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Custom Actions

Basic Examples

In this guide, you will learn how to create your own custom actions for your subsystems. We will be creating a simple intake subsystem with a single motor.

Step 1: Create your subsystem

First, we need to create our subsystem. NextRunner does not include any formal Subsystem class or interface, but we can create a class and pass in a HardwareMap instance to the constructor in order to access hardware.

class Intake(hwMap: HardwareMap) {
    private val motor = hwMap[DcMotorEx::class.java, "intake_motor"]
}

public class Intake {
    private DcMotorEx motor;
    public Intake(HardwareMap hwMap) { 
        motor = hwMap.get(DcMotorEx.class, "intake_motor");
    }
}

Step 2: Create your actions

Now, we will create two actions: run() and stop(). The run() action will turn the intake motor on, and the stop() action will turn it off.

run() action

To create the run() action, we will create a new Action that sets the motor power to 1.

fun run(): Action = Action { 
    motor.power = 1.0
    true
}

public Action run() {
    return p -> {
        motor.setPower(1.0);
        return true;
    };
}

Note that we return true at the end of the action. This is because we want the action to continue running until it is interrupted by another action (like stop()).

stop() action

Now, let's create the stop() action. This action will set the motor power to 0 and then complete.

fun stop(): Action = Action { 
    motor.power = 0.0
    false
}

public Action stop() {
    return p -> {
        motor.setPower(0.0);
        return false;
    };
}

This time, we return false at the end of the action. This tells the ActionRunner that the action is complete and can be removed from the queue.

Final Result

Here is the final code for our Intake subsystem:

class Intake(hwMap: HardwareMap) {
    private val motor = hwMap[DcMotorEx::class.java, "intake_motor"]

    fun run(): Action = Action { 
        motor.power = 1.0
        true
    }

    fun stop(): Action = Action { 
        motor.power = 0.0
        false
    }
}

public class Intake {
    private DcMotorEx motor;
    public Intake(HardwareMap hwMap) {
        motor = hwMap.get(DcMotorEx.class, "intake_motor");
    }

    public Action run() {
        return p -> {
            motor.setPower(1.0);
            return true;
        };
    }

    public Action stop() {
        return p -> {
            motor.setPower(0.0);
            return false;
        };
    }
}

More Complex Actions

The run() and stop() actions are simple, but what if we want to create more complex actions? Let's take a look at a few examples.

Lift

Let's create a lift subsystem that can move to a specific position. This is useful for things like moving a lift to a scoring position.

First, let's create our subsystem. We will need a motor for the lift.

class Lift(hwMap: HardwareMap) {
    private val motor = hwMap[DcMotorEx::class.java, "lift_motor"]
}

public class Lift {
    private DcMotorEx motor;
    public Lift(HardwareMap hwMap) { 
        motor = hwMap.get(DcMotorEx.class, "lift_motor");
    }
}

Now, let's create an action that moves the lift to a specific position. We will use a simple P controller with a gravity feedforward to move the motor to the target position. The feedforward term will help to counteract the force of gravity on the lift.

fun goToPosition(targetPosition: Double): Action = Action {
    val kP = 0.01 // Proportional gain, this should be tuned
    val kG = 0.1 // Gravity feedforward, this should be tuned

    val error = targetPosition - motor.currentPosition
    motor.power = (error * kP) + kG

    // continue if error is greater than 10 ticks
    abs(error) > 10 
}

public Action goToPosition(double targetPosition) {
    return p -> {
        double kP = 0.01; // Proportional gain, this should be tuned
        double kG = 0.1; // Gravity feedforward, this should be tuned

        double error = targetPosition - motor.getCurrentPosition();
        motor.setPower((error * kP) + kG);

        // continue if error is greater than 10 ticks
        return Math.abs(error) > 10;
    };
}

This action will move the motor to the targetPosition and then complete once it is within 10 ticks of the target.

Claw

Now, let's create a claw subsystem that can open and close.

class Claw(hwMap: HardwareMap) {
    private val servo = hwMap[Servo::class.java, "claw_servo"]
}

public class Claw {
    private Servo servo;
    public Claw(HardwareMap hwMap) { 
        servo = hwMap.get(Servo.class, "claw_servo");
    }
}

Now, let's create the open() and close() actions. These actions will set the servo position and then complete immediately.

fun open(): Action = Action {
    servo.position = 0.1
    false // complete immediately
}

fun close(): Action = Action {
    servo.position = 0.8
    false // complete immediately
}

public Action open() {
    return p -> {
        servo.setPosition(0.1);
        return false; // complete immediately
    };
}

public Action close() {
    return p -> {
        servo.setPosition(0.8);
        return false; // complete immediately
    };
}

This time, we return false at the end of the action. This tells the ActionRunner that the action is complete and can be removed from the queue.

Final Result

Here is the final code for our Lift and Claw subsystems:

class Lift(hwMap: HardwareMap) {
    private val motor = hwMap[DcMotorEx::class.java, "lift_motor"]

    fun goToPosition(targetPosition: Double): Action = Action {
        val kP = 0.01 // Proportional gain, this should be tuned
        val kG = 0.1 // Gravity feedforward, this should be tuned

        val error = targetPosition - motor.currentPosition
        motor.power = (error * kP) + kG

        // continue if error is greater than 10 ticks
        abs(error) > 10 
    }
}

class Claw(hwMap: HardwareMap) {
    private val servo = hwMap[Servo::class.java, "claw_servo"]

    fun open(): Action = Action {
        servo.position = 0.1
        false // complete immediately
    }

    fun close(): Action = Action {
        servo.position = 0.8
        false // complete immediately
    }
}

public class Lift {
    private DcMotorEx motor;

    public Lift(HardwareMap hwMap) { 
        motor = hwMap.get(DcMotorEx.class, "lift_motor");
    }

    public Action goToPosition(double targetPosition) {
        return p -> {
            double kP = 0.01; // Proportional gain, this should be tuned
            double kG = 0.1; // Gravity feedforward, this should be tuned

            double error = targetPosition - motor.getCurrentPosition();
            motor.setPower((error * kP) + kG);

            // continue if error is greater than 10 ticks
            return Math.abs(error) > 10;
        };
    }
}

// in java these should be placed in separate files

public class Claw {
    private Servo servo;
    public Claw(HardwareMap hwMap) { 
        servo = hwMap.get(Servo.class, "claw_servo");
    }

    public Action open() {
        return p -> {
            servo.setPosition(0.1);
            return false; // complete immediately
        };
    }

    public Action close() {
        return p -> {
            servo.setPosition(0.8);
            return false; // complete immediately
        };
    }
}

Next Steps

Now that you have created your custom actions, you can learn how to use them in your TeleOp OpMode in the next guide.