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127 lines
3.6 KiB
127 lines
3.6 KiB
/// -*- 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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namespace SITL { |
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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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} // namespace SITL |
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#endif // CONFIG_HAL_BOARD
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