Bogdan D. Ciubotaru

@upb.ro

Department of Automatic Control and Systems Engineering
National University of Science and Technology Politehnica Bucharest



                       

https://researchid.co/bogdan.ciubotaru

RESEARCH, TEACHING, or OTHER INTERESTS

Control and Systems Engineering, Aerospace Engineering

42

Scopus Publications

232

Scholar Citations

8

Scholar h-index

6

Scholar i10-index

Scopus Publications

  • Addressing Missing Data Challenges in Geriatric Health Monitoring: A Study of Statistical and Machine Learning Imputation Methods
    Gabriel-Vasilică Sasu, Bogdan-Iulian Ciubotaru, Nicolae Goga, and Andrei Vasilățeanu
    MDPI AG
    In geriatric healthcare, missing data pose significant challenges, especially in systems used for frailty monitoring in elderly individuals. This study explores advanced imputation techniques used to enhance data quality and maintain model performance in a system designed to detect frailty insights. We introduce missing data mechanisms—Missing Completely at Random (MCAR), Missing at Random (MAR), and Missing Not at Random (MNAR)—into a dataset collected from smart bracelets, simulating real-world conditions. Imputation methods, including Expectation–Maximization (EM), matrix completion, Bayesian networks, K-Nearest Neighbors (KNN), Support Vector Machines (SVMs), Generative Adversarial Imputation Networks (GAINs), Variational Autoencoder (VAE), and GRU-D, were evaluated based on normalized Mean Squared Error (MSE), Mean Absolute Error (MAE), and R2 metrics. The results demonstrate that KNN and SVM consistently outperform other methods across all three mechanisms due to their ability to adapt to diverse patterns of missingness. Specifically, KNN and SVM excel in MAR conditions by leveraging observed data relationships to accurately infer missing values, while their robustness to randomness enables superior performance under MCAR scenarios. In MNAR contexts, KNN and SVM effectively handle unobserved dependencies by identifying underlying patterns in the data, outperforming methods like GRU-D and VAE. These findings highlight the importance of selecting imputation methods based on the characteristics of missing data mechanisms, emphasizing the versatility and reliability of KNN and SVM in healthcare applications. This study advocates for hybrid approaches in healthcare applications like the cINnAMON project, which supports elderly individuals at risk of frailty through non-intrusive home monitoring systems.

  • Frailty Insights Detection System (FIDS)—A Comprehensive and Intuitive Dashboard Using Artificial Intelligence and Web Technologies
    Bogdan-Iulian Ciubotaru, Gabriel-Vasilică Sasu, Nicolae Goga, Andrei Vasilățeanu, Iuliana Marin, Ionel-Bujorel Păvăloiu, and Claudiu Teodor Ion Gligore
    MDPI AG
    Frailty, known as a syndrome affecting the elderly, have a direct impact on both social well-being and body’s ability to function properly. Specific to geriatric healthcare, the early detection of frailty helps the specialists to mitigate risks of severe health outcomes. This article presents the development process of a system used to determine frailty-specific parameters, focusing on easy-to-use, non-intrusive nature and reliance on objectively measured parameters. The multitude of methodologies and metrics involved in frailty assessment emphasize the multidimensional aspects of this process and the lack of a common and widely accepted methodology as being the gold standard. After the research phase, the frailty-specific parameters considered are physical activity, energy expenditure, unintentional weight loss, and exhaustion, along with additional parameters like daily sedentary time, steps history, heart rate, and body mass index. The system architecture, artificial intelligence models, feature selection, and final prototype results are presented. The last section addresses the challenges, limitations, and future work related to the Frailty Insights Detection System (FIDS).

  • Elastic Tube Model Predictive Control With Scaled Zonotopic Sets
    Sabin Diaconescu, Florin Stoican, Bogdan D. Ciubotaru, and Sorin Olaru
    Institute of Electrical and Electronics Engineers (IEEE)

  • Tube Model Predictive Control for Flexible Satellite Dynamics
    Sabin Diaconescu, Florin Stoican, and Bogdan D. Ciubotaru
    Springer International Publishing

  • Explicit MPC Solution Using Hasse Diagrams: Construction, Storage and Retrieval
    Ştefan S. Mihai, Florin Stoican, and Bogdan D. Ciubotaru
    Springer International Publishing

  • Distributed Control of Descriptor Networks: A Convex Procedure for Augmented Sparsity
    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.

  • Prototype Results of an Internet of Things System Using Wearables and Artificial Intelligence for the Detection of Frailty in Elderly People
    Bogdan-Iulian Ciubotaru, Gabriel-Vasilică Sasu, Nicolae Goga, Andrei Vasilățeanu, Iuliana Marin, Maria Goga, Ramona Popovici, and Gora Datta
    MDPI AG
    As society moves towards a preventative approach to healthcare, there is growing interest in scientific research involving technology that can monitor and prevent adverse health outcomes. The primary objective of this paper is to develop an Internet of Things (IoT) wearable system based on Fried’s phenotype that is capable of detecting frailty. To determine user requirements, the system’s architecture was designed based on the findings of a questionnaire administered to individuals confirmed to be frail. A functional prototype was successfully developed and tested under real-world conditions. This paper introduces the methodology that was used to analyze the data collected from the prototype. It proposes an interdisciplinary approach to interpret wearable sensor data, providing a comprehensive overview through both visual representations and computational analyses facilitated by machine learning models. The findings of these analyses offer insights into the ways in which different types of activities can be classified and quantified as part of an overall physical activity level, which is recognized as an important indicator of frailty. The results provide the foundations for a new generation of affordable and non-intrusive systems able to detect and assess early signs of frailty.

  • Architecture of a Non-Intrusive IoT System for Frailty Detection in Older People
    Bogdan-Iulian Ciubotaru, Gabriel-Vasilică Sasu, Nicolae Goga, Andrei Vasilateanu, and Alexandru-Filip Popovici
    MDPI AG
    Early detection of frailty is one of the main challenges in the world we live in. Being aware of physiologic and behavior changes can predict and prevent the onset of mental complications for older people. By using modern technologies, one can get insights, which may help detection of different pathologies. In this paper, preliminary results for a novel system to detect early signs of frailty are presented. A prototype was developed and tested in laboratory conditions after requirements and functional capabilities were defined. The main advantages of the proposed architecture are the usage of commercial off-the-shelf (COTS) components and custom mechanisms of security to assure a high level of confidentiality and integrity of user-specific data. Other original elements are its easy-to-use and non-intrusive characteristics.

  • Computing the explicit MPC solution using the Hasse diagram of the lifted feasible domain
    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.

  • On the link between explicit MPC and the face lattice of the lifted feasible domain
    Ştefan S. Mihai, Florin Stoican, and Bogdan D. Ciubotaru
    Elsevier BV

  • Satellite micro-launcher control: An integrated adaptive-robust and nonlinear approach
    Bogdan D. Ciubotaru, Andrei Sperilă, Sabin Diaconescu, Florin Stoican, Adrian M. Stoica, and Samir Bennani
    Elsevier BV

  • H<inf>2</inf>Output Feedback Control of Differential-Algebraic Systems
    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.

  • The optimal H<inf>2</inf> controller for generalized discrete-time systems
    Andrei Sperilă, Bogdan D. Ciubotaru, and Cristian Oară
    Elsevier BV

  • A quantitative research for determining the user requirements for developing a system to assist people with frailty
    Bogdan-Iulian Ciubotaru, Vasilica-Gabriel Sasu, Andrei Vasilateanu, Nicolae Goga, Ramona Dragomir, and Alexandru-Filip Popovici
    IEEE
    Frailty is a clinical syndrome prevalent among the older population, characterized by unintentional weight loss, exhaustion being associated with a decline in cognitive and physiological functions. Ambient Assisted Living can be used for coping through solutions based on smart devices that help older people to cope with frailty. In this paper, we present a quantitative research to determine the user requirements for developing a system to assist people with frailty.

  • Observations on the complexity of the explicit MPC
    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.

  • A Quantitative Research for Determining the User Requirements for Developing a System to Detect Depression
    Vasilica-Gabriel Sasu, Bogdan-Iulian Ciubotaru, Ramona Popovici, Alexandru-Filip Popovici, Nicolae Goga, and Gora Datta
    IEEE
    Purpose: Smart apps and wearables devices are an increasingly used way in healthcare to monitor a range of functions associated with certain health conditions. Even if in the present there are some devices and applications developed, there is no sufficient evidence of the use of such wearables devices in the detection of some disorders such as depression. Thus, through this paper, we want to address this need and present a quantitative research to determine the user requirements for developing a smart device that can detect depression. Material and Methods: To determine the user requirements for developing a system to detect depression we developed a questionnaire which was applied to 205 participants. Results and conclusions: Such a system addressed to detect depression is of interest among the respondents. The most essential parameters to be monitored refer to sleep quality, level of stress, circadian rhythm, and heart rate. Also, the developed system should prioritize reliability, privacy, security, and ease of use.

  • Extended analysis using nist methodology of sensor data entropy


  • H2 Control for Differential-Algebraic Systems


  • H<inf>∞</inf> control for differential-algebraic systems
    Andrei Sperilă, Florin S. Tudor, Bogdan D. Ciubotaru, and Cristian Oară
    Elsevier BV

  • Fault-tolerant optimal control scheme for satellite micro-launchers
    Alexandra Reitu, Andrei Sperilă, and Bogdan D. Ciubotaru
    Elsevier BV

  • A Kalman filtering approach for systems subject to parametric modeling uncertainties
    Adrian M. Stoica, Teodor V. Chelaru, Florin Stoican, and Bogdan D. Ciubotaru
    Elsevier BV

  • Space micro-launcher H<inf>∞</inf> Control under parametric modeling uncertainties
    Sabin Diaconescu, Andrei Sperilă, Bogdan D. Ciubotaru, and Adrian M. Stoica
    Elsevier BV

  • Analysis of classical and adaptive control algorithms for a space vehicle
    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.

  • Fault diagnosis of a direct drive wind turbine using a bank of goertzel filters
    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.

  • Comparative study of matrix riccati equation solvers for parametric faults accommodation
    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.

RECENT SCHOLAR PUBLICATIONS

  • Computing the explicit MPC solution in the constrained zonotope case
    F Stoican, ŞS Mihai, M Mnnigmann, BD Ciubotaru
    2024 IEEE 63rd Conference on Decision and Control (CDC), 1055-1060 2024

  • Elastic Tube Model Predictive Control With Scaled Zonotopic Sets
    S Diaconescu, F Stoican, BD Ciubotaru, S Olaru
    IEEE Control Systems Letters 2024

  • Distributed control of descriptor networks: A convex procedure for augmented sparsity
    A Sperilă, C Oară, BD Ciubotaru, Ş Sabău
    IEEE Transactions on Automatic Control 68 (12), 8067-8074 2023

  • Computing the explicit MPC solution using the Hasse diagram of the lifted feasible domain
    ŞS Mihai, F Stoican, BD Ciubotaru
    2023 European Control Conference (ECC), 1-7 2023

  • Computing the explicit MPC solution using the Hasse diagram of the lifted feasible domain
    F Stoican, BD Ciubotaru
    IEEE, 1-7 2023

  • Tube Model Predictive Control for Flexible Satellite Dynamics
    S Diaconescu, F Stoican, BD Ciubotaru
    International Conference on Difference Equations and Applications, 371-387 2022

  • Explicit MPC Solution Using Hasse Diagrams: Construction, Storage and Retrieval
    ŞS Mihai, F Stoican, BD Ciubotaru
    International Conference on Difference Equations and Applications, 353-369 2022

  • Satellite micro-launcher control: An integrated adaptive-robust and nonlinear approach
    BD Ciubotaru, A Sperilă, S Diaconescu, F Stoican, AM Stoica, S Bennani
    Control Engineering Practice 122, 105072 2022

  • On the link between explicit MPC and the face lattice of the lifted feasible domain
    ŞS Mihai, F Stoican, BD Ciubotaru
    IFAC-PapersOnLine 55 (16), 308-313 2022

  • Observations on the complexity of the explicit MPC
    F Stoican, ŞS Mihai, BD Ciubotaru
    2021 60th IEEE Conference on Decision and Control (CDC), 2551-2556 2021

  • The optimal H2 controller for generalized discrete-time systems
    A Sperilă, BD Ciubotaru, C Oară
    Automatica 133, 109889 2021

  • H2 Output Feedback Control of Differential-Algebraic Systems
    A Sperilă, C Oară, BD Ciubotaru
    IEEE Control Systems Letters 6, 542-547 2021

  • ℋ2 Control for Differential-Algebraic Systems
    A Sperilă, BD Ciubotaru, C Oară
    2020 European Control Conference (ECC), 627-632 2020

  • H∞ Control for Differential-Algebraic Systems
    A Sperila, FS Tudor, BD Ciubotaru, C Oara
    Proc. of the 21st IFAC World Congress, 4285-4290 2020

  • Fault-tolerant Optimal Control Scheme for Satellite Micro-launchers
    A Reitu, A Sperilă, BD Ciubotaru
    IFAC-PapersOnLine 53 (2), 4115-4120 2020

  • Analysis of Classical and Adaptive Control Algorithms for a Space Vehicle
    MG Măcău, BD Ciubotaru, D Ştefănoiu
    2019 23rd International Conference on System Theory, Control and Computing 2019

  • Fault diagnosis of a direct drive wind turbine using a bank of Goertzel filters
    LI Gliga, BD Ciubotaru, H Chafouk, D Popescu, C Lupu
    2019 6th International Conference on Control, Decision and Information 2019

  • Optimal reconfiguration of systems in aeronautics
    B Ciubotaru
     2019

  • A Kalman filtering approach for systems subject to parametric modeling uncertainties
    AM Stoica, TV Chelaru, F Stoican, BD Ciubotaru
    IFAC-PapersOnLine 52 (12), 400-404 2019

  • Space Micro-launcher H∞ control under parametric modeling uncertainties
    S Diaconescu, A Sperilă, BD Ciubotaru, AM Stoica
    IFAC-PapersOnLine 52 (12), 91-96 2019

MOST CITED SCHOLAR PUBLICATIONS

  • Fault detection and diagnosis using parameter estimation with recursive least squares
    EM Cimpoesu, BD Ciubotaru, D Stefanoiu
    2013 19th International Conference on Control Systems and Computer Science 2013
    Citations: 38

  • Switching solution for multiple-models control systems
    C Lupu, D Popescu, B Ciubotaru, C Petrescu, G Florea
    2006 14th Mediterranean Conference on Control and Automation, 1-6 2006
    Citations: 36

  • Fault tolerant control of the Boeing 747 short-period mode using the admissible model matching technique
    B Ciubotaru, M Staroswiecki, C Christophe
    IFAC Proceedings Volumes 39 (13), 819-824 2006
    Citations: 20

  • Automatica industriala
    D Popescu, D Stefanoiu, C Lupu, C Petrescu, B Ciubotaru, C Dimon
    Bucuresti: Agir, 384 2006
    Citations: 20

  • Industrial Process Control
    D Popescu, D Stefanoiu, C Lupu, C Petrescu, B Ciubotaru, C Dimon
    AGIR Press, Bucharest 2006
    Citations: 17

  • Industrial Automation
    D Popescu, D Stefanoiu, C Lupu, C Petrescu, B Ciubotaru, C Dimon
    Editura AGIR, Bucuresti 2006
    Citations: 14

  • Comparative study of matrix Riccati equation solvers for parametric faults accommodation
    BD Ciubotaru, M Staroswiecki
    2009 European Control Conference (ECC), 1371-1376 2009
    Citations: 9

  • A Kalman filtering approach for systems subject to parametric modeling uncertainties
    AM Stoica, TV Chelaru, F Stoican, BD Ciubotaru
    IFAC-PapersOnLine 52 (12), 400-404 2019
    Citations: 8

  • Industrial Automatics
    D Popescu, D Stefanoiu, C Lupu, C Petrescu, B Ciubotaru, C Dimon
    Ed. AGIR, Bucharest 2006
    Citations: 7

  • Short investigation on system diagnosis regarding parameter estimation
    EM Cimpoeşu, BD Ciubotaru, D Ştefănoiu
    2012 1st International Conference on Systems and Computer Science (ICSCS), 1-6 2012
    Citations: 6

  • Fault tolerant control of the B747 short-period mode using progressive accommodation
    B Ciubotaru, M Staroswiecki
    2006 IEEE Conference on Computer Aided Control System Design, 2006 IEEE 2006
    Citations: 6

  • Distributed control of descriptor networks: A convex procedure for augmented sparsity
    A Sperilă, C Oară, BD Ciubotaru, Ş Sabău
    IEEE Transactions on Automatic Control 68 (12), 8067-8074 2023
    Citations: 5

  • On the link between explicit MPC and the face lattice of the lifted feasible domain
    ŞS Mihai, F Stoican, BD Ciubotaru
    IFAC-PapersOnLine 55 (16), 308-313 2022
    Citations: 5

  • Fault diagnosis of a direct drive wind turbine using a bank of Goertzel filters
    LI Gliga, BD Ciubotaru, H Chafouk, D Popescu, C Lupu
    2019 6th International Conference on Control, Decision and Information 2019
    Citations: 5

  • Fault detection and identification using parameter estimation techniques
    EM Cimpoesu, BD Ciubotaru, D Stefanoiu
    UPB Scientific Bulletin, Series C 76 (2), 3-14 2014
    Citations: 5

  • Modified pseudo-inverse method with generalized linear quadratic regulator for fault tolerant model matching with prescribed stability degree
    BD Ciubotaru, M Staroswiecki, ND Christov
    2011 50th IEEE conference on decision and control and European control 2011
    Citations: 5

  • Anytime algorithm for parametric faults accommodation under handling quality constraints
    BD Ciubotaru, M Staroswiecki
    IFAC Proceedings Volumes 42 (8), 887-892 2009
    Citations: 5

  • Model following with output feedback for fault tolerant control
    EM Cimpoeşu, BD Ciubotaru, D Popescu
    15th International Conference on System Theory, Control and Computing, 1-6 2011
    Citations: 4

  • Extension of modified pseudo-inverse method with generalized linear quadratic stabilization
    BD Ciubotaru, M Staroswiecki
    Proceedings of the 2010 American Control Conference, 6222-6224 2010
    Citations: 4

  • Computing the explicit MPC solution using the Hasse diagram of the lifted feasible domain
    ŞS Mihai, F Stoican, BD Ciubotaru
    2023 European Control Conference (ECC), 1-7 2023
    Citations: 2