Some measurements I did a long time ago, specifically for the two placements I cannot find my post.
Others:
The documentation and software for GoPiGo3 is built around the following:
Wheels are “nominally” 66.5 mm
Motors have a 1:120 gear reduction ratio
The magnetic encoders are “incremental” type (can tell direction of rotation but not absolute position)
The encoders output 6 counts per motor shaft revolution
Both the GoPiGo3 and EasyGoPiGo3 APIs read the encoder hardware in encoder counts
All GoPiGo3 and EasyGoPiGo3 APIs communicate in whole integer degrees (2 encoder counts)
For drive_inches() i…
IMU or Wheel Encoders for GoPiGo3 Heading Estimation
TL;DR:
Wheel Encoders were 85% to 300% more accurate than IMU
Wheel Encoder Heading Estimation displayed 33% less drift than IMU
Disclaimer: YMMV - Just documenting my observations.
[Carl_IMU_Quarter_View]
Test of IMU “Heading Estimation” vs Wheel Encoder “Heading Estimation” (by integrated rotations) after four “Undock - Dock” sequences:
Conditions:
33 Hour test with 28 heading-affecting events:
Undock = Drive off dock, continu…
I remember testing both placements with a clear improvement when I moved the battery/CG forward, but I can’t find my notes on it.
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I have a set of command line test programs that allow tuning for best performance regardless of the placement:
The title of the doc for these programs is ROS GoPiGo but it does not actually need ROS:
# Tuning the ROS2 GoPiGo3
The GoPiGo3 has a nominal WHEEL-DIAMETER of 66.5 mm and WHEEL-BASE-WIDTH of 117 mm
but...
Due to reality the effective wheel diameter and wheel base will be different.
To have the most accurate encoder odometry, the effective values need to be determined and
put in the JSON parameter file: ```/home/pi/Dexter/gpg3_config.json```
The first time your robot instantiates a GoPiGo3 or EasyGoPiGo3 class, the default values will be writen to the file.
To view the file conveniently:
```
python3 ~/systests/gpg_config/print_gpg3_config.py
or of course:
more ~/pi/Dexter/gpg3_config.json
```
show original
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este
October 9, 2023, 8:06pm
3
@cyclicalobsessive Wow, thanks for creating this great topic that pulls together a lot of useful information! I really appreciate it!
3 Likes
jimrh
October 13, 2023, 8:01am
4
You should be using the new Li-Ion battery packs.
If you’re still using AA batteries, make sure you completely cover both ends of the battery holder with black electrical tape to prevent short-circuits.
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este
October 13, 2023, 3:08pm
5
Yup, new GoPiGo3 so the Li-Ion battery packs which I love BTW! Thanks for the tip regarding what to do if I were to use the AA battery variant!
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