com.arcrobotics.ftclib.controller

Class PIDFController

java.lang.Object

com.arcrobotics.ftclib.controller.PIDFController

Direct Known Subclasses:

PController

public class PIDFController
extends java.lang.Object

This is a PID controller (https://en.wikipedia.org/wiki/PID_controller) for your robot. Internally, it performs all the calculations for you. You need to tune your values to the appropriate amounts in order to properly utilize these calculations. The equation we will use is: u(t) = kP * e(t) + kI * int(0,t)[e(t')dt'] + kD * e'(t) + kF where e(t) = r(t) - y(t) and r(t) is the setpoint and y(t) is the measured value. If we consider e(t) the positional error, then int(0,t)[e(t')dt'] is the total error and e'(t) is the velocity error.

Constructor Summary

Constructors

Constructor and Description
PIDFController(double[] coeff) Pre-Condition: coeff is a four-element array: {kP, kI, kD, kF}
PIDFController(double[] coeff, double sp, double pv, double period) This is the full constructor for the PIDF controller.

Method Summary

Modifier and Type	Method and Description
boolean	atSetPoint() Returns true if the error is within the percentage of the total input range, determined by setTolerance(double).
double	calculate() Calculates the next output of the PIDF controller.
double	calculate(double pv) Calculates the control value, u(t).
double	calculate(double pv, double sp) Calculates the next output of the PIDF controller.
double[]	getCoefficients()
double	getPeriod()
double	getPositionError()
double	getSetPoint() Returns the current setpoint of the PIDFController.
double[]	getTolerance()
double	getVelocityError()
void	reset()
void	setSetPoint(double sp) Sets the setpoint for the PIDFController
void	setTolerance(double positionTolerance) Sets the error which is considered tolerable for use with atSetPoint().
void	setTolerance(double positionTolerance, double velocityTolerance) Sets the error which is considered tolerable for use with atSetPoint().

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

PIDFController

public PIDFController(double[] coeff)

Pre-Condition: coeff is a four-element array: {kP, kI, kD, kF}

The period is automatically set to 0.02.

PIDFController

public PIDFController(double[] coeff,
                      double sp,
                      double pv,
                      double period)

This is the full constructor for the PIDF controller. Our PIDF controller includes a feed-forward value which is useful for fighting friction and gravity. Our errorVal represents the return of e(t) and prevErrorVal is the previous error.

Parameters:

coeff - The coefficient array as specified in the pre-condition of the basic constructor.

sp - The setpoint of the pid control loop.

pv - The measured value of he pid control loop. We want sp = pv, or to the degree such that sp - pv, or e(t) < tolerance.

period - The interval of time between the iteration of the control loop.

Method Detail

reset

public void reset()

setTolerance

public void setTolerance(double positionTolerance)

Sets the error which is considered tolerable for use with atSetPoint().

Parameters:

positionTolerance - Position error which is tolerable.

setTolerance

public void setTolerance(double positionTolerance,
                         double velocityTolerance)

Sets the error which is considered tolerable for use with atSetPoint().

Parameters:

positionTolerance - Position error which is tolerable.

velocityTolerance - Velocity error which is tolerable.

getSetPoint

public double getSetPoint()

Returns the current setpoint of the PIDFController.

Returns:

The current setpoint.

setSetPoint

public void setSetPoint(double sp)

Sets the setpoint for the PIDFController

Parameters:

sp - The desired setpoint.

atSetPoint

public boolean atSetPoint()

Returns true if the error is within the percentage of the total input range, determined by setTolerance(double).

Returns:

Whether the error is within the acceptable bounds.

getPeriod

public double getPeriod()

Returns:

the period of time between the interval

getCoefficients

public double[] getCoefficients()

Returns:

the PIDF coefficients

getPositionError

public double getPositionError()

Returns:

the positional error e(t)

getTolerance

public double[] getTolerance()

Returns:

the tolerances of the controller

getVelocityError

public double getVelocityError()

Returns:

the velocity error e'(t)

calculate

public double calculate()

Calculates the next output of the PIDF controller.

Returns:

the next output using the current measured value via calculate(double).

calculate

public double calculate(double pv,
                        double sp)

Calculates the next output of the PIDF controller.

Parameters:

pv - The given measured value.

sp - The given setpoint.

Returns:

the next output using the given measurd value via calculate(double).

calculate

public double calculate(double pv)

Calculates the control value, u(t).

Parameters:

pv - The current measurement of the process variable.

Returns:

the value produced by u(t).