A basic pid class. More...

#include <PidController.hpp>

Public Member Functions
double	getCurrentCmd ()
	Return current command for this PID controller. More...

void	getCurrentPIDErrors (double &pe, double &ie, double &de)
	Return PID error terms for the controller. More...

void	getGains (double &p, double &i, double &d, double &i_max, double &i_min)
	Get PID gains for the controller. More...

void	initPid (double P, double I, double D, double I1, double I2)
	Initialize PID-gains and integral term limits:[iMax:iMin]-[I1:I2]. More...

PidController &	operator= (const PidController &p)

	PidController (double P=0.0, double I=0.0, double D=0.0, double I1=0.0, double I2=-0.0)
	Constructor, zeros out Pid values when created and initialize Pid-gains and integral term limits:[iMax:iMin]-[I1:I2]. More...

void	reset ()
	Reset the state of this PID controller. More...

void	setCurrentCmd (double cmd)
	Set current command for this PID controller. More...

void	setGains (double P, double I, double D, double i_max, double i_min)
	Set PID gains for the controller. More...

double	updatePid (double p_error, boost::posix_time::time_duration dt)
	Update the Pid loop with nonuniform time step size. More...

double	updatePid (double error, double error_dot, boost::posix_time::time_duration dt)
	Update the Pid loop with nonuniform time step size. This update call allows the user to pass in a precomputed derivative error. More...

	~PidController ()
	Destructor of Pid class. More...

Private Attributes
double	cmd_

double	d_error_

double	d_gain_

double	i_error_

double	i_gain_

double	i_max_

double	i_min_

double	last_i_error

double	p_error_

double	p_error_last_

double	p_gain_

Detailed Description

A basic pid class.

This class implements a generic structure that can be used to create a wide range of pid controllers. It can function independently or be subclassed to provide more specific controls based on a particular control loop.

In particular, this class implements the standard pid equation:

$command = -p_{term} - i_{term} - d_{term}$

where:

$p_{term} = p_{gain} * p_{error}$
$i_{term} = i_{gain} * i_{error}$
$d_{term} = d_{gain} * d_{error}$
$i_{error} = i_{error} + p_{error} * dt$
$d_{error} = (p_{error} - p_{error last}) / dt$

given:

$p_{error} = p_{state} - p_{target}$ .

Usage

To use the Pid class, you should first call some version of init()
(in non-realtime) and then call updatePid() at every update step.
For example:

control_toolbox::Pid pid;
pid.initPid(6.0, 1.0, 2.0, 0.3, -0.3);
double position_desi_ = 0.5;
...
ros::Time last_time = ros::Time::now();
while (true) {
  ros::Time time = ros::Time::now();
  double effort = pid.updatePid(currentPosition() - position_desi_, time - last_time);
  last_time = time;
}

Definition at line 96 of file PidController.hpp.

Constructor & Destructor Documentation

youbot::PidController::PidController	(	double	P = `0.0`,
		double	I = `0.0`,
		double	D = `0.0`,
		double	I1 = `0.0`,
		double	I2 = `-0.0`
	)

Constructor, zeros out Pid values when created and initialize Pid-gains and integral term limits:[iMax:iMin]-[I1:I2].

Parameters

P	The proportional gain.
I	The integral gain.
D	The derivative gain.
I1	The integral upper limit.
I2	The integral lower limit.

Definition at line 42 of file PidController.cpp.

youbot::PidController::~PidController ( )

Destructor of Pid class.

Definition at line 53 of file PidController.cpp.

Member Function Documentation

double youbot::PidController::getCurrentCmd ( )

Return current command for this PID controller.

Definition at line 195 of file PidController.cpp.

void youbot::PidController::getCurrentPIDErrors	(	double &	pe,
		double &	ie,
		double &	de
	)

Return PID error terms for the controller.

Parameters

pe	The proportional error.
ie	The integral error.
de	The derivative error.

Definition at line 200 of file PidController.cpp.

void youbot::PidController::getGains	(	double &	p,
		double &	i,
		double &	d,
		double &	i_max,
		double &	i_min
	)

Get PID gains for the controller.

Parameters

p	The proportional gain.
i	The integral gain.
d	The derivative gain.
i_max	The max integral windup.
i_mim	The min integral windup.

Definition at line 77 of file PidController.cpp.

void youbot::PidController::initPid	(	double	P,
		double	I,
		double	D,
		double	I1,
		double	I2
	)

Initialize PID-gains and integral term limits:[iMax:iMin]-[I1:I2].

Parameters

P	The proportional gain.
I	The integral gain.
D	The derivative gain.
I1	The integral upper limit.
I2	The integral lower limit.

Definition at line 57 of file PidController.cpp.

PidController& youbot::PidController::operator= ( const PidController & p )

inline

Definition at line 189 of file PidController.hpp.

void youbot::PidController::reset ( )

Reset the state of this PID controller.

Definition at line 68 of file PidController.cpp.

void youbot::PidController::setCurrentCmd ( double cmd )

Set current command for this PID controller.

Definition at line 190 of file PidController.cpp.

void youbot::PidController::setGains	(	double	P,
		double	I,
		double	D,
		double	i_max,
		double	i_min
	)

Set PID gains for the controller.

Parameters

P	The proportional gain.
I	The integral gain.
D	The derivative gain.
i_max
i_min

Definition at line 86 of file PidController.cpp.

double youbot::PidController::updatePid	(	double	p_error,
		boost::posix_time::time_duration	dt
	)

Update the Pid loop with nonuniform time step size.

Parameters

p_error	Error since last call (p_state-p_target)
dt	Change in time since last call

Definition at line 96 of file PidController.cpp.

double youbot::PidController::updatePid	(	double	error,
		double	error_dot,
		boost::posix_time::time_duration	dt
	)

Update the Pid loop with nonuniform time step size. This update call allows the user to pass in a precomputed derivative error.

Parameters

error	Error since last call (p_state-p_target)
error_dot	d(Error)/dt since last call
dt	Change in time since last call

Definition at line 145 of file PidController.cpp.

Member Data Documentation

double youbot::PidController::cmd_

private

Command to send.

Definition at line 214 of file PidController.hpp.

double youbot::PidController::d_error_

private

Derivative error.

Definition at line 207 of file PidController.hpp.

double youbot::PidController::d_gain_

private

Derivative gain.

Definition at line 211 of file PidController.hpp.

double youbot::PidController::i_error_

private

Integator error.

Definition at line 208 of file PidController.hpp.

double youbot::PidController::i_gain_

private

Integral gain.

Definition at line 210 of file PidController.hpp.

double youbot::PidController::i_max_

private

Maximum allowable integral term.

Definition at line 212 of file PidController.hpp.

double youbot::PidController::i_min_

private

Minimum allowable integral term.

Definition at line 213 of file PidController.hpp.

double youbot::PidController::last_i_error

private

Definition at line 215 of file PidController.hpp.

double youbot::PidController::p_error_

private

Position error.

Definition at line 206 of file PidController.hpp.

double youbot::PidController::p_error_last_

private

_Save position state for derivative state calculation.

Definition at line 205 of file PidController.hpp.

double youbot::PidController::p_gain_

private

Proportional gain.

Definition at line 209 of file PidController.hpp.

The documentation for this class was generated from the following files:

Public Member Functions

Private Attributes

Detailed Description

Usage

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation