal values belonging to the variable period are stored from the stage closer to the first stage to the first stage, and the signals belonging to the stable period from the stage closer to the final stage among the adjacent stages to the final stage. It may be determined that the value is stored. Specifically, in the case of the example of FIG. 7a, the motion control unit 13a compares the values stored in the final stage q9 and the eighth stage q8, and the difference is 0, which is equal to or less than the threshold value. The values stored in the 7th stage q8 and the 7th stage q7 may be compared, and it may be determined that the difference is 2 and is equal to or larger than the threshold value. Here, the threshold value may be, for example, 1. Then, the motion control unit 13a belongs to the variable period from the 7th stage q7 on the side closer to the first stage q0 of the 8th stage q8 and the 7th stage q7 where the difference between the stored values is equal to or larger than the threshold value toward the first stage q0. It is determined that the signal value is stored, and the signal value belonging to the stable period is stored from the 8th stage q8 on the side closer to the final stage of the 8th stage q8 and the 7th stage q7 toward the final stage q9. May be determined.

The determination unit 13d has a waveform W1 composed of a predetermined number of signal values stored in the FIFO memory 13b at a frequency of once each time the FIFO memory 13b is updated once or a plurality of times, and a specific object 100. The degree of agreement with the reference waveform corresponding to the state may be determined by the determination model, and the state of the object may be determined based on the rank of the degree of agreement. For example, when the reference waveform has a waveform substantially equal to the shape S1 of the object shown by the broken line in FIG. 7a, the determination unit 13d sets the signal value stored in each stage of the FIFO memory 13b and the signal value of the reference waveform. The sum of the absolute values of the differences may be obtained, and it may be determined whether the state of the object is a specific state, assuming that the smaller the value, the higher the degree of coincidence. As described above, when the photoelectric sensor 10 is operating in the determination mode and the conveyed object 100 is an object having protrusions, the amount of received light received in a specific shift cycle of the FIFO memory 13b The degree of matching between the waveform composed of the values and the reference waveform composed of the values of the amount of received light at the time of model generation is increased.

FIG. 8 is a diagram showing another example of the signal value measured in the nth cycle of the photoelectric sensor 10 according to the present embodiment. In the figure, the vertical axis shows the value of the light receiving amount, and the horizontal axis shows the time and the corresponding stage of the FIFO memory 13b.

The waveform W3 shown by the solid line in FIG. 8 is a waveform composed of signal values acquired in the nth cycle and stored in the FIFO memory 13b. Further, the shape S2 of the object shown by the broken line schematically shows the shape of the object according to the timing at which the value of each light receiving amount is obtained. According to the shape S2 of the object, it can be read that the object has only the shape of the base without protrusions.

Comparing the waveform W3 with the waveform W1 shown in FIG. 7a, there is a difference in the value of the received light amount between the times t4 and t6. When the object to be conveyed is an object without protrusions when operating in the determination mode, the received light received in some shift cycles of the FIFO memory 13b within the time required to pass the object. The degree of agreement between the waveform composed of the quantity values and the reference waveform composed of the received light quantity values at the time of generating the judgment model is larger than the second predetermined value and is medium, but if it is higher than the predetermined value. No, it will not be high. Therefore, although the determination unit 13d is not an object having protrusions, it may be determined that an object having some commonality with the object having protrusions has arrived because the degree of coincidence may be medium. .. In this example, since the base part of the object is common, the degree of agreement is medium.

FIG. 9 is a diagram showing another example of the configuration of the processing unit 13 of the photoelectric sensor 10 according to the present embodiment. The example of the configuration of the processing unit 13 shown in FIG. 3 is different from the example of the configuration of the processing unit 13 shown in FIG. 3 in that the reference value R is stored in the model storage unit 13c, and other than that. Common to the configuration.

As a determination model, the model storage unit 13c calculates the degree of coincidence from the difference between the predetermined number of signal values stored in the FIFO memory 13b and the reference value R representing the reference waveform corresponding to the predetermined number of signal values. You may memorize the model. In the case of this example, the model for calculating the degree of coincidence calculates the sum of the absolute values of the differences between the five reference values R and the signal values stored in the stages q0 to q4 of the FIFO memory corresponding to them. , The model may be a model that calculates the degree of coincidence so that the smaller the value is, the larger the degree of coincidence is. Reference values r4, r3, r2, r1 and r0 are stored in the model storage unit 13c, and may correspond to the values stored in q0, q2, q4, q6 and q8 of the FIFO memory 13b, respectively.

The determination model provided in the determination unit 13d obtains the absolute value of the difference between the corresponding values, and sets the sum of the absolute values of the differences to be smaller than the first threshold value as the first criterion, and matches when the first criterion is satisfied. It may be a model that determines that the degree is high. The determination model included in the determination unit 13d further sets that the sum of the absolute values of the differences is between the first threshold value and the second threshold value larger than the first threshold value, and passes the object 100. Within the time required, the model may be a model that determines that the degree of agreement is medium rank when the second criterion may be satisfied but the first criterion is not satisfied.

The determination unit 13d may execute the determination by the determination model once every time the FIFO memory 13b is updated once or a plurality of times, and determine the state of the object based on the rank of the degree of agreement. In this way, by using a relatively simple model, the degree of coincidence between the waveform composed of the signal values stored in the FIFO memory 13b and the reference waveform corresponding to the specific state of the object 100 is determined, and the transfer is performed. It is possible to determine the state of the object 100 carried on the line one after another at a higher speed.

The determination unit 13d determines the state of the object 100 a plurality of times within the time required for the object 100 to pass through the detection range 10a, and determines a predetermined number of signal values stored in the FIFO memory 13b and a predetermined number of signal values. The state of the object 100 is in a specific state when the first criterion for determining that the difference from the predetermined number of reference values R representing the reference waveform corresponding to each of the signal values of the numbers is small is satisfied at least once. It may be determined that there is. For example, the determination unit 13d corresponds to a predetermined number of signal values stored in the FIFO memory 13b and a predetermined number of signal values within a range of time required for the object 100 to pass through the detection range 10a. When the first criterion for determining that the difference from the predetermined number of reference values R representing the reference waveform is small is satisfied at least once, it is determined that the object 100 is an object having a protrusion on the base. good. As described above, within the time required for the object 100 to pass through the detection range 10a, the waveform composed of the signal values stored in the FIFO memory 13b and the reference corresponding to the specific state of the object 100. It is possible to determine whether or not the degree of coincidence with the waveform may be higher than a predetermined value.

Further, the determination unit 13d determines the state of the object 100 a plurality of times within the time required for the object 100 to pass through the detection range 10a, and does not satisfy the first criterion in all of the plurality of determinations. , The first for determining that the difference between the predetermined number of signal values stored in the FIFO memory 13b and the predetermined number of reference values R representing the reference waveform corresponding to the predetermined number of signal values is moderate. When the two criteria are satisfied at least once, it may be determined that the object 100 which is not in a specific state has arrived. For example, the determination unit 13d has a predetermined number of signal values stored in the FIFO memory 13b and a predetermined number of reference values R representing a reference waveform within the time range required for the object 100 to pass through the detection range 10a. If the first criterion for determining that the difference is small is not met, but the second criterion for determining that the difference is moderate is met at least once, the object 100 has no protrusions and only the base. It may be determined that the object has the shape of. In this way, even when the state of the object 100 is not a specific state, it can be determined that the object 100 has arrived and that the state of the object 100 is not a specific state.

FIG. 10 is a diagram showing an example of installing a determination model from the outside on the photoelectric sensor 10 according to the present embodiment. In the example of the configuration of the processing unit 13 of the photoelectric sensor 10 shown in the figure, the operation control unit 13a outputs the value of the received light amount in time series to the outside as compared with the example of the configuration of the processing unit 13 shown in FIG. However, the difference is that a determination model generated by an external computer is input based on the input, and the input determination model is stored in the model storage unit 13c, and the other configurations are common.

The operation control unit 13a may be able to output a time-series signal value to the outside. The signal value output to the outside may be a signal value stored in the FIFO memory 13b. The signal value can be output to the outside and a judgment model can be generated by an external device. This eliminates the need for the photoelectric sensor itself to have computational resources related to the process of generating the determination model.

The motion control unit 13a may acquire the determination model from the outside and store it in the model storage unit 13c. The motion control unit 13a may acquire a determination model generated by an external computer, or may acquire a determination model generated by another photoelectric sensor. By diverting the determination model generated by another device, for example, another photoelectric sensor, the generation of the determination model can be omitted.

The operation control unit 13a does not output the time-series signal value to the outside, but is external based on the model generated by the other photoelectric sensor or the time-series signal value acquired by the other photoelectric sensor. You may enter and use a computer-generated model.

The embodiments described above are for facilitating the understanding of the present invention, and are not for limiting the interpretation of the present invention. Each element included in the embodiment and its arrangement, material, condition, shape, size, and the like are not limited to those exemplified, and can be appropriately changed. Further, it is possible to partially replace or combine the configurations shown in different embodiments.

[Appendix]
A light projecting unit (11) that emits light toward the detection range (10a) where the object (100) arrives, and
A light receiving unit (12) that acquires a time-series signal value based on the light reception, and a light receiving unit (12).
A FIFO memory (13b) that stores a predetermined number of the signal values in order of acquisition and periodically updates the predetermined number of the signal values with the newly acquired signal values.
A determination model for determining the rank of the degree of coincidence between the waveform composed of the predetermined number of the signal values stored in the FIFO memory (13b) and the reference waveform corresponding to the specific state of the object (100). The model storage unit (13c) to be stored and
The determination by the determination model is executed once every time the FIFO memory (13b) is updated once or a plurality of times, and the state of the object (100) is determined based on the rank of the degree of agreement. Judgment unit (13d)
A photoelectric sensor (10).

1 ... Detection system, 10 ... Photoelectric sensor, 10a ... Detection range, 11 ... Floodlight, 11a ... Floodlight element, 11b ... Drive circuit, 12 ... Light receiving unit, 12a ... Light receiving element, 12b ... Amplifier, 12c ... Sample / Hold circuit, 12d ... A / D converter, 13 ... Processing unit, 13a ... Operation control unit, 13b ... FIFA memory, 13c ... Model storage unit, 13d ... Judgment unit, 14 ... Operation unit, 15 ... Output unit, 20 ... Controller, 30 ... computer, 40 ... robot, 50 ... transfer device, 100 ... object

Claims (10)

A light projecting unit that emits light toward the detection range where the object arrives,
A light receiving unit that acquires a time-series signal value based on the light reception, and a light receiving unit.
A FIFO memory that stores a predetermined number of the signal values in order of acquisition and periodically updates a predetermined number of the signal values with the newly acquired signal values.
A model storage unit that stores a determination model for determining the rank of the degree of coincidence between a waveform composed of a predetermined number of signal values stored in the FIFO memory and a reference waveform corresponding to a specific state of the object. ,
A determination unit that executes determination by the determination model once or once each time the FIFO memory is updated, and determines the state of the object based on the rank of the degree of agreement.
Equipped with
The reference waveform is generated based on the waveforms acquired for the plurality of objects in the specific state.
The rank of the degree of agreement is determined based on the comparison between the degree of agreement and a predetermined value, and is a photoelectric sensor. The determination model is a trained model generated by machine learning.
The photoelectric sensor according to claim 1. The determination model calculates the degree of agreement from the difference between the predetermined number of signal values stored in the FIFO memory and the reference value representing the reference waveform corresponding to the predetermined number of signal values. It is a model that includes
The photoelectric sensor according to claim 1. The determination model is a model for determining that the degree of agreement is high when the degree of agreement is higher than a predetermined value.
When the high-ranked determination result is obtained, the determination unit determines that the state of the object is the specific state.
The photoelectric sensor according to any one of claims 1 to 3. The determination model is a model for determining that the degree of agreement is medium rank when the degree of agreement is not higher than the predetermined value but higher than the second predetermined value smaller than the predetermined value.
The determination unit is not in the specific state when the object is not in the high rank but in the middle rank within the time required for the object to pass through the detection range. Judges that has arrived,
The photoelectric sensor according to claim 4. An operation control unit that generates the determination model based on the signal value and stores the generated determination model in the model storage unit is further provided.
The photoelectric sensor according to any one of claims 1 to 5. The operation control unit belongs to the fluctuation period when a fluctuation period in which the fluctuation of the signal value in the time series is relatively large appears following a stable period in which the fluctuation of the signal value in the time series is relatively small. Generate the determination model based on the signal value,
The photoelectric sensor according to claim 6. The motion control unit can output the determination model to the outside.
The photoelectric sensor according to claim 6 or 7. The operation control unit can output the time-series signal value to the outside.
The photoelectric sensor according to claim 6 or 7. An operation control unit that acquires the determination model from the outside and stores it in the model storage unit is further provided.
The photoelectric sensor according to any one of claims 1 to 5.

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