Syncronising 4 Motors


Thread Starter

John Peterson

Hello All,
I have 4 motors spaced along a conveyor, they are all mechanically coupled via the conveyor. I wish to syncronise the speeds of all motors (for obvious reeasons). Feedback is via quadrature encoder. The motors are hydraulic with contol via +-10V command.

Can someone suggest a blackbox whick will provide such syncronisation.

[email protected]
Integration Solutions
702 Henley Rd
Kangaroo Ground Vic 3097

Check out they make a product called the MTSC-32. I beleive they can control up to 4 axis per unit and the units can be daisy chained.

The product is DSP based. I have used it on slitter, where I wanted to replace a transmission with 3 DC motors, so I could control the draw (speed difference) between the zones. It works well, almost servo accuracy.

I would suspect you would attach an encoder to each of your actuators and feed the encoder signals back to the MTSC-32. The MTSC-32 can provide the ramping for the actuators as well as the machine states.

I think they will run you about $3000.00 (US Dollars)


robert trask

I do not know of one blackbox that will do it, but check out Contrex ML-Trims that will synchronize on an individual basis and are easy to
cascade. No programming either, just enter a few parameters and you are hauling the mail.

Best regards,

Robert Trask, PE [email protected]
Wilmington, NC USA

Johan Bengtsson P&L Automatik AB

Ok, I don't know much about controlling hydraulic motors but I can't find where the problem is, it sounds to me like you have the following:

If you have one hydraulic motor you have to motor and a valve controlling the flow thru the motor, right?

If you have 4 motors and feed them from the same (larger) valve they will produce about the same torque (of course not exactly the same but quite close) and divide the flow more or less equal between them (depending on tolerances). They will be rotating with the same speed since they are mechanically linked together. Only use one point of feedback, let the other three just take their share of the torque and let the mechanical link between the motors control the small (but surely existing) differences between motors/piping/diameters/etc.

Am I missing something too obvious here?

/Johan Bengtsson

P&L, the Academy of Automation
Box 252, S-281 23 H{ssleholm SWEDEN
Tel: +46 451 49 460, Fax: +46 451 89 833
E-mail: [email protected]
Since you have feedback and a drive with +/_ 10 volt input, you have the makings of a servo loop. All that is missing is the summing network and the D/A converter. Once you have that, close 4 loops and command them all in parallel. Any motion control vendor can provide that. I know CTC can do it.

Thomas B. Bullock, President
Bull's Eye Marketing, Inc.
Industrial Controls Consulting Div.
E-mail: [email protected]
Phone 920: 929-6544

Phillip O'Meley

Just a word of caution, if the conveyor has any flex in it i.e. made of rubber. You can end up with the motors chasing each other. A quick solution is to make one the master and have the others act as slaves, with relevant time delays in the response loop to allow for flex in the system.
Phill O'Meley

The world belongs to the Enthusiast who keeps his cool.
William McFee
The key word here is command. If you give them all the same command, then they will not chase each other. Many electronic gearing schemes have one motor follow the feedback of another. This can introduce lag into the system. If they both
are geared to a common reference, then there is no programmed lag.

Bill Sturm
Actually, commanding them all in parallel with each having its own servo loop is better than having one as the leader and the other 3 as followers. This is because the leader will be ahead of the follower by the amount of the servo error. This may not matter at low velocities,
but could become substantial at high speeds.

Thomas B. Bullock
President Bull's Eye Marketing, Inc. Industrial Controls Consulting
Division [email protected] (920) 929-6544

Phillip O'Meley

Agree with the comments to my posting. However there are applications where a M/S solution works simple and well. The parallel control will work quite well if the link between all four motors is solid, however if the motors are only connected to each other through a flexible conveyor, (The length of the conveyor comes into play here as well, applications I am referring to are
typically >4000ft, although the drives are situated in close proximity to each other) then on start up the flex within the belt may cause (depending upon complexity of control loop
implemented) serious problems. My example may not be similar to the application under discussion. Regards Phill O'Meley