Use Unicode subscript notation for transfer-function variables

AERO3220_HW4_block_diagram.md

@@ -82,22 +82,22 @@ This version shows the same coupled dynamics using gain blocks and integrator tr
 
 ```mermaid
 flowchart LR
-    Z1[State z1] --> G11[Gain -k1/m1]
+    Z1[State z₁] --> G11[Gain -k₁/m₁]
     G11 --> S1[Sum z̈₁]
-    Z2[State z2] --> G12[Gain +k1/m1]
+    Z2[State z₂] --> G12[Gain +k₁/m₁]
     G12 --> S1
     S1 --> I11[Transfer block 1/s]
     I11 --> Z1D[State ż₁]
     Z1D --> I12[Transfer block 1/s]
     I12 --> Z1
 
-    U[Input force u] --> G2U[Gain 1/m2]
+    U[Input force u] --> G2U[Gain 1/m₂]
     G2U --> S2[Sum z̈₂]
-    Z1 --> G21[Gain k1/m2]
+    Z1 --> G21[Gain k₁/m₂]
     G21 --> S2
-    Z2 --> G22["Gain -(k1 + k2)/m2"]
+    Z2 --> G22["Gain -(k₁ + k₂)/m₂"]
     G22 --> S2
-    Z2D[State ż₂] --> G23[Gain -b/m2]
+    Z2D[State ż₂] --> G23[Gain -b/m₂]
     G23 --> S2
     S2 --> I21[Transfer block 1/s]
     I21 --> Z2D