ardupilot/libraries/AC_PrecLand/AC_PrecLand.cpp

/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
#include <AP_HAL/AP_HAL.h>
#include "AC_PrecLand.h"
#include "AC_PrecLand_Backend.h"
#include "AC_PrecLand_Companion.h"
#include "AC_PrecLand_IRLock.h"

extern const AP_HAL::HAL& hal;

const AP_Param::GroupInfo AC_PrecLand::var_info[] PROGMEM = {
    // @DisplayName: Precision Land enabled/disabled and behaviour
    // @Description: Precision Land enabled/disabled and behaviour
    // @Values: 0:Disabled, 1:Enabled Always Land, 2:Enabled Strict
    // @User: Advanced
    AP_GROUPINFO("ENABLED", 0, AC_PrecLand, _enabled, 0),

    // @Param: TYPE
    // @DisplayName: Precision Land Type
    // @Description: Precision Land Type
    // @Values: 0:None, 1:CompanionComputer, 2:IRLock
    // @User: Advanced
    AP_GROUPINFO("TYPE",    1, AC_PrecLand, _type, 0),

    // @Param: SPEED
    // @DisplayName: Precision Land horizontal speed maximum in cm/s
    // @Description: Precision Land horizontal speed maximum in cm/s
    // @Range: 0 500
    // @User: Advanced
    AP_GROUPINFO("SPEED",   2, AC_PrecLand, _speed_xy, AC_PRECLAND_SPEED_XY_DEFAULT),

    AP_GROUPEND
};

// Default constructor.
// Note that the Vector/Matrix constructors already implicitly zero
// their values.
//
AC_PrecLand::AC_PrecLand(const AP_AHRS& ahrs, const AP_InertialNav& inav,
                         AC_PI_2D& pi_precland_xy, float dt) :
    _ahrs(ahrs),
    _inav(inav),
    _pi_precland_xy(pi_precland_xy),
    _dt(dt),
    _have_estimate(false),
    _backend(NULL)
{
    // set parameters to defaults
    AP_Param::setup_object_defaults(this, var_info);

    // other initialisation
    _backend_state.healthy = false;
}


// init - perform any required initialisation of backends
void AC_PrecLand::init()
{
    // exit immediately if init has already been run
    if (_backend != NULL) {
        return;
    }

    // default health to false
    _backend = NULL;
    _backend_state.healthy = false;

    // instantiate backend based on type parameter
    switch ((enum PrecLandType)(_type.get())) {
        // no type defined
        case PRECLAND_TYPE_NONE:
        default:
            return;
        // companion computer
        case PRECLAND_TYPE_COMPANION:
            _backend = new AC_PrecLand_Companion(*this, _backend_state);
            break;
        // IR Lock
#if CONFIG_HAL_BOARD == HAL_BOARD_PX4 || CONFIG_HAL_BOARD == HAL_BOARD_VRBRAIN
        case PRECLAND_TYPE_IRLOCK:
            _backend = new AC_PrecLand_IRLock(*this, _backend_state);
            break;
#endif
    }

    // init backend
    if (_backend != NULL) {
        _backend->init();
    }
}

// update - give chance to driver to get updates from sensor
void AC_PrecLand::update(float alt_above_terrain_cm)
{
    // run backend update
    if (_backend != NULL) {
        // read from sensor
        _backend->update();

        // calculate angles to target and position estimate
        calc_angles_and_pos(alt_above_terrain_cm);
    }
}

// get_target_shift - returns 3D vector of earth-frame position adjustments to target
Vector3f AC_PrecLand::get_target_shift(const Vector3f &orig_target)
{
    Vector3f shift; // default shift initialised to zero

    // do not shift target if not enabled or no position estimate
    if (_backend == NULL || !_have_estimate) {
        return shift;
    }

    // shift is target_offset - (original target - current position)
    Vector3f curr_offset_from_target = orig_target - _inav.get_position();
    shift = _target_pos_offset - curr_offset_from_target;
    shift.z = 0.0f;

    // record we have consumed this reading (perhaps there is a cleaner way to do this using timestamps)
    _have_estimate = false;

    // return adjusted target
    return shift;
}

// calc_angles_and_pos - converts sensor's body-frame angles to earth-frame angles and position estimate
//  body-frame angles stored in _bf_angle_to_target
//  earth-frame angles stored in _ef_angle_to_target
//  position estimate is stored in _target_pos
void AC_PrecLand::calc_angles_and_pos(float alt_above_terrain_cm)
{
    // exit immediately if not enabled
    if (_backend == NULL) {
        _have_estimate = false;
    }

    // get body-frame angles to target from backend
    if (!_backend->get_angle_to_target(_bf_angle_to_target.x, _bf_angle_to_target.y)) {
        _have_estimate = false;
    }

    // subtract vehicle lean angles
    float x_rad = _bf_angle_to_target.x - _ahrs.roll;
    float y_rad = -_bf_angle_to_target.y + _ahrs.pitch;

    // rotate to earth-frame angles
    _ef_angle_to_target.x = y_rad*_ahrs.cos_yaw() - x_rad*_ahrs.sin_yaw();
    _ef_angle_to_target.y = y_rad*_ahrs.sin_yaw() + x_rad*_ahrs.cos_yaw();

    // get current altitude (constrained to no lower than 50cm)
    float alt = max(alt_above_terrain_cm, 50.0f);

    // convert earth-frame angles to earth-frame position offset
    _target_pos_offset.x = alt*tanf(_ef_angle_to_target.x);
    _target_pos_offset.y = alt*tanf(_ef_angle_to_target.y);
    _target_pos_offset.z = 0;  // not used

    _have_estimate = true;
}