Transfer function of an armature-controlled motor

 

 

Fig: 1 Block diagram of armature controlled motor

 

 

 

Fig: 2

 

The block diagram of the armature-controlled DC motor is shown in Figure 1. The signal-flow diagram can be obtained from the block diagram and is shown in Figure 2. Using Mason's signal-flow gain formula, let us obtain the transfer function for θ(s)/V_a(s) with T_d(s) = 0. The forward path is P₁(s), which touches the one loop, L₁(s), where

 

Therefore, the transfer function is

 

 

which is exactly the same as that from the block diagram.