FIRST Tech Challenge Drive Train Testing

By Techno Warriors Advanced

FTC #3486

Topics Project Description Requirements Basics – Drive Train Design Drive Train Types Testing Science/Engineering Conclusions

Project Description Built and tested seven drive train

designs Simulated FTC match environments Tested each design with added weight

to mimic various robot weights Compiled and analyzed data to find

ideal configurations for each test

Requirements

Meets strategy goals for the game Is built from available resources

› Time › Cost› Tools for fabrication› Part 1 of game manual

Rarely needs maintenance Is repairable within 4 minutes Uses minimal amount of space

Basics – Drive Train Design Decide strategy after kickoff

› Speed› Power› Mobility

Decide how many motors will be allotted for drive train

Decide robot weight› Traction› Mobility› Speed› Offensive/Defensive ability

Basics – Drive Train Design cont. Build for durability and test

› Find weak points› Practice driving› Have spare parts and assemblies

Develop a project plan› Allot time for development and building

Learn technology › Know motor capabilities and limitations› Know electrical capabilities and limitations.

Drive Train Types

•Nimble: 2 wheel drive + 2 omni caster wheels•Basic: 4 wheel drive, not connected•Unity: 4 wheel drive, connected•Robust: 10 wheel drive•Whirlwind: 6 wheel drive

• AndyMark Wedgetop and Performance Treads

•Track: 4 motors, connected•Direction: 4 motors, not connected

Nimble: 2 wheel drive + 2 Omni caster wheels

Omni caster wheels

Driven wheels

MotorMotor

This drive train uses two direct drive 4” wheels with two 3” omni caster wheels. This robot has a base weight of 7 lbs due to its 10”x18” 80/20 frame.

Basic: 4 wheel drive, not connected

DrivenWheels

MotorMotor

Motor Motor

This drive train uses four direct drive 4” wheels that are not connected to each other. This robot has a base weight of 7 lbs due to its 10”x18” 80/20 frame.

Unity: 4 wheel drive, connected

DrivenWheels

MotorMotor

Motor Motor

Chain Chain

This drive train uses four direct drive 4” wheels that are connected to each other using chain (not drawn in Creo). This robot has a base weight of 9 lbs due to its 10”x18” 80/20 frame plus added chain and sprockets.

Robust: 10 wheel drive

Motor

Motor

Motor

Motor

Gears Gears

This drive train uses 10 chain driven 3” wheels that are geared together with the 4 outer wheels raised. This robot was our competition robot from the 2014-2015 season which weighed 55 lbs.

Whirlwind: 6 wheel drive, 2 tread types

Motor

Motor

Motor

Motor

This drive train uses 6 chain driven 4” wheels with the outer wheels being the AndyMark omni wheels and the inner wheels using either the AndyMark Performance Tread or the AndyMark Wedgetop Tread (tested separately). This robot had a base weight of 22.5 lbs.

Tracks: Track drive, 4 motors

Motor

Motor

Motor

Motor

This drive train uses 4 direct driven 3” wheels wrapped with Tetrix tread. This robot had a base weight of 9 lbs due to the 10”x18” 80/20 frame.

Direction: 4 motors, not connected

Om

ni

Om

ni

Om

ni

Om

ni

Mot

or

Mot

orMotor

Motor

This drive train uses 4 direct driven 3” omni wheels. Each wheel was driven individually to allow for multidirectional travel. This robot had a base weight of 7 lbs.

Testing

Straight Line Speed Test Pull Test Side Drag Test Spin Test Ramp Test

Testing

Each test was preformed on standard field tiles. The robot was weighed and tested at 10, 20, 30 and 40 pounds in addition to the weight of the robot itself.

Straight Line Speed Test The Straight Line Speed Test tested the robot

on how fast it would travel 16 feet. The testing area had a starting area to allow

the robot to reach full speed prior to the course.

Total robot amps were recorded for each run. Time to drive the 16 feet was recorded for

each run. At least 4 tests were recorded for consistent

results.

Pull Test The Pull Test tested how much weight

the robot could pull. Total robot amps were recorded for

each run. The amount weight lifted was recorded

for each test. The weight lifted was increased until

the wheels slipped or the motors stalled.

Side Drag Test

The Side Drag Test tested how much weight it took to pull the robot sideways.

The amount of weight to pull the robot was recorded for each test.

Weight was added until the robot was pulled sideways.

Spin Test The Spin Test tested how fast the robot

could spin 360 degrees. Total robot amps were recorded for each

run. Time taken to spin 360 degrees was

recorded for each run. At least 4 tests were recorded for

consistent results.

Ramp Test

The Ramp Test tested if the robot could climb a ramp.

The ramp was a standard FTC ramp from the Cascade Effect Game.

Pass/Fail was given if the robot could drive up the ramp.

Science/Engineering

Estimated Robot Speed vs. Results

Estimated Robot Speed

Wheel Diameter * Pi * Motor speed = Inch/min

4" * 3.14 * 150 RPM= 1884 inches/min 1884 inches/min /60 sec = 31.4 inches/sec

3" * 3.14 * 150 RPM = 1413 inches/min1413 inches/min /60 sec = 23.5 inches/sec

Actual Speed

Tested Distance = 192 inches

Theoretical time to run course with 4" wheels192 inches / 31.4 inches/sec = 6.1 seconds

Theoretical time to run course with 3" wheels

192 inches / 23.5 inches/sec = 8.1 seconds

Most robots at minimum weight tested at or faster than predicted speed.

Conclusions

Test Data› Straight Line Speed Test

(Seconds/Amps)› Pull Test (Pounds/Amps)› Side Drag Test (Pounds)› Spin Test (Time/Amps)

Overall Robot Performance

SPEED

TES

T R

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ULT

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Test Distance 16 Feet

SPEED

TES

T R

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(CO

NTIN

UED

)

PU

LL TES

T R

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ULT

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Track drive uses 3” wheels, and, therefore, gained at least 25% of power advantage compared to 4” wheels

PU

LL TES

T R

ES

ULT

S

(CO

NTIN

UED

)

SID

E D

RA

G T

ES

T R

ES

ULT

S

SPIN

TES

T R

ES

ULT

S

SPIN

TES

T R

ES

ULT

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(CO

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UED

)

Nimble: 2 wheel drive + 2 Omni caster wheels

+ Easy to design+ Easy to build+ Lightweight+ Inexpensive+ Long battery life

- Underpowered drive train- Will not do well on ramps- Easily pushed by other robots- Not effective for defense- Not able to support much weight

+

--- -- Maneuverability

Basic: 4 wheel drive, not connected+ Easy to design+ Easy to build+ Lightweight+ Inexpensive+ Long battery life+ Able to hold position

- Not utilizing full potential out of all the motors because they are not connected- Not effective for defense- Not able to support much

weight and move effectively

= Decent on ramps= Decent maneuverability

+

-

=

Unity: 4 wheel drive, connected+ Relatively easy to design+ Relatively easy to build+ Light weight+ Able to holding position+ Preforms well on ramps+ Utilizes full potential of motors because they are connected

- Not able to support much weight and move effectively

= Inexpensive = Decent Maneuverability= Battery life depends on weight= Effective for defense

+

-=

Robust: 10 wheel drive

+ Does well on ramps+ Utilizes full potential out of all the motors + Very effective for defense+ Supports robust robot well

- Short battery life- Difficult to design- Difficult to build- Expensive

= Decent Maneuverability= Weight neutral

+

-=

Whirlwind: 6 wheel drive, 2 tread types

+ Great at holding position+ Does well on ramps+ Utilizes full potential out of all the motors + Very effective for defense+ Excellent battery life+ Will support high gear ratio

- Difficult to design- Difficult to build- Very expensive

= Weight neutral

+

-=

++ ++ Maneuverability: spins on axis well++ Supports robust robot well

Tracks: Track drive, 4 motors

+ Easy to design+ Easy to build+ Lightweight+ Long battery life+ Able to hold position

- Inconsistent turns make autonomous extremely difficult- Drive train needs to be geared up to reach

competitive speed- Vulnerable, needs to be protected

= Does decently on ramps with track treads= Average Maneuverability= Effective for defense= Cost neutral

+

-

=

Direction: Holonomic

+ Long battery life+ Inexpensive+ High Maneuverability

- Extremely difficult to program- Not able to hold position- Slow- Not at all effective for defense- Cannot go up ramp

= Moderate weight = Moderate to design= Moderate to build

+

-

=

Quick Reference Table

Detailed Information

Requirements

Requirements The drivetrain can define a robot and is the most important

element of a design; the strength of the robot's drivetrain can heavily influence its overall performance.

The drivetrain must:meet your strategy goals for the game › speed: The robot must be able to surpass the competition in any

direction at any time.› traction: The robot must be able to effectively grip the various field

elements without damaging the playing field or limiting maneuverability.

› maneuverability: The robot must be able to quickly navigate the field, rotate on its axis, and escape out of harm’s way.

› power: The robot must be able to conserve power usage to ensure maximum overall performance during a match.

› offense/defense: The robot must be able to meet strategic objectives depending on team preference.

› weight: The robot weight should maximize motor efficiency without compromising defensive/offensive abilities.

Requirements(continued) be built with available resources

› budget: The drive train construction costs should not exceed the team-defined boundaries of the budget.

› tools required: The drive train should be designed to be built only with tools that each team actually has. (No rocket boosters unless you are sponsored by NASA)

› time: The drive train should be easily assembled/dissembled for maintenance within a short time span.

rarely needs maintenance› durability: The drive train should be constructed to last so that repairs

are minimal. The drive train must be protected from harm.› testing: Thoroughly test the drive train during construction to ensure

that it can handle match conditions. can be fixed within 4 minutes

› easily replace motors between matches› easy to access critical components

Uses minimal amount of space› The drive train fits in designated space allotted by the system

envelope

Basics

BasicsBrainstorming and Design resources: Decide strategy after kickoff. What will you focus on?

› Speed: › Power› Mobility

Decide how many motors you will use on drivetrain › 4 motors is ideal (2 weakens a design and 6 causes connection issues)› chain/gear motors together to maximize power › Wire motors on separate ports on motor controllers to maximize power

Robot weight› What weight will maximize

traction mobility speed defense (limit other robots pushing while playing offense)

Durability › put the drivetrain under stress to test the durability› identify weak points and correct them› driver practice› spare parts and assemblies

Develop a project plan› allot time for design, build, testing, software and driver practice

Basics Technology

› motor capabilities and limitations› AndyMark NeveRest 40 Motor (am-2964)

Performance Specs: Gearbox Reduction: 40:1 Voltage: 12 volt DC No Load Free Speed, at gearbox output shaft: 160 rpm No Load Free Speed, motor only: 6,600 rpm Gearbox Output Power: 14W Stall Torque: 350 oz-in Stall Current: 11.5 amps Force Needed to Break Gearbox: 1478 oz-in Minimum torque needed to back drive: 12.8 oz-in Output pulse per revolution of Output Shaft (ppr): 1120 (280 rises of Channel A) Output pulse per revolution of encoder shaft (ppr): 28 (7 rises of Channel A)

Performance Specs, mounted to AndyMark dyno: Max Speed (under load of dyno): 129 rpm No Load Current (under load of dyno): 0.4 amps Stall Current: 11.5 amps Stall Torque: 396 oz-in Max Output Power: 15 Watts Time to Failure at Stall: 2 minutes, 54 seconds Motor Case Temperature at Failure: 190 degrees F

› electrical capabilities and limitations Each motor controller should only power 1 drive train motor. Never connect more than motor to a motor controller port.

Drivetrain Details

•Nimble: 2 wheel drive + 2 omni caster wheels•Basic: 4 wheel drive, not connected•Unity: 4 wheel drive, connected•Robust: 10 wheel drive•Whirlwind: 6 wheel drive

• AndyMark Wedgetop and Performance Treads

•Track: 4 motors, connected•Direction: 4 motors, not connected

Nimble: Description and Details

This robot has two motors that directly drive two wheels. The drive wheels are 4 inch Tetrix wheels, and the non-powered wheels are 3 inch omni caster wheels.

Haiku: Nimble...This nimble robot...It can move, but not too well;Try it with low weight.

Nimble: Specifications

two AndyMark NeveRest 40 motors two 4in Tetrix wheels two 3in Tetrix omni wheels two 1010 aluminum extrusions 18"

long five 1010 aluminum extrusions 10"

long

Nimble: PTC Creo Design

Nimble: Straight Line Speed Data

Nimble: Pull Test Data

Nimble: Side Drag Test Data

Nimble: Spin Test Data

Nimble: Summary

This drive train is easily constructed, but not necessarily the best choice for any robot. Due to a low weight, it draws less amps than other drive trains, promoting good battery life. Unfortunately, nothing else stands out. Its straight line speed is only average, it has low pushing power, it can be easily pushed around by an opposing robot, and it has trouble spinning under any weight. Overall, this drive train is not recommended for any game.

Basic: Description and Details

This robot is powered by four motors that directly drive the four 4" tetrix wheels. The motors on each side are not chained together in this design.

Haiku: Basic...It may seem basic...Connect the wheels with chain please...That might work better.

Basic: Specifications

Four AndyMark NeveRest 40 motors Four 4" Tetrix wheels two 1010 aluminum extrusions 18"

long five 1010 aluminum extrusions 10"

long

Basic: PTC Creo Design

Basic: Straight Line Speed Data

Basic: Pull Test Data

Basic: Side Drag Test Data

Basic: Spin Test Data

Basic: Summary

This drive train can maneuver around the field under heavy weight, but it is only at average or below average speeds. It is easily constructed and does not draw a large number of amps during movement. It can push/pull an average weight, but it is easily pushed around by other robots. It is thus effective and passable, but not the absolute best option for any task. It is recommended to connect the wheels together as in our 4 Wheel - Connected drive train configuration.

Unity: Description and Details

This robot is very similar to the previous robot in that four motors are directly driving four 4" tetrix wheels, but this time the motors are chained together on each side.

Haiku: Unity...Together we spin...Connected by lengths of chain...Unity is key.

Unity: Specifications

four AndyMark NeveRest motors four 4in Tetrix wheels four Tetrix sprockets two sets of .25 Tetrix chain

Unity: PTC Creo Design

Unity: Straight Line Speed Data

Unity: Pull Test Data

Unity: Side Drag Test Data

Unity: Spin Test Data

Unity: Summary

This drive train can maneuver around the field under heavy weight, but only at average or below average speeds. It is easily constructed and does not draw a large number of amps during movement. It can push/pull an average weight, but it is easily pushed around by other robots. It is thus effective and passable, but not the absolute best option for any task.

Robust: Description and Details

For this design, we used an already assembled robot from the previous year instead of building a new drive train for testing. This design has five wheels on each side that are driven by chain with a total of four motors. The middle three wheels are in contact with the ground at all times and the outer two are raised up off of the ground and are used for stabilization and to help the robot go up a ramp with ease.

Haiku: Robust...This robot is stout;Dieting plans have been tried.They were all failures.

Robust: Specifications

four AndyMark NeveRest 40 motors ten 3in Tetrix wheels four tooth gears six tooth gears four sets of .25 Tetrix chain twelve Tetrix sprockets

Robust: PTC Creo Design

Robust: Testing Data

Robot test weight - 55 lbs.Straight line test (@55 lbs) - 6.4 Seconds

Stall Weight test (@55 lbs) - 25 lbs.

Slide test (@55 lbs)- 65 lbs.

Ramp test - Pass

Spin Test (@55 lbs) - 2.1 Seconds

NOTE: This was our competition robot from last year, so we were unable to fully collect data for various weights.

Robust: Summary

In summary, this robot is a very strong defensive bot, and is not easily pushed around the field. It is also very stable and not easily tipped. However, it draws a significant amount of current and so the battery quickly drains during a match. It is also expensive and rather complicated to build.

Whirlwind: Description and Details

This drive train consists of four motors that are driving a total of six wheels with three on each side by chain. Four of the six wheels in this design are 4" Omni wheels from AndyMark and the remaining two are AndyMark high performance wheels. We tested the wedgetop treads and the performance treads separately, as demonstrated by the data below.

Haiku: Whirlwind...It spins really fast.Like a furious whirlwind...Super-duper spin.

Whirlwind: Specifications

four AndyMark NeveRest 40 motors two AndyMark high performance

wheels four AndyMark Omni wheels two sets of .25 Tetrix chain two 1010 aluminum extrusions 18"

long five 1010 aluminum extrusions 10"

long six 1010 aluminum extrusions 4" long

Whirlwind: PTC Creo Design

Whirlwind: Straight Line Speed Data Wedgetop Tread:

Whirlwind: Pull Test DataWedgetop Tread:

Whirlwind: Side Drag Test DataWedgetop Tread:

Whirlwind: Spin Test Data Wedgetop Tread:

Whirlwind: Straight Line Speed Data Performance Tread:

Whirlwind: Pull Test DataPerformance Tread:

Whirlwind: Side Drag Test DataPerformance Tread:

Whirlwind: Spin Test Data Performance Tread:

Whirlwind: Summary

It was incredibly good at spinning no matter how much weight we added, making it very maneuverable. This would be a good offensive robot with decent defensive capabilities, as it took a lot of weight to move it. It is also optimal to gear up this drive train for different strategies, as its overall effective performance would carry over to any strategy.

Tracks: Description and Details

This robot is powered by four motors that are connected together by tetrix conveyor/tank tread.

Haiku: Tracks...Tracks are quite nifty;They can pull a lot of weight;But don't go up ramps.

Tracks: Specifications

four AndyMark NeveRest 40 motors four Tetrix tread sprockets two sets of Tetrix tank tread two 1010 aluminum extrusions 18"

long five 1010 aluminum extrusions 10"

long

Tracks: PTC Creo Design

Tracks: Straight Line Speed Data

Tracks: Pull Test Data

Tracks: Side Drag Test Data

Tracks: Spin Test Data

Tracks: Summary

This drive train performed well in all but one of the tests. Due to its 3" wheels, it's average speed is lower than the other drive train which all had 4" wheels (except for the holonomic). It successfully pulled 45 lbs at max added weight, giving it the top score in push/pull power. It was not very efficient at power usage, and it could not travel up the ramp at any weight. Overall, this drive train is useful for pushing power, but if used, it must be highly protected and concealed within the robot frame so that the tracks do not break upon contact with an opposing robot.

Direction: Description and Details

This robot is a 4 wheel holonomic drive robot. Each wheel is powered independently to allow for multi-directional travel.

Haiku: Direction...My path I know not;Anywhere I can travel.But how do I choose...

Direction: Specifications

four AndyMark motors four 3in Tetrix omni wheels 1 18" square base plate - 1/8"

aluminum

Direction: PTC Creo Design

Direction: Straight Line Speed Data

Direction: Pull Test Data

Direction: Side Drag Test Data

Direction: Spin Test Data

Direction: Summary

This robot is highly agile at low weight, but it struggles under high stress. It is unable to go up a ramp or pull much weight, so it is only good at scuttling around. This drive train can be easily pushed around, so it's not recommended for defensive strategies.

FIRST Tech Challenge Drive Train Testing

Created by FTC Team #3486

Techno Warriors Advanced

Feel free to contact us!Engineering Notebook: bit.ly/FTC3486

Email: twa3486@gmail.com

Twitter: @technowarriors