Winder RPM adjust

L

Thread Starter

LY

The winder diameter increases,I am trying to control Winder's RPM to maintain the Winder supply line speed constant.

a dancer exists between the Winder roll and main supply roll.

Any one can help me: How to control the Winder RPM and Dancer position to maintain the main supply line speed constant, I am using a PLC to control.

Thanks in Advance

LY
 
R

Robert Scott

If the supply speed is fixed, then the take-up speed of the winder should be controlled through a closed-loop (PI) controller, servoing for a fixed dancer position.

Robert Scott
Real-Time Specialties
Embedded Systems Consulting
 
C

california bob

This is a tricky loop. There are manufacturers of these controllers because in general a PLC does not have a fast enough update rate to handle the process.

http://www.contrexinc.com

Contrex has some nice dedicated controllers that will do this type of control.

Robert Trask, PE
Los Angeles, CA USA
[email protected]
 
Hi,
Winding a web is indeed a complex control. In this case I assume you are using a dumb drive in speed mode to control your winding tension.

First of all you need to calculate the unwinder roll diameter from the line speed and the unwinder speed. If you are able to get the diameter using external sensors, eg. potentiometers, ultra sonic or lasers then this has to be sent to the PLC.

As the roll gets bigger, the surface speed increase. This will cause a displacement in the dancer position. Use the dancer position feed back to influence the setpoint speed.

Depending on the orientation of the dancer, the tension can be controlled by means of weights, springs or pneumatic cylinders.

As pointed out, a reasonable fast PLC is required to implement the above. It would be easier to implement on a technological drive with the software blocks built in. eg. diameter calculation, ramps, setpoint influence, PID etc

I have done projects for unwinding and rewinding flexible webs down to 15u thickness using a PLC.

Hope it helps.
 
P

Paul Cunningham

On April 1, 2004, LY wrote:
> a dancer exists between the Winder roll and main supply roll.
>
> Any one can help me: How to control the Winder RPM and Dancer position to maintain the main supply line speed constant, I am using a PLC to control. <

I have ten yrs. experience with windup operations. I have found that ideal control can be achieved with a simple variable speed drive with analog input, an analog input from the feed loop or dancer bar, an analog input representing the feeding line speed and any PLC. If the operation involves a lining material (all of mine do), tension control can be maintained within 1/2 pound with relatively maintenance-free components.

> The winder diameter increases,I am trying to control Winder's RPM to maintain the Winder supply line speed constant. <

Scale your input, output, and control paramters:
LOOP_HEIGHT_ACT (actual analog input; ie inches,
millimmeters)
LOOP_HEIGHT_SP (setpoint...desired
maintained dancer position)
Create a couple of Booleans called LOOP_HEIGHT_MIN and _MAX if your line must stop and start or if your winder must stop and start, start partially filled, etc.

WIND_SPD_REF (analog output to variable speed
drive;same units FPM or MPM)
LINE_SPEED (ie FPM, MPM)

Calculate MIN_WIND_RATIO and MAX_WIND_RATIO: Calculate these based on physical dimension of "winding" diameter empty and full. Use values outside the range to allow the provided logic to ramp towards the setpoint in unusual situations like starting/stopping or starting partials. Now the F.M.C.

Use a PID with the dancer position (LOOP_HEIGHT_ACT) as the PV, LOOP_HEIGHT_PV as the setpoint and a variable called WIND_RATIO as the output or CV; YOU MUST RESCALE IF USING AN INTEGER BASED INSTRUCTION. Set up this PI(D) with output limits such that WIND_RATIO will always be within the MIN and MAX calculated above. The PID instruction is now a RATIO DETECTOR.

Compute the speed output like this:
WIND_SPD_REF=WIND_RATIO*LINE_SPD+(OFFSET)
OFFSET is used for manual and when the LINE_SPD

The offset is used for jogging or to get the winder moving when the dancer is full and the feeding line is halted *because* the dancer is full!

You must tune the PID "hot" enough to deal with whatever situations your line encounters during normal production. If the winder must stop and start the gains may need to be higher, and the PID calculation should be halted while it is stopped. Remeber, the RATIO DETECTOR PID can't find a parameter that it cannot AFFECT! The gains should be as low as possible. Ideally the position of the dancer will ramp smoothly and directly to the setpoint and not overshoot much at all during a line start. This makes liner tension control much easier. If it takes too long to get to the setpoint at the start of a roll, increase the P and I gains slightly. If the loop height is not constant at steady state speeds, thee gains could be too high and check the ACCEL DECEL parameters of your motor contoller(s). Mismatched drive responsiveness will cause the dancer position to dip or climb while the line is decelerating. I have systems running up to 100YPM, diameters from 12" to 48", and the loop height stays within 1" of the setpoint while running or ramping slowly between line speed settings (3-10 second ramps) and within 2" while stopping and starting rapidly (1 sec accel and 1/2 sec decel from about 50YPM) with this logic! Make sure the LINE_SPD parameter is accurate during accel/decel cycles. I usually do all my ramping in the PLC and set the drives' ACCELs and DECELs to near identical values as low as practical for the process.

[email protected]
 
The actual line is for producing the rubber sheet.
System:

main roll controlled by one DC motor and this speed is refer to main speed.
Following a roll with load cell on it.
following a cooling roll controlled by one DC motor
following accumulation station with pressure control to adjust low and high.
Following (1)winder tenstion control roll by one DC motor
Following (2)winders control by (2)DC motor, same function.

The program was very old and no one knows in the engineering/maintenance group.

Can u help me to understand/explain how this system control the winder tension and line tension?

Thank you very much,

Ly
 
S
Use a tacho or encoder driven by roll surface for speed feedback. Alternately use a ultrasonic ranger to measure roll diameter and calcullate N winder roll rpm by formula V/PIE*D and use this as reference input to drive. Use the DR to control the trim the speed of the preceding drive.
 
Top