Dynamic Log File Analysis
Ok, lets take a look at the dynamic file. Here is an overview, of what that should look like if done like shown in the video. Notice the straight lines in the end and beginning of the files – that is the level surface we place the craft on in the beginning and end of the calibration dance. If you see spikes in the begining and end that came from bumping the craft around when plugging or unplugging the SD card, then you should clip that away before you use the file (More on that later)
Lets look at the accels only. Looking closer at the curves around 0, we can see there is some shaking going on, while the craft is being turned. You should aim for the smoothest lines you can get. The below example is acceptable, but in can be done better.
The shaking is perhaps most visible in the gyro plot. Again, this is from a working solution but it can be done better:
Dynamic calibrations are hard to do, even harder when the multicopter gets larger. Common errors are :
- Lost count : during the dance somewhere you’ve lost track of which arms are already done.
- Rough: The ‘dance’ should be as smooth as possible, the graphs will show any rough behavior
- To short: a typical dance should be around 5-7 min.
Clipping noise in the beginning and end of log files
Sometimes its hard to avoid bumping the craft or board around when plugging power or inserting card in the beginning or end of a data gathering session. This will result in noise that has to be clipped away before the data can be used. The logviewer provides a clipping tool, where you can either choose to clip a fixed number of seconds off the files or clip it manually.
Before you begin clipping the file, make sure you have made a proper backup of the file!!
Lets look at an example. Zooming in on the beginning of a static file we can see some noise that came from bumping the around when power was plugged. (To zoom, simply left-click and drag a box around the area you want to zoom in on. Right click zooms out).
The noise you see here, can be clipped away, using either the option for a fixed amount of time to be clipped at the start and end of the file, or by choosing “Manual” and pressing “set marker” and then “cut”. Remember to keep a backup of the original log file.
Once your files look somewhat similar to what you see outlined in this section, you can proceed to calculations