Modeling motor control

[Kevin Sevcik]

Alright, I'm transferring a post from the current sensing thread over here to keep things better organized.

Originally Posted by kamocat

No, they can't modulate the PWM pin. If they did, that would be locked antiphase, because the MOSFET driver would alternate between driving the low side and driving the high side.

Noooo, the Jags aren't operating in locked anti phase, and the tan wouldn't if the PWM pin was modulated.

Locked anti-phase required reserving the entire h-bridge to go from forward bias to reverse bias in respective PWM phases. It's a Forward-Reverse phase modulation. That's definitely not what either Jag is doing.

Both Jags hold one half of the h-bridge constant. So in forward motion, the M- half is held high-OFF, low-ON for the entire PWM cycle. In the Tan Jags, the M+ high side is selected via the PWM pin, and the output disable is modulated, so the M+ low side would never turn on. So that's a Forward-Open modulation. The Black Jags do things differently and alternately drive the M+ high and low sides. That's a Forward-Shorted modulation, because we never turn on the M- high side.

So I was suggesting that the Tan hardware seems perfectly capable of the same Forward-Shorted operation as the Black if they modulated the PWM pin instead of the Output Disable pin.