Line data    Source code

       1             : /*
       2             :    This program is free software: you can redistribute it and/or modify
       3             :    it under the terms of the GNU General Public License as published by
       4             :    the Free Software Foundation, either version 3 of the License, or
       5             :    (at your option) any later version.
       6             : 
       7             :    This program is distributed in the hope that it will be useful,
       8             :    but WITHOUT ANY WARRANTY; without even the implied warranty of
       9             :    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      10             :    GNU General Public License for more details.
      11             : 
      12             :    You should have received a copy of the GNU General Public License
      13             :    along with this program.  If not, see <http://www.gnu.org/licenses/>.
      14             :  */
      15             : /*
      16             :   ROV/AUV/Submarine simulator class
      17             : */
      18             : 
      19             : #pragma once
      20             : 
      21             : #include "SIM_Aircraft.h"
      22             : #include "SIM_Motor.h"
      23             : #include "SIM_Frame.h"
      24             : #include <AP_InternalError/AP_InternalError.h>
      25             : 
      26             : namespace SITL {
      27             : 
      28             : /*
      29             :   a submarine simulator
      30             :  */
      31             : 
      32             : 
      33             : class Thruster {
      34             : public:
      35       30030 :     Thruster(int8_t _servo, float roll_fac, float pitch_fac, float yaw_fac, float throttle_fac, float forward_fac, float lat_fac) :
      36       30030 :         servo(_servo)
      37             :     {
      38       30030 :         linear = Vector3f(forward_fac, lat_fac, -throttle_fac);
      39       30030 :         rotational = Vector3f(roll_fac, pitch_fac, yaw_fac);
      40       30030 :     };
      41             :     int8_t servo;
      42             :     Vector3f linear;
      43             :     Vector3f rotational;
      44             : };
      45             : 
      46             : class Submarine : public Aircraft {
      47             : public:
      48             :     Submarine(const char *frame_str);
      49             : 
      50             :     /* update model by one time step */
      51             :     void update(const struct sitl_input &input) override;
      52             : 
      53             :     /* static object creator */
      54          83 :     static Aircraft *create(const char *frame_str) {
      55          83 :         return NEW_NOTHROW Submarine(frame_str);
      56             :     }
      57             : 
      58             : 
      59             : protected:
      60             :     const float water_density = 1023.6; // (kg/m^3) At a temperature of 25 °C, salinity of 35 g/kg and 1 atm pressure
      61             : 
      62             :     const struct {
      63             :         float length = 0.457; // x direction (meters)
      64             :         float width  = 0.338; // y direction (meters)
      65             :         float height = 0.254; // z direction (meters)
      66             :         float weight = 10.5;  // (kg)
      67             :         float thrust = 51.48; // (N)
      68             :         float thruster_mount_radius = 0.25; // distance in meters from thrusters to center of mass. Used to calculate torque.
      69             :         float equivalent_sphere_radius = 0.2;
      70             :         // volume = 4.pi.r³/3
      71             :         float volume = 4 * M_PI * powf(equivalent_sphere_radius, 3) / 3;
      72             :         float density = 500;
      73             :         float mass = volume * density; // 16.75 kg
      74             :         // Moment of Inertia (I)(kg.m²) approximated with a sphere with a 25 cm radius (r) and same density as water
      75             :         // I = 2.m.r²/5
      76             :         float moment_of_inertia =  2 * (mass * powf(equivalent_sphere_radius, 2) / 5);
      77             : 
      78             :         // Frame drag coefficient
      79             :         const Vector3f linear_drag_coefficient = Vector3f(1.4, 1.8, 2.0);
      80             :         // Angular drag coefficient CD for a cube is 1.05. This is subject to change based on experimentation.
      81             :         const Vector3f angular_drag_coefficient = Vector3f(1.05, 1.05, 1.05);
      82             :         // Calculate equivalent sphere area for drag force
      83             :         // $ A = pi * r^2 / 4 $
      84             :         // $ V = 4 * pi * r^3 / 3 $
      85             :         // $ r ^2 = (V * 3 / 4) ^ (2/3) $
      86             :         // A = area (m^3), r = sphere radius (m)
      87             :         float equivalent_sphere_area = M_PI_4 * powf(volume * 3.0f / 4.0f, 2.0f / 3.0f);
      88             : 
      89             :     } frame_property;
      90             : 
      91             :     bool on_ground() const override;
      92             : 
      93           0 :     float rangefinder_beam_width() const override { return 10; }
      94             : 
      95             :     float perpendicular_distance_to_rangefinder_surface() const override;
      96             : 
      97             :     // calculate sea floor depth based for terrain follow
      98             :     float calculate_sea_floor_depth(const Vector3d &/*position*/) const;
      99             :     // calculate rotational and linear accelerations
     100             :     void calculate_forces(const struct sitl_input &input, Vector3f &rot_accel, Vector3f &body_accel);
     101             :     // calculate buoyancy
     102             :     float calculate_buoyancy_acceleration();
     103             :     // calculate drag from velocity and drag coefficient
     104             :     void calculate_drag_force(const Vector3f &velocity, const Vector3f &drag_coefficient, Vector3f &force) const;
     105             :     // calculate torque water resistance
     106             :     void calculate_angular_drag_torque(const Vector3f &angular_velocity, const Vector3f &drag_coefficient, Vector3f &torque) const;
     107             :     // calculate torque induced by buoyancy foams
     108             :     void calculate_buoyancy_torque(Vector3f &torque);
     109             :     // compute and set battery usage
     110             :     void update_battery(const struct sitl_input &input) override;
     111             :     // Sub needs the sitl_input, should never use the parent's input-free version.
     112             :     // (Using it would be using the wrong battery model, but it would silently work.)
     113           0 :     void update_battery() override { INTERNAL_ERROR(AP_InternalError::error_t::flow_of_control); };
     114    40696914 :     bool battery_is_empty() { return battery_voltage < 0.5f; };
     115             : 
     116             :     Frame *frame;
     117             :     Thruster* thrusters;
     118             :     uint8_t n_thrusters;
     119             : };
     120             : }