| 1. |
- Helmersson, Anders, 1957-
(författare)
-
µ Synthesis and LFT Gain Scheduling with Real Uncertainties
- 1998
-
Ingår i: International Journal of Robust and Nonlinear Control. - 1049-8923 .- 1099-1239. ; 8:7, s. 631-642
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a solution to synthesis of gain scheduling controllers based on μ-analysis and linear fractional transformations (LFTs). The system is assumed to have parameter dependencies described by LFTs. The goal of the controller is, with real-time knowledge of the parameters, to provide disturbance and error attenuation. The paper treats both complex and real parametric dependencies. © 1998 John Wiley & Sons, Ltd.
|
|
| 2. |
- Adib Yaghmaie, Farnaz, et al.
(författare)
-
Differential graphical games for H-infinity control of linear heterogeneous multiagent systems
- 2019
-
Ingår i: International Journal of Robust and Nonlinear Control. - : WILEY. - 1049-8923 .- 1099-1239. ; 29:10, s. 2995-3013
-
Tidskriftsartikel (refereegranskat)abstract
- Differential graphical games have been introduced in the literature to solve state synchronization problem for linear homogeneous agents. When the agents are heterogeneous, the previous notion of graphical games cannot be used anymore and a new definition is required. In this paper, we define a novel concept of differential graphical games for linear heterogeneous agents subject to external unmodeled disturbances, which contain the previously introduced graphical game for homogeneous agents as a special case. Using our new formulation, we can solve both the output regulation and H-infinity output regulation problems. Our graphical game framework yields coupled Hamilton-Jacobi-Bellman equations, which are, in general, impossible to solve analytically. Therefore, we propose a new actor-critic algorithm to solve these coupled equations numerically in real time. Moreover, we find an explicit upper bound for the overall L2-gain of the output synchronization error with respect to disturbance. We demonstrate our developments by a simulation example.
|
|
| 3. |
- Aguilar, Luis T., et al.
(författare)
-
Generating oscillations in inertia wheel pendulum via two-relay controller
- 2012
-
Ingår i: International Journal of Robust and Nonlinear Control. - Malden : Wiley-Blackwell. - 1049-8923 .- 1099-1239. ; 22:3, s. 318-330
-
Tidskriftsartikel (refereegranskat)abstract
- The problem of generating oscillations of the inertia wheel pendulum is considered. We combine exact feedback linearization with two-relay controller, tuned using frequency-domain tools, such as computing the locus of a perturbed relay system. Explicit expressions for the parameters of the controller in terms of the desired frequency and amplitude are derived. Sufficient conditions for orbital asymptotic stability of the closed-loop system are obtained with the help of the Poincare map. Performance is validated via experiments. The approach can be easily applied for a minimum phase system, provided the behavior of the states of the zero dynamics is of no concern. Copyright (C) 2011 John Wiley & Sons, Ltd.
|
|
| 4. |
- Alisic, Rijad, et al.
(författare)
-
Change time estimation uncertainty in nonlinear dynamical systems with applications to COVID-19
- 2022
-
Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley. - 1049-8923 .- 1099-1239.
-
Tidskriftsartikel (refereegranskat)abstract
- The impact that each individual non-pharmaceutical intervention (NPI) had on the spread rate of COVID-19 is difficult to estimate, since several NPIs were implemented in rapid succession in most countries. In this article, we analyze the detectability of sudden changes in a parameter of nonlinear dynamical systems, which could be used to represent NPIs or mutations of the virus, in the presence of measurement noise. Specifically, by taking an agnostic approach, we provide necessary conditions for when the best possible unbiased estimator is able to isolate the effect of a sudden change in a model parameter, by using the Hammersley–Chapman–Robbins (HCR) lower bound. Several simplifications to the calculation of the HCR lower bound are given, which depend on the amplitude of the sudden change and the dynamics of the system. We further define the concept of the most informative sample based on the largest (Formula presented.) distance between two output trajectories, which is a good indicator of when the HCR lower bound converges. These results are thereafter used to analyze the susceptible-infected-removed model. For instance, we show that performing analysis using the number of recovered/deceased, as opposed to the cumulative number of infected, may be an inferior signal to use since sudden changes are fundamentally more difficult to estimate and seem to require more samples. Finally, these results are verified by simulations and applied to real data from the spread of COVID-19 in France.
|
|
| 5. |
- Amrr, Syed, et al.
(författare)
-
Event-driven fault-tolerant attitude control of spacecraft with finite-time disturbance observer under input saturation
- 2023
-
Ingår i: International Journal of Robust and Nonlinear Control. - : WILEY. - 1049-8923 .- 1099-1239. ; 33:5, s. 3227-3246
-
Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the attitude stabilization problem for a bandwidth-constrained spacecraft subjected to model uncertainty, external disturbances, actuator faults, and saturated input. The proposed attitude controller is developed by combining the disturbance observer with an event-trigger technique to provide disturbance attenuation meanwhile respecting the constraint on the wireless control network. The proposed disturbance observer estimates the lumped disturbance within a finite time, and its output is then fed to the composite control law. The presented control scheme relaxes the use of a priori upper bound knowledge of disturbance and resolves the unwinding problem in the quaternion-based attitude representation. The closed-loop stability analysis under the proposed algorithm shows the uniformly ultimately bounded convergence of state trajectories. Moreover, the designed event trigger approach avoids the Zeno behavior. The numerical simulation with comparative analysis illustrates the efficacy of the proposed controller in terms of convergence time, steady-state bound, rate of control update, and energy consumption.
|
|
| 6. |
- Andersson, Viktor, 1995, et al.
(författare)
-
Controlled Descent Training
- 2024
-
Ingår i: International Journal of Robust and Nonlinear Control. - 1099-1239 .- 1049-8923.
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, a novel and model-based artificial neural network (ANN) training method is developed supported by optimal control theory. The method augments training labels in order to robustly guarantee training loss convergence and improve training convergence rate. Dynamic label augmentation is proposed within the framework of gradient descent training where the convergence of training loss is controlled. First, we capture the training behavior with the help of empirical Neural Tangent Kernels (NTK) and borrow tools from systems and control theory to analyze both the local and global training dynamics (e.g. stability, reachability). Second, we propose to dynamically alter the gradient descent training mechanism via fictitious labels as control inputs and an optimal state feedback policy. In this way, we enforce locally H2 optimal and convergent training behavior. The novel algorithm, Controlled Descent Training (CDT), guarantees local convergence. CDT unleashes new potentials in the analysis, interpretation, and design of ANN architectures. The applicability of the method is demonstrated on standard regression and classification problems.
|
|
| 7. |
- Bemporad, Alberto, et al.
(författare)
-
Hybrid model predictive control based on wireless sensor feedback : An experimental study
- 2010
-
Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley. - 1049-8923 .- 1099-1239. ; 20:2, s. 209-225
-
Tidskriftsartikel (refereegranskat)abstract
- Design and experimental validation of model predictive control (MPC) of a hybrid dynamical laboratory process with wireless sensors is presented. The laboratory process consists of four infrared lamps, controlled in pairs by two on/off switches, and of a transport belt, where moving parts equipped with wireless sensors are heated by the lamps. The process, which is motivated by heating processes in the plastic and printing industry, presents interesting hybrid dynamics. By approximating the stationary heat spatial distribution as a piecewise affine function of the position along the belt, the resulting plant model is a hybrid dynamical system. The control architecture is based on the reference governor approach: the process is actuated by a local controller, while a hybrid MPC algorithm running on a remote base station sends optimal belt velocity setpoints and lamp on/off commands over a wireless link, exploiting the sensor information received through the wireless network. A discrete-time hybrid model of the process is used for the hybrid MPC algorithm and for the state estimator. The physical modelling of the process and the hybrid MPC algorithm are presented in detail, together with the hardware and software architectures. The experimental results show that the presented theoretical framework is well suited for control of the new laboratory process, and that the process can be used as a prototype system for evaluating hybrid and networked control strategies.
|
|
| 8. |
- Boyd, Stephen, et al.
(författare)
-
MIMO PID Tuning via Iterated LMI Restriction
- 2015
-
Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley. - 1099-1239 .- 1049-8923. ; 26:8, s. 1718-1731
-
Tidskriftsartikel (refereegranskat)abstract
- We formulate multi-input multi-output (MIMO) proportional-integral-derivative (PID) controller design as an optimization problem that involves nonconvex quadratic matrix inequalities. We propose a simple method that replaces the nonconvex matrix inequalities with a linear matrix inequality (LMI) restriction, and iterates to convergence. This method can be interpreted as a matrix extension of the convex-concave procedure, or as a particular majorization-minimization (MM) method. Convergence to a local minimum can be guaranteed. While we do not know that the resulting controller is globally optimal, the method works well in practice, and provides a simple automated method for tuning MIMO PID controllers. The method is readily extended in many ways, for example to the design of more complex, structured controllers.
|
|
| 9. |
- Briat, Corentin
(författare)
-
Robust stability and stabilization of uncertain linear positive systems via integral linear constraints : L-1-gain and L-infinity-gain characterization
- 2013
-
Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley. - 1049-8923 .- 1099-1239. ; 23:17, s. 1932-1954
-
Tidskriftsartikel (refereegranskat)abstract
- Copositive linear Lyapunov functions are used along with dissipativity theory for stability analysis and control of uncertain linear positive systems. Unlike usual results on linear systems, linear supply rates are employed here for robustness and performance analysis using L-1-gain and L-gain. Robust stability analysis is performed using integral linear constraints for which several classes of uncertainties are discussed. The approach is then extended to robust stabilization and performance optimization. The obtained results are expressed in terms of robust linear programming problems that are equivalently turned into finite dimensional ones using Handelman's theorem. Several examples are provided for illustration.
|
|
| 10. |
- Byrnes, Christopher I., et al.
(författare)
-
Interior point solutions of variational problems and global inverse function theorems
- 2007
-
Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley. - 1049-8923 .- 1099-1239. ; 17:5-6, s. 463-481
-
Tidskriftsartikel (refereegranskat)abstract
- Variational problems and the solvability of certain nonlinear equations have a long and rich history beginning with calculus and extending through the calculus of variations. In this paper, we are interested in 'well-connected' pairs of such problems which are not necessarily related by critical point considerations. We also study constrained problems of the kind which arise in mathematical programming. We are also interested in interior minimizing points for the variational problem and in the well-posedness (in the sense of Hadamard) of solvability of the related systems of equations. We first prove a general result which implies the existence of interior points and which also leads to the development of certain generalization of the Hadamard-type global inverse function theorem, along the theme that uniqueness quite often implies existence. This result is illustrated by proving the non-existence of shock waves for certain initial data for the vector Burgers' equation. The global inverse function theorem is also illustrated by a derivation of the existence of positive definite solutions of matrix Riccati equations without first analysing the nonlinear matrix Riccati differential equation. The main results on the existence of solutions to geometrically constrained well-connected pairs are then presented and illustrated by a geometric analysis of the existence of interior points for linear programming problems.
|
|
| 11. |
- Dai, L., et al.
(författare)
-
Distributed stochastic MPC for systems with parameter uncertainty and disturbances
- 2018
-
Ingår i: International Journal of Robust and Nonlinear Control. - : John Wiley and Sons Ltd. - 1049-8923 .- 1099-1239. ; 28:6, s. 2424-2441
-
Tidskriftsartikel (refereegranskat)abstract
- A distributed stochastic model predictive control algorithm is proposed for multiple linear subsystems with both parameter uncertainty and stochastic disturbances, which are coupled via probabilistic constraints. To handle the probabilistic constraints, the system dynamics is first decomposed into a nominal part and an uncertain part. The uncertain part is further divided into 2 parts: the first one is constrained to lie in probabilistic tubes that are calculated offline through the use of the probabilistic information on disturbances, whereas the second one is constrained to lie in polytopic tubes whose volumes are optimized online and whose facets' orientations are determined offline. By permitting a single subsystem to optimize at each time step, the probabilistic constraints are then reduced into a set of linear deterministic constraints, and the online optimization problem is transformed into a convex optimization problem that can be performed efficiently. Furthermore, compared to a centralized control scheme, the distributed stochastic model predictive control algorithm only requires message transmissions when a subsystem is optimized, thereby offering greater flexibility in communication. By designing a tailored invariant terminal set for each subsystem, the proposed algorithm can achieve recursive feasibility, which, in turn, ensures closed-loop stability of the entire system. A numerical example is given to illustrate the efficacy of the algorithm. Copyright
|
|
| 12. |
- Dankowicz, Harry, et al.
(författare)
-
On the stabilizability of near-grazing dynamics in impact oscillators
- 2007
-
Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley. - 1049-8923 .- 1099-1239. ; 17:15, s. 1405-1429
-
Tidskriftsartikel (refereegranskat)abstract
- A constructive proof is presented for the existence of event-driven control strategies that guarantee the local persistence of system attractors with at most low-velocity contact in vibro-impacting oscillators. In particular, sufficient conditions are formulated on the linearization of the control strategies along a grazing periodic trajectory, i.e. an oscillating motion that achieves zero-relative-velocity contact with a mechanical obstacle, to ensure the asymptotic stability of the grazing trajectory and, consequently, sustained dynamics in the vicinity of the grazing trajectory even under small changes in system parameters. The implications of the methodology are illustrated with linear and nonlinear, single- and multiple-degree-of-freedom examples of vibro-impact oscillators.
|
|
| 13. |
- Di Benedetto, Maria Domenica, et al.
(författare)
-
Industrial control over wireless networks
- 2010
-
Ingår i: International Journal of Robust and Nonlinear Control. - : JOHN WILEY & SONS LTD. - 1049-8923 .- 1099-1239. ; 20:2, s. 119-122
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
|
|
| 14. |
- Dong, J, et al.
(författare)
-
Fault detection for LPV systems using model parameters that can be estimated via linear least squares
- 2014
-
Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley. - 1099-1239 .- 1049-8923. ; 24:14, s. 1989-1999
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a fault detection approach for discrete-time affine linear parameter varying systems with additive faults. A finite horizon input-output linear parameter varying model is used to obtain a linear in the model parameter regression residual form. The bias in the residual term vanishes because of quadratic stability of an underlying observer. The new methodology avoids projecting the residual onto a parity space, which in real time requires at least quadratic computational complexity. When neglecting the bias, the fault detection is carried out by an χ2 hypothesis test. Finally, the algorithm uses model parameters that can be identified prior to the on-line fault detection with linear least squares. A realtime experiment is carried out to demonstrate the viability of the proposed method.
|
|
| 15. |
- Dong, Yi, et al.
(författare)
-
Coordinated control with multiple dynamic leaders for uncertain Lagrangian systems via self-tuning adaptive distributed observer
- 2017
-
Ingår i: International Journal of Robust and Nonlinear Control. - : John Wiley & Sons. - 1049-8923 .- 1099-1239. ; 27:16, s. 2708-2721
-
Tidskriftsartikel (refereegranskat)abstract
- This paper studies coordinated control of multiple Lagrangian systems with parametric uncertainties subject to external disturbances by proposing a fully distributed continuous control law based on the improved self-tuning adaptive observer inspired by non-identifier-based high-gain adaptive control technique. Under this distributed continuous control law, a group of Lagrangian systems are driven to the convex hull spanned by multiple heterogenous dynamic leaders, which can be any combination of step signals of arbitrary unknown magnitudes, ramp signals of arbitrary unknown slopes, and sinusoidal signals of arbitrary unknown amplitudes, initial phases, and any unknown frequencies. It is also worth to mention that this control law we propose, depending neither on any information of leader systems for uninformed followers, nor on external disturbances, even independent of neighbors' velocity, can achieve asymptotic tracking of multiple leaders without any additional condition instead of ensuring the ultimate boundedness of the containment error as in the literature.
|
|
| 16. |
- Falcone, Paolo, 1977, et al.
(författare)
-
Linear Time Varying Model Predictive Control and its Application to Active Steering Systems: Stability Analysis and Experimental Validation
- 2008
-
Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley. - 1099-1239 .- 1049-8923. ; 18:8, s. 862-875
-
Tidskriftsartikel (refereegranskat)abstract
- A Model Predictive Control (MPC) approach for controlling an Active Front Steering (AFS) system in an autonomous vehicle is presented. At each time step a trajectory is assumed to be known over a finite horizon, and an MPC controller computes the front steering angle in order to best follow the desired trajectory on slippery roads at the highest possible entry speed. We start from the results presented in [2], [6] and formulate the MPC problem based on successive on-line linearization of the nonlinear vehicle model (LTV MPC). We present a sufficient stability conditions for such LTV MPC scheme. The condition is derived for a general class of nonlinear discrete time systems and results into an additional convex constraint to be included in the LTV MPC design. For the AFS control problem, we compare the proposed LTV MPC scheme against the LTV MPC scheme in [6] where stability has been enforced with an ad-hoc constraint. Simulation and experimental tests up to 21 m/s on icy roads show the effectiveness of the LTV MPC formulation.
|
|
| 17. |
- Gao, S., et al.
(författare)
-
Extended prescribed performance control with input quantization for nonlinear systems
- 2022
-
Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley. - 1049-8923 .- 1099-1239. ; 32:6, s. 3801-3821
-
Tidskriftsartikel (refereegranskat)abstract
- For a class of MIMO nonlinear systems, comprised of interconnected subsystems in Brunovsky canonical form, with uncertain yet locally Lipschitz nonlinearities among subsystems and quantized inputs, the target is to form a closed-loop system that exhibits extended prescribed performance on states tracking (accuracy determined by maximum overshoot, minimum convergence rate, maximum steady-state error, and control gains), yet still a low-complexity control structure, without requiring any identification, approximation, and filtering techniques, regardless of uncertainties. In this article, a static, decentralized, continuous, yet computationally inexpensive controller is designed, without requiring parameters of quantizers. Inheriting the merit of pioneering prescribed performance control (PPC) methodology, it is required that the reference signal is (Formula presented.) function only, while, an essential difference and new feature is that, the pioneering PPC guarantees that state tracking errors are constrained by boundary functions (also known as prescribed performance functions, PPFs) only, while, the proposed extend PPC scheme achieves that state tracking errors are constrained by boundary functions and control gains simultaneously, in other words, without “tighter” PPFs, state tracking errors can still be adjusted to arbitrarily small by choosing proper control gains. Finally, comparative simulation results are given to verify the theoretical findings.
|
|
| 18. |
- Glad, Torkel, 1947-, et al.
(författare)
-
Robustness Guarantees for Linear Control Designs with an Estimated Nonlinear Model Error Model
- 2004
-
Ingår i: International Journal of Robust and Nonlinear Control. - Linköping : John Wiley & Sons. - 1049-8923 .- 1099-1239. ; 14:11, s. 959-970
-
Tidskriftsartikel (refereegranskat)abstract
- Much attention in robust identification and control has been focused on linear low order models approximating high order linear systems. We consider the more realistic situation with a linear model approximating a nonlinear system. We describe how a nonlinear model error model can be developed, that allows a complete linear design process that results in a closed loop system with performance robustness guarantees (in terms of gain from disturbance to output) against the nonlinear error. Clearly the design can be successful only if the linear model is a reasonably good approximation of the system. A particular aspect of the design process is to define a workable definition of 'practical stability' for robust control design, with possible non-linear model errors. We use affine norms for that purpose.
|
|
| 19. |
- Gupta, Ankit, 1988, et al.
(författare)
-
Computation of Robust Control Invariant Sets with Predefined Complexity for Uncertain Systems
- 2021
-
Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley. - 1099-1239 .- 1049-8923. ; 31:5, s. 1674-1688
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents an algorithm that computes polytopic robust control-invariant (RCI) sets for rationally parameter-dependent systems with additive disturbances. By means of novel LMI feasibility conditions for invariance along with a newly developed method for volume maximization, an iterative algorithm is proposed for the computation of RCI sets with maximized volumes. The obtained RCI sets are symmetric around the origin by construction and have a user-defined level of complexity. Unlike many similar approaches, fixed state feedback structure is not imposed. In fact, a specific control input is obtained from the LMI problem for each extreme point of the RCI set. The outcomes of the proposed algorithm can be used to construct a piecewise-affine controller based on offline computations.
|
|
| 20. |
- Jacobsen, Elling W., et al.
(författare)
-
Using dynamic perturbations to identify fragilities in biochemical networks
- 2010
-
Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley. - 1049-8923 .- 1099-1239. ; 20:9, s. 1027-1046
-
Tidskriftsartikel (refereegranskat)abstract
- Biological functions at the cellular level result from interactions between genes, proteins and metabolites within complex biochemical reaction networks. Identifying specific and localized fragilities in such networks is important to understand the source of biological malfunctions, and to devise strategies for fighting disease states that have developed robustness. Herein we consider a method based on robust control theoretic concepts for identifying network fragilities. In particular, we consider adding static or dynamic perturbations to the network edges, i.e. the direct binary interactions within the network, and compute the smallest perturbation that induces a bifurcation, and hence a qualitative change, in the network function. The proposed method can also serve as a powerful modeling tool in that it can be used to identify parts of a model that require more detailed descriptions of the underlying processes. The method is demonstrated by application to models of sustained oscillations in the glycolytic pathway and bistability in the mitogen-activated protein kinase (MAPK) signal transduction.
|
|
| 21. |
- Jafarian, Matin
(författare)
-
Robust consensus of unicycles using ternary and hybrid controllers
- 2017
-
Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley-Blackwell. - 1049-8923 .- 1099-1239. ; 27:17, s. 4013-4034
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents consensus of the orientations and average positions for a group of unicycles using ternary and hybrid controllers. The decentralized controllers designed to reach consensus of the average positions take only values in the set {-1; 0; +1}. In addition, a hybrid controller is introduced to control the orientations. Finite-time practical consensus of the average positions is proven despite the simple ternary control laws together with asymptotic consensus of the orientations. Furthermore, the consensus problem is studied in the presence of matched input disturbances that are locally rejected using an internal-model-based controller. The analysis is performed in a hybrid framework. Simulation results illustrate the effectiveness of the design.
|
|
| 22. |
|
|
| 23. |
- Johansson, Rolf, et al.
(författare)
-
The Yakubovich-Kalman-Popov Lemma and Stability Analysis of Dynamic Output Feedback Systems
- 2006
-
Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley. - 1099-1239 .- 1049-8923. ; 16:2, s. 45-69
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents theory related to stability analysis and stability criteria relevant for observer-based feedback control systems. To this purpose, a special formulation of the Yakubovich-Kalman-Popov (YKP) lemma is provided. We exploit that controllability is not necessary for existence of Lur'e-Lyaptinov functions as used in stability criteria. Constructive means for dynamic output feedback stabilization, positivity, factorization and passivity are provided. Copyright (c) 2005 John Wiley & Sons, Ltd.
|
|
| 24. |
- Jönsson, Ulf T.
(författare)
-
Robustness of transitions in switched linear systems
- 2005
-
Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley. - 1049-8923 .- 1099-1239. ; 15:7, s. 293-314
-
Tidskriftsartikel (refereegranskat)abstract
- A robustness problem for transitions in switched linear systems is considered in this paper. The specific problem is to estimate the size of the image when a subset of an affine subspace is mapped by an uncertain system to another affine subspace. It is assumed that the system dynamics is linear and that the uncertainty and the disturbances are characterized by integral quadratic constraints (IQC). The estimates can be obtained by solving a special affinely parameterized linear quadratic optimal control problem. The results are applied to the problem of verifying robustness of oscillations in a switched linear system. In particular, sufficient conditions are given, which ensure that there remains a periodic solution when the system is perturbed by a Lipschitz continuous nonlinearity.
|
|
| 25. |
- Kee, Chew Yee, et al.
(författare)
-
New results in robust functional state estimation using two sliding mode observers in cascade
- 2014
-
Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley-Blackwell. - 1049-8923 .- 1099-1239. ; 24:15, s. 2079-2097
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a functional observer scheme using two sliding mode observers in cascade. A coordinate transformation is performed on the system such that existing sliding mode observer theory can be directly applied to achieve functional state estimation. The necessary and sufficient existence conditions for the scheme (in terms of the original system matrices) are also investigated, and they are found to be less stringent than earlier work on functional state estimation using one sliding mode observer; this could have benefits in terms of cost and simplicity. A numerical example verifies the effectiveness of the scheme.
|
|
| 26. |
|
|
| 27. |
- Kouzoupis, D., et al.
(författare)
-
A dual Newton strategy for scenario decomposition in robust multistage MPC
- 2018
-
Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley. - 1099-1239 .- 1049-8923. ; 28:6, s. 2340-2355
-
Tidskriftsartikel (refereegranskat)abstract
- This paper considers the solution of tree-structured quadratic programs as they may arise in multistage model predictive control. In this context, sampling the uncertainty on prescribed decision points gives rise to different scenarios that are linked to each other via the so-called nonanticipativity constraints. Previous work suggests to dualize these constraints and apply Newton's method on the dual problem to achieve a parallelizable scheme. However, it has been observed that the globalization strategy in such an approach can be expensive. To alleviate this pro blem, we propose to dualize both the nonanticipativity constraints and the dynamics to obtain a computationally cheap globalization. The dual Newton system is then reformulated into small highly structured linear systems that can be solved in parallel to a large extent. The algorithm is complemented by an open-source software implementation that targets embedded optimal control applications.
|
|
| 28. |
- Kouzoupis, D., et al.
(författare)
-
A dual Newton strategy for tree-sparse quadratic programs and its implementation in the open-source software treeQP
- 2019
-
Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley. - 1099-1239 .- 1049-8923. ; 29:8, s. 2438-2457
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a dual Newton scheme for tree-sparse quadratic programs as they may arise in the field of stochastic programming. Previous work suggests to introduce auxiliary variables to decompose the tree into scenarios and use Newton's method to solve a dual problem formulation. Following a different approach, we apply the same principle directly on the tree-sparse problem, avoiding the increase in dimensionality. In combination with a tailored algorithm for the calculation of the step direction, which is typically the most expensive operation per iteration, the proposed algorithm achieves a linear complexity in the number of nodes and supports parallel processing of the tree branches in a stage-wise fashion. An open-source implementation of the presented dual Newton strategy is publicly available in treeQP, a toolbox of open-source solvers for tree-sparse quadratic programs.
|
|
| 29. |
- Kulcsár, Balázs Adam, 1975, et al.
(författare)
-
Unknown input reconstruction for LPV systems
- 2010
-
Ingår i: International Journal of Robust and Nonlinear Control. - 1099-1239 .- 1049-8923. ; 20:5, s. 579-595
-
Tidskriftsartikel (refereegranskat)abstract
- Detection and invariant subspaces of unknown inputs' signals for linear parameter-varying systems are examined in the paper. For a class of nonlinear system like this, the effect of unmeasured signals in parameter-varying measurement equation at the plant output is investigated.The main contributions of the paper are the parameter-varying extension of the pseudo-actuation of the possible and generic unknown sensor signal and the proposition of parameter-dependent similarity transformation. The general parameter-varying measurement equation is casted into a parameter-independent form by the similarity transformation, if any. Moreover, it showed that the nonlinear state transformation does not modify the output subspace spanned by the equivalent pseudo-actuator directions.
|
|
| 30. |
- Köroglu, Hakan, 1971
(författare)
-
Observer-based linear parameter-varying control with guaranteed L2-gain and H2-type performance objectives
- 2014
-
Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley. - 1099-1239 .- 1049-8923. ; 24:14, s. 2000-2017
-
Tidskriftsartikel (refereegranskat)abstract
- Synthesis of an observer-based linear parameter-varying controller is considered for a general linearparameter-varying plant. The parameter vector and its derivative are both assumed to take values in knownbounded domains, whereas only the parameter vector is assumed to be measurable during online operation.The synthesis problem is considered for L2-gain and H2-type performance objectives. Potentially conservativeparameter-dependent linear matrix inequality conditions are derived for the solvability of these twoproblems. To facilitate the reduction of conservatism, the conditions are expressed in a way to have bilineardependence on an arbitrary positive scalar. In addition to employing a suitable relaxation scheme to reducethese conditions into finitely many constraints, a line search hence needs to be performed over the positivescalar to obtain the best achievable performance with an observer-based controller. The online implementationof the observer-based controller is relatively simpler if compared with a controller of unrestrictedstructure. Moreover, the observer-based controller will have no dependence on the parameter derivativesirrespective of the choices of the design variables.
|
|
| 31. |
- Köroglu, Hakan, 1971, et al.
(författare)
-
Robust static output feedback synthesis for platoons under leader and predecessor feedback
- 2017
-
Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley. - 1099-1239 .- 1049-8923. ; 27:10, s. 1726-1756
-
Tidskriftsartikel (refereegranskat)abstract
- A multi-objective static output feedback synthesis problem is considered for the control of vehicle platoonsunder leader and predecessor feedback. Sufficient linear matrix inequality conditions are derived for thesolvability of the problem in a way to facilitate static feed-forward as well. A novel velocity-dependent spacingpolicy is integrated into the control scheme together with a platoon model in which the emphasis on thepredecessor information can be adjusted by a normalized scalar weight. It is shown that the string stability ofthe spacing errors and the acceleration signals can always be guaranteed by choosing this weight sufficientlysmall. Moreover, provided that the time headway is chosen sufficiently large, the synthesis can be performedin a way to avoid the amplification of acceleration energies if compared with the leader. As a particularlyconvenient feature, the target spacing between the vehicles becomes smaller when moving backward alongthe platoon. The total increase in the platoon length caused by the introduction of the velocity-dependentscheme is shown to be bounded and decreasing with decreasing predecessor weight. It is also establishedthat the predecessor weight can be adjusted smoothly over time without endangering the formation stability.In addition to the optimization of the parameters of common fixed-structure controllers for general vehicle models, the proposed synthesis procedure provides various tools for improving robustness against measurement noise, communication delay, and model uncertainty.
|
|
| 32. |
- Liu, Kun, 1982-, et al.
(författare)
-
Discrete-time Network-based Control under Schedulings and Actuator Constraints
- 2014
-
Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley. - 1049-8923 .- 1099-1239.
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- This paper is concerned with the solution bounds for discrete-time networked control systems via delay-dependent Lyapunov-Krasovskii methods.Solution bounds are widely used for systems with input saturation caused byactuator saturation or by the quantizers with saturation.The time-delay approach has been introduced recently for the stabilization of continuous-time networked control systems under the Round-Robin protocol in \cite{KunSCL12} and under a weighted Try-Once-Discard protocol in \cite{KunCDC12}, respectively.Actuator saturation has not been taken into account in \cite{KunCDC12} and \cite{KunSCL12}.In the present paper, for the first time the time-delay approach is extended to the stability analysis of the discrete-time networked control systems under both scheduling protocols and actuators saturation. The communication delays are allowed tobe larger than the sampling intervals.A novel Lyapunov-based method is presented for finding the domain of attraction.Polytopic uncertainties in the system model can be easily included in our analysis. The efficiency of the time-delay approach is illustrated on the example of a cart-pendulum system.
|
|
| 33. |
- Long, Yushen, et al.
(författare)
-
Distributed nonlinear model predictive control based on contraction theory
- 2018
-
Ingår i: International Journal of Robust and Nonlinear Control. - : WILEY. - 1049-8923 .- 1099-1239. ; 28:2, s. 492-503
-
Tidskriftsartikel (refereegranskat)abstract
- A novel distributed model predictive control algorithm for continuous-time nonlinear systems is proposed in this paper. Contraction theory is used to estimate the prediction error in the algorithm, leading to new feasibility and stability conditions. Compared to existing analysis based on Lipschitz continuity, the proposed approach gives a distributed model predictive control algorithm under less conservative conditions, allowing stronger couplings between subsystems and a larger sampling interval when the subsystems satisfy the specified contraction conditions. A numerical example is given to illustrate the effectiveness and advantage of the proposed approach.
|
|
| 34. |
- Luspay, T., et al.
(författare)
-
Set-theoretic analysis of the isolated ramp metering problem
- 2016
-
Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley. - 1099-1239 .- 1049-8923. ; 26:6, s. 1246-1266
-
Tidskriftsartikel (refereegranskat)abstract
- Analysis of ramp metering, as an effective freeway traffic control solution, is focused in the paper. Thestudied traffic control problem is discussed in a set-theoretic context in order to quantitatively characterize its effectiveness. The notions of maximal robust controlled invariant set, as well as t-step robust controllable set are defined and used for analyzing the ramp metering problem independently of the control policy applied. Algorithms are developed to compute these sets, with special attention to their practical interpretations.Numerical examples with graphical representation of the proposed methodology are given to examine localramp metering and conclude implications to control strategies.
|
|
| 35. |
- Meng, Ziyang, et al.
(författare)
-
On distributed finite-time observer design and finite-time coordinated tracking of multiple double integrator systems via local interactions
- 2014
-
Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley. - 1049-8923 .- 1099-1239. ; 24:16, s. 2473-2489
-
Tidskriftsartikel (refereegranskat)abstract
- This paper studies finite-time coordinated tracking problem for multiple double integrator systems with a time-varying leader's velocity and bounded external disturbances. We consider the dynamic feedback designs for two different cases. In the first case, the velocities of the followers and the leader are assumed to be unavailable, and the communication topology is assumed to be undirected and fixed. In the second case, the velocities of the followers and the leader are assumed to be available, and the communication topology is assumed to be directed and switching. Distributed finite-time observers are designed, respectively, to obtain the velocity information in the first case and the relative state information in the second case. The states of these observers are then used to design control inputs that achieve finite time robust coordinated tracking of multiple double integrator systems in the presence of bounded disturbances for these two cases. Simulation results are provided to validate the effectiveness of these theoretical results.
|
|
| 36. |
- Miloševiç, Jezdimir, et al.
(författare)
-
Security Measure Allocation for Industrial Control Systems : Exploiting Systematic Search Techniques and Submodularity
- 2020
-
Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley. - 1049-8923 .- 1099-1239. ; 30:11, s. 4278-4302
-
Tidskriftsartikel (refereegranskat)abstract
- To protect industrial control systems from cyberattacks, multiple layers of security measures need to be allocated to prevent critical security vulnerabilities. However, both finding the critical vulnerabilities and then allocating security measures in a cost‐efficient way become challenging when the number of vulnerabilities and measures is large. This paper proposes a framework that can be used once this is the case. In our framework, the attacker exploits security vulnerabilities to gain control over some of the sensors and actuators. The critical vulnerabilities are those that are not complex to exploit and can lead to a large impact on the physical world through the compromised sensors and actuators. To find these vulnerabilities efficiently, we propose an algorithm that uses the nondecreasing properties of the impact and complexity functions and properties of the security measure allocation problem to speed up the search. Once the critical vulnerabilities are located, the security measure allocation problem reduces to an integer linear program. Since integer linear programs are NP‐hard in general, we reformulate this problem as a problem of minimizing a linear set function subject to a submodular constraint. A polynomial time greedy algorithm can then be applied to obtain a solution with guaranteed approximation bound. The applicability of our framework is demonstrated on a control system used for regulation of temperature within a building.
|
|
| 37. |
- Ng, Kok Yew, et al.
(författare)
-
New results in robust actuator fault reconstruction for linear uncertain systems using sliding mode observers
- 2007
-
Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley Online Library. - 1049-8923 .- 1099-1239. ; 17:14, s. 1294-1319
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a robust actuator fault reconstruction scheme for linear uncertain systems using sliding mode observers. In existing work, fault reconstruction via sliding mode observers is limited to either linear certain systems subject to unknown inputs, relative degree one systems or a specific class of relative degree two systems. This paper presents a new method that is applicable to a wider class of systems with relative degree higher than one, and can also be used for systems with more unknown inputs than outputs. The method uses two sliding mode observers in cascade. Signals from the first observer are processed and used to drive the second observer. Overall, this results in actuator fault reconstruction being feasible for a wider class of systems than using existing methods. A simulation example verifies the claims made in this paper.
|
|
| 38. |
- Nikou, Alexandros, et al.
(författare)
-
Decentralized tube-based model predictive control of uncertain nonlinear multiagent systems
- 2019
-
Ingår i: International Journal of Robust and Nonlinear Control. - : WILEY. - 1049-8923 .- 1099-1239. ; 29:10, s. 2799-2818
-
Tidskriftsartikel (refereegranskat)abstract
- This paper addresses the problem of decentralized tube-based nonlinear model predictive control (NMPC) for a general class of uncertain nonlinear continuous-time multiagent systems with additive and bounded disturbance. In particular, the problem of robust navigation of a multiagent system to predefined states of the workspace while using only local information is addressed under certain distance and control input constraints. We propose a decentralized feedback control protocol that consists of two terms: a nominal control input, which is computed online and is the outcome of a decentralized finite horizon optimal control problem that each agent solves at every sampling time, for its nominal system dynamics; and an additive state-feedback law which is computed offline and guarantees that the real trajectories of each agent will belong to a hypertube centered along the nominal trajectory, for all times. The volume of the hypertube depends on the upper bound of the disturbances as well as the bounds of the derivatives of the dynamics. In addition, by introducing certain distance constraints, the proposed scheme guarantees that the initially connected agents remain connected for all times. Under standard assumptions that arise in nominal NMPC schemes, controllability assumptions, communication capabilities between the agents, it is guaranteed that the multiagent system is input-to-state stable with respect to the disturbances, for all initial conditions satisfying the state constraints. Simulation results verify the correctness of the proposed framework.
|
|
| 39. |
- Rabi, Maben, et al.
(författare)
-
Networked estimation under contention-based medium access
- 2010
-
Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley. - 1049-8923 .- 1099-1239. ; 20:2, s. 140-155
-
Tidskriftsartikel (refereegranskat)abstract
- This paper studies networked estimation over a communication channel shared by a contention-based medium access protocol. A collection of N identical and physically decoupled scalar systems are sampled without sensor noise and transmitted over a common channel, using a contention-based medium access mechanism. We first carry out a calculation of the average distortion in estimation with irregular samples. Given the rate of packet generation at sensors, we characterize the traffic characteristics of the some contention-based MAC schemes. This lets us derive the statistics of inter-arrival times which in turn allows us to compute the packet loss rates and also the statistics of delay within a sample period. Using these results, we track the estimation performance as the sample generation rate and the number of contending nodes are varied. We provide a heuristic rule-of-thumb for choosing the sampling interval which minimizes the average distortion. By combining the network traffic characterization with that of the estimation performance, we show this rule performs pretty well. Carrying along the same lines, we are able to compute the scaling limits of estimation performance with respect to the number of contending nodes.
|
|
| 40. |
- Rantzer, Anders
(författare)
-
Friction Analysis Based on Integral Quadratic Constraints
- 2001
-
Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley. - 1099-1239 .- 1049-8923. ; 11:7, s. 645-652
-
Tidskriftsartikel (refereegranskat)abstract
- Passivity arguments have long been used in the analysis of systems with friction. This paper proves a new set of integral quadratic constraints, which reduces the conservatism of such methods. The result is used to derive a quantitative bound on the amount of integrator leakage that is needed to remove stiction-induced oscillations in a servo system. Finally, an incremental version of the circle criterion is used to study the existence of subharmonics due to friction in a system subject to externally forced oscillations.
|
|
| 41. |
- Ren, Wei, et al.
(författare)
-
Razumikhin stability theorems for a general class of stochastic impulsive switched time-delay systems
- 2019
-
Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley. - 1049-8923 .- 1099-1239. ; 29:12, s. 3988-4001
-
Tidskriftsartikel (refereegranskat)abstract
- This paper studies stability of a general class of impulsive switched systems under time delays and random disturbances using multiple Lyapunov functions and fixed dwell-time. In the studied system model, the impulses and switches are allowed to occur asynchronously. As a result, the switching may occur in the impulsive intervals and the impulses can occur in the switching intervals, which have great effects on system stability. Since the switches do not bring about the change of the system state, we study two cases in terms of the impulses, ie, the stable continuous dynamics case and the stable impulsive dynamics case. According to multiple Lyapunov-Razumikhin functions and the fixed dwell-time, Razumikhin-type stability conditions are established. Finally, the obtained results are illustrated via a numerical example from the synchronization problem of chaotic systems.
|
|
| 42. |
- Sætre, Christian Fredrik, et al.
(författare)
-
Robust orbital stabilization : A Floquet theory-based approach
- 2021
-
Ingår i: International Journal of Robust and Nonlinear Control. - : John Wiley & Sons. - 1049-8923 .- 1099-1239. ; 31:16, s. 8075-8108
-
Tidskriftsartikel (refereegranskat)abstract
- The design of robust orbitally stabilizing feedback is considered. From a known orbitally stabilizing controller for a nominal, disturbance-free system, a robustifying feedback extension is designed utilizing the sliding-mode control (SMC) methodology. The main contribution of the article is to provide a constructive procedure for designing the time-invariant switching function used in the SMC synthesis. More specifically, its zero-level set (the sliding manifold) is designed using a real Floquet–Lyapunov transformation to locally correspond to an invariant subspace of the Monodromy matrix of a transverse linearization. This ensures asymptotic stability of the periodic orbit when the system is confined to the sliding manifold, despite any system uncertainties and external disturbances satisfying a matching condition. The challenging task of oscillation control of the underactuated cart–pendulum system subject to both matched- and unmatched disturbances/uncertainties demonstrates the efficacy of the proposed scheme.
|
|
| 43. |
- Sandberg, Henrik, et al.
(författare)
-
Model approximation using magnitude and phase criteria : Implications for model reduction and system identification
- 2007
-
Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley. - 1049-8923 .- 1099-1239. ; 17:05-6, s. 435-461
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we use convex optimization for model reduction and identification of transfer functions. Two different approximation criteria are studied. When the first criterion is used, magnitude functions are matched, and when the second criterion is used, phase functions are matched. The weighted error bounds have direct interpretation in a Bode diagram, and are suitable to engineers working with frequency-domain data. We also show that transfer functions that have similar magnitude or phase functions have a small relative H-infinity error, under certain stability and minimum phase assumptions. The error bounds come from bounds associated with the Hilbert transform operator restricted in its application to rational transfer functions. Furthermore, it is shown how the approximation procedures can be implemented with linear matrix inequalities, and four examples are included to illustrate the results.
|
|
| 44. |
- Sayyaddelshad, Saleh, et al.
(författare)
-
H∞ observer design for uncertain nonlinear discrete-time systems with time-delay: LMI optimization approach
- 2015
-
Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley. - 1049-8923 .- 1099-1239. ; 25:10, s. 1514-1527
-
Tidskriftsartikel (refereegranskat)abstract
- We present a robust H∞ observer for a class of nonlinear discrete-time systems. The class under study includes an unknown time-varying delay limited by upper and lower bounds, as well as time-varying para- metric uncertainties. We design a nonlinear H∞ observer, by using the upper and lower bounds of the delay, that guarantees asymptotic stability of the estimation error dynamics and is also robust against time-varying parametric uncertainties. The described problem is converted to a standard optimization problem, which can be solved in terms of linear matrix inequalities (LMIs). Then, we expand the problem to a multi-objective optimization problem in which the maximum admissible Lipschitz constant and the minimum disturbance attenuation level are the problem objectives. Finally, the proposed observer is illustrated with two examples.
|
|
| 45. |
- Segundo Sevilla, Felix Rafael, et al.
(författare)
-
Fault-tolerant control design to enhance damping of inter-area oscillations in power grids
- 2013
-
Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley. - 1049-8923 .- 1099-1239. ; 24:8-9, s. 1304-1316
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, passive and active approaches for the design of fault-tolerant controllers (FTCs) are presented. The FTCs are used to improve the damping of inter-area oscillations in a power grid. The effectiveness of using a combination of local and remote (wide area) feedback signals is first demonstrated. The challenge is then to guarantee a minimum level of dynamic performance following a loss of remote signals. The designs are based on regional pole placement using linear matrix inequalities. First, a passive FTC is proposed. It is shown that the computation of the controller reduces to the solution of bilinear matrix inequalities. An iterative procedure is then used to design the controller. Next, as an alternative to active, time-varying controllers, one for each fault scenario, we propose an approach for the design of a ‘minimal switching’ FTC in which only one controller is designed, but where a simple switch is incorporated into the controller structure. A case study in a linear and nonlinear Nordic equivalent system is presented to show that the closed-loop response using a conventional control design could deteriorate the performance or even destabilize the system if the remote signals are lost and to demonstrate the effectiveness of the proposed FTC designs.
|
|
| 46. |
- Soltesz, Kristian, et al.
(författare)
-
An automatic tuner with short experiment and probabilistic plant parameterization
- 2017
-
Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley. - 1099-1239 .- 1049-8923. ; 27:11, s. 1857-1873
-
Tidskriftsartikel (refereegranskat)abstract
- A novel automatic tuning strategy is proposed. It is based on an experiment of very short duration, followed by simultaneous identification of LTI model parameters and an estimate of their error covariance. The parametric uncertainty model is subsequently exploited to design linear controllers with magnitude bounds on some closed-loop transfer function of interest, such as the sensitivity function. The method is demonstrated through industrially relevant examples. Robustness is enforced through probabilistic constraints on the H∞ norms of the sensitivity function, while minimizing load disturbance integral error (IE) to ensure performance. To demonstrate the strength of the proposed method, identification for the mentioned examples is carried out under a high level of measurement noise.
|
|
| 47. |
- Song, Qiang, et al.
(författare)
-
Semi-global and global containment control of multi-agent systems with second-order dynamics and input saturation
- 2016
-
Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley. - 1049-8923 .- 1099-1239. ; 36:16, s. 3460-3480
-
Tidskriftsartikel (refereegranskat)abstract
- This paper considers both semi-global and global containment control for a second-order multi-agent system that is composed by a network of identical harmonic oscillators or double integrators with multiple leaders and input saturation. A distributed low gain feedback algorithm is proposed to solve the semi-global containment control problem for the network whose topology is directed and initial condition is taken from any a priori given bounded set. In particular, by using a parametric Lyapunov equation approach, M-matrix properties and algebraic graph theory, an upper bound of the low gain parameter is estimated such that the low gain feedback matrix can be analytically determined without involving numerical computation. Furthermore, under the assumption that the induced subgraph formed by the followers is strongly connected and detail balanced, two linear feedback protocols are designed for coupled harmonic oscillators and coupled double integrators, respectively, to asymptotically achieve the global containment control of the network with any initial condition. Finally, numerical examples are given to illustrate the effectiveness of the theoretical results
|
|
| 48. |
- Song, Wenjun, et al.
(författare)
-
Relative attitude formation control of multi-agent systems
- 2017
-
Ingår i: International Journal of Robust and Nonlinear Control. - : John Wiley & Sons. - 1049-8923 .- 1099-1239. ; 27:18, s. 4457-4477
-
Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the relative attitude formation control problem for a group of rigid-body agents using relative attitude information on SO(3). On the basis of the gradient of a potential function, a family of distributed angular velocity control laws, which differ in the sense of a geodesic distance dependent function, is proposed. With directed and switching interaction topologies, the desired relative attitude formation is showed to be achieved asymptotically provided that the topology is jointly quasi-strongly connected. Moreover, several sufficient conditions for the desired formation to be achieved exponentially and almost globally are given. Additionally, numerical examples are provided to illustrate the effectiveness of the proposed distributed control laws.
|
|
| 49. |
- Varga, Balázs, 1990, et al.
(författare)
-
Deep Q-learning: a robust control approach
- 2023
-
Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley. - 1099-1239 .- 1049-8923. ; 33:1, s. 526-544
-
Tidskriftsartikel (refereegranskat)abstract
- This work aims at constructing a bridge between robust control theory and reinforcement learning. Although, reinforcement learning has shown admirable results in complex control tasks, the agent’s learning behaviour is opaque. Meanwhile, system theory has several tools for analyzing and controlling dynamical systems. This paper places deep Q-learning is into a control-oriented perspective to study its learning dynamics with well-established techniques from robust control. An uncertain linear time-invariant model is formulated by means of the neural tangent kernel to describe learning. This novel approach allows giving conditions for stability (convergence) of the learning and enables the analysis of the agent’s behaviour in frequency-domain. The control-oriented approach makes it possible to formulate robust controllers that inject dynamical rewards as control input in the loss function to achieve better convergence properties. Three output-feedback controllers are synthesized: gain scheduling H2, dynamical Hinf, and fixed-structure Hinf controllers. Compared to traditional deep Q-learning techniques, which involve several heuristics, setting up the learning agent with a control-oriented tuning methodology is more transparent and has well-established literature. The proposed approach does not use a target network and randomized replay memory. The role of the target network is overtaken by the control input, which also exploits the temporal dependency of samples (opposed to a randomized memory buffer). Numerical simulations in different OpenAI Gym environments suggest that the Hinf controlled learning can converge faster and receive higher scores (depending on the environment) compared to the benchmark Double deep Q-learning.
|
|
| 50. |
- Wang, Lin, et al.
(författare)
-
Connectivity maintenance and distributed tracking for double-integrator agents with bounded potential functions
- 2015
-
Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley. - 1049-8923 .- 1099-1239. ; 25:4, s. 542-558
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we develop a set of decentralized control laws with bounded potential functions. The basic control law is a combination of attractive, repulsive, and alignment forces, which can keep connectivity, avoid collision, synchronize all agents, and further track a constant moving leader. Furthermore, we investigate the distributed tracking problem with a varying-velocity leader, where the acceleration of the leader can not be measured. Two cases are considered; the acceleration of the leader is bounded, and the acceleration function satisfies Lipschitz condition. In the first case, the relative velocities of neighbors are integrated and transmitted as a new variable to account for the uncertain time-varying acceleration. In the second case, two distributed estimators are added for the leader's position and velocity. Finally, some simulations are presented to show the effectiveness of the proposed algorithms.
|
|
