The frequency response is an important tool for practical and efficient design of control systems. Control techniques based on frequency response are of special interest to dealing with important subjects such as the bandwidth and the cost of feedback. Furthermore, these techniques are easily adapted to deal with the uncertainty of the process to control. Quantitative feedback theory QFT is an ...

Quantitative feedback theory (hereafter referred as QFT), developed by Isaac Horowitz (Horowitz, 1963; Horowitz and Sidi, 1972), is a frequency domain technique utilizing the Nichols chart in order to achieve a desired robust design over a specified region of plant uncertainty. Desired time-domain responses are transformed into frequency domain tolerances, which lead to bounds (or constraints) ...

Design of robust controllers for uncertain non-minimum phase and unstable plants with the Quantitative Feedback Theory (QFT) is addressed in this paper. Several counterexamples including non-minimum phase plants and unstable plants are given to illustrate the errors in Horowitz and Sidi method 7, 5]. It is shown that the stability requirement of the new nominal plants is misused or ignored in t...

Robust control system design for uncertain systems (aka “plants”) is of great practical interest, and their automation is a key concern in the control community [1]. In the last few decades, several robust control methodologies in time as well as frequency domains have been proposed (cf. [1]). Quantitative Feedback Theory (QFT) [2] is a one such frequency-domain controller design technique base...

Development of a new revolutionary quantitative biofractal control methodology for the creation and efficient use of new organic bio-inspired devices using quantitative feedback theory (QFT) will be the focus of this lecture. The non-integer methodology will be addressed in the form of a quantitative biofractal controller architecture, which incorporates ontogentic and epigenetic scalable mecha...

This paper is discussed towards the issue of variations happening in voltage control method DC-DC boost converter. Quantitative feedback theory (QFT) adjusted to efficiently plan a robust PID regulator, which acknowledged utilizing only output plant sensed by sensor. The benefits explained configuration QFT design (Tarakanath Kobaku et al. 25) proved with fact that it disposes problem extra wor...

This paper examines methods to incorporate feedforward loops of known external inputs (output reference) into a multi-input feedback control structure achieve certain robust performance its output. Undoubtedly, can reduce the need for and therefore amplification sensor noise at actuators, as occurs in single-input control. Beyond that, since there are several available inputs, convenient distri...

When the process is highly uncertain, even linear minimum phase systems must sacrifice desirable feedback control benefits to avoid an excessive ‘cost of feedback’, while preserving the robust stability. In this paper, the control structure of supervisory based switching Quantitative Feedback Theory (QFT) control is proposed to control highly uncertain plants. According to this strategy, the un...

Wastewater treatment processes with activated sludge are described in the specialized literature by complex models with nonlinear parameterization, such as for example Activated Sludge Model ASM1, ASM2 or ASM3. Under these conditions, the design of control structures using the state space representation is very difficult. Suitable techniques to approach the control of these processes are using ...