Merge remote-tracking branch 'upstream/mtecs' into mtecs_estimator

21 files changed, 640 insertions, 236 deletions

diff --git a/ROMFS/px4fmu_common/init.d/rc.usb b/ROMFS/px4fmu_common/init.d/rc.usb
index 76593881d..d6e638c0a 100644
--- a/ROMFS/px4fmu_common/init.d/rc.usb
+++ b/ROMFS/px4fmu_common/init.d/rc.usb
@@ -17,6 +17,8 @@ mavlink stream -d /dev/ttyACM0 -s ATTITUDE_CONTROLS -r 30
 usleep 100000
 mavlink stream -d /dev/ttyACM0 -s SERVO_OUTPUT_RAW_0 -r 20
 usleep 100000
+mavlink stream -d /dev/ttyACM0 -s GLOBAL_POSITION_SETPOINT_INT -r 20
+usleep 100000
 
 # Exit shell to make it available to MAVLink
 exit
diff --git a/src/drivers/gps/ubx.cpp b/src/drivers/gps/ubx.cpp
index 7502809bd..c143eeb0c 100644
--- a/src/drivers/gps/ubx.cpp
+++ b/src/drivers/gps/ubx.cpp
@@ -69,6 +69,9 @@ UBX::UBX(const int &fd, struct vehicle_gps_position_s *gps_position) :
 	_gps_position(gps_position),
 	_configured(false),
 	_waiting_for_ack(false),
+	_got_posllh(false),
+	_got_velned(false),
+	_got_timeutc(false),
 	_disable_cmd_last(0)
 {
 	decode_init();
@@ -275,9 +278,10 @@ UBX::receive(unsigned timeout)
 	bool handled = false;
 
 	while (true) {
+		bool ready_to_return = _configured ? (_got_posllh && _got_velned && _got_timeutc) : handled;
 
 		/* poll for new data, wait for only UBX_PACKET_TIMEOUT (2ms) if something already received */
-		int ret = poll(fds, sizeof(fds) / sizeof(fds[0]), handled ? UBX_PACKET_TIMEOUT : timeout);
+		int ret = poll(fds, sizeof(fds) / sizeof(fds[0]), ready_to_return ? UBX_PACKET_TIMEOUT : timeout);
 
 		if (ret < 0) {
 			/* something went wrong when polling */
@@ -286,7 +290,10 @@ UBX::receive(unsigned timeout)
 
 		} else if (ret == 0) {
 			/* return success after short delay after receiving a packet or timeout after long delay */
-			if (handled) {
+			if (ready_to_return) {
+				_got_posllh = false;
+				_got_velned = false;
+				_got_timeutc = false;
 				return 1;
 
 			} else {
@@ -438,6 +445,7 @@ UBX::handle_message()
 
 					_rate_count_lat_lon++;
 
+					_got_posllh = true;
 					ret = 1;
 					break;
 				}
@@ -482,6 +490,7 @@ UBX::handle_message()
 					_gps_position->time_gps_usec += (uint64_t)(packet->time_nanoseconds * 1e-3f);
 					_gps_position->timestamp_time = hrt_absolute_time();
 
+					_got_timeutc = true;
 					ret = 1;
 					break;
 				}
@@ -557,6 +566,7 @@ UBX::handle_message()
 
 					_rate_count_vel++;
 
+					_got_velned = true;
 					ret = 1;
 					break;
 				}
diff --git a/src/drivers/gps/ubx.h b/src/drivers/gps/ubx.h
index 5cf47b60b..43d688893 100644
--- a/src/drivers/gps/ubx.h
+++ b/src/drivers/gps/ubx.h
@@ -397,6 +397,9 @@ private:
 	struct vehicle_gps_position_s *_gps_position;
 	bool			_configured;
 	bool			_waiting_for_ack;
+	bool			_got_posllh;
+	bool			_got_velned;
+	bool			_got_timeutc;
 	uint8_t			_message_class_needed;
 	uint8_t			_message_id_needed;
 	ubx_decode_state_t	_decode_state;
diff --git a/src/lib/ecl/attitude_fw/ecl_pitch_controller.cpp b/src/lib/ecl/attitude_fw/ecl_pitch_controller.cpp
index 0a909d02f..a0a18bc2e 100644
--- a/src/lib/ecl/attitude_fw/ecl_pitch_controller.cpp
+++ b/src/lib/ecl/attitude_fw/ecl_pitch_controller.cpp
@@ -61,9 +61,9 @@ ECL_PitchController::ECL_PitchController() :
 	_integrator(0.0f),
 	_rate_error(0.0f),
 	_rate_setpoint(0.0f),
-	_bodyrate_setpoint(0.0f)
+	_bodyrate_setpoint(0.0f),
+	_nonfinite_input_perf(perf_alloc(PC_COUNT, "fw att control pitch nonfinite input"))
 {
-	perf_alloc(PC_COUNT, "fw att control pitch nonfinite input");
 }
 
 ECL_PitchController::~ECL_PitchController()
diff --git a/src/lib/ecl/attitude_fw/ecl_roll_controller.cpp b/src/lib/ecl/attitude_fw/ecl_roll_controller.cpp
index 82903ef5a..d2a231694 100644
--- a/src/lib/ecl/attitude_fw/ecl_roll_controller.cpp
+++ b/src/lib/ecl/attitude_fw/ecl_roll_controller.cpp
@@ -59,9 +59,9 @@ ECL_RollController::ECL_RollController() :
 	_integrator(0.0f),
 	_rate_error(0.0f),
 	_rate_setpoint(0.0f),
-	_bodyrate_setpoint(0.0f)
+	_bodyrate_setpoint(0.0f),
+	_nonfinite_input_perf(perf_alloc(PC_COUNT, "fw att control roll nonfinite input"))
 {
-	perf_alloc(PC_COUNT, "fw att control roll nonfinite input");
 }
 
 ECL_RollController::~ECL_RollController()
diff --git a/src/lib/ecl/attitude_fw/ecl_yaw_controller.cpp b/src/lib/ecl/attitude_fw/ecl_yaw_controller.cpp
index e53ffc644..79184e2cd 100644
--- a/src/lib/ecl/attitude_fw/ecl_yaw_controller.cpp
+++ b/src/lib/ecl/attitude_fw/ecl_yaw_controller.cpp
@@ -58,9 +58,9 @@ ECL_YawController::ECL_YawController() :
 	_rate_error(0.0f),
 	_rate_setpoint(0.0f),
 	_bodyrate_setpoint(0.0f),
-	_coordinated_min_speed(1.0f)
+	_coordinated_min_speed(1.0f),
+	_nonfinite_input_perf(perf_alloc(PC_COUNT, "fw att control yaw nonfinite input"))
 {
-	perf_alloc(PC_COUNT, "fw att control yaw nonfinite input");
 }
 
 ECL_YawController::~ECL_YawController()
diff --git a/src/modules/fw_att_control/fw_att_control_params.c b/src/modules/fw_att_control/fw_att_control_params.c
index aa637e207..7cae84678 100644
--- a/src/modules/fw_att_control/fw_att_control_params.c
+++ b/src/modules/fw_att_control/fw_att_control_params.c
@@ -50,149 +50,322 @@ f *   Copyright (c) 2013 PX4 Development Team. All rights reserved.
  * Controller parameters, accessible via MAVLink
  *
  */
-// @DisplayName		Attitude Time Constant
-// @Description		This defines the latency between a step input and the achieved setpoint (inverse to a P gain). Half a second is a good start value and fits for most average systems. Smaller systems may require smaller values, but as this will wear out servos faster, the value should only be decreased as needed.
-// @Range		0.4 to 1.0 seconds, in tens of seconds
+
+/**
+ * Attitude Time Constant
+ *
+ * This defines the latency between a step input and the achieved setpoint
+ * (inverse to a P gain). Half a second is a good start value and fits for
+ * most average systems. Smaller systems may require smaller values, but as
+ * this will wear out servos faster, the value should only be decreased as
+ * needed.
+ *
+ * @unit seconds
+ * @min 0.4
+ * @max 1.0
+ * @group FW Attitude Control
+ */
 PARAM_DEFINE_FLOAT(FW_ATT_TC, 0.5f);
 
-// @DisplayName		Pitch rate proportional gain.
-// @Description		This defines how much the elevator input will be commanded depending on the current body angular rate error.
-// @Range		10 to 200, 1 increments
+/**
+ * Pitch rate proportional gain.
+ *
+ * This defines how much the elevator input will be commanded depending on the
+ * current body angular rate error.
+ *
+ * @group FW Attitude Control
+ */
 PARAM_DEFINE_FLOAT(FW_PR_P, 0.05f);
 
-// @DisplayName		Pitch rate integrator gain.
-// @Description		This gain defines how much control response will result out of a steady state error. It trims any constant error.
-// @Range		0 to 50.0
+/**
+ * Pitch rate integrator gain.
+ *
+ * This gain defines how much control response will result out of a steady
+ * state error. It trims any constant error.
+ *
+ * @min 0.0
+ * @max 50.0
+ * @group FW Attitude Control
+ */
 PARAM_DEFINE_FLOAT(FW_PR_I, 0.0f);
 
-// @DisplayName		Maximum positive / up pitch rate.
-// @Description		This limits the maximum pitch up angular rate the controller will output (in degrees per second). Setting a value of zero disables the limit.
-// @Range		0 to 90.0 degrees per seconds, in 1 increments
+/**
+ * Maximum positive / up pitch rate.
+ *
+ * This limits the maximum pitch up angular rate the controller will output (in
+ * degrees per second). Setting a value of zero disables the limit.
+ *
+ * @unit deg/s
+ * @min 0.0
+ * @max 90.0
+ * @group FW Attitude Control
+ */
 PARAM_DEFINE_FLOAT(FW_P_RMAX_POS, 0.0f);
 
-// @DisplayName		Maximum negative / down pitch rate.
-// @Description		This limits the maximum pitch down up angular rate the controller will output (in degrees per second). Setting a value of zero disables the limit.
-// @Range		0 to 90.0 degrees per seconds, in 1 increments
+/**
+ * Maximum negative / down pitch rate.
+ *
+ * This limits the maximum pitch down up angular rate the controller will
+ * output (in degrees per second). Setting a value of zero disables the limit.
+ *
+ * @unit deg/s
+ * @min 0.0
+ * @max 90.0
+ * @group FW Attitude Control
+ */
 PARAM_DEFINE_FLOAT(FW_P_RMAX_NEG, 0.0f);
 
-// @DisplayName		Pitch rate integrator limit
-// @Description		The portion of the integrator part in the control surface deflection is limited to this value
-// @Range		0.0 to 1
-// @Increment		0.1
+/**
+ * Pitch rate integrator limit
+ *
+ * The portion of the integrator part in the control surface deflection is
+ * limited to this value
+ *
+ * @min 0.0
+ * @max 1.0
+ * @group FW Attitude Control
+ */
 PARAM_DEFINE_FLOAT(FW_PR_IMAX, 0.2f);
 
-// @DisplayName		Roll to Pitch feedforward gain.
-// @Description		This compensates during turns and ensures the nose stays level.
-// @Range		0.5 2.0
-// @Increment		0.05
-// @User		User
+/**
+ * Roll to Pitch feedforward gain.
+ *
+ * This compensates during turns and ensures the nose stays level.
+ *
+ * @min 0.0
+ * @max 2.0
+ * @group FW Attitude Control
+ */
 PARAM_DEFINE_FLOAT(FW_P_ROLLFF, 0.0f); //xxx: set to 0 as default, see comment in ECL_PitchController::control_attitude (float turn_offset = ...)
 
-// @DisplayName		Roll rate proportional Gain.
-// @Description		This defines how much the aileron input will be commanded depending on the current body angular rate error.
-// @Range		10.0 200.0
-// @Increment		10.0
-// @User		User
+/**
+ * Roll rate proportional Gain
+ *
+ * This defines how much the aileron input will be commanded depending on the
+ * current body angular rate error.
+ *
+ * @group FW Attitude Control
+ */
 PARAM_DEFINE_FLOAT(FW_RR_P, 0.05f);
 
-// @DisplayName		Roll rate integrator Gain
-// @Description		This gain defines how much control response will result out of a steady state error. It trims any constant error.
-// @Range		0.0 100.0
-// @Increment		5.0
-// @User		User
+/**
+ * Roll rate integrator Gain
+ *
+ * This gain defines how much control response will result out of a steady
+ * state error. It trims any constant error.
+ *
+ * @min 0.0
+ * @max 100.0
+ * @group FW Attitude Control
+ */
 PARAM_DEFINE_FLOAT(FW_RR_I, 0.0f);
 
-// @DisplayName		Roll Integrator Anti-Windup
-// @Description		The portion of the integrator part in the control surface deflection is limited to this value.
-// @Range		0.0 to 1.0
-// @Increment		0.1
+/**
+ * Roll Integrator Anti-Windup
+ *
+ * The portion of the integrator part in the control surface deflection is limited to this value.
+ *
+ * @min 0.0
+ * @max 1.0
+ * @group FW Attitude Control
+ */
 PARAM_DEFINE_FLOAT(FW_RR_IMAX, 0.2f);
 
-// @DisplayName		Maximum Roll Rate
-// @Description		This limits the maximum roll rate the controller will output (in degrees per second). Setting a value of zero disables the limit.
-// @Range		0 to 90.0 degrees per seconds
-// @Increment		1.0
-PARAM_DEFINE_FLOAT(FW_R_RMAX, 0);
+/**
+ * Maximum Roll Rate
+ *
+ * This limits the maximum roll rate the controller will output (in degrees per
+ * second). Setting a value of zero disables the limit.
+ *
+ * @unit deg/s
+ * @min 0.0
+ * @max 90.0
+ * @group FW Attitude Control
+ */
+PARAM_DEFINE_FLOAT(FW_R_RMAX, 0.0f);
 
-// @DisplayName		Yaw rate proportional gain.
-// @Description		This defines how much the rudder input will be commanded depending on the current body angular rate error.
-// @Range		10 to 200, 1 increments
-PARAM_DEFINE_FLOAT(FW_YR_P, 0.05);
+/**
+ * Yaw rate proportional gain
+ *
+ * This defines how much the rudder input will be commanded depending on the
+ * current body angular rate error.
+ *
+ * @group FW Attitude Control
+ */
+PARAM_DEFINE_FLOAT(FW_YR_P, 0.05f);
 
-// @DisplayName		Yaw rate integrator gain.
-// @Description		This gain defines how much control response will result out of a steady state error. It trims any constant error.
-// @Range		0 to 50.0
+/**
+ * Yaw rate integrator gain
+ *
+ * This gain defines how much control response will result out of a steady
+ * state error. It trims any constant error.
+ *
+ * @min 0.0
+ * @max 50.0
+ * @group FW Attitude Control
+ */
 PARAM_DEFINE_FLOAT(FW_YR_I, 0.0f);
 
-// @DisplayName		Yaw rate integrator limit
-// @Description		The portion of the integrator part in the control surface deflection is limited to this value
-// @Range		0.0 to 1
-// @Increment		0.1
+/**
+ * Yaw rate integrator limit
+ *
+ * The portion of the integrator part in the control surface deflection is
+ * limited to this value
+ *
+ * @min 0.0
+ * @max 1.0
+ * @group FW Attitude Control
+ */
 PARAM_DEFINE_FLOAT(FW_YR_IMAX, 0.2f);
 
-// @DisplayName		Maximum Yaw Rate
-// @Description		This limits the maximum yaw rate the controller will output (in degrees per second). Setting a value of zero disables the limit.
-// @Range		0 to 90.0 degrees per seconds
-// @Increment		1.0
-PARAM_DEFINE_FLOAT(FW_Y_RMAX, 0);
+/**
+ * Maximum Yaw Rate
+ *
+ * This limits the maximum yaw rate the controller will output (in degrees per
+ * second). Setting a value of zero disables the limit.
+ *
+ * @unit deg/s
+ * @min 0.0
+ * @max 90.0
+ * @group FW Attitude Control
+ */
+PARAM_DEFINE_FLOAT(FW_Y_RMAX, 0.0f);
 
-// @DisplayName		Roll rate feed forward
-// @Description		Direct feed forward from rate setpoint to control surface output
-// @Range		0 to 10
-// @Increment		0.1
+/**
+ * Roll rate feed forward
+ *
+ * Direct feed forward from rate setpoint to control surface output
+ *
+ * @min 0.0
+ * @max 10.0
+ * @group FW Attitude Control
+ */
 PARAM_DEFINE_FLOAT(FW_RR_FF, 0.3f);
 
-// @DisplayName		Pitch rate feed forward
-// @Description		Direct feed forward from rate setpoint to control surface output
-// @Range		0 to 10
-// @Increment		0.1
+/**
+ * Pitch rate feed forward
+ *
+ * Direct feed forward from rate setpoint to control surface output
+ *
+ * @min 0.0
+ * @max 10.0
+ * @group FW Attitude Control
+ */
 PARAM_DEFINE_FLOAT(FW_PR_FF, 0.4f);
 
-// @DisplayName		Yaw rate feed forward
-// @Description		Direct feed forward from rate setpoint to control surface output
-// @Range		0 to 10
-// @Increment		0.1
+/**
+ * Yaw rate feed forward
+ *
+ * Direct feed forward from rate setpoint to control surface output
+ *
+ * @min 0.0
+ * @max 10.0
+ * @group FW Attitude Control
+ */
 PARAM_DEFINE_FLOAT(FW_YR_FF, 0.3f);
 
-// @DisplayName		Minimal speed for yaw coordination
-// @Description		For airspeeds above this value the yaw rate is calculated for a coordinated turn. Set to a very high value to disable.
-// @Range		0 to 90.0 degrees per seconds
-// @Increment		1.0
+/**
+ * Minimal speed for yaw coordination
+ *
+ * For airspeeds above this value, the yaw rate is calculated for a coordinated
+ * turn. Set to a very high value to disable.
+ *
+ * @unit m/s
+ * @group FW Attitude Control
+ */
 PARAM_DEFINE_FLOAT(FW_YCO_VMIN, 1000.0f);
 
-/* Airspeed parameters: the following parameters about airspeed are used by the attitude and the positon controller */
+/* Airspeed parameters:
+ * The following parameters about airspeed are used by the attitude and the
+ * position controller.
+ * */
 
-// @DisplayName		Minimum Airspeed
-// @Description		If the airspeed falls below this value the TECS controller will try to increase airspeed more aggressively
-// @Range		0.0 to 30
+/**
+ * Minimum Airspeed
+ *
+ * If the airspeed falls below this value, the TECS controller will try to
+ * increase airspeed more aggressively.
+ *
+ * @unit m/s
+ * @min 0.0
+ * @max 30.0
+ * @group FW Attitude Control
+ */
 PARAM_DEFINE_FLOAT(FW_AIRSPD_MIN, 13.0f);
 
-// @DisplayName		Trim Airspeed
-// @Description		The TECS controller tries to fly at this airspeed
-// @Range		0.0 to 30
+/**
+ * Trim Airspeed
+ *
+ * The TECS controller tries to fly at this airspeed.
+ *
+ * @unit m/s
+ * @min 0.0
+ * @max 30.0
+ * @group FW Attitude Control
+ */
 PARAM_DEFINE_FLOAT(FW_AIRSPD_TRIM, 20.0f);
 
-// @DisplayName		Maximum Airspeed
-// @Description		If the airspeed is above this value the TECS controller will try to decrease airspeed more aggressively
-// @Range		0.0 to 30
+/**
+ * Maximum Airspeed
+ *
+ * If the airspeed is above this value, the TECS controller will try to decrease
+ * airspeed more aggressively.
+ *
+ * @unit m/s
+ * @min 0.0
+ * @max 30.0
+ * @group FW Attitude Control
+ */
 PARAM_DEFINE_FLOAT(FW_AIRSPD_MAX, 50.0f);
 
-// @DisplayName		Roll Setpoint Offset
-// @Description		An airframe specific offset of the roll setpoint in degrees, the value is added to the roll setpoint and should correspond to the typical cruise speed of the airframe
-// @Range		-90.0 to 90.0
+/**
+ * Roll Setpoint Offset
+ *
+ * An airframe specific offset of the roll setpoint in degrees, the value is
+ * added to the roll setpoint and should correspond to the typical cruise speed
+ * of the airframe.
+ *
+ * @unit deg
+ * @min -90.0
+ * @max 90.0
+ * @group FW Attitude Control
+ */
 PARAM_DEFINE_FLOAT(FW_RSP_OFF, 0.0f);
 
-// @DisplayName		Pitch Setpoint Offset
-// @Description		An airframe specific offset of the pitch setpoint in degrees, the value is added to the pitch setpoint and should correspond to the typical cruise speed of the airframe
-// @Range		-90.0 to 90.0
+/**
+ * Pitch Setpoint Offset
+ *
+ * An airframe specific offset of the pitch setpoint in degrees, the value is
+ * added to the pitch setpoint and should correspond to the typical cruise
+ * speed of the airframe.
+ *
+ * @unit deg
+ * @min -90.0
+ * @max 90.0
+ * @group FW Attitude Control
+ */
 PARAM_DEFINE_FLOAT(FW_PSP_OFF, 0.0f);
 
-// @DisplayName		Max Manual Roll
-// @Description		Max roll for manual control in attitude stabilized mode
-// @Range		0.0 to 90.0
+/**
+ * Max Manual Roll
+ *
+ * Max roll for manual control in attitude stabilized mode
+ *
+ * @unit deg
+ * @min 0.0
+ * @max 90.0
+ * @group FW Attitude Control
+ */
 PARAM_DEFINE_FLOAT(FW_MAN_R_MAX, 45.0f);
 
-// @DisplayName		Max Manual Pitch
-// @Description		Max pitch for manual control in attitude stabilized mode
-// @Range		0.0 to 90.0
+/**
+ * Max Manual Pitch
+ *
+ * Max pitch for manual control in attitude stabilized mode
+ *
+ * @unit deg
+ * @min 0.0
+ * @max 90.0
+ * @group FW Attitude Control
+ */
 PARAM_DEFINE_FLOAT(FW_MAN_P_MAX, 45.0f);
diff --git a/src/modules/fw_pos_control_l1/fw_pos_control_l1_main.cpp b/src/modules/fw_pos_control_l1/fw_pos_control_l1_main.cpp
index fe4eb66a9..5df17e2ec 100644
--- a/src/modules/fw_pos_control_l1/fw_pos_control_l1_main.cpp
+++ b/src/modules/fw_pos_control_l1/fw_pos_control_l1_main.cpp
@@ -1456,7 +1456,7 @@ void FixedwingPositionControl::tecs_update_pitch_throttle(float alt_sp, float v_
 		if (ground_speed_length > FLT_EPSILON) {
 			flightPathAngle = -asinf(ground_speed(2)/ground_speed_length);
 		}
-		fwPosctrl::mTecs::LimitOverride limitOverride;
+		fwPosctrl::LimitOverride limitOverride;
 		if (climbout_mode) {
 			limitOverride.enablePitchMinOverride(M_RAD_TO_DEG_F * climbout_pitch_min_rad);
 		} else {
diff --git a/src/modules/fw_pos_control_l1/module.mk b/src/modules/fw_pos_control_l1/module.mk
index c887223f4..af155fe08 100644
--- a/src/modules/fw_pos_control_l1/module.mk
+++ b/src/modules/fw_pos_control_l1/module.mk
@@ -41,4 +41,5 @@ SRCS		= fw_pos_control_l1_main.cpp \
 		  fw_pos_control_l1_params.c \
 		  landingslope.cpp \
 		  mtecs/mTecs.cpp \
+		  mtecs/limitoverride.cpp \
 		  mtecs/mTecs_params.c
diff --git a/src/modules/fw_pos_control_l1/mtecs/limitoverride.cpp b/src/modules/fw_pos_control_l1/mtecs/limitoverride.cpp
new file mode 100644
index 000000000..58795edb6
--- /dev/null
+++ b/src/modules/fw_pos_control_l1/mtecs/limitoverride.cpp
@@ -0,0 +1,71 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2013 PX4 Development Team. All rights reserved.
+ *   Author: 	@author Thomas Gubler <thomasgubler@gmail.com>
+ *
+ * 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 limitoverride.cpp
+ *
+ * @author Thomas Gubler <thomasgubler@gmail.com>
+ */
+
+#include "limitoverride.h"
+
+namespace fwPosctrl {
+
+bool LimitOverride::applyOverride(BlockOutputLimiter &outputLimiterThrottle,
+		BlockOutputLimiter &outputLimiterPitch)
+{
+	bool ret = false;
+
+	if (overrideThrottleMinEnabled)	{
+		outputLimiterThrottle.setMin(overrideThrottleMin);
+		ret = true;
+	}
+	if (overrideThrottleMaxEnabled)	{
+		outputLimiterThrottle.setMax(overrideThrottleMax);
+		ret = true;
+	}
+	if (overridePitchMinEnabled)	{
+		outputLimiterPitch.setMin(overridePitchMin);
+		ret = true;
+	}
+	if (overridePitchMaxEnabled)	{
+		outputLimiterPitch.setMax(overridePitchMax);
+		ret = true;
+	}
+
+	return ret;
+}
+
+} /* namespace fwPosctrl */
diff --git a/src/modules/fw_pos_control_l1/mtecs/limitoverride.h b/src/modules/fw_pos_control_l1/mtecs/limitoverride.h
new file mode 100644
index 000000000..64c2e7bbd
--- /dev/null
+++ b/src/modules/fw_pos_control_l1/mtecs/limitoverride.h
@@ -0,0 +1,107 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2013 PX4 Development Team. All rights reserved.
+ *   Author: 	@author Thomas Gubler <thomasgubler@gmail.com>
+ *
+ * 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 limitoverride.h
+ *
+ * @author Thomas Gubler <thomasgubler@gmail.com>
+ */
+
+
+#ifndef LIMITOVERRIDE_H_
+#define LIMITOVERRIDE_H_
+
+#include "mTecs_blocks.h"
+
+namespace fwPosctrl
+{
+
+/* A small class which provides helper functions to override control output limits which are usually set by
+* parameters in special cases
+*/
+class LimitOverride
+{
+public:
+	LimitOverride() :
+		overrideThrottleMinEnabled(false),
+		overrideThrottleMaxEnabled(false),
+		overridePitchMinEnabled(false),
+		overridePitchMaxEnabled(false)
+	{};
+
+	~LimitOverride() {};
+
+	/*
+	* Override the limits of the outputlimiter instances given by the arguments with the limits saved in
+	* this class (if enabled)
+	* @return true if the limit was applied
+	*/
+	bool applyOverride(BlockOutputLimiter &outputLimiterThrottle,
+			BlockOutputLimiter &outputLimiterPitch);
+
+	/* Functions to enable or disable the override */
+	void enableThrottleMinOverride(float value) { enable(&overrideThrottleMinEnabled,
+			&overrideThrottleMin, value); }
+	void disableThrottleMinOverride() { disable(&overrideThrottleMinEnabled); }
+	void enableThrottleMaxOverride(float value) { enable(&overrideThrottleMaxEnabled,
+			&overrideThrottleMax, value); }
+	void disableThrottleMaxOverride() { disable(&overrideThrottleMaxEnabled); }
+	void enablePitchMinOverride(float value) { enable(&overridePitchMinEnabled,
+			&overridePitchMin, value); }
+	void disablePitchMinOverride() { disable(&overridePitchMinEnabled); }
+	void enablePitchMaxOverride(float value) { enable(&overridePitchMaxEnabled,
+			&overridePitchMax, value); }
+	void disablePitchMaxOverride() { disable(&overridePitchMaxEnabled); }
+
+protected:
+	bool overrideThrottleMinEnabled;
+	float overrideThrottleMin;
+	bool overrideThrottleMaxEnabled;
+	float overrideThrottleMax;
+	bool overridePitchMinEnabled;
+	float overridePitchMin; //in degrees (replaces param values)
+	bool overridePitchMaxEnabled;
+	float overridePitchMax; //in degrees (replaces param values)
+
+	/* Enable a specific limit override */
+	void enable(bool *flag, float *limit, float value) { *flag = true; *limit = value; };
+
+	/* Disable a specific limit override */
+	void disable(bool *flag) { *flag = false; };
+};
+
+} /* namespace fwPosctrl */
+
+#endif /* LIMITOVERRIDE_H_ */
diff --git a/src/modules/fw_pos_control_l1/mtecs/mTecs.cpp b/src/modules/fw_pos_control_l1/mtecs/mTecs.cpp
index 32f9f19ca..03353cbc1 100644
--- a/src/modules/fw_pos_control_l1/mtecs/mTecs.cpp
+++ b/src/modules/fw_pos_control_l1/mtecs/mTecs.cpp
@@ -58,6 +58,7 @@ mTecs::mTecs() :
 	_controlEnergyDistribution(this, "PIT", true),
 	_controlAltitude(this, "FPA", true),
 	_controlAirSpeed(this, "ACC"),
+	_airspeedLowpass(this, "A_LP"),
 	_airspeedDerivative(this, "AD"),
 	_throttleSp(0.0f),
 	_pitchSp(0.0f),
@@ -122,12 +123,18 @@ int mTecs::updateFlightPathAngleSpeed(float flightPathAngle, float flightPathAng
 	/* time measurement */
 	updateTimeMeasurement();
 
+	/* Filter arispeed */
+	float airspeedFiltered = _airspeedLowpass.update(airspeed);
+
 	/* calculate longitudinal acceleration setpoint from airspeed setpoint*/
-	float accelerationLongitudinalSp = _controlAirSpeed.update(airspeedSp - airspeed);
+	float accelerationLongitudinalSp = _controlAirSpeed.update(airspeedSp - airspeedFiltered);
 
 	/* Debug output */
 	if (_counter % 10 == 0) {
-		debug("updateFlightPathAngleSpeed airspeedSp %.4f, airspeed %.4f, accelerationLongitudinalSp%.4f", (double)airspeedSp, (double)airspeed, (double)accelerationLongitudinalSp);
+		debug("updateFlightPathAngleSpeed airspeedSp %.4f, airspeed %.4f airspeedFiltered %.4f,"
+				"accelerationLongitudinalSp%.4f",
+				(double)airspeedSp, (double)airspeed,
+				(double)airspeedFiltered, (double)accelerationLongitudinalSp);
 	}
 
 	/* Write part of the status message */
@@ -135,19 +142,20 @@ int mTecs::updateFlightPathAngleSpeed(float flightPathAngle, float flightPathAng
 	_status.flightPathAngle = flightPathAngle;
 	_status.airspeedSp = airspeedSp;
 	_status.airspeed = airspeed;
+	_status.airspeedFiltered = airspeedFiltered;
 
 
 	/* use longitudinal acceleration setpoint for total energy control */
-	return updateFlightPathAngleAcceleration(flightPathAngle, flightPathAngleSp, airspeed,
+	return updateFlightPathAngleAcceleration(flightPathAngle, flightPathAngleSp, airspeedFiltered,
 			accelerationLongitudinalSp, mode, limitOverride);
 }
 
-int mTecs::updateFlightPathAngleAcceleration(float flightPathAngle, float flightPathAngleSp, float airspeed,
+int mTecs::updateFlightPathAngleAcceleration(float flightPathAngle, float flightPathAngleSp, float airspeedFiltered,
 		float accelerationLongitudinalSp, tecs_mode mode, LimitOverride limitOverride)
 {
 	/* check if all input arguments are numbers and abort if not so */
 	if (!isfinite(flightPathAngle) || !isfinite(flightPathAngleSp) ||
-			!isfinite(airspeed) || !isfinite(accelerationLongitudinalSp) || !isfinite(mode)) {
+			!isfinite(airspeedFiltered) || !isfinite(accelerationLongitudinalSp) || !isfinite(mode)) {
 		return -1;
 	}
 	/* time measurement */
@@ -160,7 +168,7 @@ int mTecs::updateFlightPathAngleAcceleration(float flightPathAngle, float flight
 	float flightPathAngleError = flightPathAngleSp - flightPathAngle;
 	float airspeedDerivative = 0.0f;
 	if(_airspeedDerivative.getDt() > 0.0f) {
-		airspeedDerivative = _airspeedDerivative.update(airspeed);
+		airspeedDerivative = _airspeedDerivative.update(airspeedFiltered);
 	}
 	float airspeedDerivativeNorm = airspeedDerivative / CONSTANTS_ONE_G;
 	float airspeedDerivativeSp = accelerationLongitudinalSp;
@@ -186,7 +194,7 @@ int mTecs::updateFlightPathAngleAcceleration(float flightPathAngle, float flight
 	}
 
 	/* Check airspeed: if below safe value switch to underspeed mode (if not in land or takeoff mode) */
-	if (mode != TECS_MODE_LAND && mode != TECS_MODE_TAKEOFF && airspeed < _airspeedMin.get()) {
+	if (mode != TECS_MODE_LAND && mode != TECS_MODE_TAKEOFF && airspeedFiltered < _airspeedMin.get()) {
 		mode = TECS_MODE_UNDERSPEED;
 	}
 
@@ -302,29 +310,4 @@ void mTecs::debug(const char *fmt, ...) {
 	debug_print(fmt, args);
 }
 
-bool mTecs::LimitOverride::applyOverride(BlockOutputLimiter &outputLimiterThrottle,
-		BlockOutputLimiter &outputLimiterPitch)
-{
-	bool ret = false;
-
-	if (overrideThrottleMinEnabled)	{
-		outputLimiterThrottle.setMin(overrideThrottleMin);
-		ret = true;
-	}
-	if (overrideThrottleMaxEnabled)	{
-		outputLimiterThrottle.setMax(overrideThrottleMax);
-		ret = true;
-	}
-	if (overridePitchMinEnabled)	{
-		outputLimiterPitch.setMin(overridePitchMin);
-		ret = true;
-	}
-	if (overridePitchMaxEnabled)	{
-		outputLimiterPitch.setMax(overridePitchMax);
-		ret = true;
-	}
-
-	return ret;
-}
-
 } /* namespace fwPosctrl */
diff --git a/src/modules/fw_pos_control_l1/mtecs/mTecs.h b/src/modules/fw_pos_control_l1/mtecs/mTecs.h
index ddd6583e8..c102f5dee 100644
--- a/src/modules/fw_pos_control_l1/mtecs/mTecs.h
+++ b/src/modules/fw_pos_control_l1/mtecs/mTecs.h
@@ -44,6 +44,7 @@
 #define MTECS_H_
 
 #include "mTecs_blocks.h"
+#include "limitoverride.h"
 
 #include <controllib/block/BlockParam.hpp>
 #include <drivers/drv_hrt.h>
@@ -60,62 +61,6 @@ public:
 	mTecs();
 	virtual ~mTecs();
 
-	/* A small class which provides helper fucntions to override control output limits which are usually set by
-	 * parameters in special cases
-	 */
-	class LimitOverride
-	{
-	public:
-		LimitOverride() :
-			overrideThrottleMinEnabled(false),
-			overrideThrottleMaxEnabled(false),
-			overridePitchMinEnabled(false),
-			overridePitchMaxEnabled(false)
-		{};
-
-		~LimitOverride() {};
-
-		/*
-		 * Override the limits of the outputlimiter instances given by the arguments with the limits saved in
-		 * this class (if enabled)
-		 * @return true if the limit was applied
-		 */
-		bool applyOverride(BlockOutputLimiter &outputLimiterThrottle,
-				BlockOutputLimiter &outputLimiterPitch);
-
-		/* Functions to enable or disable the override */
-		void enableThrottleMinOverride(float value) { enable(&overrideThrottleMinEnabled,
-				&overrideThrottleMin, value); }
-		void disableThrottleMinOverride() { disable(&overrideThrottleMinEnabled); }
-		void enableThrottleMaxOverride(float value) { enable(&overrideThrottleMaxEnabled,
-				&overrideThrottleMax, value); }
-		void disableThrottleMaxOverride() { disable(&overrideThrottleMaxEnabled); }
-		void enablePitchMinOverride(float value) { enable(&overridePitchMinEnabled,
-				&overridePitchMin, value); }
-		void disablePitchMinOverride() { disable(&overridePitchMinEnabled); }
-		void enablePitchMaxOverride(float value) { enable(&overridePitchMaxEnabled,
-				&overridePitchMax, value); }
-		void disablePitchMaxOverride() { disable(&overridePitchMaxEnabled); }
-
-	protected:
-		bool overrideThrottleMinEnabled;
-		float overrideThrottleMin;
-		bool overrideThrottleMaxEnabled;
-		float overrideThrottleMax;
-		bool overridePitchMinEnabled;
-		float overridePitchMin; //in degrees (replaces param values)
-		bool overridePitchMaxEnabled;
-		float overridePitchMax; //in degrees (replaces param values)
-
-		/* Enable a specific limit override */
-		void enable(bool *flag, float *limit, float value) { *flag = true; *limit = value;
-		};
-		/* Disable a specific limit override */
-		void disable(bool *flag) { *flag = false; };
-
-
-	};
-
 	/*
 	 * Control in altitude setpoint and speed mode
 	 */
@@ -131,7 +76,7 @@ public:
 	/*
 	 * Control in flightPathAngle setpoint (flollow a slope etc.) and acceleration mode (base case)
 	 */
-	int updateFlightPathAngleAcceleration(float flightPathAngle, float flightPathAngleSp, float airspeed,
+	int updateFlightPathAngleAcceleration(float flightPathAngle, float flightPathAngleSp, float airspeedFiltered,
 			float accelerationLongitudinalSp, tecs_mode mode, LimitOverride limitOverride);
 
 	/*
@@ -145,9 +90,10 @@ public:
 	void resetDerivatives(float airspeed);
 
 	/* Accessors */
-	bool getEnabled() {return _mTecsEnabled.get() > 0;}
-	float getThrottleSetpoint() {return _throttleSp;}
-	float getPitchSetpoint() {return _pitchSp;}
+	bool getEnabled() { return _mTecsEnabled.get() > 0; }
+	float getThrottleSetpoint() { return _throttleSp; }
+	float getPitchSetpoint() { return _pitchSp; }
+	float airspeedLowpassUpdate(float input) { return _airspeedLowpass.update(input); }
 
 protected:
 	/* parameters */
@@ -160,11 +106,12 @@ protected:
 	/* control blocks */
 	BlockFFPILimitedCustom _controlTotalEnergy;		/**< FFPI controller for total energy control: output is throttle */
 	BlockFFPILimitedCustom _controlEnergyDistribution;	/**< FFPI controller for energy distribution control: output is pitch */
-	BlockPDLimited	_controlAltitude;		/**< P controller for altitude: output is the flight path angle setpoint */
-	BlockPLimited	_controlAirSpeed;			/**< P controller for airspeed: output is acceleration setpoint */
+	BlockPDLimited	_controlAltitude;		/**< PD controller for altitude: output is the flight path angle setpoint */
+	BlockPDLimited	_controlAirSpeed;			/**< PD controller for airspeed: output is acceleration setpoint */
 
 	/* Other calculation Blocks */
-	control::BlockDerivative _airspeedDerivative;
+	control::BlockLowPass _airspeedLowpass;		/**< low pass filter for airspeed */
+	control::BlockDerivative _airspeedDerivative;	/**< airspeed derivative calulation */
 
 	/* Output setpoints */
 	float _throttleSp;				/**< Throttle Setpoint from 0 to 1 */
diff --git a/src/modules/fw_pos_control_l1/mtecs/mTecs_params.c b/src/modules/fw_pos_control_l1/mtecs/mTecs_params.c
index 39514b223..c95bf1dc9 100644
--- a/src/modules/fw_pos_control_l1/mtecs/mTecs_params.c
+++ b/src/modules/fw_pos_control_l1/mtecs/mTecs_params.c
@@ -222,6 +222,12 @@ PARAM_DEFINE_FLOAT(MT_FPA_MIN, -10.0f);
  */
 PARAM_DEFINE_FLOAT(MT_FPA_MAX, 30.0f);
 
+/**
+ * Lowpass (cutoff freq.) for airspeed
+ *
+ * @group mTECS
+ */
+PARAM_DEFINE_FLOAT(MT_A_LP, 1.0f);
 
 /**
  * P gain for the airspeed control
@@ -234,6 +240,23 @@ PARAM_DEFINE_FLOAT(MT_FPA_MAX, 30.0f);
 PARAM_DEFINE_FLOAT(MT_ACC_P, 1.5f);
 
 /**
+ * D gain for the airspeed control
+ * Maps the change of airspeed error to the acceleration setpoint
+ *
+ * @min 0.0f
+ * @max 10.0f
+ * @group mTECS
+ */
+PARAM_DEFINE_FLOAT(MT_ACC_D, 0.0f);
+
+/**
+ * Lowpass for ACC error derivative calculation (see MT_ACC_D)
+ *
+ * @group mTECS
+ */
+PARAM_DEFINE_FLOAT(MT_ACC_D_LP, 1.0f);
+
+/**
  * Minimal acceleration (air)
  *
  * @unit m/s^2
diff --git a/src/modules/mavlink/mavlink_messages.cpp b/src/modules/mavlink/mavlink_messages.cpp
index fd41b723a..d94e7fc7e 100644
--- a/src/modules/mavlink/mavlink_messages.cpp
+++ b/src/modules/mavlink/mavlink_messages.cpp
@@ -938,14 +938,14 @@ protected:
 
 	void send(const hrt_abstime t)
 	{
-		if (pos_sp_triplet_sub->update(t)) {
-			mavlink_msg_global_position_setpoint_int_send(_channel,
-					MAV_FRAME_GLOBAL,
-					(int32_t)(pos_sp_triplet->current.lat * 1e7),
-					(int32_t)(pos_sp_triplet->current.lon * 1e7),
-					(int32_t)(pos_sp_triplet->current.alt * 1000),
-					(int16_t)(pos_sp_triplet->current.yaw * M_RAD_TO_DEG_F * 100.0f));
-		}
+		/* always send this message, even if it has not been updated */
+		pos_sp_triplet_sub->update(t);
+		mavlink_msg_global_position_setpoint_int_send(_channel,
+			MAV_FRAME_GLOBAL,
+			(int32_t)(pos_sp_triplet->current.lat * 1e7),
+			(int32_t)(pos_sp_triplet->current.lon * 1e7),
+			(int32_t)(pos_sp_triplet->current.alt * 1000),
+			(int16_t)(pos_sp_triplet->current.yaw * M_RAD_TO_DEG_F * 100.0f));
 	}
 };
 
diff --git a/src/modules/position_estimator_inav/position_estimator_inav_main.c b/src/modules/position_estimator_inav/position_estimator_inav_main.c
index d7503e42d..f908d7a3b 100644
--- a/src/modules/position_estimator_inav/position_estimator_inav_main.c
+++ b/src/modules/position_estimator_inav/position_estimator_inav_main.c
@@ -71,19 +71,20 @@
 #include "inertial_filter.h"
 
 #define MIN_VALID_W 0.00001f
+#define PUB_INTERVAL 10000	// limit publish rate to 100 Hz
+#define EST_BUF_SIZE 250000 / PUB_INTERVAL		// buffer size is 0.5s
 
 static bool thread_should_exit = false; /**< Deamon exit flag */
 static bool thread_running = false; /**< Deamon status flag */
 static int position_estimator_inav_task; /**< Handle of deamon task / thread */
 static bool verbose_mode = false;
 
-static const hrt_abstime gps_topic_timeout = 1000000;		// GPS topic timeout = 1s
+static const hrt_abstime gps_topic_timeout = 500000;		// GPS topic timeout = 0.5s
 static const hrt_abstime flow_topic_timeout = 1000000;	// optical flow topic timeout = 1s
 static const hrt_abstime sonar_timeout = 150000;	// sonar timeout = 150ms
 static const hrt_abstime sonar_valid_timeout = 1000000;	// estimate sonar distance during this time after sonar loss
 static const hrt_abstime xy_src_timeout = 2000000;	// estimate position during this time after position sources loss
 static const uint32_t updates_counter_len = 1000000;
-static const uint32_t pub_interval = 10000;	// limit publish rate to 100 Hz
 static const float max_flow = 1.0f;	// max flow value that can be used, rad/s
 
 __EXPORT int position_estimator_inav_main(int argc, char *argv[]);
@@ -92,6 +93,16 @@ int position_estimator_inav_thread_main(int argc, char *argv[]);
 
 static void usage(const char *reason);
 
+static inline int min(int val1, int val2)
+{
+	return (val1 < val2) ? val1 : val2;
+}
+
+static inline int max(int val1, int val2)
+{
+	return (val1 > val2) ? val1 : val2;
+}
+
 /**
  * Print the correct usage.
  */
@@ -135,7 +146,7 @@ int position_estimator_inav_main(int argc, char *argv[])
 
 		thread_should_exit = false;
 		position_estimator_inav_task = task_spawn_cmd("position_estimator_inav",
-					       SCHED_DEFAULT, SCHED_PRIORITY_MAX - 5, 4000,
+					       SCHED_DEFAULT, SCHED_PRIORITY_MAX - 5, 5000,
 					       position_estimator_inav_thread_main,
 					       (argv) ? (const char **) &argv[2] : (const char **) NULL);
 		exit(0);
@@ -199,8 +210,21 @@ int position_estimator_inav_thread_main(int argc, char *argv[])
 	float y_est[2] = { 0.0f, 0.0f };	// pos, vel
 	float z_est[2] = { 0.0f, 0.0f };	// pos, vel
 
-	float eph = 1.0;
-	float epv = 1.0;
+	float est_buf[EST_BUF_SIZE][3][2];	// estimated position buffer
+	float R_buf[EST_BUF_SIZE][3][3];	// rotation matrix buffer
+	float R_gps[3][3];					// rotation matrix for GPS correction moment
+	memset(est_buf, 0, sizeof(est_buf));
+	memset(R_buf, 0, sizeof(R_buf));
+	memset(R_gps, 0, sizeof(R_gps));
+	int buf_ptr = 0;
+
+	static const float min_eph_epv = 2.0f;	// min EPH/EPV, used for weight calculation
+	static const float max_eph_epv = 20.0f;	// max EPH/EPV acceptable for estimation
+
+	float eph = max_eph_epv;
+	float epv = 1.0f;
+
+	float eph_flow = 1.0f;
 
 	float x_est_prev[2], y_est_prev[2], z_est_prev[2];
 	memset(x_est_prev, 0, sizeof(x_est_prev));
@@ -257,9 +281,6 @@ int position_estimator_inav_thread_main(int argc, char *argv[])
 	float corr_flow[] = { 0.0f, 0.0f };	// N E
 	float w_flow = 0.0f;
 
-	static float min_eph_epv = 2.0f;	// min EPH/EPV, used for weight calculation
-	static float max_eph_epv = 10.0f;	// max EPH/EPV acceptable for estimation
-
 	float sonar_prev = 0.0f;
 	hrt_abstime flow_prev = 0;			// time of last flow measurement
 	hrt_abstime sonar_time = 0;			// time of last sonar measurement (not filtered)
@@ -536,9 +557,10 @@ int position_estimator_inav_thread_main(int argc, char *argv[])
 						w_flow *= 0.05f;
 					}
 
-					flow_valid = true;
+					/* under ideal conditions, on 1m distance assume EPH = 10cm */
+					eph_flow = 0.1 / w_flow;
 
-					eph = fminf(eph, 0.1 / att.R[2][2] / flow_q * fmaxf(1.0f, flow_dist));	// under ideal conditions, on 1m distance assume EPH = 10cm
+					flow_valid = true;
 
 				} else {
 					w_flow = 0.0f;
@@ -597,13 +619,13 @@ int position_estimator_inav_thread_main(int argc, char *argv[])
 
 				/* hysteresis for GPS quality */
 				if (gps_valid) {
-					if (gps.eph_m > max_eph_epv * 1.5f || gps.epv_m > max_eph_epv * 1.5f || gps.fix_type < 3) {
+					if (gps.eph_m > max_eph_epv || gps.epv_m > max_eph_epv || gps.fix_type < 3) {
 						gps_valid = false;
 						mavlink_log_info(mavlink_fd, "[inav] GPS signal lost");
 					}
 
 				} else {
-					if (gps.eph_m < max_eph_epv && gps.epv_m < max_eph_epv && gps.fix_type >= 3) {
+					if (gps.eph_m < max_eph_epv * 0.7f && gps.epv_m < max_eph_epv * 0.7f && gps.fix_type >= 3) {
 						gps_valid = true;
 						reset_est = true;
 						mavlink_log_info(mavlink_fd, "[inav] GPS signal found");
@@ -657,16 +679,22 @@ int position_estimator_inav_thread_main(int argc, char *argv[])
 							y_est[1] = gps.vel_e_m_s;
 						}
 
+						/* calculate index of estimated values in buffer */
+						int est_i = buf_ptr - 1 - min(EST_BUF_SIZE - 1, max(0, (int)(params.delay_gps * 1000000.0f / PUB_INTERVAL)));
+						if (est_i < 0) {
+							est_i += EST_BUF_SIZE;
+						}
+
 						/* calculate correction for position */
-						corr_gps[0][0] = gps_proj[0] - x_est[0];
-						corr_gps[1][0] = gps_proj[1] - y_est[0];
-						corr_gps[2][0] = local_pos.ref_alt - alt - z_est[0];
+						corr_gps[0][0] = gps_proj[0] - est_buf[est_i][0][0];
+						corr_gps[1][0] = gps_proj[1] - est_buf[est_i][1][0];
+						corr_gps[2][0] = local_pos.ref_alt - alt - est_buf[est_i][2][0];
 
 						/* calculate correction for velocity */
 						if (gps.vel_ned_valid) {
-							corr_gps[0][1] = gps.vel_n_m_s - x_est[1];
-							corr_gps[1][1] = gps.vel_e_m_s - y_est[1];
-							corr_gps[2][1] = gps.vel_d_m_s - z_est[1];
+							corr_gps[0][1] = gps.vel_n_m_s - est_buf[est_i][0][1];
+							corr_gps[1][1] = gps.vel_e_m_s - est_buf[est_i][1][1];
+							corr_gps[2][1] = gps.vel_d_m_s - est_buf[est_i][2][1];
 
 						} else {
 							corr_gps[0][1] = 0.0f;
@@ -674,8 +702,8 @@ int position_estimator_inav_thread_main(int argc, char *argv[])
 							corr_gps[2][1] = 0.0f;
 						}
 
-						eph = fminf(eph, gps.eph_m);
-						epv = fminf(epv, gps.epv_m);
+						/* save rotation matrix at this moment */
+						memcpy(R_gps, R_buf[est_i], sizeof(R_gps));
 
 						w_gps_xy = min_eph_epv / fmaxf(min_eph_epv, gps.eph_m);
 						w_gps_z = min_eph_epv / fmaxf(min_eph_epv, gps.epv_m);
@@ -717,8 +745,12 @@ int position_estimator_inav_thread_main(int argc, char *argv[])
 		t_prev = t;
 
 		/* increase EPH/EPV on each step */
-		eph *= 1.0 + dt;
-		epv += 0.005 * dt;	// add 1m to EPV each 200s (baro drift)
+		if (eph < max_eph_epv) {
+			eph *= 1.0 + dt;
+		}
+		if (epv < max_eph_epv) {
+			epv += 0.005 * dt;	// add 1m to EPV each 200s (baro drift)
+		}
 
 		/* use GPS if it's valid and reference position initialized */
 		bool use_gps_xy = ref_inited && gps_valid && params.w_xy_gps_p > MIN_VALID_W;
@@ -731,7 +763,7 @@ int position_estimator_inav_thread_main(int argc, char *argv[])
 			xy_src_time = t;
 		}
 
-		bool can_estimate_xy = eph < max_eph_epv * 1.5;
+		bool can_estimate_xy = (eph < max_eph_epv) || use_gps_xy || use_flow;
 
 		bool dist_bottom_valid = (t < sonar_valid_time + sonar_valid_timeout);
 
@@ -763,7 +795,7 @@ int position_estimator_inav_thread_main(int argc, char *argv[])
 			corr_baro += offs_corr;
 		}
 
-		/* accelerometer bias correction */
+		/* accelerometer bias correction for GPS (use buffered rotation matrix) */
 		float accel_bias_corr[3] = { 0.0f, 0.0f, 0.0f };
 
 		if (use_gps_xy) {
@@ -777,6 +809,24 @@ int position_estimator_inav_thread_main(int argc, char *argv[])
 			accel_bias_corr[2] -= corr_gps[2][0] * w_z_gps_p * w_z_gps_p;
 		}
 
+		/* transform error vector from NED frame to body frame */
+		for (int i = 0; i < 3; i++) {
+			float c = 0.0f;
+
+			for (int j = 0; j < 3; j++) {
+				c += R_gps[j][i] * accel_bias_corr[j];
+			}
+
+			if (isfinite(c)) {
+				acc_bias[i] += c * params.w_acc_bias * dt;
+			}
+		}
+
+		/* accelerometer bias correction for flow and baro (assume that there is no delay) */
+		accel_bias_corr[0] = 0.0f;
+		accel_bias_corr[1] = 0.0f;
+		accel_bias_corr[2] = 0.0f;
+
 		if (use_flow) {
 			accel_bias_corr[0] -= corr_flow[0] * params.w_xy_flow;
 			accel_bias_corr[1] -= corr_flow[1] * params.w_xy_flow;
@@ -807,7 +857,12 @@ int position_estimator_inav_thread_main(int argc, char *argv[])
 
 		/* inertial filter correction for altitude */
 		inertial_filter_correct(corr_baro, dt, z_est, 0, params.w_z_baro);
-		inertial_filter_correct(corr_gps[2][0], dt, z_est, 0, w_z_gps_p);
+
+		if (use_gps_z) {
+			epv = fminf(epv, gps.epv_m);
+
+			inertial_filter_correct(corr_gps[2][0], dt, z_est, 0, w_z_gps_p);
+		}
 
 		if (!(isfinite(z_est[0]) && isfinite(z_est[1]))) {
 			write_debug_log("BAD ESTIMATE AFTER Z CORRECTION", dt, x_est, y_est, z_est, x_est_prev, y_est_prev, z_est_prev, acc, corr_gps, w_xy_gps_p, w_xy_gps_v);
@@ -832,11 +887,15 @@ int position_estimator_inav_thread_main(int argc, char *argv[])
 
 			/* inertial filter correction for position */
 			if (use_flow) {
+				eph = fminf(eph, eph_flow);
+
 				inertial_filter_correct(corr_flow[0], dt, x_est, 1, params.w_xy_flow * w_flow);
 				inertial_filter_correct(corr_flow[1], dt, y_est, 1, params.w_xy_flow * w_flow);
 			}
 
 			if (use_gps_xy) {
+				eph = fminf(eph, gps.eph_m);
+
 				inertial_filter_correct(corr_gps[0][0], dt, x_est, 0, w_xy_gps_p);
 				inertial_filter_correct(corr_gps[1][0], dt, y_est, 0, w_xy_gps_p);
 
@@ -910,8 +969,25 @@ int position_estimator_inav_thread_main(int argc, char *argv[])
 			}
 		}
 
-		if (t > pub_last + pub_interval) {
+		if (t > pub_last + PUB_INTERVAL) {
 			pub_last = t;
+
+			/* push current estimate to buffer */
+			est_buf[buf_ptr][0][0] = x_est[0];
+			est_buf[buf_ptr][0][1] = x_est[1];
+			est_buf[buf_ptr][1][0] = y_est[0];
+			est_buf[buf_ptr][1][1] = y_est[1];
+			est_buf[buf_ptr][2][0] = z_est[0];
+			est_buf[buf_ptr][2][1] = z_est[1];
+
+			/* push current rotation matrix to buffer */
+			memcpy(R_buf[buf_ptr], att.R, sizeof(att.R));
+
+			buf_ptr++;
+			if (buf_ptr >= EST_BUF_SIZE) {
+				buf_ptr = 0;
+			}
+
 			/* publish local position */
 			local_pos.xy_valid = can_estimate_xy;
 			local_pos.v_xy_valid = can_estimate_xy;
diff --git a/src/modules/position_estimator_inav/position_estimator_inav_params.c b/src/modules/position_estimator_inav/position_estimator_inav_params.c
index 8aa08b6f2..d88419c25 100644
--- a/src/modules/position_estimator_inav/position_estimator_inav_params.c
+++ b/src/modules/position_estimator_inav/position_estimator_inav_params.c
@@ -55,6 +55,7 @@ PARAM_DEFINE_FLOAT(INAV_SONAR_ERR, 0.5f);
 PARAM_DEFINE_FLOAT(INAV_LAND_T, 3.0f);
 PARAM_DEFINE_FLOAT(INAV_LAND_DISP, 0.7f);
 PARAM_DEFINE_FLOAT(INAV_LAND_THR, 0.2f);
+PARAM_DEFINE_FLOAT(INAV_DELAY_GPS, 0.2f);
 
 int parameters_init(struct position_estimator_inav_param_handles *h)
 {
@@ -73,6 +74,7 @@ int parameters_init(struct position_estimator_inav_param_handles *h)
 	h->land_t = param_find("INAV_LAND_T");
 	h->land_disp = param_find("INAV_LAND_DISP");
 	h->land_thr = param_find("INAV_LAND_THR");
+	h->delay_gps = param_find("INAV_DELAY_GPS");
 
 	return OK;
 }
@@ -94,6 +96,7 @@ int parameters_update(const struct position_estimator_inav_param_handles *h, str
 	param_get(h->land_t, &(p->land_t));
 	param_get(h->land_disp, &(p->land_disp));
 	param_get(h->land_thr, &(p->land_thr));
+	param_get(h->delay_gps, &(p->delay_gps));
 
 	return OK;
 }
diff --git a/src/modules/position_estimator_inav/position_estimator_inav_params.h b/src/modules/position_estimator_inav/position_estimator_inav_params.h
index 08ec996a1..df1cfaa71 100644
--- a/src/modules/position_estimator_inav/position_estimator_inav_params.h
+++ b/src/modules/position_estimator_inav/position_estimator_inav_params.h
@@ -56,6 +56,7 @@ struct position_estimator_inav_params {
 	float land_t;
 	float land_disp;
 	float land_thr;
+	float delay_gps;
 };
 
 struct position_estimator_inav_param_handles {
@@ -74,6 +75,7 @@ struct position_estimator_inav_param_handles {
 	param_t land_t;
 	param_t land_disp;
 	param_t land_thr;
+	param_t delay_gps;
 };
 
 /**
diff --git a/src/modules/sdlog2/sdlog2.c b/src/modules/sdlog2/sdlog2.c
index 5e6946658..d2c86d8b2 100644
--- a/src/modules/sdlog2/sdlog2.c
+++ b/src/modules/sdlog2/sdlog2.c
@@ -1516,6 +1516,7 @@ int sdlog2_thread_main(int argc, char *argv[])
 			log_msg.body.log_TECS.flightPathAngle = buf.tecs_status.flightPathAngle;
 			log_msg.body.log_TECS.airspeedSp = buf.tecs_status.airspeedSp;
 			log_msg.body.log_TECS.airspeed = buf.tecs_status.airspeed;
+			log_msg.body.log_TECS.airspeedFiltered = buf.tecs_status.airspeedFiltered;
 			log_msg.body.log_TECS.airspeedDerivativeSp = buf.tecs_status.airspeedDerivativeSp;
 			log_msg.body.log_TECS.airspeedDerivative = buf.tecs_status.airspeedDerivative;
 			log_msg.body.log_TECS.totalEnergyRateSp = buf.tecs_status.totalEnergyRateSp;
diff --git a/src/modules/sdlog2/sdlog2_messages.h b/src/modules/sdlog2/sdlog2_messages.h
index 9a26e1c51..e55ae109d 100644
--- a/src/modules/sdlog2/sdlog2_messages.h
+++ b/src/modules/sdlog2/sdlog2_messages.h
@@ -347,6 +347,7 @@ struct log_TECS_s {
 	float flightPathAngle;
 	float airspeedSp;
 	float airspeed;
+	float airspeedFiltered;
 	float airspeedDerivativeSp;
 	float airspeedDerivative;
 
@@ -439,7 +440,7 @@ static const struct log_format_s log_formats[] = {
 	LOG_FORMAT(GS0B, "BBBBBBBBBBBBBBBB",	"s0,s1,s2,s3,s4,s5,s6,s7,s8,s9,s10,s11,s12,s13,s14,s15"),
 	LOG_FORMAT(GS1A, "BBBBBBBBBBBBBBBB",	"s0,s1,s2,s3,s4,s5,s6,s7,s8,s9,s10,s11,s12,s13,s14,s15"),
 	LOG_FORMAT(GS1B, "BBBBBBBBBBBBBBBB",	"s0,s1,s2,s3,s4,s5,s6,s7,s8,s9,s10,s11,s12,s13,s14,s15"),
-	LOG_FORMAT(TECS, "ffffffffffffB",	"AltSP,Alt,FpaSP,Fpa,AsSP,As,AsDSP,AsD,TERSP,TER,EDRSP,EDR,Mod"),
+	LOG_FORMAT(TECS, "fffffffffffffB",	"AltSP,Alt,FpaSP,Fpa,AsSP,As,AsF,AsDSP,AsD,TERSP,TER,EDRSP,EDR,Mod"),
 	LOG_FORMAT(WIND, "ffff",	"X,Y,CovX,CovY"),
 
 	/* system-level messages, ID >= 0x80 */
diff --git a/src/modules/uORB/topics/tecs_status.h b/src/modules/uORB/topics/tecs_status.h
index fc530b295..05310e906 100644
--- a/src/modules/uORB/topics/tecs_status.h
+++ b/src/modules/uORB/topics/tecs_status.h
@@ -70,6 +70,7 @@ struct tecs_status_s {
 	float flightPathAngle;
 	float airspeedSp;
 	float airspeed;
+	float airspeedFiltered;
 	float airspeedDerivativeSp;
 	float airspeedDerivative;