External reaction But Time-Varying Force with Changing Magnitude and Direction

[brownbea]

Hello everyone,

I am currently working on constructing a tether wing model that involves considering a force which varies over time not only in magnitude but also in direction. However, the external reaction that defined in XML file can not be time-varying. I would like to inquire about the best approach to incorporate such dynamic forces into my simulation model.

I am particularly interested in finding effective solutions to this problem and would appreciate any suggestions, experiences, or insights you may have.

Thank you in advance for your assistance!

[andgi]

I think you can change both magnitude and also direction already. For direction you can also split it into 3 90 degree angle forces - that has worked from the beginning of external forces. Have a look at the hydrodynamics.xml system (https://github.com/JSBSim-Team/jsbsim/blob/master/systems/hydrodynamics.xml) for an example. It is used in the aircraft Short_S23 that is in the aircraft directory.

[seanmcleod]

Looks like you can change both the direction and magnitude at runtime, so you can make them both time varying. If you use a function for the force magnitude you can make use of properties in the function which means you can also make it time varying by varying the value of the properties used.

jsbsim/src/models/FGExternalForce.h

Lines 176 to 183 in b9bfc23

	The force direction can be specified at runtime through setting any/all of
	the following properties:
	@code
	external_reactions/{force name}/x
	external_reactions/{force name}/y
	external_reactions/{force name}/z
	@endcode

jsbsim/src/models/FGExternalForce.h

Lines 196 to 201 in b9bfc23

	When no <function> has been provided in the force definition, its magnitude
	can be specified through the following property:
	@code
	external_reactions/{force name}/magnitude
	@endcode

[brownbea]

Thank you very much for taking the time to answer my questions, it's been very helpful.