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;
}

/*
  return true if the current settings and mode should allow for stick mixing
 */
static bool stick_mixing_enabled(void)
{
    if (control_mode == CIRCLE || control_mode > FLY_BY_WIRE_B) {
        // we're in an auto mode. Check the stick mixing flag
        if (g.stick_mixing &&
            geofence_stickmixing() &&
            failsafe == FAILSAFE_NONE) {
            // we're in an auto mode, and haven't triggered failsafe
            return true;
        } else {
            return false;
        }
    }
    // non-auto mode. Always do stick mixing
    return true;
}


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 (stick_mixing_enabled()) {
        if (control_mode < FLY_BY_WIRE_A || control_mode > FLY_BY_WIRE_C) {
            // do stick mixing on aileron/elevator if not in a fly by
            // wire mode
            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();
        }

        // stick mixing performed for rudder for all cases including FBW
        // important for steering on the ground during landing
        // -----------------------------------------------
        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 = ins.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(int16_t last_throttle)
{
    // if slew limit rate is set to zero then do not slew limit
    if (g.throttle_slewrate) {                   
        // limit throttle change by the given percentage per second
        float temp = g.throttle_slewrate * G_Dt * 0.01 * fabs(g.channel_throttle.radio_max - g.channel_throttle.radio_min);
        // allow a minimum change of 1 PWM per cycle
        if (temp < 1) {
            temp = 1;
        }
        g.channel_throttle.radio_out = constrain(g.channel_throttle.radio_out, last_throttle - temp, last_throttle + temp);
    }
}


/* 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;
    int16_t last_throttle = g.channel_throttle.radio_out;

    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;

        // setup extra aileron channel. We want this to come from the
        // main aileron input channel, but using the 2nd channels dead
        // zone, reverse and min/max settings. We need to use
        // pwm_to_angle_dz() to ensure we don't trim the value for the
        // deadzone of the main aileron channel, otherwise the 2nd
        // aileron won't quite follow the first one
        int16_t aileron_in = g.channel_roll.pwm_to_angle_dz(0);
        RC_Channel_aux::set_servo_out(RC_Channel_aux::k_aileron, aileron_in);

        // this aileron variant assumes you have the corresponding
        // input channel setup in your transmitter for manual control
        // of the 2nd aileron
        RC_Channel_aux::copy_radio_in_out(RC_Channel_aux::k_aileron_with_input);

        // copy flap control from transmitter
        RC_Channel_aux::copy_radio_in_out(RC_Channel_aux::k_flap_auto);

        if (g.mix_mode != 0) {
            // set any differential spoilers to follow the elevons in
            // manual mode. 
            RC_Channel_aux::set_radio(RC_Channel_aux::k_dspoiler1, g.channel_roll.radio_out);
            RC_Channel_aux::set_radio(RC_Channel_aux::k_dspoiler2, g.channel_pitch.radio_out);
        }
    } else {
        if (g.mix_mode == 0) {
            // both types of secondary aileron are slaved to the roll servo out
            RC_Channel_aux::set_servo_out(RC_Channel_aux::k_aileron, g.channel_roll.servo_out);
            RC_Channel_aux::set_servo_out(RC_Channel_aux::k_aileron_with_input, 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);

			/* Differential Spoilers
               If differential spoilers are setup, then we translate
               rudder control into splitting of the two ailerons on
               the side of the aircraft where we want to induce
               additional drag.
             */
			if (RC_Channel_aux::function_assigned(RC_Channel_aux::k_dspoiler1) && RC_Channel_aux::function_assigned(RC_Channel_aux::k_dspoiler2)) {
				float ch3 = ch1;
				float ch4 = ch2;
				if ( BOOL_TO_SIGN(g.reverse_elevons) * g.channel_rudder.servo_out < 0) {
				    ch1 += abs(g.channel_rudder.servo_out);
				    ch3 -= abs(g.channel_rudder.servo_out);
				} else {
					ch2 += abs(g.channel_rudder.servo_out);
				    ch4 -= abs(g.channel_rudder.servo_out);
				}
				RC_Channel_aux::set_servo_out(RC_Channel_aux::k_dspoiler1, ch3);
				RC_Channel_aux::set_servo_out(RC_Channel_aux::k_dspoiler2, ch4);
			}

            // directly set the radio_out values for elevon mode
            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 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
        if (g.mix_mode == 0) {
            g.channel_roll.calc_pwm();
            g.channel_pitch.calc_pwm();
        }
        g.channel_rudder.calc_pwm();

#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()) {
            // throttle is suppressed in auto mode
            g.channel_throttle.servo_out = 0;
            if (g.throttle_suppress_manual) {
                // manual pass through of throttle while throttle is suppressed
                g.channel_throttle.radio_out = g.channel_throttle.radio_in;
            } else {
                g.channel_throttle.calc_pwm();                
            }
        } else if (g.throttle_passthru_stabilize && 
                   (control_mode == STABILIZE || control_mode == FLY_BY_WIRE_A)) {
            // manual pass through of throttle while in FBWA or
            // STABILIZE mode with THR_PASS_STAB set
            g.channel_throttle.radio_out = g.channel_throttle.radio_in;
        } else {
            // normal throttle calculation based on servo_out
            g.channel_throttle.calc_pwm();
        }
#endif
    }

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

#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 bool demoing_servos;

static void demo_servos(byte i) {

    while(i > 0) {
        gcs_send_text_P(SEVERITY_LOW,PSTR("Demo Servos!"));
        demoing_servos = true;
#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
        demoing_servos = false;
        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;
}