adccommunitymod (AutomationDirect) asked a question.
Master/Slave Speed
Created Date: August 22,2005
Created By: Mr. Jeff
**** This post has been imported from our legacy forum. Information in this post may be outdated and links contained in the post may no longer work.****
We have an immediate application requiring one small conveyor to match speed of another conveyor. Both conveyors have flights and the "slave " conveyor must not only match speed but the flights must be synchronized for proper transfer of the product from one to the other. Any ideas on the best method to do this?
Created Date: August 22,2005
Created by: yank38
You could have the master give an anolog output that it sends to the slave as the speed refernce. You then simply set the spped program in the slave to give you the desired speed based on the analog signal. The only requirement is that the speed curve from master to slave is linear.
Created Date: August 24,2005
Created by: allukes
Depending on your torque requirements, if you need to tightly synchronize the positions of both conveyors to avoid interference of the flights, I would use a Stepper motor. Feed the pulse out from a single indexer (such as from 05, 06 or CTRIO) to 2 stepper drives. You would also need to individually disable each drive to be able to home the conveyors individually from a sensor (PE or Prox) to detect the position of the flights. If you can't get enough Speed or Torque from a stepper then use a servo. If you didn't need exact snchronization, you could try to use analog control, but would probably have to monitor the position of the flights with a sensor to either speed up or slow down the slaving conveyor in order to keep the flights aligned. You need to decide how critical the alignment needs to be, how fast you need to run and motor load requirements.
Created Date: August 25,2005
Created by: Tech Guy
I think that this could be accomplished with a Vector drive with an encoder on the motor shaft. The drive would be set up for electronic gearing to syncronize the drives. One drive would be the master and the other would slave off of it. Check out the SJ300 series of Hitachi drives.
Created Date: August 25,2005
Created by: allukes
I thought the AC drives were only able to synchronize velocity. Do they have Position Snchronization built into the drive as well?
Created Date: August 26,2005
Created by: Tech Guy
Full vector drives can do positioning with encoder feedback, but a servo is a better choice if precision positioning is needed.
Created Date: September 18,2005
Created by: bsgriffen
Mr. Jeff,
I had a similar application on a bridge crane with drives at each end. Magnetek (Yaskawa) drives has a hardware/software solution. The hardware is closed loop vectors and the software is line shaft encoders. What it does is use the buffered encoder output from the master drive to set the speed and rotational position of the slave drive. If the master moves 20 pulsed, the slave moves 20 pulses in the same direction. I purchased a Marathon Vector drive motor. It comes with a 1024 pulse quadrature encoder already mounted on it. The allowed position error was about 20 counts. The system is rock solid. I used CAT 5E cable cable between the master and slave drives. I also used CAT 5E cable between the drives and encoders. The speed of the master drive was set from a 0-10 volt output from a laser positioning device. The crane was 52 ft wide, runway distance of 200 feet, weighed 10 tons loaded, travelled at 300 ft/min and we positioned it within 5 mm every time. The ends of the crane had to be kept square because we were dropping a load that was 32 feet long.
Created Date: August 22,2005
Created by: Mr. Jeff
We have an immediate application requiring one small conveyor to match speed of another conveyor. Both conveyors have flights and the "slave " conveyor must not only match speed but the flights must be synchronized for proper transfer of the product from one to the other. Any ideas on the best method to do this?