This page contains a representative selection of my publications, in reverse chronological order. Use the "»" button to reveal an abstract of each publication, and "«" to hide the abstract again (requires Javascript).

Books

• M. Bernal, A. Sala, Zs. Lendek, T. M. Guerra, Analysis and Synthesis of Nonlinear Control Systems - A Convex Optimisation Approach, Springer Cham, series Studies in Studies in Systems, Decision and Control, vol. 408, 978-3-030-90772-3.
• Zs. Lendek, T. M. Guerra, R. Babuska, B. De Schutter, Stability Analysis and Nonlinear Observer Design Using Takagi-Sugeno Fuzzy Models, Springer Germany, series Studies in Fuzziness and Soft Computing, vol. 262, 978-3-642-16775-1.

Journal papers

• B. Yousuf, R. Herzal, Zs. Lendek, and L. Busoniu, Multi-Agent Active Multi-Target Search with Intermittent Measurements. Control Engineering Practice, vol. 153, no. 106094, 2024. »
  Abstract: Consider a multi-agent system that must find an unknown number of static targets at unknown locations as quickly as possible. To estimate the number and positions of targets from noisy and sometimes missing measurements, we use a customized particle-based probability hypothesis density filter. Novel methods are introduced that select waypoints for the agents in a decoupled manner from taking measurements, which allows optimizing over waypoints arbitrarily far in the environment while taking as many measurements as necessary along the way. Optimization involves control cost, target refinement, and exploration of the environment. Measurements are taken either periodically, or only when they are expected to improve target detection, in an event-triggered manner. All this is done in 2D and 3D environments, for a single agent as well as for multiple homogeneous or heterogeneous agents, leading to a comprehensive framework for (Multi-Agent) Active target Search with Intermittent measurements. In simulations and real-life experiments involving a Parrot Mambo drone and a TurtleBot3 ground robot, the novel framework works better than baselines including lawnmowers, mutual-information-based methods, active search methods, and our earlier exploration-based techniques. «
• M. Susca, V. Mihaly, Zs. Lendek, I-C. Morarescu, Passivity of Linear Singularly Perturbed Systems. IEEE Control Systems Letters, vol. 8, pages 2105-2110, 2024. »
  Abstract: The passivity of singularly perturbed systems (SPSs) is generally studied without taking advantage of the time-scale separation present in this class of systems. To fill this gap, the objective of this letter is to provide easy-to-verify well-posed conditions characterizing the passivity of a perturbation variable-dependent SPS starting from the passivity of its associated reduced-order system. To achieve this goal, we rely on the connection between positive realness and passivity, as well as the notion of phase for multi-input multi-output (MIMO) systems. We use a benchmark DC motor to illustrate that classical reasoning used for stability analysis of SPSs, which is based on the stability of the reduced-order (slow) and boundary layer (fast) subsystems, cannot be applied to guarantee the passivity of an SPS. On top of that, our methodology explains how the time-scale separation can be used to analyze the passivity of general linear time-invariant (LTI) systems. The approach is illustrated on a numerical example. «
• Y. Xia, K. Xiao, Y. Yao, Z. Geng, Zs. Lendek, Fixed-Time Fuzzy Vibration Reduction for Stochastic MEMS Gyroscopes with Low Communication Resources. IEEE Transactions on fuzzy Systems, vol. 32, no. 8, pages 4220-4233, 2024. »
  Abstract: The microelectromechanical system (MEMS) gyroscope is a complex nonlinear system with multiple variables, strong coupling, and susceptibility to stochastic disturbances. This paper presents an adaptive fuzzy control scheme for stochastic MEMS gyroscopes, with the primary objectives of reducing control vibration and achieving high precision prescribed performance tracking with low communication resources within a fixed-time backstepping framework. To address the stochastic disturbances and unknown nonlinear system dynamics, the interval type-3 fuzzy logic system (IT3FLS) is introduced. Additionally, a novel quadratic prescribed performance function (QPPF) is proposed to ensure satisfactory transient and steady-state performance of the system while mitigating initial control vibrations during fast error convergence. Furthermore, an event-triggered mechanism (ETM) is developed using a switching threshold strategy to minimize the communication load without compromising control accuracy. By utilizing the fixedtime command-filtered backstepping design method and newly introduced error-compensating signals, the issue of “explosion of complexity” is effectively resolved, and filtering errors are adequately compensated. The proposed control scheme guarantees that the tracking errors converge to a predefined set of arbitrarily small residuals in probability. In addition, all the closed-loop signals are within a fixed time bounded in probability (FTBIP). The simulation results validate the effectiveness and superiority of the proposed scheme. «
• B. Yousuf, Zs. Lendek, and L. Busoniu, Exploration-Based Planning for Multiple-Target Search with Real-Drone Results. Sensors, vol. 24, no. 9, pages 2868, 2024. »
  Abstract: Consider a drone that aims to find an unknown number of static targets at unknown positions as quickly as possible. A multi-target particle filter uses imperfect measurements of the target positions to update an intensity function that represents the expected number of targets. We propose a novel receding-horizon planner that selects the next position of the drone by maximizing an objective that combines exploration and target refinement. Confidently localized targets are saved and removed from consideration along with their future measurements. A controller with an obstacle-avoidance component is used to reach the desired waypoints. We demonstrate the performance of our approach through a series of simulations as well as via a real-robot experiment in which a Parrot Mambo drone searches from a constant altitude for targets located on the floor. Target measurements are obtained on-board the drone using segmentation in the camera image, while planning is done off-board. The sensor model is adapted to the application. Both in the simulations and in the experiments, the novel framework works better than the lawnmower and active-search baselines. «
• A. Matyas, Z. Nagy, Zs. Lendek, Stabilization of time-delay nonlinear systems using TS fuzzy models. Fuzzy Sets and Systems, vol. 480, no. 108861, pages 1-16, 2024. »
  Abstract: We propose a controller design method for time-delay nonlinear systems with delays affecting both the states and the inputs, represented by Takagi-Sugeno fuzzy models with nonlinear consequents. To handle the nonlinearities in the consequent we assume that they are slope-bounded. Linear matrix inequality conditions are formulated to design the controller. The obtained results are compared to state-of-the-art approaches and illustrated on two examples. «
• Z. Nagy, Zs. Lendek, L. Busoniu, TS fuzzy observer-based controller design for a class of discrete-time nonlinear systems. IEEE Transactions on Fuzzy Systems, vol. 30, no. 2, pages 555-566, 2022. »
  Abstract: This paper presents an observer-based control design approach for a class of nonlinear discrete-time systems. The model nonlinearities are handled in two ways: 1) a Takagi-Sugeno fzzy representation is used for nonlinearities that depend on measured states, and 2) nonlinearities that depend on unmeasuredstates are kept in their original form and handled usinga slope-bound condition. The observer-based controller design conditions are given as linear matrix inequalities. The approach we propose significantly improves results in the literature by providing less restrictive design conditions. These improvements are illustrated in a detailed analytical and numerical comparison on a synthetic example; while a pendulum-on-a-cart example shows that the approach works both in simulation and in realtime experiments. «
• Zs. Lendek, J. Lauber, Local stabilization of discrete-time nonlinear systems. IEEE Transactions on Fuzzy Systems, vol. 30, no. 1, pages 52-62, 2022. »
  Abstract: This paper considers local stability analysis and local stabilization of discrete-time nonlinear systems represented by Takagi-Sugeno fuzzy models. Conditions are established using Lyapunov functions and controller gains that depend also on past samples. Together with the stability and design conditions, an estimate of the region of attraction is also determined. The developed conditions are discussed and illustrated on several examples. «
• Z. Nagy, Zs. Lendek, L. Busoniu, Observer design for a class of nonlinear systems with nonscalar-input nonlinear consequents. IEEE Control Systems Letters, vol. 54, no. 3, pages 971-976, 2021. »
  Abstract: This paper presents a discrete-time Takagi-Sugeno fuzzy observer design approach for a class of nonlinear systems. Instead of including all the nonlinear terms in the membership functions, some of them are kept as nonlinear consequents, and they need to fulfill a globally Lipschitz condition. The form considered permits nonlinear consequents that depend on nonscalar inputs. The design conditions are defined in terms of linear matrix inequalities, and they are less restrictive than previous conditions from the literature. Two numerical examples highlight the advantages obtained. «
• O. Boncalo, A. Amaricai, Zs. Lendek, Fault tolerant digital data-path design via control feedback loops. Electronics, vol. 9, no. 10, 2020. »
  Abstract: In this paper, we propose a novel fault tolerant methodology for digital pipelined data-paths called Control Feedback Loop Error Decimation (CFLED), that reduces the error magnitude at the outputs. The data-path is regarded from a control perspective as a process affected by perturbations or faults. Based on the corresponding dynamic model, we design feedback control loops with the goal of attenuating the effect of the faults on the output. The correction loops apply correction factors to selected data-path registers from blocks that have their execution rewinded. We apply the proposed methodology on the data-path of a controller designed for a 2-degree of freedom robot arm, and compare the cost and reliability to the generic triple modular redundancy. For Field Programmable Gate Array (FPGA) technology, the solution we propose uses 30% less slices with respect to Triple Modular Redundancy (TMR), while having a third less digital signal processing blocks. Simulation results show that our approach improves the reliability and error detection. «
• V. Estrada-Manzo, Zs. Lendek, T. M. Guerra, An alternative LMI static output feedback control design for discrete-time nonlinear systems represented by Takagi-Sugeno models. ISA Transactions, vol. 84, pages 104-110, 2019. »
  Abstract: This paper presents a static output feedback controller design for discrete-time nonlinear systems exactly represented by Takagi–Sugeno models. By introducing past states in the control law as well as in the Lyapunov function, more relaxed results are obtained. Different conditions in terms of linear matrix inequalities are provided. The proposed conditions are less demanding than the ones in the literature. This is illustrated via numerical examples. «
• Zs. Lendek, Z. Nagy, J. Lauber, Local stabilization of discrete-time TS descriptor systems. Engineering Applications of Artificial Intelligence, vol. 67, pages 409-418, 2018. »
  Abstract: Descriptor models are naturally obtained from the Euler-Lagrange modeling approach to mechanical systems. Since the underlying system is nonlinear, global stabilization and/or tracking is possible only in a limited number of cases. Therefore, we develop conditions for local stabilization and tracking of discrete-time descriptor systems represented by Takagi-Sugeno fuzzy models, using both quadratic and nonquadratic Lyapunov functions. An estimate of the region of attraction is also obtained. The conditions are illustrated on a numerical example and in tracking control for a robot arm. «
• Zs. Lendek, P. Raica, J. Lauber, T. M. Guerra, Finding a stabilizing switching law for switching TS models. International Journal of Systems Science, vol. 47, pages 2762–2772, 2016. »
  Abstract: This paper considers the stabilization of switching nonlinear models by switching between the subsystems. We assume that arbitrary switching between two subsystems is possible once a subsystem has been active for a predefined number of samples. We use a Takagi-Sugeno representation of the models and a switching Lyapunov function is employed to develop sufficient stability conditions. If the conditions are satisfied, we construct a switching law that stabilizes the system. The application of the conditions is illustrated on several examples. «
• V. Estrada-Manzo, T. M. Guerra, Zs. Lendek, Generalized observer design for discrete-time T-S descriptor models. Neurocomputing, vol. 182, pages 210-220, 2016. »
  Abstract: The present paper provides a systematic way to generalize Takagi-Sugeno observer design for discrete-time nonlinear descriptor models. The approach is based on Finsler's lemma, which decouples the observer gains from the Lyapunov function. The results are expressed as strict LMI constraints. To obtain more degrees of freedom without altering the number of LMI constraints and thus relax the conditions, delayed Lyapunov functions and delayed observer gains are considered. Even more relaxed results are developed by extending the approach to alpha-sample variation. The effectiveness of the proposed methods is illustrated via examples «
• V. Estrada-Manzo, Zs. Lendek, T. M. Guerra, Ph. Pudlo, Controller design for discrete-time descriptor models: a systematic LMI approach. IEEE Transactions on Fuzzy Systems, vol. 23 , no. 5, pages 1608–1621, 2015. »
  Abstract: The present paper provides a systematic way to generalize controller design for discrete-time nonlinear descriptor models. The controller synthesis is done using a Takagi-Sugeno representation of the descriptor models and linear matrix inequalities. We propose approaches to exploit the discrete-time nature of the problem by using delayed Lyapunov functions which allow delayed controller gains. In addition, the well-known Finsler’s Lemma is used to avoid the explicit substitution of the closed-loop dynamics. Examples are provided to show the effectiveness of the proposed results. «
• Zs. Lendek, T. M. Guerra, J. Lauber, Controller design for TS models using non-quadratic Lyapunov functions. IEEE Transactions on Cybernetics, vol. 45 , no. 3, pages 453–464, 2015. »
  Abstract: In the last few years, non-quadratic Lyapunov functions have been more and more frequently used in the analysis and controller design for Takagi-Sugeno fuzzy models. In this paper we developed relaxed conditions for controller design using nonquadratic Lyapunov functions and delayed controllers and ive a general framework for the use of such Lyapunov functions. The two controller design methods developed in this framework outperform and generalize current state-of-the-art methods. The proposed methods are extended to robust and H1 control and ®-sample variation. «
• T. M. Guerra, V. Estrada-Manzo, Zs. Lendek, Observer design for Takagi-Sugeno descriptor models: an LMI approach. Automatica, vol. 52 , no. 2, pages 154–159, 2015. »
  Abstract: This paper considers observer design for nonlinear descriptor systems. We propose approaches based on Takagi–Sugeno (TS) models. An extended estimation vector is used in order to keep the descriptor structure of the observer. The design conditions are expressed as linear matrix inequalities. The proposed observer structure, via an intermediate variable as estimated variable, is able to recover the previous observer results for TS descriptors. Moreover, through a direct extension via so-called Finsler’s Lemma, relaxed conditions are obtained. Numerical examples show the effectiveness of the proposed approaches. «
• P. Stano, A. den Dekker, Zs. Lendek, R. Babuska, Convex saturated particle filter. Automatica, vol. 50 , no. 10, pages 2494–2503, 2014. »
  Abstract: In many systems the state variables are defined on a compact set of the state space. To estimate the states of such systems, the constrained particle filters have been used with some success. The performance of the standard particle filters can be improved if the measurement information is used during the importance sampling of the filtering phase. It has been shown that the particles obtained in such a way approximate the true state of the system more accurately. The measurement is incorporated into the filtering algorithm through a user-specified detection function, which aims to detect the saturation as it occurs. The algorithm derived from the aforementioned principle is called the Saturated Particle Filter (SPF). In our previous work we have derived a complete SPF framework for the class of systems with one-dimensional constraints. In this paper we derive a novel Convex SPF that extends our method to multidimensional systems with convex constraints. The effectiveness of the new method is demonstrated using an illustrative example. «
• Zs. Lendek, P. Raica, B. De Schutter, R. Babuska, Analysis and design for continuous-time string-connected Takagi-Sugeno systems. Journal of the Franklin Institute, vol. 351, pages 3577–3592, 2014. »
  Abstract: Distributed systems consist of interconnected, lower-dimensional subsystems. For such systems, distributed analysis and design present several advantages, such as modularity, easier analysis and design, and reduced computational complexity. A special case of distributed systems is when the subsystems are connected in a string. Applications include distributed process control, traffic and communication networks, irrigation systems, hydropower valleys, etc. By exploiting such a structure, in this paper, we propose conditions for the distributed stability analysis of Takagi-Sugeno fuzzy systems connected in a string. These conditions are also extended to observer and controller design and illustrated on numerical examples. «
• Zs. Lendek, A. Sala, P. Garcia, R. Sanchis, Experimental application of Takagi-Sugeno observers and controllers in a nonlinear electromechanical system. Journal of Control Engineering and Applied Informatics, vol. 15 , no. 4, pages 3–14, 2013. »
  Abstract: In this paper, a systematic methodology to design fuzzy Takagi-Sugeno observers and controllers will be used to estimate the angular positions and speeds, as well as to stabilise an experimental mechanical system with 3 degrees of freedom (fixed quadrotor). Takagi-Sugeno observers and controllers are compared to observers and controllers based on the linearized model, both designed with the same optimization criteria and design parameters. Experimental results confirm that Takagi-Sugeno models and observers behave similarly to linear ones around the linearization point, but have a better performance over a larger operating range, as intuitively expected. «
• P. Stano, Zs. Lendek, J. Braaksma, R. Babuska, and C. de Keizer, Parametric Bayesian adaptive filters for nonlinear stochastic dynamical systems: A survey. IEEE Transactions on Cybernetics, vol. 43, no. 6, pages 1607–1624, 2013. »
  Abstract: Nonlinear stochastic dynamical systems are commonly used to model physical processes. For linear and Gaussian systems, the Kalman Filter is optimal in minimum mean squared error sense. However, for nonlinear or non-Gaussian systems the estimation of states or parameters is a challenging problem. Furthermore, it is often required to process data online. Therefore, apart from being accurate, the feasible estimation algorithm also needs to be fast. In this paper we review Bayesian filters which possess the aforementioned properties. Each filter is presented in an easy to implement algorithmic form. We focus on parametric methods, among which we distinguish three types of filters: filters based on analytical approximations (Extended Kalman Filter, Iterated Extended Kalman Filter), filters based on statistical approximations (Unscented Kalman Filter, Central Difference Filter, Gauss-Hermite Filter), and filters based on the Gaussian Sum Approximation (Gaussian Sum Filter). We discuss each of these filters, and compare them on illustrative examples. «
• Zs. Lendek, J. Lauber, and T. M. Guerra, Periodic Lyapunov functions for periodic TS systems. Systems & Control Letters, vol. 62 , no. 4, pages 303–310, 2013. »
  Abstract: In this paper we consider stability analysis and controller design for periodic Takagi-Sugeno fuzzy models. To develop the conditions, we use a switching nonquadratic Lyapunov function defined at the time instants when the subsystems switch. Using the proposed conditions we are able to handle periodic Takagi-Sugeno systems where the local models or even the subsystems are unstable or cannot be stabilized. The application of the conditions is illustrated on numerical examples. «
• P. Stano, Zs. Lendek, R. Babuska, Saturated Particle Filter: Almost Sure Convergence and Improved Resampling. Automatica, vol. 49 , no. 1, pages 147–159, 2013. »
  Abstract: Nonlinear stochastic dynamical systems are widely used to model physical processes. In many practical applications, the state variables are defined on a compact set of the state space, i.e., they are bounded or saturated. To estimate the states of systems with saturated variables, the Saturated Particle Filter (SPF) has recently been developed. This filter exploits the structure of the saturated system using a specific importance sampling distribution. In this paper we investigate the asymptotic properties of the filter, in particular its almost sure convergence to the true posterior PDF. Furthermore, an improved SPF is developed that uses a novel resampling procedure to overcome the practical shortcomings of the original SPF. We prove that this new filter also converges almost surely to the true posterior PDF. Both versions of the SPF are presented in easy to implement algorithmic forms. «
• Zs. Lendek, R. Babuska, B. De Schutter, Sequential stability analysis and observer design for distributed TS fuzzy systems. Fuzzy Sets and Systems, vol. 174 , no. 1, pages 1–30, 2011. »
  Abstract: Many complex physical systems are the interconnection of lower-dimensional subsystems. For such systems, distributed stability analysis and observer design presents several advantages with respect to centralized approaches, such as modularity, easier analysis and design, and reduced computational complexity. Applications include distributed process control, traffic and communication networks, and economic systems. In this paper, we propose sequential stability analysis and observer design for distributed systems where the subsystems are represented by Takagi–Sugeno (TS) fuzzy models. The analysis and design are done sequentially for the subsystems, allowing for the online addition of new subsystems. The conditions are formulated as LMIs and are therefore easy to solve. The approach is illustrated on simulation examples. «
• A. B. Cara, H. Pomares, I. Rojas, Zs. Lendek, R. Babuska, Online Self-Evolving Fuzzy Controller with Global Learning Capabilities. Evolving Systems, vol. 1, pages 225–239, 2010. »
  Abstract: This paper presents an online self-evolving fuzzy controller with global learning capabilities. Starting from very simple or even empty configurations, the controller learns from its own actions while controlling the plant. It applies learning techniques based on the input/output data collected during normal operation to modify online the fuzzy controller's structure and parameters. The controller does not need any information about the differential equations that govern the plant, nor any offline training. It consists of two main blocks: a parameter learning block that learns proper values for the rule consequents applying a local and a global strategy, and a self-evolving block that modifies the controller's structure online. The modification of the topology is based on the analysis of the error surface and the determination of the input variables which are most responsible for the error. Simulation and experimental results are presented to show the controller's capabilities. «
• Zs. Lendek, R. Babuska, B. De Schutter, Stability bounds for fuzzy estimation and control. Journal of Control Engineering and Applied Informatics, vol. 12 , no. 3, pages 3–12, 2010. »
  Abstract: A large class of nonlinear systems can be well approximated by Takagi-Sugeno fuzzy models, for which methods and algorithms have been developed to analyze their stability and to design observers and controllers. However, results obtained for Takagi-Sugeno fuzzy models are in general not directly applicable to the original nonlinear system. In this paper, we investigate what conclusions can be drawn and what guarantees can be expected when an observer or a state feedback controller is designed based on an approximate fuzzy model and applied to the original nonlinear system. We also investigate the case when an observer-based controller is designed for an approximate model and then applied to the original nonlinear system. In particular, we consider that the scheduling vector used in the membership functions of the observer depends on the states that have to be estimated. The results are illustrated using simulation examples. «
• Zs. Lendek, J. Lauber, T. M. Guerra, R. Babuska, B. De Schutter, Adaptive Observers for TS Fuzzy Systems with Unknown Polynomial Inputs. Fuzzy Sets and Systems, vol. 161 , no. 15, pages 2043–2065, 2010. »
  Abstract: A large class of nonlinear systems can be well approximated by Takagi-Sugeno (TS) fuzzy models, with linear or affine consequents. However, in practical applications, the process under consideration may be affected by unknown inputs, such as disturbances, faults or unmodeled dynamics. In this paper, we consider the problem of simultaneously estimating the state and unknown inputs in TS systems. The inputs considered in this paper are (1) polynomials in time (such as a bias in the model or an unknown ramp input acting on the model) and (2) unmodeled dynamics. The proposed observer is designed based on the known part of the fuzzy model. Conditions on the asymptotic convergence of the observer are presented and the design guarantees an ultimate bound on the error signal. The results are illustrated on a simulation example. «
• Zs. Lendek, R. Babuska, B. De Schutter, Stability of Cascaded Fuzzy Systems and Observers. IEEE Transactions on Fuzzy Systems, vol. 17, no. 3, pages 641–653, 2009. »
  Abstract: A large class of nonlinear systems can be well approximated by Takagi-Sugeno (TS) fuzzy models with linear or affine consequents. It is well known that the stability of these consequent models does not ensure the stability of the overall fuzzy system. Therefore, several stability conditions have been developed for TS fuzzy systems. We study a special class of nonlinear dynamic systems that can be decomposed into cascaded subsystems, which are represented as TS fuzzy models. We analyze the stability of the overall TS system based on the stability of the subsystems and prove that the stability of the subsystems implies the stability of the overall system. The main benefit of this approach is that it relaxes the conditions imposed when the system is globally analyzed, thereby solving some of the feasibility problems. Another benefit is that by using this approach, the dimension of the associated linear matrix inequality (LMI) problem can be reduced. For naturally distributed applications, such as multiagent systems, the construction and tuning of a centralized observer may not be feasible. Therefore, we also extend the cascaded approach to the observer design and use fuzzy observers to individually estimate the states of these subsystems. A theoretical proof of stability and simulation examples are presented. The results show that the distributed observer achieves the same performance as the centralized one, while leading to increased modularity, reduced complexity, lower computational costs, and easier tuning. Applications of such cascaded systems include multiagent systems, distributed process control, and hierarchical large-scale systems. «
• Zs. Lendek, R. Babuska, J. Braaksma, C. de Keizer, Decentralized Estimation of Overflow Losses in a Hopper-Dredger. Control Engineering Practice, vol. 16, no. 4, pages 392–406, 2008. »
  Abstract: The Kalman filter and its nonlinear variants have been widely used for filtering and state estimation. However, models with severe nonlinearities are not handled well by Kalman filters. Such a case is presented in this paper: the estimation of the overflow losses in a hopper dredger. The overflow mixture density and flow-rate have to be estimated based on noisy measurements of the total hopper volume, mass, incoming mixture density and flow-rate. In order to reduce complexity and make the tuning easier, a decomposition of the nonlinear process model into two simpler subsystems is proposed. A different type of observer is considered for each subsystem - a particle filter and an unscented Kalman filter. The performance is evaluated for simulated and real-world data and compared with the centralized setting for four combinations of the particle filter and the unscented Kalman filter. The results indicate that the distributed observer achieves the same performance as the centralized one, while leading to increased modularity, reduced complexity, lower computational costs and easier tuning. «
• Zs. Lendek, R. Babuska, B. De Schutter, Distributed Kalman Filtering for Cascaded Systems. Engineering Applications of Artificial Intelligence, vol. 21, no. 3, pages 457–469, 2008. »
  Abstract: The Kalman filter provides an efficient means to estimate the state of a linear process, so that it minimizes the mean of the squared estimation error. However, for naturally distributed applications, the construction and tuning of a centralized observer may present difficulties. Therefore, we propose the decomposition of a linear process model into a cascade of simpler subsystems and the use of a Kalman filter to individually estimate the states of these subsystems. Both a theoretical comparison and simulation examples are presented. The theoretical results show that the distributed observers, except for special cases, do not minimize the overall error covariance, and the distributed observer system is therefore suboptimal. However, in practice, the performance achieved by the cascaded observers is comparable and in certain cases even better than the performance of the centralized observer. A distributed observer system also leads to increased modularity, reduced complexity, and lower computational costs. «

Contributions to books

• V. Estrada-Manzo, Zs. Lendek, T. M. Guerra, Observer Design for Robotic Systems via Takagi-Sugeno Models and Linear Matrix Inequalities. In Handling uncertainty and networked structure in robot control, series Studies in Systems, Decision and Control, L. Busoniu and L. Tamas, Editors, pages 103-128. Springer International Publishing, 2015.
• Zs. Lendek, P. Raica, J. Lauber, T. M. Guerra, Observer Design for Discrete-Time Switching Nonlinear Models. In Hybrid Dynamical Systems, series Lecture Notes in Control and Information Sciences, M. Djemai, M. Defoort, Editors, vol. 457, pages 27-58. Springer International Publishing, 2015.

Conference papers

• V.-M. Maer, S. Pirje, Zs. Lendek, D. Tolic, A. Duras, V. Prkacin, I. Palunko, L. Busoniu, Two-Channel Extended Kalman Filtering with Intermittent Measurements. In 2024 American Control Conference, pages 1202-1209, Toronto, Canada, July 2024. »
  Abstract: We consider two nonlinear state estimation problems in a setting where an extended Kalman filter receives measurements from two sets of sensors via two channels (2C). In the stochastic-2C problem, the channels drop measurements stochastically, whereas in 2C scheduling, the estimator chooses when to read each channel. In the first problem, we generalize linear-case 2C analysis to obtain – for a given pair of channel arrival rates – boundedness conditions for the trace of the error covariance, as well as a worst-case upper bound. For scheduling, an optimization problem is solved to find arrival rates that balance low channel usage with low trace bounds, and channels are read deterministically with the expected periods corresponding to these arrival rates. We validate both solutions in simulations for linear and nonlinear dynamics; as well as in a real experiment with an underwater robot whose position is being intermittently found in a UAV camera image. «
• A. Codrean, A. Kovacs, O. Stefan, Zs. Lendek, Networked control of a Parrot Mambo drone. In ISIE 2024 - 33rd International Symposium on Industrial Electronics, pages 1-7, Ulsan, South Korea, June 2024. »
  Abstract: The current study proposes a network control structure for small low-cost drones like the Parrot Mambo mini-drone. The structure is composed of an inner loop running on the drone, and an outer loop running on a remote computer. The inner loop controls the attitude and altitude of the drone based on Kalman filter estimations from the onboard sensors. The outer loop ensures position tracking based on measurements from OptiTrack cameras. A time delay compensator is added to address the constraints imposed by wireless network communications between the drone and the remote computer. Experimental results using Parrot Mambo drones show good stability and tracking performances, despite model uncertainty and time delay. «
• S.-D. Sim, A. Medgyesi, Zs. Lendek, C.-L. Vaida, V. Mihaly, M. Susca, P. Dobra, J. Machado, Robotic platform for position control of a ball. Accepted 33th International Conference onRobotics in Alpe-Adria-Danube Region, pages 503-509, Cluj-Napoca, Romania, June 2024. »
  Abstract: The present paper proposes and describes an approach to stabilizing a ball on a rectangular surface using a three-armed robotic system. The system is based on advanced image detection for accurate ball and surface identification. The hardware includes three servo motors controlled by an Arduino board, and the camera used is a mobile phone connected to the computer. The control of the arm movements is achieved by a PD controller. The components were print-ed with a 3D printer. The technical details of the system, as well as the PD con-troller are presented in detail, highlighting the effective interaction between the theoretical and practical sides. The development of this system offers an inter-disciplinary perspective, combining knowledge from mechatronics, machine vi-sion, and robotic control. «
• S.-D. Sim, A. Medgyesi, Zs. Lendek, M. Susca, V. Mihaly, D. Pisla, C.-L. Vaida, P. Dobra, A.-E. Pica, Adaptive filters for DC motor identification: a case study. In 2024 IEEE International Conference on Automation, Quality and Testing, Robotics, pages 1-6, Cluj-Napoca, Romania, May 2024. »
  Abstract: This paper investigates the practical application and evaluation of four adaptive algorithms: Least Mean Square (LMS), Normalized Least Mean Square (NLMS), Recursive Least Square (RLS) and Affine Projection (AP) for the identification of a DC motor. The work focuses on dynamic system identification, where the adaptability and efficiency of numerical filters play an important role. To identify the parameters of a DC motor, these adaptive algorithms are used on measured data. With the aim of having a shorter processing time, the data was downsampled. Satisfactory results were obtained with all algorithms. Finally, the difficulty of implementing the algorithms, the errors obtained and the processing time were analyzed. «
• B. Lazar, Zs. Lendek, Sliding mode observer based fuzzy control for TS systems. In 2023 IEEE Symposium Series on Computational Intelligence, pages 1257-1262, Mexico City, Mexico, December 2023. »
  Abstract: This paper presents a sliding mode observer based fuzzy control. The sliding mode observer is developed for a linear dominant system, but taking into account the model mismatch. After that a fuzzy state feedback controller is designed. To ensure the stability of the closed loop system in the presence of uncertainties, Lyapunov synthesis is used. The results are illustrated on a numerical example. Simulations on the nonlinear system are presented to demonstrate the effectiveness of the observer based control. «
• S.-D. Sim, Zs. Lendek, P. Dobra, Analysis of the quantization effects in the implementation of numerical filters. In 2023 26th International Conference on System Theory, Control and Computing (ICSTCC), pages 227-232, Timisoara, Romania, October 2023. »
  Abstract: The paper analyzes the efficiency of fixed-point implementation and the effect of quantization of coefficients and signals in the implementation of numerical filters on the STM32 Nucleo-64P development board. Discretization methods are also analyzed. By modelling the effects of quantization, it is possible to indicate how the system responds. Proper quantization can increase the performance. We model the quantization error as stochastic noise. The results show that the quantization of the coefficients and the fixed-point processing minimally change the response of the digital filter compared to the analog one, thus achieving very good results at high sampling frequencies. Also, through this analysis, the most efficient implementation can be chosen, taking into account the system and the characteristics of the development board. «
• B. Yousuf, Zs. Lendek, L. Busoniu, Multi-Agent Exploration-Based Search for an Unknown Number of Targets. In Preprints of the 22nd IFAC World Congress, pages 5999-6004, Yokohama, Japan, July 2023. »
  Abstract: This paper presents an active sensor fusion technique for multiple mobile agents (robots) to detect an unknown number of static targets at unknown positions. To process and fuse sensor measurements from the agents, we use a random finite set formulation with an iterated-corrector probability hypothesis density filter. Our main contribution is to introduce two different multi-agent planners to quickly find the targets. The planners make greedy decisions for the next state of each agent by maximizing an objective function consisting of target refinement and exploration components. We demonstrate the performance of our approach through a series of simulations using homogeneous and heterogeneous agents. The results show that our framework works better than a lawnmower baseline, and that a centralized version of the planner works best. «
• B. Suto, A. Codrean, Zs. Lendek, Optimal control of multiple drones for obstacle avoidance. In Preprints of the 22nd IFAC World Congress, pages 5980-5986, Yokohama, Japan, July 2023. »
  Abstract: The control and path planning of multiple drones in a 3D space with obstacle avoidance is a complex challenge, subject to ongoing research. In this paper we propose an optimal control approach, with a baseline controller and filter running on the drones, and a prediction based optimization algorithm running remotely, as a supervisory controller. The supervisor is responsible for calculating the minimal deviation from the trajectory given by the baseline controllers, such that the obstacle is avoided. The approach is tested in simulations with nonlinear drone models in a realistic setting with noise and transmission delays. «
• B. Lazar, Zs. Lendek, Observer based guaranteed cost control for time-delay TS fuzzy systems. In 2022 26th International Conference on System Theory, Control and Computing (ICSTCC), pages 117-122, Sinaia, Romania, October 2022. »
  Abstract: This paper considers the design of observer based guaranteed cost control of time-delay nonlinear systems represented by TS fuzzy models. We consider that both the states and the inputs are affected by time varying delay, which is assumed to be known. We propose conditions for observer and controller design with the aim that the closed-loop is asymptotically stable and the cost is minimized. The conditions are bilinear and we solve them in two steps. We also give different possibilities for minimizing the cost function along with a performance comparison between them. The results are validated on a numerical example. «
• B. Suto, Zs. Lendek, Switching control of a rotary inverted pendulum. In 2022 26th International Conference on System Theory, Control and Computing (ICSTCC), pages 111-116, Sinaia, Romania, October 2022. »
  Abstract: In this paper we consider the problem of swinging-up and stabilization of a rotary inverted pendulum. We design switching controllers and analyse whether the performance can be improved using more controllers. We optimize both the control gains and the switching points. All the controllers are tested experimentally on a rotary inverted pendulum. Our results indicate that having a large number of switching controllers does not necessarily lead to a performance increase. «
• B. Yousuf, Zs. Lendek, L. Busoniu, Exploration-based search for an unknown number of targets using a UAV. In 6th IFAC International Conference on Intelligent Control and Automation Sciences, pages 1-6, Cluj-Napoca, Romania, July 2022. »
  Abstract: We consider a scenario in which a UAV must locate an unknown number of targets at unknown locations in a 2D environment. A random finite set formulation with a particle filter is used to estimate the target locations from noisy measurements that may miss targets. A novel planning algorithm selects a next UAV state that maximizes an objective function consisting of two components: target refinement and an exploration. Found targets are saved and then disregarded from measurements to focus on refining poorly seen targets. The desired next state is used as a reference point for a nonlinear tracking controller for the robot. Simulation results show that the method works better than lawnmower and mutual-information baselines. «
• S.-D. Sim, Zs. Lendek, P. Dobra, Implementation and Testing of Digital Filters on STM32 Nucleo-64P. In IEEE International Conference on Automation, Quality and Testing, Robotics, AQTR, pages 1-6, Cluj-Napoca, Romania, May 2022. »
  Abstract: This paper aims to present two ways to design and implement numerical filters. The first is the classic or hand-coded method, which involves the implementation of a computational algorithm in C, while the second is automatically generated code. Both FIR and IIR filters are implemented and based on the results obtained, the differences between them discussed. We highlight the advantages and disadvantages of each method of implementation and the costs in terms of design time, memory, performance. Both mplementation variants present satisfactory results and meet the equired requirements, the choice of one of them depends on the pplication used and the programming experience «
• Zs. Lendek, Observer design using Takagi-Sugeno fuzzy models. In Rencontres francophones sur la logique floue et ses applications, pages 12-18, Paris, France, October 2021. »
  Abstract: We will start with an introduction to TS models and their use for state estimation. Next, some of the main research problems that have been addressed in observer design in the last decades will be reviewed. Afterwards, recent results that take TS models closer to general nonlinear systems will be presented. Finally, the advantages and shortcomings of fuzzy models for estimation will be discussed. «
• A. Matyas, Zs. Lendek, Observer design for a class of nonlinear systems with nonscalar-input nonlinear consequents. In 4th IFAC Conference on Embedded Systems, Computational Intelligence and Telematics in Control (CESCIT), pages 62-67, Valenciennes, France, July 2021. »
  Abstract: In this paper we consider an observer design method for time-delay Takagi-Sugeno fuzzy models with nonlinear consequents. We assume that both the input and the membership functions are a ected by the known delay. The nonlinearities in the consequents are handled by a slope-bounded condition. The observer design conditions are formulated as linear matrix inequalities. A numerical example illustrates the results. «
• Z. Nagy, Zs. Lendek, L. Busoniu, Observer design for a class of nonlinear systems with nonscalar-input nonlinear consequents. Accepted 2020 59th IEEE Conference on Decision and Control, pages 1-6, Jeju, Republic of Korea, December 2020. Joint L-CSS - CDC submission.
• A. Matyas, Z. Nagy, Zs. Lendek, Controller design for time-delay TS fuzzy systems with nonlinear consequents. In 2020 IEEE World Congress on Computational Intelligence, IEEE International Conference on Fuzzy Systems, pages 1-6, Glasgow, UK, July 2020. »
  Abstract: This paper proposes a controller design method for time-delay Takagi-Sugeno fuzzy models with nonlinear consequents. We assume that both the input and the membership functions are affected by the delay. The nonlinearities in the consequents are handled by a slope-bounded condition. The controller design conditions are formulated as linear matrix inequalities. A numerical example illustrates the results. «
• Z. Nagy, A. Matyas, Zs. Lendek, Stabilization of TS fuzzy systems with time-delay and nonlinear consequents. In 2020 IFAC World Congress, pages 1-6, Berlin, Germany, July 2020. »
  Abstract: This paper proposes a controller design method for Takagi-Sugeno fuzzy systems with nonlinear consequents when the input is affected by time-delay. We consider that the membership functions may depend on both current and delayed states. To handle the nonlinear consequents a slope bounded condition is used. The design conditions are formulated in terms of linear matrix inequalities. A numerical example illustrates the obtained results. «
• Z. Nagy, Zs. Lendek, L. Busoniu, Control and estimation for mobile sensor-target problems with distance-dependent noise. In Proceedings of the 2020 American Control Conference, pages 2574-2579, Denver, Colorado, USA, July 2020. »
  Abstract: This paper investigates the scenario where a mobile sensor must observe (i.e., estimate the state of) another system, called the target. The estimation is affected by a distance-dependent noise, and for this reason we propose to control the sensor so that the effect of the noise is minimized. We propose a novel approach in which the controller and the observer are designed in tandem, with the common objective of obtaining a better estimation. We give sufficient design conditions for a general class of nonlinear systems satisfying a Lipschitz-like condition on the nonlinearity. A numerical example illustrates the obtained results. Supplementary material «
• Z. Nagy, Zs. Lendek, Observer design for discrete-time TS fuzzy systems with local nonlinearities. In Proceedings of the 2020 European Control Conference, pages 1-6, Saint Petersburg, Russia, May 2020. »
  Abstract: This paper presents a novel observer design approach for discrete-time nonlinear systems. The nonlinearities are handled on the one hand by a polytopic model and on the other hand with a slope-restricted condition. Using these two tools sufficient LMI conditions are developed for a new observer design technique. The obtained results are tested in simulation and on experimental data on an inverted pendulum on a cart. «
• O. Boncalo, A. Amaricai, Zs. Lendek, Configurable hardware accelerator architecture for Takagi-Sugeno fuzzy controller. In Proceedings of the 2019 Euromicro Conference on Digital System Design, pages 96-101, Chalkidiki, Greece, August 2019. »
  Abstract: In this paper, we present a parametric hardware accelerator for Takagi-Sugeno fuzzy controllers. The architecture consists of an application specific weighting function computation block, generic control output computation unit, and a programmable register file based interface. The proposed hardware design methodology is applied to a two degree of freedom robot arm controller. FPGA implementation results indicate that the hardware TS fuzzy controller supports throughputs up to 1.5 Msamples/sec, with maximum working frequencies of around 150 MHz. «
• Z. Nagy, Zs. Lendek, Observer-based controller design for Takagi-Sugeno fuzzy systems with local nonlinearities. In Proceedings of the 2019 IEEE International Conference on Fuzzy Systems, pages 1-6, New Orleans, USA, June 2019. »
  Abstract: This paper presents an observer-based controller design approach. To handle the inherent nonlinearities Takagi-Sugeno fuzzy modelling is used with nonlinear consequents. The purpose of using local nonlinear models is to reduce the number of fuzzy rules as well as to handle nonlinearities depending on unmeasured states. The design conditions are defined in form of Linear Matrix Inequalities, which can be efficiently solved. The obtained conditions are tested in simulation on an inverted pendulum model. «
• T. Laurain, Zs. Lendek, J. Lauber, R. M. Palhares, Transforming variable transport delays into fixed ones: An application to a conveyor belt problem . In Proceedings of the 2018 Annual American Control Conference (ACC) , pages 3969-3974, Milwaukee, WI, USA , June 2018. »
  Abstract: This paper presents a systematic methodology to deal with variable transport delays by constructing a new discrete domain where the delay becomes fixed (a difference of samples). The Euler transformation is used to change from the continuous-time domain to this special discrete domain depending on the same variable as the transport delay. After this transformation, the model becomes nonlinear and the Takagi- Sugeno fuzzy representation is used to handle the nonlinearities. To highlight and illustrate the efficiency of the proposed methodology, an LMI based controller design is used to control a conveyor belt with variable transport delay.s «
• T. Laurain, J. Lauber, Zs. Lendek, R. M. Palhares, Air-fuel ratio fuzzy controller handling delay: Comparison with a PI/Smith . In Proceedings of the 2018 IEEE International Conference on Automation, Quality and Testing, Robotics (AQTR) , pages 1-6, Cluj-Napoca, Romania, May 2018. »
  Abstract: This paper is dedicated to the control of the air-fuel ratio in a gasoline engine. The use of the crank-angle domain handles the variable transport delay, which is the main challenge when controlling air-fuel ratio. The Takagi-Sugeno methodology is considered to deal with the nonlinearities in the model. The control law is obtained using an extended state that includes the delayed variables. Simulations confirm the feasibility of the method and highlight the efficiency of the proposed air-fuel ratio controller. «
• Z. Nagy, Zs. Lendek, L. Nagy, Robot arm control with optimal PID (in Hungarian). In 18th International Conference on Energetics-Electrical Engineering, 27th International Conference on Computers and Education,, pages 88-93, Oradea, Romania, October 2017. »
  Abstract: In this paper we compute an optimal PID controller for a robot arm to track a predefined trajectory. The model of the robot arm incorporates all the physical elements, like gravity and friction. Based on this model, we develop a PID controller. Using the parameters of the PID, further optimization is done to produce better results for trajectory tracking. We test both the original and the optimized controller in simulation and in real-time experiments. «
• T. Laurain, Zs. Lendek, J. Lauber, R. M. Palhares, Transformer les retards de transport variables en retards fixes: Une application au probleme du convoyeur (in French). In Proceedings of the 2017 Rencontre sur la Logique Floue et ses Applications, pages 1-8, Amiens, France, October 2017. »
  Abstract: This paper presents a systematic methodology to deal with variable transport delays by constructing a new discrete domain where the variable transport delay becomes fixed (a difference of samples). The Euler transformation is used to change from the continuous-time domain to this special discrete domain depending on the same variable as the transport delay. After this transformation, the model becomes nonlinear and the Takagi-Sugeno fuzzy representation is obtained to handle the nonlinearities. To highlight and illustrate the efficiency of the proposed methodology, a LMI based controller design is developed to control a conveyor belt with variable transport delay. «
• T. Laurain, Zs. Lendek, J. Lauber, R. M. Palhares, A new air-fuel ratio model fixing the transport delay: validation and control. In Proceedings of the 2017 IEEE Conference on Control Technology and Applications, pages 1904-1909, Hawaii, USA, August 2017. »
  Abstract: Air-fuel ratio control is a crucial problem for engine control since it is one of the most important issues related to pollution reduction. The main difficulty in air-fuel ratio control is the time-varying delay. We propose a new model that includes the delay. This model is identified using real dataset from an engine test bench. The time-varying delay is made constant by using a change of domain. The nonlinearities of the model are handled with the Takagi-Sugeno representation and a linear controller is designed using the Lyapunov direct method. Simulation results highlight the efficiency of the proposed approach compared to classic maps-based controllers. «
• Z. Nagy, E. Pall, Zs. Lendek, Unknown input observer for a robot arm using TS fuzzy descriptor models. In Proceedings of the 2017 IEEE Conference on Control Technology and Applications, pages 939-944, Hawaii, USA, August 2017. »
  Abstract: This paper presents an unknown input observer for a two-link robot arm. To handle the inherent nonlinearities, a Takagi-Sugeno fuzzy model in descriptor form is used. The design conditions are given as linear matrix inequalities, which can be efficiently solved. The observer is tested both in simulation and on experimental, measured data. «
• B. Marx, Zs. Lendek, Local observer design for discrete-time TS systems. In Preprints of the 2017 IFAC World Congress, pages 873-878, Toulouse, France, July 2017. »
  Abstract: In this paper, the problem of local observer design for discrete-time Takagi-Sugeno fuzzy systems is addressed. The observers being designed are local in the sense that relaxed asymptotic convergence conditions are sought locally, rather than globally, while also determining the region where the conditions are valid. The design conditions are derived using both quadratic and non-quadratic Lyapunov functions. The obtained results are expressed in terms of linear matrix inequalities and they are illustrated on a numerical example. «
• S. Beyhan, F. Sarabi, Zs. Lendek, R. Babuska, Takagi-Sugeno fuzzy payload estimation and adaptive control. In Preprints of the 2017 IFAC World Congress, pages 867-872, Toulouse, France, July 2017. »
  Abstract: In this paper, a novel adaptive Takagi-Sugeno (TS) fuzzy observer-based controller is proposed. The closed-loop stability and the boundedness of all the signals are proven by Lyapunov stability analysis. The proposed controller is applied to a flexible-transmission experimental setup. The performance for constant payload in the presence of noisy measurements is compared to a controller based on a classical extended Luenberger observer. Simulation and real-time results show that the proposed observer-based feedback controller provides accurate position tracking under constant and varying payloads. «
• Z. Nagy, Zs. Lendek, Quadcopter modeling and control. In Proceedings of the Journees Francophones sur la Planification, la Decision et l'Apprentissage pour la conduite de systemes, pages 1-2, Caen, France, July 2017.
• N. Zoltan, Zs. Lendek, Takagi Sugeno fuzzy modelling and control of a robot arm. In Proceedings of the 17th International Conference on Energetics-Electrical Engineering, 26th International Conference on Computers and Education, pages 265-270, Cluj-Napoca, Romania, October 2016. »
  Abstract: The first step to control a robot arm is to define the mathematical model, which describes the motion of the arm depending on the input. In this paper we model and control an existing robot arm. The model incorporates all the physical elements, like gravity and friction. Based on this model, we develop a Takagi-Sugeno fuzzy controller. In the following we will present the steps for obtaining the model, and the results provided by the controller. «
• Zs. Lendek, J. Lauber, Local quadratic and nonquadratic stabilization of discrete-time TS fuzzy systems. In Proceedings of the 2016 IEEE World Congress on Computational Intelligence, pages 2182-2187, Vancouver, Canada, July 2016. »
  Abstract: This paper proposes conditions for the local stabilization of discrete-time Takagi-Sugeno fuzzy systems, for which all existing conditions consider only global stabilization. The conditions are developed first considering a quadratic Lyapunov function and are then extended for non-quadratic Lyapunov functions. An estimate of the region of attraction is also obtained. The conditions are illustrated and discussed on a numerical example. «
• Zs. Lendek, J. Lauber, Local stability of discrete-time TS fuzzy systems. In Proceedings of the 4th IFAC International Conference on Intelligent Control and Automation Sciences , pages 7-12, Reims, France, June 2016. »
  Abstract: This paper considers local stability analysis of discrete-time Takagi-Sugeno fuzzy systems, for which classically in the TS literature only global stability is considered. Using a common quadratic and nonquadratic Lyapunov function, respectively, LMI conditions are developed to establish local stability of an equilibrium point. An estimate of the region of attraction of this point is also determined. The developed conditions are illustrated on a numerical example. «
• N. Hodasz, V. Bradila, I. Nascu, Zs. Lendek, Modeling and parameter estimation for an activated sludge wastewater treatment process. In Proceedings of the 2016 IEEE International Conference on Automation, Quality and Testing, Robotics, pages 1-6, Cluj-Napoca, Romania, May 2016. »
  Abstract: Wastewater is treated in wastewater treatment plants (WWTP) through various physical, biological and chemical methods. A good control of WWTP processes could lead to better water quality and to an efficient use of energy. In order to control the treatment process all parameters need to be known. Some of them cannot be measured, so an estimate of the unknown parameters has to be used. This paper proposes the development of a linear model which will be used in future research for dynamic control design. To estimate the unknown parameters, a Luenberger observer and a Kalman filter are implemented. «
• V. Estrada-Manzo, Zs. Lendek, T. M. Guerra, Unknown input estimation for nonlinear descriptor systems via LMIs and Takagi-Sugeno models. In Proceedings of the 54th IEEE Conference on Decision and Control, pages 1-6, Osaka, Japan, December 2015. »
  Abstract: This paper presents an unknown inputs observer for nonlinear descriptor systems. The approach uses the Takagi-Sugeno representation of the nonlinear model. In order to obtain strict linear matrix inequalities a novel observer structure is given. Thus the conditions can be efficiently solved via convex optimization techniques. A numerical example is provided to illustrate the performance of the proposed approach. «
• V. Estrada-Manzo, T. M. Guerra, Zs. Lendek, Static output feedback control for continuous-time TS descriptor models: decoupling the Lyapunov function. In Proceedings of the 2015 IEEE International Conference on Fuzzy Systems, pages 1-6, Istanbul, Turkey, August 2015. »
  Abstract: The paper deals with static output feedback controller design for continuous-time Takagi-Sugeno descriptor models. Via the well-known Finsler’s Lemma and the descriptor-redundancy approach a set of linear matrix inequalities are derived to solve this design problem. A numerical example shows the effectiveness of the proposed approaches. «
• V. Estrada-Manzo, Zs. Lendek, T. M. Guerra, Improving the observer design for discrete-time TS descriptor models under the quadratic framework. In Proceedings of the IFAC Conference on Embedded Systems, Computational Intelligence and Telematics in Control, pages 276-281, Maribor, Slovenia, June 2015. »
  Abstract: The paper presents a new quadratic Lyapunov function for observer design for discrete-time nonlinear descriptor systems. The main idea is to represent the original nonlinear model as a Takagi-Sugeno one and then use Lyapunov’s direct method to design the observer. The well-known Finsler’s Lemma is used to design a non-Parallel-Distributed-Compensator-like observer together with a quadratic Lyapunov function. This procedure yields design conditions in terms of linear matrix inequalities. The effectiveness of the proposed approaches is illustrated via numerical examples. «
• V. Estrada-Manzo, Zs. Lendek, T. M. Guerra, Output feedback control for T-S discrete-time nonlinear descriptor models. In Proceedings of the 53rd IEEE Conference on Decision and Control, pages 860-865, Los Angeles, CA, USA, December 2014. »
  Abstract: This paper presents a static output feedback controller design for discrete-time nonlinear descriptor models. The conditions are given in terms of linear matrix inequalities (LMIs). The approach is based on the Takagi-Sugeno (T-S) representation of the nonlinear system and Finsler’s Lemma. The proposed method exploits the discrete-time nature of the T-S model by the use of delayed Lyapunov functions which provide more degrees of freedom without increasing the number of LMIs. It is also extended for robust control. The benefits of the proposed approaches are illustrated via numerical examples. «
• V. Estrada-Manzo, Zs. Lendek, T. M. Guerra, Hinf control for discrete-time Takagi-Sugeno descriptor models: a delayed approach. In Proceedings of the 23e Rencontres Francophones sur la Logique Floue et ses Applications, pages 1-6, Ajaccio, France, October 2014. »
  Abstract: This paper provides conditions for Hinf control of discrete-time nonlinear descriptor models. The nonlinear model is represented by a Takagi-Sugeno one. Conditions are given in terms of linear matrix inequalities. Relaxed conditions are obtained via delayed Lyapunov functions and delayed control laws. Such an approach allows adding extra decision variables without increasing the number of LMI conditions. The benefits of the proposed approach are verified via a numerical example. «
• Zs. Lendek, P. Raica, J. Lauber, T. M. Guerra, Nonquadratic stabilization of switching TS systems. In Preprints of the 2014 IFAC World Congress, pages 7970-7975, Cape Town, South Africa, August 2014. »
  Abstract: In this paper we consider stabilization of switching nonlinear systems represented by TS models. To develop the conditions we use two di®erent switching Lyapunov functions. For each Lyapunov function a set of conditions is developed. The conditions are formulated as LMIs and relaxed using delays in the controller and the Lyapunov function. The application of the conditions is illustrated on numerical examples. «
• V. Estrada-Manzo, Zs. Lendek, T. M. Guerra, Discrete-time Takagi-Sugeno descriptor models: observer design. In Preprints of the 2014 IFAC World Congress, pages 7965-7969, Cape Town, South Africa, August 2014. »
  Abstract: The present paper deals with observer design for discrete-time nonlinear descriptor systems. Through Finsler’s Lemma, we cut the link between the observer gains and the Lyapunov function, which relaxes existing conditions and introduces an extra degree of freedom. In addition, the results are expressed as LMI constraints. The effectiveness of the two proposed approaches is illustrated via several examples. «
• V. Estrada-Manzo, T. M. Guerra, Zs. Lendek, Discrete-time Takagi-Sugeno descriptor models: controller design. In Proceedings of the 2014 IEEE World Congress on Computational Intelligence, IEEE International Conference on Fuzzy Systems, pages 1-5, Beijing, China, July 2014. »
  Abstract: Many physical systems are naturally represented by descriptor models. This paper is concerned with stabilization of discrete-time descriptor systems represented by Takagi-Sugeno fuzzy models. Two different approaches are presented based on non-quadratic Lyapunov functions. The results are expressed in terms of linear matrix inequalities. Numerical examples validate the proposed methods. «
• Zs. Lendek, P. Raica, J. Lauber, T. M. Guerra, Observer design for switching nonlinear systems. In Proceedings of the 2014 IEEE World Congress on Computational Intelligence, IEEE International Conference on Fuzzy Systems, pages 1-6, Beijing, China, July 2014. »
  Abstract: In this paper we consider observer design for discrete-time switching systems represented by Takagi-Sugeno fuzzy models. For the design we use a switching Lyapunov function defined on the switches. In order to develop stability conditions for the estimation error dynamics, we consider the variation of this function along possible switches. The conservativeness of the approach is reduced by considering the alpha-sample variation of the Lyapunov function. This approach can bring solutions to observer design for some switching systems with unobservable and unstable local models. The developed conditions are illustrated on a numerical example. «
• V. Estrada-Manzo, T. M. Guerra, Zs. Lendek, An LMI approach for observer design for Takagi-Sugeno descriptor models. In Proceedings of the 2014 IEEE International Conference on Automation, Quality and Testing, Robotics, pages 1-6, Cluj-Napoca, Romania, May 2014. »
  Abstract: This work presents a novel observer design for nonlinear descriptor systems using their Takagi-Sugeno representation. The approach allows obtaining more relaxed results than previous literature by changing the extended estimated state vector; this step permits using a full observer gain. The obtained conditions are pure LMI. Moreover, previous results are always included by the new ones. An example illustrates the benefits of the proposed method. «
• P. Petrehus, Zs. Lendek, P. Raica, Fuzzy modeling and control of a 3D crane. In Proceedings of the 2013 IFAC International Conference on Intelligent Control and Automation Science, pages 201-206, Chengdu, China, September 2013. »
  Abstract: Cranes are used to move heavy cargo. While they are in general controlled by a human operator, automated systems are able to obtain more precise control. In this paper, we design a Takagi-Sugeno (TS) fuzzy controller for the crane. For this, first a TS fuzzy model of the crane is developed, and a TS observer is used to estimate the unmeasurable states. The observer is tested in simulation and on a laboratory-scale 3D crane, while the controller is tested in simulation. «
• Zs. Lendek, J. Lauber, T. M. Guerra, P. Raica, Stability analysis of switching TS models using alpha-samples approach. In Proceedings of the 2013 IFAC International Conference on Intelligent Control and Automation Science, pages 207-211, Chengdu, China, September 2013. »
  Abstract: In this paper we consider stability analysis of discrete-time switching systems represented by Takagi-Sugeno fuzzy models. For the analysis we use a switching Lyapunov function defined on the switches. In order to develop stability conditions, we consider the variation of this function along switching paths of length alpha, i.e., an alpha sample variation of the Lyapunov function. This approach is able to determine stability of a switching system containing unstable local models. The developed conditions can be formulated as LMIs and they are illustrated on a numerical example. «
• Zs. Lendek, J. Lauber, T. M. Guerra, P. Raica, On stabilization of discrete-time periodic TS systems. In Proceedings of the 2013 IEEE International Conference on Fuzzy Systems, pages 1-7, Hyderabad, India, July 2013. »
  Abstract: In this paper we consider controller design for periodic Takagi-Sugeno fuzzy models. For this, we use a periodic nonquadratic Lyapunov function defined at the time instants when the subsystems switch. Using the proposed conditions we are able to handle periodic Takagi-Sugeno systems where the local models or even the subsystems are unstable or cannot be stabilized. The application of the conditions is illustrated on numerical examples. «
• V. Estrada-Manzo, T. M. Guerra, Zs. Lendek, M. Bernal, Improvements on non-quadratic stabilization of continuous-time Takagi-Sugeno descriptor models. In Proceedings of the 2013 IEEE International Conference on Fuzzy Systems, pages 1-6, Hyderabad, India, July 2013. »
  Abstract: This paper presents a relaxed approach for stabilization and H-infinity disturbance rejection of continuous-time Takagi-Sugeno models in descriptor form. Based on Finsler's Lemma, the control law can be conveniently decoupled from a non-quadratic Lyapunov function. These developments include and outperform previous results on the same subject while preserving the advantage of being expressed as linear matrix inequalities. Two examples are presented to illustrate the improvements. «
• S. Beyhan, Zs. Lendek, M. Alci, R. Babuska, Takagi-Sugeno Fuzzy Observer and Extended Kalman Filter for Adaptive Payload Estimation. In Asian Control Conference, pages 1-6, Istanbul, Turkey, June 2013. »
  Abstract: In this paper, two nonlinear state estimation methods, Takagi-Sugeno fuzzy observer and extended-Kalman filter are compared in terms of their ability to reliably estimate the velocity and an unknown, variable payload of a nonlinear servo system. Using the system dynamics and a position measurement, the velocity and unknown payload are estimated. In a simulation study, the servo system is excited with a randomly generated step input. In real-time experiments, the estimation is performed under feedback-linearizing control. The performance of the TS fuzzy payload estimator is discussed with respect to the choice of the desired convergence rate. The application results show that the Takagi-Sugeno fuzzy observer provides better performance than the extended-Kalman filter with robust and less parameter dependent structure. «
• Zs. Lendek, T.M. Guerra, J. Lauber, Construction of extended Lyapunov functions and control laws for discrete-time TS systems. In Proceedings of the 2012 IEEE World Congress on Computational Intelligence, IEEE International Conference on Fuzzy Systems, pages 286-291, Brisbane, Australia, June 2012.
• S. Bindiganavile Nagesh, Zs. Lendek, A.~A. Khalate, R. Babuska, Adaptive fuzzy observer and robust controller for a 2-DOF robot arm. In Proceedings of the 2012 IEEE World Congress on Computational Intelligence, IEEE International Conference on Fuzzy Systems, pages 149-155, Brisbane, Australia, June 2012.
• P. Petrehus, Zs. Lendek, Fuzzy modeling and control of HIV infection. In Student forum - 2012 IEEE International Conference on Automation, Quality and Testing, Robotics, pages 1-6, Cluj, Romania, May 2012.
• Zs. Lendek, J. Lauber, T.M. Guerra, Switching fuzzy observers for periodic TS systems. In Proceedings of the 2012 IEEE International Conference on Automation, Quality and Testing, Robotics, pages 1-6, Cluj, Romania, May 2012.
• Zs. Lendek, J. Lauber, T.M. Guerra, Switching Lyapunov functions for periodic TS systems. In Proceedings of the 1st IFAC Conference on Embedded Systems, Computational Intelligence and Telematics in Control, pages 1-6, Wurzburg, Germany, April 2012.
• Zs. Lendek, A. Berna, J. Guzman-Gimenez, A. Sala, P. Garcia., Application of Takagi-Sugeno observers for state estimation in a quadrotor. In Proceedings of the 50th IEEE Conference on Decision and Control and European Control Conference, pages 7530-7535, Orlando, Florida, December 2011.
• S. Beyhan, Zs. Lendek, R. Babuska, M. Wisse, M. Alci, Control of a Robot Manipulator with Varying Payload Mass. In Proceedings of the 50th IEEE Conference on Decision and Control and European Control Conference, pages 8291-8296, Orlando, Florida, December 2011.
• Zs. Lendek, R. Babuska, and B. De Schutter, Stability analysis and observer design for string-connected TS systems. In Preprints of the IFAC World Congress, pages 12795-12800, Milano, Italy, September 2011.
• P. Stano, Zs. Lendek, R. Babuska, Saturated particle filter. In Proceedings of the 2011 American Control Conference, pages 1819–1824, San Francisco, California, June 2011.
• Z. Hidayat, Zs. Lendek, R. Babuska, B. De Schutter, Fuzzy observer for state estimation of the METANET traffic model. In Proceedings of the 13th International IEEE Conference on Intelligent Transportation Systems, pages 19-24, Madeira, Portugal, September 2010.
• P. Stano, Zs. Lendek, R. Babuska, J. Braaksma and C. de Keizer, Particle Filters for the Estimation of the Average Grain Diameter of the Material Excavated by a Hopper Dredger. In Proceedings of the 2010 IEEE Multi-Conference on Systems and Control , pages 292-297, Yokohama, Japan, September 2010.
• A. B. Cara, Zs. Lendek, R. Babuska, H. Pomares and I. Rojas, Online Self-organizing Adaptive Fuzzy Controller: Application to a Nonlinear Servo System. In Proceedings of the 2010 IEEE World Congress on Computational Intelligence, pages 2491-2498, Barcelona, Spain, July 2010.
• Zs. Lendek, T. M. Guerra, R. Babuska, On non-PDC Local Observers for TS Fuzzy Systems. In Proceedings of the 2010 IEEE World Congress on Computational Intelligence, pages 2436-2442, Barcelona, Spain, July 2010.
• Zs. Lendek, R. Babuska, B. De Schutter, Fuzzy Models and Observers for Freeway Traffic State Tracking. In Proceedings of the 2010 American Control Conference, pages 2278-2283, Baltimore, US, June 2010.
• Zs. Lendek, R. Babuska, B. De Schutter, Stability bounds for fuzzy estimation and control --- Part II: Output-feedback control. In Proceedings of the 2010 IEEE International Conference on Automation, Quality and Testing, Robotics, pages 1-6, Cluj-Napoca, Romania, May 2010. »
  Abstract: A large class of nonlinear systems can be well approximated by Takagi-Sugeno fuzzy models, for which methods and algorithms have been developed to analyze their stability and to design observers and controllers. However, results obtained for Takagi-Sugeno fuzzy models are in general not directly applicable to the original nonlinear system. In this paper, we investigate what conclusions can be drawn when an observer-based controller is designed for an approximate model and then applied to the original nonlinear system. In particular, we consider the case when the scheduling vector used in the membership functions of the observer depends on the states that have to be estimated. The results are illustrated using simulation examples. «
• Zs. Lendek, R. Babuska, B. De Schutter, Stability bounds for fuzzy estimation and control --- Part I: State estimation. In Proceedings of the 2010 IEEE International Conference on Automation, Quality and Testing, Robotics, pages 1-6, Cluj-Napoca, Romania, May 2010. »
  Abstract: Analysis and observer design for nonlinear systems have long been investigated, but no generally applicable methods exist as yet. A large class of nonlinear systems can be well approximated by Takagi-Sugeno fuzzy models, for which methods and algorithms have been developed to analyze their stability and to design observers. However, results obtainedfor Takagi-Sugeno fuzzy models are in general not directly applicable to the original nonlinear system. In this paper, we investigate what conclusions can be drawn and what guarantees can be expected when an observer is designed based on an approximate fuzzy model and applied to the original nonlinear system. It is shown that in general, exponential stability of the estimation error dynamics cannot be obtained. However, the estimation error is bounded. This bound is computed based on the approximation error and the Lyapunov function used. The results are illustrated using simulation examples. «
• H. Kerkeni, J. Lauber, Zs. Lendek, T.M. Guerra, Individual Cylinder Air/Fuel Ratio Observer on IC Engine Using Takagi-Sugeno's Fuzzy Model. In Proceedings of the 2008 IEEE Vehicle Power and Propulsion Conference, Harbin, China, September 2008. »
  Abstract: The aim of this article is to design an estimator of the individual air-fuel ratio of each cylinder in an turbocharger internal combustion engine. A non linear model of the exhaust manifold is used to describe the dynamic of the different gas mass flows. Then, a Takagi-Sugeno’s fuzzy model is derived from which an observer is developed. Finally, some simulations are given to show the efficiency of the proposed method. «
• H. Kerkeni, J. Lauber, Zs. Lendek, T.M. Guerra, Estimation de la richesse par cylindre dun moteur a combustion interne. In Proceedings of Conference Internationale Francophone d'Automatique, Bucharest, Romania, September 2008.
• Zs. Lendek, K.M. van Schagen, R. Babuska, A. Veersma, B. De Schutter, Cascaded Parameter Estimation for a Water Treatment Plant Using Particle Filters. In Preprints 17th IFAC World Congress, pages 10857-0862, Seoul, Korea, July 2008. »
  Abstract: Advanced online control of drinking water treatment plants requires reliable models. These models in general involve temperature-dependent, uncertain parameters, which can only be measured in laboratory conditions.We propose to estimate these parameters online, using the available pH quality measurements. Since the pH measurements are a nonlinear combination of the system’s states, a particle filter is used. Thanks to the cascaded nature of the plant, the estimation is also performed in a cascaded setting. The performance is evaluated both for simulated and real-world data. Results indicate that the filter can be effectively used to improve the model accuracy. «
• Zs. Lendek, R. Babuska, B. De Schutter, Stability Analysis and Observer Design for Decentralized TS Fuzzy Systems. In Proceedings of the IEEE International Conference on Fuzzy Systems, pages 631-636, Hong Kong, China, June 2008. »
  Abstract: A large class of nonlinear systems can be well approximated by Takagi-Sugeno (TS) fuzzy models, with linear or affine consequents. It is well-known that the stability of these consequent models does not ensure the tability of the overall fuzzy system. Stability conditions developed for TS fuzzy systems in general rely on the feasibility of an associated system of linear matrix inequalities, whose complexity may grow exponentially with the number of rules. We study distributed systems, where the subsystems are represented as TS fuzzy models. For such systems, a centralized analysis is often unfeasible. We analyze the stability of the overall TS system based on the stability of the subsystems and the strength of the interconnection terms. For naturally distributed applications, such as multi-agent systems, when adding new subsystems on-line, the construction and tuning of a centralized observer is often intractable. Therefore, we also propose a decentralized approach to observer design. Applications of such systems include distributed process control, traffic networks, and economic systems. «
• Zs. Lendek, R. Babuska, B. De Schutter, TS Fuzzy Controllers for Cascaded Systems. In Proceedings of AFNC, 2007, Valenciennes, France, 29-30 October 2007. »
  Abstract: A large class of dynamic systems can be decomposed into or approximated by cascaded subsystems. Applications include multi-agent systems, distributed process control, and hierarchical large-scale systems. Nonlinear dynamic systems can be represented as Takagi-Sugeno (TS) fuzzy models, with linear or affine consequents. For cascaded TS systems, it has been proven that the stability of the subsystems implies the stability of the overall system. In this paper, the cascaded approach is used for controller design. A theoretical design method for tracking TS controllers and a simulation example are presented. The results show that the distributed controller achieves the same performance as the centralized one, while leading to increased modularity, reduced complexity, lower computational costs, and easier tuning. «
• Zs. Lendek, R. Babuska, B. De Schutter, Stability of Cascaded Takagi-Sugeno Fuzzy Systems. In Proceedings of FUZZ-IEEE, 2007, pages 505-510, London, UK, July 2007. »
  Abstract: A large class of nonlinear systems can be well approximated by Takagi-Sugeno (TS) fuzzy models, with local models often chosen linear or affine. It is well-known that the stability of these local models does not ensure the stability of the overall fuzzy system. Therefore, several stability conditions have been developed for TS fuzzy systems. We study a special class of nonlinear dynamic systems, that can be decomposed into cascaded subsystems. These subsystems are represented as TS fuzzy models. We analyze the stability of the overall TS system based on the stability of the subsystems. For a general nonlinear, cascaded system, global asymptotic stability of the individual subsystems is not sufficient for the stability of the cascade. However, for the case of TS fuzzy systems, we prove that the stability of the subsystems implies the stability of the overall system. The main benefit of this approach is that it relaxes the conditions imposed when the system is globally analyzed, therefore solving some of the feasibility problems. Another benefit is, that by using this approach, the dimension of the associated linear matrix inequality (LMI) problem can be reduced. Applications of such cascaded systems include multiagent systems, distributed process control and hierarchical large-scale systems. «
• A. Hegyi, L. Mihaylova, R. Boel, Zs. Lendek, Parallelized Particle Filtering for Freeway Traffic State Tracking. In Proceedings of the European Control Conference, 2007, pages 2442-2449, Kos, Greece, July 2007. »
  Abstract: We consider parallelized particle filters for state tracking (estimation) of freeway traffic networks. Particle filters can accurately solve the state estimation problem for general nonlinear systems with non-Gaussian noises. However this high accuracy may come at the cost of high computational demand. We present two parallelized particle filtering algorithms where the calculations are divided over several processing units (PUs) and that reduces the computational demand per processing unit. Existing parallelization approaches typically assign sets of particles to PUs such that each full particle resides at one PU. In contrast, we partition each particle according to a partitioning of the network into subnetworks based on the topology of the network. The centralized case and the two proposed approaches are evaluated with a benchmark problem by comparing the estimation accuracy, computational complexity and communication needs. This approach is in general applicable to systems where it is possible to partition the overall state into subsets of states, such that most of the interaction takes place within the subsets. «
• Zs. Lendek, R. Babuska, B. De Schutter, Distributed Kalman Filtering for Multiagent Systems. In Proceedings of the European Control Conference, 2007, pages 2193-2200, Kos, Greece, July 2007. »
  Abstract: For naturally distributed systems, such as multiagent systems, the construction and tuning of a centralized observer may be computationally expensive or even intractable. An important class of distributed systems can be represented as cascaded subsystems. For this class of systems, observers may be designed separately for the subsystems. If the subsystems are linear, the Kalman filter provides an efficient means to estimate the states, so that it minimizes the mean squared estimation error. Kalman-like filters may be used for the whole system or the individual subsystems. In this paper, both a theoretical comparison and simulation examples are presented. The theoretical results show that the distributed observers, except for special cases, do not minimize the overall error covariance, and so the distributed observer system is suboptimal. However, in practice, the performance achieved by the cascaded observers is comparable and in certain cases outperforms that of the centralized one. Moreover, a distributed observer system leads to increased modularity, reduced complexity, and lower computational costs. «
• R. Babuska, Zs. Lendek, J. Braaksma, C. de Keizer, Particle filtering for on-line estimation of overflow losses in a hopper dredger. In American Control Conference, 2006, pages 5751-5756, Minneapolis, Minnesota, USA, June 2006. »
  Abstract: A particle filter is applied to the estimation of overflow losses in a hopper dredger. The filter estimates online the overflow mixture density and flow-rate, based on the measurements of the total hopper volume, mass, incoming mixture density and flow-rate. These data are readily available on board of every modern hopper dredger. The main advantage of the proposed approach is that the particle filter uses straightforward nonlinear mass balance equations and does not rely on complex sedimentation models with uncertain parameters. The performance was evaluated in simulations as well as with real measurements and the results are encouraging. The filter can be used to improve parameter estimation in complex mechanistic models of the hopper sedimentation process and to facilitate decision making on board of the hopper dredger. «
• Zs. Lendek, P. Raica, Numerical Simulation of 15N Isotope Separation Processes by Ion-Exchange. In Proceedings of the 2004 IEEE-TTTC International Conference on Automation, Quality and Testing, Robotics (AQTR-04), Cluj-Napoca, Romania, May 2004.

PhD thesis

• Zs. Lendek, Distributed Fuzzy and Stochastic Observers for Nonlinear Systems, ISBN 978-90-9023990-3, 186 pages, The Netherlands, 2009. »
  Abstract: Many problems in decision making, control, and monitoring require that all variables of interest, usually states and parameters of the system, are known at all times. However, in practical situations, not all variables are measurable or they are not measured due to technical or economical reasons. Therefore, these variables of interest need to be estimated using an observer. In general, the estimation is based on a dynamic system model and a sequence of measurements.

  This thesis develops efficient observer design methods for nonlinear systems. Two types of systems are considered: deterministic nonlinear systems, represented by continuous-time Takagi-Sugeno fuzzy models, and discrete time stochastic systems. For a large-scale or time-varying system, the design and tuning of an observer may be complicated and involve large computational costs. Therefore, before designing an observer, we consider the structure of the system analyzed in order to reduce the computational costs. For Takagi-Sugeno systems, three structures are investigated: when the system is in cascaded form, when the system is distributed, and when the system is affected by unknown disturbances. For stochastic systems, the case of cascaded systems is considered. The design of cascaded Kalman filters is investigated from a theoretical point of view and the combination of Kalman and particle filters is studied on two application examples: the estimation of the overflow losses in a hopper dredger and the estimation of the model parameters in a water treatment plant.

  «

Technical reports

• Zs. Lendek, R. Babuska, B. De Schutter, State Estimation under Uncertainty: A Survey. Technical report 06-004, 73 pages, February 2006, Delft Center for Systems and Control, Delft University of Technology, The Netherlands. »
  Abstract: We survey the field of multiagent learning and coordination. We introduce a theoretical framework that explicitly models agent dynamics, possibly uncertain actions and observations, and possibly stochastic environments. We classify multiagent systems and formalize relevant concepts in the field using this framework. We then review current work on multiagent learning and coordination, looking at the approaches from the perspective of our framework. We give a brief account of application domains for multiagent systems, and close the work with a set of concluding remarks, identifying some shortcomings that exist in the field as it stands now, and proposing some research questions and directions to alleviate these shortcomings. «

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