ardupilot/libraries/SITL/SIM_CRRCSim.cpp

/*
   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
/*
  simulator connector for ardupilot version of CRRCSim
*/

#include "SIM_CRRCSim.h"

#include <stdio.h>

#include <AP_HAL/AP_HAL.h>

extern const AP_HAL::HAL& hal;

namespace SITL {

CRRCSim::CRRCSim(const char *home_str, const char *frame_str) :
    Aircraft(home_str, frame_str),
    last_timestamp(0),
    sock(true)
{
    // try to bind to a specific port so that if we restart ArduPilot
    // CRRCSim keeps sending us packets. Not strictly necessary but
    // useful for debugging
    sock.bind("127.0.0.1", 9003);

    sock.reuseaddress();
    sock.set_blocking(false);
    heli_servos = (strstr(frame_str,"heli") != nullptr);
}

/*
  decode and send servos for heli
*/
void CRRCSim::send_servos_heli(const struct sitl_input &input)
{
    float swash1 = (input.servos[0]-1000) / 1000.0f;
    float swash2 = (input.servos[1]-1000) / 1000.0f;
    float swash3 = (input.servos[2]-1000) / 1000.0f;
    float tail_rotor = (input.servos[3]-1000) / 1000.0f;
    float rsc = (input.servos[7]-1000) / 1000.0f;

    float col_pitch = (swash1+swash2+swash3)/3.0 - 0.5f;
    float roll_rate = (swash1 - swash2)/2;
    float pitch_rate = -((swash1 + swash2)/2.0 - swash3)/2;
    float yaw_rate = -(tail_rotor - 0.5);

    servo_packet pkt;
    pkt.roll_rate  = constrain_float(roll_rate, -0.5, 0.5);
    pkt.pitch_rate = constrain_float(pitch_rate, -0.5, 0.5);
    pkt.throttle   = constrain_float(rsc, 0, 1);
    pkt.yaw_rate   = constrain_float(yaw_rate, -0.5, 0.5);
    pkt.col_pitch  = constrain_float(col_pitch, -0.5, 0.5);

    sock.sendto(&pkt, sizeof(pkt), "127.0.0.1", 9002);
}

/*
  decode and send servos for fixed wing
*/
void CRRCSim::send_servos_fixed_wing(const struct sitl_input &input)
{
    float roll_rate  = ((input.servos[0]-1000)/1000.0) - 0.5;
    float pitch_rate = ((input.servos[1]-1000)/1000.0) - 0.5;
    float yaw_rate   = ((input.servos[3]-1000)/1000.0) - 0.5;
    float throttle   = ((input.servos[2]-1000)/1000.0);

    servo_packet pkt;
    pkt.roll_rate  = constrain_float(roll_rate, -0.5, 0.5);
    pkt.pitch_rate = constrain_float(pitch_rate, -0.5, 0.5);
    pkt.throttle   = constrain_float(throttle, 0, 1);
    pkt.yaw_rate   = constrain_float(yaw_rate, -0.5, 0.5);
    pkt.col_pitch  = 0;

    sock.sendto(&pkt, sizeof(pkt), "127.0.0.1", 9002);
}

/*
  decode and send servos
*/
void CRRCSim::send_servos(const struct sitl_input &input)
{
    if (heli_servos) {
        send_servos_heli(input);
    } else {
        send_servos_fixed_wing(input);
    }
}

/*
  receive an update from the FDM
  This is a blocking function
 */
void CRRCSim::recv_fdm(const struct sitl_input &input)
{
    fdm_packet pkt;

    /*
      we re-send the servo packet every 0.1 seconds until we get a
      reply. This allows us to cope with some packet loss to the FDM
     */
    while (sock.recv(&pkt, sizeof(pkt), 100) != sizeof(pkt)) {
        send_servos(input);
    }

    accel_body = Vector3f(pkt.xAccel, pkt.yAccel, pkt.zAccel);
    gyro = Vector3f(pkt.rollRate, pkt.pitchRate, pkt.yawRate);
    velocity_ef = Vector3f(pkt.speedN, pkt.speedE, pkt.speedD);

    Location loc1, loc2;
    loc2.lat = pkt.latitude * 1.0e7;
    loc2.lng = pkt.longitude * 1.0e7;
    const Vector2f posdelta = loc1.get_distance_NE(loc2);
    position.x = posdelta.x;
    position.y = posdelta.y;
    position.z = -pkt.altitude;

    airspeed = pkt.airspeed;
    airspeed_pitot = pkt.airspeed;

    dcm.from_euler(pkt.roll, pkt.pitch, pkt.yaw);

    // auto-adjust to crrcsim frame rate
    double deltat = pkt.timestamp - last_timestamp;
    time_now_us += deltat * 1.0e6;

    if (deltat < 0.01 && deltat > 0) {
        adjust_frame_time(1.0/deltat);
    }
    last_timestamp = pkt.timestamp;
}

/*
  update the CRRCSim simulation by one time step
 */
void CRRCSim::update(const struct sitl_input &input)
{
    send_servos(input);
    recv_fdm(input);
    update_position();
    time_advance();

    // update magnetic field
    update_mag_field_bf();
}

} // namespace SITL