ardupilot/ArduCopter/control_circle.pde

/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-

/*
 * control_circle.pde - init and run calls for circle flight mode
 */

// circle_init - initialise circle controller
static bool circle_init(bool ignore_checks)
{
    if ((GPS_ok() && inertial_nav.position_ok()) || ignore_checks) {
        circle_pilot_yaw_override = false;
        circle_nav.init_center();
        return true;
    }else{
        return false;
    }
}

// circle_run - runs the circle flight mode
// should be called at 100hz or more
static void circle_run()
{
    float target_yaw_rate = 0;
    float target_climb_rate = 0;

    // if not auto armed set throttle to zero and exit immediately
    if(!ap.auto_armed || ap.land_complete) {
        wp_nav.init_loiter_target();
        attitude_control.init_targets();
        attitude_control.set_throttle_out(0, false);
        return;
    }

    // process pilot inputs
    if (!failsafe.radio) {
        // get pilot's desired yaw rate
        target_yaw_rate = get_pilot_desired_yaw_rate(g.rc_4.control_in);
        if (target_yaw_rate != 0) {
            circle_pilot_yaw_override = true;
        }

        // get pilot desired climb rate
        target_climb_rate = get_pilot_desired_climb_rate(g.rc_3.control_in);

        // check for pilot requested take-off
        if (ap.land_complete && target_climb_rate > 0) {
            // indicate we are taking off
            set_land_complete(false);
            // clear i term when we're taking off
            set_throttle_takeoff();
        }
    }

    // run circle controller
    circle_nav.update();

    // call attitude controller
    if (circle_pilot_yaw_override) {
        attitude_control.angle_ef_roll_pitch_rate_ef_yaw(circle_nav.get_roll(), circle_nav.get_pitch(), target_yaw_rate);
    }else{
        attitude_control.angle_ef_roll_pitch_yaw(circle_nav.get_roll(), circle_nav.get_pitch(), circle_nav.get_yaw(),true);
    }

    // run altitude controller
    if (sonar_alt_health >= SONAR_ALT_HEALTH_MAX) {
        // if sonar is ok, use surface tracking
        target_climb_rate = get_throttle_surface_tracking(target_climb_rate, pos_control.get_alt_target(), G_Dt);
    }
    // update altitude target and call position controller
    pos_control.set_alt_target_from_climb_rate(target_climb_rate, G_Dt);
    pos_control.update_z_controller();
}