Purpose of this Presentation
• Drivetrain SelectionoTypes of drivetrainsoTypes of wheelsoDrivetrain mechanicsoBest drivetrain for your teamoMaintenance
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
• 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 KOP
VEX Pro
AndyMark Plaction
AndyMark Pneumatic
Wheel Type: Holomonic
Special Wheels that allow the robot to achieve Holomonic motion
Mecanum OmniCrab Module
Caster,Omni,Slide
DrivenWheel
+ Easy to design+ Easy to build+ Light weight+ Inexpensive+ Agile
- Not much power- Will not do well on ramps - Easily turned
Motor(s)Motor(s)
Drivetrain Types: 2 Wheel Drive
Chain or belt
DrivenWheels
+ Easy to design+ Easy to build+ Inexpensive+ Powerful+ Sturdy and stable
- Not agile- Turning is difficult
Motor(s)Motor(s)
DrivenWheels
Drivetrain Types: 4 Wheel Drive2 Gearboxes
DriveWheels
+ Easy to design+ Easy to build+ Powerful+ Sturdy and stable+ Many options:Mecanum, traction
- Heavy- Costly
Motor(s)Motor(s)
DriveWheels
Motor(s) Motor(s)
Drivetrain Types: 4 Wheel Drive4 Gearboxes
Gearbox Gearbox
+ Easy to design+ Easy to build+ Powerful+ Stable+ Agile*
- Heavy ** - Expensive **
** - depending on wheel type
*2 ways to be agile
1. Lower contact point on center wheel
2. Omni wheels on front or back or both
This is very common in FRC
+ simple+ easy+ fast and powerful+ agile
Drivetrain Types: 6 Wheel Drive2 Gearboxes
Check out 1114’s Kitbot on Steroids• Simbotics.org
• Resources• Kitbot en
esteroides
Gearbox Gearbox
+ Powerful+ VERY Stable
- NOT AGILE - HEAVY - Inefficient - EXPENSIVE - Hard to maintain For turning, lower the contact point
on center of track wheel
Sole benefit: Ability to go over things
Will NOT push more than a well-controlled 6wd
Drivetrain Types: Tank Treads2 Gearboxes
Tank vs. Holomonic
Tank Drive2 Degrees of Freedom• Rotation• Forward-back Motion
Holomonic Drive3 Degrees of Freedom• Rotation• Forward-back Motion• Side-side Motion
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: Killough
+ Simple mechanisms+ Immediate turn+ Simple control – 4 wheel independent- Minimal brake- Minimal pushing power- Should have a suspension- Difficulty on inclines
Drivetrain Type: Mecanum
http://www.youtube.com/watch?v=xgTJcm9EVnE
Team 1346 Mechanum Drive
> 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
Drivetrain Type: Crab/Swerve
368’s Crab Drive in 2010
http://www.youtube.com/watch?v=q9uck-wRa_8
• 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
Drivetrain Top Speeds
Center of Gravity (CG)
o Robot mass is represented at one pointo Mobility increases when Cg is low and
centeredo High parts = light weighto 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
Chain Selection
#25 + Lightweight + Easy to install + Smaller - Easy to derail - "Steches" over time
#35 + Allows for slop + Minimal "stretching" + Heavy duty applications - More weight
Working with Chains
• Tensioningo Critical to keep robot from throwing chainso Must be accessible and easily adjustableo Does not need to be used on ALL chains but
should be on drive systems
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