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In need of more speed ?


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Hello

I have been testing this program using a drill with 4 screws per cycel and the drill runs at 50 rounds per sec. With the 4 screws the high speed pikup counts 200 per sec!

I have tried to have 8 screws but the high speed counter ( IM18-08NPS-ZUK from SICK, Ia = 300mA,DC 10-30V, fMax = 1000 Hz ) Stopps counting at a speed of 230 counts per sec. Some how i think we have reached the limitation of the v350-35-T2 oplc and it is not the high speed conter thats is the problem.

I feel that the pid controler is not reacting fast enough to the changes i implement.

Any ideas or some tips on the ladder ?

Kind regards

Hjalli Sig

PIDcontroler-ver1.vlp

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The input frequency of the HSC on a V350-35-T2 is 30 kHz for short cables, so you're not exceeding the unit's capability. I looked at your program and the input is correctly configured. You need to get the input working right before you start worrying about the PID block.

Could you make a sketch of your sensor setup with dimensions of the screw heads? You're using an 18mm sensor that is pretty large for this kind of application. Depending on how you're sensing the rotation, your target may be too small at higher RPM for the sensor to pick it up. If the maximum frequency of the sensor is 1000 Hz, then the target must be in front of the sensor for at least 1 ms. Do you have access to an oscilloscope to see what the electrical signal from the sensor looks like?

You probably need to choose a smaller sensor with a size that matches the screw size, or use a belt to connect an encoder with a 10 PPR output.

Joe T.

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The input frequency of the HSC on a V350-35-T2 is 30 kHz for short cables, so you're not exceeding the unit's capability. I looked at your program and the input is correctly configured. You need to get the input working right before you start worrying about the PID block.

Could you make a sketch of your sensor setup with dimensions of the screw heads? You're using an 18mm sensor that is pretty large for this kind of application. Depending on how you're sensing the rotation, your target may be too small at higher RPM for the sensor to pick it up. If the maximum frequency of the sensor is 1000 Hz, then the target must be in front of the sensor for at least 1 ms. Do you have access to an oscilloscope to see what the electrical signal from the sensor looks like?

You probably need to choose a smaller sensor with a size that matches the screw size, or use a belt to connect an encoder with a 10 PPR output.

Joe T.

Hi Joe, only issue I see with your concerns about screw dimensions is that he increased the speed by simply doubling the number of screws used. Thus, at the same rotation speed and all other things being equal it should have picked up the 8 screws just as well as it should have picked up the 4 screws from an individual timing standpoint. If I understand him correctly he didn't change the RPMs, just the number of screws per rev.

Hjalli, where are you reading the input? Are you looking at the raw value or scaled value?

When you say it "stops counting" are you saying it pegs at 230 or drops to 0?

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Hi Joe, only issue I see with your concerns about screw dimensions is that he increased the speed by simply doubling the number of screws used. Thus, at the same rotation speed and all other things being equal it should have picked up the 8 screws just as well as it should have picked up the 4 screws from an individual timing standpoint. If I understand him correctly he didn't change the RPMs, just the number of screws per rev.

Hjalli, where are you reading the input? Are you looking at the raw value or scaled value?

When you say it "stops counting" are you saying it pegs at 230 or drops to 0?

It looks like i was to quick to post this, i only needend to posission the counter slightly better than til all worked.

Do you know a easy way to exclude the D-factor on the PID-controler with autotune?

I know for a fact that in speed control systems like runing a govinor on a diselengine the PI - control is only used.

Joe : i will post a pic soon

Damien : im looking at the raw value and it rises about 15 % when a hevy lode is lifted from spining drillhead, the dutycycle is running constant aprox 20 % then i implement load on the drillhead, then the pid-controler reacts and prolongs the dutycycele up to 100% to keep the speed upp. This works until a release the load from 100% to 20% then the speed will rise 15% over the set value.

regards Hjalli

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