Design of Low-Voltage FO-[PD] Controller for Motion Systems

Rafailia Malatesta,Costas Psychalinos,Stavroula Kapoulea,Ahmed S Elwakil

doi:10.3390/jlpea11020026

Abstract

Fractional-order controllers have gained significant research interest in various practical applications due to the additional degrees of freedom offered in their tuning process. The main contribution of this work is the analog implementation, for the first time in the literature, of a fractional-order controller with a transfer function that is not directly constructed from terms of the fractional-order Laplacian operator. This is achieved using Padé approximation, and the resulting integer-order transfer function is implemented using operational transconductance amplifiers as active elements. Post-layout simulation results verify the validity of the introduced procedure.

Highlights

Approximation of Controller Transfer FunctionInput data include the expansion point (which is the specific frequency value ω pade around which the approximation is performed), and the orders of approximation [m, n] (where m is the number of zeros and n the number of poles) [32]
The concept of a fractional-order proportional-integral-derivative (FO-PID) controller constitutes a generalization of the conventional integer-order PID controller [1]
The performance of the proposed fractional-order controller realizations were evaluated using the Cadence IC design suite and the MOS transistor models provided by the Austria Mikro Systeme (AMS) 0.35 μm CMOS Design Kit

Summary

Approximation of Controller Transfer Function

Input data include the expansion point (which is the specific frequency value ω pade around which the approximation is performed), and the orders of approximation [m, n] (where m is the number of zeros and n the number of poles) [32]. This method is very efficient in the approximation of the filtering characteristics of a transfer function, and results in an integer-order polynomial ratio of the following form. The presented concept is general, in the sense that it is independent of the parameters of the FO-[PD] controller, and from the type of the employed plant, it offers versatility from an implementation point of view

Implementation Aspects

Simulation Results

Conclusions