Loading...
Search for:
in-control
0.004 seconds
Compensation by fractional-order phase-lead/lag compensators
, Article IET Control Theory and Applications ; Volume 8, Issue 5 , 2014 , Pages 319-329 ; ISSN: 17518644 ; Tavakoli Kakhki, M ; Sharif University of Technology
Abstract
This study deals with a generalised version of lead/lag compensators known as fractional-order lead/lag compensators. Exact and simple formulas are found for designing this introduced type of fractional-order compensators in order to provide the required magnitude and phase at a given frequency. Also, the region in the phase-magnitude plane, which is accessible by these compensators, is analytically found. Moreover, numerical examples and experimental results are presented to show the applicability of the achievements of this study in control system design
A probabilistic framework to achieve robust non-fragile tuning methods: PD control of IPD-modeled processes
, Article International Journal of Robust and Nonlinear Control ; 2021 ; 10498923 (ISSN) ; Tavazoei, M. S ; Sharif University of Technology
John Wiley and Sons Ltd
2021
Abstract
We introduce a novel probabilistic framework to achieve robust non-fragile tuning methods in control of processes with parametric uncertainties. We consider probability distributions to model the process parameters' uncertainties. First, we propose the tuning framework in a general setting. Then, as an illustration, we apply it to PD control of IPD-modeled processes. It is noteworthy that the proposed tuning method is robust against the considered parametric uncertainties. Also, to empower the proposed robust tuning method in the viewpoint of non-fragility, we utilize a centroid approach. Selecting the form of the probabilistic framework, we empirically observe some of the popular tuning...
A probabilistic framework to achieve robust non-fragile tuning methods: PD control of IPD-modeled processes
, Article International Journal of Robust and Nonlinear Control ; Volume 32, Issue 18 , 2022 , Pages 9593-9609 ; 10498923 (ISSN) ; Tavazoei, M. S ; Sharif University of Technology
John Wiley and Sons Ltd
2022
Abstract
We introduce a novel probabilistic framework to achieve robust non-fragile tuning methods in control of processes with parametric uncertainties. We consider probability distributions to model the process parameters' uncertainties. First, we propose the tuning framework in a general setting. Then, as an illustration, we apply it to PD control of IPD-modeled processes. It is noteworthy that the proposed tuning method is robust against the considered parametric uncertainties. Also, to empower the proposed robust tuning method in the viewpoint of non-fragility, we utilize a centroid approach. Selecting the form of the probabilistic framework, we empirically observe some of the popular tuning...
The Challenges in Iran for Successful Implementation of Directorial Patterns; Focus on PMBOK and PRINCE2
, M.Sc. Thesis Sharif University of Technology ; Rahimzadeh Rofouei, Fayyaz (Supervisor)
Abstract
Project Management has clearly designed to achieve a successful outcome of the projects. However, without a proper practicing, it might convey a different result. Companies are increasingly using organizational project management in their work to achieve company goals. The purpose of this study is to identify the challenges in Iran for successful implementation of directorial patterns based on the PMBoK (Project Management Body of Knowledge) and PRINCE2 (PRojects IN Controlled Environment-2nd Version). This paper presents the results of a study aiming at investigating the impacts of implementing project management processes of PMBOK and PRINCE2 and themes within Iranian construction...
Preoxidation Study of Fe-Ni-Co (KOVAR) Alloy on Glass to Metal Sealing Performance
, M.Sc. Thesis Sharif University of Technology ; Askari, Masoud (Supervisor) ; Kaflou, Ali (Supervisor)
Abstract
The Fe-Ni-Co alloy to borosilicate glass seals have been used for many years as hermetic and electrically insulating seals. It is not only excellent in thermal expansion matching but also in good wettability and bond strength too. Oxidation of Kovar was performed in Water vapor, Saturated Nitrogen and N2-H2-H2O atmosphere in tube furnace. Oxide layer composition and thickness changed by varying in oxidation temperature and time. XRD analysis showed different Iron oxides in oxide layer, FeO, Fe3O4 and Fe2O3. However in the third atmosphere no Hematite observed. Increasing oxidation temperature and time result in increasing sample weight gains and roughness. Oxide layer microstructure also was...
From traditional to fractional PI control: A key for generalization
, Article IEEE Industrial Electronics Magazine ; Volume 6, Issue 3 , 2012 , Pages 41-51 ; 19324529 (ISSN) ; Sharif University of Technology
IEEE
2012
Abstract
Proportional-integral (PI) controllers are the most common form of feedback used in industrial applications today [1][3]. The use of proportional and integral feedback also has a long history of practical applications [4]. For example, in the middle of the 18th century, centrifugal governors as the proportional feedback were applied to regulate the speed of windmills [5]. By the 19th century, it was known that using integral feedback could remove the offsets appearing in working with governors [6]. At present, PI control, still a very basic form of feedback, is also one of the first solutions often considered in the control of industrial systems [7]. On the other hand, in some applications,...
Improved optimal control technique for control of parallel three- phase inverters
, Article 2009 International Conference on Electric Power and Energy Conversion Systems, EPECS 2009, Sharjah, 10 November 2009 through 12 November 2009 ; 2009 ; 9789948427155 (ISBN) ; Mokhtari, H ; Sharif University of Technology
Abstract
This paper proposes a high performance voltage tracking and current sharing among parallel connected inverters by applying optimal control and minimizing the cost function. The control system forces the voltage of load to track the voltage reference, and the current of all inverters becomes equal. Therefore, both current sharing and voltage tracking are obtained. In addition, the smallest input energy and simplicity in control circuit are the other advantages of the suggested method. To show the performance of the proposed control scheme, the simulations with two-modular practical systems are performed and the results are provided. The results indicate that the control objectives are...
Robust fractional-order compensation in the presence of uncertainty in a pole/zero of the plant
, Article IEEE Transactions on Control Systems Technology ; Volume 26, Issue 3 , May , 2018 , Pages 797-812 ; 10636536 (ISSN) ; Tavazoei, M. S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
This paper deals with robust frequency compensation in control of fractional-order plants with an uncertain fractional pole/zero (or specially in control of integer-order plants with an uncertain pole/zero). The specifications yielding a robust compensation are introduced, and fractional-order compensators are proposed for satisfying these specifications in the set-point tracking control of the above-mentioned plants. Also, the infinite ranges for the uncertain parameter of the plant, in which satisfying robust compensation specifications is possible by the obtained compensators, are exactly specified. Furthermore, the stability of the obtained control system is analytically analyzed....
New control charts for monitoring covariance matrix with individual observations
, Article Quality and Reliability Engineering International ; Volume 25, Issue 7 , 2009 , Pages 821-838 ; 07488017 (ISSN) ; Akhavan Niaki, T ; Sharif University of Technology
2009
Abstract
It has recently been shown that the performance of multivariate exponentially weighted mean square and multivariate exponentially weighted moving variance charts of Huwang et al. (J. Qual. Technol. 2007; 39:258-278) in monitoring the variability of a multivariate process for individual observations is better than existing schemes. Both of these control charts monitor a distinct matrix which is an estimator of the in-control covariance matrix. Instead of using the trace, in this paper, we propose a L1-norm and a L2-norm-based distance between diagonal elements of the estimators from their expected values to design new control charts in monitoring the covariance matrix of a multivariate...
Dynamic-programming-based failure-tolerant control for satellite with thrusters in 6-DOF motion
, Article Advances in Space Research ; Volume 65, Issue 12 , 2020 , Pages 2857-2877 ; Assadian, N ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
In this paper, a dynamic-programming approach to the coupled translational and rotational control of thruster-driven spacecraft is studied. To reduce the complexity of the problem, dynamic-programming-based optimal policies are calculated using decoupled position and attitude dynamics with generalized forces and torques as controls. A quadratic-programming-based control allocation is then used to map the controls to actuator commands. To control the spacecraft in the event of thruster failure, both the dynamic programming policies and control allocation are reconfigured to cope with the losses in controls. The control allocation parameters are adjusted dynamically to ensure the satellite...
A hybrid method of artificial neural networks and simulated annealing in monitoring auto-correlated multi-attribute processes
, Article International Journal of Advanced Manufacturing Technology ; Volume 56, Issue 5-8 , 2011 , Pages 777-788 ; 02683768 (ISSN) ; Akbari Nasaji, S ; Sharif University of Technology
Abstract
The quality characteristics of both manufacturing and service industries include not only the variables but the attributes as well. While a substantial research have been performed on auto-correlated variables, little attempt has been fulfilled for auto-correlated attributes. Ignoring the imbedded autocorrelation structure in constructing control charts cause not only the in-control run length to decrease, but also the false alarms to increase. To overcome these shortcomings, in this research, an autoregressive vector first models the autocorrelation structure of the process data. Then, a modified Elman neural network is developed to generate simulated data using the ARTA algorithm. Next, a...
Control of microgrids: Aspects and prospects
, Article 2011 International Conference on Networking, Sensing and Control, ICNSC 2011, 11 April 2011 through 13 April 2011 ; April , 2011 , Pages 38-43 ; 9781424495702 (ISBN) ; Azizi, S ; Ranjbar, A. M ; Sharif University of Technology
2011
Abstract
A microgrid is a controllable component of the smart grid defined as a part of distribution network capable of supplying its own local load even in the case of disconnection from the upstream network. Microgrids incorporate large amount of renewable and non-renewable distributed generation (DG) that are connected to the system either directly or by power electronics (PE) interface. The diversity of technologies used in DGs and loads, high penetration of DGs, economic operation of DGs, dynamics of low-inertia conventional DGs and PE interfaced inertialess DGs and smart operation by means of enhanced communication infrastructure have raised challenges in widespread utilization of microgrids as...
Adaptive control of robot manipulators including actuator dynamics and without joint torque measurement
, Article 2010 IEEE International Conference on Robotics and Automation, ICRA 2010, Anchorage, AK, 3 May 2010 through 7 May 2010 ; 2010 , Pages 4639-4644 ; 10504729 (ISSN) ; 9781424450381 (ISBN) ; Namvar, M ; Sharif University of Technology
2010
Abstract
Ignoring actuator dynamics in control of rigid manipulators can in practice result in performance degradation or loss of system stability. However, consideration of actuator dynamics usually requires measurement of robot joint torques. This paper addresses motion tracking control of an n-DOF rigid robot by taking into account its actuator dynamics. Joint torque measurement is avoided by using an adaptive observer. The backstepping technique is adopted to develop a dynamically smooth adaptive nonlinear controller dealing with uncertainties in manipulator and actuator dynamics. Semi-global convergence of motion tracking errors as well as torque estimation error are proven without any...
Artificial neural network in applying multi attribute control chart for AR processes
, Article 2010 The 2nd International Conference on Computer and Automation Engineering, ICCAE 2010, 26 February 2010 through 28 February 2010, Singapore ; Volume 5 , 2010 , Pages 216-220 ; 9781424455850 (ISBN) ; Akbari Nasaji, S ; Sharif University of Technology
2010
Abstract
Quality characteristics are subject of both manufacturing and service industries, which include not only the variables but the attributes as well. In Quality Control area substantial research has been done for Auto-correlated variables; however, no attempt was done for Auto-correlated attributes. Ignoring the autocorrelation structure in constructing control charts cause the in-control run length to decrease, and the false alarms to increase as such. In this article we develop a new methodology based upon the modified Elman neural network capabilities to overcome this problem. Moreover, instead of back propagation, simulated annealing is suggested as an alternative training technique that is...
Control of thermo magnetic heat transfer in porous cavity with Baffle(s)
, Article ASME International Mechanical Engineering Congress and Exposition, Proceedings, 13 November 2009 through 19 November 2009 ; Volume 9, Issue PART A , 2010 , Pages 627-631 ; 9780791843826 (ISBN) ; Davoudi, M ; Pirmohammadi, M ; Sharif University of Technology
Abstract
Steady, laminar, natural-convection flow in the presence of a magnetic field in a porous cavity heated from left wall sinusoidally and cooled from right wall is considered. It is well known that unavoidable hydrodynamic movements can be damped with the help of a magnetic field. The Finite Volume method and SIMPLE algorithm for discretizing is used to solve the non-dimensional governing equations. The Convection and Diffusion term of the equations are discretized by Central Difference Scheme (CDS).The numerical procedure has been done over a range of Rayleigh number, Ra, and value of Hartmann number (Ha), 0 ≤ Ha ≤ 150 and effect of them is investigated on average and local Nusselt number....
Application of fractional derivative in control functions
, Article Proceedings of the INDICON 2008 IEEE Conference and Exhibition on Control, Communications and Automation, 11 December 2008 through 13 December 2008, Kanpur ; Volume 1 , 2008 , Pages 252-257 ; 9781424427475 (ISBN) ; Haeri, M ; Sharif University of Technology
2008
Abstract
Application of fractional derivative in control problems such as sliding surface design in Sliding Mode Control, training of MLP in neural networks, and parameters updating in Model Reference Adaptive Control is studied in this paper. Use of the fractional derivative increases possibility of improving the control performance by reducing the convergence time in the mentioned control problems. This gain is attained due to the higher degree of freedom exist in the fractional dynamical systems. We study such control problems by replacing the integer order derivative with the fractional order derivative. The performance of the proposed methods is illustrated through computer simulations of gyro...
A checkpointing technique for rollback error recovery in embedded systems
, Article 2006 International Conference on Microelectronics, ICM 2006, Dhahran, 16 December 2006 through 19 December 2006 ; 2006 , Pages 174-177 ; 1424407656 (ISBN); 9781424407651 (ISBN) ; Miremadi, S. G ; Fazeli, M ; Arabian Consulting Engineering Center; Saudi Binladin Group; Advanced Electronics Company; HEIP ; Sharif University of Technology
2006
Abstract
In this paper, a general Checkpointing technique for rollback error recovery for embedded systems is proposed and evaluated. This technique is independent of used processor and employs the most important feature in control flow error detection mechanisms to simplify checkpoint selection and to minimize the overall code overhead. In this way, during the implementation of a control flow checking mechanism, the checkpoints are added to the program. To evaluate the Checkpointing technique, a pre-processor is implemented that selects and adds the checkpoints to three workload programs running in an 8051 microcontroller -based system. The evaluation is based on 3000 experiments for each...
A parameter-tuned genetic algorithm for statistically constrained economic design of multivariate CUSUM control charts: A Taguchi loss approach
, Article International Journal of Systems Science ; Volume 43, Issue 12 , 2012 , Pages 2275-2287 ; 00207721 (ISSN) ; Ershadi, M. J ; Sharif University of Technology
2012
Abstract
In this research, the main parameters of the multivariate cumulative sum (CUSUM) control chart (the reference value k, the control limit H, the sample size n and the sampling interval h) are determined by minimising the Lorenzen-Vance cost function [Lorenzen, T.J., and Vance, L.C. (1986), The Economic Design of Control Charts: A Unified Approach, Technometrics, 28, 3-10], in which the external costs of employing the chart are added. In addition, the model is statistically constrained to achieve desired in-control and out-of-control average run lengths. The Taguchi loss approach is used to model the problem and a genetic algorithm, for which its main parameters are tuned using the response...
Multi-objective minimum entropy controller design for stochastic processes
, Article Proceedings of the 2010 American Control Conference, ACC 2010, 30 June 2010 through 2 July 2010 ; 2010 , Pages 355-360 ; 9781424474264 (ISBN) ; Nobakhti, A ; Wang, H ; Chai, T ; Sharif University of Technology
Abstract
Minimum variance control is an established method in control of systems corrupted by noise. In these cases, as it is not possible to directly control the actual value of the system variables, one aims to reduce the variations instead. However, when the system noises are non-Gaussian, this approach fails because non-Gaussian noise cannot be characterised by simple measures such as variance. In these cases, the Entropy is proposed as a generalisation of the variance measure and the control objective becomes that of minimising the Entropy. Previously a limited form of this problem has been solved using first order Newtonian methods. In this paper, the control objective is first expanded to also...
A new monitoring design for uni-variate statistical quality control charts
, Article Information Sciences ; Volume 180, Issue 6 , 2010 , Pages 1051-1059 ; 00200255 (ISSN) ; Akhavan Niaki, S. T ; Sharif University of Technology
Abstract
In this research, an iterative approach is employed to analyze and classify the states of uni-variate quality control systems. To do this, a measure (called the belief that process is in-control) is first defined and then an equation is developed to update the belief recursively by taking new observations on the quality characteristic under consideration. Finally, the upper and the lower control limits on the belief are derived such that when the updated belief falls outside the control limits an out-of-control alarm is received. In order to understand the proposed methodology and to evaluate its performance, some numerical examples are provided by means of simulation. In these examples, the...