1. AS-0.3200 Winter robot final presentation Group: O-P Osmala, Heidi Rintahaka, Jori Rintahaka

2. Assignment  Environment: ice and snow  Propulsion: wind power  Built using Lego

3. Project plan  Four milestones with smaller tasks  1: Ready to build 1 st prototype  2: 1 st prototype built  3: 2 nd 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

4. Milestone 1: Ready to build 1 st 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

5. Proto-prototype

6. 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

7. 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”

8. First prototype

9. 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

10. 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)

11. Friction model  It is clear that it’s very difficult to build a sail that would work well in all weather conditions

12. Second prototype

13. 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

14. Sail in wind tunnel

15. The robot now

16. A trip to the snow dump

17. 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