ardupilot/ArduCopter/control_loiter.cpp

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

#include "Copter.h"

/*
 * control_loiter.pde - init and run calls for loiter flight mode
 */

// loiter_init - initialise loiter controller
bool Copter::loiter_init(bool ignore_checks)
{
#if FRAME_CONFIG == HELI_FRAME
    // do not allow helis to enter Loiter if the Rotor Runup is not complete
    if (!ignore_checks && !motors.rotor_runup_complete()){
        return false;
    }
#endif

    if (position_ok() || ignore_checks) {

        // set target to current position
        wp_nav.init_loiter_target();

        // initialize vertical speed and acceleration
        pos_control.set_speed_z(-g.pilot_velocity_z_max, g.pilot_velocity_z_max);
        pos_control.set_accel_z(g.pilot_accel_z);

        // initialise position and desired velocity
        pos_control.set_alt_target(inertial_nav.get_altitude());
        pos_control.set_desired_velocity_z(inertial_nav.get_velocity_z());

        return true;
    }else{
        return false;
    }
}

// loiter_run - runs the loiter controller
// should be called at 100hz or more
void Copter::loiter_run()
{
    LoiterModeState loiter_state;
    float target_yaw_rate = 0.0f;
    float target_climb_rate = 0.0f;
    float takeoff_climb_rate = 0.0f;

    // initialize vertical speed and acceleration
    pos_control.set_speed_z(-g.pilot_velocity_z_max, g.pilot_velocity_z_max);
    pos_control.set_accel_z(g.pilot_accel_z);

    // process pilot inputs unless we are in radio failsafe
    if (!failsafe.radio) {
        // apply SIMPLE mode transform to pilot inputs
        update_simple_mode();

        // process pilot's roll and pitch input
        wp_nav.set_pilot_desired_acceleration(channel_roll->get_control_in(), channel_pitch->get_control_in());

        // get pilot's desired yaw rate
        target_yaw_rate = get_pilot_desired_yaw_rate(channel_yaw->get_control_in());

        // get pilot desired climb rate
        target_climb_rate = get_pilot_desired_climb_rate(channel_throttle->get_control_in());
        target_climb_rate = constrain_float(target_climb_rate, -g.pilot_velocity_z_max, g.pilot_velocity_z_max);
    } else {
        // clear out pilot desired acceleration in case radio failsafe event occurs and we do not switch to RTL for some reason
        wp_nav.clear_pilot_desired_acceleration();
    }

    // relax loiter target if we might be landed
    if (ap.land_complete_maybe) {
        wp_nav.loiter_soften_for_landing();
    }

    // Loiter State Machine Determination
    if (!motors.armed() || !motors.get_interlock()) {
        loiter_state = Loiter_MotorStopped;
    } else if (!ap.auto_armed) {
        loiter_state = Loiter_NotAutoArmed;
    } else if (takeoff_state.running || (ap.land_complete && (channel_throttle->get_control_in() > get_takeoff_trigger_throttle()))){
        loiter_state = Loiter_Takeoff;
    } else if (ap.land_complete){
        loiter_state = Loiter_Landed;
    } else {
        loiter_state = Loiter_Flying;
    }

    // Loiter State Machine
    switch (loiter_state) {

    case Loiter_MotorStopped:

        motors.set_desired_spool_state(AP_Motors::DESIRED_SHUT_DOWN);
#if FRAME_CONFIG == HELI_FRAME
        // helicopters are capable of flying even with the motor stopped, therefore we will attempt to keep flying
        // run loiter controller
        wp_nav.update_loiter(ekfGndSpdLimit, ekfNavVelGainScaler);

        // call attitude controller
        attitude_control.input_euler_angle_roll_pitch_euler_rate_yaw(wp_nav.get_roll(), wp_nav.get_pitch(), target_yaw_rate, get_smoothing_gain());

        // force descent rate and call position controller
        pos_control.set_alt_target_from_climb_rate(-abs(g.land_speed), G_Dt, false);
        pos_control.update_z_controller();
#else
        wp_nav.init_loiter_target();
        // multicopters do not stabilize roll/pitch/yaw when motors are stopped
        attitude_control.set_throttle_out_unstabilized(0,true,g.throttle_filt);
        pos_control.relax_alt_hold_controllers(get_throttle_pre_takeoff(channel_throttle->get_control_in())-motors.get_throttle_hover());
#endif
        break;

    case Loiter_NotAutoArmed:

        motors.set_desired_spool_state(AP_Motors::DESIRED_SPIN_WHEN_ARMED);
        wp_nav.init_loiter_target();
#if FRAME_CONFIG == HELI_FRAME
        // Helicopters always stabilize roll/pitch/yaw
        attitude_control.input_euler_angle_roll_pitch_euler_rate_yaw(0, 0, 0, get_smoothing_gain());
        attitude_control.set_throttle_out(0,false,g.throttle_filt);
#else
        // Multicopters do not stabilize roll/pitch/yaw when not auto-armed (i.e. on the ground, pilot has never raised throttle)
        attitude_control.set_throttle_out_unstabilized(0,true,g.throttle_filt);
#endif
        pos_control.relax_alt_hold_controllers(get_throttle_pre_takeoff(channel_throttle->get_control_in())-motors.get_throttle_hover());
        break;

    case Loiter_Takeoff:

        if (!takeoff_state.running) {
            takeoff_timer_start(constrain_float(g.pilot_takeoff_alt,0.0f,1000.0f));
            // indicate we are taking off
            set_land_complete(false);
            // clear i term when we're taking off
            set_throttle_takeoff();
        }

        // get takeoff adjusted pilot and takeoff climb rates
        takeoff_get_climb_rates(target_climb_rate, takeoff_climb_rate);

        // set motors to full range
        motors.set_desired_spool_state(AP_Motors::DESIRED_THROTTLE_UNLIMITED);

        // run loiter controller
        wp_nav.update_loiter(ekfGndSpdLimit, ekfNavVelGainScaler);

        // call attitude controller
        attitude_control.input_euler_angle_roll_pitch_euler_rate_yaw(wp_nav.get_roll(), wp_nav.get_pitch(), target_yaw_rate, get_smoothing_gain());

        // update altitude target and call position controller
        pos_control.set_alt_target_from_climb_rate_ff(target_climb_rate, G_Dt, false);
        pos_control.add_takeoff_climb_rate(takeoff_climb_rate, G_Dt);
        pos_control.update_z_controller();
        break;

    case Loiter_Landed:

        wp_nav.init_loiter_target();
        // call attitude controller
        attitude_control.input_euler_angle_roll_pitch_euler_rate_yaw(0, 0, 0, get_smoothing_gain());
        // move throttle to between minimum and non-takeoff-throttle to keep us on the ground
        attitude_control.set_throttle_out(get_throttle_pre_takeoff(channel_throttle->get_control_in()),false,g.throttle_filt);
        // if throttle zero reset attitude and exit immediately
        if (ap.throttle_zero) {
            motors.set_desired_spool_state(AP_Motors::DESIRED_SPIN_WHEN_ARMED);
        } else {
            motors.set_desired_spool_state(AP_Motors::DESIRED_THROTTLE_UNLIMITED);
        }
        pos_control.relax_alt_hold_controllers(get_throttle_pre_takeoff(channel_throttle->get_control_in())-motors.get_throttle_hover());
        break;

    case Loiter_Flying:

        // set motors to full range
        motors.set_desired_spool_state(AP_Motors::DESIRED_THROTTLE_UNLIMITED);

        // run loiter controller
        wp_nav.update_loiter(ekfGndSpdLimit, ekfNavVelGainScaler);

        // call attitude controller
        attitude_control.input_euler_angle_roll_pitch_euler_rate_yaw(wp_nav.get_roll(), wp_nav.get_pitch(), target_yaw_rate, get_smoothing_gain());

        // adjust climb rate using rangefinder
        if (rangefinder_alt_ok()) {
            // if rangefinder is ok, use surface tracking
            target_climb_rate = get_surface_tracking_climb_rate(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_ff(target_climb_rate, G_Dt, false);
        pos_control.update_z_controller();
        break;
    }
}