Wiki

[technik3k]

Preparing for the competition day

References (redundant?):

https://www.roboticseducation.org/resources-library/
101 Things I Wish I'd Known Before My First VEX Tournament
Advice for first competition?

https://www.vexwiki.org/robotics_competitions/101_things
https://www.roboticseducation.org/documents/2013/06/101-things.pdf/

[technik3k]

Tips on how competition works

To be expanded:

• Qualifications
• Scouting:
  At tournaments, there are various ways of scouting that can be done to improve your chances of doing well. They are as follows:

• Match scouting: Before each qualification match, it is extremely important that you go and talk to your alliance partner, to coordinate autonomous programs, match strategies, and any other miscellaneous aspects to the upcoming match. This will also tie in with the second way if scouting.

• General tournament scouting: Throughout s tournament, it is helpful to take notes on each team/robot in attendance. Whether it be a quick robot summary, or detailed notes on the successes and weak points of each mechanism, doing so will allow you to be better prepared for your matches. This ties in to the 1st way of scouting, as you should be taking down notes on your alliance partners and opponents after every match.

When it comes time for alliance selection, having notes and scouting data is extremely helpful when deciding on who to pick for the elimination bracket. They will also help you to find any “hidden gems” that might be a better pick than some of the higher ranked robots. Scouting will also prepare you if a team decides to use the “scorched earth” strategy (go down the line of teams and ask each one until one accepts) to mess up any potential powerhouse alliances.

• Alliance selection
• BO1
• Skills
• Judging
• Who qualifies

[technik3k]

Beyond the competition

What else is there in VRC beyond going to competitions?

[technik3k]

School based vs independent team / fundraising

TBD

[technik3k]

Tips for organizing the team

Getting Started in Robotics (Tips and Advice)

https://www.roboticseducation.org/resources_library/how-to-start-and-organize-a-vrc-team/

List of products/items to purchase?
What parts should I not buy?

Should this be here or moved up to post 25?
Help motivating procrastinators to do their job
How to help combat un-involved team members

How many people on a team?

[technik3k]

Tools

Sort tools in order of importance…
Add pictures?

• wrenches 1/4, 11/32
• screwdrivers hex (5/64,3/32), star (T?)
• pliers, needlenose pliers, diagonal cutters, etc…
• tabletop grinder
• dremel

Custom Tools:

…

Tips:

Don’t strip screw heads - sharpen Hex screwdrivers regularly!

…

Safety considerations:

Wear goggles!!!
…

Color coding screwdrivres and wrenches:

Special tools

Insert puller:

Drilling template:

Bearing cutting template:

[technik3k]

Alternative part sources

https://www.robosource.net

VEX Cost Reductions
Vex Low Cost Identical Legal Parts Compilation
Cheaper Option for Nylon Washers

Cheap Alternative Tiles

[technik3k]

Reserved for all Omni tank drive

[technik3k]

Reserved for X-Drive wiki entry

Why is X-Drive Faster? - AURA

2 vs 4 motor drive

Here, this is the most important graph to understand X-Drive:

Source: AURA

If you drive forward, backward, or to the side - all four motors are providing power, the velocity is MotorRPM x sqrt(2) and pushing force is 4 x OneMotorTorque/sqrt(2).

If you drive at a diagonal, then only two motors are providing power, velocity is MotorRPM and pushing force is 2 x OneMotorTorque.

Essentially, X-Drive speed is 1.41 times faster and pushing force is 1.41 times weaker than the ordinary tank drive with the identical 4 wheels & 4 motors.

Also, here are the links to the similar topics from the previous seasons: Two motor drives? , X-Drive Speed , Extinct X-Drive?

[technik3k]

Reserved for H-Drive wiki entry

https://en.m.wikipedia.org/wiki/H-drive

H-Drive?

[technik3k]

Reserved for Mecanum wheels drivetrain wiki entry

Omni wheel vs Mecanum

Meccanum Problems

You need to make sure that your mecanum wheels are mounted correctly. They need to have a specific orientation. The bottom of the robot they should look like this…

Code examples:

Vexcode Mecanum Wheel Program

Tank control

int left = Controller.Axis3.position(vex::percent);
int right = Controller.Axis2.position(vex::percent);
int sideways = Controller.Axis4.position(vex::percent);

//you can also calculate this...
int turn =    (right - left) * 0.5;
int forward = (right + left) * 0.5;

frontRight.spin(vex::forward, right - sideways, vex::percent);
frontLeft.spin(vex::forward,  left  + sideways, vex::percent);
backRight.spin(vex::forward,  right + sideways, vex::percent);
backLeft.spin(vex::forward,   left  - sideways, vex::percent);

Arcade Drive

int forward = Controller.Axis3.position(vex::percent);
int sideways = Controller.Axis4.position(vex::percent);
int turn = Controller.Axis1.position(vex::percent);

frontRight.spin(vex::forward, forward - sideways + turn, vex::percent);
frontLeft.spin(vex::forward,  forward + sideways - turn, vex::percent);
backRight.spin(vex::forward,  forward + sideways + turn, vex::percent);
backLeft.spin(vex::forward,   forward - sideways - turn, vex::percent);

A Holonomic drive is free to move in any direction without having to rotate around its axis.

https://en.wikipedia.org/wiki/Holonomic_(robotics)

One form consists of 3 or 4 omniwheels mounted at angles to each other. It is good for lateral movement, and increases speed and power of turns. However, linear drive speed and power are decreased since some or all of the powered wheels run at angles to the bot’s motion. All wheels must be omni wheels in order for this drive to function. The 4-wheel version is referred to as " X-Drive".

Another omniwheel Holonomic drive is the “H-Drive”, where 1 omniwheel is placed at right angles to the other four conventionally mounted omniwheels.

Mecanum drive is holonomic drive where four mechanum wheels are placed in a tank drive format. The wheels should look like this when looking from top:

Like all holonomic drives, mechanum bots can strafe, and does so with a simple rectangular base. However, mechanum wheels have rollers that slip, reducing traction and pushing power.

[technik3k]

Reserved for additional drivetrain discussion entry

Kiwi:

@rhowbot

Kiwi Drive Bot

Lynfield:

@vdsa

Swerve:

@93870A

Shifting X-Drive

…

[technik3k]

Reserved for additional drivetrain discussion entry

Are tracked vehicles viable in Vex?

[technik3k]

Reserved for additional drivetrain discussion entry 1

[technik3k]

Reserved for additional drivetrain discussion entry 2

[technik3k]

Reserved for additional drivetrain discussion entry 3

[technik3k]

Reserved for comparison of the VEX wheel types

Omni wheel vs Mecanum

The first table shows coefficient of friction calculated by dividing the force by the base weight, which experimentally accounts for both material-to-material and rolling friction:

And the second table shows the amount of force (in lbf) required to pull or push a typical 15 lb robot:

Conversion of the robot weight into tractive force:

https://sites.google.com/site/dkellytest1/drive-systems/comparison-of-wheels

[technik3k]

Reserved for discussion of the Claw (intake)

[technik3k]

Reserved for Side Rollers wiki entry

Are side rollers usefull???

[technik3k]

Reserved for Passive Intakes wiki entry

Need help with reverse double four bar!

Here is an album of pics of our worlds ITZ robot