Basics Drive Types Resources Torque Traction Mobility Speed - PowerPoint PPT Presentation

 Importance  Basics  Drive Types  Resources  Torque  Traction  Mobility  Speed

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 5 minutes

 Know your resources  Decide after kickoff: › Speed, power, shifting, mobility  Use most powerful motors on drive train (usually)  Test early, with full weight, including destructive  Give software team TIME to work  Give drivers TIME to drive

 Speed (Measured in ft/sec)  Acceleration (Measured in ft/sec 2 )  Maneuverability (Measured in turning arc, degrees of freedom)  Turning Speed (measured in degrees/sec)  Traction (Measured in lb)  T orque (Measured in ft-lb)  Weight (Measured in lb)  Cost (Measured by $ spent)  Efficiency (Measured in % Power)  Mobility (the ease with which the robot can be efficiently driven)  Controllability (Measured by rating – yuck)  Simplicity (Measured by time to fix, time to build)  Robustness (Measured by life time, # of impacts, force needed to break)

The Standard in FIRST

Driven Wheel Motor(s) Motor(s) + Easy to design + Easy to build + Light weight + Inexpensive + Agile - Not much power Caster - Will not do well on ramps - Less able to hold position - Horrid traction

Ziff 2.0

Driven Wheels Motor(s) Motor(s) The most standard Chain or belt drive train in + Easy to design FIRST + Easy to build + Inexpensive + Powerful + Sturdy and stable 1 or 2 motors per side Driven - Not agile Wheels -Turning is difficult -Adjustments needed

Carlson X Icarus

Driven Wheels Motor(s) Motor(s) + Easy to design + Easy to build + Powerful + Sturdy and stable + Many options Mecanum, traction - Heavy-ish Driven - Costly-ish Wheels Motor(s) Motor(s)

+ Easy to design + Easy to build + Powerful + Stable + Agile* *2 ways to be agile + simple Gearbox Gearbox + easy A) Lower contact point + fast and powerful on center wheel - Heavy ** + agile B) Omni wheels on - Expensive ** front or back or 1 or 2 motors per both ** - depending on side wheel type

Boris

+ Powerful + Stable + Agile* Benefits: Ability to go over things; Gearbox Gearbox high traction - HEAVY *2 ways to be more agile - EXPENSIVE - INNEFICIENT A) Lower contact point on center - HORRID TURNING wheel B) Omni wheels on front or back or both

Tank Tread Crab - Swerve Holonomic – Killough – Omni 3 wheel Mecanum Mouseball

2-4 motors per side Gearbox Gearbox + Powerful + VERY Stable - NOT AGILE - HEAVY Benefits: Ability to go over - Inefficient things; even higher traction - EXPENSIVE - Hard to maintain For turning, lower the contact - Even worse point on center of track turning. wheel Will NOT push more than a well- controlled 6wd without major gearing-down

 4 or 3 wheel drive + Simple Mechanics + Immediate Turning + Simple Control – 4 wheel independent No brake - Minimal pushing power - Jittery ride, unless w/ dualies - Incline difficulty - Max 50% Efficiency -

+ Simple mechanisms + Immediate turn + Simple control – 4 wheel independent - Minimal brake - OK pushing power - Expensive - Heavy - 67% Forward and reverse efficiency, 33% sideways Has issues going up ramps

Thor

 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 - Expensive - Lots of machining required - Minimum 5 motors (theoretically 4) -

 One wheel steers  Various types  Lightweight Gearbox Gearbox  Fast  Non-standard › (design intensive)  Examples: › 16 in 2008 › 67 in 2005

 More for fun!  Very maneuverable  Expensive, high-maintenance, low pushing power

 Ackerman  Go Cart + Not many - Complex system to control and program - Going backward is interesting - Complex to do well - No real advantage in FIRST

 Torque = Force X Distance  Essentially, a measure of rotational force – how hard the wheel turns  Torque X Speed = Power  Controlled with gearboxes  Torque and speed have inverse relationship – if you double the speed, you halve the torque  Standard AndyMark Toughbox gearbox comes in ratio 12.75:1  Measured in Ft-Lbs

 CIM Motor: › .25 ft-lbs of torque › 4614 RPM  After Gearing Down: › 3.18 ft-lbs torque › 362 RPM

 Static vs Dynamic (^10% lower) › Once you slip, you will slide easier › Design encoders into your system › Dynamic breaking & traction control  Pushing force = Weight * m › m = friction coefficient Normal Force Pushing (weight) Static friction coefficients Force m = 0.05 = Self Lubricating Wheels (Lunacy Traction anyone?) m = 0.1 = caster (free spinning) m = 0.3 = hard plastic m = 0.8 = smooth rubber, 80A durometer m = 1.0 = sticky rubber, 70A durometer m = 1.1 = conveyor treads

 Move x feet in any direction in a second  Generally speaking, the more mobile your robot is, the less it can resist a push Higher Mobility Higher Traction

 Robot mass is represented at one point  Mobility increases when Cg is low and centered  High parts = light weight  Low parts = heavy (within reason)  ROBOTS TIP! Battery motors pump, etc. Ms Mobile Battery motors Mr Fall pump, etc. Guy

 Game dependent  Stats for 2008 (very speedy year): › max: 20 ft/sec › Controllable top speed: 15 ft/sec › Good pushing speed: 5 ft/sec  Toughbox – 9 FPS

 Ground Interface (Wheels, Treads)  Shaft (Live, Dead)  Gears, Sprockets, and Pulleys  Chains, Belts, T ensioners  Bearings and Bushings  Gearbox  Motor  Sensors (encoders, counters)  Speed Controller

Omni Mecanum Wheels Wheels Provide Rollers propulsion in positioned at the forward 45 degree direction while allowing wheel centerline, and reverse angles from for easy sideways movements providing omnidirectional motion. Traction Standard Wheels Wheels Wheels paired with Roughtop or Wedgetop tread material to make a strong and high-traction wheel.

 Dead Shaft  Live Shaft

Finally, the fun part!

 Thor’s First Steps  The Power of Traction Control  The Nonadrive

 Drive Trains are necessary and offer considerable competitive advantage  A well-built drive train offers flexibility, power, and robustness  A non-reliable or non-repairable drive base will turn your robot into a boat anchor  Good drive bases win consistently  Reliable drive bases win awards  Well-controlled, robust drive bases win Championships

Andy Baker Brian Graham Mike Saunders