MC att control: Add time constant to simplify user-tuning of basic vehicle operation

src/modules/mc_att_control/mc_att_control_main.cpp

@@ -101,6 +101,7 @@ extern "C" __EXPORT int mc_att_control_main(int argc, char *argv[]);
 #define MIN_TAKEOFF_THRUST    0.2f
 #define RATES_I_LIMIT	0.3f
 #define MANUAL_THROTTLE_MAX_MULTICOPTER	0.9f
+#define ATTITUDE_TC_DEFAULT 0.2f
 
 class MulticopterAttitudeControl
 {
@@ -196,6 +197,8 @@ private:
 		param_t rattitude_thres;
 
 		param_t vtol_type;
+		param_t roll_tc;
+		param_t pitch_tc;
 
 	}		_params_handles;		/**< handles for interesting parameters */
 
@@ -384,6 +387,8 @@ MulticopterAttitudeControl::MulticopterAttitudeControl() :
 	_params_handles.acro_yaw_max	= 	param_find("MC_ACRO_Y_MAX");
 	_params_handles.rattitude_thres = 	param_find("MC_RATT_TH");
 	_params_handles.vtol_type 		= 	param_find("VT_TYPE");
+	_params_handles.roll_tc			= 	param_find("MC_ROLL_TC");
+	_params_handles.pitch_tc		= 	param_find("MC_PITCH_TC");
 
 	/* fetch initial parameter values */
 	parameters_update();
@@ -426,27 +431,32 @@ MulticopterAttitudeControl::parameters_update()
 {
 	float v;
 
+	float roll_tc, pitch_tc;
+
+	param_get(_params_handles.roll_tc, &roll_tc);
+	param_get(_params_handles.pitch_tc, &pitch_tc);
+
 	/* roll gains */
 	param_get(_params_handles.roll_p, &v);
-	_params.att_p(0) = v;
+	_params.att_p(0) = v * (ATTITUDE_TC_DEFAULT / roll_tc);
 	param_get(_params_handles.roll_rate_p, &v);
-	_params.rate_p(0) = v;
+	_params.rate_p(0) = v * (ATTITUDE_TC_DEFAULT / roll_tc);
 	param_get(_params_handles.roll_rate_i, &v);
 	_params.rate_i(0) = v;
 	param_get(_params_handles.roll_rate_d, &v);
-	_params.rate_d(0) = v;
+	_params.rate_d(0) = v * (ATTITUDE_TC_DEFAULT / roll_tc);
 	param_get(_params_handles.roll_rate_ff, &v);
 	_params.rate_ff(0) = v;
 
 	/* pitch gains */
 	param_get(_params_handles.pitch_p, &v);
-	_params.att_p(1) = v;
+	_params.att_p(1) = v * (ATTITUDE_TC_DEFAULT / pitch_tc);
 	param_get(_params_handles.pitch_rate_p, &v);
-	_params.rate_p(1) = v;
+	_params.rate_p(1) = v * (ATTITUDE_TC_DEFAULT / pitch_tc);
 	param_get(_params_handles.pitch_rate_i, &v);
 	_params.rate_i(1) = v;
 	param_get(_params_handles.pitch_rate_d, &v);
-	_params.rate_d(1) = v;
+	_params.rate_d(1) = v * (ATTITUDE_TC_DEFAULT / pitch_tc);
 	param_get(_params_handles.pitch_rate_ff, &v);
 	_params.rate_ff(1) = v;
 

src/modules/mc_att_control/mc_att_control_params.c

@@ -39,6 +39,28 @@
  * @author Anton Babushkin <anton@px4.io>
  */
 
+/**
+ * Roll time constant
+ *
+ * Reduce if the system is too twitchy, increase if the response is too slow and sluggish.
+ *
+ * @min 0.15
+ * @max 0.25
+ * @group Multicopter Attitude Control
+ */
+PARAM_DEFINE_FLOAT(MC_ROLL_TC, 0.2f);
+
+/**
+ * Pitch time constant
+ *
+ * Reduce if the system is too twitchy, increase if the response is too slow and sluggish.
+ *
+ * @min 0.15
+ * @max 0.25
+ * @group Multicopter Attitude Control
+ */
+PARAM_DEFINE_FLOAT(MC_PITCH_TC, 0.2f);
+
 /**
  * Roll P gain
  *