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."][/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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Another datalogging experiment - GPS

Well...I made a new datalog experiment using the beta version of the Dexter Industries GPS sensor!  I logged the latitude, longitude, velocity, and heading, all with just one sensor!  It was about a 25-min. drive.  And, the sensor tracked us all the way from point A, to point B.  Here are some graphs for you to see:



It may be kind of hard to see, but by looking at these, we can see a few things.  First, we can see that I was traveling mostly North and East.  Second, we can see how many left and right turns I made.  We can see where I stopped and was going.

Thanks for looking at my website!

jojoguy10

*Special* "Datalogging" a rolling tube

Hell0 everyone,

I'm here with a special presentation of my own!  I have created a datalog situation, where I roll in a pipe (or tube/barrel), and the NXT (with a HiTechnic Accelerometer sensor on it) records the 3 different axis.

[caption id="attachment_384" align="alignleft" width="754" caption="(click to enlarge)"][/caption]

There is lots of info we can pick up from this graph.  First, we can see that, the X and Z axis are going crazy, but the Y axis is staying, relatively, in the same spot.  Why?  Because I positioned my NXT upwards (meaning, I had the accelerometer sensor facing forward, so the Y axis was pointing left/right [ends of the barrel]), so the Y axis didn't show much data, because it wasn't used very much in this test.  But, if I had positioned my NXT, so that the Accelerometer sensor was pointing left/right (ends of barrel), the Y axis would show more change. We can also pick up from this "Rolling......" segment if the fact that each spike, is 1 revolution for the barrel. So, if you count the X spikes, you will see that there are 14 spikes. So, 14 spikes = 14 revolutions, which you will see in the video.

The second thing we can pick up from this graph, we can see the highest (or, in the X axis state, lowest) point in the axis lines: Z: 459 (~2.25 G's), X: -444 (~-2.25 G's), Y: 332 (~1.5 G's).

Third thing, right after the "Rolling......" part of the graph, you see a bunch of jumps and spikes in the Z axis.  That's because, if you see the video, you will see that I ran down a hill, and into some rocks, so those spikes, are the bumpy rocks and the hill.

Last thing you can pick up from this graph, you can see different jumps in the graph, and therefore, know what's happening.  For instance: the constant up and down movements made by the X and Z axis in the middle of the graph, are made from me rolling.  And, near the end, where the Z and X axis curve a bit, and the Y axis jumps, that's where, at the end of the "ride", it went slowly from upside-down to rightside-up.

I have also calculated the speed at which the barrel was going: ~10ft/s. The barrel is 9ft in circumference, and the time it took to go 1 revolution was 0.9, so, it was going about (~) 10ft/s.

Here is a little 30 second video that shows how I made the data (I started the program around 0:12):

Thanks for reading!

jojoguy10