Lots to Review From Week 3

We started off last weekend making some parts on the CNC machine for our drive train. We learned a lot more abut zeroing than we bargained for as we found out the CNC machine was not fully calibrated in the Y. we will have that fixed on future parts.

Next up, we did some high speed driver testing to start to get our drivers used to 16-18 FPS.  Wow is that fast.  We have been getting our cycles down and have started looking at sight lines.

Our vision team was also hard at work.  We were able to get our hands on some reto reflective rope and found out we could create an auto centering teleop assist command to help us hit the rope with more accuracy.  But, we also learned that retro reflectve ropes are illegal so that is out.

Our chief strategists has been running field simulations to better understand how many balls we will be able to pick up and how quickly we can load up after all o the hoppers are empty.  It looks like the corners are the place to be fore picking up balls in a hurry.

And of course we have been building and prototyping.  We should have our drive train driving around today because of all of the great effort that has been put in this week.  On top of that we have a much better idea of how our gear intake and ball intakes will work.  As an added bonus. if we get the main robot fully functional by next Saturday, the tea already has plans for adding a high goal shooter.  If that is the case, shooter prototyping would be on the schedule in two weeks.  much earlier than we planned.

More videos can be found on our 2017 build season play list

 

Lots of Big Learning Today

The team came back from its three day weekend with a vengeance by making 3 gear picker uppers, a revised climber and got pneumatics working.  As a bonus, the team has found ourselves a new programming mentor and he has jumped right in by helping the kids organize their code.  Things are looking up.

As an added bonus, we have a finished airship to practice on and updated liftzilla drive train to start high speed driving with.

We have also starting trying to figure out the robot’s name for this season.

Additionally, the awards team is in full swing and we are working hard to get our awards videos done.

As if all that weren’t enough, the team is starting to plan our district event that we are hosting in march.

Swerve or Octocannum……Are we crazy???

One of this year’s requirements we have made a primary goal is: Be able to drive nearly 20ft per second and highly maneuverable.  In order to make this possible we have zeroed in on two drives that we think we can allow us to meet this goal. The first is the infamous Swerve drive and the second is the slightly less infamous and scarier Octocannum drive.  These two drives are two of the most expensive, heavy, hard to manufacture and hard to code drives trains in FRC today. Under normal conditions these drives should never be attempted unless a team has invested time over the last few years to get to know them inside and out.  But, we are gluttons for punishment and no matter what want to learn as much as we can each year, and taking one of these drives on would definitely push us to learn more this season than we are planning.  The risks are pretty strait forward, we could be heavy, we could screw up fabrication, we could screw up the wiring, we could screw up the pneumatics, we could screw up the code and last but not least, we could not get anything else working because we dump to much time into the drive train.

The only thing that could save our bacon if we go his route is that both Andymark and Vexpro have cots solutions that would eliminate most of the fabrication risks.

This is going to sound strange, but we think the swerve module from Andymark, that comes with everything but encoders would reduce enough risk to make this a viable option for a team that has only done drop 6 drive trains before.  That is a totally loaded statement, but hear us out.  The Andymark swerve only needs electricity and has all of the motors and chains we would need to just strap this on our machine.  We would still need to buy all of the encoders and encoder mounting hardware, but for all intents and purposes this module is ready for wiring and code pretty quickly.  On the other side, the Vexpro swerve needs some engineering to make work and the Octocannum needs electrical, pneumatics and some engineering. The major downside of the Andymark Swerve is that it is slow.  11.5fps is about half the speed we are looking for.

We are going to do a full trade study on these three options today and will publish the results tomorrow.

On other topics, the team was hard at work making prototypes and started their robot in 5 days.  We will have pics and videos up tomorrow.

 

Robotics Day at the Kid Museum

Walt Whitman will join 3 other FRC teams from the area and help the local Kid’s Museum host their first Robotics Day. Stop by with your kids, your neighbors kids and your inner kid to check us out. We will have several team members on hand as well as our World Championship  Level robot Maelstrom available for you to drive.

Saturday, July 16

From the nuts & bolts of how robots move, to testing out competition robots…it’s everything robots at KID’s first ever Robotics Day!

Open Explore
Stop in throughout the day to experiment with gears, parts and pulleys; take part in “Imagining the Robots of the Future;” and learn about different machines and systems, like VEX, LittleBits, and Arduino.

Featured Workshops
LEGO WeDo: Move and manipulate objects with this robotics tool. Design your own interactive machine using gears, motors, motion sensors, and more. Ages 8+. $6 members; $7 nonmembers. 11:00 REGISTER

MakerWear: Customize clothing with lights and sounds that react to your movements, and be a part of the University of Maryland’s Human-Computer Interaction Lab MakerWear prototyping project. Ages 6+. $3 members; $4 nonmembers. 1:30 REGISTER

Demos
See amazing demos by local high school FRC robotics teams:

Team 1389 
Walt Whitman High School
Bethesda, MD

Team 449
Blair High School
Silver Spring, MD

We have a plan

Tonight we met to go over our performance last weekend. Lots of great insights into where the team did well and where we can improve.  We also went through the schedule for the next week and identified our priority list of things to do.

20160316_181122 20160316_181117 20160316_181116

Here is what we need to get done

  • Vision code – pushed to after second event
  • Main code part 2 – started
  • Strategy part 2 – not started
  • Scouting system part 2 – not started
  • Communication system part 2 – not started
  • Competition documents part 2 – not started
    • Tech Journal part 2 – not started
    • Judges Packet part 2 – not started
    • 1 sheeter part 2 – not started
    • Pit Video part 2 – not started
    • Chairman’s presentation part 2 – not started
    • Bill of Materials part 2- not started
  • Pre-competition scouting part 2 – started
  • Pre season scouting and risk survey part 2 – started
  • Climber pushed to after second event
  • Defensive Cheescake – not started
  • Refurbish robot cart not started (lost new cart at competition, need to start again)
  • Paint Pit – pushed to after second event
  • Upgraded alpha turret and arm – not started
  • Fix bumpers – started
  • Add camera mounts and two cameras – started
  • Identify parts we need to order – Complete
  • Organize pit – not started
  • Score in auton code – started
  • integrate NavX – started

20160316_181106

 

Mechanical Systems

Two major systems of every robot on the planet are the structural systems and mechanical systems. Mechanical systems allow some or all of the robot to move. Before we get into how to design a mechanical system we are going to go through all of the things FRC, FTC and Vex robots have been asked to do over the years.

Tasks in FRC

 

Tasks Unique to FTC or Vex

When you are doing research look up the past games to get an idea of what the various types of tasks were and what the game pieces looked like. Next we will go through some of the popular mechanical systems that teams have used to do all of the above tasks.

 

Mechanisms Examples

 

Passive vs Active Mechanical Systems

You can design a mechanism to be completely active, meaning that all functionality is a result of powered motion as demonstrated above. Or you can design a mechanism to be partially or completely passive meaning all functionality is a result of the shape. The benefits of passive mechanism are that the reduce the likelihood of mechanical or human failure occurring. Here are some examples of passive mechanisms;

  • Intake mechanisms
    • Passive claw: tote
  • Robot lifter mechanism: example 1

 

Understanding Motion

Once you have selected the desired capability you will need to select the type of motion you need. Here are the different types of motion you are most likely to see in FRC;

  • Linear motion – motion in a straight line (example: train on a track)
    linear_motion
  • Rotary motion – circular motion (example: the hands of a clock moving, or a wheel on an axle)
    engineanimation

 

Mechanical Joints

A mechanical joint is a section of a machine which is used to connect one mechanical part to another. Mechanical joints may be temporary or permanent, most types are designed to be disassembled.

 

Mechanical System Design

Mechanical Systems need to be able to withstand the expected structural loads over an expected number of cycles. Teams will need to follow these steps necessary to design their mechanical system.

  1. Sketch out a idea
  2. Build prototypes
  3. Refine the sketch
  4. Refine the prototype
  5. Create a free body diagram
  6. Understand the loads
    1. Understand ultimate load case for each type of loading
    2. Understand the number of cycles for each load case
    3. Do the math
  7. Select materials that can resist the loads
  8. Define the shape that will resist fatigue and is manufacturable

Note – steps 3 and 4 may need to be repeated many times to find the right combination to reduce weight and fabrication complexity

 

Additional Information

Pre-Selecting an FRC Drive Base

Last year the team took a tip from some veteran teams and pre-selected our drive train.  That means prior to the season we selected what drive train we would use so that we could spend the entire season focused on what we would put on top of the drive train.  Last year we selected a drop center 6 wheel west coast drive with a single speed gear box.  However, after the season started, we decided to switch to the Andymark 2015 kit bot as our base, and instead used all of the parts we had purchased for the west coast drive on our lifting mechanism.  It worked out really well since we had pre-ordered nearly all of the parts for the lifter and the kit bot was handed to us on day one. The team was able to finish a week early and drove for nearly 5 days before bag and tag.

The team did make some modification to the Andymark drive train that we feel made the drive more useful for last years game . And there in lies the beauty of using one of these two standard drive trains, they can be quickly modified because they are designed to flexible.

  • We turned the drive base from a rectangle to a U
  • We swapped out traction wheels on the front and the middle of the U for omni wheels

20150206_151439 20150131_142931 20150131_170320

We plan on doing the same thing this year and are taking things a step further. We have completed all of the CAD and code that will be needed for our drive system and plan on pre-ordering all of the parts next week.  We have decided to go with a drop center 6 wheel west coast drive with a single speed gear box for the second year in a row.  We are also adding bumper mounts to this years design in expectation of the noodles coming back.  We like the west coast drive solution because it can be easily modified to meet what ever size chassis we may need once we find out the game.  All we have to do is cut the 1″ x 2″ to fit, and then the rest of the fabrication and assembly can happen in a matter of days. This should give our drive team plenty of time to practice with the drive as we complete the rest of the robot.

pre-order pre-order 2 pre-order 3

We still have some work to do on the CAD, here are the list of the changes we are making;

  • Move pulleys inside the frame
  • Add mounts for bumpers and model bumpers according to the 2014 rules
  • Add belts
  • Move the outer wheels closer to the cross members
  • Create a rear gear box configuration
  • Change the some of the permanent fasteners on the T brackets to 10-32 bolts to increase repair ability

 

We are also planning on doing as much as we can out of versa frame since our fabrication capabilities are still growing. In order to meet the goals of finishing the robot at the beginning of week 5 we are going to need to get a jump on our fabrication.  So we figured we would take our pre order a step further and get a lot of the materials we plan on using now, before the season starts so that we can go right from prototyping to fabrication.  Here is a list of everything we plan on pre-ordering;

 

item quantity type price link sub total
hydrolic press 1 tool $       200 http://www.harborfreight.com/20-ton-shop-press-32879.html?ccdenc=eyJjb2RlIjoiNTQyMDQxODciLCJza3UiOiIzMjg3OSIsImlzIjoiMTU0Ljk5IiwicHJvZHVjdF9p%0D%0AZCI6IjQ1MyJ9%0D%0A&utm_medium=email&utm_campaign=4015b&utm_source=1022&cid=mEmail_s1022_c4015b&utm_referrer=direct%2Fnot%20provided&utm_referrer=direct%2Fnot%20provided $         200
Rivet tool head 2 tool $           3 http://www.mcmaster.com/#6659A244 $             6
Riveter 2 tool $         30 http://www.mcmaster.com/#6659A21 $           60
Drill Bits 2 tool $       132 http://www.mcmaster.com/#3186A41 $         263
1/2 hex broach 1 tool $       230 http://www.mcmaster.com/#2875A24 $         230
3/8 hex broach 1 tool $       156 http://www.mcmaster.com/#2875A19 $         156
Tube cutter 4 tool $           8 http://www.amazon.com/Coilhose-Pneumatics-PXC058-BAG-Tubing-Cutter/dp/B00CD8HB1I/ref=sr_1_2?s=power-hand-tools&ie=UTF8&qid=1447593275&sr=1-2&keywords=tubing+cutter&pebp=1447593281040&perid=0ENRN49FG9N1QSY9GM5S $           33
chain breaker 1 tool $         30 http://www.mcmaster.com/#6051K15 $           30
replacement pin 2 tool $           3 http://www.mcmaster.com/#6051K22 $             5
right angle drill 1 tool $       120 http://www.amazon.com/DEWALT-DCD740B-20-Volt-Li-Ion-Right/dp/B007ML7DHS/ref=sr_1_3?s=power-hand-tools&ie=UTF8&qid=1447593504&sr=1-3&keywords=right+angle+drill&pebp=1447593608832&perid=147VE82S41CHTHCHXC3Y $         120
VersaFrame 1″ x 1″ x 0.040″ Pre-Drilled Tube Stock (59″ length) 4 material $         15 http://www.vexrobotics.com/vexpro/versaframe/versaframestock.html $           60
VersaFrame 1″ x 1″ x 0.100″ Pre-Drilled Tube Stock (59″ length) 4 material $         20 http://www.vexrobotics.com/vexpro/versaframe/versaframestock.html $           80
VersaFrame 1″ x 2″ x 0.10″ Pre-Drilled Tube Stock (59″ length) 4 material $         25 http://www.vexrobotics.com/vexpro/versaframe/versaframestock.html $         100
VersaFrame 1″ x 1″ x 0.090″ Angle (59″ length) 2 material $         15 http://www.vexrobotics.com/vexpro/versaframe/versaframestock.html $           30
VersaFrame Corner Gusset 10 material $           8 http://www.vexrobotics.com/vexpro/versaframe/versaframegussetsandmounts.html $           80
VersaFrame 1″ Wide VersaPlanetary Parallel Mount 2 material $         10 http://www.vexrobotics.com/vexpro/versaframe/versaframegussetsandmounts.html $           20
VersaFrame 2″ Wide VersaPlanetary Parallel Mount 2 material $         10 http://www.vexrobotics.com/vexpro/versaframe/versaframegussetsandmounts.html $           20
VersaFrame 30 Degree Gusset (2-pack) 2 material $           5 http://www.vexrobotics.com/vexpro/versaframe/versaframegussetsandmounts.html $           10
VersaFrame 45 Degree Gusset (2-pack) 2 material $           5 http://www.vexrobotics.com/vexpro/versaframe/versaframegussetsandmounts.html $           10
VersaFrame 60 Degree Gusset (2-pack) 2 material $           5 http://www.vexrobotics.com/vexpro/versaframe/versaframegussetsandmounts.html $           10
VersaFrame 90 Degree Gusset (2-pack) 10 material $           5 http://www.vexrobotics.com/vexpro/versaframe/versaframegussetsandmounts.html $           50
VersaFrame 120 Degree Gusset (2-pack) 2 material $           5 http://www.vexrobotics.com/vexpro/versaframe/versaframegussetsandmounts.html $           10
VersaFrame 135 Degree Gusset (2-pack) 2 material $           5 http://www.vexrobotics.com/vexpro/versaframe/versaframegussetsandmounts.html $           10
VersaFrame 150 Degree Gusset (2-pack) 2 material $           5 http://www.vexrobotics.com/vexpro/versaframe/versaframegussetsandmounts.html $           10
VersaFrame Plus Gusset (2-pack) 2 material $           5 http://www.vexrobotics.com/vexpro/versaframe/versaframegussetsandmounts.html $           10
VersaFrame End Bearing Mount (2-pack) 4 material $           5 http://www.vexrobotics.com/vexpro/versaframe/versaframegussetsandmounts.html $           20
VersaFrame Face Bearing Mount (2-pack) 4 material $           5 http://www.vexrobotics.com/vexpro/versaframe/versaframegussetsandmounts.html $           20
VersaFrame Side Bearing Mount (2-pack) 4 material $           5 http://www.vexrobotics.com/vexpro/versaframe/versaframegussetsandmounts.html $           20
VersaFrame T Gusset (2-pack) 4 material $           5 http://www.vexrobotics.com/vexpro/versaframe/versaframegussetsandmounts.html $           20
VersaFrame VersaPlanetary Face Mount (2-pack) 4 material $           5 http://www.vexrobotics.com/vexpro/versaframe/versaframegussetsandmounts.html $           20
VersaFrame VersaPlanetary Side Mount 4 material $         10 http://www.vexrobotics.com/vexpro/versaframe/versaframegussetsandmounts.html $           40
VersaFrame Linear Motion Gusset Kit 4 material $           8 http://www.vexrobotics.com/vexpro/versaframe/versaframegussetsandmounts.html $           32
VersaFrame Roller Chain Mount (2-pack) 2 material $           3 http://www.vexrobotics.com/vexpro/versaframe/versaframegussetsandmounts.html $             6
Single Reduction Clamping Gearbox 6 gear box $         10 http://www.vexrobotics.com/vexpro/motion/gearboxes/217-4156.html $           60
VersaBlock Kit 6 gear box $         25 http://www.vexrobotics.com/vexpro/all/versachassis.html $         150
WCP Cam 4 gear box $           5 http://www.vexrobotics.com/vexpro/all/versachassis.html $           20
1/2 hex bearings 20 gear box $           6 http://www.andymark.com/Bearings-s/www.andymark.com/product-p/am-2986.htm $         120
Pneumatic Control Module 1 electrical $         90 http://www.vexrobotics.com/vexpro/motors-electronics/217-4243.html $           90
Mad Catz V.1 Joystick (am-2825) 2 electrical $         34 http://www.andymark.com/Joystick-p/am-2825.htm $           68
Dual Band Radio, OM5P-AN Access Point (am-3277) 1 electrical $       135 http://www.andymark.com/OM5P-AN-p/am-3277.htm $         135
Batteries 1 electrical $         89 http://www.andymark.com/battery-p/am-3062.htm $           89
PWM cables 1 electrical $         83 http://www.andymark.com/product-p/am-2218.htm $           83
Connectors 6 electrical $         14 http://www.andymark.com/product-p/am-2198.htm $           84
Motor Controllers 59.99 electrical $         14 http://www.vexrobotics.com/vexpro/motors-electronics/217-9090.html $         840
Valve, Double Solenoid, 12V Festo VUVG (am-0888) 4 pneumatic $       116 http://www.andymark.com/product-p/am-0888.htm $         462

Design Process

The design process is an iterative approach to organizing people, ideas and work with the goal of creating something. Variations of this process have been used all over the world to create every single thing that nature has not provided. If you plan on creating ideas, things, code or solutions. We recommend you commit this process to memory so that as you encounter challenges you have the tools at your disposal to work with others on ways to overcome those challenges.

Their are millions of ways to solve every problem and millions of ways to find every solution. The process we are about to go through is optimized for high school robotics, and is just one of those millions of way to find a solution.

FRC Design Process

Since FRC build seasons last 6 weeks here is how we recommend you spend the first 2 weeks.

FRC Design schedule

Now lets go through the detailed steps of the deign process

  1. Understand
    • Prepare
      • Learn as much as you can in the off season about robots, robot design, fabrication, previous games
      • Make things
      • Make mistakes, learn from those mistakes and make more mistakes
      • Create goals for the season
        • Example – make it to elimination as a 2nd pick
        • Example – make it to elimination as a 1st pick
        • Example – make it to elimination as an alliance captian
        • Example – win a district event
        • Example – win two district events
        • Example – win a super regional
        • Example – win a CMP division
        • Example – win CMP
      • Identify the teams limitations
        • Financial
        • Fabrication capabilities
        • Assembly capabilities
        • Student knowledge
        • Mentor knowledge
    • READ THE RULES!!!!!
      • Understand how teams will be measured at competition
      • Understand how teams will advance
      • Understand limitations defined in the rules
    • Break the game down
      • Identify every way to get points
      • Identify every way to win
      • Identify the every type of robot capability needed to get every point and execute every way to win
      • Identify what percentage of teams at a district, regional, CMP division, CMP championships will be able to perform each capability
      • Identify the capabilities your team will need to accomplish its season goals that do not exceed your team’s limitations
    • Baseline your team’s strategy
  2. Brain storm & trade study
    • Document requirements
      • Pull from your team’s goals
      • Pull from the rules
      • Pull from your team’s base line strategy
    • Brainstorm
      • Identify all of the ways a team could meat all or some of the team’s requirements
    • Check ideas for feasibility
      • Reduce the list based on the team’s limitation’s
      • Reduce the list based on rules violations
    • Trade study
      • Add a weight to each requirements
        • 1 for nice to have
        • 3 for want
        • 9 for need
      • Score each feasible idea on how well it enables each requirements
        • 0 for negative or no impact
        • 1 for some impact
        • 3 for average impact
        • 9 for significant impact
      • Verify scores with prototyping and learning
      • Identify the preferred solutions for each capability
        • multiply the weight by the enabling score and sum the products for the feasible idea
  3. Prototype & learn
    • Prototype as many of your ideas as possible
      • Make prototypes fast
      • Make prototypes cheap
      • Do not make prototype perfect
      • Prototype mechanical ideas
      • Prototype code ideas
      • Prototype electrical ideas
    • Use as many other prototype data points from outside of the team as possible
      • Other FRC teams
      • Other FTC teams
      • Other FLL teams
      • Other Vex teams
      • Other robots
      • Other industries
      • 3 day build teams
    • Research how the rest of the world has solved similar problems
      • Document commercial solutions
      • Document research solutions
      • Document future solutions
    • Document lessons learned from prototype fabrication
    • Document lessons learned from making the prototype function
    • Identify what knowledge you will need to detailed design each systems
      • Identify what mathematics you will need to know
      • Identify which sensors you will need to know how to use
      • Identify chat electronics you will need to know how to use
      • Identify what mechanical systems you will need to know how to use
      • Identify what code you will need to know how to apply
  4. Concept design
    • Make “Back of the napkin” Sketches
      • Sketches on paper
      • Sketches on white boards
      • Sketches in power point
    • Create Concept CAD
      • Make 3-6 concept CAD models
    • Focus on feasibility
    • Focus on form factor
    • Start to think about parts
      • What supplier
      • How to fabricate
      • What can be ordered now
    • Identify risks
      • Technical risk
      • Lack of knowledge
    • Create baseline system diagrams
      • Identify all of the critical systems
      • Identify the control logic rules
      • Identify sensors
    • Document assumptions
    • Lock down tea strategy
  5. Detailed prototype
    • Prototype as many of your conceptual designs as possible
      • Make prototypes fast
      • Make prototypes cheap
      • Do not make prototype perfect
      • Prototype mechanical ideas
      • Prototype code ideas
      • Prototype electrical ideas
    • Focus on design convergence
      • Work through details
      • Identify key variables that make the component function
      • Look for ways to simply design
    • Interact with game pieces and field elements
      • Verify preliminary calculations
    • Reduce risks
      • Validate assumptions
      • Reduce points for mechanical failure
      • Minimize loading
    • Create pseudo code
  6. Detail Design
    • Create prototype CAD
      • Check final details against calculations
    • Host design review
    • Maximize multi use
      • Details
      • Sub assemblies
    • Maximize symmetry
    • Maximize passive systems
    • Create final systems design
    • Create detail CAD
    • Create BOM
    • Design driver station
  7. Sourcing & fabricate
    • Order all of the parts
    • Fabricate detail parts
  8. Assembling
    • Assemble sub assemblies
      • Test sub assemblies
    • Assemble minor assembles
      • Test minor assemblies
    • Assemble major assemblies
      • Test major assemblies
    • Assemble robot
    • Wire robot
    • Install electrical systems
    • Install pneumatic systems
    • Run systems test
  9. Finalizing
    • Test robot functions
    • Optimize final design
      • Modify game element interaction to be as speedy as possible
      • Modify computer vision to be as accurate as possible
      • Modify PID loops to increase efficiency
    • Test teleop code
    • Test autonomous
    • Test driver station
    • Practice driving
    • Fabricate spare parts

 

Here are some links to resources from other teams that we highly recommend you check out;

CAD & CAM

CAD or Computer Aided Design is one of the most critical things your team can do to become more successful. CAD enables your team to be more efficient and effective with the limited time and financial resources of FRC. CAD at its roots does two things; captures design intent and communicates design intent, thus the more you CAD the more you communicate. Conceptual CAD should be completed within 5 days of kickoff. Prototype CAD should be completed within 7 days of kickoff. Final CAD should be completed within 10 days of kickoff. This rigorous schedule pushes teams to do most of their thinking up front so that they leave as little of their robot design up to chance. When doing CAD teams should think about the following at the following stages;

Conceptual CAD

  • What are the goals / requirements
    • Repairability
    • Ease of assembly
    • Game functions that need to be completed by the robot
    • Game functions that we want to be completed by the robot
    • Game functions that would be nice if the robot could complete
    • Rules
  • Game pieces are modeled and interacted with
  • Field is modeled and interacted with
  • Major structural components are modeled
  • Keep modeling time to under 2 hours per concept

2015 concept1concept 2 image 3

Prototype CAD

  • What are the teams limitations
    • Time
    • Cost
    • Detail part fabrication capability of the team’s students
    • Tools available to the team for fabrication
  • What are the ranges of motion of your mechanisms
  • What are the major and minor assemblies
  • Where will the electronics go
    • Use cubes to represent
  • Where will the pneumatics go
    • Use cubes to represent
  • What is the Master axis system for the robot
  • What are the materials you know you are going to need and can order before detail design is finished

Concept 3 image 4Concept 3 image 4Concept 3 image 1

Final CAD

  • What are the Free Body Diagrams (FBD) for your robot
  • What are the parts you are going to use for every aspect of the robot
    • Who is the supplier
    • Are the parts legal and available
    • How is every part going to be fabricated or sourced
    • What are the materials
  • What is the assembly order for the robot
    • Where are the payoffs
  • What fasteners are used at every joint
  • What gears or sprockets will be used for every mechanism
  • What mechanical transfer mediums are being used
    • What are the belt sizes
    • What are the number of chain links
    • How will they be tensioned
  • Does the math of your mechanisms work with the parts selected
  • What is the weight of the robot
  • Where is the Center of Gravity (CG)
  • Where will every electronic component go
    • Is the batter easily removable
    • Where will the wires go
    • Are the status light easily view able
  • Is the drive system easily repairable
  • Are major mechanisms easily repairable
  • Where will every pneumatic components go
    • Is the full range of motion possible
    • Do you need mechanical stops
  • Do we violate any rules
  • Does it meet all of the teams need level requirements
  • All of the assemblies and detail parts are labeled

Team1389-2015_field-12 Team1389-2015_electrical-1 Team1389-2015_field-13

 

Teams have a large variety of CAD software available to them, for free through FIRST; Autodesk and Solid works are the two most popular. Please see FIRST’s CAD webpage for the details on how to download the software for free. Once you have the software you will need to learn how to use it. Check out these tutorials to learn the basics.

 

Once you know the basics you are ready to learn about how to model detail parts and simple assemblies. But FRC robots can be made out of more than 200 parts and 300 fasteners. When modeling at this scale we recommend that you learn some more of the advanced ways of thinking about CAD;

  • Model based definition
    • This is thinking in terms of models as opposed to drawings.
  • Relational Design
    • This is thinking in terms of how the final assembly, relates to major assemblies, which relate to minor assemblies and how they all relate to detail parts, multi use assemblies and multi use parts
  • Parametric design
    • This is thinking in terms of CAD efficiency
  • Be strategic and minimize what you have to model
    • This is thinking in terms of reuse and reduction of total CAD effort
      • adTown CAD Library – FRC Team 1323, MadTown Robotics
      • 3D Content Central – Host an enormous variety of free CAD models including all components of the FIRST Kit of Parts
      • Autodesk FIRSTbase – Where all Autodesk submissions are made, voted on, and archived. FIRST teams can also download Professional licenses of Autodesk software for free here once registered
  • Product Data Management (PDM)
    • This is how you store CAD data, versions and metadata
    • We use GrabCAD
  • Design for Manufacturability (DFMA)
    • This is thinking in terms of tolerances, tooling, assembly order and payoffs
    • GD&T or FT&A are big parts of DFMA

 

After you finish you robot you will need to purchase or fabricate all of the items on your Bill of Materials (BOM). You may have planned to fabricate several of the parts by hand, making parts by hand is defiantly one way to go, but you need to understand the limitations of this fabrication method often include large tolerance issues for many FRC teams. Tolerances issues translate into assembly slop that could result in misalignment of major structural components or significant amounts of inconsistency when performing tasks. So instead we recommend using parts that are made using Computer Aided Manufacturing (CAM) techniques. There are many CAM options available to teams;

  • CNC routing
  • CNC lathe
  • CNC laser
  • CNC welding
  • CNC water jet
  • 3D prining

 

CNC stands for Computer Numerical Control and 3D printing is a euphemism for additive manufacturing techniques. Both of these types of machines allow teams to focus on making the data that the CNC machine will need to turn raw materials into the parts that you designed. For many machines the team will need to post process the CAD data to make the commands for specific machine they are going to use to fabricate the part. Each CNC or 3D vendor will identify what the post processor software the team will need to use. For CNC routers for example teams will need to identify the x,y,z, zero point, bit size, rpm, cutting paths etc.. so that the part is fabricated correctly once it is placed in the machine. The same type of forethought is needed for 3D printers, where will the machine start to print, will it print just the exterior or fill in in the interior, does it need supports to avoid deformation during printing, etc…

 

The Team is just starting its grab cad and is making all of our CAD available here

There are numerous other teams who also make their CAD available

Sprockets, Chains, Pulleys, Belts & Gears

Motors, springs and pneumatics are just of few examples of the many ways to generate mechanical energy on an FRC robot. However, in most instances where you generate the mechanical energy is not where you want to use it, so lets discus some of the ways to transfer and change mechanical energy from what is produced at the source to what / where it is needed on the robot.

In most instances the mechanical energy produced is rotational in nature, this means it will have an RPM and a torque associated with it. Here are some videos that will teach what these two terms are.


Now that you understand RPM and torque we can get down to transforming and transferring rotational mechanical energy. Sprockets, Gears and Hubs can all be attached directly to the source of the energy in a variety of ways. Once attached they are each used in conjunction with a specific transfer medium.

  • Sprockets transfer energy to chain
    300px-ChainAndSprocketSketch
  • Pulleys transfer energy to belts
    gr_pulley_system
  • Gears transfer energy to other gears
    geardrive-733x604

 

Since these are all mechanical transfer mediums there are losses due to friction that vary between 5% and 40% based on the system you have selected, the tolerances of the detail parts and the assembly tolerances. Here is great video that walks you through these transfer mechanisms in a little more detail;

Here are some more details on these systems