Declaring new Property in aircraft .xml

[ThomasKennings]

Documentation like the JSBSim PDF manual suggests that it's totally possible to instantiate an aircraft-specific variable, but when I try to do so I get an invalid token error at the bottom of the 737.xml file. I am trying to make an altitude setpoint variable for use in a PID flight controller. I have tried several things, among them putting this next to my PID section:

fcs/pid-alt-setpoint

Can someone give me an example of the proper way to do this? For the life of me I cannot find where other aircraft-specific properties are declared. I apologize for clogging this forum so!

[seanmcleod]

Please post the actual snippet and also post the actual output error. It makes it much more difficult and partly a guessing game trying to debug issues with very limited info.

Here are 2 random examples. A good source is to look for existing examples in the repo.

jsbsim/aircraft/global5000/global5000ap.xml

Lines 30 to 53 in 33735db

	<autopilot name="Global5000 Autopilot">
	<!-- INTERFACE PROPERTIES -->
	<property> ap/attitude_hold </property>
	<property> ap/altitude_hold </property>
	<property> ap/heading_hold </property>
	<property> ap/altitude_setpoint </property>
	<property> ap/heading_setpoint </property>
	<property> ap/aileron_cmd </property>
	<property> ap/elevator_cmd </property>
	<property> ap/airspeed_setpoint </property>
	<property> ap/airspeed_hold </property>
	<property> ap/throttle-cmd-norm </property>
	<property> ap/alpha_setpoint </property>
	<property> ap/alpha_hold </property>
	<!-- INITIAL GAIN VALUES -->
	<property value="0.5"> ap/hdg-roll-err-c1 </property>
	<property value="50.0"> ap/roll-pid-kp </property>
	<property value="5.0"> ap/roll-pid-ki </property>
	<property value="17.0"> ap/roll-pid-kd </property>

jsbsim/aircraft/global5000/global5000.xml

Lines 250 to 253 in 33735db

	<system file="Autopilot">
	<property value="0.523"> guidance/roll-angle-limit </property>
	<property value="0.174"> guidance/roll-rate-limit </property>
	</system>