ardupilot/ArduPlane/Attitude.pde

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

//****************************************************************
// Function that controls aileron/rudder, elevator, rudder (if 4 channel control) and throttle to produce desired attitude and airspeed.
//****************************************************************


/*
  get a speed scaling number for control surfaces. This is applied to
  PIDs to change the scaling of the PID with speed. At high speed we
  move the surfaces less, and at low speeds we move them more.
 */
static float get_speed_scaler(void)
{
    float aspeed, speed_scaler;
    if (ahrs.airspeed_estimate(&aspeed)) {
        if (aspeed > 0) {
            speed_scaler = g.scaling_speed / aspeed;
        } else {
            speed_scaler = 2.0;
        }
        speed_scaler = constrain(speed_scaler, 0.5, 2.0);
    } else {
        if (g.channel_throttle.servo_out > 0) {
            speed_scaler = 0.5 + ((float)THROTTLE_CRUISE / g.channel_throttle.servo_out / 2.0);                 // First order taylor expansion of square root
            // Should maybe be to the 2/7 power, but we aren't goint to implement that...
        }else{
            speed_scaler = 1.67;
        }
        // This case is constrained tighter as we don't have real speed info
        speed_scaler = constrain(speed_scaler, 0.6, 1.67);
    }
    return speed_scaler;
}


static void stabilize()
{
    float ch1_inf = 1.0;
    float ch2_inf = 1.0;
    float ch4_inf = 1.0;
    float speed_scaler = get_speed_scaler();

    if(crash_timer > 0) {
        nav_roll_cd = 0;
    }

    if (inverted_flight) {
        // we want to fly upside down. We need to cope with wrap of
        // the roll_sensor interfering with wrap of nav_roll, which
        // would really confuse the PID code. The easiest way to
        // handle this is to ensure both go in the same direction from
        // zero
        nav_roll_cd += 18000;
        if (ahrs.roll_sensor < 0) nav_roll_cd -= 36000;
    }

#if APM_CONTROL == DISABLED
	// Calculate dersired servo output for the roll
	// ---------------------------------------------
	g.channel_roll.servo_out = g.pidServoRoll.get_pid((nav_roll_cd - ahrs.roll_sensor), speed_scaler);
	int32_t tempcalc = nav_pitch_cd +
	        fabs(ahrs.roll_sensor * g.kff_pitch_compensation) +
	        (g.channel_throttle.servo_out * g.kff_throttle_to_pitch) -
	        (ahrs.pitch_sensor - g.pitch_trim_cd);
    if (inverted_flight) {
        // when flying upside down the elevator control is inverted
        tempcalc = -tempcalc;
    }
	g.channel_pitch.servo_out = g.pidServoPitch.get_pid(tempcalc, speed_scaler);
#else // APM_CONTROL == ENABLED
    // calculate roll and pitch control using new APM_Control library
	g.channel_roll.servo_out = g.rollController.get_servo_out(nav_roll_cd, speed_scaler, control_mode == STABILIZE);
	g.channel_pitch.servo_out = g.pitchController.get_servo_out(nav_pitch_cd, speed_scaler, control_mode == STABILIZE);    
#endif

    // Mix Stick input to allow users to override control surfaces
    // -----------------------------------------------------------
    if ((control_mode < FLY_BY_WIRE_A) ||
        (g.stick_mixing &&
         geofence_stickmixing() &&
         control_mode > FLY_BY_WIRE_B &&
         failsafe == FAILSAFE_NONE)) {

        // TODO: use RC_Channel control_mix function?
        ch1_inf = (float)g.channel_roll.radio_in - (float)g.channel_roll.radio_trim;
        ch1_inf = fabs(ch1_inf);
        ch1_inf = min(ch1_inf, 400.0);
        ch1_inf = ((400.0 - ch1_inf) /400.0);

        ch2_inf = (float)g.channel_pitch.radio_in - g.channel_pitch.radio_trim;
        ch2_inf = fabs(ch2_inf);
        ch2_inf = min(ch2_inf, 400.0);
        ch2_inf = ((400.0 - ch2_inf) /400.0);

        // scale the sensor input based on the stick input
        // -----------------------------------------------
        g.channel_roll.servo_out *= ch1_inf;
        g.channel_pitch.servo_out *= ch2_inf;

        // Mix in stick inputs
        // -------------------
        g.channel_roll.servo_out +=     g.channel_roll.pwm_to_angle();
        g.channel_pitch.servo_out +=    g.channel_pitch.pwm_to_angle();

        //Serial.printf_P(PSTR(" servo_out[CH_ROLL] "));
        //Serial.println(servo_out[CH_ROLL],DEC);
    }

    // stick mixing performed for rudder for all cases including FBW unless disabled for higher modes
    // important for steering on the ground during landing
    // -----------------------------------------------
    if (control_mode <= FLY_BY_WIRE_B ||
        (g.stick_mixing &&
         geofence_stickmixing() &&
         failsafe == FAILSAFE_NONE)) {
		ch4_inf = (float)g.channel_rudder.radio_in - (float)g.channel_rudder.radio_trim;
		ch4_inf = fabs(ch4_inf);
		ch4_inf = min(ch4_inf, 400.0);
		ch4_inf = ((400.0 - ch4_inf) /400.0);
	}

	// Apply output to Rudder
	// ----------------------
	calc_nav_yaw(speed_scaler, ch4_inf);
	g.channel_rudder.servo_out *= ch4_inf;
	g.channel_rudder.servo_out += g.channel_rudder.pwm_to_angle();

	// Call slew rate limiter if used
	// ------------------------------
	//#if(ROLL_SLEW_LIMIT != 0)
	//	g.channel_roll.servo_out = roll_slew_limit(g.channel_roll.servo_out);
	//#endif
}

static void crash_checker()
{
    if(ahrs.pitch_sensor < -4500) {
        crash_timer = 255;
    }
    if(crash_timer > 0)
        crash_timer--;
}


static void calc_throttle()
{
    if (!alt_control_airspeed()) {
        int16_t throttle_target = g.throttle_cruise + throttle_nudge;

        // TODO: think up an elegant way to bump throttle when
        // groundspeed_undershoot > 0 in the no airspeed sensor case; PID
        // control?

        // no airspeed sensor, we use nav pitch to determine the proper throttle output
        // AUTO, RTL, etc
        // ---------------------------------------------------------------------------
        if (nav_pitch_cd >= 0) {
            g.channel_throttle.servo_out = throttle_target + (g.throttle_max - throttle_target) * nav_pitch_cd / g.pitch_limit_max_cd;
        } else {
            g.channel_throttle.servo_out = throttle_target - (throttle_target - g.throttle_min) * nav_pitch_cd / g.pitch_limit_min_cd;
        }

        g.channel_throttle.servo_out = constrain(g.channel_throttle.servo_out, g.throttle_min.get(), g.throttle_max.get());
    } else {
        // throttle control with airspeed compensation
        // -------------------------------------------
        energy_error = airspeed_energy_error + altitude_error_cm * 0.098f;

        // positive energy errors make the throttle go higher
        g.channel_throttle.servo_out = g.throttle_cruise + g.pidTeThrottle.get_pid(energy_error);
        g.channel_throttle.servo_out += (g.channel_pitch.servo_out * g.kff_pitch_to_throttle);

        g.channel_throttle.servo_out = constrain(g.channel_throttle.servo_out,
                                                 g.throttle_min.get(), g.throttle_max.get());
    }

}

/*****************************************
* Calculate desired roll/pitch/yaw angles (in medium freq loop)
*****************************************/

//  Yaw is separated into a function for future implementation of heading hold on rolling take-off
// ----------------------------------------------------------------------------------------
static void calc_nav_yaw(float speed_scaler, float ch4_inf)
{
    if (hold_course != -1) {
        // steering on or close to ground
        g.channel_rudder.servo_out = g.pidWheelSteer.get_pid(bearing_error_cd, speed_scaler) + 
            g.kff_rudder_mix * g.channel_roll.servo_out;
        return;
    }

#if APM_CONTROL == DISABLED
    // always do rudder mixing from roll
    g.channel_rudder.servo_out = g.kff_rudder_mix * g.channel_roll.servo_out;

    // a PID to coordinate the turn (drive y axis accel to zero)
    Vector3f temp = imu.get_accel();
    int32_t error = -temp.y*100.0;

    g.channel_rudder.servo_out += g.pidServoRudder.get_pid(error, speed_scaler);
#else // APM_CONTROL == ENABLED
    // use the new APM_Control library
	g.channel_rudder.servo_out = g.yawController.get_servo_out(speed_scaler, ch4_inf < 0.25) + g.channel_roll.servo_out * g.kff_rudder_mix;
#endif
}


static void calc_nav_pitch()
{
    // Calculate the Pitch of the plane
    // --------------------------------
    if (alt_control_airspeed()) {
        nav_pitch_cd = -g.pidNavPitchAirspeed.get_pid(airspeed_error_cm);
    } else {
        nav_pitch_cd = g.pidNavPitchAltitude.get_pid(altitude_error_cm);
    }
    nav_pitch_cd = constrain(nav_pitch_cd, g.pitch_limit_min_cd.get(), g.pitch_limit_max_cd.get());
}


static void calc_nav_roll()
{
#define NAV_ROLL_BY_RATE 0
#if NAV_ROLL_BY_RATE
    // Scale from centidegrees (PID input) to radians per second. A P gain of 1.0 should result in a
    // desired rate of 1 degree per second per degree of error - if you're 15 degrees off, you'll try
    // to turn at 15 degrees per second.
    float turn_rate = ToRad(g.pidNavRoll.get_pid(bearing_error_cd) * .01);

    // Use airspeed_cruise as an analogue for airspeed if we don't have airspeed.
    float speed;
    if (!ahrs.airspeed_estimate(&speed)) {
        speed = g.airspeed_cruise_cm*0.01;

        // Floor the speed so that the user can't enter a bad value
        if(speed < 6) {
            speed = 6;
        }
    }

    // Bank angle = V*R/g, where V is airspeed, R is turn rate, and g is gravity.
    nav_roll = ToDeg(atan(speed*turn_rate/9.81)*100);

#else
    // this is the old nav_roll calculation. We will use this for 2.50
    // then remove for a future release
    float nav_gain_scaler = 0.01 * g_gps->ground_speed / g.scaling_speed;
    nav_gain_scaler = constrain(nav_gain_scaler, 0.2, 1.4);
    nav_roll_cd = g.pidNavRoll.get_pid(bearing_error_cd, nav_gain_scaler); //returns desired bank angle in degrees*100
#endif

    nav_roll_cd = constrain(nav_roll_cd, -g.roll_limit_cd.get(), g.roll_limit_cd.get());
}


/*****************************************
* Roll servo slew limit
*****************************************/
/*
 *  float roll_slew_limit(float servo)
 *  {
 *       static float last;
 *       float temp = constrain(servo, last-ROLL_SLEW_LIMIT * delta_ms_fast_loop/1000.f, last + ROLL_SLEW_LIMIT * delta_ms_fast_loop/1000.f);
 *       last = servo;
 *       return temp;
 *  }*/

/*****************************************
* Throttle slew limit
*****************************************/
static void throttle_slew_limit()
{
    static int16_t last = 1000;
    if(g.throttle_slewrate) {                   // if slew limit rate is set to zero then do not slew limit

        float temp = g.throttle_slewrate * G_Dt * 10.f;                 //  * 10 to scale % to pwm range of 1000 to 2000
        g.channel_throttle.radio_out = constrain(g.channel_throttle.radio_out, last - (int)temp, last + (int)temp);
        last = g.channel_throttle.radio_out;
    }
}


/* We want to supress the throttle if we think we are on the ground and in an autopilot controlled throttle mode.

   Disable throttle if following conditions are met:
   *       1 - We are in Circle mode (which we use for short term failsafe), or in FBW-B or higher
   *       AND
   *       2 - Our reported altitude is within 10 meters of the home altitude.
   *       3 - Our reported speed is under 5 meters per second.
   *       4 - We are not performing a takeoff in Auto mode
   *       OR
   *       5 - Home location is not set
*/
static bool suppress_throttle(void)
{
    if (!throttle_suppressed) {
        // we've previously met a condition for unsupressing the throttle
        return false;
    }
    if (control_mode != CIRCLE && control_mode <= FLY_BY_WIRE_A) {
        // the user controls the throttle
        throttle_suppressed = false;
        return false;
    }

    if (control_mode==AUTO && takeoff_complete == false) {
        // we're in auto takeoff 
        throttle_suppressed = false;
        return false;
    }
    
    if (labs(home.alt - current_loc.alt) >= 1000) {
        // we're more than 10m from the home altitude
        throttle_suppressed = false;
        return false;
    }

    if (g_gps != NULL && 
        g_gps->status() == GPS::GPS_OK && 
        g_gps->ground_speed >= 500) {
        // we're moving at more than 5 m/s
        throttle_suppressed = false;
        return false;        
    }

    // throttle remains suppressed
    return true;
}

/*****************************************
* Set the flight control servos based on the current calculated values
*****************************************/
static void set_servos(void)
{
    int16_t flapSpeedSource = 0;

    if(control_mode == MANUAL) {
        // do a direct pass through of radio values
        if (g.mix_mode == 0) {
            g.channel_roll.radio_out                = g.channel_roll.radio_in;
            g.channel_pitch.radio_out               = g.channel_pitch.radio_in;
        } else {
            g.channel_roll.radio_out                = APM_RC.InputCh(CH_ROLL);
            g.channel_pitch.radio_out               = APM_RC.InputCh(CH_PITCH);
        }
        g.channel_throttle.radio_out    = g.channel_throttle.radio_in;
        g.channel_rudder.radio_out              = g.channel_rudder.radio_in;
        // FIXME To me it does not make sense to control the aileron using radio_in in manual mode
        // Doug could you please take a look at this ?
        RC_Channel_aux::copy_radio_in_out(RC_Channel_aux::k_aileron);
        RC_Channel_aux::copy_radio_in_out(RC_Channel_aux::k_flap_auto);
    } else {
        if (g.mix_mode == 0) {
            RC_Channel_aux::set_servo_out(RC_Channel_aux::k_aileron, g.channel_roll.servo_out);
        }else{
            /*Elevon mode*/
            float ch1;
            float ch2;
            ch1 = g.channel_pitch.servo_out - (BOOL_TO_SIGN(g.reverse_elevons) * g.channel_roll.servo_out);
            ch2 = g.channel_pitch.servo_out + (BOOL_TO_SIGN(g.reverse_elevons) * g.channel_roll.servo_out);
            g.channel_roll.radio_out =      elevon1_trim + (BOOL_TO_SIGN(g.reverse_ch1_elevon) * (ch1 * 500.0/ SERVO_MAX));
            g.channel_pitch.radio_out =     elevon2_trim + (BOOL_TO_SIGN(g.reverse_ch2_elevon) * (ch2 * 500.0/ SERVO_MAX));
        }

#if THROTTLE_OUT == 0
        g.channel_throttle.servo_out = 0;
#else
        // convert 0 to 100% into PWM
        g.channel_throttle.servo_out = constrain(g.channel_throttle.servo_out, g.throttle_min.get(), g.throttle_max.get());

        if (suppress_throttle()) {
            g.channel_throttle.servo_out = 0;
        }

#endif


        if (control_mode >= FLY_BY_WIRE_B) {
            /* only do throttle slew limiting in modes where throttle
             *  control is automatic */
            throttle_slew_limit();
        }

#if OBC_FAILSAFE == ENABLED
        // this is to allow the failsafe module to deliberately crash 
        // the plane. Only used in extreme circumstances to meet the
        // OBC rules
        if (obc.crash_plane()) {
            g.channel_roll.servo_out = -4500;
            g.channel_pitch.servo_out = -4500;
            g.channel_rudder.servo_out = -4500;
            g.channel_throttle.servo_out = 0;
        }
#endif
        

        // push out the PWM values
        g.channel_roll.calc_pwm();
        g.channel_pitch.calc_pwm();
        g.channel_throttle.calc_pwm();
        g.channel_rudder.calc_pwm();
    }

    // Auto flap deployment
    if(control_mode < FLY_BY_WIRE_B) {
        // only use radio_in if the channel is not used as flight_mode_channel
        RC_Channel_aux::copy_radio_in_out(RC_Channel_aux::k_flap_auto);
    } else if (control_mode >= FLY_BY_WIRE_B) {
        // FIXME: use target_airspeed in both FBW_B and g.airspeed_enabled cases - Doug?
        if (control_mode == FLY_BY_WIRE_B) {
            flapSpeedSource = target_airspeed_cm * 0.01;
        } else if (airspeed.use()) {
            flapSpeedSource = g.airspeed_cruise_cm * 0.01;
        } else {
            flapSpeedSource = g.throttle_cruise;
        }
        if ( g.flap_1_speed != 0 && flapSpeedSource > g.flap_1_speed) {
            RC_Channel_aux::set_servo_out(RC_Channel_aux::k_flap_auto, 0);
        } else if (g.flap_2_speed != 0 && flapSpeedSource > g.flap_2_speed) {
            RC_Channel_aux::set_servo_out(RC_Channel_aux::k_flap_auto, g.flap_1_percent);
        } else {
            RC_Channel_aux::set_servo_out(RC_Channel_aux::k_flap_auto, g.flap_2_percent);
        }
    }

#if HIL_MODE == HIL_MODE_DISABLED || HIL_SERVOS
    // send values to the PWM timers for output
    // ----------------------------------------
    APM_RC.OutputCh(CH_1, g.channel_roll.radio_out);     // send to Servos
    APM_RC.OutputCh(CH_2, g.channel_pitch.radio_out);     // send to Servos
    APM_RC.OutputCh(CH_3, g.channel_throttle.radio_out);     // send to Servos
    APM_RC.OutputCh(CH_4, g.channel_rudder.radio_out);     // send to Servos
    // Route configurable aux. functions to their respective servos
    g.rc_5.output_ch(CH_5);
    g.rc_6.output_ch(CH_6);
    g.rc_7.output_ch(CH_7);
    g.rc_8.output_ch(CH_8);
 # if CONFIG_APM_HARDWARE != APM_HARDWARE_APM1
    g.rc_9.output_ch(CH_9);
    g.rc_10.output_ch(CH_10);
    g.rc_11.output_ch(CH_11);
 # endif
#endif
}

static void demo_servos(byte i) {

    while(i > 0) {
        gcs_send_text_P(SEVERITY_LOW,PSTR("Demo Servos!"));
#if HIL_MODE == HIL_MODE_DISABLED || HIL_SERVOS
        APM_RC.OutputCh(1, 1400);
        mavlink_delay(400);
        APM_RC.OutputCh(1, 1600);
        mavlink_delay(200);
        APM_RC.OutputCh(1, 1500);
#endif
        mavlink_delay(400);
        i--;
    }
}

// return true if we should use airspeed for altitude/throttle control
static bool alt_control_airspeed(void)
{
    return airspeed.use() && g.alt_control_algorithm == ALT_CONTROL_DEFAULT;
}