WO2012005017A1

WO2012005017A1 - Object detection system

Info

Publication number: WO2012005017A1
Application number: PCT/JP2011/052119
Authority: WO
Inventors: 齋藤善胤; 錦戸憲治
Original assignee: 株式会社エニイワイヤ
Priority date: 2010-07-03
Filing date: 2011-02-02
Publication date: 2012-01-12
Also published as: CN103109206B; CN103109206A

Abstract

Provided is an object detection system that has a simple structure, is easy to set and adjust, and is capable of detecting various target objects that include specular reflectors and transparent bodies. The sum of a first detection level and a second detection level, which are acquired by a detection means for electromagnetic waves, magnetic fields or sound waves, or the first detection level value and the second detection level value are taken as a determination level value and an object is determined as present when the determination level value is greater than a first threshold value or when the the determination level value is less than the first threshold value and a second threshold value. Further, when the determination level value is greater than the second threshold value but does not meet the first threshold value and the difference between the first threshold value and the second threshold value is greater than a designated standard value, a target object is determined as present.

Description

Object detection system

The present invention relates to an object detection system that detects the presence / absence of a detection target using an electromagnetic wave, a magnetic field, or a reflection phenomenon of a sound wave.

The reflection type photoelectric sensor receives light emitted from the light projecting unit at the light receiving unit, and detects the presence or absence of a detection object by a change in the light receiving level. Among the reflection type photoelectric sensors, the light projecting unit The type that reflects the light emitted from the light by a reflecting part (reflector or the like) and reaches the light receiving part is called a regressive reflection type photoelectric sensor or the like.

The retroreflective photoelectric sensor is suitable for detecting a translucent object (hereinafter referred to as a transparent body), but has an object that reflects light (hereinafter referred to as a specular reflector). There was a problem that it was difficult to detect accurately. Therefore, attempts have been made to accurately detect a specular reflector using a retroreflective photoelectric sensor, and various proposals have been made. As such, there are, for example, a reflective photoelectric switch disclosed in Japanese Patent Laid-Open No. 61-203522, a retroreflective photoelectric switch disclosed in Japanese Patent Laid-Open No. 2-27632, and the like. In these photoelectric switches, by using the difference in the type of polarized light reaching the light receiving unit, it is possible to identify whether the reflected light is from the specular reflector or the reflected light from the reflective unit. The presence or absence of is detected.

Also, attempts have been made to deal with new products that have been distributed in recent years. For example, there is a retroreflective photoelectric sensor disclosed in Japanese Patent Application Laid-Open No. 2008-112629, which detects a PET bottle having a complex shape with high transmittance. According to this retroreflective photoelectric sensor, a light projecting system that projects circularly polarized light, and a light receiving system that selectively receives reverse circularly polarized light when mixed light of reverse circularly polarized light and circularly polarized light is incident. The sensor body formed of PET utilizes the birefringence of the PET bottle that has caused the malfunction, and converts the polarization state disturbance due to the birefringence into the attenuation of light. The bottle can be detected.

JP-A-61-203522 JP-A-2-27632 JP 2008-112629 A

However, as in the conventional photoelectric sensor, in order to use the difference in the type of polarization, it is difficult to adjust the optical axis, and a large number of filters and polarizing plates are required, which makes setting and adjustment difficult. was there.

Therefore, an object of the present invention is to provide an object detection system capable of detecting various detection objects including a specular reflector and a transparent body while having a simple configuration and being easy to set and adjust.

A first object detection system according to the present invention includes electromagnetic wave, magnetic field or sound wave generation means, first detection means, and second detection means. The angle formed by the detection axes of the first detection means and the second detection means becomes significant in the detection of the electromagnetic wave, the magnetic field, or the sound wave reflected by the detection target, and from the target region for determining the presence or absence of the detection target. The size of the electromagnetic wave, the magnetic field, or the acoustic wave that reaches the first detection unit or the second detection unit through a distant area is not affected. Then, the sum of the first detection level value by the first detection means and the second detection level value by the second detection means, or either the first detection level value or the second detection level value is determined. It is determined as a level value, and when the determination level value is larger than the first threshold value or smaller than the second threshold value smaller than the first threshold value, it is determined that the detection object is present. Further, when the determination level value is larger than the second threshold value and less than the first threshold value, and the difference between the first detection level value and the second detection level value is larger than a predetermined reference value, the detection object is Judge that there is.

A second object detection system according to the present invention includes first generation means, second generation means, and detection means for electromagnetic waves, magnetic fields, or sound waves generated by the first generation means and the second generation means. . Then, the detection level of the electromagnetic wave, magnetic field, or sound wave that reaches the detection unit through the target region for determining the presence or absence of the detection target from the first generation unit is set as a first detection level value, and the target from the second generation unit The detection level of the electromagnetic wave, magnetic field, or sound wave that reaches the detection means through a region is set as a second detection level value, or the sum of the first detection level value and the second detection level value, or the first detection level value and One of the second detection level values is set as a determination level value, and when the determination level value is larger than the first threshold value or smaller than the second threshold value smaller than the first threshold value, it is determined that there is a detection target. Further, when the determination level value is larger than the second threshold value and less than the first threshold value, and the difference between the first detection level value and the second detection level value is larger than a predetermined reference value, the detection object is Judge that there is.

In the second object detection system, a time-division detection level generated by receiving the electromagnetic wave, magnetic field or sound wave generated by the first generation unit is set as the first detection level value, and is generated by the second generation unit. Another time division light reception level generated by receiving the electromagnetic wave, magnetic field or sound wave may be used as the second detection level value.

In the first object detection system, a plurality of sets of the generation means, the first detection means, and the second detection means are installed, and each of the sets is connected to a common data signal line via a slave station. It may be what was done. In this case, a master station connected to the control unit is connected to the common data signal line. The master station has timing generation means for generating a predetermined timing signal synchronized with a transmission clock having a predetermined cycle, and according to the value of control data from the control unit under the control of the timing signal And outputting a series of pulse signals as control data signals to the common data signal line, and under the control of the timing signal, the series of pulse signals via the slave station for each cycle of the transmission clock. The data value of the detection data signal superimposed on is extracted and delivered to the control unit. Further, each of the slave stations extracts a value of each data of the control data signal under the control of the timing signal, and corresponds to the data corresponding to the own station in the value of each data. One generation means or the second generation means, and under the control of the timing signal, the detection data values of the first detection means and the second detection means corresponding to each cycle of the transmission clock. The corresponding detection data signal is superimposed on the series of pulse signals.

The second object detection system includes a plurality of sets of the first generation means, the second generation means, and the reception means, and each of the sets is connected to a common data signal line via a slave station. It may be what was done. In this case, a master station connected to the control unit is connected to the common data signal line. The master station has timing generation means for generating a predetermined timing signal synchronized with a transmission clock having a predetermined cycle, and according to the value of control data from the control unit under the control of the timing signal And outputting a series of pulse signals as control data signals to the common data signal line, and under the control of the timing signal, the series of pulse signals via the slave station for each cycle of the transmission clock. The data value of the detection data signal superimposed on is extracted and delivered to the control unit. Further, each of the slave stations extracts a value of each data of the control data signal under the control of the timing signal, and corresponds to the data corresponding to the own station in the value of each data. The detection data signal according to the value of the detection data of the corresponding detection means for each cycle of the transmission clock under the control of the timing signal, and delivered to one generation means or the second generation means, It is superimposed on the series of pulse signals.

In the first and second object detection systems, the first threshold value, the second threshold value, and the reference value may be transmitted via the common data signal line.

In the object detection system according to the present invention, the threshold level (the first threshold value or the second threshold value) is set on each of the detection level when the detection target is not present (the detection level when there is no detection object) and on the smaller side. In addition, two detection levels (first detection level value and second detection level value) obtained from two different detections are set as a set, and the difference between these levels is compared with a reference different from the above threshold value. By determining the presence / absence of the detection object, various detection objects including a specular reflector and a transparent body can be detected.

The detection level of the electromagnetic wave, magnetic field, or sound wave that reaches the detection means through the region where the detection target exists is, for example, a detection light beam in the order of specular reflector, reflector, transparent body, opaque body, and black body (non-reflector). The detection level changes step by step in accordance with the properties of the detection target so that the detection level decreases. However, there are two detection levels, one that is higher than the detection level when the detection target is not present (the detection level when no object is present) and one that is smaller than the detection level. In this case, it is impossible to determine the presence or absence of the detection target. On the other hand, in the present invention, since the detection level is compared with the threshold value (first threshold value or second threshold value) on each of the increase side and the decrease side with respect to the detection level in the absence, The presence / absence of the detection target can be determined from the detection level that changes step by step.

However, the condition for determining that there is an object to be detected is that it is greater than the first threshold value on the side that is greater than the detection level when there is no detection, and that it is less than the second threshold value on the side that is smaller than the detection level when there is no presence Therefore, when the detection level is a level between two threshold values, it is impossible to determine the presence or absence of the detection target. Therefore, two detection levels (first detection level value and second detection level value) obtained from two different detections are set as a set, and the difference between these levels is compared with the above threshold and a reference different from the above threshold. It is decided to determine whether there is any.

In the first object detection system, the two different detections are significant in the detection of the electromagnetic wave, magnetic field, or sound wave reflected by the detection target, with the angle formed by the detection axes of the first detection unit and the second detection unit. This can be achieved by setting the size so as not to affect the detection of the electromagnetic wave, magnetic field or sound wave that reaches the first detection means or the second detection means through a region away from the target region for determining the presence or absence of the detection target. In the second object detection system, the first generation means, the second generation means, and the electromagnetic wave, magnetic field, or sound wave detection means generated by the first generation means and the second generation means can be provided. .

In addition, in order to perform detection in a plurality of areas, when it is necessary to install a plurality of sets of generating means and detecting means side by side, under the control of a predetermined timing signal synchronized with a transmission clock of a predetermined period, A transmission method is preferable in which a control data signal and a detection data signal are exchanged for each cycle of the transmission clock according to the value of control data from the control unit. In this case, by obtaining the operation timing of the generating means for each cycle of the transmission clock, detection in a plurality of areas can be performed while preventing mutual interference between the generating means.

It is a graph which shows the time-dependent change of the judgment level value in the Example of the object detection system which concerns on this invention. It is a block diagram of the system. It is a functional block diagram of a control part and a master station. It is a functional block diagram of a slave station. It is a system block diagram of a slave station. The detection principle of a sensor part is shown typically, (a) is an enlarged plan view in the vicinity of the target area when there is a detection target, and (b) is a plan view when there is no detection target. It is a graph which shows the relationship between the distance from a light projection part to the reflective point of the light ray for a detection, and a detection level value. It is a program flowchart of a master station. It is a time chart which shows typically the basic signal of the transmission clock signal at the time of parameter transmission. It is a time chart which shows typically the basic signal of the transmission clock signal at the time of detection data transmission. It is an input / output processing program flowchart of a slave station. It is a detection processing program flowchart of a slave station. 6 is a flowchart of a slave station determination processing program. It is a table which shows the parameter memorized by a child station. It is a time chart which shows the signal produced | generated in a slave station in contrast with a transmission clock signal. The detection principle of the sensor part in the other Example of the object detection system which concerns on this invention is shown typically, (a) is an enlarged plan view of the object area | region vicinity in case there exists a detection target object, (b) is a detection target object. It is a top view when there is no.

An embodiment of the object detection system according to the present invention will be described with reference to the drawings.
As shown in FIG. 2, this object detection system detects the presence or absence of a transported object on a conveyor 7 as a detection object 6, and includes a plurality of sensor units 4 arranged along the moving direction of the conveyor 7. I have. Each of the sensor units 4 is connected to the common data signal lines DP and DN via the corresponding slave stations 5, and the master station 2 connected to the control unit 1 is also connected to the common data signal lines DP and DN. Has been.

The control unit 1 is, for example, a programmable controller, a computer, and the like, and includes an output unit 11 that transmits control data 13 for the sensor unit 4 and an input unit 12 that receives monitoring data 14 as a detection result in the sensor unit 4. The master station 2 is connected to the output unit 11 and the input unit 12.

As shown in FIG. 3, the master station 2 includes an output data unit 22, a timing generator 23, a master station output unit 24, a master station input unit 25, and an input data unit 26. The parallel data received as control data 13 from the output unit 11 of the control unit 1 is connected to the common data signal lines DP and DN, and is sent to the common data signal lines DP and DN as control signals. 4 is converted into parallel data and sent as monitoring data 14 to the input unit 12 of the control unit 1. Here, the control signals sent to the common data signal lines DP and DN correspond to a series of pulse signals in the present invention, but hereinafter, control signals flowing through the common data signal lines DP and DN are transmitted. This is called a clock signal.

The output data unit 22 delivers the parallel data received as the control data 13 from the output unit 11 of the control unit 1 to the master station output unit 24 as serial data.

The timing generation unit 23 includes an oscillation circuit (OSC) 31, a master station address setting unit 32, and a timing generation unit 33. Based on the OSC 31, the timing generation unit 33 generates a timing clock of this system and generates a master station output unit 24. To hand over.

The master station output unit 24 includes a control data generation unit 34 and a line driver 35. Based on the data received from the output data unit 22 and the timing clock received from the timing generation unit 23, a common data signal is transmitted via the line driver 35. A transmission clock signal is sent as a series of pulse signals to the lines DP and DN.

The data value (control data) of the transmission clock signal transmitted from the master station output unit 24 to the common data signal lines DP and DN is expressed by the pulse width of a period with a high voltage level in one cycle of the transmission clock signal. As shown in FIG. 9, the transmission clock signal has a high potential level (+ 24V in this embodiment) in the second half of one cycle and a low potential level (0V or + 12V in this embodiment) in the first half. The width of the high potential level is expanded according to the value of each data of the control data 13 input from the control unit 1, and in this embodiment, the width shown by the broken line in FIG. 9, that is, 1 of the transmission clock signal. When the period is t0, the period is extended to (3/4) t0. However, the width is not limited and may be adjusted as appropriate according to transmission conditions and the like. In addition, an address is assigned for each cycle of the transmission clock signal, and the slave station 5 described later takes in control data to be received by the local station by a method of counting this address. A start signal (StartBit) and an end signal (not shown) are formed at the beginning and end of the transmission clock signal in order to determine the beginning and the end for counting addresses. The start signal is a signal having the same potential level as the high potential level of the transmission clock signal and longer than one cycle of the transmission clock signal. On the other hand, the end signal is the same level as the low potential level of the transmission clock signal and is longer than one cycle of the transmission clock signal and shorter than the start signal. This end signal is formed at the time point when it matches the address assigned to the master station 2 held in the master station address setting means 32.

The master station input unit 25 includes a detection data signal detection unit 36 and a detection data extraction unit 37, and transmits an input data signal to the input data unit 26. The detection data signal detection means 36 detects a detection data signal sent from the slave station 5 via the common data signal lines DP and DN. The data value of the detection data signal transmitted from the slave station 5 is represented by the voltage level of the first half (period of low potential level) of one cycle in the transmission clock signal. After the start signal is transmitted, the slave station Each of 5 is received sequentially. Data (detection data) of the detection data signal is extracted by the detection data extraction unit 37 in synchronization with the signal of the timing generation unit 33 and sent to the input data unit 26 as a serial input data signal. The input data unit 26 converts the serial input data signal received from the master station input unit 25 into parallel data, and sends it as monitoring data 14 to the input unit 12 of the control unit 1.

As shown in FIG. 6, the sensor unit 4 includes a generating unit 41 having two light projecting units 41a and 41b for emitting a detection light beam, a detection unit 42 having a light receiving unit 42a for receiving the detection light beam, and a detection light beam. Reflection means 43. The reflection means 43 is disposed opposite to the generation means 41 and the detection means 42 with the target region 3 for determining the presence or absence of the detection target 6 interposed therebetween, and constitutes a regressive reflection type sensor. In this embodiment, the predetermined transport distance range on the conveyor 7 is the target area 3.

The generation means 41 and the detection means 42 are connected to the slave station 5, and the slave station 5 includes a microcomputer control unit (MCU) 51, an address setting means 52, and an A / D converter 53 as shown in FIG. Is provided. As shown in FIGS. 4 and 5, the MCU 51 includes a CPU, a RAM, and a ROM, and a program (PRG) necessary for detection processing is stored in the ROM. Then, detection data, parameters, and address data are stored in the RAM, and processing for obtaining information necessary for detection is performed using the arithmetic function of the CPU. The light projecting sections 41a and 41b of the generating means 41 are connected to the output terminals La and Lb of the MCU 51, and the light projecting timing is controlled. On the other hand, the detection level value of the light receiving unit 42 a of the detection unit 42 is input from the input terminal ADAT to the MCU 51 via the A / D converter 53.

The MCU 51 also receives the address information set by the address setting means 52 from the input terminal ADRS, and the divided signal obtained by dividing the potential difference between the common data signal lines DP and DN by the dividing resistors R1 and R2. Is input from the input terminal CK. Further, an out signal for transmitting the detection data signal to the common data signal lines DP and DN is output from the output terminal OUT, and an enable signal en for the A / D converter 53 is output from the output terminal EN. The contents of processing in this MCU 51 will be described later.

Next, the detection principle of the sensor unit 4 will be described. As shown in FIG. 6A, the detection light beams projected by the light projecting portions 41a and 41b reach different parts of the detection target 6, and are reflected there. The reflected light from the detection object 6 is the strongest when the angle (reflection angle) with respect to the reflection surface (the surface of the detection object 6) is equal to the incident angle (reflected light D in FIG. 6A). As the value increases, it becomes weaker. Specifically, in the case of FIG. 6A, the reflected light from the light projecting unit 41b to the light receiving unit 42a is the strongest when the reflection angle A1 is 0, and becomes weaker as the reflection angle A1 becomes larger. The reflected light from 41a to the light receiving unit 42a is the strongest when the reflection angle A2 is equal to the incident angle A0, and becomes weaker as the reflection angle A2 increases. On the other hand, as the point where the detection light beam is reflected (referred to as a reflection point) is further away from the light receiving unit 42a, the reflection angle of the reflected light from the reflection point to the light receiving unit 42a becomes larger and weaker. Specifically, in the case of FIG. 6A, the reflection angle A1 of the reflected light from the light projecting unit 41b to the light receiving unit 42a is larger than the reflection angle A2 of the reflected light from the light projecting unit 41a to the light receiving unit 42a. Thus, the detection light beam from the light projecting unit 41a to the light receiving unit 42a is stronger than that from the light projecting unit 41b. Accordingly, the detection levels of the detection light beams projected by the light projecting units 41a and 41b, reflected from the surface of the detection target 6 and reaching the light receiving unit 42a are those from the light projecting unit 41a and those from the light projecting unit 41b. Then it will be different.

Further, as shown in FIG. 6B, the detection light beam projected from each of the light projecting portions 41a and 41b when there is no detection target 6 reaches the reflection means 43 and is reflected there. At this time, the reflecting unit 43 is arranged at a sufficient distance from the projecting unit 41 so that the difference between the angles of the optical axes of the projecting unit 41a and the projecting unit 41b is negligible. The detection level of the detection light beam projected from the light parts 41a and 41b and reflected by the reflecting means 43 to reach the light receiving part 42a is not different between the light level from the light projecting part 41a and the light level from the light projecting part 41b. This phenomenon will be described with reference to FIG. FIG. 7 is a graph showing the relationship between the detection level and the distance from the light projecting units 41a and 41b to the reflection point of the detection light beam. As an input value to the MCU 51 of the slave station 5, a detection level value (first detection level value) Pana input from the input terminal ADAT upon receiving a detection light beam from the light projecting unit 41 a, and a detection value from the light projecting unit 41 b A detection level value (second detection level value) Panb, a sum (Pana + Panb), and a difference (Pana−Panb) of the detection level value (second detection level value) received from the input terminal ADAT upon receiving the light beam are detected from the light projecting units 41a and 41b. The distance to the reflection point of the light beam changes as shown in FIG. However, in FIG. 7, the change in the detection level value is emphasized in order to facilitate understanding of the detection principle, and the relationship between the value itself and the distance is not accurate.

On the other hand, the detection level of the detection light beam projected from the light projecting units 41a and 41b and reflected from the surface of the detection target 6 to reach the light receiving unit 42a is that of the light projecting unit 41a and that of the light projecting unit 41b. In any case, it changes stepwise according to the properties of the detection object 6. Specifically, the detection level when the detection target 6 is a specular reflector is large, and the detection level when the detection target 6 is a non-reflector that hardly reflects the detection light beam is extremely low, and the detection light beam can be transmitted. In the case of a transparent body, the detection level is between these detection levels. Furthermore, since the detection light beam when there is no detection object 6 is reflected by the reflecting means 43 and reaches the light receiving unit 42a, the detection level (detection level when absent) is higher than that when the detection object 6 is a transparent body. Will also be big. Therefore, first, the first threshold value S1 smaller than the detection level of the specular reflector is provided on the side larger than the detection level in the absence, and the second threshold value S2 larger than the detection level of the transparent body is provided on the smaller side. The presence / absence of the detection target 6 can be determined by comparing the threshold value with the detection level.

The total change (Pana + Panb) of the first detection level value and the second detection level value is taken as a judgment level value, and the change with time is shown in FIG. In FIG. 1, time t <b> 1 is when the detection target 6 has entered the target area 3, and time t <b> 2 is when the detection target 6 has left the target area 3. Therefore, the determination level value (Pana + Panb) changes according to the property of the detection target object 6 between time t1 and time t2. Since the judgment level value P1 of the solid line is larger than the first threshold value S1, it can be seen that the specular reflector is present in the target region 3 as the detection target 6. Further, since the imaginary line judgment level values P2 and P3 are smaller than the second threshold value S2 in any case, it can be seen that a transparent body or a non-reflecting body is present in the target area 3 as the detection target 6.

However, when the detection target 6 is a reflector that makes a reflection that is smaller than the specular reflector and larger than the transparent body, the determination level value is the first threshold value S1 and the second threshold value S2. It is not possible to judge the presence or absence. Therefore, in this case, a determination is made based on the difference between the first detection level value and the second detection level value. As described above, when the detection target 6 is in the target region 3, the first detection level value and the second detection level value are different, so that the difference is larger than a predetermined reference value considering an error. In this case, it is determined that the first detection level value and the second detection level value are different, and it can be determined that the detection target 6 is present.

In addition, since the tendency which changes in steps according to the property of the detection target object 6 is the same for both the first detection level value and the second detection level value, the determination level value to be compared with the first threshold value and the second threshold value is Only one of the first detection level value and the second detection level value may be used.

Next, processing contents executed in the master station 2 and the slave station 5 of this object detection system will be described with reference to a flowchart.
In the master station 2, as shown in FIG. 8, when the power is turned on and the program is started (S1) and the initial process (S2) is completed, it is determined whether or not there is a parameter change (S3). As will be described later, this parameter is an identification given to a plurality of sets of the first threshold value, the second threshold value, and a reference value (a value to be compared with the difference between the first detection level value and the second detection level value). Number. In this object detection system, by appropriately changing these parameters, it is possible to adapt to the case where the conveyed item on the conveyor 7 changes and the property of the detection target 6 changes.

If there is a parameter change, the start signal in the transmission clock signal is made long (S4), and the slave station 5 can recognize that the parameter value is transmitted. As will be described later, the short start signal causes the slave station 5 to recognize that the detection data is transmitted.

When the long start signal is transmitted, the address in the transmission clock signal is incremented thereafter (S5), and a parameter (see FIG. 9) obtained by modulating the pulse width of the transmission clock signal corresponding to the address is set to each channel CH. Data is transmitted (S6). The channel CH is an identification number assigned to each of the sensor units 4.

When the transmission of the parameter data is completed, a short start signal is subsequently sent (S7), and reception of the detection data is started. If there is no change in the parameter, that is, if it is determined that there is no parameter in step S3, the process proceeds from step S3 to step S7.

The slave station 5 that has recognized that the transmission clock signal transmits the detection data by the short start signal modulates the voltage level of the first half of one cycle in the pulse of the address corresponding to the local station in the transmission clock signal as described above. Then, the detection data signal is superimposed on the transmission clock signal (broken line in FIG. 10). Therefore, in the master station 2, when a start signal having a short transmission clock signal is transmitted, the address in the transmission clock signal is subsequently incremented (S8), and detection data superimposed on the pulse of the transmission clock signal corresponding to the address is detected. Is received (S9). Then, the process returns to step S1 to repeat the above series of processing.

The slave station 5 is based on processing mainly for data input / output (input / output processing), processing for obtaining information necessary for detection of the detection target 6 (detection processing), and information obtained by the detection processing. Processing for determining the presence or absence of the detection target 6 (determination processing) is performed. The flowchart in FIG. 11 shows data input / output processing, the flowchart in FIG. 12 shows detection processing, and the flowchart in FIG. 13 shows determination processing.

As the first process in the slave station 5, the input / output process shown in FIG. 11 is performed. In this process, first, the power is turned on and the program is started (S21). When the initial process (S22) is completed, it is determined whether or not the start signal of the transmission clock signal is a long start signal (S23). If it is a long start signal, the local station address set by the address setting means 52 is read (S24). Then, the address of the transmission clock signal is obtained by counting the period of the transmission clock signal, and the address is compared with the local station address (S25). If it is the address of the own station, the data at that time is received as parameter data (S26). For each parameter data, constants used for the determination, that is, Kun (first threshold value), Kdn (second threshold value), Kcn (reference value) are defined in advance, and each slave station 5 is shown in FIG. Stored as a table. Then, the slave station 5 that has received the parameter data stores constants (Kun, Kdn, Kcn) corresponding to the parameter data in the RAM of the MCU 51 (S27). Although the parameter data of this embodiment has four types in 2-bit expression, the number is not limited and may be changed as appropriate. On the other hand, if it is not the address of the own station, the cycle is counted until the address of the own station is reached, and the address is incremented (S28).

When Kun, Kdn, and Kcn are stored, the process returns to step S23, and the determination as to whether the signal is a long start signal is repeated. If it is not a long start signal, it is subsequently determined whether it is a short start signal (S29). If it is not a short start signal, the same determination is repeated until it becomes a short start signal. If it is a short start signal, the local station address set by the address setting means 52 is read (S30). Subsequently, the address of the transmission clock signal is obtained by counting the period of the transmission clock signal, and the address is compared with the local station address (S31). If it is the address of its own station, a signal corresponding to the detection data stored in the RAM of the MCU 51 at that time is output from the output terminal OUT to the base of the transistor TR. Specifically, if the detection data is on (indicating that the detection target 6 is present), the transistor TR is turned on, the current flows, the voltage drops, the voltage level becomes 0V, and the signal is It is transmitted on the common data signal lines DP and DN. That is, as shown in FIG. 10, the voltage of the low voltage period in one cycle of the transmission clock signal is sent out as a detection data signal on the common data signal lines DP and DN in a form that is lowered as shown by a broken line. . (S33). On the other hand, if it is not the address of the own station, the cycle is counted until the address of the own station is reached, and the address is incremented (S32).

After sending the detection data, the detection process is performed next. In this processing, first, the light projecting unit 41a is turned on. When the light projecting unit 41a is turned on, the output terminal La of the MCU 51 is set to “on” (S41). Since the processing in the slave station 5 is common to all sensor units 4, that is, all channels (CH), the CH number is represented by n in FIGS. Therefore, Lan in step S41 means the output terminal La at CHn.

The timing at which the output terminal La is turned “on” in step S41 can be obtained from the transmission clock signal. That is, when the slave station 5 corresponding to the sensor unit 4 of each channel receives the address assigned to the local station in the transmission clock signal, the slave unit 5 transmits the light of the light projecting units 41a and 41b in the local station from the pulse signal of the address. Get light timing. For example, in the example shown in FIG. 15, since the first period following the short start signal and the next one period are allocated to CH1, the start of the first period (falling of the short start signal) is performed by CH1. The light projecting timing of the light unit 41a (the timing when La1 is turned “on”) and the start of the next cycle are the light projecting timing of the light projecting unit 41b of CH1 (the timing when Lb1 is turned “on”). The same applies to the light projecting timing of the CH2 light projecting unit 41a (the timing when La2 is "on") and the light projecting timing of the CH2 light projecting unit 41b (the timing when Lb2 is "on"). Thus, by obtaining the light projection timing from each pulse of the transmission clock signal, the light projecting unit 41a and the light projecting unit 41b can be operated without causing mutual interference. Similarly, when viewed as the sensor unit 4, the sensor units 4 can be operated without causing the sensor units 4 to interfere with each other.

When the light projecting unit 41a is turned on and a detection light beam is projected, a detection level signal is output from the light receiving unit 42a that has received the detection light beam, and AD conversion of the signal is started (S42). Note that Pana in step S42 means data based on the detection level signal of the light receiving unit 42a that has received the detection light beam from the light projecting unit 41a in CHn, and corresponds to the first detection level value of the present invention.

When a predetermined time elapses after the light emitting unit 41a is turned on, the output terminal EN of the MCU 51 is set to “on” (S43), the enable signal en is output, and data is read from the input terminal ADAT (S44). ). Then, the read data is stored in the RAM as a first detection level value (Pana) (S45).

When the first detection level value is stored, the output terminal Lan is set to “off” (S46), the light projecting unit 41a is turned off, and the output terminal EN is set to “off” (S47). Then, 1 is added to the own station address (S48). Note that, in the method of counting the addresses, it is determined by the addition in step S48 that the next cycle pulse also corresponds to the own station. However, the determination is not essential in this detection process, and the description is omitted.

After the detection process using the light projecting unit 41a (from step S41 to step S48) is completed, the detection process using the light projecting unit 41b is performed. This process is the same as the detection process using the light projecting unit 41a. First, the output terminal Lb of the MCU 51 is set to “on” (S51), and the light projecting unit 41b is turned on. When the light projecting unit 41b is turned on, a detection level signal is output from the light receiving unit 42a that has received the detection light beam, and AD conversion of the signal is started (S52). When a predetermined time elapses after the light emitting unit 41b is turned on, the output terminal EN of the MCU 51 is set to “on” (S53), the enable signal en is output, and data is read from the input terminal ADAT (S54). . Then, the read data is stored in the RAM as the second detection level value (Panb) (S55). When the second detection level value is stored, the output terminal Lbn is set to “off” (S56), the light projecting unit 41b is turned off, the output terminal EN is set to “off” (S57), and the detection process ends.

In the above detection processing, the first detection level value and the second detection level value are projected from each of the two light projecting units 41a and 41b by appropriately switching between “on” and “off” of the output terminal EN. The detected light beam is obtained as a distinguished detection level value without confusion. The detection level value thus obtained is the time-division detection level of the present invention.

When the detection process is completed, the determination process shown in FIG. 13 is performed using the obtained first detection level value (Pana) and second detection level value (Panb). In this process, first, the sum of Pana and Panb is used as a judgment level value and compared with the first threshold (Kun) (S61). If it is larger than Kun, it is determined that the detection target 6 exists, the detection data is set to “on” (S65), and the determination process ends. If it is smaller than Kun, then it is compared with the second threshold (Kdn) (S62). If it is smaller than Kdn, it is determined that there is the detection object 6, the detection data is set to “on” (S65), and the determination process ends. If it is larger than Kdn, the difference between Pana and Panb is subsequently compared with a reference value (Kcn) (S63). If it is larger than Kcn, it is determined that the detection target 6 exists, the detection data is set to “on” (S65), and the determination process ends. If it is smaller than Kcn, it is determined that there is no detection object 6, the detection data is set to "off" (S64), and the determination process ends.

After completion of the determination process, the process returns to step S23 of the input / output process, and the same process is repeated. The detection data determined in step S64 or step S65 of the determination process is sent to the common data signal lines DP and DN in step S33 of the input / output process.

In this embodiment, the light projecting means 41 is provided with two light projecting parts 41a and 41b, and the light receiving means 42 is provided with a single light receiving part 42a. Even if two are used, the same detection can be performed. FIG. 16 schematically shows the detection principle in that case. Note that, in FIG. 16, the same reference numerals are given to components that are essentially the same as the detection principle illustrated in FIG. 6.

As shown in FIG. 16A, the detection light beam projected by the light projecting unit 41a reaches the detection object 6 and is reflected there. The reflected light at this time is reflected on the reflection surface (detection object 6). When the angle (reflection angle) with respect to the surface of the light is equal to the incident angle (reflected light D in FIG. 16A) is the strongest, and becomes weaker as the reflection angle increases. On the other hand, the farther the light receiving unit 42a or 42b is from the point where the detection light beam is reflected (referred to as a reflection point), the greater the reflection angle of the reflected light reaching them, and the weaker it becomes. In the case of FIG. 16A, the reflection angle A1 of the reflected light Da from the light projecting unit 41a to the light receiving unit 42a is smaller than the reflection angle A2 of the reflected light Db from the light projecting unit 41a to the light receiving unit 42b. The detection light beam from the light projecting unit 41a to the light receiving unit 42a is stronger than that from the light receiving unit 42b. Therefore, the detection level of the detection light beam that is projected by the light projecting unit 41a and reflected by the surface of the detection target 6 and reaches the light receiving unit 42a is different from the detection level of the detection light beam that reaches the light projecting unit 41b. Detection can be performed in the same manner as in the embodiment shown in FIGS.

In this embodiment, since each of the light receiving parts 42a and 42b performs different detection, it is not necessary to time-divide the detection level as in the sensor part 4 shown in FIG. Further, since the light projecting means 41 is only a single light projecting unit 41a, the light projecting timing is also single. Therefore, only one cycle of pulses in the transmission clock signal allocated to each channel is required.

DESCRIPTION OF SYMBOLS 1 Control part 2 Master station 3 Target area 4 Sensor part 5 Slave station 6 Detection target 7 Conveyor 11 Output unit 12 Input unit 13 Control data 14 Monitoring data 22 Output data part 23 Timing generation part 24 Parent station output part 25 Parent station input Unit 26 input data unit 32 timing generation unit 33 master station address setting unit 34 control data generation unit 35 line driver 36 detection data signal detection unit 37 detection data extraction unit 41 generation unit 41a, 41b light projecting unit 42 detection unit 42a, 42b light reception Part 43 Reflecting means 51 MCU
52 Address setting means 53 A / D converter DP, DN Common data signal line R1, R2 Resistor TR Transistor

Claims

An electromagnetic wave, a magnetic field, or a sound wave generating means, a first detecting means, and a second detecting means are provided, and an angle formed by the detection axes of the first detecting means and the second detecting means is reflected by a detection object. Detection of the electromagnetic wave, magnetic field, or sound wave that becomes significant in the detection of the electromagnetic wave, magnetic field, or sound wave, and that reaches the first detection means or the second detection means through a region away from the target region for determining the presence or absence of the detection object The size has no effect on
The sum of the first detection level value by the first detection means and the second detection level value by the second detection means, or a determination level value for either the first detection level value or the second detection level value And when the determination level value is larger than the first threshold value or smaller than the second threshold value smaller than the first threshold value, it is determined that the detection object is present,
The detection object is present when the determination level value is greater than the second threshold value and less than the first threshold value, and the difference between the first detection level value and the second detection level value is greater than a predetermined reference value. An object detection system characterized by judging.
A first generating means; a second generating means; and an electromagnetic wave, magnetic field or sound wave detecting means generated by the first generating means and the second generating means,
The detection level of the electromagnetic wave, magnetic field, or sound wave that reaches the detection unit through the target region for determining the presence or absence of the detection target from the first generation unit is set as a first detection level value, and the target region is determined from the second generation unit. The detection level of the electromagnetic wave, magnetic field or sound wave that reaches the detection means via the second detection level value,
The sum of the first detection level value and the second detection level value or one of the first detection level value and the second detection level value is set as a determination level value, and the determination level value is larger than the first threshold value. Or when it is smaller than the second threshold smaller than the first threshold,
The detection object is present when the determination level value is greater than the second threshold value and less than the first threshold value, and the difference between the first detection level value and the second detection level value is greater than a predetermined reference value. An object detection system characterized by judging.
The time division detection level generated by receiving the electromagnetic wave, magnetic field or sound wave generated by the first generation means is set as the first detection level value, and the electromagnetic wave, magnetic field or sound wave generated by the second generation means is The object detection system according to claim 2, wherein the second detection level value is another time-division detection level generated in response.
A plurality of sets of the generating means, the first detecting means, and the second detecting means are installed, and each of the sets is connected to a common data signal line via a slave station,
A master station connected to the control unit is connected to the common data signal line,
The master station has timing generation means for generating a predetermined timing signal synchronized with a transmission clock having a predetermined cycle, and according to the value of control data from the control unit under the control of the timing signal And outputting a series of pulse signals as control data signals to the common data signal line, and under the control of the timing signal, the series of pulse signals via the slave station for each cycle of the transmission clock. The data value of the detection data signal superimposed on is extracted and delivered to the control unit,
Each of the slave stations extracts the value of each data of the control data signal under the control of the timing signal, and sends the data corresponding to the own station in the value of each data to the corresponding generation unit. Under the control of the delivery and the timing signal, the detection data signal corresponding to the value of the detection data of the first detection means and the second detection means corresponding to each cycle of the transmission clock is sent to the series. The object detection system according to claim 1, wherein the object detection system is superimposed on the pulse signal.
A plurality of sets of the first generating means, the second generating means, and the receiving means are installed, and each of the sets is connected to a common data signal line via a slave station,
A master station connected to the control unit is connected to the common data signal line,
The master station has timing generation means for generating a predetermined timing signal synchronized with a transmission clock having a predetermined cycle, and according to the value of control data from the control unit under the control of the timing signal And outputting a series of pulse signals as control data signals to the common data signal line, and under the control of the timing signal, the series of pulse signals via the slave station for each cycle of the transmission clock. The data value of the detection data signal superimposed on is extracted and delivered to the control unit,
Each of the slave stations extracts the value of each data of the control data signal under the control of the timing signal, and the first generation corresponding to the data corresponding to the own station in the value of each data The detection data signal corresponding to the value of the detection data of the detection means corresponding to each cycle of the transmission clock under the control of the timing signal. The object detection system according to claim 2 or 3, wherein the object detection system is superimposed on the pulse signal.
The object detection system according to claim 4 or 5, wherein the first threshold value, the second threshold value, and the reference value are transmitted via the common data signal line.