ardupilot/ArduCopter/navigation.pde

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

//****************************************************************
// Function that will calculate the desired direction to fly and distance
//****************************************************************
static void navigate()
{
    // waypoint distance from plane in cm
    // ---------------------------------------
    wp_distance     = get_distance_cm(&filtered_loc, &next_WP);
    home_distance   = get_distance_cm(&filtered_loc, &home);

    // target_bearing is where we should be heading
    // --------------------------------------------
    target_bearing          = get_bearing_cd(&filtered_loc, &next_WP);
    home_to_copter_bearing  = get_bearing_cd(&home, &current_loc);
}

static bool check_missed_wp()
{
    int32_t temp;
    temp = target_bearing - original_target_bearing;
    temp = wrap_180(temp);
    return (labs(temp) > 9000);         // we passed the waypoint by 100 degrees
}

// ------------------------------
static void calc_XY_velocity(){
    static int32_t last_longitude = 0;
    static int32_t last_latitude  = 0;

    // called after GPS read
    // offset calculation of GPS speed:
    // used for estimations below 1.5m/s
    // y_GPS_speed positve = Up
    // x_GPS_speed positve = Right

    // initialise last_longitude and last_latitude
    if( last_longitude == 0 && last_latitude == 0 ) {
        last_longitude 	= g_gps->longitude;
        last_latitude 	= g_gps->latitude;
    }

    // this speed is ~ in cm because we are using 10^7 numbers from GPS
    float tmp = 1.0/dTnav;

    x_actual_speed  = (float)(g_gps->longitude - last_longitude)  * scaleLongDown * tmp;
    y_actual_speed  = (float)(g_gps->latitude  - last_latitude)  * tmp;

    last_longitude  = g_gps->longitude;
    last_latitude   = g_gps->latitude;

#if INERTIAL_NAV == ENABLED
    // inertial_nav
    xy_error_correction();
    filtered_loc.lng = xLeadFilter.get_position(g_gps->longitude, accels_velocity.x);
    filtered_loc.lat = yLeadFilter.get_position(g_gps->latitude,  accels_velocity.y);
#else
    filtered_loc.lng = xLeadFilter.get_position(g_gps->longitude, x_actual_speed, g_gps->get_lag());
    filtered_loc.lat = yLeadFilter.get_position(g_gps->latitude,  y_actual_speed, g_gps->get_lag());
#endif
}

static void calc_location_error(struct Location *next_loc)
{
    /*
     *  Becuase we are using lat and lon to do our distance errors here's a quick chart:
     *  100     = 1m
     *  1000    = 11m	 = 36 feet
     *  1800    = 19.80m = 60 feet
     *  3000    = 33m
     *  10000   = 111m
     */

    // X Error
    long_error      = (float)(next_loc->lng - current_loc.lng) * scaleLongDown;       // 500 - 0 = 500 Go East

    // Y Error
    lat_error       = next_loc->lat - current_loc.lat;                                                          // 500 - 0 = 500 Go North
}

#define NAV_ERR_MAX 600
#define NAV_RATE_ERR_MAX 250
static void calc_loiter(int16_t x_error, int16_t y_error)
{
    int32_t p,i,d;                                              // used to capture pid values for logging
    int32_t output;
    int32_t x_target_speed, y_target_speed;

    // East / West
    x_target_speed  = g.pi_loiter_lon.get_p(x_error);                           // calculate desired speed from lon error

#if LOGGING_ENABLED == ENABLED
    // log output if PID logging is on and we are tuning the yaw
    if( g.log_bitmask & MASK_LOG_PID && (g.radio_tuning == CH6_LOITER_KP || g.radio_tuning == CH6_LOITER_KI) ) {
        Log_Write_PID(CH6_LOITER_KP, x_error, x_target_speed, 0, 0, x_target_speed, tuning_value);
    }
#endif


    // calculate rate error
#if INERTIAL_NAV == ENABLED
    x_rate_error    = x_target_speed - accels_velocity.x;               // calc the speed error
#else
    x_rate_error    = x_target_speed - x_actual_speed;                          // calc the speed error
#endif


    p                               = g.pid_loiter_rate_lon.get_p(x_rate_error);
    i                               = g.pid_loiter_rate_lon.get_i(x_rate_error + x_error, dTnav);
    d                               = g.pid_loiter_rate_lon.get_d(x_error, dTnav);
    d                               = constrain(d, -2000, 2000);

    // get rid of noise
    if(abs(x_actual_speed) < 50) {
        d = 0;
    }

    output                  = p + i + d;
    nav_lon                 = constrain(output, -32000, 32000); // constraint to remove chance of overflow when adding int32_t to int16_t

#if LOGGING_ENABLED == ENABLED
    // log output if PID logging is on and we are tuning the yaw
    if( g.log_bitmask & MASK_LOG_PID && (g.radio_tuning == CH6_LOITER_RATE_KP || g.radio_tuning == CH6_LOITER_RATE_KI || g.radio_tuning == CH6_LOITER_RATE_KD) ) {
        Log_Write_PID(CH6_LOITER_RATE_KP, x_rate_error, p, i, d, nav_lon, tuning_value);
    }
#endif

    // North / South
    y_target_speed  = g.pi_loiter_lat.get_p(y_error);                           // calculate desired speed from lat error

#if LOGGING_ENABLED == ENABLED
    // log output if PID logging is on and we are tuning the yaw
    if( g.log_bitmask & MASK_LOG_PID && (g.radio_tuning == CH6_LOITER_KP || g.radio_tuning == CH6_LOITER_KI) ) {
        Log_Write_PID(CH6_LOITER_KP+100, y_error, y_target_speed, 0, 0, y_target_speed, tuning_value);
    }
#endif

    // calculate rate error
#if INERTIAL_NAV == ENABLED
    y_rate_error    = y_target_speed - accels_velocity.y;               // calc the speed error
#else
    y_rate_error    = y_target_speed - y_actual_speed;                          // calc the speed error
#endif

    p                               = g.pid_loiter_rate_lat.get_p(y_rate_error);
    i                               = g.pid_loiter_rate_lat.get_i(y_rate_error + y_error, dTnav);
    d                               = g.pid_loiter_rate_lat.get_d(y_error, dTnav);
    d                               = constrain(d, -2000, 2000);

    // get rid of noise
    if(abs(y_actual_speed) < 50) {
        d = 0;
    }

    output                  = p + i + d;
    nav_lat                 = constrain(output, -32000, 32000); // constraint to remove chance of overflow when adding int32_t to int16_t

#if LOGGING_ENABLED == ENABLED
    // log output if PID logging is on and we are tuning the yaw
    if( g.log_bitmask & MASK_LOG_PID && (g.radio_tuning == CH6_LOITER_RATE_KP || g.radio_tuning == CH6_LOITER_RATE_KI || g.radio_tuning == CH6_LOITER_RATE_KD) ) {
        Log_Write_PID(CH6_LOITER_RATE_KP+100, y_rate_error, p, i, d, nav_lat, tuning_value);
    }
#endif

    // copy over I term to Nav_Rate
    g.pid_nav_lon.set_integrator(g.pid_loiter_rate_lon.get_integrator());
    g.pid_nav_lat.set_integrator(g.pid_loiter_rate_lat.get_integrator());
}

static void calc_nav_rate(int16_t max_speed)
{
    float temp, temp_x, temp_y;

    // push us towards the original track
    update_crosstrack();

    int16_t cross_speed = crosstrack_error * -g.crosstrack_gain;     // scale down crosstrack_error in cm
    cross_speed     = constrain(cross_speed, -150, 150);

    // rotate by 90 to deal with trig functions
    temp                    = (9000l - target_bearing) * RADX100;
    temp_x                  = cos(temp);
    temp_y                  = sin(temp);

    // rotate desired spped vector:
    int32_t x_target_speed = max_speed   * temp_x - cross_speed * temp_y;
    int32_t y_target_speed = cross_speed * temp_x + max_speed   * temp_y;

    // East / West
    // calculate rate error
#if INERTIAL_NAV == ENABLED
    x_rate_error    = x_target_speed - accels_velocity.x;
#else
    x_rate_error    = x_target_speed - x_actual_speed;
#endif

    x_rate_error    = constrain(x_rate_error, -500, 500);
    nav_lon         = g.pid_nav_lon.get_pid(x_rate_error, dTnav);
    int32_t tilt    = (x_target_speed * x_target_speed * (int32_t)g.tilt_comp) / 10000;

    if(x_target_speed < 0) tilt = -tilt;
    nav_lon                 += tilt;


    // North / South
    // calculate rate error
#if INERTIAL_NAV == ENABLED
    y_rate_error    = y_target_speed - accels_velocity.y;
#else
    y_rate_error    = y_target_speed - y_actual_speed;
#endif

    y_rate_error    = constrain(y_rate_error, -500, 500);       // added a rate error limit to keep pitching down to a minimum
    nav_lat         = g.pid_nav_lat.get_pid(y_rate_error, dTnav);
    tilt            = (y_target_speed * y_target_speed * (int32_t)g.tilt_comp) / 10000;

    if(y_target_speed < 0) tilt = -tilt;
    nav_lat                 += tilt;

    // copy over I term to Loiter_Rate
    g.pid_loiter_rate_lon.set_integrator(g.pid_nav_lon.get_integrator());
    g.pid_loiter_rate_lat.set_integrator(g.pid_nav_lat.get_integrator());
}


// this calculation rotates our World frame of reference to the copter's frame of reference
// We use the DCM's matrix to precalculate these trig values at 50hz
static void calc_loiter_pitch_roll()
{
    //Serial.printf("ys %ld, cx %1.4f, _cx %1.4f | sy %1.4f, _sy %1.4f\n", dcm.yaw_sensor, cos_yaw_x, _cos_yaw_x, sin_yaw_y, _sin_yaw_y);
    // rotate the vector
    auto_roll       = (float)nav_lon * sin_yaw_y - (float)nav_lat * cos_yaw_x;
    auto_pitch      = (float)nav_lon * cos_yaw_x + (float)nav_lat * sin_yaw_y;

    // flip pitch because forward is negative
    auto_pitch = -auto_pitch;
}

static int16_t get_desired_speed(int16_t max_speed)
{
    /*
    Based on Equation by Bill Premerlani & Robert Lefebvre
    	(sq(V2)-sq(V1))/2 = A(X2-X1)
        derives to:
        V1 = sqrt(sq(V2) - 2*A*(X2-X1))
     */

    if(fast_corner) {
        // don't slow down
    }else{
        if(wp_distance < 20000){ // limit the size of numbers we're dealing with to avoide overflow
            // go slower
    	 	int32_t temp 	= 2 * 100 * (int32_t)(wp_distance - g.waypoint_radius * 100);
    	 	int32_t s_min 	= WAYPOINT_SPEED_MIN;
    	 	temp 			+= s_min * s_min;
    		max_speed 		= sqrt((float)temp);
            max_speed 		= min(max_speed, g.waypoint_speed_max);
        }
    }

    max_speed 		= min(max_speed, max_speed_old + (100 * dTnav));// limit going faster
    max_speed 		= max(max_speed, WAYPOINT_SPEED_MIN); 	// don't go too slow
    max_speed_old 	= max_speed;
    return max_speed;
}

static void reset_desired_speed()
{
    max_speed_old = 0;
}

static int16_t get_desired_climb_rate()
{
    if(alt_change_flag == ASCENDING) {
        return constrain(altitude_error / 4, 100, 180);         // 180cm /s up, minimum is 100cm/s

    }else if(alt_change_flag == DESCENDING) {
        return constrain(altitude_error / 6, -100, -10);         // -100cm /s down, max is -10cms

    }else{
        return 0;
    }
}

static void update_crosstrack(void)
{
    // Crosstrack Error
    // ----------------
    // If we are too far off or too close we don't do track following
    float temp = (target_bearing - original_target_bearing) * RADX100;
    crosstrack_error = sin(temp) * wp_distance;          // Meters we are off track line
}

static int32_t get_altitude_error()
{
    // Next_WP alt is our target alt
    // It changes based on climb rate
    // until it reaches the target_altitude
    return next_WP.alt - current_loc.alt;
}

static void clear_new_altitude()
{
    alt_change_flag = REACHED_ALT;
}

static void force_new_altitude(int32_t new_alt)
{
    next_WP.alt     = new_alt;
    alt_change_flag = REACHED_ALT;
}

static void set_new_altitude(int32_t new_alt)
{
    next_WP.alt     = new_alt;

    if(next_WP.alt > current_loc.alt + 20) {
        // we are below, going up
        alt_change_flag = ASCENDING;

    }else if(next_WP.alt < current_loc.alt - 20) {
        // we are above, going down
        alt_change_flag = DESCENDING;

    }else{
        // No Change
        alt_change_flag = REACHED_ALT;
    }
}

static void verify_altitude()
{
    if(alt_change_flag == ASCENDING) {
        // we are below, going up
        if(current_loc.alt >  next_WP.alt - 50) {
            alt_change_flag = REACHED_ALT;
        }
    }else if (alt_change_flag == DESCENDING) {
        // we are above, going down
        if(current_loc.alt <=  next_WP.alt + 50)
            alt_change_flag = REACHED_ALT;
    }
}


static int32_t wrap_360(int32_t error)
{
    if (error > 36000) error -= 36000;
    if (error < 0) error += 36000;
    return error;
}

static int32_t wrap_180(int32_t error)
{
    if (error > 18000) error -= 36000;
    if (error < -18000) error += 36000;
    return error;
}