ardupilot/libraries/AP_AHRS/AP_AHRS_NavEKF.h

#pragma once

/*
   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/>.
 */

/*
 *  NavEKF based AHRS (Attitude Heading Reference System) interface for
 *  ArduPilot
 *
 */

#include <AP_HAL/AP_HAL.h>

#ifndef HAL_NAVEKF2_AVAILABLE
// only default to EK2 enabled on boards with over 1M flash
#define HAL_NAVEKF2_AVAILABLE (BOARD_FLASH_SIZE>1024)
#endif

#ifndef HAL_NAVEKF3_AVAILABLE
#define HAL_NAVEKF3_AVAILABLE 1
#endif

#define AP_AHRS_NAVEKF_AVAILABLE 1
#include "AP_AHRS.h"

#if CONFIG_HAL_BOARD == HAL_BOARD_SITL
#include <SITL/SITL.h>
#endif

#include <AP_ExternalAHRS/AP_ExternalAHRS.h>

#include <AP_NavEKF2/AP_NavEKF2.h>
#include <AP_NavEKF3/AP_NavEKF3.h>
#include <AP_NavEKF/AP_Nav_Common.h>              // definitions shared by inertial and ekf nav filters


#define AP_AHRS_NAVEKF_SETTLE_TIME_MS 20000     // time in milliseconds the ekf needs to settle after being started

class AP_AHRS_NavEKF : public AP_AHRS_DCM {
public:
    enum Flags {
        FLAG_ALWAYS_USE_EKF = 0x1,
    };

    // Constructor
    AP_AHRS_NavEKF(uint8_t flags = 0);

    // initialise
    void init(void) override;

    /* Do not allow copies */
    AP_AHRS_NavEKF(const AP_AHRS_NavEKF &other) = delete;
    AP_AHRS_NavEKF &operator=(const AP_AHRS_NavEKF&) = delete;

    // return the smoothed gyro vector corrected for drift
    const Vector3f &get_gyro(void) const override;
    const Matrix3f &get_rotation_body_to_ned(void) const override;

    // return the current drift correction integrator value
    const Vector3f &get_gyro_drift(void) const override;

    // reset the current gyro drift estimate
    //  should be called if gyro offsets are recalculated
    void reset_gyro_drift() override;

    void            update(bool skip_ins_update=false) override;
    void            reset(bool recover_eulers = false) override;

    // dead-reckoning support
    bool get_position(struct Location &loc) const override;

    // get latest altitude estimate above ground level in meters and validity flag
    bool get_hagl(float &hagl) const override WARN_IF_UNUSED;

    // status reporting of estimated error
    float           get_error_rp() const override;
    float           get_error_yaw() const override;

    // return a wind estimation vector, in m/s
    Vector3f wind_estimate() const override;

    // return an airspeed estimate if available. return true
    // if we have an estimate
    bool airspeed_estimate(float &airspeed_ret) const override;

    // return estimate of true airspeed vector in body frame in m/s
    // returns false if estimate is unavailable
    bool airspeed_vector_true(Vector3f &vec) const override;

    // true if compass is being used
    bool use_compass() override;

    // we will need to remove these to fully hide which EKF we are using
#if HAL_NAVEKF2_AVAILABLE
    NavEKF2 &get_NavEKF2(void) {
        return EKF2;
    }
    const NavEKF2 &get_NavEKF2_const(void) const {
        return EKF2;
    }
#endif

#if HAL_NAVEKF3_AVAILABLE
    NavEKF3 &get_NavEKF3(void) {
        return EKF3;
    }
    const NavEKF3 &get_NavEKF3_const(void) const {
        return EKF3;
    }
#endif

    // return the quaternion defining the rotation from NED to XYZ (body) axes
    bool get_quaternion(Quaternion &quat) const override WARN_IF_UNUSED;

    // return secondary attitude solution if available, as eulers in radians
    bool get_secondary_attitude(Vector3f &eulers) const override;

    // return secondary attitude solution if available, as quaternion
    bool get_secondary_quaternion(Quaternion &quat) const override;

    // return secondary position solution if available
    bool get_secondary_position(struct Location &loc) const override;

    // EKF has a better ground speed vector estimate
    Vector2f groundspeed_vector() override;

    const Vector3f &get_accel_ef(uint8_t i) const override;
    const Vector3f &get_accel_ef() const override;

    // Retrieves the corrected NED delta velocity in use by the inertial navigation
    void getCorrectedDeltaVelocityNED(Vector3f& ret, float& dt) const override;

    // blended accelerometer values in the earth frame in m/s/s
    const Vector3f &get_accel_ef_blended() const override;

    // set the EKF's origin location in 10e7 degrees.  This should only
    // be called when the EKF has no absolute position reference (i.e. GPS)
    // from which to decide the origin on its own
    bool set_origin(const Location &loc) override WARN_IF_UNUSED;

    // returns the inertial navigation origin in lat/lon/alt
    bool get_origin(Location &ret) const override WARN_IF_UNUSED;

    bool have_inertial_nav() const override;

    bool get_velocity_NED(Vector3f &vec) const override;

    // return the relative position NED to either home or origin
    // return true if the estimate is valid
    bool get_relative_position_NED_home(Vector3f &vec) const override;
    bool get_relative_position_NED_origin(Vector3f &vec) const override;

    // return the relative position NE to either home or origin
    // return true if the estimate is valid
    bool get_relative_position_NE_home(Vector2f &posNE) const override;
    bool get_relative_position_NE_origin(Vector2f &posNE) const override;

    // return the relative position down to either home or origin
    // baro will be used for the _home relative one if the EKF isn't
    void get_relative_position_D_home(float &posD) const override;
    bool get_relative_position_D_origin(float &posD) const override;

    // Get a derivative of the vertical position in m/s which is kinematically consistent with the vertical position is required by some control loops.
    // This is different to the vertical velocity from the EKF which is not always consistent with the vertical position due to the various errors that are being corrected for.
    bool get_vert_pos_rate(float &velocity) const;

    // write optical flow measurements to EKF
    void writeOptFlowMeas(const uint8_t rawFlowQuality, const Vector2f &rawFlowRates, const Vector2f &rawGyroRates, const uint32_t msecFlowMeas, const Vector3f &posOffset);

    // write body odometry measurements to the EKF
    void writeBodyFrameOdom(float quality, const Vector3f &delPos, const Vector3f &delAng, float delTime, uint32_t timeStamp_ms, uint16_t delay_ms, const Vector3f &posOffset);

    // Writes the default equivalent airspeed and its 1-sigma uncertainty in m/s to be used in forward flight if a measured airspeed is required and not available.
    void writeDefaultAirSpeed(float airspeed, float uncertainty);

    // Write position and quaternion data from an external navigation system
    void writeExtNavData(const Vector3f &pos, const Quaternion &quat, float posErr, float angErr, uint32_t timeStamp_ms, uint16_t delay_ms, uint32_t resetTime_ms) override;

    // Write velocity data from an external navigation system
    void writeExtNavVelData(const Vector3f &vel, float err, uint32_t timeStamp_ms, uint16_t delay_ms) override;

    // get speed limit
    void getEkfControlLimits(float &ekfGndSpdLimit, float &ekfNavVelGainScaler) const;

    // is the AHRS subsystem healthy?
    bool healthy() const override;

    // returns false if we fail arming checks, in which case the buffer will be populated with a failure message
    // requires_position should be true if horizontal position configuration should be checked
    bool pre_arm_check(bool requires_position, char *failure_msg, uint8_t failure_msg_len) const override;

    // true if the AHRS has completed initialisation
    bool initialised() const override;

    // get_filter_status - returns filter status as a series of flags
    bool get_filter_status(nav_filter_status &status) const;

    // get compass offset estimates
    // true if offsets are valid
    bool getMagOffsets(uint8_t mag_idx, Vector3f &magOffsets) const;

    // check all cores providing consistent attitudes for prearm checks
    bool attitudes_consistent(char *failure_msg, const uint8_t failure_msg_len) const override;

    // return the amount of yaw angle change due to the last yaw angle reset in radians
    // returns the time of the last yaw angle reset or 0 if no reset has ever occurred
    uint32_t getLastYawResetAngle(float &yawAng) override;

    // return the amount of NE position change in meters due to the last reset
    // returns the time of the last reset or 0 if no reset has ever occurred
    uint32_t getLastPosNorthEastReset(Vector2f &pos) override;

    // return the amount of NE velocity change in meters/sec due to the last reset
    // returns the time of the last reset or 0 if no reset has ever occurred
    uint32_t getLastVelNorthEastReset(Vector2f &vel) const override;

    // return the amount of vertical position change due to the last reset in meters
    // returns the time of the last reset or 0 if no reset has ever occurred
    uint32_t getLastPosDownReset(float &posDelta) override;

    // Resets the baro so that it reads zero at the current height
    // Resets the EKF height to zero
    // Adjusts the EKf origin height so that the EKF height + origin height is the same as before
    // Returns true if the height datum reset has been performed
    // If using a range finder for height no reset is performed and it returns false
    bool resetHeightDatum() override;

    // send a EKF_STATUS_REPORT for current EKF
    void send_ekf_status_report(mavlink_channel_t chan) const;

    // get_hgt_ctrl_limit - get maximum height to be observed by the control loops in meters and a validity flag
    // this is used to limit height during optical flow navigation
    // it will return invalid when no limiting is required
    bool get_hgt_ctrl_limit(float &limit) const override;

    // Set to true if the terrain underneath is stable enough to be used as a height reference
    // this is not related to terrain following
    void set_terrain_hgt_stable(bool stable) override;

    // get_location - updates the provided location with the latest
    // calculated location including absolute altitude
    // returns true on success (i.e. the EKF knows it's latest
    // position), false on failure
    bool get_location(struct Location &loc) const;

    // return the innovations for the specified instance
    // An out of range instance (eg -1) returns data for the primary instance
    bool get_innovations(Vector3f &velInnov, Vector3f &posInnov, Vector3f &magInnov, float &tasInnov, float &yawInnov) const override;

    // returns true when the state estimates are significantly degraded by vibration
    bool is_vibration_affected() const;

    // get_variances - provides the innovations normalised using the innovation variance where a value of 0
    // indicates perfect consistency between the measurement and the EKF solution and a value of of 1 is the maximum
    // inconsistency that will be accepted by the filter
    // boolean false is returned if variances are not available
    bool get_variances(float &velVar, float &posVar, float &hgtVar, Vector3f &magVar, float &tasVar) const override;

    // get a source's velocity innovations
    // returns true on success and results are placed in innovations and variances arguments
    bool get_vel_innovations_and_variances_for_source(uint8_t source, Vector3f &innovations, Vector3f &variances) const override WARN_IF_UNUSED;

    // returns the expected NED magnetic field
    bool get_mag_field_NED(Vector3f& ret) const;

    // returns the estimated magnetic field offsets in body frame
    bool get_mag_field_correction(Vector3f &ret) const override;

    bool getGpsGlitchStatus() const;

    // return the index of the airspeed we should use for airspeed measurements
    // with multiple airspeed sensors and airspeed affinity in EKF3, it is possible to have switched
    // over to a lane not using the primary airspeed sensor, so AHRS should know which airspeed sensor
    // to use, i.e, the one being used by the primary lane. A lane switch could have happened due to an 
    // airspeed sensor fault, which makes this even more necessary
    uint8_t get_active_airspeed_index() const;

    // return the index of the primary core or -1 if no primary core selected
    int8_t get_primary_core_index() const override;

    // get the index of the current primary accelerometer sensor
    uint8_t get_primary_accel_index(void) const override;

    // get the index of the current primary gyro sensor
    uint8_t get_primary_gyro_index(void) const override;

    // see if EKF lane switching is possible to avoid EKF failsafe
    void check_lane_switch(void) override;

    // request EKF yaw reset to try and avoid the need for an EKF lane switch or failsafe
    void request_yaw_reset(void) override;

    // set position, velocity and yaw sources to either 0=primary, 1=secondary, 2=tertiary
    void set_posvelyaw_source_set(uint8_t source_set_idx) override;

    void Log_Write();

    // check whether external navigation is providing yaw.  Allows compass pre-arm checks to be bypassed
    bool is_ext_nav_used_for_yaw(void) const override;

    // set and save the ALT_M_NSE parameter value
    void set_alt_measurement_noise(float noise) override;

    // active EKF type for logging
    uint8_t get_active_AHRS_type(void) const override {
        return uint8_t(active_EKF_type());
    }

    // these are only out here so vehicles can reference them for parameters
#if HAL_NAVEKF2_AVAILABLE
    NavEKF2 EKF2;
#endif
#if HAL_NAVEKF3_AVAILABLE
    NavEKF3 EKF3;
#endif

private:
    enum class EKFType {
        NONE = 0
#if HAL_NAVEKF3_AVAILABLE
        ,THREE = 3
#endif
#if HAL_NAVEKF2_AVAILABLE
        ,TWO = 2
#endif
#if CONFIG_HAL_BOARD == HAL_BOARD_SITL
        ,SITL = 10
#endif
#if HAL_EXTERNAL_AHRS_ENABLED
        ,EXTERNAL = 11
#endif
    };
    EKFType active_EKF_type(void) const;

    // if successful returns true and sets secondary_ekf_type to None (for DCM), EKF3 or EKF3
    // returns false if no secondary (i.e. only using DCM)
    bool get_secondary_EKF_type(EKFType &secondary_ekf_type) const;

    bool always_use_EKF() const {
        return _ekf_flags & FLAG_ALWAYS_USE_EKF;
    }

#if HAL_NAVEKF2_AVAILABLE
    void update_EKF2(void);
    bool _ekf2_started;
#endif
#if HAL_NAVEKF3_AVAILABLE
    bool _ekf3_started;
    void update_EKF3(void);
#endif

    // rotation from vehicle body to NED frame
    Matrix3f _dcm_matrix;
    Vector3f _dcm_attitude;
    
    Vector3f _gyro_drift;
    Vector3f _gyro_estimate;
    Vector3f _accel_ef_ekf[INS_MAX_INSTANCES];
    Vector3f _accel_ef_ekf_blended;
    const uint16_t startup_delay_ms = 1000;
    uint32_t start_time_ms;
    uint8_t _ekf_flags; // bitmask from Flags enumeration

    EKFType ekf_type(void) const;
    void update_DCM(bool skip_ins_update);

    // get the index of the current primary IMU
    uint8_t get_primary_IMU_index(void) const;

    // avoid setting current state repeatedly across all cores on all EKFs:
    enum class TriState {
        False = 0,
        True = 1,
        UNKNOWN = 3,
    };

    TriState terrainHgtStableState = TriState::UNKNOWN;

    EKFType last_active_ekf_type;

#if CONFIG_HAL_BOARD == HAL_BOARD_SITL
    SITL::SITL *_sitl;
    uint32_t _last_body_odm_update_ms;
    void update_SITL(void);
#endif    

#if HAL_EXTERNAL_AHRS_ENABLED
    void update_external(void);
#endif    
};