Title: Superiority of fractional order controllers in limit cycle suppression

Authors: Ameya Anil Kesarkar; N. Selvaganesan

Addresses: Department of Avionics, Indian Institute of Space Science and Technology (IIST), Department of Space, Government of India, Thiruvananthapuram, 695547, India ' Department of Avionics, Indian Institute of Space Science and Technology (IIST), Department of Space, Government of India, Thiruvananthapuram, 695547, India

Abstract: In this paper, we report an interesting advantage of fractional order controllers over integer order ones. It is found that the three-parameter-fractional-controllers such as PI^α and [PI]^α outperform integer PID in limit cycle suppression when designed to meet Wang et al. specifications. An elementary servo plant having separable static backlash non-linearity in its model is considered for the tuning purpose. For this plant, designed PI^α and [PI]^α produce significantly reduced limit cycles in the closed loop non-linear simulation response as compared to PID. The results are further verified with describing function method. Also, the results exhibiting such a 'fractional superiority' for a real time application of precision modular servo experimental set-up are included for the better illustration.

Keywords: nonlinearity; limit cycle suppression; describing function; fractional order controllers; static backlash; Oustaloup approximation; precision modular servo.

DOI: 10.1504/IJAAC.2013.057057

International Journal of Automation and Control, 2013 Vol.7 No.3, pp.166 - 182

Received: 08 May 2013
Accepted: 02 Aug 2013
Published online: 12 Jul 2014 *

Full-text access for editors Full-text access for subscribers Purchase this article Comment on this article