vex drive systems
DESCRIPTION
VEX Drive Systems. Presented by Chani Martin Lauren Froschauer Michelle. What Are They? Why Are They Important?. The drive system of a robot is the maneuverable based on which the articulation is built. Importance? If you’re robot doesn’t move, what’s the point? - PowerPoint PPT PresentationTRANSCRIPT
VEX Drive SystemsVEX Drive Systems
Presented by
Chani Martin
Lauren Froschauer
Michelle
Presented by
Chani Martin
Lauren Froschauer
Michelle
What Are They? Why Are They Important?
What Are They? Why Are They Important?
The drive system of a robot is the maneuverable based on which the articulation is built.
Importance? If you’re robot doesn’t move, what’s the point? If your robot is too slow, you lose If your robot is too weak, you lose
The drive system of a robot is the maneuverable based on which the articulation is built.
Importance? If you’re robot doesn’t move, what’s the point? If your robot is too slow, you lose If your robot is too weak, you lose
Types of Drive SystemsTypes of Drive Systems
Tank Drive
Omni- Drive
Crab Drive
Holonomic
Four Wheel
Six Wheel
Allows for
Strafing Better Turning
Type of BasesType of Bases
Drive train configurations Drive train configurations
simplerear wheel drive
simplefront wheel drive
simpleall wheel drive
simplecenter drive
6 wheeldrive
tracked drive There is no “right” answer!
swerve/ crab drive other?
Taken from Base Fundamentals
Beach Cities Robotics – Team 294Beach Cities Robotics – Team 294
Andrew KeisicAndrew Keisic
November 2009November 2009
Choosing a Drive SystemChoosing a Drive System
When designing, choose a drive system that will match your strategy for the game
Will you need to strafe? (Holonomic) Will you need torque? Friction? (Tank) Will you need speed? ( four-six wheel) How about quick turns? (Crab, Omni)
When designing, choose a drive system that will match your strategy for the game
Will you need to strafe? (Holonomic) Will you need torque? Friction? (Tank) Will you need speed? ( four-six wheel) How about quick turns? (Crab, Omni)
How to Optimize How to Optimize
Gear ratios Sensors (autonomous) Practice!!!
Gear ratios Sensors (autonomous) Practice!!!
Gear RatiosGear Ratios
There are four VEX spur gears 12 tooth 36 tooth 60 tooth 84 tooth
A VEX motor has a certain amount of torque and speed without gearing. You can gear
your robot to be stronger or faster with certain gear ratios.
There are four VEX spur gears 12 tooth 36 tooth 60 tooth 84 tooth
A VEX motor has a certain amount of torque and speed without gearing. You can gear
your robot to be stronger or faster with certain gear ratios.
QuickTime™ and a decompressor
are needed to see this picture.
QuickTime™ and a decompressor
are needed to see this picture.
Chain and sprockets are Related to gear ratios the same way
as spur gears
Gear Ratios Cont. Gear Ratios Cont.
Driven/drive gear Drive gear= on the same axle as the
motor; drives the next gear Driven Gear= -_- Idle gears do not matter, we do not
factor them into gear ratio formula Idle gears= gears between drive and
final driven gear
Driven/drive gear Drive gear= on the same axle as the
motor; drives the next gear Driven Gear= -_- Idle gears do not matter, we do not
factor them into gear ratio formula Idle gears= gears between drive and
final driven gear
Speed Vs. TorqueSpeed Vs. Torque Driven/ drive gear Big gear/ small gear ; small gear drives big
gear , big gear turns slower than small gear= torque= power
Small gear/ big gear ; big gear drives small gear; small gear turns faster than big gear= speed
Driven/ drive gear Big gear/ small gear ; small gear drives big
gear , big gear turns slower than small gear= torque= power
Small gear/ big gear ; big gear drives small gear; small gear turns faster than big gear= speed
Examples Examples
Use the number of teeth 84/ 60 =7:5= big/ small = torque 12/84 = 1:7=small to big = speed Why? When the 60 tooth gear spins
once, the 84 tooth gear will spin less than once.
When the 84 tooth gear spins once, the 12 tooth gear will spin 7 times
Use the number of teeth 84/ 60 =7:5= big/ small = torque 12/84 = 1:7=small to big = speed Why? When the 60 tooth gear spins
once, the 84 tooth gear will spin less than once.
When the 84 tooth gear spins once, the 12 tooth gear will spin 7 times
To calculate Gear RatiosDivide the tooth numbers of the
Driven/ Drive gear
Red = DirectionOf Wheel Force
Green= Direction of wheel slip
The Force Applied by wheels must be greater than resisting force of friction between wheels and ground
Torque= F* DTapplying= Fwheel* Width/2Tresisting = Ffriction*Length/2
Force at Wheel= torque of motor* gear ratio* radius of wheel
Ffriction= coefficient of friction*weight/ # of wheels
More About TurningMore About Turning
Base Base FundamentalsFundamentalsBase Base FundamentalsFundamentalsBeach Cities Robotics – Team Beach Cities Robotics – Team 294294
Andrew KeisicAndrew Keisic
November 2009November 2009
Beach Cities Robotics – Team Beach Cities Robotics – Team 294294
Andrew KeisicAndrew Keisic
November 2009November 2009
Center of GravityCenter of Gravity
A point in space where gravity acts Why it’s important?
Determines the balance and stability of an object
A point in space where gravity acts Why it’s important?
Determines the balance and stability of an object
Center of GravityCenter of Gravity
What robot is the most stable? The least? What robot is the most stable? The least?How do you know?
What systems are inherently stable?
Center of GravityCenter of Gravity
Putting math behind intuition Putting math behind intuition
Stability Triangle
h
b2b1
α1
α2
⎟⎠
⎞⎜⎝
⎛= −
h
b111 tanα
⎟⎠
⎞⎜⎝
⎛= −
h
b212 tanα
Center of GravityCenter of Gravity Limit of stability is determined by the
CG location In other words – the maximum ramp
angle of a stationary robot
Limit of stability is determined by the CG location
In other words – the maximum ramp
angle of a stationary robot
⎟⎠
⎞⎜⎝
⎛== −
h
b2122 tanαβ⎟
⎠
⎞⎜⎝
⎛== −
h
b1111 tanαβ ⎟
⎠
⎞⎜⎝
⎛== −
h
b1111 tanαβ
β1β2
α1
α2
Center of GravityCenter of Gravity Why keep it low?
Lowering the center of gravity maximizes alpha!
Why keep it low? Lowering the center of gravity maximizes
alpha!Stability Triangle
h
b2b1
α1
α2
Watch Your Center of GravityWatch Your Center of GravityThe bigger alpha is, the more stable theRobot. Having either a large alpha and good turning ability are trade offs, just like torque and speed.
Sensors Sensors
Ultrasonic Range Finder
Optical Shaft Encoders
Line Trackers
Ultrasonic Range Finder
Optical Shaft Encoders
Line Trackers
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QuickTime™ and a decompressor
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QuickTime™ and a decompressor
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Ultrasonic Range FinderUltrasonic Range Finder
Measures distances and locates obstacles/objects
Used in autonomous
Measures distances and locates obstacles/objects
Used in autonomous
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QuickTime™ and a decompressor
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Optical Shaft EncodersOptical Shaft Encoders
Measures direction of rotation and position of shaft
Used in calculation for speed of shaft and distance traveled
Measures direction of rotation and position of shaft
Used in calculation for speed of shaft and distance traveled
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Line TrackersLine Trackers
Allows robot to follow a black line on a white surface
Perfect for autonomous relocation Usually, used three in a row
Allows robot to follow a black line on a white surface
Perfect for autonomous relocation Usually, used three in a row
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