Partial Jag failure?

[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]

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?

[kamocat]

This one was configured for coast.

[Al Skierkiewicz]

tech,
Marshall said he checked using voltage mode after the controller failed. Vbus is used when the target speed on the motor is known and the input voltage is variable. In CAN bus Voltage mode, this is a requirement to maintain motor speed in the absence of a rotational sensor. Again it is a calculation used to make the output voltage appear to be regulated. It does not regulate the output voltage but it does modify the PWM output to the motor to simulate voltage changes. Again, the Vbus must be monitored in all modes even if only used for internal protections.
It is not necessary to fill the server with text that is easily found somewhere else. If you would like you can delete your earlier posts or I can. Just let me know.

[kamocat]

I'm sorry, I wasn't clear enough.
I used %vbus mode (the original voltage mode), not the voltage compensation mode you refer to here.

[techhelpbb]

Originally Posted by kamocat

I'm sorry, I wasn't clear enough.
I used %vbus mode (the original voltage mode), not the voltage compensation mode you refer to here.

What mode were you using when you pushed the Jaguar over the current limits?

[kamocat]

Originally Posted by techhelpbb

What mode were you using when you pushed the Jaguar over the current limits?

Either %vbus or position. Perhaps both.