fix submarine sitl: indicate motor channel range 0..1 or -1..1 in simulation_mavlink.cpp (#16637)

change motor_count variable to 'pos_thrust_motor_count'
This is more specific to what is actually happening in the code.
'pos_thrust_motors_count' indicates number of motor channels which are configured with 0..1 range (positive thrust) all other motors are configured for -1..1 range

submarine only have motors with -1..1 range.
Thus, pos_thrust_motor_count = 0

Co-authored-by: Thies Lennart Alff <33184858+lennartalff@users.noreply.github.com>

src/modules/simulator/simulator_mavlink.cpp

@@ -87,52 +87,58 @@ void Simulator::actuator_controls_from_outputs(mavlink_hil_actuator_controls_t *
 
 	int _system_type = _param_mav_type.get();
 
-	unsigned motors_count;
+	/* 'pos_thrust_motors_count' indicates number of motor channels which are configured with 0..1 range (positive thrust)
+	all other motors are configured for -1..1 range */
+	unsigned pos_thrust_motors_count;
 	bool is_fixed_wing;
 
 	switch (_system_type) {
 	case MAV_TYPE_AIRSHIP:
 	case MAV_TYPE_VTOL_DUOROTOR:
 	case MAV_TYPE_COAXIAL:
-		motors_count = 2;
+		pos_thrust_motors_count = 2;
 		is_fixed_wing = false;
 		break;
 
 	case MAV_TYPE_TRICOPTER:
-		motors_count = 3;
+		pos_thrust_motors_count = 3;
 		is_fixed_wing = false;
 		break;
 
 	case MAV_TYPE_QUADROTOR:
 	case MAV_TYPE_VTOL_QUADROTOR:
 	case MAV_TYPE_VTOL_TILTROTOR:
-		motors_count = 4;
+		pos_thrust_motors_count = 4;
 		is_fixed_wing = false;
 		break;
 
 	case MAV_TYPE_VTOL_RESERVED2:
-		motors_count = 5;
+		pos_thrust_motors_count = 5;
 		is_fixed_wing = false;
 		break;
 
 	case MAV_TYPE_HEXAROTOR:
-		motors_count = 6;
+		pos_thrust_motors_count = 6;
 		is_fixed_wing = false;
 		break;
 
 	case MAV_TYPE_OCTOROTOR:
+		pos_thrust_motors_count = 8;
+		is_fixed_wing = false;
+		break;
+
 	case MAV_TYPE_SUBMARINE:
-		motors_count = 8;
+		pos_thrust_motors_count = 0;
 		is_fixed_wing = false;
 		break;
 
 	case MAV_TYPE_FIXED_WING:
-		motors_count = 0;
+		pos_thrust_motors_count = 0;
 		is_fixed_wing = true;
 		break;
 
 	default:
-		motors_count = 0;
+		pos_thrust_motors_count = 0;
 		is_fixed_wing = false;
 		break;
 	}
@@ -143,7 +149,7 @@ void Simulator::actuator_controls_from_outputs(mavlink_hil_actuator_controls_t *
 			msg->controls[i] = 0.0f;
 
 		} else if ((is_fixed_wing && i == 4) ||
-			   (!is_fixed_wing && i < motors_count)) {	//multirotor, rotor channel
+			   (!is_fixed_wing && i < pos_thrust_motors_count)) {	//multirotor, rotor channel
 			/* scale PWM out PWM_DEFAULT_MIN..PWM_DEFAULT_MAX us to 0..1 for rotors */
 			msg->controls[i] = (_actuator_outputs.output[i] - PWM_DEFAULT_MIN) / (PWM_DEFAULT_MAX - PWM_DEFAULT_MIN);
 			msg->controls[i] = math::constrain(msg->controls[i], 0.f, 1.f);