February 9, 2011

Motor Speed vs. Motor Power



Reposting from My Blog.



[caption id="attachment_230" align="aligncenter" width="497" caption="Polled at a Motor Power Output (%) every 5% increase, over a motor rotation of 720 degrees each. Motor Rotation Speed vs Motor Power Output (%) for NBC/NXC Firmware 1.28. As you can see, it's a pretty linear."]Speed/Power is very linear.[/caption]


I was interested in how fast the motors would spin (in the air for the first tests, to not let gravity/load/friction/etc affect the results) depending on what I set pwr in the NXC function OnFwd(outputs, pwr).

I wrote a program (download here) which logged the time it took to spin the motor at 720 degrees (in one experiment), and with a starting pwr value of 5, increasing by 5, until it reached 100. It was tested on the NBC/NXC Firmware 1.28.

It seemed to be linear, and I did a little "analysis" (if you can call it that), and came up with the graph on the right, which represents the ratio between Speed and Power. This ratio is about 7:1.

Next, I tried it with the robot on the ground. The results were pretty much the same (linear), as you can see in the image to the bottom left. Of course, it slowed down a bit, as can be expected.

I still haven't figured out how this is useful, but if you can suggest reasons for why I haven't wasted my time (which I actually like doing, believe it or not), please tell me in the comments. Now I'm adding meaningless text just to fill this line, so my blog post looks good. :)


If you want a copy of the program and data, you can download it here. [LINK]






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