Do-more H2 (Micro Modular PLC) Videos

Hide Transcript

View Transcript

Dynamic Position is very similar to the Absolute

positioning of the Trapezoid instruction we looked at in a previous video. You tell the carriage what position to go

to and it does. The main difference is this instruction gets

triggered a little differently and you can change your mind mid instruction. That is, you can tell it to go to position

A, and while it is enroute to that position, you can change the destination to position

B and it will abort A and immediately head towards B. Dynamic Position even works if you have already

passed the destination: For example, If we specify a new destination that the carriage

has already passed, back here for example, Dynamic Position will ramp down. Reverse direction and head back and try and

find that new destination via the configuration profile. Exactly what you would expect it to do. Let’s do an example. We’re going to use the same config block

that we used in all of the previous videos – see those for an explanation on that. On the next rung I have the Dynamic Position

Block. I’ve already put it in here to save us some

time, so let’s go take a look at it. All we do is select the module we want to

talk to - of course we only have one in this system. Do we want to zero out the position when we

first call this routine? We do for this example. And we give it the register we want to use

for the target position. These little reminders are telling us that

once this instruction is enabled, you have to set the dot gotoposition bit to start the

move. We’ll see that in just a second. This instruction will clear that bit when

the move begins and once it does, you can go set it again to change the destination. We’ll enable that instruction with X7, and

we’ll suspend it with X6. So just like those notes in the instruction

said … once we enable this instruction, nothing happens. You actually have to set this gotoposition

bit on our device to get things to move. We’ll use the rising edge of X0 to do that

in our example. To help us with this, I’ve added a few more

instructions here. Any time X1 gets set, we are going to change

our destination register to 0. X2 will change it to 100,000. X3 will change it to 200,000. And X4 will change it to 400,000. That way I can very quickly change directions

while this thing is running. So let’s accept all of these changes. Save it to the disk and write it to the PLC. So, let’s see .. D0 is currently set at

200,00. Let me change that. I’ll flip X4 and D0 got changed to 400,000. Perfect. So when we run this example, what’s going

to happen is the position will get cleared out via our config, so the carriage will be

starting from position 0. I’ve already setup the destination register

with 400,000. And I’ve enabled the instruction. To get things moving, all I have to do is

flip X0. Before we do that, let’s come up with a

plan here. We’re going to head towards 400,000. When the carriage starts moving, I’m going

to quickly flip X2 to put 100,000 in our destination register. After I’ve done that, I’m going to flip

X0 again to kick off that new target. So what we should see is the carriage heads

towards 400,000. While it is enroute I’ll change the destination,

set X0 and we should see the carriage ramp down and then ramp back up and head back towards

100. Let’s try it. Here we go.. I’m going to kick it off with X0. Change the destination, kick X0 again, watch

the carriage change its mind and head back. I’m going to change the destination to zero. Kick that off, and try it again. Change our destination to 400,000. Kick it off. Change it. And back it goes. So again, with the Dynamic position command

you can change the position at any time, even while the carriage is moving. The Dynamic Velocity command allows you to

ramp to a specified frequency AND it allows you to change that frequency at any time dynamically. The good news is you don’t need to toggle

a bit with this one though. All you have to do is change the frequency

and it will follow. We’ll, That’s all there is to implementing

motion using the DYNP and DYNV instructions. Be sure to check out the other videos in this

series for more on using motion. And as always, please send us any comments

you may have, we appreciate the feedback. Spend Less. Do-more. From AutomationDirect.