A basic pid class. More...

#include <PidController.hpp>

Public Member Functions
double	getCurrentCmd ()
	Return current command for this PID controller.
void	getCurrentPIDErrors (double &pe, double &ie, double &de)
	Return PID error terms for the controller.
void	getGains (double &p, double &i, double &d, double &i_max, double &i_min)
	Get PID gains for the controller.
void	initPid (double P, double I, double D, double I1, double I2)
	Initialize PID-gains and integral term limits:[iMax:iMin]-[I1:I2].
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].
void	reset ()
	Reset the state of this PID controller.
void	setCurrentCmd (double cmd)
	Set current command for this PID controller.
void	setGains (double P, double I, double D, double i_max, double i_min)
	Set PID gains for the controller.
double	updatePid (double p_error, boost::posix_time::time_duration dt)
	Update the Pid loop with nonuniform time step size.
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.
	~PidController ()
	Destructor of Pid class.
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 95 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 189 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 194 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 188 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 184 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 95 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 142 of file PidController.cpp.

Member Data Documentation

double youbot::PidController::cmd_ [private]

Command to send.

Definition at line 213 of file PidController.hpp.

double youbot::PidController::d_error_ [private]

Derivative error.

Definition at line 206 of file PidController.hpp.

double youbot::PidController::d_gain_ [private]

Derivative gain.

Definition at line 210 of file PidController.hpp.

double youbot::PidController::i_error_ [private]

Integator error.

Definition at line 207 of file PidController.hpp.

double youbot::PidController::i_gain_ [private]

Integral gain.

Definition at line 209 of file PidController.hpp.

double youbot::PidController::i_max_ [private]

Maximum allowable integral term.

Definition at line 211 of file PidController.hpp.

double youbot::PidController::i_min_ [private]

Minimum allowable integral term.

Definition at line 212 of file PidController.hpp.

double youbot::PidController::last_i_error [private]

Definition at line 214 of file PidController.hpp.

double youbot::PidController::p_error_ [private]

Position error.

Definition at line 205 of file PidController.hpp.

double youbot::PidController::p_error_last_ [private]

_Save position state for derivative state calculation.

Definition at line 204 of file PidController.hpp.

double youbot::PidController::p_gain_ [private]

Proportional gain.

Definition at line 208 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