Micromouse

Prototyping

Schematic

Soldering

Goals

• Straight lines
• Turns
• 👍 😂

Limitations 😅

• Acceleration

System

Angular velocity

\displaystyle \begin{aligned} \overline{v_2} &= \overline{v_1} + \overline{w} \wedge \overline{r_{21}} \\ v_2 \overline{u} &= v_1 \overline{u} + (w \overline{u_z}) \wedge (2d \overline{t}) \\ v_2 &= v_1 + 2dw \\ \\ w &= \frac{v_2 - v_1}{2d} \end{aligned}

Linear velocity

\displaystyle \begin{aligned} \overline{v_M} &= \overline{v_1} + \overline{w} \wedge \overline{r_{M1}} \\ v_M \overline{u} &= v_1 \overline{u} + (w \overline{u_z}) \wedge (d \overline{t}) \\ v_M &= v_1 + wd \\ &= v_1 + \left(\frac{v_2 - v_1}{2d}\right)d \\ \\ v_M &= \frac{v_1 + v_2}{2} \end{aligned}

Wheels... but how many?

Image taken from micromouseusa.com

Image taken from micromouseonline.com

Image taken from micromouseonline.com

Image taken from micromouseonline.com

Better start with 4...

More about "tetra" designs.

CAD designs

• Motor mount
• Rim
• Both designed with CadQuery (Python)
• 3D printed (FDM)

Approach

• Neural networks?
• State space control?
• ...

PID! 👍 😂

Image taken from micromouseusa.com (Futura Project)

Characteristics

• Positional PD (velocity error is integrated)
• PI for sensor error
• Green Ye's Futura Project documentation 😍

Speed profile

Calculating turns

From the motion equations:

\displaystyle \begin{aligned} \dot{x} &= v_m cos \theta \\ \dot{y} &= v_m sin \theta \end{aligned}

Considering \dot{w} \equiv cte. and v_m \equiv cte.:

\displaystyle \theta = w_0 t + \frac{k}{d} t^2

Discrete integration approximation

Notebook in GitHub

Flood fill 🐭

Image taken from micromouseusa.com (Futura Project)

Implementation details

• Green Ye's Futura Project documentation 😍

Sensors state machine

• 16 KHz trigger
• Sequentially power on and off
• 4 states * 4 sensors

Systick

• 1 KHz trigger
• Update ideal speed, encoder, distances
• Motor control

Main

• Setup
• Buttons, debug LEDs
• Side sensors calibration
• Algorithm
• Communication
• Collision detection

Hardware

• Battery charger
• Power supply
• Programmer
• Soldering station
• Polimeter
• Logic analyzer
• Oscilloscope

Software

• C language - libopencm3, gcc, clang format
• Python - notebooks, scripts, communication
• Continuous integration - github, travis
• Reviews & management - github
• Documentation - doxygen, sphinx
• Board design - upverter

Maze

Eye-opening experience

\displaystyle y = e^{\frac{a}{x+b}}

More on micromouseonline.com

Very optimistic costs

• Around 60 €
• Half is just for motors+encoders (second hand)
• Electronic parts and boards are really cheap (carefully selected)

Realistic costs

• Lots
• Replacements
• Shipping costs
• More than 100 €
• Not counting tools, maze...

And then...

Time... 😂

Current state

Done

• Functional micromouse
• 0.8 ~ m/s (straight)
• 0.666 ~ m/s (turn)
• 5 ~ m/s^2
• Only search speed
• Flood fill

TODO

• Gyroscope integration (PCB redesign)
• More complete maze exploration
• Path selection
• Fast run
• Diagonals
• New wheels (maybe)
• ~60 issues in GitHub 💪 💪

Thanks ❤️

Green Ye

Who shares details about his micromice and posts many useful resources in micromouseusa.com

Peter Harris

Who posts many useful and detailed resources in micromouseonline.com

Kato-san

Who shares details about his micromice and posts some useful resources

Links 🔗

• https://github.com/Theseus/bulebule
• https://bulebule.readthedocs.io