FIRST Tech Challenge Drive Train Testing By Techno

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 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 › Speed › Power › Mobility after kickoff � 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 • Andy. Mark Wedgetop and Performance Treads • Track: 4 motors, connected • Direction: 4 motors, not connected

Nimble: 2 wheel drive + Omni caster wheels Motor 2 Motor Driven wheels Omni caster wheels 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”x 18” 80/20 frame.

Basic: 4 wheel drive, not connected Motor Driven. W heels 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”x 18” 80/20 frame.

Unity: 4 wheel drive, connected Motor Chain Motor Driven. W heels Chain Motor 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”x 18” 80/20 frame plus added chain and sprockets.

Robust: 10 wheel drive Motor Gears Motor 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 This drive train uses 6 chain driven 4” wheels with the outer wheels being the Andy. Mark omni wheels and the inner wheels using either the Andy. Mark Performance Tread or the Andy. Mark Wedgetop Tread (tested separately). This robot had a base weight of 22. 5 lbs.

Tracks: Track drive, 4 motors 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”x 18” 80/20 frame.

Direction: 4 motors, not connected O O n m n i m i M ot o r or ot M M ot or i n m O M or ot i n m O 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 /60 sec = 31. 4 inches/sec 3" * 3. 14 * 150 RPM = 1413 inches/min /60 sec = 23. 5 inches/sec

Actual Speed Tested Distance = 192 inches Theoretical time to run course with 4" wheels 192 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 TEST RESULTS Test Distance 16 Feet

SPEED TEST RESULTS (CONTINUED)

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

PULL TEST RESULTS (CONTINUED)

SIDE DRAG TEST RESULTS

SPIN TEST RESULTS

SPIN TEST RESULTS (CONTINUED)

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 = Decent on ramps = Decent maneuverability - 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

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 = Inexpensive = Decent Maneuverability = Battery life depends on weight = Effective for defense - Not able to support much weight and move effectively

Robust: 10 wheel drive + = - + Does well on ramps + Utilizes full potential out of all the motors + Very effective for defense + Supports robust robot well = Decent Maneuverability = Weight neutral - Short battery life - Difficult to design - Difficult to build - Expensive

Whirlwind: 6 wheel drive, 2 tread types ++ + = - ++ Maneuverability: spins on axis well ++ Supports robust robot well + 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 = Weight neutral - Difficult to design - Difficult to build - Very expensive

Tracks: Track drive, 4 motors + = - + Easy to design + Easy to build + Lightweight + Long battery life + Able to hold position = Does decently on ramps with track treads = Average Maneuverability = Effective for defense = Cost neutral - Inconsistent turns make autonomous extremely difficult - Drive train needs to be geared up to reach competitive speed - Vulnerable, needs to be protected

Direction: Holonomic + = - + Long battery life + Inexpensive + High Maneuverability = Moderate weight = Moderate to design = Moderate to build - Extremely difficult to program - Not able to hold position - Slow - Not at all effective for defense - Cannot go up ramp

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 teamdefined 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

Basics Brainstorming 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 › Andy. Mark Neve. Rest 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: 14 W � 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 Andy. Mark 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 • Andy. Mark 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;

Nimble: Specifications � two Andy. Mark Neve. Rest 40 motors � two 4 in Tetrix wheels � two 3 in 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. . .

Basic: Specifications � Four Andy. Mark Neve. Rest 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: Specifications � four Andy. Mark Neve. Rest motors � four 4 in 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 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.

Robust: Specifications � four Andy. Mark Neve. Rest 40 motors � ten 3 in Tetrix wheels � four tooth gears � six tooth gears � four sets of. 25 Tetrix chain � twelve Tetrix sprockets

Robust: PTC Creo Design

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

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 Andy. Mark and the remaining two are Andy. Mark 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. . .

Whirlwind: Specifications � four Andy. Mark Neve. Rest 40 motors � two Andy. Mark high performance wheels � four Andy. Mark 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 Data Wedgetop Tread:

Whirlwind: Side Drag Test Data Wedgetop Tread:

Whirlwind: Spin Test Data Wedgetop Tread:

Whirlwind: Straight Line Speed Data Performance Tread:

Whirlwind: Pull Test Data Performance Tread:

Whirlwind: Side Drag Test Data Performance 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

Tracks: Specifications � four Andy. Mark Neve. Rest 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;

Direction: Specifications � four Andy. Mark motors � four 3 in 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/FTC 3486 Email: twa 3486@gmail. com Twitter: @technowarriors