CN109298461B - Method for judging light projection state of correlation type photoelectric switch - Google Patents

Abstract

The purpose of the present application is to provide a method for judging a light projection state of a correlation-type photoelectric switch, by determining a judgment cycle according to a light projection cycle of a first photoelectric switch and/or a light projection cycle of a second photoelectric switch in the correlation-type photoelectric switch; taking the first optical signal received by the light receiver as a trigger signal, and performing a capturing task in the determination period according to the trigger signal to determine the number of effective optical signals captured by the capturing task in the determination period; and comparing the number of the effective optical signals with a preset threshold value, and determining the light projecting state of the light projector in the same group with the light receiver according to the comparison result, wherein the light projecting state comprises a light incident state and a light shading state. To prevent the two sets of light from malfunctioning after they interfere with each other. Therefore, the light projectors and the light receivers are in one-to-one correspondence only through simple setting without additional optical components.

Description

Method for judging light projection state of correlation type photoelectric switch

Technical Field

The application relates to the field of photoelectric switches, in particular to a method for judging a light projection state of a correlation type photoelectric switch.

Background

The correlation type photoelectric switch includes a light projector and a light receiver, and the light receiver detects the presence or absence of an object based on a received light pulse. Unlike a reflection-type photoelectric switch, a light receiver cannot precisely synchronize pulses of a light projector, so that light from the light projector enters the light receiver in the same manner as light from another group of correlation-type photoelectric switches arranged in parallel with the light receiver, causing malfunction, which is referred to as occurrence of interference. The product that two groups of opposite photoelectric switches are closely attached in parallel through the polaroid is called as a passive interference prevention method, and the cost of the product is increased.

As for the opposed-emitting photoelectric switch having the function of preventing the external stray light, a receiving method with a gate control signal is widely used at present, which can prevent the interference of the external stray light, and as shown in fig. 1, the timing chart shows that the light receiving gate (gate) and the light projecting period are set to be the same, and when the number of the light receiving signals falling on the light receiving gate reaches the set value, the light receiver judges that the light is the light of the own light projector. When there is a pulse discontinuity, it is considered to be stray light. In this way, light with a period greater than T2 can be shielded, but for light with a period less than T2, for example, two light receiving signals enter one light receiving gate, the signal processing circuit still considers itself as light and is continuously counted, which affects the correct judgment of the sensor. This way also does not have the mutual interference prevention function.

Therefore, there is a need for a method for determining optical signals in mutual interference of correlation-type optoelectronic switches, so as to identify signals of light projectors in the same group and prevent malfunction after mutual interference of two groups of light.

Disclosure of Invention

The purpose of the application is to provide a method for judging a light projection state of an opposite-type photoelectric switch, so as to solve the problems that the opposite-type photoelectric switch cannot be detected when interfering with each other, and the wiring and installation cost is increased for avoiding interference.

In order to solve the above technical problem, according to an aspect of the present application, there is provided a method for determining a light projection state of a correlation-type photoelectric switch, the method including:

determining a determination period according to a light projection period of a first photoelectric switch and/or a light projection period of a second photoelectric switch in the correlation type photoelectric switch, wherein the first photoelectric switch and the second photoelectric switch respectively comprise a light projector and a light receiver, and the frequencies of light projected by the corresponding light projectors are different;

taking the first optical signal received by the light receiver as a trigger signal, and performing a capturing task in the determination period according to the trigger signal to determine the number of effective optical signals captured by the capturing task in the determination period;

and comparing the number of the effective optical signals with a preset threshold value, and determining the light projecting state of the light projector in the same group with the light receiver according to the comparison result, wherein the light projecting state comprises a light incident state and a light shading state.

Further, determining the determination period according to the light projection period of the first photoelectric switch and/or the light projection period of the second photoelectric switch comprises at least any one of the following steps:

taking the least common multiple of the light projection period of the first photoelectric switch and the light projection period of the second photoelectric switch as a judgment period;

setting N times of a projector period of the first photoelectric switch as a determination period, wherein N is 1, 2,3, … …;

the determination period is N times the projector period of the second photoelectric switch, where N is 1, 2,3, and … ….

Further, determining the number of captured valid optical signals of the capture task within the decision period comprises:

opening the width of a signal capture gate corresponding to the light receiver after the signal capture period of the light receiver;

and judging whether the optical signal of the light projector in the same group with the light receiver is received within the time of the width of the signal capture door, if so, determining the received optical signal as a valid optical signal, and counting.

Further, the method comprises:

if the optical signal is not received within the time of the signal capture gate width, the previously determined number of valid optical signals is discarded and the trigger signal is re-determined.

Further, comparing the number of the effective optical signals with a preset threshold value, and determining the light projecting state of the light projector in the same group with the light receiver according to the comparison result, includes:

if the number of the effective optical signals is larger than or equal to a preset threshold value, the light projecting state of the light projector in the same group with the light receiver is a light incident state;

and if the number of the effective optical signals is less than a preset threshold value, the light projecting state of the light projector in the same group with the light receiver is a light shielding state.

Further, the method comprises:

and the signal capturing period of the light receiver is synchronous with the period of the light projecting pulse of the corresponding photoelectric switch, wherein the period of the light projecting pulse is used for the light projector to project light according to a preset period.

Further, after comparing the number of the effective optical signals with a preset threshold value and determining the light projecting state of the light projector in the same group with the light receiver according to the comparison result, the method includes:

and clearing the related data in the judging period, wherein the related data comprises the light projecting state of the light projector and the number of the effective light signals.

Further, the method further comprises:

and when the judging period is the least common multiple of the light projecting period of the first photoelectric switch and the light projecting period of the second photoelectric switch, if the optical signals of the light projectors in the same group as the light receiver are not received after 2 times of the time length of the judging period, abandoning the time sequence corresponding to the current capturing task, and offsetting the receiving time sequence according to preset time.

Compared with the prior art, the judgment period is determined according to the light projection period of a first photoelectric switch and/or the light projection period of a second photoelectric switch in the correlation type photoelectric switch, wherein the first photoelectric switch and the second photoelectric switch respectively comprise a light projector and a light receiver, and the frequencies of light projected by the corresponding light projectors are different; taking the first optical signal received by the light receiver as a trigger signal, and performing a capturing task in the determination period according to the trigger signal to determine the number of effective optical signals captured by the capturing task in the determination period; and comparing the number of the effective optical signals with a preset threshold value, and determining the light projecting state of the light projector in the same group with the light receiver according to the comparison result, wherein the light projecting state comprises a light incident state and a light shading state. Two groups of light emitters are used for emitting two groups of light with different frequencies, and the light receivers are used for identifying signals of the light emitters in the same group through a certain algorithm, so that misoperation caused by mutual interference of the two groups of light is prevented. Therefore, the light projector and the light receiver are in one-to-one correspondence only through simple setting without additional optical parts, wherein the setting method can be key operation, or wire switching, or can be completed through special operation after the machine is started.

Drawings

Other features, objects and advantages of the present application will become more apparent upon reading of the following detailed description of non-limiting embodiments thereof, made with reference to the accompanying drawings in which:

FIG. 1 illustrates a timing diagram for preventing interference in a prior art reception with gating signals;

fig. 2 is a schematic flow chart illustrating a method for determining a light projection state of a correlation-type photoelectric switch according to an aspect of the present application;

fig. 3 shows two sets of correlation-type photoelectric switches and signal structures thereof in an embodiment of the present application;

FIG. 4 is a schematic flow chart illustrating a process of determining a light projection state according to an embodiment of the present disclosure;

FIG. 5 is a timing diagram illustrating capturing of the same group of signal times in an embodiment of the present application.

The same or similar reference numbers in the drawings identify the same or similar elements.

Detailed Description

The present application is described in further detail below with reference to the attached figures.

Fig. 2 is a schematic flow chart of a method for determining a light projection state of a correlation-type optoelectronic switch provided in an aspect of the present application, where the method includes: a step S11 to a step S13, wherein in the step S11, a determination period is determined according to a light projection period of a first photoelectric switch and/or a light projection period of a second photoelectric switch in the correlation type photoelectric switch, wherein the first photoelectric switch and the second photoelectric switch each include a light projector and a light receiver, and frequencies of light projected by the corresponding light projectors are different; in step S12, performing a capturing task in the determination period according to the trigger signal with the first optical signal received by the light receiver as the trigger signal to determine the number of effective optical signals captured by the capturing task in the determination period; in step S13, the number of the effective optical signals is compared with a preset threshold, and a light projecting state of a light projector in the same group as the light receiver is determined according to the comparison result, wherein the light projecting state includes a light incident state and a light shielding state. Two groups of light emitters are used for emitting two groups of light with different frequencies, and the light receivers are used for identifying signals of the light emitters in the same group through a certain algorithm, so that misoperation caused by mutual interference of the two groups of light is prevented. Therefore, the light projector and the light receiver are in one-to-one correspondence only through simple setting without additional optical parts, wherein the setting method can be key operation, or wire switching, or can be completed through special operation after the machine is started.

Specifically, in step S11, a determination period is determined based on a light projection period of a first photoelectric switch and/or a light projection period of a second photoelectric switch in the correlation-type photoelectric switches, wherein each of the first photoelectric switch and the second photoelectric switch includes a light projector and a light receiver, and frequencies of light projected by the corresponding light projectors are different; here, as shown in the two opposed photoelectric switches and the signal structure diagram of fig. 3, the first photoelectric switch s1 and the second photoelectric switch s2 have different light emitting periods, and the period setting can be set according to the specific application. The first photoelectric switch S1 includes a light projector S1_ T and a light receiver S1_ D, and the second photoelectric switch S2 includes a light projector S2_ T and a light receiver S2_ D. Wherein, the meaning of each parameter symbol in fig. 3 is as follows:

pulse _ 1-projector light Pulse timing for the first opto-electronic switch,

pulse _ 2. projector light-emitting Pulse timing of the second photoelectric switch,

s1_ Judge _ gate, the photo receiver operation determination sequence of the first photoelectric switch,

s2_ Judge _ gate, the photo receiver operation judging sequence of the second photoelectric switch,

s1_ Catch _ gate the photoreceptor signal capture timing of the first photoelectric switch,

s2_ Catch _ gate the photoreceptor signal capture timing of the second photoelectric switch,

t1_1& T2_1 the widths of the light projection pulses of the first and second photoelectric switches,

t1_2& T2_ 2: the period of the light projection pulse of the first and second photoelectric switches,

t1_3& T2_3 is the photo detector operation determination cycle of the first and second photoelectric switches,

t1_4& T2_4 photo acceptor signal capturing periods of the first and second photo switches,

t1_5& T2_5 photo acceptor signal capture gate widths of the first and second photoelectric switches.

Setting a determination period through the light projection periods of the two photoelectric switches, wherein the minimum common multiple of the light projection period of the first photoelectric switch and the light projection period of the second photoelectric switch can be used as the determination period; or, taking N times of the projector period of the first photoelectric switch as the determination period, wherein N is 1, 2,3, … …; or, the determination period is N times the projector period of the second photoelectric switch, where N is 1, 2,3, … ….

Next, in step S12, the first optical signal received by the light receiver is used as a trigger signal, and the capturing task in the determination period is performed according to the trigger signal to determine the number of effective optical signals captured by the capturing task in the determination period; here, after the two photoelectric switches are energized, the light receiver captures the light reception signal in a set capture period, and counts the number of effective light signals captured in the determination period. Accordingly, in step S13, the number of effective optical signals is compared with a preset threshold, and the light projecting state of the light projector in the same group as the light receiver is determined according to the comparison result, wherein the light projecting state includes a light incident state and a light shielding state. The projector and the light receiver are set according to the determined projection state of the projector to prevent the malfunction after the two groups of lights interfere with each other.

In an embodiment of the present invention, in step S12, after the signal capturing period of the photo detector, the signal capturing gate width corresponding to the photo detector is opened; and judging whether the optical signal of the light projector in the same group with the light receiver is received within the time of the width of the signal capture door, if so, determining the received optical signal as a valid optical signal, and counting. Further, the method comprises: if the optical signal is not received within the time of the signal capture gate width, the previously determined number of valid optical signals is discarded and the trigger signal is re-determined.

Further, in step S13, if the number of the effective optical signals is greater than or equal to a preset threshold, the light projecting state of the light projector in the same group as the light receiver is a light incident state; and if the number of the effective optical signals is less than a preset threshold value, the light projecting state of the light projector in the same group with the light receiver is a light shielding state.

The photoelectric switch judges the light incidence signal and comprises two functions of a capturing period and a judging period, and after the photoelectric switch is electrified, two groups of light projectors which are installed in parallel project light according to the light projecting periods which are set by the photoelectric switch respectively. The light receiver performs a task of capturing a self light receiving signal and a task of judging whether the signal is valid after the capture.

A) Capturing execution of tasks

The trapping task is to find the same set of light in two sets of unordered incoming light, while eliminating the accumulated error. The detailed description is made in conjunction with the timing diagram in fig. 3:

after the photoelectric switch is electrified, the phases of two groups of light generated by the light projector are disordered, so when the light receiver enters the light incident state from the light incident state, the received first optical signal is used as a trigger signal, also called a synchronous signal, and the signal is used as a reference signal to carry out the next cycle of capturing the same group of signals. The method of processing the sensor signal is described by taking the first photoelectric switch s1 as an example.

The method comprises the following steps: after the light receiver s1 receives a light signal, the signal is used as a trigger signal to start the following step two;

step two: after the time T1_4, the gate signal T1_5 is turned on to receive the signal of s1 light projector, because the setting makes the period of the light projector and light receiver in the same group identical, if a light signal is received in the time T1_5, the light receiver defaults that the previous signal is sent by the light projector in the same group. The active semaphore counter now counts up to 2. If no signal is received within time T1_5, indicating that the previous trigger signal was another set of light signals of different periods, then the previous data is discarded and the process returns to a wait signal trigger.

Step three: repeating the step two, if the effective signal is still received, the signal is effective and the counter is + 1;

the number of repetitions is set according to the detection response time of the photoelectric switch.

B) Execution of output decision task

When the light receiver s1 receives a light signal, the signal acts as a trigger signal to start a decision cycle. If the effective signal count reaches the set value in one period, the light receiver is considered to stably receive the effective signals sent by the light projectors in the same group, and the light incoming state is output. The length of the judging period depends on the period setting of the two groups of light projecting pulses, and is reasonably set to be the least common multiple period of the two groups of light periods. Similarly, when the effective signal counter does not reach the set value in one period, the shading state is output.

In an embodiment of the present application, the method includes: and the signal capturing period of the light receiver is synchronous with the period of the light projecting pulse of the corresponding photoelectric switch, wherein the period of the light projecting pulse is used for the light projector to project light according to a preset period. Here, T1_2 is synchronized with T1_4, T2_2 is synchronized with T2_4, and the two groups of light emitters emit two groups of lights with different frequencies.

With reference to the timing diagram in fig. 3, the parameters in the timing diagram are set, as shown in table one:

watch 1

It should be noted that the setting of each parameter in the table i is only an example in an embodiment of the present application, and other setting of other existing or future parameters, such as may be applicable to the present application, should also be included in the scope of protection of the present application, and is hereby incorporated by reference.

In an embodiment of the present application, the first optoelectronic switch s1 is exemplified by the setting data of each parameter in table one, as shown in fig. 4. Step 1-step 2 are reference points of a determination period, and further, relevant data in the determination period are cleared, wherein the relevant data include the light projection state of the light projector and the number of effective optical signals, so as to eliminate accumulated errors, that is, all data need to be cleared after each determination period is finished, the implementation mode can be that a timing period is opened at the reference points, and signals enter in an interruption mode; a timer may also be started, with the timed period set at the least common multiple of the two groups of light projection periods. Step 3-Step 5: if a signal is received during this period, it indicates that the signal that previously caused the interrupt or start decision period is the same group signal. If not, the state is cleared and the decision cycle is restarted. The time setting of the capture window takes into account the time setting of the capture window, the pulse accuracy, the response time and the interference rejection. The longer the window time, the shorter the capture time, but the weaker the interference rejection.

Further, the method further comprises: and when the judging period is the least common multiple of the light projecting period of the first photoelectric switch and the light projecting period of the second photoelectric switch, if the optical signals of the light projectors in the same group as the light receiver are not received after 2 times of the time length of the judging period, abandoning the time sequence corresponding to the current capturing task, and offsetting the receiving time sequence according to preset time. As in loop1 of fig. 4, there are optimum and worst states in the actual determination for a loop cycle. And optimally, the initial phases of the two groups of signals are within +/-10 us, and the same group of signals are directly found without using loop 1. The worst state is when the same set of signals has just passed through at the capture point after the signals are triggered. Then loop1 cycles for N times the least common multiple of the period, and to avoid this, other algorithms are needed: that is, after 2 times of common times and weeks, no valid signal is received, the current capture timing sequence is abandoned, and the receiving timing sequence is shifted by a certain time to restart synchronization. In addition, increasing the capture window is also an effective way to reduce the capture time.

Continuing with FIG. 4, Step 6-Step 7: and after receiving the effective signal, closing the signal receiving channel and counting the existing signals. And resetting the decision period to ensure that the decision time of one decision period is ensured. Then, Step 8: and if the judgment period is not finished, each gate is finely adjusted, the loop2 is entered, and the same group of signals are continuously received. If the same group signal is not received in the middle, the initial state is returned through loop 1. Among them, ring2 is a time fine adjustment, which aims to reduce the difference of program running time caused by different program branches. Finally, at Step9, after the determination period is completed, whether the output is in the light incident state or in the light shielded state is determined based on whether the count value of the effective signal in the entire determination period reaches a set value.

In an embodiment of the present application, for example, assuming that the time periods of two pulses are 75us and 125us, respectively, after the s2 photo detector captures the s1 interference signal, the two pulses are at different phases

Under the poor condition, the light receiver captures the delay condition of its own signal, when

The time for the first capture is about 275 us; when in use

The time for the first capture is about 450 us; when in use

The time for first capture is about 600 us; when in use

The time for the first capture is about 750 us; when in use

The time for the first capture is about 900 us. Shown in FIG. 5

The timing chart of time and the timing chart of the other ranges of the phase difference are similar to those in fig. 5. Wherein the phase difference

The light incident signal of the s1 light receiver and the light receiving signal of the s2 light receiver are receiveds1 time difference of interference signal.

Through the method, the light projecting signal of the light projector is identified, so that the corresponding relation between the two sets of light receivers and the light projector is set to prevent mutual interference, the function of preventing mutual interference of the two sets of opposite-type photoelectric switches can be achieved, the defects of the existing opposite-type photoelectric switches are overcome, and the requirement that the two sets of opposite-type photoelectric switches can be installed in a close fit mode is met. It is also possible to reach areas where detection was previously impossible because of interference. Meanwhile, in the case of using a correlation type photoelectric switch, the interference is avoided by installing the light projector and the light receiver in a crossing manner, but the wiring and installation costs are increased.

It will be evident to those skilled in the art that the present application is not limited to the details of the foregoing illustrative embodiments, and that the present application may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the application being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned. Furthermore, it is obvious that the word "comprising" does not exclude other elements or steps, and the singular does not exclude the plural. A plurality of units or means recited in the apparatus claims may also be implemented by one unit or means in software or hardware. The terms first, second, etc. are used to denote names, but not any particular order.

Claims (6)

1. A method for determining a light projection state of a correlation-type photoelectric switch, the method comprising:

determining a determination period according to a light projection period of a first photoelectric switch and/or a light projection period of a second photoelectric switch in the correlation type photoelectric switch, wherein the first photoelectric switch and the second photoelectric switch respectively comprise a light projector and a light receiver, and the frequencies of light projected by the corresponding light projectors are different;

taking the first optical signal received by the light receiver as a trigger signal, and performing a capturing task in the determination period according to the trigger signal to determine the number of effective optical signals captured by the capturing task in the determination period;

comparing the number of the effective optical signals with a preset threshold value, and determining the light projecting state of a light projector in the same group with the light receiver according to the comparison result, wherein the light projecting state comprises a light incident state and a light shielding state;

wherein determining the number of captured valid optical signals of the capture task within the decision period comprises:

opening the width of a signal capturing door corresponding to the light receiver after the signal capturing period of the light receiver is passed, wherein the signal capturing period of the light receiver is synchronous with the period of a light projecting pulse of a corresponding photoelectric switch, and the period of the light projecting pulse is used for the light projector to project light according to a preset period;

and judging whether the optical signal of the light projector in the same group with the light receiver is received within the time of the width of the signal capture door, if so, determining the received optical signal as a valid optical signal, and counting.

2. The method of claim 1, wherein determining the decision period based on a light projection period of the first opto-electronic switch and/or a light projection period of the second opto-electronic switch comprises at least any one of:

taking the least common multiple of the light projection period of the first photoelectric switch and the light projection period of the second photoelectric switch as a judgment period;

setting a light projection period of the first photoelectric switch as a judgment period, wherein N is 1, 2,3 and … …;

and taking N times of the light projection period of the second photoelectric switch as a determination period, wherein N is 1, 2,3 and … ….

3. The method according to claim 1, characterized in that it comprises:

if the optical signal is not received within the time of the signal capture gate width, the previously determined number of valid optical signals is discarded and the trigger signal is re-determined.

4. The method of claim 1, wherein comparing the number of the effective optical signals with a preset threshold value, and determining the light projecting state of the light projector in the same group as the light receiver according to the comparison result comprises:

if the number of the effective optical signals is larger than or equal to a preset threshold value, the light projecting state of the light projector in the same group with the light receiver is a light incident state;

and if the number of the effective optical signals is less than a preset threshold value, the light projecting state of the light projector in the same group with the light receiver is a light shielding state.

5. The method according to claim 1, wherein the comparing the number of the effective optical signals with a preset threshold value, and determining the light projecting state of the light projector in the same group with the light receiver according to the comparison result comprises:

and clearing the related data in the judging period, wherein the related data comprises the light projecting state of the light projector and the number of the effective light signals.

6. The method of claim 2, further comprising:

and when the judging period is the least common multiple of the light projecting period of the first photoelectric switch and the light projecting period of the second photoelectric switch, if the optical signals of the light projectors in the same group as the light receiver are not received after 2 times of the time length of the judging period, abandoning the time sequence corresponding to the current capturing task, and offsetting the receiving time sequence according to preset time.

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