What is meaning of fcs/aileron-cmd-norm property

[dw95kim]

I'm experimenting with reinforcement learning using JSBSim, and I'm using the value of fcs/aileron-cmd-norm as one of the outputs for the reinforcement learning.

1. I understood this value to represent the actual control stick input of the pilot, is that correct? If not, what is the property for the control stick value?

2. I understand that in actual fighter jets, the control stick and the control surfaces are not reflected 1:1 due to the Fly-By-Wire (FBW) system. Is this aspect considered in JSBSim as well?

[bcoconni]

1. I understood this value to represent the actual control stick input of the pilot, is that correct? If not, what is the property for the control stick value?

The exact meaning of the property fcs/aileron-cmd-norm depends on the model you are using. But generally speaking, you are correct: it is as much deflection of the aileron as the control stick requests.

2. I understand that in actual fighter jets, the control stick and the control surfaces are not reflected 1:1 due to the Fly-By-Wire (FBW) system. Is this aspect considered in JSBSim as well?

Here again, the implementation of a FBW is left to the model author. JSBSim is capable of simulating aircraft with or without FBW. Even the sign convention of fcs/aileron-cmd-norm is left to the model author.

If you could tell which flight dynamics model you are using, we would be able to give you a bit more explanations.

[Warning39]

As @bcoconni mentioned, the implementation or not of an FBW control system is up to the developer of each aircraft model, specified in the FCS section.

So for example take a look at the FCS sections of the 737 which doesn't include FBW:

https://github.com/JSBSim-Team/jsbsim/blob/master/aircraft/737/737.xml

And the F-16 which does include FBW:

https://github.com/JSBSim-Team/jsbsim/blob/master/aircraft/f16/f16.xml

[dw95kim]

Thank you for your prompt response.

We are utilizing the JSBSim/aircraft/f16.xml file. In this XML file, is the fcs/aileron-cmd-norm property the pilot-controlled stick with fly-by-wire (FBW) systems implemented?

Could you guide me on how to read XML files? Specifically, where should I look within the XML file to determine which parts are controlled by a particular property, and how can I confirm whether FBW is applied?

[dw95kim]

Also, could you tell me which properties can be used for controlling the aileron control surfaces on each wing of a fighter jet? I am currently utilizing f16.xml.

[Warning39]

@dw95kim have you taken a look at FCS section in the F-16's XML file to try and follow the logic?

If there is an FBW system then there isn't going to be a simple one-to-one mapping between some property and a control surface like the aileron. There is going to be a lot of control logic in-between.

For example, at a high-level the pilot's input, e.g. fcs/aileron-cmd-norm will typically be mapped to a pilot commanded roll rate. There will then be some control logic, e.g. in the simple case a basic PID controller that will then move the relevant control surfaces to try and achieve the pilot's commanded roll rate with a feedback loop etc.