Robot Integration

By now your team has a drivetrain that drives and at least one mechanism that works on the bench. Integration is the job of turning those pieces into one robot. It sounds simple, but most problems show up at the joins: an arm that hits a wheel, a wire that gets pinched, a robot that tips over when the lift goes up, or two pieces of code that both try to control the same motor. Plan integration carefully and you avoid days of rework.

Mounting mechanisms on the chassis

1. 1
   Plan the layout

   Sketch a top and side view, or place the parts in your CAD assembly. Mark where every mechanism, the Control Hub, the battery and the power switch will go.
2. 2
   Check clearances

   With the robot powered off, move each mechanism through its full range of motion by hand. Nothing should touch wheels, wires or other mechanisms at any point.
3. 3
   Mount to strong points

   Bolt mechanisms to the frame channels, not to thin plates. Use at least two fasteners per mount so the part cannot pivot, and use lock nuts or nylon-insert nuts on anything that vibrates.
4. 4
   Keep access open

   You must be able to swap the battery, reach the power switch and plug a cable into the hub without taking the robot apart. At an event you may have only minutes between matches.

Weight distribution

Every robot has a center of gravity: the point where its weight balances. Keep heavy parts, like the battery and motors, low and near the middle. A tall lift or a long arm raises the center of gravity when extended, so the robot can tip when it brakes or turns quickly. Uneven weight also causes problems you might blame on code: if one side is much heavier, the light-side wheels slip and your Autonomous drifts.

• Check that all wheels touch the tiles evenly; a rocking robot loses traction.
• Extend the arm or lift fully and drive slowly, then stop sharply. If the robot lifts a wheel, lower or move weight.
• Mount the battery low and secure it so it cannot slide during a collision.
• Weigh or feel each side by lifting the robot by one end, then the other, to spot obvious imbalance.

Wiring for added mechanisms

• Route wires along the frame and secure them with zip ties every few inches.
• Leave a loose service loop where a wire crosses a moving joint, so the joint can move without pulling the wire.
• Keep wires away from gears, belts, wheels and pinch points.
• Label both ends of every cable with its port and name, for example arm on motor port 2.
• Make sure the name in the robot configuration matches the name in your code exactly.

Combining code subsystems

When each mechanism lives in its own class, your TeleOp and your Autonomous can share the same tested code. The class sets up its hardware once and gives you simple methods like goTo(UP). If you later change a motor direction or a preset position, you fix it in one place instead of in every OpMode.

1import com.qualcomm.robotcore.hardware.DcMotor;
2import com.qualcomm.robotcore.hardware.HardwareMap;
3
4public class Arm {
5    public static final int DOWN = 0;
6    public static final int UP = 800; // measure this on your own robot
7
8    private final DcMotor motor;
9
10    public Arm(HardwareMap hardwareMap) {
11        motor = hardwareMap.get(DcMotor.class, "arm");
12        motor.setZeroPowerBehavior(DcMotor.ZeroPowerBehavior.BRAKE);
13        motor.setMode(DcMotor.RunMode.STOP_AND_RESET_ENCODER);
14        motor.setTargetPosition(DOWN);
15        motor.setMode(DcMotor.RunMode.RUN_TO_POSITION);
16    }
17
18    public void goTo(int ticks) {
19        motor.setTargetPosition(ticks);
20        motor.setPower(0.5);
21    }
22
23    public int getPosition() {
24        return motor.getCurrentPosition();
25    }
26}