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FRC Concepts: Drivetrains Team 1716 Redbird Robotics.

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Presentation on theme: "FRC Concepts: Drivetrains Team 1716 Redbird Robotics."— Presentation transcript:

1 FRC Concepts: Drivetrains Team 1716 Redbird Robotics

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5 Why are drivetrains important? ●It moves a robot from point A to point B ●Not all drivetrain designs are equal o each have advantages and disadvantages, and not all are entirely obvious ●A robot’s drivetrain is the most basic part of the robot o It MUST be reliable ●A major consideration for pit scouting

6 Rules of Drivetrain Design ●Keep It Simple, Stupid o It’s a drivetrain, not a space station o Simple usually means reliable, too ●It Must Meet Our Needs o Field and operating conditions are the two primary considerations for picking the type of drivetrain we will be going with

7 How Power is Transmitted ●Motors turn ●Gearbox reduces speed, increases torque* ●Chain, gears, or pulleys transmit power to wheels ●Wheels turn

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9 How a Drivetrain is Controlled Arcade One joystick controls direction Tank Two joysticks control either side of drivetrain

10 Why YOU need to know all this ●The engineering and scouting divisions need you to know what you’re talking about

11 Common Drivetrain Styles ●“Skid” Systems o 2WD, 4WD, 6WD, 6WD+ o Tank Treads/Belting o Traditional/WCD ●Holonomic Systems o Swerve (Crab) o Mecanum

12 Two Wheel Skid ●Pros o Dirt cheap o Kitbot can be 2WD o Simple to build ●Cons o Weak, can’t climb inclines well o Loses traction easily - if it gets into a pushing match with a robot, driving wheels may get pushed up above the floor o Noob tier

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14 Four Wheel Skid ●Pros o Easier to control o Simple, more traction ●The Bad o Turning is more difficult (both wheels have traction) o A compromise between stability and maneuverability o Still noob tier

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16 Six Wheel Skid ●Middle wheel is offset, essentially creating two 4WD systems ●Pros o Plenty of traction o Minimized resistance to turning due to middle wheel offset ●Cons o Drivetrain “rocks” slightly due to middle wheel offset  Can be significant if robot has long arms and appendages

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18 6+ Wheels/Tank Tread ●More wheels = more distributed load o Pretty pointless in FRC ●Traction not dependent on surface area o More wheels != more traction ●Pushover tier o Complex and expensive for no good reason o Tank treads only useful if field elements make maneuvering downright diabolical

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22 West Coast Drive ●Two wheels are driven directly by gearbox ●No outer chassis rails ●Wheels “cantilevered” outside the frame o Meaning: the wheel axle is attached at only one point, that point being the square metal tubing the axle is routed through ●Pros o Easier to conduct maintenance on ●Cons o Harder to implement as it requires precise machining

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26 Holonomic Drive Systems ●Allows a robot to move in two dimensions, instead of just forward and backward o This allows it to rotate simultaneously o It can also do this WITHOUT rotating ●Two major systems o Swerve/Crab o Mecanum/Omni

27 Swerve ●Each wheel can (at least theoretically) be independently driven and steered ●In practice, arcade or tank drive is utilized to simplify steering ●Pros o Highest maneuverability ●Cons o Complex to build, maintain, code, and operate. Also quite heavy

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31 Mecanum/Omni ●Uses vector addition to allow for omnidirectional motion ●No complex steering mechanisms ●Requires four independent wheels ●Mass-produced parts make this drivetrain accessible (compared to swerve)

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37 Four Guidelines of Drivetrain Design ●RRRR o Reliability o Repairability o Relevance o Resonability

38 Reliability ●Most important consideration o It’s the most important part of the robot ●Good practices o Wheels be aligned properly o Reduce or remove friction wherever possible o Components must be manufactured to a high degree of quality and accuracy o Components must be durable (no wood or plastic)

39 Repairability ●It won’t be reliable 100% of the time, but it should be close ●Good practices: o Accessibility o Have plenty of spare parts for quick repairs at competition o Maintenance and repair times should be quick (<10 min)

40 Relevance ●Everything on a drivetrain must be worth the work and risk of including it o Driving around in circles doesn’t require tank treads or swerve o Maneuvering around in tight spaces or climbing bumps in the game field may make one of them more worth it, however

41 Reasonability ●We have a limited amount of time and money during the build season o We have to allot our resources very carefully, and putting that time and money into something that won’t offer a good return is a bad idea o this is the reason we didn’t go swerve last year (we’d have to figure it out in only a few weeks)

42 Resources FRC Drivetrain Design and Implementation PPT: oad/2256


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