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Lesson 3.5: Build Dynamic Power Logic with Multiple Variables

Technical Context​

A competitive robot rarely runs at one static speed. Combining inputs, multipliers, and offsets can create adjustable control behavior. For example, a driver-selected multiplier can reduce maximum power for precise alignment. Compensating for battery sag requires a measured voltage model or closed-loop velocity controller; a fixed multiplier alone cannot ensure consistent performance.

How to Think Through Multi-Variable Power Logic​

This lesson combines different variable types in a single expression. When an int and a double are used in the same math operation, Java "promotes" the result to a double to maintain precision. You must be careful with assignment operators; using = updates the variable's value, while using *= or += allows you to modify the current value relative to its previous state.

Annotated Code​

@TeleOp(name="Dynamic_Control")
public class DynamicControl extends OpMode {

    DcMotor drive;

    // Multi-variable setup
    double baseSpeed       = 0.5;
    double boostMultiplier = 2.0;
    int    gearSetting     = 1;

    @Override
    public void init() {
        drive = hardwareMap.get(DcMotor.class, "motor");
    }

    @Override
    public void loop() {
        double finalPower;

        if (gamepad1.right_trigger > 0.5) {
            // Math combining double inputs and multipliers
            finalPower = baseSpeed * boostMultiplier;
        } else {
            finalPower = baseSpeed;
        }

        drive.setPower(finalPower);
        telemetry.addData("Gear", gearSetting);
        telemetry.addData("Output Power", finalPower);
    }
}

Fill-in-the-Blank Practice​

  1. The operator used to assign a new value to a variable is __________.
  2. If you multiply an int by a double, the resulting datatype will be a/an __________.
  3. To perform math and update a variable in one step (e.g., adding 5 to the current value), you use the __________ operator.
Show answers
  1. =
  2. double (Java promotes the result to the wider type)
  3. +=

Simulator Practice​

Robot Scenario: Create a "Precision Mode." If the driver holds the left bumper, the motor power should be exactly half of the joystick input. Use variables for input, scaleFactor, and finalPower.

Telemark Unit 3 Simulator
Tracks `String`, `double`, `boolean`, and `int` variables as you edit.
Supports telemetry, `gamepad1`, simple `if` blocks, and basic `setPower()` math.
Does not simulate full hardware behavior or complex Java control flow.
Show answer
@Override
public void loop() {
    double input = -gamepad1.left_stick_y;

    double finalPower;

    if (gamepad1.left_bumper) {
        finalPower = input * scaleFactor;
    } else {
        finalPower = input;
    }

    motor.setPower(finalPower);
}

A Team Separates Input from Scale​

Titan Robotics Club reads drive inputs, applies separate drive and turn scales, then sends the results to its drive base. This smaller version keeps the variable flow visible:

double forwardInput = -gamepad1.left_stick_y;
double turnInput = gamepad1.right_stick_x;
double forwardPower = forwardInput * driveScale;
double turnPower = turnInput * turnScale;
robot.drive.arcadeDrive(forwardPower, turnPower);

The input array and framework types were replaced with lesson vocabulary. The separate variables still make each value and scale easy to inspect. Adapted from Team 3543 Titan Robotics Club's FtcTeleOp.java at a pinned commit under the MIT License.

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