mirror of https://github.com/ArduPilot/ardupilot
307 lines
12 KiB
C++
307 lines
12 KiB
C++
/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
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#ifndef __AP_INERTIALNAV_H__
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#define __AP_INERTIALNAV_H__
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#include <AP_AHRS.h>
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#include <AP_InertialSensor.h> // ArduPilot Mega IMU Library
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#include <AP_Baro.h> // ArduPilot Mega Barometer Library
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#include <AP_Buffer.h> // FIFO buffer library
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#include <AP_GPS_Glitch.h> // GPS Glitch detection library
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#include <AP_Baro_Glitch.h> // Baro Glitch detection library
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#define AP_INTERTIALNAV_TC_XY 2.5f // default time constant for complementary filter's X & Y axis
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#define AP_INTERTIALNAV_TC_Z 5.0f // default time constant for complementary filter's Z axis
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// #defines to control how often historical accel based positions are saved
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// so they can later be compared to laggy gps readings
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#define AP_INTERTIALNAV_SAVE_POS_AFTER_ITERATIONS 10
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#define AP_INTERTIALNAV_GPS_LAG_IN_10HZ_INCREMENTS 4 // must not be larger than size of _hist_position_estimate_x and _hist_position_estimate_y
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#define AP_INTERTIALNAV_GPS_TIMEOUT_MS 300 // timeout after which position error from GPS will fall to zero
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/*
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* AP_InertialNav blends accelerometer data with gps and barometer data to improve altitude and position hold.
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*
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* Most of the functions have to be called at 100Hz. (see defines above)
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*
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* The accelerometer values are integrated over time to approximate velocity and position.
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* The inaccurcy of these estimates grows over time due to noisy sensor data.
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* To improve the accuracy, baro and gps readings are used:
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* An error value is calculated as the difference between the sensor's measurement and the last position estimation.
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* This value is weighted with a gain factor and incorporated into the new estimation
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*
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* Special thanks to Tony Lambregts (FAA) for advice which contributed to the development of this filter.
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*
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*/
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class AP_InertialNav
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{
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public:
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// Constructor
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AP_InertialNav(AP_AHRS &ahrs, AP_Baro &baro, GPS_Glitch& gps_glitch, Baro_Glitch &baro_glitch) :
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_ahrs(ahrs),
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_baro(baro),
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_xy_enabled(false),
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_k1_xy(0.0f),
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_k2_xy(0.0f),
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_k3_xy(0.0f),
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_gps_last_update(0),
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_gps_last_time(0),
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_historic_xy_counter(0),
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_lon_to_cm_scaling(LATLON_TO_CM),
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_k1_z(0.0f),
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_k2_z(0.0f),
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_k3_z(0.0f),
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_baro_last_update(0),
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_glitch_detector(gps_glitch),
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_baro_glitch(baro_glitch),
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_error_count(0)
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{
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AP_Param::setup_object_defaults(this, var_info);
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}
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/**
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* initializes the object.
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*/
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virtual void init();
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/**
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* update - updates velocity and position estimates using latest info from accelerometers
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* augmented with gps and baro readings
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*
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* @param dt : time since last update in seconds
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*/
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virtual void update(float dt);
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//
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// XY Axis specific methods
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//
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/**
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* position_ok - true if inertial based altitude and position can be trusted
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* @return
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*/
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virtual bool position_ok() const;
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/**
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* get_position - returns the current position relative to the home location in cm.
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*
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* @return
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*/
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virtual const Vector3f& get_position() const { return _position; }
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/**
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* get_latitude - returns the latitude of the current position estimation in 100 nano degrees (i.e. degree value multiplied by 10,000,000)
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* @return
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*/
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virtual int32_t get_latitude() const;
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/**
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* get_longitude - returns the longitude of the current position estimation in 100 nano degrees (i.e. degree value multiplied by 10,000,000)
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* @return
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*/
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virtual int32_t get_longitude() const;
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/**
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* get_latitude_diff - returns the current latitude difference from the home location.
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*
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* @return difference in 100 nano degrees (i.e. degree value multiplied by 10,000,000)
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*/
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virtual float get_latitude_diff() const;
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/**
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* get_longitude_diff - returns the current longitude difference from the home location.
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*
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* @return difference in 100 nano degrees (i.e. degree value multiplied by 10,000,000)
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*/
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virtual float get_longitude_diff() const;
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/**
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* get_velocity - returns the current velocity in cm/s
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*
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* @return velocity vector:
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* .x : latitude velocity in cm/s
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* .y : longitude velocity in cm/s
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* .z : vertical velocity in cm/s
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*/
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virtual const Vector3f& get_velocity() const { return _velocity; }
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/**
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* get_velocity_xy - returns the current horizontal velocity in cm/s
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*
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* @returns the current horizontal velocity in cm/s
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*/
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virtual float get_velocity_xy() const;
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/**
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* set_velocity_xy - overwrites the current horizontal velocity in cm/s
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*
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* @param x : latitude velocity in cm/s
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* @param y : longitude velocity in cm/s
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*/
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void set_velocity_xy(float x, float y);
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/**
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setup_home_position - reset on home position change
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*/
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void setup_home_position(void);
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//
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// Z Axis methods
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//
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/**
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* altitude_ok - returns true if inertial based altitude and position can be trusted
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* @return
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*/
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virtual bool altitude_ok() const { return true; }
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/**
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* get_altitude - get latest altitude estimate in cm above the
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* reference position
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* @return
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*/
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virtual float get_altitude() const { return _position.z; }
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/**
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* set_altitude - overwrites the current altitude value.
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*
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* @param new_altitude : altitude in cm
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*/
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void set_altitude( float new_altitude);
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/**
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* get_velocity_z - returns the current climbrate.
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*
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* @see get_velocity().z
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*
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* @return climbrate in cm/s (positive up)
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*/
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virtual float get_velocity_z() const { return _velocity.z; }
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/**
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* set_velocity_z - overwrites the current climbrate.
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*
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* @param new_velocity : climbrate in cm/s
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*/
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void set_velocity_z( float new_velocity );
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/**
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* error_count - returns number of missed updates from GPS
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*/
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uint8_t error_count() const { return _error_count; }
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/**
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* ignore_next_error - the next error (if it occurs immediately) will not be added to the error count
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*/
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void ignore_next_error() { _flags.ignore_error = 7; }
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// class level parameters
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static const struct AP_Param::GroupInfo var_info[];
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// public variables
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Vector3f accel_correction_hbf; // horizontal body frame accelerometer corrections. here for logging purposes only
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protected:
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/**
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* correct_with_gps - calculates horizontal position error using gps
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*
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* @param now : current time since boot in milliseconds
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* @param lon : longitude in 100 nano degrees (i.e. degree value multiplied by 10,000,000)
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* @param lat : latitude in 100 nano degrees (i.e. degree value multiplied by 10,000,000)
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*/
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void correct_with_gps(uint32_t now, int32_t lon, int32_t lat);
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/**
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* check_gps - checks if new gps readings have arrived and calls correct_with_gps to
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* calculate the horizontal position error
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* @see correct_with_gps(int32_t lon, int32_t lat, float dt);
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*/
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void check_gps();
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/**
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* check_baro - checks if new baro readings have arrived and calls correct_with_baro to
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* calculate the vertical position error
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*
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* @see correct_with_baro(float baro_alt, float dt);
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*/
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void check_baro();
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/**
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* correct_with_baro - calculates vertical position error using barometer.
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*
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* @param baro_alt : altitude in cm
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* @param dt : time since last baro reading in s
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*/
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void correct_with_baro(float baro_alt, float dt);
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/**
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* update gains from time constant.
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*/
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void update_gains();
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/**
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* set_position_xy - overwrites the current position relative to the home location in cm
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*
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* the home location was set with AP_InertialNav::set_home_location(int32_t, int32_t)
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*
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* @param x : relative latitude position in cm
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* @param y : relative longitude position in cm
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*/
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void set_position_xy(float x, float y);
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// structure for holding flags
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struct InertialNav_flags {
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uint8_t gps_glitching : 1; // 1 if glitch detector was previously indicating a gps glitch
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uint8_t baro_glitching : 1; // 1 if baro glitch detector was previously indicating a baro glitch
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uint8_t ignore_error : 3; // the number of iterations for which we should ignore errors
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} _flags;
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AP_AHRS &_ahrs; // reference to ahrs object
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AP_Baro &_baro; // reference to barometer
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// parameters
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AP_Float _time_constant_xy; // time constant for horizontal corrections in s
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AP_Float _time_constant_z; // time constant for vertical corrections in s
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// XY Axis specific variables
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bool _xy_enabled; // xy position estimates enabled
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float _k1_xy; // gain for horizontal position correction
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float _k2_xy; // gain for horizontal velocity correction
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float _k3_xy; // gain for horizontal accelerometer offset correction
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uint32_t _gps_last_update; // system time of last gps update in ms
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uint32_t _gps_last_time; // time of last gps update according to the gps itself in ms
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uint8_t _historic_xy_counter; // counter used to slow saving of position estimates for later comparison to gps
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AP_BufferFloat_Size5 _hist_position_estimate_x; // buffer of historic accel based position to account for gpslag
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AP_BufferFloat_Size5 _hist_position_estimate_y; // buffer of historic accel based position to account for gps lag
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float _lon_to_cm_scaling; // conversion of longitude to centimeters
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// Z Axis specific variables
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float _k1_z; // gain for vertical position correction
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float _k2_z; // gain for vertical velocity correction
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float _k3_z; // gain for vertical accelerometer offset correction
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uint32_t _baro_last_update; // time of last barometer update in ms
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AP_BufferFloat_Size15 _hist_position_estimate_z; // buffer of historic accel based altitudes to account for barometer lag
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// general variables
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Vector3f _position_base; // (uncorrected) position estimate in cm - relative to the home location (_base_lat, _base_lon, 0)
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Vector3f _position_correction; // sum of corrections to _position_base from delayed 1st order samples in cm
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Vector3f _velocity; // latest velocity estimate (integrated from accelerometer values) in cm/s
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Vector3f _position_error; // current position error in cm - is set by the check_* methods and used by update method to calculate the correction terms
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Vector3f _position; // sum(_position_base, _position_correction) - corrected position estimate in cm - relative to the home location (_base_lat, _base_lon, 0)
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// error handling
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GPS_Glitch& _glitch_detector; // GPS Glitch detector
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Baro_Glitch& _baro_glitch; // Baro glitch detector
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uint8_t _error_count; // number of missed GPS updates
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};
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#if AP_AHRS_NAVEKF_AVAILABLE
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#include "AP_InertialNav_NavEKF.h"
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#endif
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#endif // __AP_INERTIALNAV_H__
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