mirror of https://github.com/ArduPilot/ardupilot
123 lines
3.5 KiB
C++
123 lines
3.5 KiB
C++
/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
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/*
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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/*
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balloon simulator class
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*/
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#include <AP_HAL/AP_HAL.h>
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#if CONFIG_HAL_BOARD == HAL_BOARD_SITL
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#include "SIM_Balloon.h"
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#include <stdio.h>
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/*
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constructor
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*/
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Balloon::Balloon(const char *home_str, const char *frame_str) :
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Aircraft(home_str, frame_str)
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{
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mass = 5.0f;
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}
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/*
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update the balloon simulation by one time step
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*/
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void Balloon::update(const struct sitl_input &input)
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{
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if (!released && input.servos[6] > 1800) {
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::printf("Balloon released\n");
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released = true;
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}
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if (!burst && input.servos[7] > 1800) {
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::printf("Balloon burst\n");
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burst = true;
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}
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float delta_time = frame_time_us * 1.0e-6f;
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// rotational air resistance
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Vector3f rot_accel = -gyro * radians(400) / terminal_rotation_rate;
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// update rotational rates in body frame
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gyro += rot_accel * delta_time;
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// update attitude
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dcm.rotate(gyro * delta_time);
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dcm.normalize();
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// air resistance
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Vector3f air_resistance = -velocity_ef * (GRAVITY_MSS/terminal_velocity);
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float lift_accel = 0;
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if (!burst && released) {
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float air_resistance_at_climb_rate = climb_rate * (GRAVITY_MSS/terminal_velocity);
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lift_accel = air_resistance_at_climb_rate + GRAVITY_MSS * dcm.c.z;
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}
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accel_body = Vector3f(0, 0, -lift_accel);
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Vector3f accel_earth = dcm * accel_body;
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accel_earth += Vector3f(0, 0, GRAVITY_MSS);
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accel_earth += air_resistance;
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// if we're on the ground, then our vertical acceleration is limited
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// to zero. This effectively adds the force of the ground on the aircraft
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if (on_ground(position) && accel_earth.z > 0) {
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accel_earth.z = 0;
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}
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// work out acceleration as seen by the accelerometers. It sees the kinematic
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// acceleration (ie. real movement), plus gravity
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accel_body = dcm.transposed() * (accel_earth + Vector3f(0, 0, -GRAVITY_MSS));
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// add some noise
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add_noise(velocity_ef.length() / terminal_velocity);
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// new velocity vector
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velocity_ef += accel_earth * delta_time;
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// new position vector
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Vector3f old_position = position;
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position += velocity_ef * delta_time;
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if (position.z < -burst_altitude) {
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::printf("Balloon burst at %.1f\n", -position.z);
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burst = true;
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}
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// assume zero wind for now
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airspeed = velocity_ef.length();
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// constrain height to the ground
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if (on_ground(position)) {
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if (!on_ground(old_position)) {
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printf("Hit ground at %f m/s\n", velocity_ef.z);
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velocity_ef.zero();
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// zero roll/pitch, but keep yaw
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float r, p, y;
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dcm.to_euler(&r, &p, &y);
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dcm.from_euler(0, 0, y);
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position.z = -(ground_level + frame_height - home.alt*0.01f);
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}
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}
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// update lat/lon/altitude
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update_position();
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}
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#endif // CONFIG_HAL_BOARD
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