Problem With Talon SRX PID Control

Technical Programming
1

Hey CD,
Right now I’m working on a PID control using the TalonSRX built in closed loop controls and nothing is working.
I try to use the Speed control mode (TalonControlMode.Speed), I set everything just as they did in the examples that CTRE provided and either nothing is happening or it goes full speed even though I try and set it to 30 RPM.
Using the SRX Magnetic Encoder

Here is the code:


package org.usfirst.frc.team5951.robot;

import com.ctre.CANTalon;
import com.ctre.CANTalon.FeedbackDevice;
import com.ctre.CANTalon.TalonControlMode;

import edu.wpi.first.wpilibj.IterativeRobot;
import edu.wpi.first.wpilibj.XboxController;
import edu.wpi.first.wpilibj.smartdashboard.SmartDashboard;

/**
 * The VM is configured to automatically run this class, and to call the
 * functions corresponding to each mode, as described in the IterativeRobot
 * documentation. If you change the name of this class or the package after
 * creating this project, you must also update the manifest file in the resource
 * directory.
 */
public class Robot extends IterativeRobot {

	private CANTalon flywheelMotor;
	private XboxController controller;
	
	/**
	 * This function is run when the robot is first started up and should be
	 * used for any initialization code.
	 */
	@Override
	public void robotInit() {
		this.flywheelMotor = new CANTalon(8);
		this.flywheelMotor.changeControlMode(TalonControlMode.Speed);
        this.flywheelMotor.setFeedbackDevice(FeedbackDevice.CtreMagEncoder_Relative);
        this.flywheelMotor.reverseSensor(true);
        this.flywheelMotor.setInverted(true);
        this.flywheelMotor.configNominalOutputVoltage(0.0f, -0.0f);
        this.flywheelMotor.configPeakOutputVoltage(+12.0f, -12.0f);
        this.flywheelMotor.setPosition(0);
        this.flywheelMotor.setProfile(0);
        this.flywheelMotor.setF(0);
        this.flywheelMotor.setP(0.2);
        this.flywheelMotor.setI(0.00);
		
		this.controller = new XboxController(0);
	}

	/**
	 * This autonomous (along with the chooser code above) shows how to select
	 * between different autonomous modes using the dashboard. The sendable
	 * chooser code works with the Java SmartDashboard. If you prefer the
	 * LabVIEW Dashboard, remove all of the chooser code and uncomment the
	 * getString line to get the auto name from the text box below the Gyro
	 *
	 * You can add additional auto modes by adding additional comparisons to the
	 * switch structure below with additional strings. If using the
	 * SendableChooser make sure to add them to the chooser code above as well.
	 */
	@Override
	public void autonomousInit() {
	}

	/**
	 * This function is called periodically during autonomous
	 */
	@Override
	public void autonomousPeriodic() {
	}

	/**
	 * This function is called periodically during operator control
	 */
	@Override
	public void teleopPeriodic() {
		if(this.controller.getAButton()) {
			this.flywheelMotor.set(40);
		} else if(this.controller.getYButton()) {
			this.flywheelMotor.set(0);
		}
		SmartDashboard.putNumber("Speed: ", this.flywheelMotor.getPosition());
		SmartDashboard.putNumber("Error: ", this.flywheelMotor.getError());
	}

	/**
	 * This function is called periodically during test mode
	 */
	@Override
	public void testPeriodic() {
	}
}

What am I missing?

2

The first thing I always suspect on a runaway is that the encoder is backwards or not working.
What are the outputs of your dashboard printouts (Speed and Error)? How do they change over time?

3

When something does move (and usually goes full speed), the speed goes up and the error gets negative because the error is negative.

4

Try also printing the speed. Does the speed ever reach the set point (40)? - note that you are doing a getPosition(), not a getSpeed(), even though you are logging it to the dashboard as Speed…

5

Right now I’m suspecting it’s a talon fault. The PID works on another talon, will update soon

Sent from my Redmi Note 4 using Tapatalk

6

Make sure the talons have the latest firmware installed. That often fixes problems where code works on one talon but not an another.