For reducing steady state error which type of controller is used?

The system type of the forward-path system determines if the path system determines if the

steady-state error is zero. state error is zero.

The key tool is the The key tool is the final value theorem!

PID Controllers which means 

Proportional Integral Derivative

PID Controller is used.

Also you can tune the KI and KP parameter to reduce the offset or increace the action of the PID controller

PID controller reduces offset as well as steady state error and reduces oscillations.

1.Proportional controllers

2.Integral controllers

3.Derivative controllers.