Практика Shadowing: PLC State Machines Explained - Изучайте разговорный английский по видео
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Hello and welcome back to the channel.
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In today's video, we're going to cover a super important concept in the world of PLC programming, controls programming, called the finite state machine, or sometimes just state machine.
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In a very basic setting, sometimes a state machine is also just considered like a sequencer or sequential logic.
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They overlap a little bit in small systems, but when you get into large,
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complex systems, a state machine is really like a hierarchy or a fundamental way of structuring your code that is super scalable,
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easy to debug, easy to write additional code onto.
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one together.
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Okay, so let's talk about a very simple example of something that we could create a state machine to control.
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And let's take a look at an industrial setting.
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Okay, we have a tank, right?
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We have some vessel that we want to be able to fill with material.
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And then we want to be able to blend it and mix it up.
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And then we want to be able to drain it and discharge material.
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So I have all the IO, all the inputs and outputs used in this system shown here.
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We're going to have a fill valve that will gravity feed raw material in.
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We'll have a high and low level sensor, just digital inputs that tell us there is material in the tank at different levels
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so we can see if we're below a low level set point or above a high level.
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We'll actually have a mixer, kind of like a mixer descending into the tank to blend the material, and then we'll have a discharge valve that will also be gravity fed.
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So we're not going to worry about pumps or things like that to
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case and let's talk about how we want this system to operate normally okay
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so we want the tank sort of sitting there waiting for a command someone would hit start
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On an HMI or a push button doesn't really matter someone says okay start a blend and
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and the system will check make sure everything's good no faults we're ready for
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that command we're going to start by opening the fill valve until high level is reached
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and then starting the mixer mix for some set point desired
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and then we'll stop the mixer open the discharge valve
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and once low level is reached then we'll close the discharge valve and return to idle okay so
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conceptually you can see how this might make sense if you've been in industry or in a chemical plant
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They are very simple.
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It's like raw material in sometimes an operator will put a couple cups of additives in the top
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or you use little diaphragm pumps for dosing.
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You'll blend it up and mix it and then you'll send it on its merry way to go get packaged out.
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So this is a very realistic real world scenario.
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Now to program this in a logical way, a well documented, well structured way.
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We want to create a state machine for it and state machines, broadly speaking, are defined by states and transitions between states.
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Okay?
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So for this system that we've just described, the states could effectively be idle, it's sitting there not doing anything,
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filling where the mixer is off and the discharge valve is closed
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and only the fill valve is open and the tank is building up its volume of raw material.
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And then mixing where it's blending, no new materials coming in, no new materials going out.
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We're just mixing and blending and then draining where the mixer's off, the fill valve's off, and we're just letting the blended material leave.
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And then another state to think about is if something goes wrong, like the mixer fails to start or a valve gets stuck open,
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that might go into alarm state.
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So here shown in kind of the blue bubbles are what you could think of as the states.
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schematic I'm showing here is known as a state transition diagram
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because you're defining the states and the transition events
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that take you from one state to another right so
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when you're sitting there in idle the only thing that's going
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to take you out of idle the way I've described the
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system would be someone pressing the start button you could have an automated system where just like high level
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or replacing a tote or something automatically triggers a fill,
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that's a transition from the idle state to the filling state.
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Now if I'm in filling and something bad happens, I might need to go into alarm state.
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But if a person says this was a mistake, call it off, and they hit the stop button, I might just go right back to idle.
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But in normal circumstances, I've hit start, I've started a fill, and I've reached high level,
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then I will transition from the filling state to the mixing state.
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Here, once low level is reached, I'll go back to idle.
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So a normal operation flow is idle.
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Someone presses start.
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I fill to high level.
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I mix for a desired set point.
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And I drain to low level.
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But you can see just in this one tank, 5IO point, simple system, how these state transition diagrams also capture a lot of unique edge cases.
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And the PLC programmer needs to be thinking about these edge cases when they write the code for it.
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diagram actually does not look too different from an IEC 61131 PLC programming language called SFC or sequential function chart.
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Sometimes I think mislabeled sequential flow chart,
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but it actually is a programming language that uses this concept of states and transitions similar to this.
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It's not common in PLC programming.
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Far more common is ladder diagram and structured text.
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So we're going to stick with those.
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But it is worth calling out that that is basically what an SFC is, is a document of the states and transitions between the states.
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And you need to write lower level code to actually automate the system.
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Okay, so enough PowerPoint engineering.
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Let's take a look at what this actually means in a PLC program.
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And because it would probably take, you know, hour to write together,
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I'm going to go ahead and talk about the state machine that I have already written and walk you through it.
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So let's go to main.
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The main PLC let me close this side by side real quick.
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Okay, and
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so what I have set up ahead of time for this
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Demonstration is something to handle the basic states something to simulate as
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if we had these inputs and outputs This isn't a hardware tutorial
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So I'm not you know actually standing up a tank in my garage to show you guys this
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and then I have that running logic that normal sequence built Okay, so that's all that's in Maine.
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Let's go to state handler, right?
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at my main states and the things that could transition between primary states
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so active just not being true me not being in sequence
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is going to say I want to be in zero I want to be an idle
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running will be our main control code this is where the things are happening that'll be
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when someone hits the start command we'll start it up we'll say we're in active we're in run mode
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One quick just sort of syntax thing, it's not a good idea to program yourself into a corner when you're doing PLC programming.
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So when you're setting up a program initially for a small system, maybe you want to take jumps of tens rather than individual integers.
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When you're doing a large system, maybe you would want to go from zero to 100 to 200 or 1 ,000, 2 ,000, 3 ,000.
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added, sometimes you want to add a step that's actually halfway between idle and running, right, like a startup sequence,
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and maybe you want to make that five or something so that these numbers still make sense and are sort of sequential.
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So that's why this is zero to 10 and not zero to one.
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It's just sort of like a programmer's delight sort of feature.
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But anyways, so we have running, stopping, and alarmed or faulted, okay, those are kind of what you could think of as like your
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modes and then we'll go into running
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and we'll take a look at what actually happens
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when we enter running
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so someone has hit start we've entered active first thing we do is we check are there no active alarms
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if there are no active alarms let's go start a fill
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if there are active alarms let's go to that mode 30
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and let's sit there until someone clears them or acknowledges them
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Now we're in mode 11 right which is just right after starting up the running sequence.
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Now we're in filling and we're going to open the fill valve until we reach high level.
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And then once high level is reached we're going to move to step 12 and step 12 is going to be mixing.
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Here we're going to start the mixer and again
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if you've been following along with the PLC programming tutorials on the channel you already know this.
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the fill valve just once this condition is no longer true the fill valve will shut
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so these momentary coils imply if I'm in step 11
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and I don't have high level open the fill valve
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but it also says if I'm not in step 11
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or I do have high level close the fill valve so
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that you implicitly get that code for using these momentary coils hopefully that's clear go watch the
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previous tutorials if
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if you're unfamiliar with why we don't need to also command the fill valve to close okay
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but now moving on to look at the mixing step again
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we're turning on the mixer we'll wait to watch for mixer feedback
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so this is a very common convention in digital outputs for motors
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or pumps is you command a plc output to turn on a pump
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or motor but usually that chunk some big motor contactor pulls in
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and you want feedback off of that contactor that it has and pulled in.
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So other than just looking at the output and saying is the output on ideally, you'd actually be looking at a feedback on that contactor that says, Yep, it pulled in.
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And now I'm counting up in timing.
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That's a normal source of alarms and faults is like, Hey, I commanded this output to turn on, but I never got feedback that the contactor pulled in.
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And anyways, then we're going to time for some set point, I have one minute in there right now, this could be a
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I just have one minute in there and when
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that timer finishes we'll go to step 13 similar to the
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valve we won't need to tell the mixer to turn off
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it will just turn off once we're no longer in step 12.
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Step 13 will be draining it looks exactly like filling
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but now we open the drain valve until low level is met
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and then when low level is met we're going to turn off the active bit
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and we're going to go back to step 0 which is idle.
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Okay so that's the normal sequence of events and you can see how handles this little discrete chunk of logic.
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And it's really easy to see how from an HMI or a monitoring system of any sort,
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you can always know exactly what your code thinks it ought to be doing just by looking at this one tag.
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This one mode tag will tell you exactly what it should be trying to do
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and what state it should be in right now.
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This is a lot cleaner than a world of dozens of
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Find what mode currently is and you go look at what it's trying to do in that specific step.
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Now, because this is a software setup and I don't have all this physical IO, I'll walk you through the sim logic I have here really quickly.
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When fill valve is open, I have every 500 milliseconds, so twice a second, I have add one to tank level,
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just this integer value that's tracking the tank level.
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fill and tank drain.
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And then when the mixer turns on, I today tell the feedback to act as if that worked properly.
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And then when tank level gets above 75, we say, okay, we have high level when it gets below 10, we say we have low level.
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So that's the that's the simulation logic I've built so that we can test this sequencer.
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All right.
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So let's actually walk through what this looks like.
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And then we'll just close the tutorial real quick.
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So we're sitting here in idle system is just chilling.
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Everything seems okay.
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Nothing's faulted.
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A person comes along and hits a start button.
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Now I go to step 10.
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Now I move into step 11.
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I'm in running.
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And if I go in and monitor my running logic, you can see we're sitting here with the fill valve open, waiting for high level to be reached.
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So if I go over to my sim logic, you can see the tank level is rapidly counting up, it's counting up twice per second.
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So we'll hit 75 in no time.
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But if I had an HMI setup for this, and you know, we'll do some HMI tutorials on the channel soon, it would say, you know,
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a graphic of the tank that is showing the volume counting up.
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And then it just hit 75.
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So now we're in mixing and you can see our mix timer is counting up the fill valve closed.
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The level is holding at 75, which is what it filled to there.
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And in 45 seconds, we're going to finish this mix timer.
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And here you could is a good spot to say like you have the main logic of what you want to
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this code is like what's a common issue you could have
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at this step it would be like the mixer is being commanded to be on
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but i don't have mixer feedback for five seconds
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or one second like i gave the contactor a chance to pull in
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and relay that back to the plc and
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so you could have a oh i commanded the mixer to start
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and i didn't get the feedback in that case i want to go to my
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when everything's good and we get the feedback, we count up to 60 seconds, we get to our drain state.
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Now the mixer's off, the fill valve's off, and all the system is trying to do is drain until we get low level.
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We can see the level hurtling down now, kind of opposite of the filling step that we were just in.
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And in a couple of seconds, we'll be at 10, which will trigger our low level indication, and we should go back to idle, right?
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So this very simple logic actually would let us completely automate a filling and draining sequence.
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And it all goes back to there.
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There we go.
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We hit 10.
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Okay, so we should be back in idle.
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All right, we hit low level, it moved to step zero, and it reset active.
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And now everything is just chilling, waiting for commands and transitions.
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It all goes back to being able to
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writing the PLC code to actually do the thing is relatively trivial
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and there are great ways to go through step by step
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and check for edge cases
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and of course it gets more complicated as you get into dozens
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or thousands of IO points and large interconnected systems with DCSs
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and SCADAs but if you can take every system and subsystem back to a state transition diagram and say what
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move me from filling to mixing to draining, then you can create well -structured, easy to debug, easy to program PLC code.
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And a big thing in our industry in controls
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and automation is writing code for the next person who has to work on that system.
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Over decades, it's very unlikely that one person will be responsible for all of the control code for a facility.
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programmers and people working on a system what you were thinking when you created that system.
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Okay, so like I said early on in the video, in a smaller system like this one I've demonstrated here, creating a sequencer where you just say like,
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I'm in step 10, 11, 12, 13, is not super different from a state machine.
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When you get to very large systems, you often have like zones of control that
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have a mode that says I've gone from you know idle to fill
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but you'll have a new like sub step
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or sub mode that's like command all the valves to do a thing
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and they'll all be sub functions inside of the fill sort of master mode control
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so state machines can actually have state machines nested inside of them it gets very complicated at very large systems
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but if you're able to break it down doing.
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So I hope you found this useful.
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As always, if you have questions about what you saw in this video, feel free to ask them in the comments below.
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Please consider leaving a like on the video and subscribing to the channel.
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And let me know what you want to see more of on the channel next time.
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Thanks for watching and see you next time.
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Thanks.
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Bye.
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Зачем практиковать разговорный английский с этим видео?
Практика разговорного английского на основе видео, подобного этому, позволяет вам не только лучше понимать технические концепции, но и развивать навыки устной речи. Когда вы слушаете и повторяете за носителем языка, вы способны улучшить произношение английского и увидеть, как используются выражения в естественных контекстах. В данном видео представлено объяснение концепции машин состояний, что помогает не только расширить ваш словарный запас, но и укрепляет уверенность в разговоре на технические темы.
Грамматика и выражения в контексте
Основные структуры, используемые в этом видео, включают:
- Сложные предложения: Использование вводных слов для объяснения последовательности действий ("Когда вы сидите там в режиме ожидания..."). Это помогает создавать ясные и логичные связи между идеями.
- Пассивный залог: Часто используется для акцентирования внимания на действии, а не на том, кто его выполняет ("Материал будет смешан"). Это полезно в формальных ситуациях и технических обсуждениях.
- Модальные глаголы: Подобные "можно" и "должен" помогают описать обязательные действия в различных состояниях машины и могут быть полезны в контексте программирования или управления, например, "это должно быть сделано" или "можно ожидать".
Распространенные ловушки произношения
При изучении английского языка с помощью видео могут возникнуть определенные сложности с произношением. Вот несколько трудных слов и фраз из видео:
- "state machine" (машина состояний): Обратите внимание на четкое произношение обеих частей, чтобы избежать путаницы с другими терминами.
- "blending" (смешивание): Это слово имеет несколько слогов, и важно правильно акцентировать ударение для лучшего звучания.
- "discharge" (выброс): Иногда произносится с акцентом на второй слог, что может затруднить понимание.
Используя видеоуроки, такие как это, вы сможете эффективно учить английский с YouTube и укрепить свои навыки через shadow speech, повторяя за носителями языка. Регулярная практика поможет вам улучшить произношение и уверенность в разговорной речи!
Грамматика в этом видео
Конструкции, которые говорящий использует чаще всего, с точными словами из видео:
| Конструкция | В видео |
|---|---|
| Present Perfect have/has + причастие прошедшего времени — прошлое действие, важное сейчас | you've been · we've just described · I've described |
| Пассивный залог be + причастие прошедшего времени — важно, что происходит, а не кто это делает | is also just considered · is reached · are defined |
| Придаточные определительные who / which + предложение — уточнение о человеке или предмете | right which is · person who has |
Что такое техника Shadowing?
Shadowing — это научно обоснованная техника изучения языка, изначально разработанная для подготовки профессиональных переводчиков и популяризированная полиглотом доктором Александром Аргуэльесом. Метод прост, но эффективен: вы слушаете аудио на английском от носителей языка и немедленно повторяете вслух — как тень, следующая за говорящим с задержкой в 1–2 секунды. В отличие от пассивного прослушивания или грамматических упражнений, Shadowing заставляет мозг и мышцы рта одновременно обрабатывать и воспроизводить реальные речевые паттерны. Исследования показывают, что это значительно улучшает точность произношения, интонацию, ритм, связную речь, понимание на слух и беглость речи — что делает его одним из самых эффективных методов для подготовки к IELTS Speaking и реального общения на английском.