Design Concepts
History of Design Contests
What we are doing isn’t really new. There are lots of design contests.
Robot contests are relatively new
Robot Contests
Woodie Flowers — Father of Competitive Robotics
In his MIT Course 2.70, he developed a way to inspire students to work extremely hard, use engineering principles, compete like crazy, and work together with even their opponents.
Short
Long but really good
Robot Contests
FIRST Robotics Competition
The varsity level of high school robotics.
Building a quality robot and having a good season is hard. It's supposed to be hard. That’s the challenge. You have to put in the work to get the reward at the end.
It’s not just a robot
Our goal on the team isn’t just the robot. The robot is important but what’s more important is that we strive to be a good team.
That means
Things you should learn
Most of what you learn on this team isn’t going to come from anyone standing at a whiteboard teaching you. It’s going to come from you putting in the time to learn it.
So what are we doing?
We are designing an entire program, not just a team. That means every year, every month, and every day. We should always be trying to make our program better.
What can you do today to make our team better?
Improving as a team requires everyone’s effort, which can be shown by designing a new feature for a robot, tagging photos, cleaning the lab, taking photos, creating a team handbook, etc.
Be passionate about making your team better!
Design is a Passionate Process
"Enthusiasm is one of the most powerful engines of success. When you do a thing, do it with all your might. Put your whole soul into it. Stamp it with your own personality. Be active, be energetic, be enthusiastic and faithful and you will accomplish your object. Nothing great was ever achieved without enthusiasm."
-Ralph Waldo Emerson
Speak UP!!!
Focus
Maximize aquatic avian linearity
Maximize avian termination with a minimum number of projectiles:
Lacerate bovine growth by-product:
Minimize deceased equine flagellation:
Impactus maximus ad gluteus maximus
Design of Prose - George Orwell
Deterministic Design
Deterministic Design: Play!
Value of failure
Reverse Engineering
Try to understand how the game designers designed the game.
This is crucial; ask lots of question about the game design.
Disruptive Technologies
Best Engineering Practices
“Random Results are the Result of Random Procedures”
Prevent problems before they occur
Schedules
Risk Management
Engineering Design Process
What do we have?
1. Evaluate your resources
What are we trying to do?
2. Study the problem
Analyze the scoring
2. Study the problem
Create Possible Strategies
3. Create possible Strategies
Create Possible Strategies
3. Create possible Strategies
Time Analysis
3. Create possible Strategies
Trade - offs
3. Create possible Strategies
Cost Benefit Analysis
3. Create possible Strategies
Scoring Analysis
The MOST critical thing you can do in a robot design contest is study the scoring algorithm and determine which are the most sensitive parameters!
In 2017 - Climbing and Gear Cycle times
In 2016 - Defense Crossings and then high goal cycle times
In 2014 - 3 Assist cycle times were critical
In Ultimate Ascent - ????
3. Create possible Strategies
Karthik’s Golden Rules
3. Create possible Strategies
Strategy Comparison Tables
3. Create possible Strategies
Strategy Comparison Tables - 2013 Example
3. Create possible Strategies
Design in Multiple Steps
Strategies -> Concepts -> Module -> Components
The design process is done of each of these steps. Sometimes you may have to go back up a step because a lower function reveals a flaw or is not obtainable with your resource or requirements.
Coarse-to-Fine
Planning a robot is like planning a party
Make broad decisions that enable you to plan the next level of detail. Sometimes you’ll have to make estimates before you know all the details and you will have to make adjustments as you go.
Coarse-to-Fine
1 2 3 4 5 6
4
1 2 3 4 5 6
1
1 2 3 4
2
1 2 3 4 5
4
Strategy
Concepts
1 2 3 4 5
1
1 2 3 4 5 6
3
Modules
1 2 3 4 5 6
5
Component
FRDPARRC Chart
Functional Requirements (FR)
Things the design must do
Examples
Design Parameters (DP)
Analysis
References
Risk
Countermeasures
Sample Chart
Sample Charts
You can always evolve your strategy
3. Create possible Strategies
FUNdamental Principles
Occam’s Razor
Occam’s Razor
Simple Machines
Ramp and Wedges
Screw
Screw
Lever
Lever
Ratio of the Lever Arms (distance the forces are from the pivot) is how we determine our mechanical advantage.
Force Lever Arm x Force >= Load
Load Lever Arm
Critical in designing pneumatic actuations
Wheel and Axle
Gear Ratios are Levers / Wheels and Axles
Big Input gear, reduces force but increases distance
Small input gear, increases force but reduces distance
Pulley
With just a single pulley you are just redirecting force. 2 pulleys as shown to the right allow you to use ½ the force over 2x the distance to lift an object.
Newton’s Laws
Basics of Mechanics - lots of our problems can come down to Newton’s laws
Newton’s 1st Law
“Every body persists in its state of rest or of uniform motion in a straight line unless it is compelled to change that state by forces imposed on it.”
An object in motion tends to stay in motion.
Newton’s 2nd Law
“The acceleration of a body is directly proportional to the resultant force acting on it and parallel in direction to this force and that the acceleration, for a given force, is inversely proportional to the mass of the body.”
Force = Mass x Acceleration
Rotational Force = Moment of Inertia x Angular Acceleration
Newton’s 3rd Law
“To every action there is always opposed an equal reaction or, the mutual actions of two bodies upon each other are always equal and directed to contrary parts.”
Conservation of linear and angular momentum
Golden Rectangle
Motors vs. Pneumatics
Motors vs. Pneumatics
Motors vs. Pneumatics
CIM Motor
miniCIM Motor
775pro Motor
BAG Motor
Motors vs. Pneumatics
Falcon 500 Motor
NEO motor
NEO 550 Motor
Motors vs. Pneumatics
v2
v1
VP Encoder
Motors vs. Pneumatics
Motors vs. Pneumatics
Motors vs. Pneumatics
Spring Return Cylinders (Single Acting)
Double Acting Cylinders
Motors vs. Pneumatics
remains the same
Abbe’s Principle
“If errors in parallax are to be avoided, then the measuring system must be placed coaxially with the axis along which the displacement is to be measured on the workpiece.”
Small errors in angle are amplified as you get far away from the origin.
It was discovered when working on manufacturing better microscopes.
Abbe’s Principle
The implications of this observation on the design of instruments and machines are profound:
Abbe’s Principle
Abbe’s Principle
Abstractions can be taken to other systems as well.
Saint-Venant’s Principle
What’s a characteristic dimension?
Saint-Venant’s Principle
Saint-Venant’s Principle - Applications
Saint-Venant’s Principle - Applications
Self-Principles
Self principles utilize the phenomena the machine is trying to control to help control the phenomena.
A design that uses the inputs to assist in achieving the desired output
4 basic types of self principles:
Examples of Self-Help
Accuracy, Repeatability, and Resolution
Accuracy: the ability to tell the truth
Repeatability: the ability to tell the same story each time
Resolution: the detail to which you tell a story
Accuracy, Repeatability, and Resolution
Sensitive Directions
Triangulate for Stiffness
Centers of Action
Center of Gravity
Center of Gravity
Bumpers are your friend
Acquisition Zone
“Touch it, Own it!” should be your goal
Continuous intake > Single Intake
Sensors
Simple Sensors
Simple Sensors
Simple Sensors
Proximity Sensors
Reflective / IR / Light Sensors
Encoders
Give you rotational speed or displacement (how many times has it turned)
Chinese LPA3806 Encoders
VersaPlanetary Encoders
Modified VersaPlanetary Encoders with 3D printed gear
for hex shaft
REV hex bore encoder
Encoders
Gyros / IMUs
Pigeon IMU connects to Talon SRX
Nav-X connects to RoboRIO MXP port
FIRST Choice Analog Devices Gryo
Fuses vs. Breakers
What is a fuse: https://www.youtube.com/watch?v=2MWwwrOQOUc
How the main breaker works - https://www.youtube.com/watch?v=KNWFCxhootY
Bolt Types
Nut Types
Taps and Dies
Rivets
Manage Friction
You will have friction in any mechanism design. What is Friction?
Gravity
Pushing Force
Friction Force resists motion
Manage Friction
Manage Friction
Rolling Friction in Linear Motion
Use our two different red toolboxes to feel the difference
Ball Bearings
out
Plain Bearings (aka bushings)
Over Constraining
Exactly Constraining
Exactly Constraining
Exactly Constraining
Exactly Constraining
Exactly Constraining
Examples
Constraint Design Notes
Elastic Averaging
Torque Transfer
Hex Broach
Hex vs Thunderhex
Hex vs Thunderhex
Spacing and securing shafts
Spacing and securing shafts
Triple-Helix Gear linkage - CAD Sketches
Triple-Helix Gear linkage
How would we modify this?
Avoid Bending Stresses
This is why the hole in Thunderhex shaft doesn’t weaken it much.
Load Paths or Structural Loops
Load Paths or Structural Loops
without inadvertently steering the bike.
Preload (why structural bolts should be tight)
Preload (why structural bolts should be tight)
The clamping force between the plate and bracket is reduced by 1
With no load applied the clamp force is 2 units, with the load applied this decreases to 1 unit of force. The bolt would not actually 'feel' any of the applied force until it exceeded the bolts clamp force.
Spacers vs standoffs
Spacers vs standoffs (Intro to FEA)
Live Axle vs Dead Axle
Live Axle vs Dead Axle
Shoulder Bolts and Bearings
⅜” Shoulder Bolt + ⅜” Bearing + Hubs/Shaft with 5/16-18 tapped holes
⅜” Shoulder Bolt + ⅜” Bearing + Hubs/Shaft with 5/16-18 tapped holes
Power Transmission: It’s all just ratios
Sprockets/Pulleys/Gears are all just levers. We will use the word gear for a bit but know it applies to sprockets and pulleys too.
If they are same size they just transfer power at the same speed and torque. This is called 1:1 (1 to 1) gearing.
If the powered gear is smaller you increase torque but decrease speed. This is called “gearing down” or the motor is “geared down to” some RPM.
If the powered gear is larger you decrease torque but increase speed.
This is called “gearing up” or the motor is “geared up to” some RPM.
Gearing Problems
If the red gear is driven by the motor, How fast will the green gear turn in relation to the motor?
1
2
Motor
Gearing Problems
If the red gear is driven by the motor, How fast will the green gear turn in relation to the motor?
It’s 2:1 (2 to 1) because it’s stated that the motor has to spin 2 times for each time the output spins once. It’s a 2:1 reduction.
2:1
1
2
Gearing Problems
If the red gear is driven by the motor, How fast will the green gear turn in relation to the motor?
If the motor is spinning at 5,000 RPM (Rotations per Minute) how fast is the green gear turning?
2:1
1
2
Gearing Problems
If the red gear is driven by the motor, How fast will the green gear turn in relation to the motor?
If the motor is spinning at 5,000 RPM (Rotations per Minute) how fast is the green gear turning? 2,500RPM
2:1
1
2
Gearing Problems
If the red gear is driven by the motor, How fast will the green gear turn in relation to the motor?
3
2
Gearing Problems
If the red gear is driven by the motor, How fast will the green gear turn in relation to the motor?
Motor is spinning at 1000 RPM.
How fast is the green gear spinning?
1.5:1
3:2
3
2
Gearing Problems
If the red gear is driven by the motor, How fast will the green gear turn in relation to the motor?
Motor is spinning at 1000 RPM.
How fast is the green gear spinning? 1500RPM
3
2
Compound Gears
If you gear multiple times you just multiply the ratios. What’s the ratio?
1
1
2
2
Compound Gears
2:1 x 2:1 = 4:1
If the motor is spinning at 2,000 RPM (Rotations per Minute) how fast is the green gear turning?
If you gear multiple times you just multiply the ratios. What’s the ratio?
1
1
2
2
Compound Gears
2:1 x 2:1 = 4:1
If the motor is spinning at 2,000 RPM (Rotations per Minute) how fast is the green gear turning? 2000 / 4 = 500RPM
If you gear multiple times you just multiply the ratios. What’s the ratio?
1
1
2
2
Gussets and Tubing Construction
on VEX website
for examples on
how to use these
VersaFrame Examples
Build Blitz JVN Robot - https://www.youtube.com/watch?v=Gm96S8gdhR0��
VersaFrame Examples
CAD Walkthrough
Adjustable Prototypes
118 Test Catapult 2016
Adjustable Prototypes
2848 Designed Test Jig from 2016
Power Transmission
Pitch - Roughly the size of the tooth in the power transmission system. There are multiple ways to measure pitch and they are different for gears, sprockets, & pulleys. Don’t mix match pitch.
In FRC we basically have a big and small version of each of these. Make sure the teeth on your pulleys/gears/sprockets all are the same size.
Timing Belts and Pulleys
with a pressed on pinion pulley
to get the number of teeth.
(500mm long, 5mm pitch belt is 100 teeth)
Timing Belts and Pulleys
Timing Belts and Pulleys
Timing Belts and Pulleys
5mm Pitch HTD (bigger teeth)
3mm Pitch GT2 / HTD (smaller teeth)
work but they will be less efficient.
Timing Belts and Pulleys
Calculating Belt Distances
Chain and Sprockets
Chain and Sprockets
#25 Chain - 0.25" Pitch (smaller teeth)
#35 Chain - 0.375” Pitch (bigger teeth)
Chain and Sprockets
Working with chain
Chain and Sprockets
Master Links
Half Links
Chain and Sprockets
Calculating Chain Distances
Designing with Chain
Chain and Sprockets
Mounting to chain
Attache to the chain as well.
Gears
Gears
all gears sold by FIRST suppliers they are the same for a given
DP.
Gears
20 DP (bigger teeth)
32 DP (smaller teeth)
Gears
Calculating Gear Distances
Quiz
Planetary Gears
How planetary gears work - https://youtu.be/ARd-Om2VyiE
The VersaPlanetary is our standard planetary gearbox. It can be customized by interchanging and stacking gear sets.
VP User Guide - Read this if you are using VPs
VP Customization Options
VP Videos
VEXpro VersaKey system
Lubrication
Lubrication - using a substance to reduce the friction between two surfaces.
VP lubricant - TRI-Flow, just a few drops on each gear.
Chain Lubricant - TRI-Flow, just a few drops on the sprockets
Gearbox Lubrication - blueWorks spray in as you rotate the gearbox, try to coat all the teeth.
CADing Shafts
973 Adam Heard Method - https://youtu.be/e2TK3_XMcdU?t=725
Springs
Variable Force
Constant Force
Springs - Counterbalances
Elastic bands
Constant force springs
Springs
118 clutched roller with springs
Pneumatic to Rotary Motion
Star Nuts
Mounting tubes to plates.
You insert the nut and then the bolt expands the fins into the side of the tube stopping it from coming out.
Spring Loaded Rollers
Compliant roller mount
Lead Screws
3D Printing
SLA - https://www.youtube.com/watch?v=NM55ct5KwiI
SLS - https://www.youtube.com/watch?v=9E5MfBAV_tA
FDM (what we use, most desktop printers) - https://www.youtube.com/watch?v=WHO6G67GJbM
3D Printing
Filament - the material used for printing. Different plastics in thin strands that can be melted and deposited on to the build plate.
3D Printing
Supports - material that you break away since you can’t print in thin air.
Designing for 3D printing