When we design a control system for a physical process, one or more parameters are to be selected to give the best performance. For this purpose, a measure known as Performance Indices is used. The usual criteria for performance index are given using 4 expressions which are the function of an error signal.

1. Integral Square Error (ISE)

2. Integral Absolute Error (IAE)

3. Integral time Squared Error (ITSE)

4 Integral time Absolute Error (ITAE)

The error signal e(t) in a control system is given by

e(t) = r(t) − c(t)

where, r(t) = input or reference signal

c(t) = output signal

Performance Indices in Control System are as follows:

**1. Integral Square Error (ISE)**

**2. Integral Absolute Error (IAE)**

**3. Integral time Squared Error (ITSE)**

**4 Integral time Absolute Error (ITAE)**