Motors

package com.arcrobotics.ftclib.hardware.motors

FTCLib brings you the best abstraction and additions to your programmed motors. Unfortunately, unlike FRC, FTC motors are restricted heavily when it comes to software. Consequently, we decided not to directly port the SpeedController features from WPILib.

The Motor Interface

Fortunately, however, we have provided plenty of motors for your customization and optimization needs. Instead of SpeedController, the base abstraction for your motors is the Motor interface that can be found here.

The javadocs on the interface explains how each method is to be used when creating a custom motor object.

Below is an example of a custom motor:

import com.qualcomm.robotcore.hardware.DcMotor;
import com.qualcomm.robotcore.hardware.HardwareMap;

public class YellowJacket435 implements Motor {
  
    private DcMotor m_motor;
    private double resetVal;
    
    public static final double TICKS_PER_REV = 383.6;

    public YellowJacket435(HardwareMap hMap, String name) {
      m_motor = hMap.get(DcMotor.class, name);
    }
    
    @Override
    public void set(double speed) {
      m_motor.setPower(speed);
    }

    @Override
    public double get() {
      return m_motor.getPower();
    }

    @Override
    public void setInverted(boolean isInverted) {
      m_motor.setDirection(!isInverted ? DcMotor.Direction.FORWARD : DcMotor.Direction.REVERSE);
    }

    @Override
    public boolean getInverted() {
      return m_motor.getDirection() == DcMotor.Direction.REVERSE;
    }

    @Override
    public void disable() {
       m_motor.close();
    }

    @Override
    public void pidWrite(double output) {
      set(output);
    }
    
    @Override
    public void stopMotor() {
      set(0);
    }
    
    public double getEncoderCount() {
      return m_motor.getCurrentPosition() - resetVal;
    }

    public void resetEncoder() {
      resetVal += getEncoderCount();
    }

    public void getNumRevolutions() {
      return getEncoderCount() / TICKS_PER_REV;
    }

}

Alternatively to multiplying the power by some multiplier, we can just set the direction of the DcMotor object with setDirection(DcMotor.Direction direction).

MotorGroup

The MotorGroup class takes a set of motors and controls them like one set of objects. This is extremely useful for a differential drive.

SimpleMotor

The implementation sample in FTCLib is the SimpleMotor class. If you do not want to use custom motors, you can still use the FTCLib-compatible motor that has already been written for you.

MotorEx

The MotorEx class is an extension of the motor interface that allows for more customization and control. It adds in the ZeroPowerBehavior functionality of the DcMotor class in the SDK and implements a proportional control loop to control the deceleration.

For the pidWrite(double output) method, we introduce the SimpleMotorFeedForward that we discussed in controllers along with PID control.

SimpleMotorEx

Just like the motor interface, MotorEx has an implementation seen in SimpleMotorEx. All it does is define the abstract methods for you in case you do not want to create your own custom hardware.

EncoderEx

The EncoderEx class takes a MotorEx object into the constructor and makes use of custom and optimized methods for tracking position and encoder counts. This is where you can have the motor object run to a position as well, in an attempt to avoid utilizing the RUN_TO_POSITION run mode for the DcMotor.

CRServo

Th CRServo class is just a motor object intended to be used for a continuous rotation servo. To use it, you create a custom implementation of the Motor interface where you pass a CRServo object from the SDK into the constructor. Then, using the CRServo class in FTCLib, you can extend its functionality and capabilities.