PIDSubsystems for built-in PID control

If a mechanism uses a sensor for feedback then most often a PID controller will be used to control the motor speed or position. Examples of subsystems that might use PID control are: elevators with potentiometers to track the height, shooters with encoders to measure the speed, wrists with potentiometers to measure the joint angle, etc.

There is a PIDController class built into WPILib, but to simplify its use for command based programs there is a PIDSubsystem. A PIDSubsystem is a normal subsystem with the PIDController built in and exposes the required methods for operation.

A PIDSubsystem to control the angle of a wrist joint

In this example you can see the basic elements of a PIDSubsystem for the wrist joint:

package org.usfirst.frc.team1.robot.subsystems; import edu.wpi.first.wpilibj.*; import edu.wpi.first.wpilibj.command.PIDSubsystem; import org.usfirst.frc.team1.robot.RobotMap; public class Wrist extends PIDSubsystem { // This system extends PIDSubsystem Victor motor = RobotMap.wristMotor; AnalogInput pot = RobotMap.wristPot(); public Wrist() { super("Wrist", 2.0, 0.0, 0.0);// The constructor passes a name for the subsystem and the P, I and D constants that are sueed when computing the motor output setAbsoluteTolerance(0.05); getPIDController().setContinuous(false); } public void initDefaultCommand() { } protected double returnPIDInput() { return pot.getAverageVoltage(); // returns the sensor value that is providing the feedback for the system } protected void usePIDOutput(double output) { motor.pidWrite(output); // this is where the computed output value fromthe PIDController is applied to the motor } }

0 Report Errors

Use this form to report any errors with the documentation. For help with WPILib, please use the FIRST Forums at For reporting WPILib bugs, please submit an issue on GitHub at