Implemented SK450 DeadCat frame support

Implemented the way to specify motor output scale which is required for SK450 DeadCat as it has asymetrical arms (front arms are longer than back ones)

ROMFS/px4fmu_common/init.d/10019_sk450_deadcat

@@ -0,0 +1,32 @@
+#!nsh
+#
+# HobbyKing SK450 DeadCat modification
+#
+# Anton Matosov <anton.matosov@gmail.com>
+#
+
+sh /etc/init.d/rc.mc_defaults
+
+if [ $AUTOCNF == yes ]
+then
+	param set MC_ROLL_P 6.0
+	param set MC_ROLLRATE_P 0.04
+	param set MC_ROLLRATE_I 0.1
+	param set MC_ROLLRATE_D 0.0015
+	
+	param set MC_PITCH_P 6.0
+	param set MC_PITCHRATE_P 0.08
+	param set MC_PITCHRATE_I 0.2
+	param set MC_PITCHRATE_D 0.0015
+	
+	param set MC_YAW_P 2.8
+	param set MC_YAWRATE_P 0.1
+	param set MC_YAWRATE_I 0.07
+	param set MC_YAWRATE_D 0.0
+fi
+
+set VEHICLE_TYPE mc
+set MIXER FMU_quad_deadcat
+
+set PWM_OUTPUTS 1234
+set PWM_MIN 1075

ROMFS/px4fmu_common/init.d/rc.autostart

@@ -226,6 +226,11 @@ then
 	sh /etc/init.d/10018_tbs_endurance
 fi
 
+if param compare SYS_AUTOSTART 10019
+then
+	sh /etc/init.d/10019_sk450_deadcat
+fi
+
 #
 # Hexa Coaxial
 #

ROMFS/px4fmu_common/mixers/FMU_quad_deadcat.mix

@@ -0,0 +1,25 @@
+Multirotor mixer for PX4FMU
+===========================
+
+This file defines a single mixer for a quadrotor in SK450 DeadCat configuration.  All controls are mixed 100%.
+
+R: 4dc 10000 10000 10000 0
+
+Gimbal / payload mixer for last four channels
+-----------------------------------------------------
+
+M: 1
+O:      10000  10000      0 -10000  10000
+S: 0 4  10000  10000      0 -10000  10000
+
+M: 1
+O:      10000  10000      0 -10000  10000
+S: 0 5  10000  10000      0 -10000  10000
+
+M: 1
+O:      10000  10000      0 -10000  10000
+S: 0 6  10000  10000      0 -10000  10000
+
+M: 1
+O:      10000  10000      0 -10000  10000
+S: 0 7  10000  10000      0 -10000  10000

src/modules/systemlib/mixer/mixer.h

@@ -441,7 +441,6 @@ private:
 	SimpleMixer operator=(const SimpleMixer&);
 };
 
-
 /**
  * Supported multirotor geometries.
  *
@@ -460,12 +459,14 @@ class __EXPORT MultirotorMixer : public Mixer
 {
 public:
 	/**
+
 	 * Precalculated rotor mix.
 	 */
 	struct Rotor {
 		float	roll_scale;	/**< scales roll for this rotor */
 		float	pitch_scale;	/**< scales pitch for this rotor */
 		float	yaw_scale;	/**< scales yaw for this rotor */
+		float	out_scale;	/**< scales total out for this rotor */
 	};
 
 	/**

src/modules/systemlib/mixer/mixer_multirotor.cpp

@@ -75,7 +75,8 @@ float constrain(float val, float min, float max)
 {
 	return (val < min) ? min : ((val > max) ? max : val);
 }
-}
+
+} // anonymous namespace
 
 MultirotorMixer::MultirotorMixer(ControlCallback control_cb,
 				 uintptr_t cb_handle,
@@ -89,6 +90,7 @@ MultirotorMixer::MultirotorMixer(ControlCallback control_cb,
 	_pitch_scale(pitch_scale),
 	_yaw_scale(yaw_scale),
 	_idle_speed(-1.0f + idle_speed * 2.0f),	/* shift to output range here to avoid runtime calculation */
+	_limits_pub(),
 	_rotor_count(_config_rotor_count[(MultirotorGeometryUnderlyingType)geometry]),
 	_rotors(_config_index[(MultirotorGeometryUnderlyingType)geometry])
 {
@@ -152,6 +154,9 @@ MultirotorMixer::from_text(Mixer::ControlCallback control_cb, uintptr_t cb_handl
 	} else if (!strcmp(geomname, "4w")) {
 		geometry = MultirotorGeometry::QUAD_WIDE;
 
+	} else if (!strcmp(geomname, "4dc")) {
+		geometry = MultirotorGeometry::QUAD_DEADCAT;
+
 	} else if (!strcmp(geomname, "6+")) {
 		geometry = MultirotorGeometry::HEX_PLUS;
 
@@ -212,6 +217,8 @@ MultirotorMixer::mix(float *outputs, unsigned space)
 			    pitch * _rotors[i].pitch_scale +
 			    thrust;
 
+		out *= _rotors[i].out_scale;
+
 		/* limit yaw if it causes outputs clipping */
 		if (out >= 0.0f && out < -yaw * _rotors[i].yaw_scale) {
 			yaw = -out / _rotors[i].yaw_scale;

src/modules/systemlib/mixer/multi_tables.py

@@ -69,6 +69,13 @@ quad_plus = [
     [ 180, CW],
 ]
 
+quad_deadcat = [
+    [  63, CCW, 1.0],
+    [-135, CCW, 0.964],
+    [ -63, CW, 1.0],
+    [ 135, CW, 0.964],
+]
+
 quad_v = [
     [  18.8, 0.4242],
     [ -18.8, 1.0],
@@ -148,13 +155,18 @@ twin_engine = [
     [-90, 0.0],
 ]
 
+
+tables = [quad_x, quad_plus, quad_v, quad_wide, quad_deadcat, hex_x, hex_plus, hex_cox, octa_x, octa_plus, octa_cox, twin_engine]
+
 def variableName(variable):
     for variableName, value in list(globals().items()):
         if value is variable:
             return variableName
 
-tables = [quad_x, quad_plus, quad_v, quad_wide, hex_x, hex_plus, hex_cox, octa_x, octa_plus, octa_cox, twin_engine]
+def unpackScales(scalesList):
-
+    if len(scalesList) == 2:
+        scalesList += [1.0] #Add thrust scale
+    return scalesList
 
 def printEnum():
     print("enum class MultirotorGeometry : MultirotorGeometryUnderlyingType {")
@@ -167,10 +179,11 @@ def printEnum():
 def printScaleTables():
     for table in tables:
         print("const MultirotorMixer::Rotor _config_{}[] = {{".format(variableName(table)))
-        for (angle, yawScale) in table:
+        for row in table:
+            angle, yawScale, thrustScale = unpackScales(row)
             rollScale = rcos(angle + 90)
             pitchScale = rcos(angle)
-            print("\t{{ {:9f}, {:9f}, {:9f} }},".format(rollScale, pitchScale, yawScale))
+            print("\t{{ {:9f}, {:9f}, {:9f}, {:9f} }},".format(rollScale, pitchScale, yawScale, thrustScale))
         print("};\n")
 
 def printScaleTablesIndex():