FLL Robot Odometry With LEGO MINDSTORMS 51515 Rotation Sensor

LEGO MINDSTORMS 51515 motors come equipped with absolute rotation sensors, AKA motor encoders. FLL robots have long relied on their motor rotation sensors for navigation via odometry. Today, I teach you how to use the redesigned LEGO 51515 rotation sensor and show examples that are relevant to an FLL robot application.

CONTENTS
0:00 - Introduction
0:42 - Absolute Motor Encoder Explained
1:18 - Exploring Port View
3:22 - Code Example 1: Motor Position Reset
5:04 - Code Example 2: Odometry
6:42 - Adjusting for Wheel Size

📽 Thank you to my friend Preston Nichols for designing Builderdude35's intro animation and logo!

#builderdude35 #lego51515 #legomindstorms51515

[Builderdude]

Tell me about a time where you used the motor encoders to navigate your FLL robot!

[dluders]

When using Lego Mindstorms robots in FLL, one should make sure that the "gear lash" inside the motors are the same on both wheels. At the FLL Base, one has to drag the robot back into position, so that the internal motor gears are meshed the same on both sides. If one does not drag the robot back into the FLL Base, when it launches the robot may suddenly cock at an unintended angle.

[largewallofbeans]

I made this turntable robot thing and it had a few gears from the motors to the wheels, but it was very easy to recalibrate the distance values. Kudos to Lego to adding that subtle but extremely useful function.

[gibfordsrobotlab]

I had no idea about those pull down menus on the motors allowing us to select relative position. The ability to select position or relative position is a real game changer. Thanks for showing us this.

[WitoEngelke]

Nice video! For the problem at 6:46 : Another simple way, especially when using gearing before the drive wheels, is to measure your robot specific configuration. Driving for a fixed amount of rotations and measuring the distance it traveled. Higher numbers of rotation result in higher accuracy. Besides that you can look into motor acceleration and how they break. With this, the movement during start and stop gets smoother and higher motor speeds can be used. Especially useful for heavy robots. Have fun building!

[hydroworld-soontobemigrate]

Is there a video coming out soon on that FLL-style robot you built from the new kit? It appears to be a successor to Sirius, and now that Robot Inventor and Spike Prime are officially allowed in competition, building compact robots like that will come in handy for many of our teams.

[justadude]

I noticed that you don't seem to use the "More Motors" and "More Movement" extensions; is this just to keep things simpler to understand? Also, one of my biggest frustrations about the new robot and software is the removal of text files - is the only solution (in terms of RLI calibration) to have all runs/programs in the same project? Or should we just have predefined RLI values?

[bobcubsfan]

Of course you can set multiple motors to Shortest Path with one block.