PID Class Reference

#include <pid.h>

Inheritance diagram for PID:

Classes
struct	pid_config_t

Public Types
enum	ERROR_TYPE

Public Member Functions
	PID (pid_config_t &config)
void	init (double start_pt, double set_pt) override
double	update (double sensor_val) override
double	update (double sensor_val, double v_setpt)
double	get_sensor_val () const
	gets the sensor value that we were last updated with
double	get () override
void	set_limits (double lower, double upper) override
bool	is_on_target () override
void	reset ()
double	get_error ()
double	get_output ()
double	get_target () const
void	set_target (double target)

Public Attributes
pid_config_t &	config

Detailed Description

PID Class

Defines a standard feedback loop using the constants kP, kI, kD, deadband, and on_target_time. The formula is:

out = kP*error + kI*integral(d Error) + kD*(dError/dt)

The PID object will determine it is "on target" when the error is within the deadband, for a duration of on_target_time

Author

Ryan McGee

Date

4/3/2020

Member Enumeration Documentation

ERROR_TYPE

enum PID::ERROR_TYPE

An enum to distinguish between a linear and angular caluclation of PID error.

Constructor & Destructor Documentation

PID()

PID::PID

(

pid_config_t &

config

)

Create the PID object

Parameters

config

the configuration data for this controller

Create the PID object

Member Function Documentation

get()

double PID::get ( )

overridevirtual

Gets the current PID out value, from when update() was last run

Returns

the Out value of the controller (voltage, RPM, whatever the PID controller is controlling)

Gets the current PID out value, from when update() was last run

Implements Feedback.

get_error()

double PID::get_error

(

)

Get the delta between the current sensor data and the target

Returns

the error calculated. how it is calculated depends on error_method specified in pid_config_t

Get the delta between the current sensor data and the target

get_output()

double PID::get_output

(

)

Get the output calculated from the P, I, D and Error values

Returns

the output calculated from the pid controller specified in pid_config_t

Get the delta between the current sensor data and the target

get_sensor_val()

double PID::get_sensor_val

(

)

const

gets the sensor value that we were last updated with

Returns

sensor_val

get_target()

double PID::get_target

(

)

const

Get the PID's target

Returns

the target the PID controller is trying to achieve

init()

void PID::init ( double start_pt, double set_pt )

overridevirtual

Inherited from Feedback for interoperability. Update the setpoint and reset integral accumulation

start_pt can be safely ignored in this feedback controller

Parameters

start_pt	commpletely ignored for PID. necessary to satisfy Feedback base
set_pt	sets the target of the PID controller
start_vel	completely ignored for PID. necessary to satisfy Feedback base
end_vel	sets the target end velocity of the PID controller

Implements Feedback.

is_on_target()

bool PID::is_on_target ( )

overridevirtual

Checks if the PID controller is on target.

Returns

true if the loop is within [deadband] for [on_target_time] seconds

Returns true if the loop is within [deadband] for [on_target_time] seconds

Implements Feedback.

reset()

void PID::reset

(

)

Reset the PID loop by resetting time since 0 and accumulated error.

set_limits()

void PID::set_limits ( double lower, double upper )

overridevirtual

Set the limits on the PID out. The PID out will "clip" itself to be between the limits.

Parameters

lower	the lower limit. the PID controller will never command the output go below lower
upper	the upper limit. the PID controller will never command the output go higher than upper

Set the limits on the PID out. The PID out will "clip" itself to be between the limits.

Implements Feedback.

set_target()

void PID::set_target

(

double

target

)

Set the target for the PID loop, where the robot is trying to end up

Parameters

target

the sensor reading we would like to achieve

Set the target for the PID loop, where the robot is trying to end up

update() [1/2]

double PID::update ( double sensor_val )

overridevirtual

Update the PID loop by taking the time difference from last update, and running the PID formula with the new sensor data

Parameters

sensor_val

the distance, angle, encoder position or whatever it is we are measuring

Returns

the new output. What would be returned by PID::get()

Implements Feedback.

update() [2/2]

double PID::update	(	double	sensor_val,
		double	v_setpt )

Update the PID loop by taking the time difference from last update, and running the PID formula with the new sensor data

Parameters

sensor_val	the distance, angle, encoder position or whatever it is we are measuring
v_setpt	Expected velocity setpoint, to subtract from the D term (for velocity control)

Returns

the new output. What would be returned by PID::get()

Member Data Documentation

config

pid_config_t& PID::config

configuration struct for this controller. see pid_config_t for information about what this contains

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

• pid.h
• pid.cpp