/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
#ifndef __AP_INERTIALNAV_H__
#define __AP_INERTIALNAV_H__
#include <AP_AHRS.h>
#include <AP_InertialSensor.h> // ArduPilot Mega IMU Library
#include <AP_Baro.h> // ArduPilot Mega Barometer Library
#include <AP_Buffer.h> // FIFO buffer library
#define AP_INTERTIALNAV_TC_XY 2.5f // default time constant for complementary filter's X & Y axis
#define AP_INTERTIALNAV_TC_Z 5.0f // default time constant for complementary filter's Z axis
// #defines to control how often historical accel based positions are saved
// so they can later be compared to laggy gps readings
#define AP_INTERTIALNAV_SAVE_POS_AFTER_ITERATIONS 10
#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
#define AP_INTERTIALNAV_GPS_TIMEOUT_MS 300 // timeout after which position error from GPS will fall to zero
/*
* AP_InertialNav is an attempt to use accelerometers to augment other sensors to improve altitud e position hold
*/
class AP_InertialNav
{
public:
// Constructor
AP_InertialNav( AP_AHRS* ahrs, AP_InertialSensor* ins, AP_Baro* baro, GPS** gps_ptr ) :
_ahrs(ahrs),
_ins(ins),
_baro(baro),
_gps_ptr(gps_ptr),
_xy_enabled(false),
_gps_last_update(0),
_gps_last_time(0),
_baro_last_update(0)
{
AP_Param::setup_object_defaults(this, var_info);
}
// Initialisation
void init();
// update - updates velocities and positions using latest info from accelerometers;
void update(float dt);
//
// XY Axis specific methods
//
// set time constant - set timeconstant used by complementary filter
void set_time_constant_xy( float time_constant_in_seconds );
// altitude_ok, position_ok - true if inertial based altitude and position can be trusted
bool position_ok() const;
// check_gps - check if new gps readings have arrived and use them to correct position estimates
void check_gps();
// correct_with_gps - modifies accelerometer offsets using gps. dt is time since last gps update
void correct_with_gps(int32_t lon, int32_t lat, float dt);
// get_position - returns current position from home in cm
Vector3f get_position() const { return _position_base + _position_correction; }
// get latitude & longitude positions
int32_t get_latitude() const;
int32_t get_longitude() const;
// set_current_position - all internal calculations are recorded as the distances from this point
void set_current_position(int32_t lon, int32_t lat);
// get latitude & longitude positions from base location (in cm)
float get_latitude_diff() const;
float get_longitude_diff() const;
// get velocity in latitude & longitude directions (in cm/s)
float get_latitude_velocity() const;
float get_longitude_velocity() const;
// get_velocity - returns current velocity in cm/s
Vector3f get_velocity() const { return _velocity; }
// set velocity in latitude & longitude directions (in cm/s)
void set_velocity_xy(float x, float y);
//
// Z Axis methods
//
// set time constant - set timeconstant used by complementary filter
void set_time_constant_z( float time_constant_in_seconds );
// altitude_ok, position_ok - true if inertial based altitude and position can be trusted
bool altitude_ok() const { return true; }
// check_baro - check if new baro readings have arrived and use them to correct vertical accelerometer offsets
void check_baro();
// correct_with_baro - modifies accelerometer offsets using barometer. dt is time since last baro reading
void correct_with_baro(float baro_alt, float dt);
// get_altitude - get latest altitude estimate in cm
float get_altitude() const { return _position_base.z + _position_correction.z; }
void set_altitude( float new_altitude);
// get_velocity_z - get latest climb rate (in cm/s)
float get_velocity_z() const { return _velocity.z; }
void set_velocity_z( float new_velocity );
// class level parameters
static const struct AP_Param::GroupInfo var_info[];
// public variables
Vector3f accel_correction_ef; // earth frame accelerometer corrections. here for logging purposes only
protected:
void update_gains(); // update_gains - update gains from time constant (given in seconds)
AP_AHRS* _ahrs; // pointer to ahrs object
AP_InertialSensor* _ins; // pointer to inertial sensor
AP_Baro* _baro; // pointer to barometer
GPS** _gps_ptr; // pointer to pointer to gps
// XY Axis specific variables
bool _xy_enabled; // xy position estimates enabled
AP_Float _time_constant_xy; // time constant for horizontal corrections
float _k1_xy; // gain for horizontal position correction
float _k2_xy; // gain for horizontal velocity correction
float _k3_xy; // gain for horizontal accelerometer offset correction
uint32_t _gps_last_update; // system time of last gps update
uint32_t _gps_last_time; // time of last gps update according to the gps itself
uint8_t _historic_xy_counter; // counter used to slow saving of position estimates for later comparison to gps
AP_BufferFloat_Size5 _hist_position_estimate_x; // buffer of historic accel based position to account for lag
AP_BufferFloat_Size5 _hist_position_estimate_y; // buffer of historic accel based position to account for lag
int32_t _base_lat; // base latitude
int32_t _base_lon; // base longitude
float _lon_to_m_scaling; // conversion of longitude to meters
// Z Axis specific variables
AP_Float _time_constant_z; // time constant for vertical corrections
float _k1_z; // gain for vertical position correction
float _k2_z; // gain for vertical velocity correction
float _k3_z; // gain for vertical accelerometer offset correction
uint32_t _baro_last_update; // time of last barometer update
AP_BufferFloat_Size15 _hist_position_estimate_z; // buffer of historic accel based altitudes to account for lag
// general variables
Vector3f _position_base; // position estimate
Vector3f _position_correction; // sum of correction to _comp_h from delayed 1st order samples
Vector3f _velocity; // latest velocity estimate (integrated from accelerometer values)
Vector3f _position_error;
};
#endif // __AP_INERTIALNAV_H__