Intakes and Grippers

Almost every point in a match starts the same way: your robot has to get control of a game element. There are two big families of mechanisms for this. Intakes usually use spinning parts to pull elements in, often straight off the floor. Grippers (or claws) close around a single element and hold it firmly so it can be placed precisely. Many good robots use both: an intake to collect quickly and a gripper or holder to score accurately.

Touch it, own it

A useful goal for any intake is touch it, own it: the moment any part of the mechanism touches a game element, the element should get pulled in and controlled. Why does this matter so much? During a match, drivers are rushing, the field is crowded and the robot is rarely lined up perfectly. If your intake only works when the element is exactly centred, the driver wastes seconds lining up. A wide, forgiving intake lets the driver drive roughly at the element and still collect it, which shortens every scoring cycle.

Active roller intakes

An active intake has one or more rollers (spinning shafts) driven by a motor or a continuous-rotation servo. The rollers grip the element and drag it into the robot. Active intakes are fast and forgiving, which is why they are so common. The trade-off is that they need a motor or servo, careful tuning, and a way to stop the element in the right place once it is inside.

• Compression: how much the roller squeezes the element. Too little and it slips; too much and it jams or stalls the motor.
• Roller speed: faster pulls elements in quicker, but very fast rollers can bounce elements away. Test a few speeds.
• Width: a wider intake is more forgiving, but adds weight and may hit size limits. Check the current Competition Manual.
• Stopping point: use a hard stop, a ramp or a sensor so the element ends up in the same place every time.

Compliant wheels and surgical tubing

The material on the roller matters as much as the roller itself. Compliant wheels are soft, flexible wheels that squish around the element. They grip well, tolerate misalignment, and come in different softness levels. Surgical tubing is stretchy rubber tubing that you thread or zip-tie onto a roller hub so it sticks out like flaps. It is cheap, easy to replace, and easy to tune: shorter flaps grip harder, longer flaps are gentler and reach further. Both are excellent for 'touch it, own it' because they bend instead of bouncing elements away.

Grippers and claws

A servo claw uses a servo to open and close one or two fingers around an element. Claws are slower to grab than a roller intake because the driver has to line up first, but they hold one element very securely and can release it exactly where you want. That makes them great for precise placing. The grip can be active (a powered motion squeezes the element) or passive (the element is held by shape, springs or friction without power).

1import com.qualcomm.robotcore.eventloop.opmode.LinearOpMode;
2import com.qualcomm.robotcore.eventloop.opmode.TeleOp;
3import com.qualcomm.robotcore.hardware.Servo;
4
5@TeleOp(name = "Claw Test")
6public class ClawTest extends LinearOpMode {
7    // Example values: tune these on your own robot
8    static final double CLAW_OPEN = 0.30;
9    static final double CLAW_CLOSED = 0.65;
10
11    @Override
12    public void runOpMode() {
13        Servo claw = hardwareMap.get(Servo.class, "claw");
14
15        waitForStart();
16
17        while (opModeIsActive()) {
18            if (gamepad2.right_bumper) {
19                claw.setPosition(CLAW_CLOSED);
20            } else if (gamepad2.left_bumper) {
21                claw.setPosition(CLAW_OPEN);
22            }
23            telemetry.addData("Claw position", claw.getPosition());
24            telemetry.update();
25        }
26    }
27}

So which should you build? Choose an intake when you need to collect many elements quickly from the floor, and a claw when you need to hold one element and place it precisely. If you are unsure, prototype both in cardboard and test them, which you will learn to do in Lesson 4.