[Jsbsim-users] Unable to implement a Yaw Damper using the washout filter

[Peter S. <Pet...@on...>]

Dear JSBSim users,

I aim at reproducing a generic Yaw damper as proposed by Blakelock in 
his book "Automatic Control of Aircraft and Missiles".

The block diagram looks like this:

[Blakelock picture]


I modified then the Tutorial_1.xml file to implement the Yaw Damper 
using the washout filter (like on the F22 model).

Unfortunately, there is absolutely no damping of the dutch roll when I 
run the simulation.

I copied here below the part of the aircraft file where the Yaw Damper 
is coded.

Any Idea about my (obvious) mistake(s)?
My last automatic control classe was long time ago so please be indulgent :)

Thank you for your help.

Kind regards,


Peter


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<channel name="Yaw">
    <summer name="Rudder Command Sum">
       <input>fcs/rudder-cmd-norm</input>
       <input>fcs/yaw-trim-cmd-norm</input>
       <clipto>
         <min>-1</min>
         <max>1</max>
       </clipto>
    </summer>

     <actuator name="generic_actuator">
           <input> fcs/rudder-command-sum </input>
           <lag> 0.0 </lag>
           <rate_limit> 0.0 </rate_limit>
         <clipto>
             <min> -1.0 </min>
             <max>  1.0 </max>
        </clipto>
         <output>fcs/rudder-pos-norm</output>
     </actuator>

     <washout_filter name="yaw_damper_washout">
<input>velocities/r-aero-rad_sec</input>
         <c1> 1.2 </c1>
         <output>fcs/yaw-damper-washout</output>
     </washout_filter>

    <summer name="Rudder Sum">
       <input>fcs/rudder-pos-norm</input>
       <input>fcs/yaw-damper-washout</input>
         <clipto>
             <min> -1.0 </min>
             <max>  1.0 </max>
        </clipto>
    </summer>

     <aerosurface_scale name="Rudder Control rad">
       <input>fcs/rudder-sum</input>
       <range>
         <min> -0.35 </min>
         <max>  0.35 </max>
       </range>
       <output>fcs/rudder-pos-rad</output>
    </aerosurface_scale>

    <aerosurface_scale name="Rudder Control deg">
       <input>fcs/rudder-pos-norm</input>
       <range>
         <min> -20.0 </min>
         <max>  20.0 </max>
       </range>
       <output>fcs/rudder-pos-deg</output>
    </aerosurface_scale>
   </channel>
--------------------------------------------------------------------------------------