Duke Combat Robotics

Spring 2025

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Tyler Bletsch

Duke University

https://sites.duke.edu/combatrobots/

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Exec

• Cody Andres Alessio-Bunnell, President

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• Ava Jarell, Vice President

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• Shaan Narayan, Treasurer

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• Cody Andres Alessio-Bunnell, Safety Officer

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• Zachary Maldonado, Outreach and Competition Planning

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• Will Neuner, Student Advisor

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• Tyler Bletsch, Faculty Advisor

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Objectives

• Learn mechanical and electrical fundamentals
• Develop skills to complement understanding of theory
• Enhance skill at decomposing problems among a group
• Emphasize role of prototyping to practical engineering
• Provide a design experience in a difficult, open problem with no one right answer
• There’s always a bigger fish
• Most Importantly: Have FUN!!!

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General Structure

Teams

• Focus on creating 1 lb “antweight robots”
• Divide club into sub teams of 2-4
• Each create their own bot
• Make your own or we will have a team creation form sent after this meeting
• Each team is assigned an Exec advisor to help

Meeting Structure

• Monthly GBM’s (Sundays)
• Slight food provided
• “Show and Tell” for teams to present updates on robots
• Largely Social
• Biweekly Build Tutorials
• Lessons on subset robotics fundamentals taught by exec of Dr. Bletsch
• Designed for newcomers
• Teams then have the next two weeks to implement lessons before next tutorial
• Weekly Office Hours
• Exec and Dr. Bletsch will host Office Hours in Foundry throughout the weeks

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General Structure

Goal: End of Semester Competition

• A weekend before finals (date not finalized)
• Have a tournament style competition
• This year we plan to host an NC State vs Duke Robot Bash (Name still in development)

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First Semester Timeline

Timeline:

• January: learn fundamentals of each piece, prototype possibilities
• Optimized metric: things learned per second (theory and practice)
• February: Build *ASAP* (don’t dawdle!), get testing
• Optimized metric: robots destroyed per second, lessons learned
• March: Skirmishes between teams ending
• Optimized metric: battles per second, robot changes applied
• April: Polish/iteration, internal competition
• They fight

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Other Fun Things

• Regional Off-campus league events
• Day trips to competitions in NC or surrounding states
• Travel costs covered by Duke
• About 1
• Sign up dates will be earlier in semester, so build bot accordingly if want to go
• Exec will provide updates when competitions open
• Social Events
• 1-2 per semester
• Build community
• Ex: Movie Night, wii night, etc.
• We’re starting to design a beetleweight (3 lb) robot to represent Duke

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• New arena!

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The Beetleweight Team

• New initiative this semester
• Teams will be composed of 6-8 people and led by members of exec
• Current plan: team veterans can declare interest to join the team and teams will be formed
• newbies can join but it is HIGHLY recommended to first successfully complete a combat robot and compete one semester before joining

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• If you have past combat robot experience and are interested, speak up on Discord in #beetleweight

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General vibe

• Don’t be afraid to ask questions!
• There is no assumed pre-requisite knowledge!
• Weekly Roundups and large announcements are sent via email from Duke Groups
• Discord is a social space!
• Discuss stuff with the broader group (#battlebot-general), ask questions, etc.
• some in-the-moment smaller announcements will be made here
• Use the wiki: https://combatrobotics.wiki.duke.edu/
• New this year; lots of technical info
• Anyone who wants to edit it, just ask me to add you
• Veterans: Help out the rookies

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Rules

• SPARC rules
• http://sparc.tools/
• Weight class: antweight – max 1lb (454 g)

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• What about plastic antweight?
• A separate weight class for fully 3D printed robots (PLA/PETG only).
• Not necessary for us, but some external events have a �“plastic antweight” class.

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To-Dos

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Join DukeGroups!

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Get on the Discord!

• Join in a way where you see @ notifications �(not in a throwaway browser session)
• Set your name on here to your full real name (first+last)

DISCORD INVITE

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Brief Intro to Common antweight �combat robot components

(Bletsch)

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Battery

• Lithium polymer batteries (LiPo)
• High energy density
• Can source a lot of current
• Explode and catch fire if mistreated!

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LiPo concepts

• “S”: Batteries have a number of cells in series, �which sets the nominal voltage. �These are labeled “1S” (3.7V), “2S” (7.4V), “3S” (11.1V), etc.
• We use 2S batteries.
• LiPo bag: A fireproof bag used to store and charge LiPos
• Charging: LiPos get their white JST-XH port plugged into a balance charger. All lights green = done.
• If a light NEVER turns green, battery is cursed, must be banished (see next)
• Charged? Move to “charged” bag.
• Needs charge but all chargers busy? Leave in charger bag.

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Charge�JST-XH port

Run�XT30 port

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Brushed motors and brushed ESCs

• Brushed DC motors
• Fairly fast
• Often paired with an onboard gearbox to get higher torque at lower speed
• Two-wire interface: more volts = faster
• Governed by a motor controller also known as a brushed Electronic Speed Controller (ESC)

Battery in

2x signal in

2x motor out

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BLDC motors and ESCs

• Brush-Less DC (BLDC) motors
• Three wire interface – power is three sine waves of voltage
• Fast and cheap – common in drones
• Governed by Electronic Speed Controller (ESC)

Battery in

Signal in

Motor out

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Radio receiver

• Runs on 5V, but battery is ~7V – what to do?
• Need to regulate battery voltage down to 5V
• Could be a separate thing, but most ESCs have a regulator built in – they feed 5V out. This is (dumbly) called the battery eliminator circuit.

Signals out (Pulse Width Modulation, PWM)

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Kinds of weapons

• Passive: Shape/geometry + drivetrain is the weapon, e.g. a wedge

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• Kinetic: Constant rotation holds lots of kinetic�energy, whacks opponent when it connects�E.g., drum spinners, horizonal spinners, vertical spinners

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• Sudden acceleration: Weapon is actuated from a stop to high speed, e.g. a hammer or flipper

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Electrical skeleton of one potential robot

~9V

5V

A voltage regulator in here converts ~9V to 5V to power radio. This is also called a Battery Eliminator Circuit (BEC) by drone people.

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Power wiring diagram

• Same as last slide, just showing power connections only, labeling connector types

Wire harness (you build this)

To Radio

To motor 1

To motor 2

To BLDC �motor

To Radio

Battery

XT30

female

XT30

male

XT30

female

JST

female

JST

male

XT30

male

Switch

Brushed �dual ESC

Brushless ESC

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Switches

We have two switches available

• Automotive switch with built in LED

+ Easiest to wire and mount (just need the right size hole)

– Sticks out of robot, easy to get hit by accident

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• Homemade “fingertech style” switch

+ Turns on and off by screwdriver and lives inside your bot (safter)

– Some assembly required, must wire and expose your own LED

(A power indicator light is required by rules)

+ input

+ output

– negative (just for LED)

Could also consider name-brand FingerTech switch, but we don’t want to pay for one for everyone (~$15/ea shipped)

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Aaand…back to exec

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Safety!

• Combat Robotic is inherently a little dangerous
• Stay vigilant on what you’re working on
• Listen to safety briefings
• Report incidents to exec
• If you don’t know what to do, don’t hesitate to reach out!
• we won’t be mad

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Example Fight

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Questions?

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Thank you

https://www.youtube.com/watch?v=1SiylvmFI_8

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