Jaguar Output Question

Technical Electrical
1

I have heard (and experienced) that the output on a tan Jaguar is not fully from -1,1]. Has anyone done testing/know the actual output range of it?

Thanks!! :smiley:

2

Alex -
**
For all purposes, you can assume they do operate -1 to 1.**

The source of this misconception is that the Tan jaguars spend a very small amount of time in the “off” state to re-charge part of their drive circuitry, even if they are commanded to go 100% on.

However, this is transparent to the end user. “1.0” still refers to full forward, and “-1.0” still refers to full backward. Without an oscilloscope, you wouldn’t really be able to tell.

The natural followup is “how does this compare to the Victor?”.
I would argue that this is almost imperceptible, and washes out in the end.

  1. At anything less than 100%, it is irrelevant.
  2. The Jaguars’ FETs are slightly better and have a lower resistance. This means that for a given on percentage, they can give slightly higher power to the motors.

But really, these differences are completely buried in the noise. Any gear box is going to have an impact easily an order of magnitude greater than this.

The reason that Jaguars are typically perceived to be “slower” is that they have a very linear response, whereas the Victors have a non-linear response that is “punchier”.

3

The power delivered to the Cim motor is definitely less with a Jaguar than a Victor. The pure torque output when reflected thru a gearbox is less with the Jaguar— I estimate somewhere in the neighborhood of 10-15%

4

Do you have actual data to back this up, rather than estimates? When we switched from Jaguars to Victors at SVR during Lunch on Saturday, the bot felt more sluggish after the switch than before. (a driver related issue caused the switch. It’s easier to change the hardware then the driver…) So, I’d be inclined to say the opposite, but unfortunately I don’t have any data to actually back it up.

5

The factory calibration on a Jaguar will not give full range on the output if you feed it a hobby servo standard PWM signal that goes from 1ms minimum (full reverse) to 2ms maximum (full forward). That’s what you get if you use an IFI controller, or if you use the cRIO and forget to tell your code to control a Jaguar instead of a Victor (or a servo).

If you tell the cRIO to control a factory-fresh Jaguar, you will get full range on the output. If you calibrate the Jaguar to use the PWM signal it is receiving, you will get full range on the output.

6

Nope, I don’t buy it. Got Data?

7

Interestingly enough, Luminary Micro’s own data seems to show a CIM motor a few percent slower, although certainly not 15%. However they don’t give enough data to know how similar the test conditions were.

8

Alan,
Just to be sure, your answer was directed at Austin’s post (and Mr. B’s) rather than the original, correct?
At full throttle there is essentially no difference electrically between the two controllers as Eric has pointed out. Both the Victor and the Jaguar are supplied with a method to calibrate the controller. If you experience a significant difference after modifying the code as Alan has pointed out, then you may suspect that calibration has been changed. The indicated difference in the post that Joe has pointed to, may be due to the method used to produce the graph rather than actual speed results.
As Eric has pointed out, the “ON” resistance between the two are slight, only a .004 ohm difference between the two controllers.

9

We do not see any difference in speed! But the torque output definately drops off. Initially both are the same but the current folds back on the Jags reducing the torque output.

10

Mr. B,
When the Jaguar is commanded through PWM input, there is no current foldback. If an over current condition is met, the Jag goes into fault for three to four seconds where no current flows and the LED flashes RED.

11

AL, I am not sure of the correct terms to describe what we have seen, but with the victor, when the motor is loaded to the max, the motor output continues at speed and torque(I assume this is a peek condition). The Jag will start at full speed and torque but, slowly the speed is reduced until it faults out like you have described above. In 3-4 sec it will start moving but again it will slow down and fault out again. My assumptions are:
The Victor will continue to put out a Peek current while the Jag circuit requires the Jag to fold back to a max continious causing the speed to decrease. When we look at the voltage output to the motor with a scope, we can see a decrease over time, therefore because V=IR the current must be decreasing.
Note, both controllers were tested with the same set-up.

12

Mr. B,
The output voltage changes? That is to say the motor output waveform moves from a 12 volt peak to peak waveform to something less (8-10 volts)? Sounds like it could be a FET failure. The Jag manual talks about the current fault in terms of .2 sec of 100+ amps and 2 sec of 60+ amps but it does not speak to limiting current.