ardupilot/libraries/AP_InertialSensor/AP_InertialSensor_Backend.cpp

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

#include <AP_HAL/AP_HAL.h>
#include "AP_InertialSensor.h"
#include "AP_InertialSensor_Backend.h"

AP_InertialSensor_Backend::AP_InertialSensor_Backend(AP_InertialSensor &imu) :
    _imu(imu),
    _product_id(AP_PRODUCT_ID_NONE)
{}

void AP_InertialSensor_Backend::_rotate_and_correct_accel(uint8_t instance, Vector3f &accel) 
{
    /*
      accel calibration is always done in sensor frame with this
      version of the code. That means we apply the rotation after the
      offsets and scaling.
     */

    // apply offsets
    accel -= _imu._accel_offset[instance];

    // apply scaling
    const Vector3f &accel_scale = _imu._accel_scale[instance].get();
    accel.x *= accel_scale.x;
    accel.y *= accel_scale.y;
    accel.z *= accel_scale.z;

    // rotate to body frame
    accel.rotate(_imu._board_orientation);
}

void AP_InertialSensor_Backend::_rotate_and_correct_gyro(uint8_t instance, Vector3f &gyro) 
{
    // gyro calibration is always assumed to have been done in sensor frame
    gyro -= _imu._gyro_offset[instance];
    gyro.rotate(_imu._board_orientation);
}

/*
  rotate gyro vector and add the gyro offset
 */
void AP_InertialSensor_Backend::_publish_gyro(uint8_t instance, const Vector3f &gyro)
{
    _imu._gyro[instance] = gyro;
    _imu._gyro_healthy[instance] = true;

    if (_imu._gyro_raw_sample_rates[instance] <= 0) {
        return;
    }

    // publish delta angle
    _imu._delta_angle[instance] = _imu._delta_angle_acc[instance];
    _imu._delta_angle_valid[instance] = true;
}

void AP_InertialSensor_Backend::_notify_new_gyro_raw_sample(uint8_t instance,
                                                            const Vector3f &gyro)
{
    float dt;

    if (_imu._gyro_raw_sample_rates[instance] <= 0) {
        return;
    }

    dt = 1.0f / _imu._gyro_raw_sample_rates[instance];

    // compute delta angle
    Vector3f delta_angle = (gyro + _imu._last_raw_gyro[instance]) * 0.5f * dt;

    // compute coning correction
    // see page 26 of:
    // Tian et al (2010) Three-loop Integration of GPS and Strapdown INS with Coning and Sculling Compensation
    // Available: http://www.sage.unsw.edu.au/snap/publications/tian_etal2010b.pdf
    // see also examples/coning.py
    Vector3f delta_coning = (_imu._delta_angle_acc[instance] +
                             _imu._last_delta_angle[instance] * (1.0f / 6.0f));
    delta_coning = delta_coning % delta_angle;
    delta_coning *= 0.5f;

    // integrate delta angle accumulator
    // the angles and coning corrections are accumulated separately in the
    // referenced paper, but in simulation little difference was found between
    // integrating together and integrating separately (see examples/coning.py)
    _imu._delta_angle_acc[instance] += delta_angle + delta_coning;

    // save previous delta angle for coning correction
    _imu._last_delta_angle[instance] = delta_angle;
    _imu._last_raw_gyro[instance] = gyro;
}

/*
  rotate accel vector, scale and add the accel offset
 */
void AP_InertialSensor_Backend::_publish_accel(uint8_t instance, const Vector3f &accel)
{
    _imu._accel[instance] = accel;
    _imu._accel_healthy[instance] = true;

    if (_imu._accel_raw_sample_rates[instance] <= 0) {
        return;
    }

    // publish delta velocity
    _imu._delta_velocity[instance] = _imu._delta_velocity_acc[instance];
    _imu._delta_velocity_dt[instance] = _imu._delta_velocity_acc_dt[instance];
    _imu._delta_velocity_valid[instance] = true;
}

void AP_InertialSensor_Backend::_notify_new_accel_raw_sample(uint8_t instance,
                                                             const Vector3f &accel)
{
    float dt;

    if (_imu._accel_raw_sample_rates[instance] <= 0) {
        return;
    }

    dt = 1.0f / _imu._accel_raw_sample_rates[instance];

    _imu.calc_vibration_and_clipping(instance, accel, dt);

    // delta velocity
    _imu._delta_velocity_acc[instance] += accel * dt;
    _imu._delta_velocity_acc_dt[instance] += dt;
}

void AP_InertialSensor_Backend::_set_accel_max_abs_offset(uint8_t instance,
                                                          float max_offset)
{
    _imu._accel_max_abs_offsets[instance] = max_offset;
}

void AP_InertialSensor_Backend::_set_accel_raw_sample_rate(uint8_t instance,
                                                           uint32_t rate)
{
    _imu._accel_raw_sample_rates[instance] = rate;
}

// set accelerometer error_count
void AP_InertialSensor_Backend::_set_accel_error_count(uint8_t instance, uint32_t error_count)
{
    _imu._accel_error_count[instance] = error_count;
}

void AP_InertialSensor_Backend::_set_gyro_raw_sample_rate(uint8_t instance,
                                                          uint32_t rate)
{
    _imu._gyro_raw_sample_rates[instance] = rate;
}

// set gyro error_count
void AP_InertialSensor_Backend::_set_gyro_error_count(uint8_t instance, uint32_t error_count)
{
    _imu._gyro_error_count[instance] = error_count;
}

// return the requested sample rate in Hz
uint16_t AP_InertialSensor_Backend::get_sample_rate_hz(void) const
{
    // enum can be directly cast to Hz
    return (uint16_t)_imu._sample_rate;
}

/*
  publish a temperature value for an instance
 */
void AP_InertialSensor_Backend::_publish_temperature(uint8_t instance, float temperature)
{
    _imu._temperature[instance] = temperature;
}