Abstract
This paper verifies a fractional-order PI controller to stabilize integrating time delay plants. Firstly, the stability region by non-integer order controller namely, PI λ is illustrated using boundary condition. This is achieved using complex root boundary domains. The controller parameters are calculated using the ITAE criterion for integrating plant with time delay. The twin rotor MIMO system (TRMS) as an integrating plant is verified in our study. Another example with large time delay is studied to check the validity of fractional-order integrator. Both simulation and experimental results are discussed and compared by PI λ with classical PI. The result proves the effectiveness of the fractional order controller.