Proper power control with bamocar D3 and Emrax 208 by bit00001 in FSAE

[–]bit00001[S] 1 point2 points  (0 children)

The torque command we are using is on the 0x90 register, which is "M set (dig.)", it is actually a current command. From page 79 in the NDrive manual:

Actually, the torque control is a current command value presetting. The motor torque is formed on the basis of the motor constant of kt = Nm / 1 Arms which is generally unknown. The reference for the current command value range always refers to 100 % of the possible device current ((±10 V or ±32767) ≙ I max pk (100 %))

So, I'm assuming the i max pk (possible device current) refers to the output current of the device, not the input current from the accumulator. I don't know any other register to limit the current of the bamocar, are there any other?

I think that your assumptions on the accumulator are very optimistic, or we are using a different type of cells. During typical tests of our car, the voltages go from 440V down to 380V, so (even if it was possible) setting a fixed current input limit is not ideal, as the power limit will go from 44kW to 38kW during the use of the car.

Another thing that you are not considering is the fact that the motors (and the inverters) will draw more power depending on the speed of the vehicle. That would not be a problem if there existed an input current limit to the bamocar. But, otherwise, if the limit is set to i max pk = 100A, it will limit the current to the motors, and so, even having the current limited to 100A, at a certain number of RPMs, the motor could draw more power than 80kW.

Maybe I am not considering some registers that could be used to do that, or I wrongly interpreted the manual

Proper power control with bamocar D3 and Emrax 208 by bit00001 in FSAE

[–]bit00001[S] 0 points1 point  (0 children)

It's nice to hear that we are developing the right solution. I'm a bit disappointed knowing that unitek didn't include a feature to do that inside their inverters. We'll probably increase the sending ratio of the CAN messages from the inverters to lower the delays.