DECIDE - AI design of decentralized coopetitive control over networks

The project has resulted in the publications listed below. Use the "»" button to reveal an abstract of each publication, and "«" to hide the abstract again (requires Javascript).

Journal papers

M. Susca, V. Mihaly, Zs. Lendek, I.-C. Morarescu, Passivity of Linear Singularly Perturbed Systems. IEEE Control Systems Letters, 2024. In press. »
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.
Online at IEEEXplore.
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B. Yousuf, Zs. Lendek, L. Busoniu, Exploration-Based Planning for Multiple-Target Search with Real-Drone Results. Sensors, vol. 24, pages/article number 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.
Online at MDPI.
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T. Santejudean, S. Ungur, R. Herzal, I.-C. Morarescu, V.S. Varma, L. Busoniu, Globally convergent path-aware optimization with mobile robots. Nonlinear Analysis - Hybrid Systems, 2024. revised version under review »
Abstract: Consider a mobile robot that must navigate as quickly as possible to the global maxima of a function (e.g. density of seabed litter, pollutant concentration, wireless signal strength) defined over its operating area. This objective function is initially unknown and is assumed to be Lipschitz continuous. The limited velocity of the robot restricts the next samples to neighboring positions, and to avoid wasting time and energy, the robot's path must be adapted as new information becomes available. The paper proposes two methods that use an upper bound on the objective to iteratively change the position targeted by the robot as new samples are acquired. The first method is FTW, which Turns When the best value seen so far of the objective Function is larger than the bound of the current target position. The second is FTWD, an extension of FTW that takes into account the Distance to the target. Convergence guarantees are provided for both methods, and a convergence rate is proven to characterize how fast the FTW suboptimality decreases as the number of samples grows. In a numerical study, FTWD greatly improves performance compared to FTW, outperforms two representative source-seeking baselines, and obtains results similar to a much more computationally intensive method that does not guarantee convergence. The relationship between FTW and FTWD is also confirmed in real-robot experiments, where a TurtleBot3 seeks the darkest point on a 2D grayscale map. «
B. Adhikari, J. Veetaseveera, V.S. Varma, I.-C. Morarescu, E. Panteley, Computationally efficient guaranteed cost control design for homogeneous clustered networks. Automatica, vol. 163, pages/article number 111588, 2023. »
Abstract: We consider a clustered network where connections inside the cluster are dense and between clusters are sparse. This leads us to a classical decoupling into fast (intra-cluster) and slow (inter-cluster) dynamics. Our objective is to provide a computationally efficient method to design control strategies that guarantee a certain bound on the cost for each cluster. Basically, we design a composite synchronizing controller with two terms: one responsible for the intra-cluster synchronization and the other achieving the synchronization between clusters. The first one does not require much computational effort since an analytic expression describes it. The second term is designed through a satisfaction equilibrium approach. In other words, the internal (fast) and external (slow) controllers are independently designed, and they ensure a guaranteed satisfactory cost for each cluster. Moreover, we show that the internal control affects the cluster cost only for a short time period. Finally, numerical simulations illustrate the theoretical results.
Online at ScienceDirect.
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Conference papers

E. Pop, I. Lal, L. Busoniu, Real-Time Simultaneous Optimistic Planning for Hybrid-Input Nonlinear Optimal Control. In 2024 IEEE International Conference on Automation, Quality and Testing, Robotics (AQTR), Cluj-Napoca, Romania, 16–18 May 2024. »
Abstract: Simultaneous Optimistic Planning for Hybrid-Input Systems (SOPHIS) is a powerful method for the near-optimal control of nonlinear systems with hybrid - continuous and discrete - inputs, which works by iteratively splitting sets of input sequences. The generality of SOPHIS however comes at high computational costs that are often untenable in real-time control, especially for fast unstable systems. We introduce two modifications that make SOPHIS more suitable for real-time control: running it on a separate machine, over multiple sampling periods, while applying several inputs to the system during this time; and parallelizing the algorithm by splitting several sets simultaneously across multiple threads. Experiments investigate two parallelization schemes, the impact of thread count on the execution time, and the influence of the prediction horizon and budget; the latter on a real-life fast unstable system, a rotary inverted pendulum. In the experiments, the discrete input controls the quantization accuracy of the control action sent to the system.
Online at IEEEXplore.
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A. Couthures, T. Mongaillard, V. S. Varma, S. Lasaulce, I.-C. Morarescu, Analysis of a continuous opinion and discrete action model coupled with an external dynamics. Accepted at 22nd European Control Conference (ECC), Stockholm, Sweden, 25–28 June 2024. »
Abstract: We consider a set of consumers in a city or town whose opinion is governed by a continuous opinion and discrete action (CODA) dynamics model. This dynamics is coupled with an observation signal dynamics, which defines the information on the common pollution that the consumers can access. We show that the external observation signal has a significant impact on the asymptotic behavior of the CODA model. When the coupling is strong, it induces either a chaotic behavior or convergence towards a limit cycle. When the coupling is weak, a more classical behavior characterized by local agreements in polarized clusters is observed. In both cases, conditions under which clusters of consumers dont change their actions are provided. Numerical examples are provided to illustrate the derived analytical results. «

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