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diff --git a/src/modules/fixedwing_backside/fixedwing.cpp b/src/modules/fixedwing_backside/fixedwing.cpp
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+++ b/src/modules/fixedwing_backside/fixedwing.cpp
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+/****************************************************************************
+ *
+ *   Copyright (C) 2012 PX4 Development Team. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name PX4 nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/**
+ * @file fixedwing.cpp
+ *
+ * Controller library code
+ */
+
+#include "fixedwing.hpp"
+
+namespace control
+{
+
+namespace fixedwing
+{
+
+BlockYawDamper::BlockYawDamper(SuperBlock *parent, const char *name) :
+	SuperBlock(parent, name),
+	_rLowPass(this, "R_LP"),
+	_rWashout(this, "R_HP"),
+	_r2Rdr(this, "R2RDR"),
+	_rudder(0)
+{
+}
+
+BlockYawDamper::~BlockYawDamper() {};
+
+void BlockYawDamper::update(float rCmd, float r, float outputScale)
+{
+	_rudder = outputScale*_r2Rdr.update(rCmd -
+				_rWashout.update(_rLowPass.update(r)));
+}
+
+BlockStabilization::BlockStabilization(SuperBlock *parent, const char *name) :
+	SuperBlock(parent, name),
+	_yawDamper(this, ""),
+	_pLowPass(this, "P_LP"),
+	_qLowPass(this, "Q_LP"),
+	_p2Ail(this, "P2AIL"),
+	_q2Elv(this, "Q2ELV"),
+	_aileron(0),
+	_elevator(0)
+{
+}
+
+BlockStabilization::~BlockStabilization() {};
+
+void BlockStabilization::update(float pCmd, float qCmd, float rCmd,
+				float p, float q, float r, float outputScale)
+{
+	_aileron = outputScale*_p2Ail.update(
+			   pCmd - _pLowPass.update(p));
+	_elevator = outputScale*_q2Elv.update(
+			    qCmd - _qLowPass.update(q));
+	_yawDamper.update(rCmd, r, outputScale);
+}
+
+BlockMultiModeBacksideAutopilot::BlockMultiModeBacksideAutopilot(SuperBlock *parent, const char *name) :
+	BlockUorbEnabledAutopilot(parent, name),
+	_stabilization(this, ""), // no name needed, already unique
+
+	// heading hold
+	_psi2Phi(this, "PSI2PHI"),
+	_phi2P(this, "PHI2P"),
+	_phiLimit(this, "PHI_LIM"),
+
+	// velocity hold
+	_v2Theta(this, "V2THE"),
+	_theta2Q(this, "THE2Q"),
+	_theLimit(this, "THE"),
+	_vLimit(this, "V"),
+
+	// altitude/climb rate hold
+	_h2Thr(this, "H2THR"),
+	_cr2Thr(this, "CR2THR"),
+
+	// guidance block
+	_guide(this, ""),
+
+	_trimAil(this, "TRIM_ROLL", false), 	/* general roll trim (full name: TRIM_ROLL) */
+	_trimElv(this, "TRIM_PITCH", false), 	/* general pitch trim */
+	_trimRdr(this, "TRIM_YAW", false), 	/* general yaw trim */
+	_trimThr(this, "TRIM_THR"), 	/* FWB_ specific throttle trim (full name: FWB_TRIM_THR) */
+	_trimV(this, "TRIM_V"), 	/* FWB_ specific trim velocity (full name : FWB_TRIM_V) */
+
+	_vCmd(this, "V_CMD"),
+	_crMax(this, "CR_MAX"),
+	_attPoll(),
+	_lastPosCmd(),
+	_timeStamp(0)
+{
+	_attPoll.fd = _att.getHandle();
+	_attPoll.events = POLLIN;
+}
+
+void BlockMultiModeBacksideAutopilot::update()
+{
+	// wait for a sensor update, check for exit condition every 100 ms
+	if (poll(&_attPoll, 1, 100) < 0) return; // poll error
+
+	uint64_t newTimeStamp = hrt_absolute_time();
+	float dt = (newTimeStamp - _timeStamp) / 1.0e6f;
+	_timeStamp = newTimeStamp;
+
+	// check for sane values of dt
+	// to prevent large control responses
+	if (dt > 1.0f || dt < 0) return;
+
+	// set dt for all child blocks
+	setDt(dt);
+
+	// store old position command before update if new command sent
+	if (_posCmd.updated()) {
+		_lastPosCmd = _posCmd.getData();
+	}
+
+	// check for new updates
+	if (_param_update.updated()) updateParams();
+
+	// get new information from subscriptions
+	updateSubscriptions();
+
+	// default all output to zero unless handled by mode
+	for (unsigned i = 4; i < NUM_ACTUATOR_CONTROLS; i++)
+		_actuators.control[i] = 0.0f;
+
+	// only update guidance in auto mode
+	if (_status.main_state == MAIN_STATE_AUTO) {
+		// TODO use vehicle_control_mode here?
+		// update guidance
+		_guide.update(_pos, _att, _posCmd.current, _lastPosCmd.current);
+	}
+
+	// XXX handle STABILIZED (loiter on spot) as well
+	// once the system switches from manual or auto to stabilized
+	// the setpoint should update to loitering around this position
+
+	// handle autopilot modes
+	if (_status.main_state == MAIN_STATE_AUTO) {
+
+		// calculate velocity, XXX should be airspeed,
+		// but using ground speed for now for the purpose 
+		// of control we will limit the velocity feedback between
+		// the min/max velocity
+		float v = _vLimit.update(sqrtf(
+					_pos.vx * _pos.vx +
+					_pos.vy * _pos.vy +
+					_pos.vz * _pos.vz));
+
+		// limit velocity command between min/max velocity
+		float vCmd = _vLimit.update(_vCmd.get());
+
+		// altitude hold
+		float dThrottle = _h2Thr.update(_posCmd.current.altitude - _pos.alt);
+
+		// heading hold
+		float psiError = _wrap_pi(_guide.getPsiCmd() - _att.yaw);
+		float phiCmd = _phiLimit.update(_psi2Phi.update(psiError));
+		float pCmd = _phi2P.update(phiCmd - _att.roll);
+
+		// velocity hold
+		// negative sign because nose over to increase speed
+		float thetaCmd = _theLimit.update(-_v2Theta.update(vCmd - v));
+		float qCmd = _theta2Q.update(thetaCmd - _att.pitch);
+
+		// yaw rate cmd
+		float rCmd = 0;
+
+		// stabilization
+		float velocityRatio = _trimV.get()/v;
+		float outputScale = velocityRatio*velocityRatio;
+		// this term scales the output based on the dynamic pressure change from trim
+		_stabilization.update(pCmd, qCmd, rCmd,
+				      _att.rollspeed, _att.pitchspeed, _att.yawspeed,
+				      outputScale);
+
+		// output
+		_actuators.control[CH_AIL] = _stabilization.getAileron() + _trimAil.get();
+		_actuators.control[CH_ELV] = _stabilization.getElevator() + _trimElv.get();
+		_actuators.control[CH_RDR] = _stabilization.getRudder() + _trimRdr.get();
+		_actuators.control[CH_THR] = dThrottle + _trimThr.get();
+
+		// XXX limit throttle to manual setting (safety) for now.
+		// If it turns out to be confusing, it can be removed later once
+		// a first binary release can be targeted.
+		// This is not a hack, but a design choice.
+
+		// do not limit in HIL
+		if (_status.hil_state != HIL_STATE_ON) {
+			/* limit to value of manual throttle */
+			_actuators.control[CH_THR] = (_actuators.control[CH_THR] < _manual.throttle) ?
+						     _actuators.control[CH_THR] : _manual.throttle;
+		}
+
+	} else if (_status.main_state == MAIN_STATE_MANUAL) {
+		_actuators.control[CH_AIL] = _manual.roll;
+		_actuators.control[CH_ELV] = _manual.pitch;
+		_actuators.control[CH_RDR] = _manual.yaw;
+		_actuators.control[CH_THR] = _manual.throttle;
+
+	} else if (_status.main_state == MAIN_STATE_SEATBELT ||
+		_status.main_state == MAIN_STATE_EASY /* TODO, implement easy */) {
+
+		// calculate velocity, XXX should be airspeed, but using ground speed for now
+		// for the purpose of control we will limit the velocity feedback between
+		// the min/max velocity
+		float v = _vLimit.update(sqrtf(
+					_pos.vx * _pos.vx +
+					_pos.vy * _pos.vy +
+					_pos.vz * _pos.vz));
+
+		// pitch channel -> rate of climb
+		// TODO, might want to put a gain on this, otherwise commanding
+		// from +1 -> -1 m/s for rate of climb
+		//float dThrottle = _cr2Thr.update(
+		//_crMax.get()*_manual.pitch - _pos.vz);
+
+		// roll channel -> bank angle
+		float phiCmd = _phiLimit.update(_manual.roll * _phiLimit.getMax());
+		float pCmd = _phi2P.update(phiCmd - _att.roll);
+
+		// throttle channel -> velocity
+		// negative sign because nose over to increase speed
+		float vCmd = _vLimit.update(_manual.throttle *
+				(_vLimit.getMax() - _vLimit.getMin()) +
+				_vLimit.getMin());
+		float thetaCmd = _theLimit.update(-_v2Theta.update(vCmd - v));
+		float qCmd = _theta2Q.update(thetaCmd - _att.pitch);
+
+		// yaw rate cmd
+		float rCmd = 0;
+
+		// stabilization
+		_stabilization.update(pCmd, qCmd, rCmd,
+					  _att.rollspeed, _att.pitchspeed, _att.yawspeed);
+
+		// output
+		_actuators.control[CH_AIL] = _stabilization.getAileron() + _trimAil.get();
+		_actuators.control[CH_ELV] = _stabilization.getElevator() + _trimElv.get();
+		_actuators.control[CH_RDR] = _stabilization.getRudder() + _trimRdr.get();
+
+		// currently using manual throttle
+		// XXX if you enable this watch out, vz might be very noisy
+		//_actuators.control[CH_THR] = dThrottle + _trimThr.get();
+		_actuators.control[CH_THR] = _manual.throttle;
+
+		// XXX limit throttle to manual setting (safety) for now.
+		// If it turns out to be confusing, it can be removed later once
+		// a first binary release can be targeted.
+		// This is not a hack, but a design choice.
+
+		/* do not limit in HIL */
+		if (_status.hil_state != HIL_STATE_ON) {
+			/* limit to value of manual throttle */
+			_actuators.control[CH_THR] = (_actuators.control[CH_THR] < _manual.throttle) ?
+							 _actuators.control[CH_THR] : _manual.throttle;
+		}
+	// body rates controller, disabled for now
+	// TODO
+	} else if (0 /*_status.manual_control_mode == VEHICLE_MANUAL_CONTROL_MODE_SAS*/) {	// TODO use vehicle_control_mode here?
+
+		_stabilization.update(_manual.roll, _manual.pitch, _manual.yaw,
+					  _att.rollspeed, _att.pitchspeed, _att.yawspeed);
+
+		_actuators.control[CH_AIL] = _stabilization.getAileron();
+		_actuators.control[CH_ELV] = _stabilization.getElevator();
+		_actuators.control[CH_RDR] = _stabilization.getRudder();
+		_actuators.control[CH_THR] = _manual.throttle;
+	}
+
+	// update all publications
+	updatePublications();
+}
+
+BlockMultiModeBacksideAutopilot::~BlockMultiModeBacksideAutopilot()
+{
+	// send one last publication when destroyed, setting
+	// all output to zero
+	for (unsigned i = 0; i < NUM_ACTUATOR_CONTROLS; i++)
+		_actuators.control[i] = 0.0f;
+
+	updatePublications();
+}
+
+} // namespace fixedwing
+
+} // namespace control
+