Synthesis of feedback systems with large plant ignorance for prescribed time-domain tolerances†

Horowitz, Isaac; Sidi, Marcel J.

doi:10.1080/00207177208932261

Cited by 452 publications

(164 citation statements)

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“…Under the assumption of parametric uncertainty 1 in the plant, the uncertainty templates of G o (jω) at high frequencies approach a vertical line in the Nichols chart. Hence, to ensure that the specified minimum amount of damping is maintained at high frequencies despite the presence of uncertainty, the M circle is translated downwards by a specific amount, resulting in the so-called "universal high frequency boundary", which should not be penetrated by the nominal open-loop response [4]. This contour will be denoted by B in the sequel.…”

Section: F(s)mentioning

confidence: 99%

“…If the specifications are feasible, the best design is considered to be the one for which the specifications are met as tightly as possible. This is in order to avoid the possibility of "overdesigning" the system using unnecessarily large gains/bandwidth, which can result in measurement noise amplification and potential instability due to parasitics and highfrequency unmodelled dynamics [3], [4]. A compromise between controller complexity and a "tight" design has to be made in many cases.…”

Section: Optimal Design Of Pid Controllersmentioning

confidence: 99%

“…In comparison to other optimisation-based robust control methods, QFT offers a number of advantages. These include, (i) the ability to assess quantitatively the "cost of feedback" [3], [4], [5], (ii) the ability to take into account phase information in the design process (which is lost if, e.g. singular values are used as the design parameters), and , (iii) the ability to provide "design transparency", i.e.…”

Section: Introductionmentioning

confidence: 99%

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Optimal design of PID controllers using the QFT method

Zolotas

Halikias

1999

IEE Proceedings - Control Theory and Applications

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Section: F(s)mentioning

confidence: 99%

Section: Optimal Design Of Pid Controllersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Optimal design of PID controllers using the QFT method

Zolotas

Halikias

1999

IEE Proceedings - Control Theory and Applications

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Section: Iintroductionmentioning

confidence: 99%

“…Therefore, a single fixed controller in such systems is found among the 'robust control' family. Quantitative feedback theory (QFT) is a robust feedback control-system design technique which allows the direct design to closed-loop robust performance and stability specifications [4].QFT not only uses transfer function approach but also takes phase information into account in the design process. The unique feature of QFT is that the performance specifications are expressed as bounds on the frequency-domain response.…”

mentioning

confidence: 99%

Control of Two Link SCARA Robot Using Quantitative Feedback Theory

Rao¹,

Raja²,

Kumar³

2014

IJAREEIE

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SCARA Robots are mainly suitable for pick-and-place operations such as part handling, assembly, etc. Till now, many controllers are designed (like Trial and error, ZN PID and IMC etc) to control a Scara robot to meet desired position. The main drawbacks of those controllers are if plant parameter changes automatically system performance changes. In this paper, to overcome this drawback Quantitative Feedback Theory (QFT) has proposed for single and two link SCARA Robot. KEYWORDS: SCARA, QFT, Robust Controller, IMC, PID I.INTRODUCTIONSCARA (Selective Compliance assembly Robot Arm) robots are horizontally articulated manipulator with a vertical joint at the wrist end. Generally the robot configuration has one vertical (linear) and two revolute joints, it was designed by Professor Makino of Yamanashi University, Japan, and they are ideally suited for operations in which the vertical motion requirements are small compared to the horizontal motion requirements. Such an application would be assembly work where parts are picked up from a parts holder and moved along a nearly horizontal path to the unit being assembled. Fig.1 shows the Two link scara robot model. Potential problems arise mainly due to the positioning errors in assembly. The Adaptive and model-based control strategies cannot overcome the structure of uncertainties of a robotic system . Dynamic models of robot manipulators consist of highly non-linear coupled second-order differential equations. Non-linearity and parameter variations in real systems prevents, ordinary linear time-invariant control schemes achieving a satisfactory control performance. Linearization techniques for the robust control of robot manipulators with uncertainty have been the subject of many research studies. The SCARA robot is used for clean-room applications, such as wafer and disk handling in the electronics industry. It performs many tasks in a fraction of the time it would take a human. Whether constructing something intricate, such as a computer motherboard, or large and hulking, such as the frame of an 18-wheel semi truck, this tool helps increase production and lower costs because of its efficiency.Many practical systems that have high uncertainty levels in their open-loop transfer functions which makes it very difficult to create suitable stability margins and good performance in command following problems for a closed-loop system. Therefore, a single fixed controller in such systems is found among the 'robust control' family. Quantitative feedback theory (QFT) is a robust feedback control-system design technique which allows the direct design to closed-loop robust performance and stability specifications [4].QFT not only uses transfer function approach but also takes phase information into account in the design process. The unique feature of QFT is that the performance specifications are expressed as bounds on the frequency-domain response. Meeting these bounds implies a corresponding approximate closed-loop realization of the time-domain response bounds for a gi...

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