mirror of https://github.com/ArduPilot/ardupilot
110 lines
3.9 KiB
C++
110 lines
3.9 KiB
C++
/*
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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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ROV/AUV/Submarine simulator class
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*/
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#pragma once
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#include "SIM_Aircraft.h"
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#include "SIM_Motor.h"
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#include "SIM_Frame.h"
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namespace SITL {
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/*
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a submarine simulator
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*/
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class Thruster {
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public:
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Thruster(int8_t _servo, float roll_fac, float pitch_fac, float yaw_fac, float throttle_fac, float forward_fac, float lat_fac) :
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servo(_servo)
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{
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linear = Vector3f(forward_fac, lat_fac, -throttle_fac);
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rotational = Vector3f(roll_fac, pitch_fac, yaw_fac);
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};
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int8_t servo;
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Vector3f linear;
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Vector3f rotational;
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};
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class Submarine : public Aircraft {
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public:
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Submarine(const char *frame_str);
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/* update model by one time step */
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void update(const struct sitl_input &input) override;
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/* static object creator */
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static Aircraft *create(const char *frame_str) {
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return new Submarine(frame_str);
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}
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protected:
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const float water_density = 1023.6; // (kg/m^3) At a temperature of 25 °C, salinity of 35 g/kg and 1 atm pressure
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const struct {
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float length = 0.457; // x direction (meters)
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float width = 0.338; // y direction (meters)
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float height = 0.254; // z direction (meters)
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float weight = 10.5; // (kg)
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float thrust = 51.48; // (N)
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float thruster_mount_radius = 0.25; // distance in meters from thrusters to center of mass. Used to calculate torque.
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float equivalent_sphere_radius = 0.2;
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// volume = 4.pi.r³/3
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float volume = 4 * M_PI * pow(equivalent_sphere_radius, 3) / 3;
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float density = 500;
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float mass = volume * density; // 16.75 kg
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// Moment of Inertia (I)(kg.m²) approximated with a sphere with a 25 cm radius (r) and same density as water
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// I = 2.m.r²/5
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float moment_of_inertia = 2 * (mass * pow(equivalent_sphere_radius, 2) / 5);
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// Frame drag coefficient
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const Vector3f linear_drag_coefficient = Vector3f(1.4, 1.8, 2.0);
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// Angular drag coefficient CD for a cube is 1.05. This is subject to change based on experimentation.
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const Vector3f angular_drag_coefficient = Vector3f(1.05, 1.05, 1.05);
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// Calculate equivalent sphere area for drag force
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// $ A = pi * r^2 / 4 $
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// $ V = 4 * pi * r^3 / 3 $
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// $ r ^2 = (V * 3 / 4) ^ (2/3) $
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// A = area (m^3), r = sphere radius (m)
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float equivalent_sphere_area = M_PI_4 * pow(volume * 3.0f / 4.0f, 2.0f / 3.0f);
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} frame_property;
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bool on_ground() const override;
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// calculate sea floor depth based for terrain follow
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float calculate_sea_floor_depth(const Vector3f &/*position*/);
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// calculate rotational and linear accelerations
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void calculate_forces(const struct sitl_input &input, Vector3f &rot_accel, Vector3f &body_accel);
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// calculate buoyancy
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float calculate_buoyancy_acceleration();
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// calculate drag from velocity and drag coefficient
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void calculate_drag_force(const Vector3f &velocity, const Vector3f &drag_coefficient, Vector3f &force);
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// calculate torque water resistance
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void calculate_angular_drag_torque(const Vector3f &angular_velocity, const Vector3f &drag_coefficient, Vector3f &torque);
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// calculate torque induced by buoyancy foams
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void calculate_buoyancy_torque(Vector3f &torque);
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Frame *frame;
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Thruster* thrusters;
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uint8_t n_thrusters;
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};
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}
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