ecl_yaw_controller.cpp
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/****************************************************************************
*
* Copyright (c) 2013-2020 Estimation and Control Library (ECL). All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name ECL nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/**
* @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 <float.h>
#include <lib/ecl/geo/geo.h>
#include <mathlib/mathlib.h>
float ECL_YawController::control_attitude(const float dt, const ECL_ControlData &ctl_data)
{
/* Do not calculate control signal with bad inputs */
if (!(PX4_ISFINITE(ctl_data.roll) &&
PX4_ISFINITE(ctl_data.pitch) &&
PX4_ISFINITE(ctl_data.roll_rate_setpoint) &&
PX4_ISFINITE(ctl_data.pitch_rate_setpoint))) {
return _rate_setpoint;
}
float constrained_roll;
bool inverted = false;
/* roll is used as feedforward term and inverted flight needs to be considered */
if (fabsf(ctl_data.roll) < math::radians(90.0f)) {
/* not inverted, but numerically still potentially close to infinity */
constrained_roll = math::constrain(ctl_data.roll, math::radians(-80.0f), math::radians(80.0f));
} else {
inverted = true;
// inverted flight, constrain on the two extremes of -pi..+pi to avoid infinity
//note: the ranges are extended by 10 deg here to avoid numeric resolution effects
if (ctl_data.roll > 0.0f) {
/* right hemisphere */
constrained_roll = math::constrain(ctl_data.roll, math::radians(100.0f), math::radians(180.0f));
} else {
/* left hemisphere */
constrained_roll = math::constrain(ctl_data.roll, math::radians(-180.0f), math::radians(-100.0f));
}
}
constrained_roll = math::constrain(constrained_roll, -fabsf(ctl_data.roll_setpoint), fabsf(ctl_data.roll_setpoint));
if (!inverted) {
/* Calculate desired yaw rate from coordinated turn constraint / (no side forces) */
_rate_setpoint = tanf(constrained_roll) * cosf(ctl_data.pitch) * CONSTANTS_ONE_G / (ctl_data.airspeed <
ctl_data.airspeed_min ? ctl_data.airspeed_min : ctl_data.airspeed);
}
if (!PX4_ISFINITE(_rate_setpoint)) {
PX4_WARN("yaw rate sepoint not finite");
_rate_setpoint = 0.0f;
}
return _rate_setpoint;
}
float ECL_YawController::control_bodyrate(const float dt, const ECL_ControlData &ctl_data)
{
/* Do not calculate control signal with bad inputs */
if (!(PX4_ISFINITE(ctl_data.roll) &&
PX4_ISFINITE(ctl_data.pitch) &&
PX4_ISFINITE(ctl_data.body_y_rate) &&
PX4_ISFINITE(ctl_data.body_z_rate) &&
PX4_ISFINITE(ctl_data.pitch_rate_setpoint) &&
PX4_ISFINITE(ctl_data.airspeed_min) &&
PX4_ISFINITE(ctl_data.airspeed_max) &&
PX4_ISFINITE(ctl_data.scaler))) {
return math::constrain(_last_output, -1.0f, 1.0f);
}
/* Calculate body angular rate error */
_rate_error = _bodyrate_setpoint - ctl_data.body_z_rate;
if (!ctl_data.lock_integrator && _k_i > 0.0f) {
/* Integral term scales with 1/IAS^2 */
float id = _rate_error * dt * ctl_data.scaler * ctl_data.scaler;
/*
* 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);
}
/* add and constrain */
_integrator = math::constrain(_integrator + id * _k_i, -_integrator_max, _integrator_max);
}
/* Apply PI rate controller and store non-limited output */
/* FF terms scales with 1/TAS and P,I with 1/IAS^2 */
_last_output = _bodyrate_setpoint * _k_ff * ctl_data.scaler +
_rate_error * _k_p * ctl_data.scaler * ctl_data.scaler
+ _integrator;
return math::constrain(_last_output, -1.0f, 1.0f);
}
float ECL_YawController::control_euler_rate(const float dt, const ECL_ControlData &ctl_data)
{
/* Transform setpoint to body angular rates (jacobian) */
_bodyrate_setpoint = -sinf(ctl_data.roll) * ctl_data.pitch_rate_setpoint +
cosf(ctl_data.roll) * cosf(ctl_data.pitch) * _rate_setpoint;
set_bodyrate_setpoint(_bodyrate_setpoint);
return control_bodyrate(dt, ctl_data);
}