JP2005070847A - Sensor system and sensor unit thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sensor system and a sensor unit thereof capable of accurately receiving data even if deviation occurs between each sensor unit in an embedded clock operation. <P>SOLUTION: A CPU 15 starts counting of time based on a clock pulse of an own clock oscillator (S11), and reads a data signal D2 when the time Ts (reference time) is counted (step S15) unless a rising edge is not detected ('Y' in S12). On the other hand, when the rising edge is detected ('N' in the step S12), time difference α between detection timing of the rising edge (hereafter 'actual edge detection timing') and normal edge detection timing is calculated, then if it is the reference value or more ('N' in S14), the next data signal D2 is read when the time is counted which is compensated by adding the time difference α to the time Ts (S16). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sensor system that includes a plurality of sensor units and exchanges transmission signals between the sensor units and the sensor unit.
[0002]
[Prior art]
Conventionally, for example, a so-called bucket relay in which a plurality of sensor units are adjacently arranged in a predetermined order, and each sensor unit receives a transmission signal from an upper sensor unit and transmits a transmission signal to a lower sensor unit. There is a sensor system that performs data transmission in a system. Specifically, the transmission signal 1 is a digital signal including a synchronization signal 2 and a data group signal formed by connecting a plurality of high-level or low-level data signals 3. As shown in FIG. 6, each sensor system transmits the synchronization signal 2 of the transmission signal 1 to the lower sensor unit, and subsequently the clock of its own clock oscillator based on the transmission timing of the synchronization signal 2. A plurality of data signals 3 are sequentially transmitted at every transmission timing (timing at time t1 in the figure) synchronized with the pulse (see the top timing chart in the figure).
[0003]
On the other hand, the next-stage sensor unit that receives the transmission signal 1 from the upper sensor unit synchronizes with the clock pulse of its own clock oscillator based on the reception timing of the synchronization signal 2, and receives each reception timing corresponding to the transmission timing. Each data signal 3 of the data group signal is sequentially read at (timing every time t1 in the figure). Therefore, if there is no deviation in the clock timing of the clock oscillator built in each sensor unit, each data signal of the data group signal can be accurately read in each sensor unit (refer to the time chart in the second stage of the figure). ).
[0004]
[Patent Document 1]
JP 2001-222786 A
[0005]
[Problems to be solved by the invention]
However, in order to perform normal data transmission as described above, it is necessary to use a high-accuracy clock oscillator that does not generate clock timing for each sensor unit, resulting in a problem that the cost of the entire sensor increases. Therefore, in order to reduce the cost, a low-cost clock oscillator may be used for each sensor unit. As a result, the deviation of the reading timing of each data signal 3 increases in a superimposed manner due to the deviation of the clock timing between the clock oscillators of each sensor unit, and each of the data group signals at a timing different from the timing to be originally read. There is a risk of reading data. This will be specifically described with reference to the time chart shown in FIG. In the figure, the first time chart shows the waveform of the transmission signal 1 transmitted from the upper sensor unit. In this case, a plurality of data signals are continued every time t1 following the synchronization signal 2. The second stage shows a time chart of the receiving operation of the next stage sensor unit that receives the transmission signal 1, and the clock timing of the clock transmitter between the next stage sensor unit and the upper sensor unit is not shifted. It is. In this case, the sensor unit of the next stage operates to read the data group signal of the transmission signal 1 every time t1 from the reception timing of the synchronization signal, and can accurately read each data signal of the data group signal.
[0006]
On the other hand, in the third stage, the clock timing of the clock oscillator of the next stage sensor unit is delayed with respect to the upper sensor unit, and the data of the transmission signal 1 every time t2 (> t1) from the reception timing of the synchronization signal. It is a time chart in the case of operate | moving so that a group signal may be read. In such a case, the deviation of the reading timing of each data signal 3 is increased in a superimposed manner, and there is a malfunction that erroneously reads the data signal adjacent to the data signal that should be read, such as after the receiving timing X in FIG. It may occur.
[0007]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a sensor system and its sensor unit capable of receiving accurate data even when the built-in clock operation between the sensor units is shifted. There is a place to do.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a sensor system according to a first aspect of the present invention is a sensor system comprising a plurality of sensor units that perform a detection operation in accordance with a detection state of an object to be detected. Receiving means for receiving a transmission signal comprising a synchronization signal and a data group signal composed of a plurality of high-level or low-level data signals from another sensor unit; and the transmission signal to another sensor unit. Transmitting means for transmitting the transmission signal, and the transmission signal is exchanged between the plurality of sensor units. In the sensor system, each sensor unit transmits the transmission signal via the transmission means. A synchronization signal is transmitted, and after that, every reference time interval based on its own internal clock based on the transmission timing of the synchronization signal Transmission control means for sequentially transmitting each data signal of the data group signal, synchronization signal detection means for detecting a synchronization signal from a transmission signal received by the reception means, and always detected by the synchronization signal detection means Data reading means for sequentially reading each data signal of the data group signal at each reference time interval based on a synchronization signal, and a rising edge or a falling edge of each data signal of the transmission signal received by the receiving means Edge detection means for detecting the normal edge detection closest to the actual edge detection timing at which the edge is detected by the edge detection means among the normal edge detection timings based on the synchronization signal detected by the synchronization signal detection means Extraction means for extracting timing; real edge detection timing; and regular edge detection data extracted by the extraction means Comparing the timing has a characteristic in corrected reference time interval based on the comparison result reading process of the next data signal at which a correcting means for causing said data reading means.
[0009]
Here, the “regular edge detection timing” of the present invention is a timing at which a rising edge or a falling edge should be originally detected when there is no deviation between the oscillation operations of the sensor units. Before the correction operation, each timing of the reference time counted based on the reception timing of the synchronization signal is referred to. After the correction operation, the reference interval counted based on the timing of the next data signal reading process The timing of each.
[0010]
The sensor system according to a second aspect of the present invention is the sensor system according to the first aspect, wherein the correction unit detects a timing error between the actual edge detection timing and a normal edge detection timing extracted by the extraction unit. Then, on the condition that the timing error exceeds a predetermined value, the data reading unit is caused to read the next data signal at a reference time interval corrected according to the timing error.
[0011]
According to a third aspect of the present invention, in the sensor system according to the first or second aspect, the data group signal of the transmission signal has a time during which the high level or the low level continues for another sensor unit within this time. It is characterized in that it is configured such that the maximum amount of deviation generated according to the built-in clock error does not exceed half of the reference time.
Note that the “maximum deviation amount” of the present invention includes, for example, a time obtained by multiplying a time during which a high level or a low level continues by a deviation rate per unit time in a built-in clock with another sensor unit.
[0012]
According to a fourth aspect of the present invention, in the sensor system according to any one of the first to third aspects, a high level continuous time in which a high level continues after a rising edge is detected by the edge detection means, First determining means for determining whether or not the high level continuous time is equal to or greater than the reference time, the edge detecting means is configured to detect a rising edge of each data signal, and the data reading means includes the first reading means. 1 When the determination means determines that the high-level continuous time is equal to or longer than the reference time, the data signal read within the reference time after detection of the rising edge among the data signals read in each reading process. The first determination means determines that the high level continuous time is shorter than the reference time. Sometimes, among data signals to be read in each of reading process, having characterized in that the after the detection of the rising edge, and is configured such that the level of the read data signal in the reference period considered as the low level.
[0013]
According to a fifth aspect of the present invention, in the sensor system according to any one of the first to third aspects, is the rising edge detection timing of the edge detection means substantially coincident with any of the regular edge detection timings? A second determination unit configured to determine whether the edge detection unit detects a rising edge of each data signal, and the data reading unit detects the rising edge at the second determination unit. Is determined to be substantially coincident with the regular edge detection timing, the data signal level read within the reference time from the detection timing of the rising edge is regarded as a high level.
[0014]
The sensor unit according to the invention of claim 6 performs a detection operation according to the detection state of the detected object, and also connects a synchronization signal and a plurality of high-level or low-level data signals from other sensor units. In a sensor unit comprising a receiving means for receiving a transmission signal comprising a data group signal and a sending means for sending the transmission signal to another sensor unit, a synchronization of the transmission signals via the sending means. Transmission control means for transmitting a signal, and then sequentially transmitting each data signal of the data group signal at every reference time interval based on its own internal clock based on the transmission timing of the synchronization signal; and the receiving means A synchronization signal detecting means for detecting a synchronization signal from the transmission signal received in the step, and always based on the synchronization signal detected by the synchronization signal detecting means Data reading means for sequentially reading each data signal of the data group signal at every interval, and edge detecting means for detecting a rising edge or a falling edge of each data signal of the transmission signal received by the receiving means And an extraction means for extracting a normal edge detection timing closest to the actual edge detection timing at which the edge is detected by the edge detection means from among the normal edge detection timings based on the synchronization signal detected by the synchronization signal detection means The actual edge detection timing is compared with the regular edge detection timing extracted by the extraction means, and the next data signal reading process is performed on the data reading means at a reference time interval corrected based on the comparison result. It has a feature in that it is provided with correction means to be performed.
[0015]
The sensor unit according to a seventh aspect of the present invention is the sensor unit according to the sixth aspect, wherein the correction means detects a timing error between the actual edge detection timing and a regular edge detection timing extracted by the extraction means. Then, on the condition that the timing error exceeds a predetermined value, the data reading unit is caused to read the next data signal at a reference time interval corrected according to the timing error.
[0016]
According to an eighth aspect of the present invention, in the sensor unit according to the sixth or seventh aspect, the data group signal of the transmission signal has a time during which a high level or a low level continues, with another sensor unit within this time. It is characterized in that it is configured such that the maximum amount of deviation generated according to the built-in clock error does not exceed half of the reference time.
[0017]
The invention of claim 9 is the sensor unit according to any one of claims 6 to 8, wherein a high level continuous time in which a high level continues after a rising edge is detected by the edge detection means, First determining means for determining whether or not the high level continuous time is equal to or greater than the reference time, the edge detecting means is configured to detect a rising edge of each data signal, and the data reading means includes the first reading means. 1 When the determination means determines that the high-level continuous time is equal to or longer than the reference time, the data signal read within the reference time after detection of the rising edge among the data signals read in each reading process. The first determination means determines that the high level continuous time is shorter than the reference time. Sometimes, among data signals to be read in each of reading process, having characterized in that the after the detection of the rising edge, and is configured such that the level of the read data signal in the reference period considered as the low level.
[0018]
According to a tenth aspect of the present invention, in the sensor unit according to any one of the sixth to eighth aspects, is the rising edge detection timing of the edge detection means substantially coincident with any of the regular edge detection timings? A second determination unit configured to determine whether the edge detection unit detects a rising edge of each data signal, and the data reading unit detects the rising edge at the second determination unit. Is determined to be substantially coincident with the regular edge detection timing, the data signal level read within the reference time from the detection timing of the rising edge is regarded as a high level.
[0019]
[Action and effect of the invention]
<Invention of Claims 1, 2, 6, 7>
According to this configuration, a synchronization signal is detected from a transmission signal received from another sensor unit, and normally, a reference time based on its own internal clock based on the reception timing of the synchronization signal (the synchronization signal is transmitted in the transmission operation). After transmission, the data signal of the data group signal is read every time the self-built-in clock (the time interval of each data signal transmission counted based on its own oscillation means). On the other hand, when the actual edge detection timing at which the edge is detected by the edge detection means deviates from the nearest regular edge detection timing (in the configurations of claims 2 and 7, when the deviation time is a predetermined value or more) ), And operates so as to read the next data signal at the timing corrected in the direction to eliminate the deviation (the timing at which the reference time interval is lengthened or shortened).
Therefore, accurate data reception can be performed even when the built-in clock operation between the sensor units varies.
[0020]
<Invention of Claims 3 and 8>
For example, when a high level or low level continues for a predetermined time or more with respect to a data group signal of a transmission signal (when a rising edge or a falling edge does not occur), two regular edge detections whose actual edge detection timings are adjacent to each other There is a case where it is not possible to determine which of the regular edge detection timings is closest to the timing in the middle of the timing, and there is a possibility that the next data signal reading timing is erroneously corrected. Therefore, according to the present configuration, the data group signal of the transmission signal has a time during which the high level or the low level continues, and the maximum deviation amount generated according to the built-in clock error with another sensor unit within this time is the reference level. It is configured not to exceed half of the time. More specifically, the time obtained by multiplying the time at which the high level or low level continues by the deviation rate per unit time in the built-in clock with another sensor unit does not exceed half of the reference time. Has been. Therefore, the actual edge detection timing is always closest to any one of the regular edge detection timings, and it is possible to prevent erroneous correction of the reading timing for the next data signal.
[0021]
<Inventions of Claims 4 and 9>
For example, although the data signal of the transmission signal is originally at a low level due to noise, the data signal may be erroneously read due to a temporary high level. Therefore, according to the present configuration, when a high level continues for more than the reference time after the edge is detected, this is regarded as the original level of the data signal and is read if it is shorter than the reference time. Is considered to be read as a low level. Thus, accurate data reception can be performed without being affected by primary noise generation.
[0022]
<Invention of Claims 5 and 10>
For example, each data signal may be shorter than the original data length (duty ratio) due to the influence of noise or the like. In this case, there is a possibility that a data signal that should be read as a high level is read as a low level. Therefore, according to this configuration, when the rising edge detection timing substantially matches one of the regular edge detection timings, the data signal level read within the reference time after the rising edge is detected is set to the high level. Works to read as Therefore, each data signal can be read accurately even when the data length of the data signal changes due to the influence of noise or the like.
[0023]
In the present invention, the reading process of each data signal is a so-called majority decision in which the signal level is sequentially read an odd number of times within the reference time and the higher level (high level or low level) is used as the signal level of the data signal. The configuration may be such that a data signal is read by a method.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
A sensor system according to the present invention will be described with reference to FIGS. In FIG. 1, the direction of arrow A is the forward direction, and the direction of arrow B is the right direction.
1. Outline configuration of the entire sensor system
The sensor system of the present embodiment is configured to include 16 optical fiber sensors 1 (only four of which are shown in FIGS. 1 and 2, which correspond to the “sensor unit” of the present invention) having the same structure. The fiber sensors 1 are arranged adjacent to each other with the tip of the optical fiber F derived therefrom facing the detection region, and perform a detection operation in accordance with the presence or absence of an object to be detected in the detection region. The sensor system is positioned on the other end side from the optical fiber sensor 1 positioned on one end side while reflecting the detection result of each optical fiber sensor 1 on the transmission signal D transmitted from the communication unit 2. Data transmission (serial transmission) is performed by a so-called bucket relay system, which is sequentially transferred to the optical fiber sensor 1.
[0025]
In the following description, when referring to the entire optical fiber sensor 1, it is referred to as a sensor 1, and when referring to individual optical fiber sensors 1, the first optical fiber sensor 1, the second optical fiber sensor 1 are referred to These are referred to as sensor 1, third sensor 1, and fourth sensor 1.
[0026]
2. External configuration of each device
(1) Optical fiber sensor
As shown in FIG. 1, each sensor 1 has a box shape, and a front end of an optical fiber F is inserted into a fiber insertion hole provided on the front surface. On the other hand, a cable connector connected to a control unit (not shown) on the rear surface. C is connected. Further, a light projecting element 12 corresponding to the output side coupler is provided on the right side surface of the sensor 1, and a light receiving element 11 corresponding to the input side coupler is provided on the left side surface. A square-shaped through-hole 13 is formed. Further, a pinching portion (hidden by the terminal unit 4 in FIG. 1) is formed by forming dovetail grooves (grooves whose opening side is narrower than the bottom surface side) along the alignment direction of the sensors 1 on the lower surface. (Not shown) is provided.
[0027]
The sensor 1 is mounted by passing the clamping portion through a groove of a well-known DIN rail 3 corresponding to a mounting rail, and the light projecting element 12 and the light receiving element 11 of the sensor 1 that are closely adjacent to each other face each other. It has become a state.
[0028]
(2) Communication unit and termination unit
A box-shaped communication unit 2 and a terminal unit 4 are arranged on the sides of the first and fourth sensors 1. The communication unit 2 is provided with a holding part (not shown) having the same shape as the holding part of the sensor 1, and is attached to the holding part through the DIN rail 3. In addition, two screw holes 21 formed so as to penetrate between the upper and lower side surfaces are provided, and a screw 22 that is screwed into the screw hole 21 is provided. 3 can be inserted and fixed to the DIN rail 3. The end unit 4 is also provided with a clamping portion 41, a screw hole 42 and a screw 43, and can be fixed to the DIN rail 3 by tightening the screw 43.
[0029]
The light projecting element 23 corresponding to the output side coupler provided on the right side surface of the communication unit 2 is disposed at a position facing the light receiving element 11 of the first sensor 1, and is positioned at the position facing the through hole 13 at the input side. A light receiving element 24 corresponding to a coupler is provided. Further, the light receiving element 44 corresponding to the relay input unit provided on the left side surface of the termination unit 4 is arranged at a position facing the light projecting element 12 of the fourth sensor 1, and at a position facing the through hole 13. A light projecting element 45 corresponding to the relay output unit is provided. An optical axis can be formed between the light projecting element 45 of the termination unit 4 and the light receiving element 24 of the communication unit 2 through the through hole 13 of the sensor 1.
[0030]
3. Electrical configuration of each device
Next, the electrical configuration of the sensor system will be described with reference to FIG.
(1) Communication unit
First, a setting operation unit 20 is provided in the housing of the communication unit 2. An address for specifying the communication partner sensor 1 by operating a setting switch provided therein and the sensor 1 should be executed. You can enter commands. The switch state of this setting switch is captured by the CPU 25, where a transmission signal D is generated and provided to the light projecting circuit 26 which constitutes the communication unit side transmitting means together with the light projecting element 23. The light projecting circuit 24 supplies a drive current to the light projecting element 23 based on the transmission signal D, and sequentially transmits the transmission signal D as an optical signal to the first sensor 1 at a predetermined cycle (for example, 50 μS). On the other hand, the light incident on the light receiving element 24 is input to the CPU 25 via the light receiving circuit 27 corresponding to the communication unit side receiving means.
[0031]
(2) Optical fiber sensor
In each sensor 1, the transmission signal D received as an optical signal by the light receiving element 11 is converted into an electric signal, and this light receiving element 11 and the light receiving circuit 14 constituting the inter-sensor receiving means (“receiving means” of the present invention). It is converted into a digital signal and given to the CPU 15. The CPU 15 executes a detection operation, a data signal reading process, and the like based on the synchronization signal included in the transmission signal D, as will be apparent from the description of the software configuration described later. Then, the transmission signal D reflecting its own detection result is sent to the light projecting circuit 16 that constitutes the inter-sensor transmitting means (the “transmitting means” of the present invention) together with the light projecting element 12, and the driving current is sent from the light projecting circuit 16. Is supplied to the light projecting element 12 for light projection.
[0032]
(3) Termination unit
The light incident on the light receiving element 44 corresponding to the relay input section of the termination unit 4 is converted into a digital signal by the light receiving circuit 46 and then sent to the light projecting circuit 47 via the relay amplifier 48 having a signal amplification function. Sent out. Based on the signal, the light projecting circuit 47 supplies a drive current to the light projecting element 45 corresponding to the relay output unit to project light from the light projecting element 45. As a result, the transmission signal D transmitted between the sensors 1 is returned from the termination unit 4 to the communication unit 2. The output of the light projecting element 45 is set to be stronger than the light projecting element 12 of the sensor 1.
[0033]
4). Software configuration
The CPU 15 of each sensor 1 has a built-in clock oscillator that outputs a clock pulse, and performs transmission processing and reception processing of the transmission signal D based on the clock pulse from its own clock oscillator. The transmission signal D is a digital signal including a synchronization signal D1 and a data group signal formed by connecting a plurality of high-level or low-level data signals D2. The clock oscillator is not limited to the one built in the CPU 15 and may be provided separately.
[0034]
(1) Transmission operation of transmission signal
FIG. 4 shows a flowchart showing the transmission operation routine. When the timing for starting transmission of the transmission signal D comes, the CPU 15 first sends the synchronization signal D1 to the light projecting circuit 16 in step S1, and starts from the transmission timing of the synchronization signal D1, and the reference time based on its own clock pulse. Each time Ts is counted, a high-level or low-level data signal D2 is sequentially transmitted to the light projecting circuit 16 (steps S2 to S5. Refer to the uppermost time chart of FIG. 3 for the transmission signal D waveform). Accordingly, each sensor 1 transmits a transmission signal D having a data interval corresponding to the clock pulse from its own clock oscillator to the lower sensor 1. Therefore, at this time, the CPU 15 functions as the “transmission control means” of the present invention.
[0035]
(2) Transmission signal reception operation
FIG. 5 shows a flowchart showing the reception operation routine. When the CPU 15 receives the synchronization signal D1 from the upper sensor 1, the CPU 15 starts the reception operation routine of FIG. In step S11, time counting is started based on the clock pulse of the own clock oscillator. In step S12, the presence or absence of a rising edge is detected. If the rising edge is not detected (“Y” in step S12), the data signal D2 is read when the time Ts (reference time) is counted (step S15). On the other hand, when a rising edge is detected (“N” in step S12), a time difference α between the rising edge detection timing (hereinafter, “real edge detection timing”) and the regular edge detection timing is calculated. Here, the regular edge detection timing refers to a timing at which a rising edge can be detected when counted by its own clock oscillator. Before the following read timing correction operation is performed, the reception timing of the synchronization signal D1 is used as a reference. And the timing for each time obtained by multiplying the reference time Ts by an integer. Further, after the correction operation described below, the timing becomes every time obtained by multiplying the reference time Ts by an integer with the next data reading timing as a reference.
[0036]
Subsequently, if the absolute value of the time difference α is less than the reference value (“Y”) in step S14, the data signal D2 is read when the time Ts is counted in step S15, as in the case where the rising edge is not detected. On the other hand, when the absolute value of the time difference α is greater than or equal to the reference value in step S14 (“N”), the data signal D2 is read when the time corrected by adding the time difference α to the time Ts is counted in step S16. . The above operation is repeated until the data signal D2 disappears (step S17). Accordingly, at this time, the CPU 15 functions as the “data reading unit”, “edge detection unit”, “extraction unit”, and “correction unit” of the present invention.
[0037]
In this embodiment, the reading process of each data signal D2 reads the level of the data signal D2 an odd number of times (three times in this embodiment) at predetermined time intervals in synchronization with the reading timing or the corrected reading timing. The level of the data signal D2 is determined by a so-called majority method in which the higher level (high level or low level) is determined as the level of the data signal D2. With such a configuration, the level of each data signal D2 can be accurately read even if the clock pulse of the clock oscillator between the sensors is slightly deviated.
In addition, the CPU 15 projects light from the light projecting unit 17 in synchronization with the reception timing of the synchronization signal D2 of the received transmission signal D, irradiates the detection region via the optical fiber F, and emits light from the detection region. Light is converted into a digital signal by the light receiving unit 18 and taken in, and a detection operation is performed in which the received light amount data is compared with a currently set threshold value to determine the presence or absence of a detection object. Then, the detection result is reflected in the data group signal of the transmission signal D given to the lower sensor 1.
[0038]
(3) Specific operation
A specific operation will be described with reference to FIG. In the figure, the uppermost stage is a time chart of the transmission signal D transmitted from the upper sensor 1, and the second and subsequent stages of the sensor 1 (lower sensor 1) of the next order receiving the transmission signal D from the upper sensor 1 are shown. It is a reception operation time chart. The second stage is a reception operation time chart when there is no deviation in the oscillation operation (clock pulse interval t1) of the clock oscillator between the upper sensor 1 and the lower sensor 1, and the third stage is a clock in the lower sensor 1. 6 is a reception operation time chart when the pulse interval t2 is longer than the clock pulse interval t1 in the upper sensor 1. The fourth stage is a reception operation time chart when the clock pulse interval t3 in the lower sensor 1 is shorter than the clock pulse interval t1 in the upper sensor 1.
[0039]
First, as shown in the second stage, when there is no deviation in the clock pulse interval t1 between the upper sensor 1 and the lower sensor 1, the transmission signal D from the upper sensor 1 is positioned at the position of each data signal D2 arranged every time interval Ts. Correspondingly, the data signal D2 can be read sequentially at the same time interval Ts so that the data can be read accurately.
[0040]
On the other hand, as shown in the third stage, when the clock pulse interval t2 in the lower sensor 1 is longer than the clock pulse interval t1 in the upper sensor 1, the cycle (time) is longer than the data signal D2 interval Ts of the transmission signal D from the upper sensor 1. Each data signal D2 is read at T1> Ts). Accordingly, the deviation gradually increases. However, in the present embodiment, the rising edge that should be detected between the (7) -th reading process and the (8) -th reading process (regular edge detection timing) is detected by time α1. This means that each lower reading process is delayed with respect to each data signal D2 of the transmission signal D. Therefore, the reading timing is corrected so that the (8) -th reading process starts when the time T1-α1 is counted from the (7) -th reading timing. That is, the (8) -th reading process is executed at a timing earlier by the time α1. The (9) -th reading process is executed when time T1 is counted from the start of the (8) -th reading process executed at the corrected reading timing. As a result, each data signal D2 can be read normally in the (9) th and subsequent reading processes.
[0041]
Next, as shown in the fourth stage, when the clock pulse interval t3 in the lower sensor 1 is shorter than the clock pulse interval t1 in the upper sensor 1, a cycle shorter than the data signal D2 interval Ts of the transmission signal D from the upper sensor 1 ( Each data signal D2 is read at time T2> Ts). Therefore, the deviation gradually increases. However, in the present embodiment, the rising edge that should be detected between the (3) -th reading process and the (4) -th reading process (regular edge detection timing) is detected after the time α2. This means that each lower-level reading process is faster for each data signal D2 of the transmission signal D. Therefore, the reading timing is corrected so that the (5) -th reading process starts when the time T1 + α2 is counted from the (4) -th reading timing. That is, the (5) -th reading process is executed at a timing delayed by the time α2. The (6) -th reading process is executed when time T2 is counted from the start of the (5) -th reading process executed at the corrected reading timing. Thereby, each data signal D2 can be normally read also in the reading process after the (5) th time.
[0042]
Thereafter, the rising edge to be detected between the (7) -th reading process and the (8) -th reading process (regular edge detection timing) is detected after time α3. Therefore, the reading timing is corrected so that the (9) -th reading process starts when the time T1 + α3 is counted from the (8) -th reading timing. That is, the (9) -th reading process is executed at a timing delayed by the time α3. Thereby, each data signal D2 can be normally read also in the (9) th and subsequent reading processes.
[0043]
5). Measures against waveform deformation of transmission signal D
By the way, the waveform of the transmission signal D may be deformed due to the influence of noise or the like. Therefore, in the present embodiment, the following measures are taken in the reading process.
(1) When a primary high-level signal is carried on the transmission signal D
For example, a high level signal may be temporarily transmitted due to noise or the like as indicated by a two-dot broken line X in FIG. In this case, the data signal D2 that should be read as a low level is read as a high level. However, in the present embodiment, when the rising time is detected and the time during which the high level continues is equal to or longer than the time Ts (T1, T2), it is regarded as the normal data signal D2, and the time Ts (T1, T2). The data signal D2 level read in is processed as a high level. On the other hand, when the time when the high level continues after the rising edge is detected is less than the time Ts (T1, T2), it is regarded as not the normal data signal D2, and the data signal read within the time Ts (T1, T2) D2 is processed at a low level (corresponding to the configurations of claims 4 and 9).
With such a configuration, data can be accurately read without being affected by primary noise or the like.
[0044]
(2) When the high level data signal D2 of the transmission signal D is partially missing
For example, the high-level data signal D2 may be partially lost due to the influence of noise or the like, as indicated by a two-dot broken line Y in FIG. In this case, the data signal D2 that should be read as a high level is read as a low level. However, in the present embodiment, when the rising edge detection timing (actual edge detection timing) substantially coincides with the regular edge detection timing, within the time Ts (T1, T2) from the rising edge detection timing. Processing is performed by regarding the read data signal D2 level as a high level (corresponding to the configurations of claims 5 and 10).
With such a configuration, it is possible to accurately read data even if a high-level signal is partially lost.
[0045]
6). Effects of this embodiment
As described above, according to the present embodiment, the synchronization signal D1 is detected from the transmission signal D received from the upper sensor 1, and normally, the reference time Ts (T1, T2, T2) is based on the reception timing of the synchronization signal D1. The data signal D2 of the data group signal is read at every reading timing corresponding to T3). On the other hand, when the timing at which the rising edge is detected (actual edge detection timing) is deviated by a predetermined value or more from the nearest regular edge detection timing, the timing corrected in the direction to eliminate the misalignment (correct the reference time) Thus, the reading operation of the next data signal D2 is performed at a timing at which the reading timing is advanced or delayed).
Therefore, accurate data reception can be performed even when a deviation occurs in the clock pulse of the clock oscillator of each sensor 1.
[0046]
Furthermore, in this embodiment, the transmission signal D is such that the time obtained by multiplying the time at which the high level or low level continues by the deviation rate per unit time does not exceed half of the reference time Ts (T1, T2, T3). It is configured. Here, the “deviation rate per unit time” refers to the maximum deviation rate per unit time in a built-in clock with another sensor unit. Specifically, in this embodiment, the deviation rate per unit time may be 1% per 1 μS. Therefore, the transmission signal D has a data configuration that satisfies the following expression (corresponding to the configurations of claims 3 and 8).
“Time for which high level or low level continues” * 0.01 <“reference time Ts (T1, T2, T3)” / 2
With such a configuration, even if the rising edge or falling edge of the transmission signal D is not detected and the reading timing is not corrected, the maximum deviation time is half of the reference time Ts (T1, T2, T3). Therefore, the actual edge detection timing is always closest to any one of the regular edge detection timings, and it is possible to prevent erroneous correction of the reading timing for the next data signal.
[0047]
<Other embodiments>
The present invention is not limited to the above-described embodiment. For example, the embodiments described below are also included in the technical scope of the present invention, and various other than the following can be made without departing from the scope of the invention. It can be changed and implemented.
(1) In the above-described embodiment, the configuration is such that the reading timing of the data signal is corrected according to the amount of deviation on the condition that the deviation between the actual edge detection timing and the regular edge detection timing is a predetermined value or more. Not limited to this, the actual edge detection timing is compared with the closest regular edge detection timing, and the reading timing is corrected (shortened or lengthened) by a predetermined value according to the comparison result. (Corresponding to the configurations of claims 1 and 6).
[0048]
(2) In the above embodiment, the rising edge is detected, and the data signal reading timing is corrected based on the detection timing and the normal edge detection timing. However, the falling edge is detected and detected. The configuration may be such that the data signal reading timing correction operation is performed based on the timing and the regular edge detection timing. Furthermore, the configuration may be such that both the rising edge and the falling edge are detected, and the correction operation is performed based on these detection timings and regular edge detection timings.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an external appearance of a sensor system according to an embodiment of the present invention.
FIG. 2 is a block diagram showing the internal configuration of the sensor system.
FIG. 3 is a time chart showing a transmission signal from the upper sensor and a reception timing in the lower sensor.
FIG. 4 is a flowchart showing a transmission operation routine.
FIG. 5 is a flowchart showing a reception operation routine.
FIG. 6 is a time chart showing a transmission signal from a higher sensor and a reception timing in a lower sensor in a conventional sensor system.
[Explanation of symbols]
1 ... Sensor (sensor unit)
11: Light receiving element
12 ... Projection element
14: Light receiving circuit
15 ... CPU
16: Floodlight circuit
17 ... Projector
18. Light receiving part
D ... Transmission signal
D1 ... Synchronization signal
D2: Data signal
Ts (T1, T2, T3) ... reference time

Claims (10)

A sensor system comprising a plurality of sensor units that perform a detection operation according to a detection state of a detected object,
Each sensor unit includes, from other sensor units, receiving means for receiving a transmission signal including a synchronization signal and a data group signal composed of a plurality of high level or low level data signals, and other sensors. A sensor system configured to transmit the transmission signal to a unit, and configured to exchange the transmission signal between the plurality of sensor units;
Each sensor unit is
Each of the data group signals is transmitted at each reference time interval based on its own internal clock based on the transmission timing of the synchronization signal after transmitting a synchronization signal among the transmission signals via the transmission means. Transmission control means for sequentially transmitting signals;
Synchronization signal detecting means for detecting a synchronization signal from the transmission signal received by the receiving means;
Always, a data reading unit that sequentially performs a reading process of reading each data signal of the data group signal at each reference time interval based on the synchronization signal detected by the synchronization signal detection unit;
Edge detecting means for detecting a rising edge or a falling edge of each data signal of the transmission signal received by the receiving means;
An extraction means for extracting a normal edge detection timing closest to an actual edge detection timing at which an edge is detected by the edge detection means among normal edge detection timings based on the synchronization signal detected by the synchronization signal detection means;
The actual edge detection timing is compared with the regular edge detection timing extracted by the extraction means, and the data reading means is caused to read the next data signal at a reference time interval corrected based on the comparison result. A sensor system comprising a correcting means. The correction unit detects a timing error between the actual edge detection timing and the regular edge detection timing extracted by the extraction unit, and sets the timing error on condition that the timing error exceeds a predetermined value. 2. A sensor system according to claim 1, wherein said data reading means is made to perform reading processing of a next data signal at a reference time interval corrected accordingly. The data group signal of the transmission signal is such that the time during which the high level or the low level continues, the maximum deviation caused by the built-in clock error with other sensor units within this time does not exceed half of the reference time. The sensor system according to claim 1, wherein the sensor system is configured as follows. A first determination unit that measures a high level continuous time in which a high level continues after a rising edge is detected by the edge detection unit, and determines whether the high level continuous time is equal to or greater than the reference time; The edge detection means is configured to detect a rising edge of each data signal,
The data reading means includes
When the first determination means determines that the high-level continuous time is equal to or longer than the reference time, the data signal read in each reading process is read within the reference time after detection of the rising edge. The data signal level is considered high level,
When the first determination means determines that the high-level continuous time is shorter than the reference time, the data read within the reference time after detection of the rising edge, among the data signals read in the respective reading processes 4. The sensor system according to claim 1, wherein the sensor system is configured to regard the level of the signal as a low level. And a second determining means for determining whether a detection timing of the rising edge in the edge detecting means substantially coincides with any of the regular edge detection timings, and the edge detecting means includes a rising edge of each data signal. Configured to detect
When the second determining means determines that the rising edge detection timing is substantially coincident with the regular edge detection timing, the data reading means falls within the reference time from the rising edge detection timing. 4. The sensor system according to claim 1, wherein the read data signal level is regarded as a high level. Performs detection operation according to the detection state of the object to be detected, and receives a transmission signal including a synchronization signal and a data group signal composed of a plurality of high level or low level data signals from other sensor units. In a sensor unit comprising receiving means for transmitting and transmitting means for transmitting the transmission signal to another sensor unit,
Each of the data group signals is transmitted at each reference time interval based on its own internal clock based on the transmission timing of the synchronization signal after transmitting a synchronization signal among the transmission signals via the transmission means. Transmission control means for sequentially transmitting signals;
Synchronization signal detecting means for detecting a synchronization signal from the transmission signal received by the receiving means;
Always, a data reading unit that sequentially performs a reading process of reading each data signal of the data group signal at each reference time interval based on the synchronization signal detected by the synchronization signal detection unit;
Edge detecting means for detecting a rising edge or a falling edge of each data signal of the transmission signal received by the receiving means;
An extraction means for extracting a normal edge detection timing closest to an actual edge detection timing at which an edge is detected by the edge detection means among normal edge detection timings based on the synchronization signal detected by the synchronization signal detection means;
The actual edge detection timing is compared with the regular edge detection timing extracted by the extraction means, and the data reading means is caused to read the next data signal at a reference time interval corrected based on the comparison result. A sensor unit comprising a correcting means. The correction unit detects a timing error between the actual edge detection timing and the regular edge detection timing extracted by the extraction unit, and sets the timing error on condition that the timing error exceeds a predetermined value. 7. The sensor unit according to claim 6, wherein the data reading unit is caused to read a next data signal at a reference time interval corrected accordingly. The data group signal of the transmission signal is such that the time during which the high level or the low level continues, the maximum deviation caused by the built-in clock error with other sensor units within this time does not exceed half of the reference time. The sensor unit according to claim 6, wherein the sensor unit is configured as follows. A first determination unit that measures a high level continuous time in which a high level continues after a rising edge is detected by the edge detection unit, and determines whether the high level continuous time is equal to or greater than the reference time; The edge detection means is configured to detect a rising edge of each data signal,
The data reading means includes
When the first determination means determines that the high-level continuous time is equal to or longer than the reference time, the data signal read in each reading process is read within the reference time after detection of the rising edge. The data signal level is considered high level,
When the first determination means determines that the high-level continuous time is shorter than the reference time, the data read within the reference time after detection of the rising edge, among the data signals read in the respective reading processes 9. The sensor unit according to claim 6, wherein the signal level is regarded as a low level. And a second determining means for determining whether a detection timing of the rising edge in the edge detecting means substantially coincides with any of the regular edge detection timings, and the edge detecting means includes a rising edge of each data signal. Configured to detect
When the second determining means determines that the rising edge detection timing is substantially coincident with the regular edge detection timing, the data reading means falls within the reference time from the rising edge detection timing. 9. The sensor unit according to claim 6, wherein the read data signal level is regarded as a high level.

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