Survey paper: A survey on industrial applications of fuzzy control

Important results about two-degree-of-freedom PID controllers are surveyed for the tutorial purpose, including equivalent transformations, various explanations about the effect of the two-degree-of-freedom structure, relation to the preceded-derivative PID and the I-PD con- trollers, and an optimal tuning method.

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Two-Degree-of-Freedom PID Controllers

In this paper, we study the global properties of a class of human immunodeficiency virus (HIV) models. The basic model is a 5-dimensional nonlinear ODEs that describes the interaction of the HIV with two target cells, CD4+ T cells and macrophages. An HIV model with exposed state and a model with nonlinear incidence rate are also analyzed. Lyapunov functions are constructed to establish the global asymptotic stability of the uninfected and infected steady states. We have proven that if the basic reproduction number R 0 is less than unity, then the uninfected steady state is globally asymptotically stable. If R 0 > 1 (or if the infected steady state exists), then the infected steady state is globally asymptotically stable. In a control system framework, we have shown that the HIV model incorporating the effect of Highly Active AntiRetroviral Therapy (HAART) is globally asymptotically controllable to the uninfected steady state.

Global properties of a class of HIV models

In grid connected photovoltaic (PV) systems, lowpass filters are utilized to reduce injected current harmonics. LCL filters have recently drawn attention for PV system grid interfaces due to their small size and they have shown better attenuation to switching harmonics than simple L filters. However, the LCL filter causes resonance resulting in oscillation and instability issues. This paper proposes an effective active damping technique by introducing a two-degree-of-freedom (2DOF) PID control structure. The 2DOF control structure allows the independent action of PI and D terms giving two degrees of freedom. The design is based on a typical three-phase grid-tied PV system. The active damping control loop is formed by using the existing grid side inductor currents and thus eliminating the need of additional sensors. The relative stability is illustrated in frequency domain by using bode plots. A real-time hardware-in-loop study is performed to validate the performance of the proposed 2DOF technique to damp out the LCL filter resonance.

Two Degrees of Freedom Active Damping Technique for $LCL$ Filter-Based Grid Connected PV Systems

As an alternative to both classical PID-type and modern model-based approaches to solving control problems, active disturbance rejection control (ADRC) has gained significant traction in recent years. With its simple tuning method and robustness against process parameter variations, it puts itself forward as a valuable addition to the toolbox of control engineering practitioners. This article aims at providing a single-source introduction and reference to linear ADRC with this audience in mind. A simulative study is carried out using generic first- and second-order plants to enable a quick visual assessment of the abilities of ADRC. Finally, a modified form of the discrete-time case is introduced to speed up real-time implementations as necessary in applications with high dynamic requirements.

A Simulative Study on Active Disturbance Rejection Control (ADRC) as a Control Tool for Practitioners

Optimal Parameters of Two-Degrees-of-Freedom PID Control Systems

The tuning problem of two-degree-of-freedom PID (2DOF-PID) controllers is studied. The focus is placed on the effects of the location where the major disturbance enters into the plant. First, analysis is made about their effects on the response curves, and then the optimal 2DOF-PID parameters are recalculated assuming generalized location of the disturbance entrance using the two-step optimization method proposed by the authors in the previous report. The results are studied from the viewpoint of the overall performance and a guideline of parameter tuning is presented.

On Tuning of Two-Degree-of-Freedom PID Controllers with Consideration on Location of Disturbance Input

An adjusting unit in a feedback loop for controlling a hydraulically operated-type load mechanism consists of two portions both adapted to effect proportional action and derivative action. Weights are applied to these two portions independently. Hence, an output y can be made to follow sudden changes in a target value r with fast response without the occurrence of overshoots, and the effect of a disturbance input w is alleviated to a maximum. In addition, since integral action is not effected in the adjusting portions, the term of 1 /s 2 is not included in transfer functions of inputs and outputs, thereby realizing stability of control.

Hydraulic servo-type material testing apparatus

PROBLEM TO BE SOLVED: To provide a hydraulic servo type material testing machine capable of optimizing both command responsiveness and disturbance responsiveness, and stabilizing control. SOLUTION: An output y is tracked by high responsiveness and influence of a disturbance input w is minimized without causing an overshoot to an abrupt change of a command r by composing an adjusting part 52 in a feedback loop for controlling a hydraulic drive type loading mechanism 14 from two portions 52a and 52b respectively executing proportional action and derivative action and providing a means of individually applying weight to both portions. Since integral action is not executed in the adjusting parts 52a and 52b, a term of 1/s 2 is eliminated from transfer functions of input and output and the control is stabilized. COPYRIGHT: (C)2003,JPO

Hidefumi Taguchi

Papers

Two-Degree-of-Freedom PID Controllers

Optimal Parameters of Two-Degrees-of-Freedom PID Control Systems

On Tuning of Two-Degree-of-Freedom PID Controllers with Consideration on Location of Disturbance Input

Hydraulic servo-type material testing apparatus

Hydraulic servo type material testing machine