Andrew Evenson
Member
View attachment 36685Hi all,
Have a quick question about starting and stopping a PowerFlex 70. In my application, I am trying to position the lead of a metal strip via a set of pinch rolls - an encoder is being used to track lead position, am sending a speed reference to the drive (Outer Loop is postion, inner loop is speed) All is working fine, but some times I have issues decelerating, the drive doesn't follow the reference near the end of the reference ramp.
The original programmers of the system basically set the "start" bit whenever the speed reference is <> 0 and pulse the "stop" bit when it is zero again.
What I really need to do is decelerate to zero speed and then set the "stop bit". Currently I am not at zero speed, but my reference is, therefore the "Stop bit" is being set and the drive coasts.
I had seen Ken Roach's solution to start/stop requests in the following post:
http://www.plctalk.net/qanda/showthread.php?t=46728&highlight=powerflex+70+start
Is my best bet to sequence this the following:
a. If "Move Request" Then Set "Start Bit" Until "Active Bit"
b. Release Speed Reference to Drive - Ramped S-Curve
c. Bring Speed Reference to Zero
d. Wait for "Drive Speed Feedback =0
e. Pulse "Stop Bit"
I have attatched a screen shot of the speed/position control, sorry, looks choppy, but will have to do, the reference and speed feedbacks are not really the rough. Yes, you do see a negative speed reference and a positive incremental strip position, that is correct for the roll configuration.
Sorry it is blurry, didn't look like that when I took the screen capture..
Red Boolean = Stop Bit
Green Boolean = Start Bit
Yellow Boolean = Drive "Ready" Status Bit
Blue Boolean = Drive "Active" Status Bit
Green analog Trace = Speed Ref
Red Analog Trace = Speed Feedback
Purple Analog Trace = Integrated Strip position
Does anyone know why the "ready" status bit drops out?? What constitutes the "ready" and "active" status bits. Looked in the manuals and didn't get a good clear explination.
Any advice would be much appreciated.
Thanks,
Andrew Evenson
Have a quick question about starting and stopping a PowerFlex 70. In my application, I am trying to position the lead of a metal strip via a set of pinch rolls - an encoder is being used to track lead position, am sending a speed reference to the drive (Outer Loop is postion, inner loop is speed) All is working fine, but some times I have issues decelerating, the drive doesn't follow the reference near the end of the reference ramp.
The original programmers of the system basically set the "start" bit whenever the speed reference is <> 0 and pulse the "stop" bit when it is zero again.
What I really need to do is decelerate to zero speed and then set the "stop bit". Currently I am not at zero speed, but my reference is, therefore the "Stop bit" is being set and the drive coasts.
I had seen Ken Roach's solution to start/stop requests in the following post:
http://www.plctalk.net/qanda/showthread.php?t=46728&highlight=powerflex+70+start
Is my best bet to sequence this the following:
a. If "Move Request" Then Set "Start Bit" Until "Active Bit"
b. Release Speed Reference to Drive - Ramped S-Curve
c. Bring Speed Reference to Zero
d. Wait for "Drive Speed Feedback =0
e. Pulse "Stop Bit"
I have attatched a screen shot of the speed/position control, sorry, looks choppy, but will have to do, the reference and speed feedbacks are not really the rough. Yes, you do see a negative speed reference and a positive incremental strip position, that is correct for the roll configuration.
Sorry it is blurry, didn't look like that when I took the screen capture..
Red Boolean = Stop Bit
Green Boolean = Start Bit
Yellow Boolean = Drive "Ready" Status Bit
Blue Boolean = Drive "Active" Status Bit
Green analog Trace = Speed Ref
Red Analog Trace = Speed Feedback
Purple Analog Trace = Integrated Strip position
Does anyone know why the "ready" status bit drops out?? What constitutes the "ready" and "active" status bits. Looked in the manuals and didn't get a good clear explination.
Any advice would be much appreciated.
Thanks,
Andrew Evenson