AS-0.3200 Winter robot midterm report

Group: O-P Osmala, Heidi Rintahaka, Jori Rintahaka

Assignment

Environment: ice and snow

Propulsion: wind power

Built using Lego

Milestones completed 1: Ready to build first prototype

Due 2.2.2011, reached 1.2.2011 55h estimated, ~60h spent What was done:

Lots of research, sketch mathematical model constructed Propulsion method (sail) + steering method

(turning/tilting skis) selected Parts weighted, size estimated, skis acquired SDK installed, connection to robot established Missing parts ordered

Challenges: Aerodynamic model of a sail is very complex Everything affects everything in the mathematical model

Milestones completed (cont.’d) 2: First prototype

Due 22.2.2011, reached 1.3.2011 105h estimated, ~80h spent What was done:

Prototype built (without sail) Steering by tilting the skis instead of turning them Primitive Bluetooth interface Control loops for servos

Challenges: NXT built-in servo control is useless No debugger Jori & Heidi sick all the time Getting COMSOL license

Milestones completed (cont.’d) 3: Second prototype, intermediate demo

presentation Due 23.3.2011, reached 22.3.2011 100h estimated, ~140h spent What was done:

Built turning sail (needs 3-4m/s of wind to move) Shortened legs, strengthened chassis Nonlinear controller for servos Bluetooth remote control Lots of testing

Challenges: Incredibly calm period, no wind at all! Jori & Heidi sick again

Challenges Impact of weather conditions

Static friction on ice and dry snow: 0,03 – 0,14 Static friction on wet snow: 0,53-1,76 Required force differs by several orders of magnitude! Gusts of wind may be turbulent and over 10m/s

Difficulty building the body with Lego's Very difficult to build anything sturdy The NXT brick weighs more than all other parts

combined! Something will always get in the way Blu-tack and duct tape help a little

Very nonlinear servo behaviour Very inflexible communication interface