Merge pull request #234 from PX4/seatbelt

Seatbelt for fixed wing

6 files changed, 159 insertions, 253 deletions

diff --git a/apps/controllib/fixedwing.cpp b/apps/controllib/fixedwing.cpp
index 7f5711c47..1cc28b9dd 100644
--- a/apps/controllib/fixedwing.cpp
+++ b/apps/controllib/fixedwing.cpp
@@ -86,113 +86,6 @@ void BlockStabilization::update(float pCmd, float qCmd, float rCmd,
 	_yawDamper.update(rCmd, r);
 }
 
-BlockHeadingHold::BlockHeadingHold(SuperBlock *parent, const char *name) :
-	SuperBlock(parent, name),
-	_psi2Phi(this, "PSI2PHI"),
-	_phi2P(this, "PHI2P"),
-	_phiLimit(this, "PHI_LIM")
-{
-}
-
-BlockHeadingHold::~BlockHeadingHold() {};
-
-float BlockHeadingHold::update(float psiCmd, float phi, float psi, float p)
-{
-	float psiError = _wrap_pi(psiCmd - psi);
-	float phiCmd = _phiLimit.update(_psi2Phi.update(psiError));
-	return _phi2P.update(phiCmd - phi);
-}
-
-BlockVelocityHoldBackside::BlockVelocityHoldBackside(SuperBlock *parent, const char *name) :
-	SuperBlock(parent, name),
-	_v2Theta(this, "V2THE"),
-	_theta2Q(this, "THE2Q"),
-	_theLimit(this, "THE"),
-	_vLimit(this, "V")
-{
-}
-
-BlockVelocityHoldBackside::~BlockVelocityHoldBackside() {};
-
-float BlockVelocityHoldBackside::update(float vCmd, float v, float theta, float q)
-{
-	// negative sign because nose over to increase speed
-	float thetaCmd = _theLimit.update(-_v2Theta.update(_vLimit.update(vCmd) - v));
-	return _theta2Q.update(thetaCmd - theta);
-}
-
-BlockVelocityHoldFrontside::BlockVelocityHoldFrontside(SuperBlock *parent, const char *name) :
-	SuperBlock(parent, name),
-	_v2Thr(this, "V2THR")
-{
-}
-
-BlockVelocityHoldFrontside::~BlockVelocityHoldFrontside() {};
-
-float BlockVelocityHoldFrontside::update(float vCmd, float v)
-{
-	return _v2Thr.update(vCmd - v);
-}
-
-BlockAltitudeHoldBackside::BlockAltitudeHoldBackside(SuperBlock *parent, const char *name) :
-	SuperBlock(parent, name),
-	_h2Thr(this, "H2THR"),
-	_throttle(0)
-{
-}
-
-BlockAltitudeHoldBackside::~BlockAltitudeHoldBackside() {};
-
-void BlockAltitudeHoldBackside::update(float hCmd, float h)
-{
-	_throttle = _h2Thr.update(hCmd - h);
-}
-
-BlockAltitudeHoldFrontside::BlockAltitudeHoldFrontside(SuperBlock *parent, const char *name) :
-	SuperBlock(parent, name),
-	_h2Theta(this, "H2THE"),
-	_theta2Q(this, "THE2Q")
-{
-}
-
-BlockAltitudeHoldFrontside::~BlockAltitudeHoldFrontside() {};
-
-float BlockAltitudeHoldFrontside::update(float hCmd, float h, float theta, float q)
-{
-	float thetaCmd = _h2Theta.update(hCmd - h);
-	return _theta2Q.update(thetaCmd - theta);
-}
-
-BlockBacksideAutopilot::BlockBacksideAutopilot(SuperBlock *parent,
-		const char *name,
-		BlockStabilization *stabilization) :
-	SuperBlock(parent, name),
-	_stabilization(stabilization),
-	_headingHold(this, ""),
-	_velocityHold(this, ""),
-	_altitudeHold(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", true) /* FWB_ specific throttle trim (full name: FWB_TRIM_THR) */
-{
-}
-
-BlockBacksideAutopilot::~BlockBacksideAutopilot() {};
-
-void BlockBacksideAutopilot::update(float hCmd, float vCmd, float rCmd, float psiCmd,
-				    float h, float v,
-				    float phi, float theta, float psi,
-				    float p, float q, float r)
-{
-	_altitudeHold.update(hCmd, h);
-	_stabilization->update(
-		_headingHold.update(psiCmd, phi, psi, p),
-		_velocityHold.update(vCmd, v, theta, q),
-		rCmd,
-		p, q, r);
-}
-
 BlockWaypointGuidance::BlockWaypointGuidance(SuperBlock *parent, const char *name) :
 	SuperBlock(parent, name),
 	_xtYawLimit(this, "XT2YAW"),
@@ -251,9 +144,33 @@ BlockUorbEnabledAutopilot::~BlockUorbEnabledAutopilot() {};
 BlockMultiModeBacksideAutopilot::BlockMultiModeBacksideAutopilot(SuperBlock *parent, const char *name) :
 	BlockUorbEnabledAutopilot(parent, name),
 	_stabilization(this, ""), // no name needed, already unique
-	_backsideAutopilot(this, "", &_stabilization),
+
+	// 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/roc hold
+	_h2Thr(this, "H2THR"),
+	_roc2Thr(this, "ROC2THR"),
+
+	// guidance block
 	_guide(this, ""),
+
+	// block params
+	_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", true), /* FWB_ specific throttle trim (full name: FWB_TRIM_THR) */
+
 	_vCmd(this, "V_CMD"),
+	_rocMax(this, "ROC_MAX"),
 	_attPoll(),
 	_lastPosCmd(),
 	_timeStamp(0)
@@ -305,7 +222,7 @@ void BlockMultiModeBacksideAutopilot::update()
 
 	// handle autopilot modes
 	if (_status.state_machine == SYSTEM_STATE_AUTO ||
-		_status.state_machine == SYSTEM_STATE_STABILIZED) {
+	    _status.state_machine == SYSTEM_STATE_STABILIZED) {
 
 		// update guidance
 		_guide.update(_pos, _att, _posCmd, _lastPosCmd);
@@ -313,19 +230,32 @@ void BlockMultiModeBacksideAutopilot::update()
 		// calculate velocity, XXX should be airspeed, but using ground speed for now
 		float v = sqrtf(_pos.vx * _pos.vx + _pos.vy * _pos.vy + _pos.vz * _pos.vz);
 
-		// commands
+		// altitude hold
+		float dThrottle = _h2Thr.update(_posCmd.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(
+				_vLimit.update(_vCmd.get()) - v));
+		float qCmd = _theta2Q.update(thetaCmd - _att.pitch);
+
+		// yaw rate cmd
 		float rCmd = 0;
 
-		_backsideAutopilot.update(
-			_posCmd.altitude, _vCmd.get(), rCmd, _guide.getPsiCmd(),
-			_pos.alt, v,
-			_att.roll, _att.pitch, _att.yaw,
-			_att.rollspeed, _att.pitchspeed, _att.yawspeed
-		);
-		_actuators.control[CH_AIL] = _backsideAutopilot.getAileron();
-		_actuators.control[CH_ELV] = _backsideAutopilot.getElevator();
-		_actuators.control[CH_RDR] = _backsideAutopilot.getRudder();
-		_actuators.control[CH_THR] = _backsideAutopilot.getThrottle();
+		// 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();
+		_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
@@ -336,14 +266,12 @@ void BlockMultiModeBacksideAutopilot::update()
 		if (!_status.flag_hil_enabled) {
 			/* limit to value of manual throttle */
 			_actuators.control[CH_THR] = (_actuators.control[CH_THR] < _manual.throttle) ?
-							_actuators.control[CH_THR] : _manual.throttle;
+						     _actuators.control[CH_THR] : _manual.throttle;
 		}
 
-
 	} else if (_status.state_machine == SYSTEM_STATE_MANUAL) {
 
 		if (_status.manual_control_mode == VEHICLE_MANUAL_CONTROL_MODE_DIRECT) {
-
 			_actuators.control[CH_AIL] = _manual.roll;
 			_actuators.control[CH_ELV] = _manual.pitch;
 			_actuators.control[CH_RDR] = _manual.yaw;
@@ -351,8 +279,60 @@ void BlockMultiModeBacksideAutopilot::update()
 
 		} else if (_status.manual_control_mode == VEHICLE_MANUAL_CONTROL_MODE_SAS) {
 
+			// calculate velocity, XXX should be airspeed, but using ground speed for now
+			float v = 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 = _roc2Thr.update(
+			//_rocMax.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 = _manual.throttle * (_vLimit.getMax() - _vLimit.getMin()) + _vLimit.getMin();
+			float thetaCmd = _theLimit.update(-_v2Theta.update(_vLimit.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();
+
+			// currenlty 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.flag_hil_enabled) {
+				/* 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
+		else if (0 /*_status.manual_control_mode == VEHICLE_MANUAL_CONTROL_MODE_SAS*/) {
+
 			_stabilization.update(_manual.roll, _manual.pitch, _manual.yaw,
-			_att.rollspeed, _att.pitchspeed, _att.yawspeed);
+					      _att.rollspeed, _att.pitchspeed, _att.yawspeed);
 
 			_actuators.control[CH_AIL] = _stabilization.getAileron();
 			_actuators.control[CH_ELV] = _stabilization.getElevator();
diff --git a/apps/controllib/fixedwing.hpp b/apps/controllib/fixedwing.hpp
index ea742641c..281cbb4cb 100644
--- a/apps/controllib/fixedwing.hpp
+++ b/apps/controllib/fixedwing.hpp
@@ -233,26 +233,6 @@ public:
 };
 
 /**
- * Heading hold autopilot block.
- * Aircraft Control and Simulation, Stevens and Lewis
- * Heading hold, pg. 348
- */
-class __EXPORT BlockHeadingHold : public SuperBlock
-{
-private:
-	BlockP _psi2Phi;
-	BlockP _phi2P;
-	BlockLimitSym _phiLimit;
-public:
-	BlockHeadingHold(SuperBlock *parent, const char *name);
-	virtual ~BlockHeadingHold();
-	/**
-	 * returns pCmd
-	 */
-	float update(float psiCmd, float phi, float psi, float p);
-};
-
-/**
  * Frontside/ Backside Control Systems
  *
  * Frontside :
@@ -270,106 +250,6 @@ public:
  */
 
 /**
- * Backside velocity hold autopilot block.
- * v -> theta -> q -> elevator
- */
-class __EXPORT BlockVelocityHoldBackside : public SuperBlock
-{
-private:
-	BlockPID _v2Theta;
-	BlockPID _theta2Q;
-	BlockLimit _theLimit;
-	BlockLimit _vLimit;
-public:
-	BlockVelocityHoldBackside(SuperBlock *parent, const char *name);
-	virtual ~BlockVelocityHoldBackside();
-	/**
-	 * returns qCmd
-	 */
-	float update(float vCmd, float v, float theta, float q);
-};
-
-/**
- * Frontside velocity hold autopilot block.
- * v -> throttle
- */
-class __EXPORT BlockVelocityHoldFrontside : public SuperBlock
-{
-private:
-	BlockPID _v2Thr;
-public:
-	BlockVelocityHoldFrontside(SuperBlock *parent, const char *name);
-	virtual ~BlockVelocityHoldFrontside();
-	/**
-	 * returns throttle
-	 */
-	float update(float vCmd, float v);
-};
-
-/**
- * Backside altitude hold autopilot block.
- * h -> throttle
- */
-class __EXPORT BlockAltitudeHoldBackside : public SuperBlock
-{
-private:
-	BlockPID _h2Thr;
-	float _throttle;
-public:
-	BlockAltitudeHoldBackside(SuperBlock *parent, const char *name);
-	virtual ~BlockAltitudeHoldBackside();
-	void update(float hCmd, float h);
-	float getThrottle() { return _throttle; }
-};
-
-/**
- * Frontside altitude hold autopilot block.
- * h -> theta > q -> elevator
- */
-class __EXPORT BlockAltitudeHoldFrontside : public SuperBlock
-{
-private:
-	BlockPID _h2Theta;
-	BlockPID _theta2Q;
-public:
-	BlockAltitudeHoldFrontside(SuperBlock *parent, const char *name);
-	virtual ~BlockAltitudeHoldFrontside();
-	/**
-	 * return qCmd
-	 */
-	float update(float hCmd, float h, float theta, float q);
-};
-
-/**
- * Backside autopilot
- */
-class __EXPORT BlockBacksideAutopilot : public SuperBlock
-{
-private:
-	BlockStabilization *_stabilization;
-	BlockHeadingHold _headingHold;
-	BlockVelocityHoldBackside _velocityHold;
-	BlockAltitudeHoldBackside _altitudeHold;
-	BlockParam<float> _trimAil;
-	BlockParam<float> _trimElv;
-	BlockParam<float> _trimRdr;
-	BlockParam<float> _trimThr;
-public:
-	BlockBacksideAutopilot(SuperBlock *parent,
-			       const char *name,
-			       BlockStabilization *stabilization);
-	virtual ~BlockBacksideAutopilot();
-	void update(float hCmd, float vCmd, float rCmd, float psiCmd,
-		    float h, float v,
-		    float phi, float theta, float psi,
-		    float p, float q, float r);
-	float getRudder() { return _stabilization->getRudder() + _trimRdr.get(); }
-	float getAileron() { return _stabilization->getAileron() + _trimAil.get(); }
-	float getElevator() { return _stabilization->getElevator() + _trimElv.get(); }
-	float getThrottle() { return _altitudeHold.getThrottle() + _trimThr.get(); }
-};
-
-/**
  * Waypoint Guidance block
  */
 class __EXPORT BlockWaypointGuidance : public SuperBlock
@@ -416,10 +296,34 @@ public:
 class __EXPORT BlockMultiModeBacksideAutopilot : public BlockUorbEnabledAutopilot
 {
 private:
+	// stabilization
 	BlockStabilization _stabilization;
-	BlockBacksideAutopilot _backsideAutopilot;
+
+	// heading hold
+	BlockP _psi2Phi;
+	BlockP _phi2P;
+	BlockLimitSym _phiLimit;
+
+	// velocity hold
+	BlockPID _v2Theta;
+	BlockPID _theta2Q;
+	BlockLimit _theLimit;
+	BlockLimit _vLimit;
+
+	// altitude/ roc hold
+	BlockPID _h2Thr;
+	BlockPID _roc2Thr;
+
+	// guidance
 	BlockWaypointGuidance _guide;
+
+	// block params
+	BlockParam<float> _trimAil;
+	BlockParam<float> _trimElv;
+	BlockParam<float> _trimRdr;
+	BlockParam<float> _trimThr;
 	BlockParam<float> _vCmd;
+	BlockParam<float> _rocMax;
 
 	struct pollfd _attPoll;
 	vehicle_global_position_setpoint_s _lastPosCmd;
diff --git a/apps/examples/control_demo/params.c b/apps/examples/control_demo/params.c
index 83e01e63c..428b779b1 100644
--- a/apps/examples/control_demo/params.c
+++ b/apps/examples/control_demo/params.c
@@ -56,4 +56,16 @@ PARAM_DEFINE_FLOAT(FWB_V_MIN, 10.0f);       // minimum commanded velocity
 PARAM_DEFINE_FLOAT(FWB_V_CMD, 12.0f);       // commanded velocity
 PARAM_DEFINE_FLOAT(FWB_V_MAX, 16.0f);       // maximum commanded velocity
 
+// rate of climb
+// this is what rate of climb is commanded (in m/s) 
+// when the pitch stick is fully defelcted in simple mode
+PARAM_DEFINE_FLOAT(FWB_ROC_MAX, 1.0f);
+
+//  rate of climb -> thr
+PARAM_DEFINE_FLOAT(FWB_ROC2THR_P, 0.01f);   // rate of climb to throttle PID
+PARAM_DEFINE_FLOAT(FWB_ROC2THR_I, 0.0f);
+PARAM_DEFINE_FLOAT(FWB_ROC2THR_D, 0.0f);
+PARAM_DEFINE_FLOAT(FWB_ROC2THR_D_LP, 0.0f);
+PARAM_DEFINE_FLOAT(FWB_ROC2THR_I_MAX, 0.0f);
+
 PARAM_DEFINE_FLOAT(FWB_TRIM_THR, 0.8f);     // trim throttle (0,1)
diff --git a/apps/examples/kalman_demo/KalmanNav.cpp b/apps/examples/kalman_demo/KalmanNav.cpp
index 955e77b3e..6df454a55 100644
--- a/apps/examples/kalman_demo/KalmanNav.cpp
+++ b/apps/examples/kalman_demo/KalmanNav.cpp
@@ -61,8 +61,8 @@ KalmanNav::KalmanNav(SuperBlock *parent, const char *name) :
 	HAtt(6, 9),
 	RAtt(6, 6),
 	// position measurement ekf matrices
-	HPos(5, 9),
-	RPos(5, 5),
+	HPos(6, 9),
+	RPos(6, 6),
 	// attitude representations
 	C_nb(),
 	q(),
@@ -95,6 +95,7 @@ KalmanNav::KalmanNav(SuperBlock *parent, const char *name) :
 	_rGpsVel(this, "R_GPS_VEL"),
 	_rGpsPos(this, "R_GPS_POS"),
 	_rGpsAlt(this, "R_GPS_ALT"),
+	_rPressAlt(this, "R_PRESS_ALT"),
 	_rAccel(this, "R_ACCEL"),
 	_magDip(this, "ENV_MAG_DIP"),
 	_magDec(this, "ENV_MAG_DEC"),
@@ -134,6 +135,7 @@ KalmanNav::KalmanNav(SuperBlock *parent, const char *name) :
 	HPos(2, 6) = 1.0e7f * M_RAD_TO_DEG_F;
 	HPos(3, 7) = 1.0e7f * M_RAD_TO_DEG_F;
 	HPos(4, 8) = 1.0f;
+	HPos(5, 8) = 1.0f;
 
 	// initialize all parameters
 	updateParams();
@@ -192,7 +194,7 @@ void KalmanNav::update()
 	    gpsUpdate &&
 	    _gps.fix_type > 2
 	    //&& _gps.counter_pos_valid > 10
-	    ) {
+	   ) {
 		vN = _gps.vel_n_m_s;
 		vE = _gps.vel_e_m_s;
 		vD = _gps.vel_d_m_s;
@@ -630,12 +632,13 @@ int KalmanNav::correctPos()
 	using namespace math;
 
 	// residual
-	Vector y(5);
+	Vector y(6);
 	y(0) = _gps.vel_n_m_s - vN;
 	y(1) = _gps.vel_e_m_s - vE;
 	y(2) = double(_gps.lat) - lat * 1.0e7 * M_RAD_TO_DEG;
 	y(3) = double(_gps.lon) - lon * 1.0e7 * M_RAD_TO_DEG;
 	y(4) = double(_gps.alt) / 1.0e3 - alt;
+	y(5) = double(_sensors.baro_alt_meter) - alt;
 
 	// compute correction
 	// http://en.wikipedia.org/wiki/Extended_Kalman_filter
@@ -685,7 +688,8 @@ int KalmanNav::correctPos()
 		       double(y(1) / sqrtf(RPos(1, 1))),
 		       double(y(2) / sqrtf(RPos(2, 2))),
 		       double(y(3) / sqrtf(RPos(3, 3))),
-		       double(y(4) / sqrtf(RPos(4, 4))));
+		       double(y(4) / sqrtf(RPos(4, 4))),
+		       double(y(5) / sqrtf(RPos(5, 5))));
 	}
 
 	return ret_ok;
@@ -740,7 +744,8 @@ void KalmanNav::updateParams()
 	float noiseVel = _rGpsVel.get();
 	float noiseLatDegE7 = 1.0e7f * M_RAD_TO_DEG_F * _rGpsPos.get() / R;
 	float noiseLonDegE7 = noiseLatDegE7 / cosLSing;
-	float noiseAlt = _rGpsAlt.get();
+	float noiseGpsAlt = _rGpsAlt.get();
+	float noisePressAlt = _rPressAlt.get();
 
 	// bound noise to prevent singularities
 	if (noiseVel < noiseMin) noiseVel = noiseMin;
@@ -749,13 +754,16 @@ void KalmanNav::updateParams()
 
 	if (noiseLonDegE7 < noiseMin) noiseLonDegE7 = noiseMin;
 
-	if (noiseAlt < noiseMin) noiseAlt = noiseMin;
+	if (noiseGpsAlt < noiseMin) noiseGpsAlt = noiseMin;
+
+	if (noisePressAlt < noiseMin) noisePressAlt = noiseMin;
 
 	RPos(0, 0) = noiseVel * noiseVel; // vn
 	RPos(1, 1) = noiseVel * noiseVel; // ve
 	RPos(2, 2) = noiseLatDegE7 * noiseLatDegE7; // lat
 	RPos(3, 3) = noiseLonDegE7 * noiseLonDegE7; // lon
-	RPos(4, 4) = noiseAlt * noiseAlt; // h
+	RPos(4, 4) = noiseGpsAlt * noiseGpsAlt; // h
+	RPos(5, 5) = noisePressAlt * noisePressAlt; // h
 	// XXX, note that RPos depends on lat, so updateParams should
 	// be called if lat changes significantly
 }
diff --git a/apps/examples/kalman_demo/KalmanNav.hpp b/apps/examples/kalman_demo/KalmanNav.hpp
index 7709ac697..c2bf18115 100644
--- a/apps/examples/kalman_demo/KalmanNav.hpp
+++ b/apps/examples/kalman_demo/KalmanNav.hpp
@@ -159,6 +159,7 @@ protected:
 	control::BlockParam<float> _rGpsVel;    /**< gps velocity measurement noise */
 	control::BlockParam<float> _rGpsPos;    /**< gps position measurement noise */
 	control::BlockParam<float> _rGpsAlt;    /**< gps altitude measurement noise */
+	control::BlockParam<float> _rPressAlt;  /**< press altitude measurement noise */
 	control::BlockParam<float> _rAccel;     /**< accelerometer measurement noise */
 	control::BlockParam<float> _magDip;     /**< magnetic inclination with level */
 	control::BlockParam<float> _magDec;     /**< magnetic declination, clockwise rotation */
diff --git a/apps/examples/kalman_demo/params.c b/apps/examples/kalman_demo/params.c
index 3bfe01261..91e80a5ea 100644
--- a/apps/examples/kalman_demo/params.c
+++ b/apps/examples/kalman_demo/params.c
@@ -7,6 +7,7 @@ PARAM_DEFINE_FLOAT(KF_R_MAG, 1.0f);
 PARAM_DEFINE_FLOAT(KF_R_GPS_VEL, 1.0f);
 PARAM_DEFINE_FLOAT(KF_R_GPS_POS, 5.0f);
 PARAM_DEFINE_FLOAT(KF_R_GPS_ALT, 5.0f);
+PARAM_DEFINE_FLOAT(KF_R_PRESS_ALT, 0.1f);
 PARAM_DEFINE_FLOAT(KF_R_ACCEL, 1.0f);
 PARAM_DEFINE_FLOAT(KF_FAULT_POS, 10.0f);
 PARAM_DEFINE_FLOAT(KF_FAULT_ATT, 10.0f);