Jaguar current sensing technical details?

[Ether]

Hi Marshal,

A couple of observations and a question:

Two additional sources of error:

Brush commutation on the motor

The Brush resistance is in series with the current sense resistor so it shouldn't cause error in the current sense resistor's reading.

The current shunt resistor is on the supply end of the H-bridge drivers; it is not subject to the motor impedance, because it is cut off from the motors when the FETs are in the OFF state.

It's on the high side in the Black Jag.

In the Tan Jag, it's on the low side.

Either way, the current sense resistor is not in the current path during the OFF portion of the duty cycle. See attached images. For simplicity, I showed path through only one FET of each pair, and only for + currents. Green path is during ON portion. Blue path is during OFF portion (for high-side switching). Red path is during OFF portion (for low-side switching).

I don't know if the Jags use high-side, or low-side, or some other switching method. Does anyone know, definitively, what switching method the Jags use? I've heard many different claims.

What would the current through this resistor look like over a span of 200 us? (That is, 3 pulses at 15 khz)

Good question. I'd like to see some actual data. I did a simulation with the Black Jag with a CIM with locked rotor (no back emf) and included the CIM's resistance and inductance, and included the Zener diode voltage. I'd like to see how it compares to actual data.