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.
//****************************************************************

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

    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);
    }

    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) + 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(airspeed.use()) {
        speed = airspeed.get_airspeed();
    } else {
        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;

    // vectorize the rc channels
    RC_Channel_aux* rc_array[NUM_CHANNELS];
    rc_array[CH_1] = NULL;
    rc_array[CH_2] = NULL;
    rc_array[CH_3] = NULL;
    rc_array[CH_4] = NULL;
    rc_array[CH_5] = &g.rc_5;
    rc_array[CH_6] = &g.rc_6;
    rc_array[CH_7] = &g.rc_7;
    rc_array[CH_8] = &g.rc_8;

    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 ?
        if (g_rc_function[RC_Channel_aux::k_aileron]) {
            if (g_rc_function[RC_Channel_aux::k_aileron] != rc_array[g.flight_mode_channel-1]) {
                g_rc_function[RC_Channel_aux::k_aileron]->radio_out     = g_rc_function[RC_Channel_aux::k_aileron]->radio_in;
            }
        }
        // only use radio_in if the channel is not used as flight_mode_channel
        if (g_rc_function[RC_Channel_aux::k_flap_auto]) {
            if (g_rc_function[RC_Channel_aux::k_flap_auto] != rc_array[g.flight_mode_channel-1]) {
                g_rc_function[RC_Channel_aux::k_flap_auto]->radio_out   = g_rc_function[RC_Channel_aux::k_flap_auto]->radio_in;
            } else {
                g_rc_function[RC_Channel_aux::k_flap_auto]->radio_out   = g_rc_function[RC_Channel_aux::k_flap_auto]->radio_trim;
            }
        }
    } else {
        if (g.mix_mode == 0) {
            if (g_rc_function[RC_Channel_aux::k_aileron]) {
                g_rc_function[RC_Channel_aux::k_aileron]->servo_out = g.channel_roll.servo_out;
                g_rc_function[RC_Channel_aux::k_aileron]->calc_pwm();
            }

        }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 (g_rc_function[RC_Channel_aux::k_flap_auto] != NULL) {
        if(control_mode < FLY_BY_WIRE_B) {
            // only use radio_in if the channel is not used as flight_mode_channel
            if (g_rc_function[RC_Channel_aux::k_flap_auto] != rc_array[g.flight_mode_channel-1]) {
                g_rc_function[RC_Channel_aux::k_flap_auto]->radio_out = g_rc_function[RC_Channel_aux::k_flap_auto]->radio_in;
            } else {
                g_rc_function[RC_Channel_aux::k_flap_auto]->radio_out = g_rc_function[RC_Channel_aux::k_flap_auto]->radio_trim;
            }
        } 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) {
                g_rc_function[RC_Channel_aux::k_flap_auto]->servo_out = 0;
            } else if (g.flap_2_speed != 0 && flapSpeedSource > g.flap_2_speed) {
                g_rc_function[RC_Channel_aux::k_flap_auto]->servo_out = g.flap_1_percent;
            } else {
                g_rc_function[RC_Channel_aux::k_flap_auto]->servo_out = g.flap_2_percent;
            }
            g_rc_function[RC_Channel_aux::k_flap_auto]->calc_pwm();
        }
    }

#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;
}