AS-0.3200 Winter robot final presentation

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

Assignment

Environment: ice and snow

Propulsion: wind power

Built using Lego

Project plan

Four milestones with smaller tasks 1: Ready to build 1st prototype 2: 1st prototype built 3: 2nd prototype and intermediate presentation 4: Final robot and presentation

Main responsibility areas for group members Heidi: mathematical modelling Jori: software & project management O-P: mechanical design

Milestone 1: Ready to build 1st prototype Due 2.2.2011, reached 4.2.2011 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

Proto-prototype

Milestone 2: First prototype built 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 Servo torque model

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

Servo torque model

Torque required by the servo which takes the larger share of the load

Maximum possible torque ~25Ncm with brand new batteries, 20Ncm “safe value”

First prototype

Milestone 3: Second prototype and intermediate demo

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

Minimum and maximum sail size model We see that the range of a “good” sail area is

very small! (Assumed static friction coefficient here is 0.15)

Friction model It is clear that it’s very difficult to build a sail

that would work well in all weather conditions

Second prototype

Milestone 4: Final presentation Due 11.5.2011, not yet reached 70h estimated, ~100h spent What was done:

Built improved sail Strengthened sail connection Better servo control Wind tunnel sail model

Challenges: Snow melted Everyone sick COMSOL awkward to use

Sail in wind tunnel

The robot now

A trip to the snow dump

Conclusion No one sail can accommodate all weather

conditions Proven mathematically and experimentally Sail should either be very easy to switch, or some

mechanism should adjust it Building the body with Lego's has its ups and

downs Easy to experiment Very difficult to build anything sturdy, needs glue Gear boxes impractical to build

Steering is very difficult The servos need to be very strong Tracks in the snow are difficult to get out of