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Paper details
Number 2 - June 2019
Volume 29 - 2019
Frequency response based curve fitting approximation of fractional-order PID controllers
Kishore Bingi, Rosdiazli Ibrahim, Mohd Noh Karsiti, Sabo Miya Hassam, Vivekananda Rajah Harindran
Abstract
Fractional-order PID (FOPID) controllers have been used extensively in many control applications to achieve robust control
performance. To implement these controllers, curve fitting approximation techniques are widely employed to obtain
integer-order approximation of FOPID. The most popular and widely used approximation techniques include the Oustaloup,
Matsuda and Cheraff approaches. However, these methods are unable to achieve the best approximation due to the limitation
in the desired frequency range. Thus, this paper proposes a simple curve fitting based integer-order approximation
method for a fractional-order integrator/differentiator using frequency response. The advantage of this technique is that it
is simple and can fit the entire desired frequency range. Simulation results in the frequency domain show that the proposed
approach produces better parameter approximation for the desired frequency range compared with the Oustaloup, refined
Oustaloup and Matsuda techniques. Furthermore, time domain and stability analyses also validate the frequency domain
results.
Keywords
curve fitting, fractional-order PID controller, frequency response, integer-order approximation, Oustaloup approximation, Matsuda approximation