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/****************************************************************************
*
* Copyright (c) 2013 PX4 Development Team. 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 PX4 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_fw_att_control_vector.cpp
*
* Fixed wing attitude controller
*
* @author Lorenz Meier <lm@inf.ethz.ch>
* @author Tobias Naegeli <naegelit@student.ethz.ch>
*
*/
#include <mathlib/mathlib.h>
#include <systemlib/geo/geo.h>
#include "ecl_fw_att_control_vector.h"
ECL_FWAttControlVector::ECL_FWAttControlVector() :
_integral_error(0.0f, 0.0f),
_integral_max(1000.0f, 1000.0f),
_rates_demanded(0.0f, 0.0f, 0.0f),
_k_p(1.0f, 1.0f, 1.0f),
_k_d(1.0f, 1.0f, 1.0f),
_k_i(1.0f, 1.0f, 1.0f),
_integral_lock(false),
_p_airspeed_min(12.0f),
_p_airspeed_max(24.0f),
_p_tconst(0.1f),
_p_roll_ffd(1.0f),
_airspeed_enabled(false)
{
}
/**
*
* @param F_des_in Desired force vector in body frame (NED). Straight flight is (0 0 -1)',
* banking hard right (1 0 -1)' and pitching down (1 0 -1)'.
*/
void ECL_FWAttControlVector::control(float dt, float airspeed, float airspeed_scaling, const math::Dcm &R_nb, float roll, float pitch, float yaw, const math::Vector &F_des_in,
const math::Vector &angular_rates,
math::Vector &moment_des, float &thrust)
{
if (!isfinite(airspeed) || !airspeed_enabled()) {
// If airspeed is not available or Inf/NaN, use the center
// of min / max
airspeed = 0.5f * (_p_airspeed_min + _p_airspeed_max);
}
math::Dcm R_bn(R_nb.transpose());
math::Matrix R_yaw_bn = math::Dcm(math::EulerAngles(0.0f, 0.0f, yaw)).transpose();
// Establish actuator signs and lift compensation
float lift_sign = (R_bn(3, 3) >= 0) ? 1.0f : -1.0f;
float lift_comp = CONSTANTS_ONE_G / math::max(airspeed , float(_p_airspeed_min) * (R_nb(2,3) * R_nb(2,3)) / (R_nb(3,3) * sqrtf((R_nb(2,3) * R_nb(2,3)) + (R_nb(3,3) * R_nb(3,3)))));
//float lift_comp = fabsf((CONSTANTS_ONE_G / math::max(airspeed , float(_p_airspeed_min)) * tanf(roll) * sinf(roll))) * _p_roll_ffd;
float cy = cosf(yaw);
float sy = sinf(yaw);
//math::Matrix RYaw = math::Dcm(cy,-sy,0.0f,sy,cy,0.0f,0.0f,0.0f,1.0f);
math::Vector z_b = math::Vector3(R_bn(0,2), R_bn(1,2), R_bn(2,2));
math::Vector3 F_des = R_yaw_bn * F_des_in;
// desired thrust in body frame
// avoid division by zero
// compensates for thrust loss due to roll/pitch
if (F_des(2) >= 0.1f) {
thrust = F_des(2) / R_bn(2, 2);
} else {
F_des(2) = 0.1f;
thrust= F_des(2) / R_bn(2, 2);
}
math::Vector3 x_B_des;
math::Vector3 y_B_des;
math::Vector3 z_B_des;
// desired body z axis
z_B_des = (F_des / F_des.norm());
// desired direction in world coordinates (yaw angle)
math::Vector3 x_C(cy, sy, 0.0f);
// desired body y axis
y_B_des = z_B_des.cross(x_C) / (z_B_des.cross(x_C)).norm();
// desired body x axis
x_B_des = y_B_des.cross(z_B_des);
// desired Rotation Matrix
math::Dcm R_des(x_B_des(0), x_B_des(1), x_B_des(2),
y_B_des(0), y_B_des(1), y_B_des(2),
z_B_des(0), z_B_des(1), z_B_des(2));
// Attitude Controller
// P controller
// error rotation matrix
// operation executed in quaternion space to allow large differences
// XXX switch between operations based on difference,
// benchmark both options
math::Quaternion e_q = math::Quaternion(R_des) - math::Quaternion(R_bn);
// Renormalize
e_q = e_q / e_q.norm();
math::Matrix e_R = math::Dcm(e_q);
//small angles: math::Matrix e_R = (R_des.transpose() * R_bn - R_bn.transpose() * R_des) * 0.5f;
// error rotation vector
math::Vector e_R_v(3);
e_R_v(0) = e_R(1,2);
e_R_v(1) = e_R(0,2);
e_R_v(2) = e_R(0,1);
// attitude integral error
math::Vector intError = math::Vector3(0.0f, 0.0f, 0.0f);
if (!_integral_lock) {
if (fabsf(_integral_error(0)) < _integral_max(0)) {
_integral_error(0) = _integral_error(0) + e_R_v(0) * dt;
}
if (fabsf(_integral_error(1)) < _integral_max(1)) {
_integral_error(1) = _integral_error(1) + e_R_v(1) * dt;
}
intError(0) = _integral_error(0);
intError(1) = _integral_error(1);
intError(2) = 0.0f;
}
_rates_demanded = (e_R_v * _k_p(0) + angular_rates * _k_d(0) + intError * _k_i(0));
moment_des = _rates_demanded;
}
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