The Neverending Arms Race: FRC

Peyton Fitzgerald and Peter Ha Who We Are

Peyton Fitzgerald Peter Ha

● Freshman at Northeastern University ● Senior at BHS ● FRC Alum (5459 Mechanical and Drive ● Fourth year on the Nutrons Coach) ● Mechanical student, 2017 driver ● 125 College Mentor What is a ?

● A drivetrain is the system of motors, , and that enables the robot to move. ● Without a solid drivetrain, your performance will be limited by struggling against the drivetrain. ● Your drivetrain is the first, second, and third most important system on your robot. Important Design Factors

● Agility ○ How well can we avoid defense and approach objectives quickly? ● Terrain Maneuverability ○ Can it get from point A to point B over/around obstacles? ● Pushing Power ○ Will our robot get pushed around? ● Rotation Point ○ Can we make alignment easier? Will the robot be balanced when moving? ● Simplicity ○ Can you pull it off? Will it break? How long will it take? ● Weight ○ Low center of gravity and weight limit ● Ease of Driving ○ Use your drivetrain to its full potential ● Gearing ○ Adjusting motor load Wheels

● For tank drive, traction wheels are default ○ Many types are similar, I prefer Colson wheels ○ Wider = better traction, more turning drag ● Plaction wheels offer the same purpose as traction wheels but ○ Have higher traction ○ Require maintenance (replacing tread after wear) ● Omni wheels ○ reduce turning drag and ○ change turning point ● Pneumatic wheels ○ absorb impact (like in 2016, getting over obstacles) ○ Just like , wheelbarrows, and lawn mowers ● Size ○ Larger wheels are better for moving over large terrain ○ 4” wheels are usually a good bet for flat field ○ Remember… wheels are a “” in themselves Motors

● CIMs ○ Big, powerful, standard ● MiniCIMs ○ Smaller, less powerful ● 775s ○ Traditionally used for manipulators and other purposes, but growing in popularity for drivetrains Motor Curves

● Single most valuable tool in designing your drivetrain ● Look at max power for an idea of general motor performance ● Speed and torque can always be adjusted via gearing Gearing and Power Transfer

● Gears ○ Standard method of gearing and power transfer. ○ Not as flexable as other methods, but the easiest to implement. ● Belts ○ Requires precision CAD and manufacturing. ○ Great for when you know exactly what you want. ● Chain ○ More flexible in length and implimentation than belts. ○ Easy to start with. ● Direct drive ○ No. Drivetrain Types

● Tank drive ○ Simple, straightforward option with excellent reliability and good means for customization with wheels, gearing, and motors. ● Holonomic drive ○ Gives many more movement options via strafing. Good when there is no defense, but hard to win a pushing war with. ● Exotic drives ○ Infrequent and often extremely complicated. MFD. Holonomic Drive (H-drive) Tank Drive

Exotic Drive (Grasshopper drive) Tank Configuration Options

● Wheels ○ Traction wheels standard ○ Four, six, eight ○ Center Drop vs Corner Omni Wheels ● Special Substitution ○ Plaction, pneumatic, omni, etc ● Motors ○ 4 CIM (standard), 6 CIM ○ 775Pros, Mini CIMs ● Video Holonomic Drive

● Adds additional degrees of movement freedom to your basic tank drive. ● H-drive ○ A tank drive setup, with omni wheels, and two perpendicular omnis in an “H” arrangement. ○ Allows the robot to strafe while driving, though losing significant traction via the omni setup. ○ Requires additional motors for the H-wheels ● Mecanum drive ○ Tank drive with mecanum wheels. ○ Similarly to H-drive, allows the robot to strafe, but requires individual motors driving each wheel, so each wheel can move independently. ○ Loses yet greater traction to the mecanum rollers. ● Swerve drive ○ Each wheel can pivot relative to the robot, allowing the robot to strafe, rotate, and drive simultaneously. ○ Adds a whole degree of complexity above most other standard drive designs. Holonomic Drive

H-Drive

Mecanum Drive

Swerve Drive Exotic Drives ● Arms Race of Drive Trains ○ Every year, during the offseason, the higher performing teams and incredibly bored people will design incredibly over-complicated and hyper-specialized drivetrains, resulting in some really cool, if impractical, designs that only sometimes see the light of day. ○ Usually involved actuation of wheels or an extreme number of wheels, motors, etc ● Insect/Critter drive ○ Uses pneumatics to switch between one of two wheels, giving more movement options. ○ Situationally very useful, when you have two movement scenarios to deal with. ● Kiwi Drive ○ Three wheels arranged in a triangle pattern. ○ Difficult to drive without computer assistance. ○ Each wheel moves independently, similarly to mecanum drive. ● 775 Drives (Tank and Differential Swerve) ○ 775s burn out easily, but teams are battle testing them for drivetrains Exotic Drives

H-Drive Butterfly Differential Swerve CIM-in-Wheel Swerve

775 Drive Octocanum Drive Things to Keep in Mind

● Build to your capabilities ● Build to your needs ● Cooler isn’t always best Resources

● Ideas, help, etc.

● Parts Questions