The simplePID class is a basic, tried and true PID controller. Only P (proportional) gains are necessary, the I (integral) and D (derivative) default to zero. The I control is computed using a first-order numerical integral of the error, the derivative is the numerical first-order derivative of the error. Due to these crude integration techniques, it is best if the control be computed fast (i.e. small dt). More...

#include <simple_pid.h>

Public Member Functions
void	clearIntegrator ()
	clearIntegrator allows you to clear the integrator, in case of integrator windup. More...

double	computePID (double desired, double current, double dt, double x_dot=INFINITY)
	computePID computes the PID control for the given error and timestep (since the last control was computed!) More...

void	setGains (double p, double i=0.0, double d=0.0, double tau=0.15)
	setgains is used to set the gains for a controller after it's been initialized. It will rewrite whatever is already there! More...

void	setLimits (double max, double min)
	setgains is used to set the gains for a controller after it's been initialized. It will rewrite whatever is already there! More...

	SimplePID ()
	SimplePID is the basic initializer;. More...

	SimplePID (double p, double i=0.0, double d=0.0, double max=DBL_MAX, double min=-DBL_MAX, double tau=0.15)
	SimplePID initializes the class. More...

Protected Member Functions
double	saturate (double val, double &min, double &max)
	saturate saturates the variable val More...

Protected Attributes
double	differentiator_
	used for noise reduced differentiation More...

double	integrator_
	the integral of p_error More...

double	kd_
	the derivative gain (zero if you don't want derivative control) More...

double	ki_
	the integral gain (zero if you don't want integral control) More...

double	kp_
	the proportional gain More...

double	last_error_
	the last p_error, for computing the derivative; More...

double	last_state_
	the last state, for computing the derivative; More...

double	max_
	Maximum Output. More...

double	min_
	Minimum Output. More...

double	tau_
	the noise reduction term for the derivative More...

Detailed Description

The simplePID class is a basic, tried and true PID controller. Only P (proportional) gains are necessary, the I (integral) and D (derivative) default to zero. The I control is computed using a first-order numerical integral of the error, the derivative is the numerical first-order derivative of the error. Due to these crude integration techniques, it is best if the control be computed fast (i.e. small dt).

Definition at line 53 of file simple_pid.h.

Constructor & Destructor Documentation

rosflight_utils::SimplePID::SimplePID ( )

SimplePID is the basic initializer;.

Definition at line 39 of file simple_pid.cpp.

rosflight_utils::SimplePID::SimplePID	(	double	p,
		double	i = `0.0`,
		double	d = `0.0`,
		double	max = `DBL_MAX`,
		double	min = `-DBL_MAX`,
		double	tau = `0.15`
	)

SimplePID initializes the class.

Parameters

p	the proportional controller gain (required)
i	the integral controller gain (defaults to zero)
d	the derivative controller gain (defaults to zero)
imin	the min value accepted in the output of the integral control
imax	the max value accepted in the output of the integral control (saturation for integrator windup)
tau	band limited differentiator to reduce noise

Definition at line 54 of file simple_pid.cpp.

Member Function Documentation

void rosflight_utils::SimplePID::clearIntegrator ( )

inline

clearIntegrator allows you to clear the integrator, in case of integrator windup.

Definition at line 102 of file simple_pid.h.

double rosflight_utils::SimplePID::computePID	(	double	desired,
		double	current,
		double	dt,
		double	x_dot = `INFINITY`
	)

computePID computes the PID control for the given error and timestep (since the last control was computed!)

Parameters

p_error	is the "position" error (or whatever variable you are controlling)
dt	is the timestep since the last control was computed.
x_dot	derivative of current state (optional)

Returns: the control command

Definition at line 66 of file simple_pid.cpp.

double rosflight_utils::SimplePID::saturate	(	double	val,
		double &	min,
		double &	max
	)

inlineprotected

saturate saturates the variable val

Parameters

val	the parameter to saturate (makes a copy)
min	the minimum value
max	the max value

Returns: the saturated (if necessary) value

Definition at line 126 of file simple_pid.h.

void rosflight_utils::SimplePID::setGains	(	double	p,
		double	i = `0.0`,
		double	d = `0.0`,
		double	tau = `0.15`
	)

setgains is used to set the gains for a controller after it's been initialized. It will rewrite whatever is already there!

Parameters

p	the proportional controller gain (required)
i	the integral controller gain (defaults to zero)
d	the derivative controller gain (defaults to zero)
tau	band limited differentiator to reduce noise

Todo:: Should we really be zeroing this while we are gain tuning?

Definition at line 144 of file simple_pid.cpp.

void rosflight_utils::SimplePID::setLimits	(	double	max,
		double	min
	)

setgains is used to set the gains for a controller after it's been initialized. It will rewrite whatever is already there!

Parameters

max	the largest output allowed (integrator anti-windup will kick in at this value as well)
min	the smallest output allowed (also activates integrator anti-windup

Member Data Documentation

double rosflight_utils::SimplePID::differentiator_

protected

used for noise reduced differentiation

Definition at line 112 of file simple_pid.h.

double rosflight_utils::SimplePID::integrator_

protected

the integral of p_error

Definition at line 111 of file simple_pid.h.

double rosflight_utils::SimplePID::kd_

protected

the derivative gain (zero if you don't want derivative control)

Definition at line 110 of file simple_pid.h.

double rosflight_utils::SimplePID::ki_

protected

the integral gain (zero if you don't want integral control)

Definition at line 109 of file simple_pid.h.

double rosflight_utils::SimplePID::kp_

protected

the proportional gain

Definition at line 108 of file simple_pid.h.

double rosflight_utils::SimplePID::last_error_

protected

the last p_error, for computing the derivative;

Definition at line 113 of file simple_pid.h.

double rosflight_utils::SimplePID::last_state_

protected

the last state, for computing the derivative;

Definition at line 114 of file simple_pid.h.

double rosflight_utils::SimplePID::max_

protected

Maximum Output.

Definition at line 116 of file simple_pid.h.

double rosflight_utils::SimplePID::min_

protected

Minimum Output.

Definition at line 117 of file simple_pid.h.

double rosflight_utils::SimplePID::tau_

protected

the noise reduction term for the derivative

Definition at line 115 of file simple_pid.h.

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

Public Member Functions

Protected Member Functions

Protected Attributes

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation