Siemens 6RA80 DCM Drive

[plcengineer]

I have a new Siemens DCM Drive and I need to know how to make it run Forward Only. I can do this if I turn the torque to 0 but I need the negative torque to decel fast. Is there a parameter that I need to turn on? I want to use the negative torque to ramp down and then when speed == 0, disable run in reverse..The issue that I am having is that when I ramp the drive down quickly, the roll stops but then starts turning reverse.. I need it to just stall and only run forward

 

[plcengineer]

This DCM is a 4Q

 

[plcengineer]

The drive is running in torque mode on a winder. We are controlling tension and when the tension goes above the setpoint, the drive reduces torque and then runs in reverse. How can I let the motor just hold the stall position without running reverse? Any assistance would be appreciated.

 

[JRW]

Can you post the Starter file?

 

[plcengineer]

JRW,

I tried to attach the starter file and it is too large for the site. It has a Winder DCC chart in it so I assume that is why it is so large.. Or, is there another way to compress it with Siemens? The archive was 622Kb and I think the site is limited to 380Kb or something like that..

 

[JRW]

So from starter if you file>archive >
And zip


With only that drive
Still too large?

 

[JRW]

Your right!
Even zipping it is too large

Try this
see pic

then zip the export

I tested and I will get the dcc chart

 

[plcengineer]

JRW, I did the export and then I created a .ZIP File.. Please see the attached.. Thank you so much for the help..

 

[JRW]

plcengineer

Your running in mode 3, that is speed control with a torque limit for tension control

So I would try to adjust p50513 (neg direction of the speed controller)

Be careful because a 0 may not be a safe value to use

see screenshots

Let us know how it goes

 

[plcengineer]

Thanks.. Yes, it did work.. Also, I had to end up making sure I had more positive torque than negative to keep it from spinning reverse on me.. I am trying to tune the tension loop and it is quite a challenge.. Any pointers on that? I have never used DCC Winder before.. It seems that when I make a change to the Kp, I, add D, I still have the same issue.. I can run the spindle in tension mode and simulate the setpoint/pv and everything appears to work ok.. If the PV goes above the SP, the torque starts to taper off. However, when I have a web running in the machine, the spindle will turn, stop and turn again.. When it stops, we get slack and then the spindle speeds up to get it and it just starts oscillating.. WE have a small roller with a load cell and then the web goes to a Nip roller before the winder.. I am trying to control tension to the nip.. I tried to follow all the steps in the DCC Winder Manual but this one is kind of a challenge.. The winder drive is producing speed but I think the torque is going too low when we get too much tension.. It is almost like I need a min torque.. I tried raising my torque limit values and I was able to get rid of the oscillation but then the torque was too high and it made a hard roll.. Any advice would be appreciated and thanks again for your expertise..

 

[Manglemender]

Edit. Ingore my waffle. I see you are using the internal drive functions.

Your problem seems to be that you are not accurately controlling tension rather than any problem with the drive. I'm guessing that you are trying to control this entirely with a PID loop but you probably need to calculate the required torqe and set the torque limit (and speed setpoint) accordingly.

Total torque requirment is made up of: Tension component + inertia component +-friction losses

Tension torque is easy enough to calculate as tension required(N) * Distance (Radius) (M) = NM

Friction loses are static friction pluse dynamic losses (speed related) and may be added or subtracted depending on your torque direction.

Inertia is generally made up of two parts: a constant part relating to the mechanics and a varialbe part based on roll diameter. Calculate inertial mass then multiply by accelleration in radians/S

Based on whether your total torque is positive or negative you would then set an overspeed or an underspeed so that the drive can generate torque in that direction.

You make no mention of the mechanics: motor sizes, gearboxes, line speed, accell rates etc. this may help people understand your problem. You may be better off trimming speed to control tension rather than torque.

Maybe I'm over-thinking this and you are trying to do everything in the drive? Have you set up the diameter calculator?

One other thing to note: Ensure that the speed and current loops in the drive have been setup adequately before you start trying to make tension control work as you have two integral functions: one in the speed loop and one in teh PID.

Nick

 

[JRW]

plcengineer

I'm with Nick, Have you turned off/disabled the tension controller and tuned the drive?

What did you adjust ?

Also, did you set up a trace and how does it look?

Adjust and tune the speed controller (load maybe a half to full roll)

Then work on the tension control loop (this part is in dcc parameters)

 

[Manglemender]

Whilst were on the subject of drive tuning, The current loop autotune should be OK but I wouldn't advise doing a speed loop autotune on any drive that has a variable/high inertia. You will likely get a better tuned drive by doing it manually with a half sized roll (as suggested by JRW).

How is your inertia match (ratio of motor inertia to load inertia): A typical servo sytem may have an inertia match o <10:1 but a winder is never that good and can be 100:1 quite easily becuase of the variable load. The inertia of the motor should be in the spec sheet. calculate load inertia at maximum roll dimensions and then refelected inertia is the square of the gear ratio so if you have a gear ratio of 2:1 then the reflected inertia is 1/4 of the load inertia.

Nick

 

[plcengineer]

Thanks.. Yes, I have did the autotune for all the loops as well as the friction compensation.. I used watch tables and traces to review setpoints vs pv's and to follow the step changes... The issue seems that the winder speed torque setpoint isn't changing fast enough.. However, I have changed the Kp, I in the speed controller to see if I can see it react faster.. I have the ramp-up down settings in the drive set so that we can ramp up/down quickly.. I have tuned in the tension loop as well Kp, I as well but it seems I can't make the spindle ramp up/down quickly.. I have changed the RFG input but I read in the manual that the winder speed comes from an internal RFG and I am not sure what that is.. I have changed all the settings in the RFG but I can't seem to get the spindle to ramp up/down quickly.. Now, when I press the start/stop buttons, the ramp up down times react really fast.. If I could get that response when I am running tension, I think I would be fine..

We have a 15:1 gear ratio with a 7.5 HP motor.. We are using the diameter calculator in the DCC Winder program.. It works really well..

 

[Manglemender]

I'm not very familliar with DCC and it's been more than 10 years since I last used it but studying the DCC winder control it looks pretty good.

If you did a speed loop autotune with no roll in the winder then the gains will be too low. If you did a speed loop autotune with a roll on the winder then the gains could be anywhere. As a starting point you may wish to take the default values then double the P gain and half the intergral term.

Controlling tension with a load cell and a high rate of change of speed is going to be tricky. On the assumtion that everything is stable at steady speed and only speed change causes a problem then, most likely, you need some inertia compensation. I can see that this is available but have no idea what it looks like in the drive.

One other thing to check is that all of your scaling factors are correct for speed and tension etc.

While I think of it, If you find that different gains work better for different sized rolls/ speeds then the gains can be profiled.

Good luck,

Nick