ardupilot/libraries/AP_IMU/AP_IMU_INS.cpp

260 lines
7.1 KiB
C++

// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
//
//
// AP_IMU_INS.cpp - IMU Sensor Library for Ardupilot Mega
// Code by Michael Smith, Doug Weibel, Jordi Muñoz and Jose Julio. DIYDrones.com
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
/// @file AP_IMU_INS.cpp
/// @brief IMU driver on top of an INS driver. Provides calibration for the
// inertial sensors (gyro and accel)
#include <FastSerial.h>
#include <AP_Common.h>
#include <avr/eeprom.h>
#include "AP_IMU_INS.h"
void
AP_IMU_INS::init( Start_style style,
void (*delay_cb)(unsigned long t),
void (*flash_leds_cb)(bool on),
AP_PeriodicProcess * scheduler )
{
_product_id = _ins->init(scheduler);
// if we are warm-starting, load the calibration data from EEPROM and go
//
if (WARM_START == style) {
_sensor_cal.load();
} else {
// do cold-start calibration for both accel and gyro
_init_gyro(delay_cb, flash_leds_cb);
// save calibration
_sensor_cal.save();
}
}
/**************************************************/
void
AP_IMU_INS::init_gyro(void (*delay_cb)(unsigned long t), void (*flash_leds_cb)(bool on))
{
_init_gyro(delay_cb, flash_leds_cb);
_sensor_cal.save();
}
#define FLASH_LEDS(on) do { if (flash_leds_cb != NULL) flash_leds_cb(on); } while (0)
void
AP_IMU_INS::_init_gyro(void (*delay_cb)(unsigned long t), void (*flash_leds_cb)(bool on))
{
Vector3f last_average, best_avg;
float ins_gyro[3];
float best_diff = 0;
// cold start
delay_cb(100);
Serial.printf_P(PSTR("Init Gyro"));
for(int c = 0; c < 25; c++) {
// Mostly we are just flashing the LED's here
// to tell the user to keep the IMU still
FLASH_LEDS(true);
delay_cb(20);
_ins->update();
_ins->get_gyros(ins_gyro);
FLASH_LEDS(false);
delay_cb(20);
}
// the strategy is to average 200 points over 1 second, then do it
// again and see if the 2nd average is within a small margin of
// the first
last_average.zero();
// we try to get a good calibration estimate for up to 10 seconds
// if the gyros are stable, we should get it in 2 seconds
for (int j = 0; j <= 10; j++) {
Vector3f gyro_sum, gyro_avg, gyro_diff;
float diff_norm;
uint8_t i;
Serial.printf_P(PSTR("*"));
gyro_sum.zero();
for (i=0; i<200; i++) {
_ins->update();
_ins->get_gyros(ins_gyro);
gyro_sum += Vector3f(ins_gyro[0], ins_gyro[1], ins_gyro[2]);
if (i % 40 == 20) {
FLASH_LEDS(true);
} else if (i % 40 == 0) {
FLASH_LEDS(false);
}
delay_cb(5);
}
gyro_avg = gyro_sum / i;
gyro_diff = last_average - gyro_avg;
diff_norm = gyro_diff.length();
if (j == 0) {
best_diff = diff_norm;
best_avg = gyro_avg;
} else if (gyro_diff.length() < ToRad(0.04)) {
// we want the average to be within 0.1 bit, which is 0.04 degrees/s
last_average = (gyro_avg * 0.5) + (last_average * 0.5);
_sensor_cal[0] = last_average.x;
_sensor_cal[1] = last_average.y;
_sensor_cal[2] = last_average.z;
// all done
return;
} else if (diff_norm < best_diff) {
best_diff = diff_norm;
best_avg = (gyro_avg * 0.5) + (last_average * 0.5);
}
last_average = gyro_avg;
}
// we've kept the user waiting long enough - use the best pair we
// found so far
Serial.printf_P(PSTR("\ngyro did not converge: diff=%f dps\n"), ToDeg(best_diff));
_sensor_cal[0] = best_avg.x;
_sensor_cal[1] = best_avg.y;
_sensor_cal[2] = best_avg.z;
}
void
AP_IMU_INS::save()
{
_sensor_cal.save();
}
void
AP_IMU_INS::init_accel(void (*delay_cb)(unsigned long t), void (*flash_leds_cb)(bool on))
{
_init_accel(delay_cb, flash_leds_cb);
_sensor_cal.save();
}
void
AP_IMU_INS::_init_accel(void (*delay_cb)(unsigned long t), void (*flash_leds_cb)(bool on))
{
int flashcount = 0;
float adc_in;
float prev[6] = {0,0,0};
float total_change;
float max_offset;
float ins_accel[3];
// cold start
delay_cb(500);
Serial.printf_P(PSTR("Init Accel"));
for (int j=3; j<=5; j++) _sensor_cal[j] = 500; // Just a large value to load prev[j] the first time
do {
_ins->update();
_ins->get_accels(ins_accel);
for (int j = 3; j <= 5; j++) {
prev[j] = _sensor_cal[j];
adc_in = ins_accel[j-3];
_sensor_cal[j] = adc_in;
}
for(int i = 0; i < 50; i++) { // We take some readings...
delay_cb(20);
_ins->update();
_ins->get_accels(ins_accel);
for (int j = 3; j < 6; j++) {
adc_in = ins_accel[j-3];
_sensor_cal[j] = _sensor_cal[j] * 0.9 + adc_in * 0.1;
}
if(flashcount == 5) {
Serial.printf_P(PSTR("*"));
FLASH_LEDS(true);
}
if(flashcount >= 10) {
flashcount = 0;
FLASH_LEDS(false);
}
flashcount++;
}
// null gravity from the Z accel
_sensor_cal[5] += 9.805;
total_change = fabs(prev[3] - _sensor_cal[3]) + fabs(prev[4] - _sensor_cal[4]) +fabs(prev[5] - _sensor_cal[5]);
max_offset = (_sensor_cal[3] > _sensor_cal[4]) ? _sensor_cal[3] : _sensor_cal[4];
max_offset = (max_offset > _sensor_cal[5]) ? max_offset : _sensor_cal[5];
delay_cb(500);
} while ( total_change > _accel_total_cal_change || max_offset > _accel_max_cal_offset);
Serial.printf_P(PSTR(" "));
}
float
AP_IMU_INS::_calibrated(uint8_t channel, float ins_value)
{
return ins_value - _sensor_cal[channel];
}
bool
AP_IMU_INS::update(void)
{
float gyros[3];
float accels[3];
_ins->update();
_ins->get_gyros(gyros);
_ins->get_accels(accels);
_sample_time = _ins->sample_time();
// convert corrected gyro readings to delta acceleration
//
_gyro.x = _calibrated(0, gyros[0]);
_gyro.y = _calibrated(1, gyros[1]);
_gyro.z = _calibrated(2, gyros[2]);
// convert corrected accelerometer readings to acceleration
//
_accel.x = _calibrated(3, accels[0]);
_accel.y = _calibrated(4, accels[1]);
_accel.z = _calibrated(5, accels[2]);
// always updated
return true;
}
bool AP_IMU_INS::new_data_available(void) {
return _ins->new_data_available();
}
/// return the maximum gyro drift rate in radians/s/s. This
/// depends on what gyro chips are being used
float AP_IMU_INS::get_gyro_drift_rate(void)
{
return _ins->get_gyro_drift_rate();
}