paper: Cyber Blue 234 Drive System Test - Performance and Power

[jeremylee]

Thanks for sharing. Another good check would be how much current it takes to spin the tires without moving such as pushing against an unmoveable robot. This is a key high current consumption situation to watch.

[AllenGregoryIV]

A couple things I think would also be interesting. A graph of distance / time, you can see some of this in the FPS vs. time but the actual graph could be enlightening to see how the acceleration changes time to different distances (25' and 50' are often to long of distances in many games).

Also the graphs of each motor current. It may just be how it's measured but it's interesting to me that the 6 CIM has the highest individual peak motor current yet the 4+2 had a higher total current.

[Chris Fultz]

Originally Posted by jeremylee

Thanks for sharing. Another good check would be how much current it takes to spin the tires without moving such as pushing against an unmoveable robot. This is a key high current consumption situation to watch.

there is another paper we posted a few weeks ago that does some of this. we were pushing a wall. we went from 6 CIM to 4, so we wouldn't spin, and that is where we learned about the 7V brownout impacts.

[Chris Fultz]

Originally Posted by AllenGregoryIV

A couple things I think would also be interesting. A graph of distance / time, you can see some of this in the FPS vs. time but the actual graph could be enlightening to see how the acceleration changes time to different distances (25' and 50' are often to long of distances in many games).

That will be pretty easy to do. We have the encoder counts and can convert them to inches (or feet) and plot distance v time.

Originally Posted by AllenGregoryIV

Also the graphs of each motor current. It may just be how it's measured but it's interesting to me that the 6 CIM has the highest individual peak motor current yet the 4+2 had a higher total current.

Also easy to do. In both cases, though, there is not a lot of difference in the 6 CIM or 4+2 CIM.

[MrRiedemanJACC]

This is a great paper and I completely agree with what Wayne stated (and I'm sure others were thinking) that it definitely opens up options of what motors to use elsewhere if we can go with a 4+2 combo on the drivetrain. The game and our strategy on handling it will drive that decision, but it is nice to have options!

Thanks again for posting this information, can't wait to share it with my team on Saturday when we meet.

[sastoller]

Thanks for posting the data. This information is very handy to know.

Just a quick thought regarding the 4 CIM + 2 Mini CIM test outperforming the 6 CIM test:
When I look at your battery voltage plots on pages 8 (single robot) and 14 (pushing), I see that your battery voltage on the 4+2 starts out higher than the 6, and the 4+2 voltage does not droop as low as the 6 initially, when the motors are in a stall situation. This is happening despite the higher measured current draw of the 4+2 system than the 6 system. I do see that you listed battery voltage as a variable that changed with each test. Do you think it is possible that the battery could have been in a higher charge state (and thus able to supply more power to the system) in the 4+2 test than in the 6 test? Is this difference significant enough that it could cause the 4+2 test to outperform the 6 test?

[blturner]

I would like to see the code you used for the data logging. Were looking into doing similar testing and sample code would save us a lot of time.

[Chris Fultz]

We captured the data from the control, which is output as a .csv file, then opened it with Excel. All of the analysis and plots are Excel.

I can get more details on the data logging if that is helpful.

[samthesnake]

I'd like to see some 775 Pro testing. We are intrigued by their capabilities and would consider using them in our drive train.

[Ether]

Originally Posted by samthesnake

I'd like to see some 775 Pro testing. We are intrigued by their capabilities and would consider using them in our drive train.

http://motors.vex.com/775pro

http://motors.vex.com/cim-motor

Comparing the peak power and stall torque graphs will give some insight into why CIMs are preferred over high-speed-fan-cooled motors for drivetrain.