Motion Control – Virtual Gearing

Posted on November 16, 2021

Jeff Mottershead heashot

Two motors are virtually geared if they move as if they were mechanically coupled together, despite there being no physical connection. Virtual gearing systems are classified as relative or absolute:

Relative systems behave as if they were V-belt coupled; they accelerate in unison and maintain a constant speed ratio, but there isn’t a controlled phase position.
Absolute virtual gearing behaves as if the shafts are coupled toothed gears; synchronization is preserved even through a power outage by absolute encoders. If the envelopes of two mixers overlap, like in an eggbeater, only absolute virtual gearing will do.
Coanda’s go-to motion control platform, the Siemens S120, supports absolute virtual gearing at all scales. We’re able to size experiments with interfering geometries based on scaling relationships, not dual-output gearbox availability. We can adjust the phasing with a keyboard, rather than machining a new key slot. We’re also free to parameterize the gear ratio.

In any system with coupled motion that we’re optimizing, absolute virtual gearing gives us design freedom and the ability to continuously vary parameters that would not be possible using a mechanical coupling.

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