control_toolbox::Pid Class Reference

A basic pid class. More...

#include <pid.h>

List of all members.

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.
bool init (const ros::NodeHandle &n)
 Initialize PID with the parameters in a NodeHandle namespace.
bool initParam (const std::string &prefix)
 Initialize PID with the parameters in a namespace.
void initPid (double P, double I, double D, double I1, double I2)
 Initialize PID-gains and integral term limits:[iMax:iMin]-[I1:I2].
bool initXml (TiXmlElement *config)
Pid & operator= (const Pid &p)
 Pid (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 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.
double updatePid (double p_error, ros::Duration dt)
 Update the Pid loop with nonuniform time step size.
 ~Pid ()
 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 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:

given:

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 $i_{term}$ and not the $i_{error}$

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 106 of file pid.h.

Constructor & Destructor Documentation

control_toolbox::Pid::Pid ( 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 pid.cpp.

control_toolbox::Pid::~Pid (  ) 

Destructor of Pid class.

Definition at line 52 of file pid.cpp.

Member Function Documentation

double control_toolbox::Pid::getCurrentCmd (  ) 

Return current command for this PID controller.

Definition at line 228 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 233 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_mim The min integral windup.

Definition at line 76 of file pid.cpp.

bool control_toolbox::Pid::init ( const ros::NodeHandle &  n  ) 

Initialize PID with the parameters in a NodeHandle namespace.

Parameters:
n The NodeHandle.

Definition at line 123 of file pid.cpp.

bool control_toolbox::Pid::initParam ( const std::string &  prefix  ) 

Initialize PID with the parameters in a namespace.

Parameters:
n The namespace prefix.

Definition at line 94 of file pid.cpp.

void control_toolbox::Pid::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 56 of file pid.cpp.

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

Definition at line 111 of file pid.cpp.

Pid& control_toolbox::Pid::operator= ( const Pid &  p  )  [inline]

Definition at line 213 of file pid.h.

void control_toolbox::Pid::reset (  ) 

Reset the state of this PID controller.

Definition at line 67 of file pid.cpp.

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

Set current command for this PID controller.

Definition at line 223 of file pid.cpp.

void control_toolbox::Pid::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 85 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.

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 183 of file pid.cpp.

double control_toolbox::Pid::updatePid ( double  p_error,
ros::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 140 of file pid.cpp.

Member Data Documentation

double control_toolbox::Pid::cmd_ [private]

Command to send.

Definition at line 238 of file pid.h.

double control_toolbox::Pid::d_error_ [private]

Derivative error.

Definition at line 231 of file pid.h.

double control_toolbox::Pid::d_gain_ [private]

Derivative gain.

Definition at line 235 of file pid.h.

double control_toolbox::Pid::i_error_ [private]

Integator error.

Definition at line 232 of file pid.h.

double control_toolbox::Pid::i_gain_ [private]

Integral gain.

Definition at line 234 of file pid.h.

double control_toolbox::Pid::i_max_ [private]

Maximum allowable integral term.

Definition at line 236 of file pid.h.

double control_toolbox::Pid::i_min_ [private]

Minimum allowable integral term.

Definition at line 237 of file pid.h.

double control_toolbox::Pid::p_error_ [private]

Position error.

Definition at line 230 of file pid.h.

double control_toolbox::Pid::p_error_last_ [private]

_Save position state for derivative state calculation.

Definition at line 229 of file pid.h.

double control_toolbox::Pid::p_gain_ [private]

Proportional gain.

Definition at line 233 of file pid.h.

The documentation for this class was generated from the following files:
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control_toolbox
Author(s): Melonee Wise, Sachin Chitta, John Hsu
autogenerated on Fri Jan 11 10:00:57 2013