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Replaced member variables with constants. #44

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Feb 16, 2022
Merged

Replaced member variables with constants. #44

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15 changes: 0 additions & 15 deletions include/path_tracking_pid/controller.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -308,21 +308,6 @@ class Controller
double vel_max_external_ = INFINITY; // Dynamic external max velocity requirement (e.g. no more power available)
double vel_max_obstacle_ = INFINITY; // Can be zero if lethal obstacles are detected

// Cutoff frequency for the derivative calculation in Hz.
// Negative -> Has not been set by the user yet, so use a default.
double cutoff_frequency_lat_ = -1.0;
double cutoff_frequency_ang_ = -1.0;

// Upper and lower saturation limits
double upper_limit_ = 100.0;
double lower_limit_ = -100.0;

double ang_upper_limit_ = 100.0;
double ang_lower_limit_ = -100.0;

// Anti-windup term. Limits the absolute value of the integral term.
double windup_limit_ = 1000.0;

// Used in filter calculations. Default 1.0 corresponds to a cutoff frequency at
// 1/4 of the sample rate.
double c_lat_ = 1.;
Expand Down
61 changes: 38 additions & 23 deletions src/controller.cpp
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Expand Up @@ -20,6 +20,21 @@ namespace {
constexpr double RADIUS_EPS = 0.001; // Smallest relevant radius [m]
constexpr double LONG_DURATION = 31556926; // A year (ros::Duration cannot be inf)

// Cutoff frequency for the derivative calculation in Hz.
constexpr double cutoff_frequency_lat = -1.0;
constexpr double cutoff_frequency_ang = -1.0;

// Upper and lower saturation limits
constexpr double lat_upper_limit = 100.0;
constexpr double lat_lower_limit = -100.0;

constexpr double ang_upper_limit = 100.0;
constexpr double ang_lower_limit = -100.0;

// Anti-windup term. Limits the absolute value of the integral term.
constexpr double windup_limit = 1000.0;


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// Typesafe sign implementation with signum:
// https://stackoverflow.com/a/4609795
template <typename T> int sign(T val) {
Expand Down Expand Up @@ -501,20 +516,20 @@ geometry_msgs::Twist Controller::update(const double target_x_vel,
controller_state_.error_integral_ang += controller_state_.error_ang.at(0) * dt.toSec();

// Apply windup limit to limit the size of the integral term
if (controller_state_.error_integral_lat > std::abs(windup_limit_))
controller_state_.error_integral_lat = std::abs(windup_limit_);
if (controller_state_.error_integral_lat < -std::abs(windup_limit_))
controller_state_.error_integral_lat = -std::abs(windup_limit_);
if (controller_state_.error_integral_ang > std::abs(windup_limit_))
controller_state_.error_integral_ang = std::abs(windup_limit_);
if (controller_state_.error_integral_ang < -std::abs(windup_limit_))
controller_state_.error_integral_ang = -std::abs(windup_limit_);
if (controller_state_.error_integral_lat > std::abs(windup_limit))
controller_state_.error_integral_lat = std::abs(windup_limit);
if (controller_state_.error_integral_lat < -std::abs(windup_limit))
controller_state_.error_integral_lat = -std::abs(windup_limit);
if (controller_state_.error_integral_ang > std::abs(windup_limit))
controller_state_.error_integral_ang = std::abs(windup_limit);
if (controller_state_.error_integral_ang < -std::abs(windup_limit))
controller_state_.error_integral_ang = -std::abs(windup_limit);

// My filter reference was Julius O. Smith III, Intro. to Digital Filters With Audio Applications.
if (cutoff_frequency_lat_ != -1)
if (cutoff_frequency_lat != -1)
{
// Check if tan(_) is really small, could cause c = NaN
auto tan_filt = tan((cutoff_frequency_lat_ * 6.2832) * dt.toSec() / 2);
auto tan_filt = tan((cutoff_frequency_lat * 6.2832) * dt.toSec() / 2);

// Avoid tan(0) ==> NaN
if ((tan_filt <= 0.) && (tan_filt > -0.01))
Expand All @@ -524,10 +539,10 @@ geometry_msgs::Twist Controller::update(const double target_x_vel,

c_lat_ = 1 / tan_filt;
}
if (cutoff_frequency_ang_ != -1)
if (cutoff_frequency_ang != -1)
{
// Check if tan(_) is really small, could cause c = NaN
auto tan_filt = tan((cutoff_frequency_ang_ * 6.2832) * dt.toSec() / 2);
auto tan_filt = tan((cutoff_frequency_ang * 6.2832) * dt.toSec() / 2);

// Avoid tan(0) ==> NaN
if ((tan_filt <= 0.) && (tan_filt > -0.01))
Expand Down Expand Up @@ -773,15 +788,15 @@ geometry_msgs::Twist Controller::update(const double target_x_vel,


// Apply saturation limits
if (control_effort_lat_ > upper_limit_)
control_effort_lat_ = upper_limit_;
else if (control_effort_lat_ < lower_limit_)
control_effort_lat_ = lower_limit_;
if (control_effort_lat_ > lat_upper_limit)
control_effort_lat_ = lat_upper_limit;
else if (control_effort_lat_ < lat_lower_limit)
control_effort_lat_ = lat_lower_limit;

if (control_effort_ang_ > ang_upper_limit_)
control_effort_ang_ = ang_upper_limit_;
else if (control_effort_ang_ < ang_lower_limit_)
control_effort_ang_ = ang_lower_limit_;
if (control_effort_ang_ > ang_upper_limit)
control_effort_ang_ = ang_upper_limit;
else if (control_effort_ang_ < ang_lower_limit)
control_effort_ang_ = ang_lower_limit;

// Populate debug output
// Error topic containing the 'control' error on which the PID acts
Expand Down Expand Up @@ -1130,9 +1145,9 @@ void Controller::printParameters()

ROS_INFO("Robot type (holonomic): (%i)", holonomic_robot_enable_);

ROS_INFO("Integral-windup limit: %f", windup_limit_);
ROS_INFO("Saturation limits xy: %f/%f", upper_limit_, lower_limit_);
ROS_INFO("Saturation limits ang: %f/%f", ang_upper_limit_, ang_lower_limit_);
ROS_INFO("Integral-windup limit: %f", windup_limit);
ROS_INFO("Saturation limits xy: %f/%f", lat_upper_limit, lat_lower_limit);
ROS_INFO("Saturation limits ang: %f/%f", ang_upper_limit, ang_lower_limit);
ROS_INFO("-----------------------------------------");
}

Expand Down