Partial Jag failure?

[EricVanWyk]

Marshall - does it respond to PWM normally? Are there any signs of physical damage?

Originally Posted by Al Skierkiewicz

...

Al -

Thank you for the very clear and informative post.

The difference in total on-resistance between the Jaguar and the Victor is inconsequentially small. I think the Jag wins the numbers game, but not by enough to make an actual difference.

The reason that the Jaguar uses fewer FETs is that it uses slightly more modern FETs that can handle more current per device.

[kamocat]

Getting back to the question of how the Jaguar failed:

Al's explanation of the desoldered current shunt resistor would make sense, except that the Jaguar says it's outputting 0v.

I re-checked the diagram: the Jaguar measures its supply voltage, but not its output voltage. The output voltage is calculated from duty cycle. (Indeed, in the first revisions of the firmware, the output voltage was only GIVEN in duty cycle, on a range of -1 to 1.)

Apparently nobody has had this exact issue before.

I will check that the resistor is still connected, but I will also try reflashing the Jaguar, in case the firmware got corrupted.

More info on the over-current: the Jaguar goes into over-current fault at 60A after 2 seconds. I was running an RS-775. (There were some binding issues with the jack screw on our arm)

[kamocat]

Well, it worked fine today. I even held it in a 41 Amp stall for 5 seconds.
There's only two causes I can think of.

One is that perhaps it had tripped the breaker and needed "voltage enable" to be sent again. However, I'm pretty sure I would have seen movement out of it before that happened.

The other is that today I'm outside at 15 degrees Celcius. Friday I was inside at 30 degrees. The Jaguar only said its internal temperature was 37 degrees on Friday. I thought it would operate up to 50.

(Note: I haven't opened it up yet.)

[Al Skierkiewicz]

Marshall,
This kind of action leads me to believe there is a foreign body floating around inside. A look inside is warranted.

[kamocat]

I just checked inside.
No debris.
No signs of heat.
The resistance from 0v to vLow measures 0.3 ohms on my multimeter (the same as when I touch the leads together). I measured this between the 0v 6-32 screw and the lead of a low-side MOSFET.

[techhelpbb]

Originally Posted by kamocat

I just checked inside.
No debris.
No signs of heat.
The resistance from 0v to vLow measures 0.3 ohms on my multimeter (the same as when I touch the leads together). I measured this between the 0v 6-32 screw and the lead of a low-side MOSFET.

It would be unlikely a simple digital multimeter could measure that small a resistance reliably with the currents it uses when measuring resistance. Though checking for continuity would confirm that there is connectivity and we know from the fact that it does work there must be a connection currently.

Also...if the resistor got very hot...it would heat the PCB and itself. That combined mass might take a while to cool off even with the fan.

Could it be that you melted the paste on that component and when it finally cooled off it closed again? One could also ask this question about the points to which the body of the resistor meet the areas designed to be soldered down.

In other applications I've seen surface mount resistors recover from overload before but usually it alters the resistance which you might not be able to measure with that meter. If it has altered that resistance by some appreciable amount it'll alter your current measurements. Do these current measurements seem proper for the mechanism in question?

Would there be some value in using a fixed, high power resistor as a load on the Jaguar and taking comparison measurements with another Jaguar? How about just trying to measure the current with another meter with a fixed resistive load?

[Al Skierkiewicz]

Marshall,
I am still going with my foreign body analysis. It is certainly possible for it to have been blown out by the fan.

[kamocat]

That works as a partial explanation.

Any idea why it would refuse to output power? (That is, it reported its calculated output voltage as zero)
I'm guessing it's one of the fault conditions. I know of four:

• Current fault
• Temperature fault
• Bus Voltage fault
• Gate Driver fault (I don't know how it detects this)

I can rule out the Current and Bus Voltage faults right now. I know it tells me of those. The battery was fine, and the Current Fault is temporary.

Does the BDC-COMM display a Temperature fault or a Gate Driver fault in red, as it does the Current fault?

[Al Skierkiewicz]

Marshall,
I don't remember you mentioning a fault condition. It is possible that a particular fault will shutdown the voltage mode and the software may be written to report 0 volts under that condition. It is possible for the any of the sense circuits to have had a fragment causing a short to supply. Say for instance, a short at the input of the current monitor could have artificially raised the voltage input to beyond current rating. In the Tan Jag there is no feedback from the output terminals so the zero volt condition must be derived mathematically from internals.

[kamocat]

Ah, I understand now.

I was thinking of aluminum shavings only affecting large circuits, and destroying them in doing so. I hadn't considered that it might make a contact across a small circuit, and not damage anything in the process. Even more so, I hadn't considered that they might, in effect, put the Jaguar in a fault condition that it can't detect. I don't know that it was in a fault condition, but it's either that or the limits, and I'm pretty sure the limits were not active.

These Jaguars really need a conformal coating. It would be interesting to compare the failure rate. In fact, if I had a few thousand dollars to spare, I would buy Jaguars, paint them with polyurithane, and sprinkle aluminum dust on them to see how well they survive.
But because of the cost, I think that's something best done by TI.

[techhelpbb]

In response to your question in a previous post above:
"Does the BDC-COMM display a Temperature fault or a Gate Driver fault in red, as it does the Current fault?"

In BDC-COMM itself...we find this in: bdc-comm.cxx

//
// Update the status items on the GUI.
//
g_pStatusVout->value(g_sBoardStatus.fVout);
g_pStatusVbus->value(g_sBoardStatus.fVbus);
g_pStatusCurrent->value(g_sBoardStatus.fCurrent);
g_pStatusTemperature->value(g_sBoardStatus.fTemperature);
g_pStatusPosition->value(g_sBoardStatus.fPosition);
g_pStatusSpeed->value(g_sBoardStatus.fSpeed);
g_pStatusLimit->value(g_sBoardStatus.pcLimit);
g_pStatusPower->value(g_sBoardStatus.lPower);

if(g_sBoardStatus.lFault)
{
switch(g_sBoardStatus.lFault)
{
case 1:
{
strcpy(g_pcFaultTxt, "CUR FAULT");
break;
}

case 2:
{
strcpy(g_pcFaultTxt, "TEMP FAULT");
break;
}

case 4:
{
strcpy(g_pcFaultTxt, "VBUS FAULT");
break;
}

case 8:
{
strcpy(g_pcFaultTxt, "GATE FAULT");
break;
}
}
g_pStatusFault->label(g_pcFaultTxt);
g_pStatusFault->show();
}
else
{
g_pStatusFault->hide();
}

So BDC-COMM can trap that gate fault...(I deleted a post above...because apparently they have some unrelated gadget that can't trap the gate fault condition...didn't want to confuse anyone).

This is where they draw and hide the control for the fault indicator in FLTK in the file: gui.fl

Fl_Box g_pStatusFault {
label FAULT
xywh {325 62 100 25} box ENGRAVED_BOX color 1 labelcolor 7 hide
}

So it does not appear that BDC-COMM considers the type of fault in setting this control's color.
Have you seen it do otherwise?

[techhelpbb]

Originally Posted by Al Skierkiewicz

In the Tan Jag there is no feedback from the output terminals so the zero volt condition must be derived mathematically from internals.

I was just digging in the source code for the BDC (not the newer BDC24...the black Jaguar).

They have a file in that firmware: adc_ctrl.c

In that file:

//
// Configure the GPIOs used with the analog inputs.
//
GPIOPinTypeADC(ADC_POSITION_PORT, ADC_POSITION_PIN);
GPIOPinTypeADC(ADC_CURRENT_PORT, ADC_CURRENT_PIN);
GPIOPinTypeADC(ADC_VBUS_PORT, ADC_VBUS_PIN);
GPIOPinTypeADC(ADC_VBOOTA_PORT, ADC_VBOOTA_PIN);
GPIOPinTypeADC(ADC_VBOOTB_PORT, ADC_VBOOTB_PIN);

Then later down the source code...

//************************************************** ***************************
//
// This function returns the current bus voltage, specified as an unsigned 8.8
// fixed-point value that represents the voltage.
//
//************************************************** ***************************
unsigned long
ADCVBusGet(void)
{
//
// Convert the ADC reading into a voltage and return it.
//
return(ADC_TO_VBUS(g_pusADCData[VBUS]));
}

This got me thinking....I know in the black Jaguar you can clearly see in the schematic where the voltage divider for the VBus measurement is.

However, it appears in the older schematic they hid this divider in the schematic section for the power regulation.

Look right next to C15 on the schematic...for the VSENSE tag.
It's on the second page of schematics in the user manual and it's between the great big tag for "+12V POWER IN" and the 5V power regulation.

In pins.h they define:

#define ADC_VBUS_PORT GPIO_PORTE_BASE
#define ADC_VBUS_PIN GPIO_PIN_3
#define ADC_VBUS_CH ADC_CTL_CH0

I'm pretty sure that in both cases (the old and the new Jaguar) this means that they aren't measuring at the output terminals...but they seem to be measuring the same thing.

[Al Skierkiewicz]

tech,
The VBuss is measuring input voltage so that the Jag can disable output when the input power goes down to dropout on the voltage regulators. The thought being that a significant load may be causing a large voltage drop in the input wiring. By disabling the output, the voltage can climb back up to full terminal voltage. There is no feedback in the controller from the output terminals.
I changed the color on your post so people could read it.

[techhelpbb]

Originally Posted by Al Skierkiewicz

tech,
The VBuss is measuring input voltage so that the Jag can disable output when the input power goes down to dropout on the voltage regulators. The thought being that a significant load may be causing a large voltage drop in the input wiring. By disabling the output, the voltage can climb back up to full terminal voltage. There is no feedback in the controller from the output terminals.
I changed the color on your post so people could read it.

Thank you for the assistance with the text color.

They must use it for more than that...from readme.txt in the development kit...

Additional advanced control methods are also available when using the CAN communication interface.

There are voltage compensation control mode, current control mode, speed control mode, and position control mode. Each of these modes is mutually exclusive and operate using a PID controller whose gains are fully programmable via the CAN interface. Each PID controller starts with all of its gains set to zero, so no output voltage will be generated by any of these modes until the PID controller is at least partially configured.

In voltage compensation control mode, the output duty cycle is adjusted to compensate for changes in the input voltage, resulting in a constant voltage output.

From controller.c:

//
// Get the current bus voltage.
//
lVBus = ADCVBusGet();

//
// Compute the desired output PWM width in order to produce the desired
// output voltage, and limit it to the available range.
//
...

Though you are also absolutely right...neither model of Jaguar gets direct voltage feedback from it's output terminals.

[techhelpbb]

I presume in voltage control mode...this section of: controller.c is most critical.

//************************************************** ***************************
//
// This function handles the periodic processing for voltage control mode.
//
//************************************************** ***************************
static void
ControllerVoltageMode(void)
{
...
}

Now...in places littered through out the code they leave the motor in neutral or intentionally create a neutral for coasting.
The do this by setting the target voltages to 0.

What was this Jaguar configured for...brake or coast?