A basic pid class. More...

#include <pid.h>

Classes
struct	Gains
	Store gains in a struct to allow easier realtime buffer usage. More...

Public Member Functions
double	computeCommand (double error, ros::Duration dt)
	Set the PID error and compute the PID command with nonuniform time step size. The derivative error is computed from the change in the error and the timestep `dt`. More...

double	computeCommand (double error, double error_dot, ros::Duration dt)
	Set the PID error and compute the PID command with nonuniform time step size. This also allows the user to pass in a precomputed derivative error. More...

void	dynamicReconfigCallback (control_toolbox::ParametersConfig &config, uint32_t)
	Update the PID parameters from dynamics reconfigure. More...

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	getGains (double &p, double &i, double &d, double &i_max, double &i_min, bool &antiwindup)

Gains	getGains ()
	Get PID gains for the controller. More...

bool	init (const ros::NodeHandle &n, const bool quiet=false)
	Initialize PID with the parameters in a NodeHandle namespace Initializes dynamic reconfigure for PID gains. More...

void	initDynamicReconfig (ros::NodeHandle &node)
	Start the dynamic reconfigure node and load the default values. More...

bool	initParam (const std::string &prefix, const bool quiet=false)
	Initialize PID with the parameters in a namespace Initializes dynamic reconfigure for PID gains. More...

void	initPid (double p, double i, double d, double i_max, double i_min, bool antiwindup=false)
	Zeros out Pid values and initialize Pid-gains and integral term limits Does not initialize dynamic reconfigure for PID gains. More...

void	initPid (double p, double i, double d, double i_max, double i_min, const ros::NodeHandle &)
	Zeros out Pid values and initialize Pid-gains and integral term limits Initializes dynamic reconfigure for PID gains. More...

void	initPid (double p, double i, double d, double i_max, double i_min, bool antiwindup, const ros::NodeHandle &)

bool	initXml (TiXmlElement *config)
	Initialize PID with the parameters in an XML element Initializes dynamic reconfigure for PID gains. More...

Pid &	operator= (const Pid &source)
	Custom assignment operator Does not initialize dynamic reconfigure for PID gains. More...

	Pid (double p=0.0, double i=0.0, double d=0.0, double i_max=0.0, double i_min=-0.0, bool antiwindup=false)
	Constructor, zeros out Pid values when created and initialize Pid-gains and integral term limits. Does not initialize dynamic reconfigure for PID gains. More...

	Pid (const Pid &source)
	Copy constructor required for preventing mutexes from being copied. More...

void	printValues ()
	Print to console the current parameters. 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, bool antiwindup=false)
	Set PID gains for the controller. More...

void	setGains (const Gains &gains)
	Set PID gains for the controller. More...

void	updateDynamicReconfig ()
	Set Dynamic Reconfigure's gains to Pid's values. More...

void	updateDynamicReconfig (Gains gains_config)

void	updateDynamicReconfig (control_toolbox::ParametersConfig config)

ROS_DEPRECATED double	updatePid (double p_error, ros::Duration dt)
	Update the Pid loop with nonuniform time step size. More...

ROS_DEPRECATED double	updatePid (double error, double error_dot, ros::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...

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

Private Types
typedef dynamic_reconfigure::Server< control_toolbox::ParametersConfig >	DynamicReconfigServer

Private Attributes
double	cmd_

double	d_error_

bool	dynamic_reconfig_initialized_

realtime_tools::RealtimeBuffer< Gains >	gains_buffer_

double	i_error_

double	p_error_

double	p_error_last_

DynamicReconfigServer::CallbackType	param_reconfig_callback_

boost::recursive_mutex	param_reconfig_mutex_

boost::shared_ptr< DynamicReconfigServer >	param_reconfig_server_

bool	publish_state_

boost::shared_ptr< realtime_tools::RealtimePublisher< control_msgs::PidState > >	state_publisher_

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:

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

given:

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

ROS interface

Parameters

p	Proportional gain
d	Derivative gain
i	Integral gain
i_clamp	Min/max bounds for the integral windup, the clamp is applied to the $i_{term}$
publish_state	Enable publishing internal controller state on the `state` topic. May break real-time guarantees due to clock_gettime system call.

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 117 of file pid.h.

Member Typedef Documentation

typedef dynamic_reconfigure::Server<control_toolbox::ParametersConfig> control_toolbox::Pid::DynamicReconfigServer

private

Definition at line 406 of file pid.h.

Constructor & Destructor Documentation

control_toolbox::Pid::Pid	(	double	p = `0.0`,
		double	i = `0.0`,
		double	d = `0.0`,
		double	i_max = `0.0`,
		double	i_min = `-0.0`,
		bool	antiwindup = `false`
	)

Constructor, zeros out Pid values when created and initialize Pid-gains and integral term limits. Does not initialize dynamic reconfigure for PID gains.

Parameters

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

Definition at line 51 of file pid.cpp.

control_toolbox::Pid::Pid ( const Pid & source )

Copy constructor required for preventing mutexes from being copied.

Parameters

source - Pid to copy

Definition at line 59 of file pid.cpp.

control_toolbox::Pid::~Pid ( )

Destructor of Pid class.

Definition at line 69 of file pid.cpp.

Member Function Documentation

double control_toolbox::Pid::computeCommand	(	double	error,
		ros::Duration	dt
	)

Set the PID error and compute the PID command with nonuniform time step size. The derivative error is computed from the change in the error and the timestep dt.

Parameters

error	Error since last call (error = target - state)
dt	Change in time since last call

Returns: PID command

Definition at line 298 of file pid.cpp.

double control_toolbox::Pid::computeCommand	(	double	error,
		double	error_dot,
		ros::Duration	dt
	)

Set the PID error and compute the PID command with nonuniform time step size. This also allows the user to pass in a precomputed derivative error.

Parameters

error	Error since last call (error = target - state)
error_dot	d(Error)/dt since last call
dt	Change in time since last call

Returns: PID command

Definition at line 321 of file pid.cpp.

void control_toolbox::Pid::dynamicReconfigCallback	(	control_toolbox::ParametersConfig &	config,
		uint32_t
	)

Update the PID parameters from dynamics reconfigure.

Definition at line 290 of file pid.cpp.

double control_toolbox::Pid::getCurrentCmd ( )

Return current command for this PID controller.

Definition at line 396 of file pid.cpp.

void control_toolbox::Pid::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 401 of file pid.cpp.

void control_toolbox::Pid::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_min	The min integral windup.

Definition at line 206 of file pid.cpp.

void control_toolbox::Pid::getGains	(	double &	p,
		double &	i,
		double &	d,
		double &	i_max,
		double &	i_min,
		bool &	antiwindup
	)

Definition at line 212 of file pid.cpp.

Pid::Gains control_toolbox::Pid::getGains ( )

Get PID gains for the controller.

Returns: gains A struct of the PID gain values

Definition at line 224 of file pid.cpp.

bool control_toolbox::Pid::init	(	const ros::NodeHandle &	n,
		const bool	quiet = `false`
	)

Initialize PID with the parameters in a NodeHandle namespace Initializes dynamic reconfigure for PID gains.

Parameters

n	The NodeHandle which should be used to query parameters.
quiet	If true, no error messages will be emitted on failure.

Definition at line 106 of file pid.cpp.

void control_toolbox::Pid::initDynamicReconfig ( ros::NodeHandle & node )

Start the dynamic reconfigure node and load the default values.

Parameters

node	- a node handle where dynamic reconfigure services will be published

Definition at line 180 of file pid.cpp.

bool control_toolbox::Pid::initParam	(	const std::string &	prefix,
		const bool	quiet = `false`
	)

Initialize PID with the parameters in a namespace Initializes dynamic reconfigure for PID gains.

Parameters

prefix	The namespace prefix.
quiet	If true, no error messages will be emitted on failure.

Definition at line 100 of file pid.cpp.

void control_toolbox::Pid::initPid	(	double	p,
		double	i,
		double	d,
		double	i_max,
		double	i_min,
		bool	antiwindup = `false`
	)

Zeros out Pid values and initialize Pid-gains and integral term limits Does not initialize dynamic reconfigure for PID gains.

Parameters

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

Definition at line 93 of file pid.cpp.

void control_toolbox::Pid::initPid	(	double	p,
		double	i,
		double	d,
		double	i_max,
		double	i_min,
		const ros::NodeHandle &
	)

Zeros out Pid values and initialize Pid-gains and integral term limits Initializes dynamic reconfigure for PID gains.

Parameters

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

Definition at line 73 of file pid.cpp.

void control_toolbox::Pid::initPid	(	double	p,
		double	i,
		double	d,
		double	i_max,
		double	i_min,
		bool	antiwindup,
		const ros::NodeHandle &
	)

Definition at line 83 of file pid.cpp.

bool control_toolbox::Pid::initXml ( TiXmlElement * config )

Initialize PID with the parameters in an XML element Initializes dynamic reconfigure for PID gains.

Parameters

config the XML element

Definition at line 157 of file pid.cpp.

Pid& control_toolbox::Pid::operator= ( const Pid & source )

inline

Custom assignment operator Does not initialize dynamic reconfigure for PID gains.

Definition at line 375 of file pid.h.

void control_toolbox::Pid::printValues ( )

Print to console the current parameters.

Definition at line 411 of file pid.cpp.

void control_toolbox::Pid::reset ( )

Reset the state of this PID controller.

Definition at line 197 of file pid.cpp.

void control_toolbox::Pid::setCurrentCmd ( double cmd )

Set current command for this PID controller.

Definition at line 391 of file pid.cpp.

void control_toolbox::Pid::setGains	(	double	p,
		double	i,
		double	d,
		double	i_max,
		double	i_min,
		bool	antiwindup = `false`
	)

Set 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_min	The min integral windup.

Definition at line 229 of file pid.cpp.

void control_toolbox::Pid::setGains ( const Gains & gains )

Set PID gains for the controller.

Parameters

gains A struct of the PID gain values

Definition at line 236 of file pid.cpp.

void control_toolbox::Pid::updateDynamicReconfig ( )

Set Dynamic Reconfigure's gains to Pid's values.

Definition at line 244 of file pid.cpp.

void control_toolbox::Pid::updateDynamicReconfig ( Gains gains_config )

Definition at line 259 of file pid.cpp.

void control_toolbox::Pid::updateDynamicReconfig ( control_toolbox::ParametersConfig config )

Definition at line 278 of file pid.cpp.

double control_toolbox::Pid::updatePid	(	double	p_error,
		ros::Duration	dt
	)

Update the Pid loop with nonuniform time step size.

Deprecated:: in ROS Hydro. This function assumes p_error = (state - target) which is an unconventional definition of the error. Please use computeCommand instead, which assumes error = (target - state) . Note that calls to computeCommand should not be mixed with calls to updatePid.

Parameters

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

Definition at line 316 of file pid.cpp.

double control_toolbox::Pid::updatePid	(	double	error,
		double	error_dot,
		ros::Duration	dt
	)

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

Deprecated:: in ROS Hydro. This function assumes p_error = (state - target) which is an unconventional definition of the error. Please use computeCommand instead, which assumes error = (target - state) . Note that calls to computeCommand should not be mixed with calls to updatePid.

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 386 of file pid.cpp.

Member Data Documentation

double control_toolbox::Pid::cmd_

private

Command to send.

Definition at line 402 of file pid.h.

double control_toolbox::Pid::d_error_

private

Derivative of position error.

Definition at line 401 of file pid.h.

bool control_toolbox::Pid::dynamic_reconfig_initialized_

private

Definition at line 405 of file pid.h.

realtime_tools::RealtimeBuffer<Gains> control_toolbox::Pid::gains_buffer_

private

Definition at line 393 of file pid.h.

double control_toolbox::Pid::i_error_

private

Integral of position error.

Definition at line 400 of file pid.h.

double control_toolbox::Pid::p_error_

private

Position error.

Definition at line 399 of file pid.h.

double control_toolbox::Pid::p_error_last_

private

_Save position state for derivative state calculation.

Definition at line 398 of file pid.h.

DynamicReconfigServer::CallbackType control_toolbox::Pid::param_reconfig_callback_

private

Definition at line 408 of file pid.h.

boost::recursive_mutex control_toolbox::Pid::param_reconfig_mutex_

private

Definition at line 410 of file pid.h.

boost::shared_ptr<DynamicReconfigServer> control_toolbox::Pid::param_reconfig_server_

private

Definition at line 407 of file pid.h.

bool control_toolbox::Pid::publish_state_

private

Definition at line 396 of file pid.h.

boost::shared_ptr<realtime_tools::RealtimePublisher<control_msgs::PidState> > control_toolbox::Pid::state_publisher_

private

Definition at line 395 of file pid.h.

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

Classes

Public Member Functions

Private Types

Private Attributes

Detailed Description

ROS interface

Usage

Member Typedef Documentation

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation