21-12-2012, 12:44 PM
FIRST Robotics Drive Systems
FIRST Robotics.ppt (Size: 2.64 MB / Downloads: 35)
Importance
The best drive train…
is more important than anything else on the robot
meets your strategy goals
can be built with your resources
rarely needs maintenance
can be fixed within 4 minutes
is more important than anything else on the robot
Basics
Know your resources
Decide after kickoff:
Speed, power, shifting, mobility
Use most powerful motors on drive train
Don’t drive ½ of your robot… WEIGH IT DOWN!
Break it early
Give software team TIME to work
Give drivers TIME to drive
Drive Types:Holonomic - Killough
4 wheel drive or 3 wheel drive
Stephen Killough, 1994
+ Simple Mechanics
+ Immediate Turning
+ Simple Control – 4 wheel independent
No brake
Minimal pushing power
Jittery ride, unless w/ dualies
Incline difficulty
Drive Types:Mecanum
+ Simple mechanisms
+ Immediate turn
+ Simple control – 4 wheel independent
Minimal brake
OK pushing power
Needs a suspension
Difficulty on inclines
Drive Type:Swerve or crab steering
High-traction wheels
Each wheel rotates to steer
+ 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
Omnidirectional drive systems
Mobility
Move +/- 1 foot in any direction in under 1 second
Generally speaking, the more mobile your robot is, the less it can resist a push
Center of gravity (Cg)
Robot mass is represented at one point
Mobility increases when Cg is low and centered
High parts = light weight
Low parts = heavy (within reason
Timing
Get something driving early
End of week 2
Practice for operators
Lessons learned for electrical
Strategy lessons
Continuously improve
Good enough is not good enough
Finish final drivetrain by week 4