Stability of negative feedback

2021 ◽  
pp. 377-403
Author(s):  
Geoffrey Brooker
Keyword(s):  
Negative Feedback ◽  
Design Procedure ◽  
Feedback System ◽  
Conditional Stability ◽  
Phase Lag ◽  
Minimum Phase ◽  
Safety Margins ◽  
Nyquist Stability ◽  
Nyquist Plots ◽  
Frequency Dependences

“Stability of negative feedback” discusses the measures that must be taken to guarantee that a negative-feedback system is stable. Examples are given of frequency dependences using Bode and Nyquist plots. Safety margins are quantified by means of gain margins and phase margins; the desirability of a minimum-phase-lag network. A design procedure is formulated. There is discussion of Nyquist (conditional) stability, and how it may be achieved by judicious introduction of a non-linearity. A demonstration circuit shows that these measures can yield Nyquist stability with safety.

scholarly journals Robust guaranteed performance PID controller design for non-minimum phase plants

2018 ◽  
Vol 69 (2) ◽  
pp. 117-127
Author(s):  
Štefan Bucz ◽  
Alena Kozáková ◽  
Vojtech Veselý
Keyword(s):  
Time Domain ◽  
Closed Loop ◽  
Controller Design ◽  
Design Method ◽  
Design Procedure ◽  
Uncertain System ◽  
Harmonic Excitation ◽  
Minimum Phase ◽  
Performance Specification ◽  
Gain Margin

AbstractThe paper presents a new original robust PID design method for non-minimum phase plants to achieve closed-loop performance prescribed by the process technologist in terms of settling time and maximum overshoot, respectively. The proposed design procedure has two steps: first, the uncertain system is identified using external harmonic excitation signal with frequency, second, the controller of the nominal system is designed for specified gain margin. A couple of parameters is obtained from the time domain performance specification using quadratic regression curves, the so-called performance Bparabolas so, as to simultaneously satisfy robust closed-loop stability conditions. The main benefits of the proposed method are universal applicability for systems with both fast and slow dominant dynamics as well as performance specification using time domain criteria. The proposed PID design method has been verified on a set of benchmark systems.

Broadband Dynamic Modification Using Feedforward Control

1995 ◽  
Author(s):  
Thomas E. Alberts ◽  
Hemanshu R. Pota
Keyword(s):  
Steady State ◽  
Feedforward Control ◽  
Design Procedure ◽  
Harmonic Excitation ◽  
Flexible Structure ◽  
Minimum Phase ◽  
Original Result ◽  
Modal Expansion ◽  
General Proof ◽  
Dynamic Modification

Abstract This paper presents a general proof of a result due to Fuller and Burdisso, that asserts that system eigenvalues can be modified using feedforward control. The original result applies to the case of steady-state harmonic excitation. This paper extends that work to allow for broadband excitation. The results apply to any flexible structure representable using modal expansion, and are applicable to systems with non-minimum phase zeros. A design procedure is presented to allow arbitrary assignment of the controlled system’s poles, using a fixed feedforward compensator.

Data-driven Controller Tuning for Non-minimum Phase Plants with Stability Constraints

2014 ◽  
Vol 134 (12) ◽  
pp. 1802-1808
Author(s):  
Ryota Matsuo ◽  
Kazuhiro Yubai ◽  
Daisuke Yashiro ◽  
Junji Hirai
Keyword(s):  
Data Driven ◽  
Minimum Phase ◽  
Controller Tuning

Application of Computational Mechanics to Tire Design—Yesterday, Today, and Tomorrow

2011 ◽  
Vol 39 (4) ◽  
pp. 223-244 ◽  
Author(s):  
Y. Nakajima
Keyword(s):  
Finite Element ◽  
New Technologies ◽  
Computational Mechanics ◽  
Design Procedure ◽  
Side Wall ◽  
Rolling Resistance ◽  
Optimization Techniques ◽  
Stress Strain ◽  
Element Analysis ◽  
Crown Shape

Abstract The tire technology related with the computational mechanics is reviewed from the standpoint of yesterday, today, and tomorrow. Yesterday: A finite element method was developed in the 1950s as a tool of computational mechanics. In the tire manufacturers, finite element analysis (FEA) was started applying to a tire analysis in the beginning of 1970s and this was much earlier than the vehicle industry, electric industry, and others. The main reason was that construction and configurations of a tire were so complicated that analytical approach could not solve many problems related with tire mechanics. Since commercial software was not so popular in 1970s, in-house axisymmetric codes were developed for three kinds of application such as stress/strain, heat conduction, and modal analysis. Since FEA could make the stress/strain visible in a tire, the application area was mainly tire durability. Today: combining FEA with optimization techniques, the tire design procedure is drastically changed in side wall shape, tire crown shape, pitch variation, tire pattern, etc. So the computational mechanics becomes an indispensable tool for tire industry. Furthermore, an insight to improve tire performance is obtained from the optimized solution and the new technologies were created from the insight. Then, FEA is applied to various areas such as hydroplaning and snow traction based on the formulation of fluid–tire interaction. Since the computational mechanics enables us to see what we could not see, new tire patterns were developed by seeing the streamline in tire contact area and shear stress in snow in traction.Tomorrow: The computational mechanics will be applied in multidisciplinary areas and nano-scale areas to create new technologies. The environmental subjects will be more important such as rolling resistance, noise and wear.

Issues on Design of Piled Raft Foundation

2018 ◽  
Vol 14 (1) ◽  
pp. 6057-6061 ◽  
Author(s):  
Padmanaban M S ◽  
J Sreerambabu
Keyword(s):  
Contact Area ◽  
Concrete Slab ◽  
Design Procedure ◽  
Bending Moment ◽  
Foundation Design ◽  
Detailed Review ◽  
Piled Raft ◽  
Piled Raft Foundation ◽  
Raft Foundation ◽  
Influencing Parameters

A piled raft foundation consists of a thick concrete slab reinforced with steel which covers the entire contact area of the structure, in which the raft is supported by a group of piles or a number of individual piles. Bending moment on raft, differential and average settlement, pile and raft geometries are the influencing parameters of the piled raft foundation system. In this paper, a detailed review has been carried out on the issues on the raft foundation design. Also, the existing design procedure was explained.

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