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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 1 st prototype 2: 1 st prototype built
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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
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”
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
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
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