Control systems design via a quantitative feedback theory approach

A MATLAB toolbox for the design of control systems using a quantitative feedback theory (QFT) is being developed. The toolbox will consist of a number of independent routines associated with different tasks in the QFT design process. The particular variant of QFT considered is a development of the work by East (1982), in which the plant uncertainties and the desired plant performance tolerances are expressed as circular disks in the Nyquist plane. The toolbox will include a number of routines for the input of uncertain plants and the specification of the desired closed loop performance (tolerances). From this the nominal loop gain, which ensures that the variation of the closed loop is less than the variation in the tolerances, can be found. An iterative routine, using Bode integrals, is then used to determine a realisable loop controller which satisfies the loop gain previously calculated. Finally a pre-filter is calculated to ensure that the closed loop performance is within the specified tolerances