how to get velocity from encoder signal in simulink

I am using the transfer function s/(tau*s+1) to get the angular velocity from the encoder angle signal. But the problem is that in the simulation, open loop yields smaller error than the close loop control for trajectory tracking. Is there any other way to get velocity from encoder signal in simulink?

PS: my system is a pendulum attached to the shaft of a DC motor and it is oscillating around the Straight Down position within 1 radian which is the desired trajectory).