Open Loop / Synchronized Conveyors 1

[mtrs]

We have three conveyors that are driven by one jack shaft. We would like to install three individual variable frequency drive and motor systems and continue to synchronize these conveyors with an open loop control.

Has anyone done this successfully?

 

[rhatcher]

Yes, this can be done. By "open loop", I take it to mean that you do not want to utilize feeback devices like encoders or tachometers. With a standard variable frequency/
variable voltage drive you could expect open loop speed accuracy of about 5-7%, with an open loop vector drive you could get down to 1% or so if everything is matched. That should be plenty for your application. I am using ballpark figures here and a general case. If you need specific info the manufacturer specifications will provide that or someone in this group may if you provide more specific information.

 

[don01]

I agree with Rhatcher that yep you can use an open loop control scheme. The numbers given are well in the order you should expect.
BUT why??
Ensure that your application has some slippage and can tolerate some variation.
You have used the name 4 wheeler so take the analogy of a 4 wheel drive running on a sealed road. If there is a variation between front and rear wheels then something snaps.
The use of closed loop control provides some feed back and if tuned carefully will ensure you do not distort a "rigid product" like steel or paper.
If you are conveying material like ore or coal go for open loop.

Regards Don
Ps to be very very very pendantic you cannot syncronise in open loop ie no feed back = no synch

 

[jbartos]

Suggestions: Notice that
1. Encoders may be used in the "open loop" control as speed sensors and directly control motor speed. Two dependent motors on the third one could use encoders/speed sensors. One motor may be without any sensors.
2. Assuming a belt conveyor, even small difference in the roller surface speed and belt linear speed will cause friction and belt wear.