11-02-2012 05:29 PM

Joe Ross

Re: paper: Talon, Victor884, Victor888, and Jaguar speed vs torque tests

That's great.

Could you use the same axis settings for all graphs, to make it easier to compare?

How were the PWM pulse widths chosen?

11-02-2012 05:48 PM

Richard Wallace

Re: paper: Talon, Victor884, Victor888, and Jaguar speed vs torque tests

Quote:

Originally Posted by Joe Ross That's great. Could you use the same axis settings for all graphs, to make it easier to compare? How were the PWM pulse widths chosen?

11-02-2012 06:04 PM

DampRobot

Re: paper: Talon, Victor884, Victor888, and Jaguar speed vs torque tests

Ether, if I examine the graph for the CIM with the Victor 884, it shows that at the top PWM setting, the Victor gives significantly less power than any other of the motor controlers. Di you simply not go to the top PWM setting for that motor controler? Is the 884 truely weaker?

Also, your results seem to show that the motor curves, even at full power, are slightly diferent across motor controlers. Is this an artifact of the testing? If it has to do with the electronic characteristics of the motor controlers, could you elaborate on the design implications?

11-02-2012 06:28 PM

Ether

Re: paper: Talon, Victor884, Victor888, and Jaguar speed vs torque tests

Quote:

Originally Posted by DampRobot Ether, if I examine the graph for the CIM with the Victor 884, it shows that at the top PWM setting, the Victor gives significantly less power than any other of the motor controlers. Di you simply not go to the top PWM setting for that motor controler?

11-02-2012 06:29 PM

Jim Zondag

Re: paper: Talon, Victor884, Victor888, and Jaguar speed vs torque tests

Nice work, very useful.
Could we get the raw data in a spreadsheet, CSV or txt file format so we can import for use in other analysis programs? Thanks.

11-02-2012 07:15 PM

DampRobot

Re: paper: Talon, Victor884, Victor888, and Jaguar speed vs torque tests

Quote:

Originally Posted by Ether It was an oversight. I have the data but it did not make it into the graph. I will post an update later this evening. The switching method, output PWM frequency, parts selection, and circuit design of a controller can affect the motor performance.

11-02-2012 07:37 PM

Ether

Re: paper: Talon, Victor884, Victor888, and Jaguar speed vs torque tests

RevA has been posted. It includes 2.00 and 2.10 ms curves for the 884 graph. Also the tic marks on the 888 torque axis were changed to match the other graphs.

The graphs were created with gnuplot, and the raw data does not contain metadata identifying the plots. I'll work on that after I finish processing and posting the results of the inrush current tests.

11-03-2012 06:41 PM

dsirovica

Re: paper: Talon, Victor884, Victor888, and Jaguar speed vs torque tests

Nice work Ether,

if its not too hard to do, it would be great to see a plot taken all the way to stall and show the Current drawn for Highest PWM, for the FRC approved speed controllers.

I suspect many/most robots are not designed to operate in the optimal range, but are driven to operate in the extreme regions, so it would be a great teaching tool to show the inefficiency when operating in the extreme, and therefore the importance of good design.

This would also show the Jag cutting out way before a Vic does. Though the 2013 Jags apparently will not have a current limit?

Dean

11-04-2012 09:04 PM

Ether

Re: paper: Talon, Victor884, Victor888, and Jaguar speed vs torque tests

Updated revB posted. Four graphs were added to present the same data as a family of RPM vs PWM curves at constant torque.

11-05-2012 09:45 PM

Ether

Re: paper: Talon, Victor884, Victor888, and Jaguar speed vs torque tests

Quote:

Originally Posted by Ether The graphs were created with gnuplot, and the raw data does not contain metadata identifying the plots. I'll work on that after I finish processing and posting the results of the inrush current tests.

11-06-2012 07:52 AM

Jared Russell

Re: paper: Talon, Victor884, Victor888, and Jaguar speed vs torque tests

Does the 888 have the same ~50Hz update rate that its predecessor did? What is the frequency of the modulated output?

11-06-2012 08:02 AM

Ether

Re: paper: Talon, Victor884, Victor888, and Jaguar speed vs torque tests

Quote:

Originally Posted by Jared341 Does the 888 have the same ~50Hz update rate that its predecessor did? What is the frequency of the modulated output?

11-06-2012 08:12 AM

Jared Russell

Re: paper: Talon, Victor884, Victor888, and Jaguar speed vs torque tests

Quote:

Originally Posted by Ether I've been told by a very reliable source that the output PWM frequency is 1000Hz. That's responsible for the reduction in current ripple and the improved linearity. I think the input PWM signal period remains at 17ms since I've not heard otherwise.

11-06-2012 08:35 AM

Ether

Re: paper: Talon, Victor884, Victor888, and Jaguar speed vs torque tests

Quote:

Originally Posted by Jared341 For reference, what are the output PWM frequencies of the 884, Talon, and Jaguar?

11-06-2012 10:44 AM

Paul Copioli

Re: paper: Talon, Victor884, Victor888, and Jaguar speed vs torque tests

There seems to be some confusion regarding the input PWM signal period that VEX Robotics published. The 17ms input signal period in our documentation for the Victor 884 was the typical number used on the old IFI control system.

Both the Victor 884 and 888 can support (and has been tested to support) down to 2.1ms.

Sorry for the confusion.

Paul

11-06-2012 11:02 AM

Ether

Re: paper: Talon, Victor884, Victor888, and Jaguar speed vs torque tests

Thanks for the info Paul. For completeness, do you know the minimum period that the Jag can support?

11-06-2012 12:15 PM

s1900ahon

Re: paper: Talon, Victor884, Victor888, and Jaguar speed vs torque tests

Quote:

Originally Posted by Ether Thanks for the info Paul. For completeness, do you know the minimum period that the Jag can support?

11-06-2012 12:24 PM

Paul Copioli

Re: paper: Talon, Victor884, Victor888, and Jaguar speed vs torque tests

Scott,

We did not change it. It is still 5ms.


All,

To be clear, we did not do anything new with regards to the PWM input on the Victor 888. It has always been 2.1ms on the 884, but we just did a bad job documenting that fact.

Paul

11-06-2012 12:27 PM

Mike Copioli

Re: paper: Talon, Victor884, Victor888, and Jaguar speed vs torque tests

The Talon input is interrupt driven so it can be updated at ~2.1 ms. We published 3 ms to add conservatism for variations due to calibration points and non standard pulse widths.

If the input pulse produces a rising and falling edge the Talon will process it.

11-06-2012 12:40 PM

Ether

Re: paper: Talon, Victor884, Victor888, and Jaguar speed vs torque tests

Quote:

Originally Posted by Paul Copioli All, To be clear, we did not do anything new with regards to the PWM input on the Victor 888. It has always been 2.1ms on the 884, but we just did a bad job documenting that fact. Paul

11-06-2012 01:12 PM

apalrd

Re: paper: Talon, Victor884, Victor888, and Jaguar speed vs torque tests

Quote:

Originally Posted by Ether Paul, would it be useful to ask the folks at WPILib to change their 884 (and future 888) driver to use a period of 5ms instead of 17ms? I realize it probably makes little difference in the vast majority of cases, but there may be teams who want to close a loop at 10ms.

11-06-2012 01:41 PM

Joe Ross

Re: paper: Talon, Victor884, Victor888, and Jaguar speed vs torque tests

Quote:

Originally Posted by Ether Paul, would it be useful to ask the folks at WPILib to change their 884 (and future 888) driver to use a period of 5ms instead of 17ms? I realize it probably makes little difference in the vast majority of cases, but there may be teams who want to close a loop at 10ms.

    /**
     * kDefaultPwmPeriod is "ticks" where each tick is 6.525us
     *
     * - 20ms periods (50 Hz) are the "safest" setting in that this works for all devices
     * - 20ms periods seem to be desirable for Vex Motors
     * - 20ms periods are the specified period for HS-322HD servos, but work reliably down
     *      to 10.0 ms; starting at about 8.5ms, the servo sometimes hums and get hot;
     *      by 5.0ms the hum is nearly continuous
     * - 10ms periods work well for Victor 884
     * - 5ms periods allows higher update rates for Luminary Micro Jaguar speed controllers.
     *      Due to the shipping firmware on the Jaguar, we can't run the update period less
     *      than 5.05 ms.
     *
     * kDefaultPwmPeriod is the 1x period (5.05 ms).  In hardware, the period scaling is implemented as an
     * output squelch to get longer periods for old devices.

11-06-2012 03:00 PM

Ether

Re: paper: Talon, Victor884, Victor888, and Jaguar speed vs torque tests

Quote:

Originally Posted by Joe Ross The Victor 884 class runs at 10ms

11-06-2012 03:08 PM

Joe Ross

Re: paper: Talon, Victor884, Victor888, and Jaguar speed vs torque tests

Quote:

Originally Posted by Joe Ross The Victor 884 class runs at 10ms.

11-06-2012 03:27 PM

Ether

Re: paper: Talon, Victor884, Victor888, and Jaguar speed vs torque tests

Quote:

Originally Posted by Joe Ross And it's as easy to change as calling setPeriodMultiplier in C++ and Java.

11-06-2012 08:12 PM

AlexH

Re: paper: Talon, Victor884, Victor888, and Jaguar speed vs torque tests

ether, can you share any info about the 888 such as operating voltage and amp rating?

11-07-2012 12:38 AM

Tom Line

Re: paper: Talon, Victor884, Victor888, and Jaguar speed vs torque tests

Victor 888:

Nominal Voltage: 12V
Min/Max Voltage: 6-15V
PWM Input Pulse: 1-2 ms
PWM Input Rate: 2.1-500 ms
PWM Output Chop Rate: 1 KHz
Fan Voltage Range: 6V - 16V

No max current listing yet.

We'll be testing one to determine max current (failure current) over the next week along with a Talon.

11-07-2012 01:09 AM

billbo911

Re: paper: Talon, Victor884, Victor888, and Jaguar speed vs torque tests

Quote:

Originally Posted by Tom Line Victor 888: No max current listing yet. We'll be testing one to determine max current (failure current) over the next week along with a Talon.

11-08-2012 11:13 AM

Ether

Re: paper: Talon, Victor884, Victor888, and Jaguar speed vs torque tests

Links should be fixed now.

Here's an interesting visual. I wrote an awk script to read and convert the RPM vs Nm @ fixed IPW¹ raw data into a family of closely-spaced RPM vs IPW @ fixed Nm curves and plotted it with gnuplot. You can really see the change in linearity of the 884 as the load on the CIM increases.

Also, FWIW, here's a graphic of the 884 driving a 1500 ohm resistive load. You can see how linear it is. The non-linearity (when connected to a motor) comes from the interaction of the (slow) frequency the 884's output with the motor's inductance.


¹ input pulse width

11-08-2012 03:35 PM

EricVanWyk

Re: paper: Talon, Victor884, Victor888, and Jaguar speed vs torque tests

Quote:

Originally Posted by Ether Links should be fixed now. Here's an interesting visual. I wrote an awk script to read and convert the RPM vs Nm @ fixed IPW1 raw data into a family of closely-spaced RPM vs IPW @ fixed Nm curves and plotted it with gnuplot. You can really see the change in linearity of the 884 as the load on the CIM increases. Also, FWIW, here's a graphic of the 884 driving a 1500 ohm resistive load. You can see how linear it is. The non-linearity (when connected to a motor) comes from the interaction of the (slow) frequency the 884's output with the motor's inductance. 1 input pulse width

01-16-2014 09:46 PM

Joe Ross

Re: paper: Talon, Victor884, Victor888, and Jaguar speed vs torque tests

Has anyone tested a TalonSR to see how close it is to the original Talon?

01-17-2014 08:01 AM

Gdeaver

Re: paper: Talon, Victor884, Victor888, and Jaguar speed vs torque tests

Our team used talons last year. 8 Total on our swerve module. No failures no problems. We have always put 20mm height EBM- Pabst fans on them. We have a big box of them from previous years. My one most important observation. Our RS-540 steering motors have never run as cool as with the Talons. Original talons not SR's. In a hot warehouse this summer (95 F) our drivers went crazy and drove non-stop for over an hour with only quick battery change for rest. Our steering motors never went over 140F. Our drive cims hit 160F for a short period. The steering motors are in a positional application- go this way no go back this way no go this ways continuously. A Nasty life for a motor and controller. I submit after this observation that the original talons locked anti-phase modulation as opposed to the sign magnitude modulation of the other controllers is superior in a position application that is always hunting and requiring motor reversal. And now they are gone. Do we use last years talons on our 2014 robot or the new SR's ?? I can not prove this with instrumentation we don't have but the observed difference is huge.

02-22-2014 10:25 PM

James Lightfoot

Re: paper: Talon, Victor884, Victor888, and Jaguar speed vs torque tests

I am a rookie mentor, so this reply is coming long after your work, but I still wanted to thanks. When I fist read the User Manual on the Talon, I thought that when it stated a 100amp inrush/60amp maintained w/ a fan for constant loads > 30amps that there was all kinds of headroom. After looking at your charts, I see that my initial thought was wrong.

Thanks for the effort and details.