mtecs: add altitude prefiltering

src/modules/fw_pos_control_l1/mtecs/mTecs.cpp

@@ -59,6 +59,7 @@ mTecs::mTecs() :
 	_controlAltitude(this, "FPA", true),
 	_controlAirSpeed(this, "ACC"),
 	_flightPathAngleLowpass(this, "FPA_LP"),
+	_altitudeLowpass(this, "ALT_LP"),
 	_airspeedLowpass(this, "A_LP"),
 	_airspeedDerivative(this, "AD"),
 	_throttleSp(0.0f),
@@ -93,18 +94,23 @@ int mTecs::updateAltitudeSpeed(float flightPathAngle, float altitude, float alti
 	/* time measurement */
 	updateTimeMeasurement();
 
+	/* Filter altitude */
+	float altitudeFiltered = _altitudeLowpass.update(altitude);
+
+
 	/* calculate flight path angle setpoint from altitude setpoint */
-	float flightPathAngleSp = _controlAltitude.update(altitudeSp - altitude);
+	float flightPathAngleSp = _controlAltitude.update(altitudeSp - altitudeFiltered);
 
 	/* Debug output */
 	if (_counter % 10 == 0) {
 		debug("***");
-		debug("updateAltitudeSpeed: altitudeSp %.4f, altitude %.4f, flightPathAngleSp %.4f", (double)altitudeSp, (double)altitude, (double)flightPathAngleSp);
+		debug("updateAltitudeSpeed: altitudeSp %.4f, altitude %.4f, altitude filtered %.4f, flightPathAngleSp %.4f", (double)altitudeSp, (double)altitude, (double)altitudeFiltered, (double)flightPathAngleSp);
 	}
 
 	/* Write part of the status message */
 	_status.altitudeSp = altitudeSp;
 	_status.altitude = altitude;
+	_status.altitudeFiltered = altitudeFiltered;
 
 
 	/* use flightpath angle setpoint for total energy control */

src/modules/fw_pos_control_l1/mtecs/mTecs.h

@@ -115,6 +115,7 @@ protected:
 
 	/* Other calculation Blocks */
 	control::BlockLowPass _flightPathAngleLowpass;	/**< low pass filter for the flight path angle */
+	control::BlockLowPass _altitudeLowpass;	/**< low pass filter for altitude */
 	control::BlockLowPass _airspeedLowpass;		/**< low pass filter for airspeed */
 	control::BlockDerivative _airspeedDerivative;	/**< airspeed derivative calulation */
 

src/modules/fw_pos_control_l1/mtecs/mTecs_params.c

@@ -174,6 +174,13 @@ PARAM_DEFINE_FLOAT(MT_PIT_MIN, -45.0f);
  */
 PARAM_DEFINE_FLOAT(MT_PIT_MAX, 20.0f);
 
+/**
+ * Lowpass (cutoff freq.) for altitude
+ *
+ * @group mTECS
+ */
+PARAM_DEFINE_FLOAT(MT_ALT_LP, 1.0f);
+
 /**
  * Lowpass (cutoff freq.) for the flight path angle
  *