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/**
* @file ecl_roll_controller.cpp
* Implementation of a simple orthogonal roll PID controller.
*
* Authors and acknowledgements in header.
*/
#include "../ecl.h"
#include "ecl_roll_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_RollController::ECL_RollController() :
_last_run(0),
_tc(0.1f),
_k_p(0.0f),
_k_i(0.0f),
_k_d(0.0f),
_integrator_max(0.0f),
_max_rate(0.0f),
_last_output(0.0f),
_integrator(0.0f),
_rate_error(0.0f),
_rate_setpoint(0.0f),
_bodyrate_setpoint(0.0f)
{
}
float ECL_RollController::control_attitude(float roll_setpoint, float roll)
{
/* Calculate error */
float roll_error = roll_setpoint - roll;
/* Apply P controller */
_rate_setpoint = roll_error / _tc;
/* 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;
}
return _rate_setpoint;
}
float ECL_RollController::control_bodyrate(float pitch,
float roll_rate, float yaw_rate,
float yaw_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; //xxx: param
/* input conditioning */
// warnx("airspeed pre %.4f", (double)airspeed);
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 = _rate_setpoint - sinf(pitch) * yaw_rate_setpoint; //jacobian
/* Transform estimation to body angular rates */
float roll_bodyrate = roll_rate - sinf(pitch) * yaw_rate; //jacobian
/* Calculate body angular rate error */
_rate_error = _bodyrate_setpoint - roll_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 */
//xxx: until start detection is available: integral part in control signal is limited here
float integrator_constrained = math::constrain(_integrator * _k_i, -_integrator_max, _integrator_max);
//warnx("roll: _integrator: %.4f, _integrator_max: %.4f", (double)_integrator, (double)_integrator_max);
/* Apply PI rate controller and store non-limited output */
_last_output = (_rate_error * _k_p + integrator_constrained + _rate_setpoint * k_ff) * scaler * scaler; //scaler is proportional to 1/airspeed
return math::constrain(_last_output, -1.0f, 1.0f);
}
void ECL_RollController::reset_integrator()
{
_integrator = 0.0f;
}