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/**
* @file ecl_yaw_controller.cpp
* Implementation of a simple orthogonal coordinated turn yaw PID controller.
*
* Authors and acknowledgements in header.
*/
#include "ecl_yaw_controller.h"
#include <stdint.h>
#include <float.h>
#include <geo/geo.h>
#include <ecl/ecl.h>
#include <mathlib/mathlib.h>
#include <systemlib/err.h>
ECL_YawController::ECL_YawController() :
_last_run(0),
_tc(0.1f),
_last_output(0.0f),
_integrator(0.0f),
_rate_error(0.0f),
_rate_setpoint(0.0f),
_bodyrate_setpoint(0.0f),
_coordinated(1.0f)
{
}
float ECL_YawController::control_attitude(float roll, float pitch,
float speed_body_u, float speed_body_w,
float roll_rate_setpoint, float pitch_rate_setpoint)
{
// static int counter = 0;
/* Calculate desired yaw rate from coordinated turn constraint / (no side forces) */
_rate_setpoint = 0.0f;
if (_coordinated > 0.1) {
float denumerator = (speed_body_u * cosf(roll) * cosf(pitch) + speed_body_w * sinf(pitch));
if(denumerator != 0.0f) { //XXX: floating point comparison
_rate_setpoint = (speed_body_w * roll_rate_setpoint + 9.81f * sinf(roll) * cosf(pitch) + speed_body_u * pitch_rate_setpoint * sinf(roll)) / denumerator;
}
// if(counter % 20 == 0) {
// warnx("denumerator: %.4f, speed_body_u: %.4f, speed_body_w: %.4f, cosf(roll): %.4f, cosf(pitch): %.4f, sinf(pitch): %.4f", (double)denumerator, (double)speed_body_u, (double)speed_body_w, (double)cosf(roll), (double)cosf(pitch), (double)sinf(pitch));
// }
}
/* limit the rate */ //XXX: move to body angluar rates
if (_max_rate > 0.01f) {
_rate_setpoint = (_rate_setpoint > _max_rate) ? _max_rate : _rate_setpoint;
_rate_setpoint = (_rate_setpoint < -_max_rate) ? -_max_rate : _rate_setpoint;
}
// counter++;
return _rate_setpoint;
}
float ECL_YawController::control_bodyrate(float roll, float pitch,
float pitch_rate, float yaw_rate,
float pitch_rate_setpoint,
float airspeed_min, float airspeed_max, float airspeed, float scaler, bool lock_integrator)
{
/* get the usual dt estimate */
uint64_t dt_micros = ecl_elapsed_time(&_last_run);
_last_run = ecl_absolute_time();
float dt = (float)dt_micros * 1e-6f;
/* lock integral for long intervals */
if (dt_micros > 500000)
lock_integrator = true;
// float k_ff = math::max((_k_p - _k_i * _tc) * _tc - _k_d, 0.0f);
float k_ff = 0;
/* input conditioning */
if (!isfinite(airspeed)) {
/* airspeed is NaN, +- INF or not available, pick center of band */
airspeed = 0.5f * (airspeed_min + airspeed_max);
} else if (airspeed < airspeed_min) {
airspeed = airspeed_min;
}
/* Transform setpoint to body angular rates */
_bodyrate_setpoint = -sinf(roll) * pitch_rate_setpoint + cosf(roll)*cosf(pitch) * _rate_setpoint; //jacobian
/* Transform estimation to body angular rates */
float yaw_bodyrate = -sinf(roll) * pitch_rate + cosf(roll)*cosf(pitch) * yaw_rate; //jacobian
/* Calculate body angular rate error */
_rate_error = _bodyrate_setpoint - yaw_bodyrate; //body angular rate error
if (!lock_integrator && _k_i > 0.0f && airspeed > 0.5f * airspeed_min) {
float id = _rate_error * dt;
/*
* anti-windup: do not allow integrator to increase if actuator is at limit
*/
if (_last_output < -1.0f) {
/* only allow motion to center: increase value */
id = math::max(id, 0.0f);
} else if (_last_output > 1.0f) {
/* only allow motion to center: decrease value */
id = math::min(id, 0.0f);
}
_integrator += id;
}
/* integrator limit */
_integrator = math::constrain(_integrator, -_integrator_max, _integrator_max);
/* Apply PI rate controller and store non-limited output */
_last_output = (_rate_error * _k_p + _integrator * _k_i + _rate_setpoint * k_ff) * scaler * scaler; //scaler is proportional to 1/airspeed
//warnx("yaw:_last_output: %.4f, _integrator: %.4f, _integrator_max: %.4f, airspeed %.4f, _k_i %.4f, _k_p: %.4f", (double)_last_output, (double)_integrator, (double)_integrator_max, (double)airspeed, (double)_k_i, (double)_k_p);
return math::constrain(_last_output, -1.0f, 1.0f);
}
void ECL_YawController::reset_integrator()
{
_integrator = 0.0f;
}