Quote:
Originally Posted by Tristan Lall
I think he means that the disable signal is either an element of the control signal (neutralizing PWM to disable is "in-band"), or a separate signal (neutralizing via digital I/O + PWM is "out-of-band").
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Basically.
In telecommunications when we are doing in-band management we are managing something often over the same bandwidth that infrastructure is providing (SSH for example). When we do out-of-band management we are providing some alternative communications infrastructure to manage devices (a dial-up modem to a Cisco console port for example).
If you can somehow communicate over the CAN bus to the electronic motor control your intention to disable it you are operating in-band.
If you add a digital I/O wire to communicate the disable you are operating out-of-band (there's probably no other communications on that disable wire, or as much of my industrial stuff would call it the e-stop). The addition of the alternate communications infrastructure makes it out-of-band.
Stopping PWM might be considered in-band signaling in some ways, but personally, the absense of signal into a motor control to me should just naturally make it stop. Just as if you powered it up on a bench to test with no signal input. That's really a fault condition to me because generally with PWM there's a certain pulse width that's the neutral position for the speed control and in the absense of even the base frequency you may as well have left it floating.