Continued fractions approximation of the impulse response of fractional-order dynamic systems

Noninteger (fractional)-order controllers are recognised to guarantee better closed-loop performance and robustness with respect to conventional integer order controllers. But irrational transfer functions make time-domain analysis and simulation much difficult. A systematic approach is proposed here for inverting the transfer function of fractional systems of commensurate order. The approach is based on the continued fractions expansion to approximate irrational transfer functions by minimum-phase, stable, rational functions, which can be easily transformed in the time-domain. The accuracy of the designed low-order approximation is shown by simulation results.