Bogdan D. Ciubotaru
@upb.ro
Department of Automatic Control and Systems Engineering
National University of Science and Technology Politehnica Bucharest
RESEARCH, TEACHING, or OTHER INTERESTS
Control and Systems Engineering, Aerospace Engineering
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Sabin Diaconescu, Florin Stoican, and Bogdan D. Ciubotaru
Springer International Publishing
Ştefan S. Mihai, Florin Stoican, and Bogdan D. Ciubotaru
Springer International Publishing
Andrei Sperilă, Cristian Oară, Bogdan D. Ciubotaru, and Şerban Sabău
Institute of Electrical and Electronics Engineers (IEEE)
For networks of systems, with possibly improper transfer function matrices, we present a design framework that enables <inline-formula><tex-math notation="LaTeX">$\\mathcal {H}_\\infty$</tex-math></inline-formula> control, while imposing sparsity constraints on the coprime factors of the controller. We propose a convex and iterative optimization procedure with guaranteed convergence to obtain distributed controllers. By exploiting the robustness-oriented nature of our proposed approach, we provide the means to obtain sparse representations of our control laws that may not be directly supported by the nominal model of the network.
Ştefan S. Mihai, Florin Stoican, and Bogdan D. Ciubotaru
IEEE
This paper provides a combinatorial interpretation for the explicit solution of the quadratic cost, linear-constrained MPC (model predictive control) problem. We link the Hasse diagram of the lifted feasible domain with the critical regions which partition the parameter space and serve as polyhedral support for the piecewise affine explicit MPC solution.
Ştefan S. Mihai, Florin Stoican, and Bogdan D. Ciubotaru
Elsevier BV
Bogdan D. Ciubotaru, Andrei Sperilă, Sabin Diaconescu, Florin Stoican, Adrian M. Stoica, and Samir Bennani
Elsevier BV
Andrei Sperila, Cristian Oara, and Bogdan D. Ciubotaru
Institute of Electrical and Electronics Engineers (IEEE)
By employing the properties of centered realizations, we devise a modified version of the dual Riccati equation approach to optimal <inline-formula> <tex-math notation="LaTeX">$\\mathcal {H}_{2}$ </tex-math></inline-formula> control for differential-algebraic systems that is guaranteed to be more computationally efficient and numerically accurate than other methods from literature. Moreover, we show that if the optimal controller has an improper transfer function matrix, then all controllers which ensure a finite <inline-formula> <tex-math notation="LaTeX">$\\mathcal {H}_{2}$ </tex-math></inline-formula> norm will share this property.
Andrei Sperilă, Bogdan D. Ciubotaru, and Cristian Oară
Elsevier BV
Florin Stoican, Stefan S. Mihai, and Bogdan D. Ciubotaru
IEEE
This paper analyzes the structure of the constrained optimization problem induced by a typical Model Predictive Control (MPC) problem. The main idea is to exploit the particularities of the feasible domain (namely, that input/state/output constraints describe in fact zonotopic sets) to: i) efficiently describe the solution as a piecewise affine function with polyhedral support; ii) exploit the combinatorial properties of zonotopes to reduce the number of candidate active sets. The results are tested over a numerical example.
Andrei Sperilă, Florin S. Tudor, Bogdan D. Ciubotaru, and Cristian Oară
Elsevier BV
Alexandra Reitu, Andrei Sperilă, and Bogdan D. Ciubotaru
Elsevier BV
Adrian M. Stoica, Teodor V. Chelaru, Florin Stoican, and Bogdan D. Ciubotaru
Elsevier BV
Sabin Diaconescu, Andrei Sperilă, Bogdan D. Ciubotaru, and Adrian M. Stoica
Elsevier BV
Maria G. Macau, Bogdan D. Ciubotaru, and Dan Stefanoiu
IEEE
This paper addresses the problem of modeling the dynamics of a launch vehicle and some control algorithms designed to ensure the stability of the closed-loop system and to meet certain performance requirements. The equations of motion were written taking into account the forces acting on a space launcher and the disturbances that may occur and lead to changes in the desired trajectory without taking into account the effects of nozzle dynamics, propellant motion and bending modes. The formulated structure is brought to state space representation and used in the design of the control algorithms. A comparative analysis of different classical control and adaptive algorithms (PD, PID, MRAC) was performed.
Lavinius I. Gliga, Bogdan D. Ciubotaru, Houcine Chafouk, Dumitru Popescu, and Ciprian Lupu
IEEE
Direct Drive Wind Turbines (DDWTs) are used in newer wind farm installations. They are equipped with Permanent Magnet Synchronous Generators (PMSGs), which offer high efficiency for energy generation, but which are also prone to faults. They account for almost a quarter of the downtime of a DDWT. Machine Current Signature Analysis (MCSA) is often used to look for generator problems, as these impairments introduce supplementary harmonics into the generated currents. The Fast Fourier Transform (FFT) is utilized to compute the spectrum of the currents and to look for these additional harmonics. However, the FFT computes the whole spectrum, while the number of possible faults and the number of introduced harmonics is very low. The Goertzel Algorithm (GA), implemented as a filter - the Goertzel Filter (GF), is presented in this paper as a more efficient alternative to the FFT. The GF was tested in Matlab/Simulink and simulation results prove that it can return the squared magnitude of these harmonics. This information can be used to set thresholds for fault detection within a FDI algorithm.
Bogdan D. Ciubotaru and Marcel Staroswiecki
IEEE
Linear quadratic fault accommodation is addressed. Under process and/or actuator faults, fault accommodation procedures need the controller to be redesigned, which amounts to solving the matrix algebraic Riccati equation (ARE) associated with the post-fault system model. In this respect, direct and iterative ARE solvers are analyzed, providing two different ways of application, namely the progressive respectively classical accommodation, function whether the ARE solution is used either during or after convergence. The longitudinal control of an aircraft under actuator and structural faults is used to illustrate the approaches.
Elena M. Cimpoesu, Bogdan D. Ciubotaru, and Dan Stefanoiu
IEEE
This paper focuses on the design of a Fault Isolation procedure suitable for integration within Fault Detection and Diagnosis schemes which are based on parameter estimation techniques. A brief discussion regarding the structure and functionality of model-based technical diagnosis systems is provided within this context, and a summary of previously obtained results in the field of fault detection and fault identification using the Recursive Least Squares method with exponential weighting and constant forgetting factor is presented. A fault localization procedure is proposed based on these results and on the principles of the directional fault isolation approach. Also, an enhancement is made to the classical model-based fault isolation approach, consisting of using history data in order to increase the accuracy of the associated algorithm. An application example from the field of aircraft control is considered in order to illustrate the performances of the proposed method.
Elena M. Cimpoesu, Bogdan D. Ciubotaru, and Dan Stefanoiu
IEEE
This paper focuses on the use of parameter estimation techniques for the implementation of real-time Fault Detection and Diagnosis schemes that are suitable for closed-loop system operation. A description of the main principles regarding fault detection and identification using parameter estimation is given, along with some considerations on the closed-loop system identification problem. The Recursive Least Squares method with exponential weighting and constant forgetting factor is used for the design of the closed-loop system diagnosis procedure. An application example from the field of aircraft control illustrates the suitability of the proposed solution for complex applications where a state-space representation of the system dynamics is used.
Elena M. Cimpoesu, Bogdan D. Ciubotaru, and Dan Stefanoiu
IEEE
The computational simplicity of Fault Detection and Diagnosis (FDD) schemes based on parameter estimation, as well as their suitability for integrated design with Fault Tolerant Control (FTC), make them attractive from the point of view of their implementation within real-time practical applications. This paper focuses on the advantages that these methods can offer as opposed to state estimation and parity equations based system diagnosis, while also highlighting the disadvantages of the parameter estimation approach in view of identifying the problems that could benefit from a simultaneous state and parameter estimation based scheme. In order to achieve this objective, a system diagnosis procedure is proposed, which makes use of the Recursive Least Squares (RLS) method with exponential weighting and constant forgetting factor in view of detecting the occurrence of a fault within the system, as well as providing the post-fault system model. An application example from the aircraft control field is also presented in order to illustrate the efficiency of the proposed approach.
Bogdan D. Ciubotaru, Marcel Staroswiecki, and Nicolai D. Christov
IEEE
The Exact Model Matching (EMM) problem knows an Approximate Model Matching (AMM) solution in the Fault Tolerant Control (FTC) context, solution obtained using either the Modified Pseudo-Inverse Method (MPIM) or the Classical Robust Optimal Model Matching (CROMM) technique. In this paper, the authors reiterate the AMMsolution with MPIM-CROMM and propose another hybrid technique of MPIM with Generalized Linear Quadratic Regulator (GLQR) stabilization and control correction using one of the ROMM variants, called the Extended approach (EROMM). The specificity of the MPIM-GLQR-EROMM as an AMM solution for FTC is also shown in its application on the B747 short-period model impaired with two structural and actuator faults.
Elena M. Cimpoesu, Bogdan D. Ciubotaru, and Dan Stefanoiu
IEEE
Fault Detection and Diagnosis (FDD) is a research field that has known a rapid development due to the increasing safety and dependability requirements in high-risk applications. Consequently, a significant number of FDD techniques and associated algorithms were developed, and their effectiveness was proven in practice. However, given the current trend that consist of designing and developing integrated real-time risk-management systems for safety-critical installations, it became obvious that most of these techniques, in their original form, fail to provide an efficient solution to the problems related to the implementation of the corresponding FDD schemes in real-time; this paper focuses on the use of parameter estimation techniques for achieving these objectives. First, a global overview of the current state of the FDD research is given, then the most commonly used parameter estimation techniques are described, with an emphasis on the possibility of using them within FDD schemes that respond to the requirements of modern industrial applications.
Bogdan D. Ciubotaru, Marcel Staroswiecki, and Nicolai D. Christov
IEEE
When faults turn the nominal operation to an unstable post-fault regime, the accommodation procedure must recover stability and as much performance of the reference model as possible, ideally attaining perfect Model Matching (MM). In this paper, the authors develop the Modified Pseudo-Inverse Method (MPIM) with the Generalized Linear Quadratic Regulator (GLQR) stabilization using the weighting matrices derived from the Robust Optimal Model Matching (ROMM) approach and show that the MPIM-GLQR technique is the best candidate to solve the MM problem extended with the prescribed stability degree property, as opposed to the classical MPIM with simple LQR stabilization using arbitrary penalties, as was proposed in the original method. The theoretical development presented in the paper is illustrated by an aeronautical example, namely the longitudinal motion control of the B747 aircraft impaired by a structural and an actuator fault.