Hello, I'm working on proof of concept for a feeding mechanism using dual motors. Typically our feeding mechanisms use 1 small permanent magnet dc motor via gearbox to drive 2 rollers. Due to tolerances on the rolls, any difference in diameter will result in some slippage between the two rolls. I was inspired by a model locomotive with dual motors. Each motor in the locomotive drives it's own wheels. Since the track is rigid and the locomotive weight is enough to avoid slippage, the series deviations in motor speed are equalized.
I've only started testing the concept and I'm confronted with the difference between series and parallel. I'm aware of the implications this has on tension and current, but I don't quite see a clear choice for this.
In series I can easily add more load to one motor and quickly see the oposite motor increase speed. I interpret this as a more dynamic setup not unfamiliar to a differential gearbox. The downside is that there is no limit to the slip.
In parallel I do not have the above relationship between load and speed of opposite motors, only the relationship of load and speed for each motor individually. One advantage is that there is not unlimited slip. But, I am not yet convinced that the torque stiffness of each motor won't result in slippage. Contrary to the model train scenario, my workpieces can sometimes be soft material.
Are there any electrical techniques to create the "limited slip differential" in the series connected motors? Are there any techniques to make the parallell setup more dynamic?
From a control perspective, I was thinking to use feedback from only one motor, and let the other follow along.
How are you controlling the motors? Depending on the setup you can lead/follow with an encoder or sometimes step pulses and create slip. Using slip from one motor to control another motor may take some trial and error and be prone to external variances.