On the Rational Representation of Fractional Order Lead Compensator using Pade Approximation

Abstract

This paper presents simple, flexible and effective approximation method for fractional order lead-lag compensators. The proposed method relies on a Pade approximation of linear fractional order transfer functions, giving rational approximations of order N accurate enough for control applications as soon as N is greater than 2 or 3. An example of feedback loop incorporating this approximation is adopted from the well-known car suspension problem, wherein an iso-damping property of the closed loop response is achieved, with regard to a variation of the vehicle mass.