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A fractional PID (PI λ D µ ) controller is an extension of the classical PID controller, employing five tuning parameters rather than just three. General guidelines are available for the effect of classical controller parameters on the time domain specification. However, no guidelines are available for fractional PID controllers, particularly for the order of differentiation ( µ ) and integration ( λ ). To assist with fine tuning, the effect of the order of differentiation and integration parameters on the time domain specifications for various plants are investigated. The relationship with the time domain specification serves as general guideline for manual tuning, and the effect of parameters will also assist with auto-tuning. In this paper, five plants covering integer order as well as non-integer order are simulated. The relationship between time domain specifications is plotted by varying the order of differentiation and integration between 0 and 2. Simulation results have revealed an association between the order of differentiation ( µ ) and the maximum overshoot (MP) for all plants. No other particular behavior was observed with other time domain specifications. However, some remarks on time domains specifications are made from the simulation results. Simulation results were validated using an experimental set up of the quadruple tank system.

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