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Base Fundamentals

Base Fundamentals. Beach Cities Robotics – Team 294 Andrew Keisic June 2008. Sources. Copioli and Patton’s “Robot Drive Systems Fundamentals” presentation. 2 - Introduction / Agenda. Topics. Center of Gravity Types of Drive Trains Maximizing Design Motor Performance

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Base Fundamentals

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  1. Base Fundamentals Beach Cities Robotics – Team 294 Andrew Keisic June 2008

  2. Sources • Copioli and Patton’s “Robot Drive Systems Fundamentals” presentation 2 - Introduction / Agenda

  3. Topics • Center of Gravity • Types of Drive Trains • Maximizing Design • Motor Performance • Gear Ratio Calculation 3 - Introduction / Agenda

  4. Center of Gravity • A point in space where gravity acts • Why it’s important? • Determines the balance and stability of an object

  5. Center of Gravity • Stability - what ball is the most stable? the least?

  6. Center of Gravity • What robot is the most stable? The least? How do you know? What systems are inherently stable?

  7. Center of Gravity • Putting math behind intuition Stability Triangle α2 α1 h b2 b1

  8. Center of Gravity • Limit of stability is determined by the CG location • In other words – the maximum ramp angle of a stationary robot α2 α1 β2 β1

  9. Center of Gravity • Why keep it low? • Lowering the center of gravity maximizes alpha! Stability Triangle α2 α1 h b2 b1

  10. Center of Gravity • BCR 2008 FRC initial CG estimate

  11. Type of Bases

  12. simple rear wheel drive simple front wheel drive simple all wheel drive simple center drive 6 wheel drive other? tracked drive Type of Bases • Drive train configurations There is no “right” answer! swerve/ crab drive

  13. simple rear wheel drive Types of Bases

  14. simple front wheel drive Type of Bases

  15. simple all wheel drive Types of Bases

  16. simple center drive Type of Bases

  17. 6 wheel drive Types of Bases

  18. tracked drive Types of Bases

  19. swerve/ crab drive

  20. other?

  21. Maximizing Design • Designing is all about tradeoffs • Speed vs torque • Low CG vs reaching high • Weight vs features • Control vs power

  22. Maximizing Design: Motor Performance

  23. Maximizing Design: Motor Performance

  24. Maximizing Design • Requirements • Before designing a system, we must know what it needs to do • The design requirements usually stem from the game • Strategy plays a big part in the requirements • Decide the requirements as a team • For competitive robots, torque is always needed • We’re going to design for maximum torque – pushing ability

  25. Note: Slide from Copiloi & Patton presentation Traction Fundamentals: “Normal Force” weight front normal force (rear) normal force (front) The normal force is the force that the wheels exert on the floor, and is equal and opposite to the force the floor exerts on the wheels. In the simplest case, this is dependent on the weight of the robot. The normal force is divided among the robot features in contact with the ground.

  26. Note: Slide from Copiloi & Patton presentation Traction Fundamentals maximum tractive force friction coefficient normal force x = torque turning the wheel weight tractive force normal force The friction coefficient for any given contact with the floor, multiplied by the normal force, equals the maximum tractive force can be applied at the contact area. Tractive force is important! It’s what moves the robot.

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