SKEDSOFT
Comparison of steady-state errors in open-loop control system and closed loop control system:
Fig: 1 Block diagrams of an open-loop control system and a closed-loop control system.
Consider the open-loop control system and closed-loop control system shown in Figure 1. In the open loop one, gain Kc is calibrated so that Kc = 1/K. Thus, the transfer function of the open-loop control system is
In the closed-loop control system, gain Kp of the controller is set so that KpK >> 1.
Table: Steady-State Error in Terms of Gain K
Assuming a unit-step input, let us compare the steady-state errors for these control systems. For the open-loop control system, the error signal is
The steady-state error in the unit-step response is
