Preserve Const Speed with Variable Voltage and Stop the Motor as quick as possible

Thanks Chris for your answer,

the first problem is near to be solved, with the overmodulation and the Vbus compensation disabled the target speed is preserved until 37 V (under the system is a little bit unstable).

In the second problem I drive the motor to 0 speed (or at least I think I did - maybe I didn't follow the right procedure, can you explain a little bit more?) but the stop is to slow.

If I do the right thing, then I'd think to force to gnd all the three phase of the motor (close for example the Q7, Q8, Q9 MOS in the 515502~1.pdf schematic, how can I do this? with the HAL_writeDacData ()/HAL_writePwmData() function?Which values can I use to do this?

Thanks Again

Matteo

Thanks Again,

I try to implement this last solution but, for now, my solution doesn't work very well:
When I wan't to stop the motor, the firmware bypass the CTRL function (CTRL_run() and CTRL_setup()) and when the speed decrease under 1500 RPM I set all three variables gPwmData.Tabc.value[0,1,2] to _IQ(0.0) and then I use the HAL_writePwmData() to force all three phase to low level.

What I see at the oscilloscope is that: in the first part of braking there are floating phases (right behavior because I use HAL_disablePwm()); in the second part (when the speed is under 1500 RPM) I see all three phases not at low level but oscillating between high and low level (all three with the same timing --> I think that the driver switch on alternately Q4,Q5,Q6 (High level MOS) and Q7,Q8,Q9 (Low level MOS)).

I achieve a good braking effect but I'd like to force to low level all three phases for all the braking time; I know that I'am doing something wrong but I don't understand the error. Any suggestions?

Another question: setting to 0% the duty cycle, do I obtain the same results?In affermative case, which variable do I change to work directly on the duty cycle?

Matteo

Hi Chris,

I solve the active braking problem; I modified the HAL_writePwmData() in HAL_writePwmMOD() and I use it when, in the braking sequence, the speed goes under 2000 RPM:

static inline void HAL_writePwmDataMOD(HAL_Handle handle,_iq dutyCycle)

{

uint_least8_t cnt;

HAL_Obj *obj = (HAL_Obj *)handle;
PWM_Obj *pwm;
_iq period;
_iq value;
uint16_t value_sat;

for(cnt=0;cnt<3;cnt++)
{
pwm = (PWM_Obj *)obj->pwmHandle[cnt];
period = (_iq)pwm->TBPRD;
value = _IQmpy(dutyCycle, period);
value_sat = (uint16_t)_IQsat(value, period, _IQ(0.0));

// write the PWM data
PWM_write_CmpA(obj->pwmHandle[cnt],value_sat);
}

return;
} // end of HAL_writePwmDataMOD() function

If I set to _IQ(0.0) or _IQ(1.0) I'am able to force all three phases to low or high level; in the photo you can see the first braking part with floating phases and the second braking part with all three phases to low level

Thanks to the purple signal that represents one of the three hall sensors monted in the motor, I can controll the effective braking time which is about 2 seconds (perfect for my security specific)

I have now another question: Which is the maximun value for the overmodulation variable that doesn't damage the inverter and let me to obtain the best performance in terms of stability and max speed with low power supply voltage?

I set overmodulation = _IQ(1.5) to maintain 3200 RPM in 41-31V voltage range with no load motor. Is this value too high?how can the situation change with a loaded motor?

Thanks Again

Matteo