from the None department...
Synchronization of two Motors
Motion control, servos, steppers, etc. topic
Posted by Kouotou Fenjou on 12 June, 2002 - 11:25 am
I am writing a project on the design of a horizontal belt conveyor and a bucket belt conveyor. The two conveyors are to be driven by different motors. But I would like to synchrozise the two motors since the two conveyors will be used for a chain of transmission.

What are the different components that I need to establish this synchronization?

In the case of a feeback control system, which considerations do i have to make? Is it possible to use sensors to control the speed of the two motors besides the synchronization?

I will appreciate any positive responce from all the members. Thanks....

Posted by Hakan Ozevin on 12 June, 2002 - 6:06 pm
You will need:
1. Two encoders connected to the main shaft for each belt
2. Two variable speed drives
3. A master/follower controller, to sense the difference between the encoders (i.e. position difference) and to lead the variable speed drives.

Posted by Anonymous on 13 June, 2002 - 11:42 am
You will need:
1. Two encoders connected to the main shaft for each belt
2. Two variable speed drives
3. A master/follower controller, to sense the difference between the encoders (i.e. position difference) and to lead the variable speed drives.

Posted by Mike on 12 June, 2002 - 10:16 pm
Run one as a master in speed and the other as a helper in torque.

Posted by Bill on 13 June, 2002 - 12:58 pm
"":ht tp://

This page has application data on how to utilize a master/follower arrangement.

Posted by Frantz Miles on 15 June, 2002 - 12:14 pm
Here is the deal. I have done about twenty of these applications before.

2 x Control Techniques Unidrves (Whatever size)
2 x 1024 PPR Encoders (Compatible with Unidrive)
1 x Control Techniques Second Encoder module

The encoders go on the motors.
The "Slave" Drive is to be fitted with the 2nd encoder module.

The encoder signals from the master motor is then also taken to the 2nd encoder Module on the slave drive.

The UNIDRIVE has pre-set macros for use. The slave needs to be set up for the digital lock macro.

Then, the slave will follow the master according to position (not speed) so that they will be synchronised with less than a degree of rotation.

The following ratio is also setable.

Frantz Miles
Technical Support
CT Dynamics (SA).
+27 41 4531758 (PH)
+27 41 4539299 (FAX)

Posted by Todd Edmunds on 19 June, 2002 - 9:57 am
If you are using a PLC for the main control, you don't need any extra components, just run encoder signals from both conveyors back to the PLC. Use a PID instruction in the PLC to convert the position difference between the two encoders into an analog output value that controls the speed of the "slave" conveyor. It will then match the position of the "master".

The position synchronization will not be exact, but will be close enough for most conveyor applications, and will not "drift" over time.

Posted by Chris on 20 June, 2002 - 11:50 am
Depending on the accuracy of the system, you may not need the encoders. Most applications that I do now use Siemens AC Masterdrives with the motors run in sensorless vector mode. No encoder makes a lot of sense especially in places like a roofing plant or other dirty, harsh environment.

If you have a belt, then there is enough play in the system anyway so don't waste $$$ on encoders.

Don't plc send speed signal to both drives from plc. I agree with set up one drive as master (speed ref from pot or plc, etc.) and send torque limit to the slave drive from this drive.

Posted by Anonymous on 4 October, 2002 - 10:12 am
Have you gotten an answer. If you have can you share it with me.Because i have the same experience also.

My experience:
Master conv -Belt conveyor with a chain drive. Driven by a 3KW induction motor.
Slave conv -Bucket conveyor with a different hain drive driven by a 4KW conveyor.
Objective -To syncronize both the speed and positioning of the falling of the product from the belt conveyor into the bucket conveyor.

Posted by Anonymous on 19 December, 2002 - 1:45 pm
The method I have used in the past is to feed the analog out from the master machine VFD to the analog in of the slave VFD, then using a proximity on both master and slave machines fed into a simple PLC. The outputs of the PLC feed 2 preset speeds on the slave VFD, one fast and one slow, then monitor the proximities and fire the corret output to increase or decrease the slave speed for the time between proxy pulses so making it self correcting. The accel and decel values of the slave VFD need to be quite short, but it does work provided the fixed preset speeds of the VFD overide the analog speed control. Another method would be to use an analog I/O card in the PLC to more closely monitor the speeds, and used the proximity inputs as before to keep sync.

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