what does DcMotorEx setVelocity do

The setVelocity method is an enhanced motor control method available on the DcMotorEx interface used for velocity control . It can be used as a solution when a motor fails to reach full speed using the standard .setPower method .

Additional information on setting velocity is covered in these restricted resources:

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Setting Velocity | REV DUO Control System

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Open REV Robotics Docs

Setting Velocity | REV DUO Control System

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SDK Motors > Hidden Methods

Game Manual 0·CC BY-NC 4.0

All REV hub DC motors are instances of DcMotorEx, which exposes some more methods to the user, such as velocity control and current draw measurement.

Note: There is no downside to using DcMotorEx, in order to convert a DcMotor to a DcMotorEx the user simply just needs to cast the DcMotor returned by the hardwareMap to a DcMotorEx.

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FTC SDK API > com.qualcomm.robotcore.hardware > DcMotorEx

FTC SDK API·BSD 3-Clause

The DcMotorEx interface provides enhanced motor functionality which is available with some hardware devices. The DcMotorEx interface is typically used as a second interface on an object whose primary interface is DcMotor. To access it, cast your DcMotor object to DcMotorEx. However, it is perhaps prudent to first test whether the cast will succeed by testing using 'instanceof'.

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Control Loops > PID > Built-In PID Controller

Game Manual 0·CC BY-NC 4.0

For situations where one needs to control the velocity or position of a single motor, the built in PID controller can be used. PID can be enabled by changing the run mode to RUN_USING_ENCODER

Hint: Many misunderstand the use of RUN_USING_ENCODER, many may mistake that it is necessary to use this mode for the encoders to work at all, but this is not true. Instead, RUN_USING_ENCODER enables velocity feedback using the encoder. If you are using an external PID controller such as one that you implement, generally, it is recommended that you use RUN_WITHOUT_ENCODER.

For official documentation on the built in PID controller, see here (https://docs.revrobotics.com/duo-control/programming/using-encoder-feedback)

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Changing PID Coefficients

FTC Docs·BSD 3-Clause

The REV Robotics Control Hub and REV Robotics Expansion Hub allow a user to change the PID coefficients used for closed loop motor control. The PID coefficients are channel and mode specific.

The following op mode uses an extended or enhanced DcMotor class (called “DcMotorEx”) to change the PID coefficients for the RUN_USING_ENCODER mode for a motor named “left_drive”. The op mode uses the setPIDCoefficients method of the DcMotorEx class to change the values. This method is not available with the standard DcMotor class.

Note that changes made to the PID coefficients do not persist if you power cycle the REV Robotics Control Hub or REV Robotics Expansion Hub. If you need your changes to the PID to persist, you should consider modifying your op mode to store state information on the Control Hub or Android phone. The Android Developer website has a tutorial on how to save data from your app onto an Android device here (https://developer.android.com/training/data-storage)

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SDK Motors > Hidden Methods > DcMotorEx > Tips

Game Manual 0·CC BY-NC 4.0

While current readings are not bulk read, current alerts (isMotorOverCurrent()) is bulk read.
PID/PIDF coefficients use internal units for the output, a two byte short from -32767 to 32767, instead of the user -1 to 1.
The default getVelocity() method returns the encoder velocity in ticks per second.
The RunMode STOP_AND_RESET_ENCODERS is not actually a run mode. Instead, it just sets the power to zero and sends a LynxResetMotorEncoderCommand. This command can be issued manually if one wants to easy reset a motor encoder without changing the run mode.

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Changing PIDF Coefficients

FTC Docs·BSD 3-Clause

The REV Robotics Control Hub or REV Robotics Expansion Hub allows a user to change the PIDF coefficients used for closed loop motor control. The PIDF coefficients are specific to each channel (motor port) and to each RunMode.

The following sample OpMode uses an extended or enhanced DcMotor class (called “DcMotorEx”) to change the PIDF coefficients for the RUN_USING_ENCODER RunMode for a motor named “left_drive”. The OpMode uses the setPIDFCoefficients method of the DcMotorEx class to change the values. This method is not available with the standard DcMotor class.

Note that changes made to the PIDF coefficients do not persist if you power cycle the REV Robotics Control Hub or REV Robotics Expansion Hub. If you need your changes to persist, consider modifying your OpMode to store state information on the Control Hub or Android phone. The Android Developer website has a tutorial on how to save data from your app onto an Android device here (https://developer.android.com/training/data-storage)

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FTC SDK API > com.qualcomm.robotcore.hardware > DcMotorImplEx

FTC SDK API·BSD 3-Clause

DcMotorImplEx is a motor that supports the DcMotorEx interface in addition to simply DcMotor .

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Control Loops > PID > Debugging Built-In PID Controller

Game Manual 0·CC BY-NC 4.0

+-----------------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Problem | Solution | +===========================================================+===========================================================================================================================================================================+ | Motor goes at Full Speed regardless of velocity setpoint | Most of the time this occurs when one of two things occurs: | | | | | | #1: Your encoder is not connected properly. | | | | | | Diagnosis: Log your encoder position to telemetry, if the position oscillates between 0 - 1 make sure you have the correct cable and it is seated correctly. | | | | | | #2: Your motor is going in the wrong direction. | | | | | | Diagnosis: Log your velocity to telemetry, if you have a positive reference velocity and the output is negative or vice versa then your motor is plugged in backwards. | +-----------------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Motor does not reach full speed with .setPower | Use the .setVelocity method as part of DcMotorEx or use RUN_WITHOUT_ENCODER with an external PID controller. | +-----------------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

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FTC SDK API > com.qualcomm.robotcore.hardware > DcMotor.RunMode

FTC SDK API·BSD 3-Clause

The run mode of a motor RunMode controls how the motor interprets theit's parameter settings passed through power- and encoder-related methods.Some of these modes internally use PID control to achieve their function, while others do not. Those that do are referredto as "PID modes".

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Changing PID Coefficients

FTC Docs·BSD 3-Clause

package org.firstinspires.ftc.teamcode;

import com.qualcomm.robotcore.eventloop.opmode.Autonomous;
import com.qualcomm.robotcore.eventloop.opmode.LinearOpMode;
import com.qualcomm.robotcore.hardware.DcMotor;
import com.qualcomm.robotcore.hardware.DcMotorEx;
import com.qualcomm.robotcore.hardware.PIDCoefficients;

/**
 * Created by tom on 9/26/17.
 * This assumes that you are using a REV Robotics Control Hub or REV Robotics Expansion Hub
 * as your DC motor controller.  This op mode uses the extended/enhanced
 * PID-related functions of the DcMotorEx class.
 */

@Autonomous(name="Concept: Change PID", group = "Concept")
public class ConceptChangePID extends LinearOpMode {

    // our DC motor.
    DcMotorEx motorExLeft;

    public static final double NEW_P = 2.5;
    public static final double NEW_I = 0.1;
    public static final double NEW_D = 0.2;

    public void runOpMode() {
        // get reference to DC motor.
        // since we are using the Control Hub or Expansion Hub,
        // cast this motor to a DcMotorEx object.
        motorExLeft = (DcMotorEx)hardwareMap.get(DcMotor.class, "left_drive");

        // wait for start command.
        waitForStart();

        // get the PID coefficients for the RUN_USING_ENCODER  modes.
        PIDCoefficients pidOrig = motorExLeft.getPIDCoefficients(DcMotor.RunMode.RUN_USING_ENCODER);

        // change coefficients using methods included with DcMotorEx class.
        PIDCoefficients pidNew = new PIDCoefficients(NEW_P, NEW_I, NEW_D);
        motorExLeft.setPIDCoefficients(DcMotor.RunMode.RUN_USING_ENCODER, pidNew);

        // re-read coefficients and verify change.
        PIDCoefficients pidModified = motorExLeft.getPIDCoefficients(DcMotor.RunMode.RUN_USING_ENCODER);

        // display info to user.
        while(opModeIsActive()) {
            telemetry.addData("Runtime", "%.03f", getRuntime());
            telemetry.addData("P,I,D (orig)", "%.04f, %.04f, %.0f",
                    pidOrig.p, pidOrig.i, pidOrig.d);
            telemetry.addData("P,I,D (modified)", "%.04f, %.04f, %.04f",
                    pidModified.p, pidModified.i, pidModified.d);
            telemetry.update();
        }
    }
}

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FTC SDK API > com.qualcomm.robotcore.hardware.configuration > ExpansionHubMotorControllerVelocityParams

FTC SDK API·BSD 3-Clause

When ExpansionHubMotorControllerVelocityParams annotations are placed on a motor type, the indicated PID coefficients are automatically initialized when instances of that motor are used.

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MAXMotion Velocity Control | REVLib

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Open REV Robotics Docs

Velocity Control Mode | REVLib

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Open REV Robotics Docs

Tuning Methods of a PID Controller

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