Intakes are a subsystem on pretty much every robot where the purpose of the subsystem is to acquire game pieces and store them in the robot. Since intakes have such a broad definition, there are a large amount of different types of intakes.
General Intake Design Guidelines
- Try to use rollers/wheels over pinching/grasping mechanisms. Rollers almost always are more forgiving for alignment to pick up a game piece.
- When using rollers, make sure there are no dead zones where a wheel is not in contact with the game piece.
- Read the intake section of this blog for a guide on some roller types.
Choosing an Intake Ratio
- Surface speed of roller at least 2 * robot max speed
- If driving towards an object at max speed, you still need to be able to have net positive intaking speed
- The 2* or more is needed because with a single top roller, the object will be rolling, so middle of object has speed V getting pushed, 0 at carpet (assuming in worst case no slip condition) and 2*V at top of object
- Surface speed = motor free speed RPM * 80% (efficiency) * gear ratio * roller circumference (length units) * conversion factors for units
Rollers and Compression
- Maximize grippiness (contract friction) through all methods to maximize energy transfer, and thus intake speed and reliability
- Friction = Coefficient of Friction * Normal Force between objects
- Find the most grippy pair of materials, such as rubbers or fancy grippy tapes, to increase coefficient of friction
- Have enough normal force to lift object against gravity and pull in quickly
- Normal force needs to be generated between roller-object-ground, roller-object-bumper, or roller-object-something
- If object is rigid (examples: 2019 hatches, 2018 cubes, 2017 wiffle balls) you need compliance/compression either in the mechanism (pivoting point allow floating wheel/roller and springs/pneumatic-pressure generates squeeze force) or in the wheels/rollers (Compliant Wheels, thick rubber surfaces).
- If object is compliant (examples: most balls, 2023 cubes/cones) then you can have a rigid roller and instead compress the object
- Don’t have too much normal force because it increases resistance/drag which can slow system down and make it drawing more power, this is why maximizing grippiness through material selection is optimal
Intake Size
- Maximize intake area to simplify driver/autonomous skill required
- Ideally intake is as wide as entire robot, which usually means its better to pull object over bumper and then center/serialize inside robot
- Also means intake has to deploy outside bumper perimeter which leads to point building robust intakes
Build Robust Intakes
- Build robust intakes
- Use 1/4” Polycarbonate plates for good mix of stiffness and toughness (bend then spring back without cracking)
- Big plates with plenty of material around holes. Ideally small holes, that’s why the dead axle roller design is so good, you only have a bolt hole in the plate
- Have spares and design-for and practice quickly repairing
- Use Sensors
- Hall effect sensors to zero motor driven deploy
- Beam-break sensor (ex. retro reflective laser) to know that object is in robot and automatically trigger intake to stow, elevator to move, etc
- Color sensor to detect multicolored game objects (ex. 2022 balls)
Intake Indexing
Regularly intakes will have to index multiple pieces, or direct game pieces to a specific place in the robot to be singularized (IE. Intake is multiple game pieces wide, but needs to narrow down to one game piece wide)