ardupilot/APMrover2/sensors.cpp

#include "Rover.h"

#include <AP_RangeFinder/RangeFinder_Backend.h>
#include <AP_VisualOdom/AP_VisualOdom.h>

// check for new compass data - 10Hz
void Rover::update_compass(void)
{
    if (AP::compass().enabled() && compass.read()) {
        ahrs.set_compass(&compass);
    }
}

// Save compass offsets
void Rover::compass_save() {
    if (AP::compass().enabled() &&
        compass.get_learn_type() >= Compass::LEARN_INTERNAL &&
        !arming.is_armed()) {
        compass.save_offsets();
    }
}

// init beacons used for non-gps position estimates
void Rover::init_beacon()
{
    g2.beacon.init();
}

// init visual odometry sensor
void Rover::init_visual_odom()
{
    g2.visual_odom.init();
}

// update wheel encoders
void Rover::update_wheel_encoder()
{
    // exit immediately if not enabled
    if (g2.wheel_encoder.num_sensors() == 0) {
        return;
    }

    // update encoders
    g2.wheel_encoder.update();

    // initialise on first iteration
    const uint32_t now = AP_HAL::millis();
    if (wheel_encoder_last_ekf_update_ms == 0) {
        wheel_encoder_last_ekf_update_ms = now;
        for (uint8_t i = 0; i < g2.wheel_encoder.num_sensors(); i++) {
            wheel_encoder_last_angle_rad[i] = g2.wheel_encoder.get_delta_angle(i);
            wheel_encoder_last_update_ms[i] = g2.wheel_encoder.get_last_reading_ms(i);
        }
        return;
    }

    // calculate delta angle and delta time and send to EKF
    // use time of last ping from wheel encoder
    // send delta time (time between this wheel encoder time and previous wheel encoder time)
    // in case where wheel hasn't moved, count = 0 (cap the delta time at 50ms - or system time)
    //     use system clock of last update instead of time of last ping
    const float system_dt = (now - wheel_encoder_last_ekf_update_ms) / 1000.0f;
    for (uint8_t i = 0; i < g2.wheel_encoder.num_sensors(); i++) {
        // calculate angular change (in radians)
        const float curr_angle_rad = g2.wheel_encoder.get_delta_angle(i);
        const float delta_angle = curr_angle_rad - wheel_encoder_last_angle_rad[i];
        wheel_encoder_last_angle_rad[i] = curr_angle_rad;

        // save cumulative distances at current time (in meters)
        wheel_encoder_last_distance_m[i] = g2.wheel_encoder.get_distance(i);

        // calculate delta time
        float delta_time;
        const uint32_t latest_sensor_update_ms = g2.wheel_encoder.get_last_reading_ms(i);
        const uint32_t sensor_diff_ms = latest_sensor_update_ms - wheel_encoder_last_update_ms[i];

        // if we have not received any sensor updates, or time difference is too high then use time since last update to the ekf
        // check for old or insane sensor update times
        if (sensor_diff_ms == 0 || sensor_diff_ms > 100) {
            delta_time = system_dt;
            wheel_encoder_last_update_ms[i] = wheel_encoder_last_ekf_update_ms;
        } else {
            delta_time = sensor_diff_ms / 1000.0f;
            wheel_encoder_last_update_ms[i] = latest_sensor_update_ms;
        }

        /* delAng is the measured change in angular position from the previous measurement where a positive rotation is produced by forward motion of the vehicle (rad)
         * delTime is the time interval for the measurement of delAng (sec)
         * timeStamp_ms is the time when the rotation was last measured (msec)
         * posOffset is the XYZ body frame position of the wheel hub (m)
         */
        EKF3.writeWheelOdom(delta_angle, delta_time, wheel_encoder_last_update_ms[i], g2.wheel_encoder.get_pos_offset(i), g2.wheel_encoder.get_wheel_radius(i));
    }

    // record system time update for next iteration
    wheel_encoder_last_ekf_update_ms = now;
}

// Accel calibration

void Rover::accel_cal_update() {
    if (hal.util->get_soft_armed()) {
        return;
    }
    ins.acal_update();
    // check if new trim values, and set them    float trim_roll, trim_pitch;
    float trim_roll, trim_pitch;
    if (ins.get_new_trim(trim_roll, trim_pitch)) {
        ahrs.set_trim(Vector3f(trim_roll, trim_pitch, 0));
    }
}

// read the rangefinders
void Rover::read_rangefinders(void)
{
    rangefinder.update();
    Log_Write_Depth();
}

// initialise proximity sensor
void Rover::init_proximity(void)
{
    g2.proximity.init();
    g2.proximity.set_rangefinder(&rangefinder);
}

/*
  ask airspeed sensor for a new value, duplicated from plane
 */
void Rover::read_airspeed(void)
{
    g2.airspeed.update(should_log(MASK_LOG_IMU));
}

/*
  update RPM sensors
 */
void Rover::rpm_update(void)
{
    rpm_sensor.update();
    if (rpm_sensor.enabled(0) || rpm_sensor.enabled(1)) {
        if (should_log(MASK_LOG_RC)) {
            logger.Write_RPM(rpm_sensor);
        }
    }
}