Modified stuck valve fault description

lumen/lumen_index.md

@@ -13,7 +13,7 @@
 
 ## LUMEN Fault Diagnosis Benchmark
 
-** Latest update January 9th, 2025: Website is updated. 
+** Latest update January 24th, 2025: Modified stuck valve fault description. 
 
 This homepage contains information about the Liquid Upper stage demonstrator Engine (LUMEN) benchmark.
 
@@ -64,8 +64,7 @@ In total 10 test runs in the simulation domain for different fault scenarios are
   $A_{\text{t}} = f A_{\text{t}}$, $f < 1.0$
 * Pump leakage: This fault results in a leakage mass flow downstream of the pump. It is modeled with an additional valve which can be opened and thus inject a partial mass flow into the environment. The opening area of the valve $A_{\text{valve}}$ is a linear function of the throat area $A_{\text{0}}$ and the position of the valve $x_{\text{valve}}$\
    $A_{\text{valve}} = x_{\text{valve}} A_{\text{0}}$, $x_{\text{valve}} > 0.0$
-* Stuck valve: This fault results in an additive offset $f$ in the command signal of a control valve $u_{\text{valve}}$\
-   $u_{\text{valve}} = f u_{\text{valve}}$, $f = [-1.0, 1.0]$
+* Stuck valve: This fault results in a stuck FCV valve, i.e. the valve position does not change in accordance with the command.
 * Multiplicative faults in all sensors: This fault results in a multiplicative offset $f$ in the output of the corresponding signal\
    $y_{\text{sensor}} = f y_{\text{sensor}}$, $f = [0.8, 1.2]$