Transcript File

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Drivetrains
Presented by:
John & Paul Hines
Purpose of this Presentation
• Drivetrain Selection
o Types of drivetrains
o Types of wheels
o Drivetrain mechanics
o Best drivetrain for your team
o Maintenance
Ideal Drivetrain
• Gets your robot where it needs to be, when it
needs to be there
• Is robust and reliable
• Can push/pull objects and other robots
• Meets your strategy goals
• Fits with the game
• Can be built with your resources
• Rarely needs maintenance
• Can be fixed quickly
Basics
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Know your resources
Decide after kickoff:
Speed, power, shifting, mobility
Use the most powerful motors on drivetrain
Don’t drive ½ of your robot… WEIGH IT
DOWN!
• Break it early
• Give software team TIME to work
• Give drivers TIME to drive
Wheel Types: Traction
Standard wheels with varying amounts
of traction, stength and weight
AndyMark
Plaction
VEX Pro
AndyMark
Pneumatic
AndyMark KOP
Wheel Type: Holomonic
Special Wheels that allow the robot
to achieve Holomonic motion
Mecanum
Omni
Crab Module
Drivetrain Types: 2 Wheel Drive
Driven
Wheel
Motor(s)
Motor(s)
+ Easy to design
+ Easy to build
+ Light weight
+ Inexpensive
+ Agile
- Not much power
- Will not do well on ramps
- Easily turned
Caster,
Omni,
Slide
Drivetrain Types: 4 Wheel Drive
2 Gearboxes
Driven
Wheels
Motor(s)
Motor(s)
+ Easy to design
+ Easy to build
+ Inexpensive
+ Powerful
+ Sturdy and stable
- Not agile
- Turning is difficult
Chain or
belt
Driven
Wheels
Drivetrain Types: 4 Wheel Drive
4 Gearboxes
Drive
Wheels
Motor(s)
Motor(s)
+ Easy to design
+ Easy to build
+ Powerful
+ Sturdy and stable
+ Many options:
Mecanum, traction
- Heavy
- Costly
Motor(s)
Drive
Wheels
Motor(s)
Drivetrain Types: 6 Wheel Drive
2 Gearboxes
This is very
common in FRC
+ simple
+ easy
+ fast and powerful
+ agile
+ Easy to design
+ Easy to build
+ Powerful
+ Stable
+ Agile*
Gearbox
Gearbox
- Heavy **
- Expensive **
** - depending on
wheel type
Check out 1114’s
Kitbot on Steroids
• Simbotics.org
• Resources
•
Kitbot en
esteroides
*2 ways to be agile
1. Lower contact
point on center
wheel
2. Omni wheels on
front or back or
both
Drivetrain Types: Tank Treads
2 Gearboxes
Gearbox
Gearbox
+ Powerful
+ VERY Stable
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NOT AGILE
HEAVY
Inefficient
EXPENSIVE
Hard to maintain
Sole benefit: Ability to go over
things
For turning, lower the contact point
on center of track wheel
Will NOT push more than a wellcontrolled 6wd
Tank vs. Holomonic
Tank Drive
2 Degrees of Freedom
• Rotation
• Forward-back Motion
Holomonic Drive
3 Degrees of Freedom
• Rotation
• Forward-back Motion
• Side-side Motion
Drivetrain Type: Killough
4 wheel drive or 3 wheel drive
+ Immediate Turning
+ Simple Control – 4 wheel independent
- No brake
- Minimal pushing power
- Jittery ride, unless w/ dualies
- Incline difficulty
Drivetrain Type: Mecanum
+ Simple mechanisms
+ Immediate turn
+ Simple control – 4 wheel independent
- Minimal brake
- Minimal pushing power
- Should have a suspension
- Difficulty on inclines
Team 1346 Mechanum Drive
http://www.youtube.com/watch?v=xgTJcm9EVnE
Drivetrain Type: Crab/Swerve
> Each wheel rotates to steer
+ High-traction wheels
+ No friction losses in wheel-floor interface
+ Ability to push or hold position
+ Simple wheels
- Complex system to control and program
- Mechanical and control issues
- Difficult to drive
- Wheel turning delay
368’s Crab Drive in 2010
http://www.youtube.com/watch?v=q9uck-wRa_8
Drivetrain Top Speeds
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Game dependent
Determined by wheel size and gear ratios
Controllable top speed: 15 ft/sec
Average 1-speed rate: 9 ft/sec
Good pushing speed: 4-5 ft/sec
Center of Gravity (CG)
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Robot mass is represented at one point
Mobility increases when Cg is low and centered
High parts = light weight
Low parts = heavy (within reason)
Which is more Stable?
Gearboxes/Transmissions
• Gear ratio determines top speed and motor load
• Single Speed and Shifting options
• CIMple Box shipped in 2011 KOP
• 1 or 2 CIMs per gearbox
• 2011 4 CIMs allowed
• Must be greased to reduce friction
Belts
Don’t Stretch
+ Can reach far
- Need to buy in custom sizes
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Chain Selection
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#25
Lightweight
Easy to install
Smaller
Easy to derail
"Steches" over time
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#35
Allows for slop
Minimal "stretching"
Heavy duty
applications
More weight
Working with Chains
• Tensioning
o Critical to keep robot from throwing chains
o Must be accessible and easily adjustable
o Does not need to be used on ALL chains but should be
on drive systems
Look at other Designs!
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Competitions
chiefdelphi.com
Team websites
YouTube
thebluealliance.com
Presented by:
Paul Hines
John Hines
Drive Types + Wheel Pictures
www.AndyMark.com (FRC Supplier)
Swerve Drive Revolution Custom Frame
www.team221.com (FRC Supplier)
Check out 1114’s Kitbot on Steroids
• Simbotics.org
• Resources
•
Kitbot en esteroides