| 1. |
- Arnström, Daniel, et al.
(författare)
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Complexity Certification of Proximal-Point Methods for Numerically Stable Quadratic Programming
- 2021
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Ingår i: IEEE Control Systems Letters. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 2475-1456. ; 5:4, s. 1381-1386
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Tidskriftsartikel (refereegranskat)abstract
- When solving a quadratic program (QP), one can improve the numerical stability of any QP solver by performing proximal-point outer iterations, resulting in solving a sequence of better conditioned QPs. In this letter we present a method which, for a given multi-parametric quadratic program (mpQP) and any polyhedral set of parameters, determines which sequences of QPs will have to be solved when using outer proximal-point iterations. By knowing this sequence, bounds on the worst-case complexity of the method can be obtained, which is of importance in, for example, real-time model predictive control (MPC) applications. Moreover, we combine the proposed method with previous work on complexity certification for active-set methods to obtain a more detailed certification of the proximal-point methods complexity, namely the total number of inner iterations.
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| 2. |
- Bahraini, Masoud, 1991, et al.
(författare)
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Optimal Control Design for Perturbed Constrained Networked Control Systems
- 2021
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Ingår i: IEEE Control Systems Letters. - 2475-1456. ; 5:2, s. 553-558
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Tidskriftsartikel (refereegranskat)abstract
- This letter focuses on an optimal control design problem for a class of perturbed networked control systems where a number of systems, subject to state and input constraints, share a communication network with limited bandwidth. We first formulate an optimal control design problem with a constant feedback gain in order to minimize the communication demand for each system while guaranteeing satisfaction of state and input constraints; we show that this optimization problem is very hard to solve. Then, we formulate the same optimal control design problem with a non-constant feedback gain; we argue that this problem is less difficult and results in a lower, or equal, communication demand in comparison to the design with the constant feedback gain. We illustrate and compare these optimal control designs by a simple example.
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| 3. |
- Batkovic, Ivo, 1992, et al.
(författare)
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A Robust Scenario MPC Approach for Uncertain Multi-Modal Obstacles
- 2021
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Ingår i: IEEE Control Systems Letters. - 2475-1456. ; 5:3, s. 947-952
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Tidskriftsartikel (refereegranskat)abstract
- Motion planning and control algorithms for autonomous vehicles need to be safe, and consider future movements of other road users to ensure collision-free trajectories. In this letter, we present a control scheme based on Model Predictive Control (MPC) with robust constraint satisfaction where the constraint uncertainty, stemming from the road users' behavior, is multimodal. The method combines ideas from tube-based and scenario-based MPC strategies in order to approximate the expected cost and to guarantee robust state and input constraint satisfaction. In particular, we design a feedback policy that is a function of the disturbance mode and allows the controller to take less conservative actions. The effectiveness of the proposed approach is illustrated through two numerical simulations, where we compare it against a standard robust MPC formulation.
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| 4. |
- Greiff, Marcus, et al.
(författare)
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Attitude Control on SU(2): Stability, Robustness, and Similarities
- 2021
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Ingår i: IEEE Control Systems Letters. - 2475-1456. ; 6, s. 73-78
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Tidskriftsartikel (refereegranskat)abstract
- This paper concerns trajectory tracking control of attitude dynamics configured on SU(2). Inspired by a popular geometric tracking controller on SO(3), differential geometric tools are used to derive both continuous and discontinuous attitude controllers on the SU(2) manifold, relating these to preexisting controllers operating with imaginary quaternion errors. Additionally, a robustness result is given for the controllers on SU(2), which is illustrated by simulation examples.
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| 5. |
- Haasler, Isabel, et al.
(författare)
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Optimal Steering of Ensembles with Origin-Destination Constraints
- 2021
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Ingår i: IEEE Control Systems Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 2475-1456. ; 5:3, s. 881-886
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Tidskriftsartikel (refereegranskat)abstract
- We consider the optimal control problem of steering a collection of agents over a network. The group behavior of an ensemble is often modeled by a distribution, and thus the optimal control problem we study can be cast as a distribution steering problem. While most existing works for steering distributions require the agents in the ensemble to be indistinguishable, we consider the setting where agents have specified origin-destination constraints. This control problem also resembles a minimum cost network flow problem with a massive number of commodities. We propose a novel optimal transport based framework for this problem and derive an efficient algorithm for solving it. This framework extends multi-marginal optimal transport theory to settings with capacity and origin-destination constraints. The proposed method is illustrated on a numerical simulation for traffic planning.
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| 6. |
- Heyden, Martin, et al.
(författare)
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A Structured Optimal Controller With Feed-Forward for Transportation
- 2021
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Ingår i: IEEE Control Systems Letters. - 2475-1456. ; 6, s. 1130-1135
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Tidskriftsartikel (refereegranskat)abstract
- We study an optimal control problem for a simple transportation model on a path graph. We give a closed form solution for the optimal controller, which can also account for planned disturbances using feed-forward. The optimal controller is highly structured, which allows the controller to be implemented using only local communication, conducted through two sweeps through the graph.
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| 7. |
- Jouini, Taouba, et al.
(författare)
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On cost design in applications of optimal control
- 2021
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Ingår i: IEEE Control Systems Letters. - 2475-1456. ; 6, s. 452-457
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Tidskriftsartikel (refereegranskat)abstract
- A new approach to feedback control design based on optimal control is proposed. Instead of expensive computations of the value function for different penalties on the states and inputs, we use a control Lyapunov function that amounts to be a value function of the optimal control problem with suitable cost design and then study combinations of input and state penalty that are compatible with this value function. This drastically simplifies the role of the Hamilton-Jacobi-Bellman equation, since it is no longer a partial differential equation to be solved, but an algebraic relationship between different terms of the cost. The paper illustrates this idea in different examples, including H_\infty control and optimal control of coupled oscillators.
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| 8. |
- Jung, Daniel
(författare)
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Distributed Feature Selection for Multi-Class Classification Using ADMM
- 2021
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Ingår i: IEEE Control Systems Letters. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 2475-1456. ; 5:3, s. 821-826
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Tidskriftsartikel (refereegranskat)abstract
- Feature selection is an important task in data-driven control applications to identify relevant features and remove non-informative ones, for example residual selection for fault diagnosis. For multi-class data, the objective is to find a minimal set of features that can distinguish data from all different classes. A distributed feature selection algorithm is derived using convex optimization and the Alternating Direction Method of Multipliers. The distributed algorithm scales well with increasing number of classes by utilizing parallel computations. Two case studies are used to evaluate the developed feature selection algorithm: fault classification of an internal combustion engine and the MNIST data set to illustrate a larger multi-class classification problem.
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| 9. |
- Kergus, Pauline
(författare)
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Data-driven control of infinite dimensional systems : Application to a continuous crystallizer
- 2021
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Ingår i: IEEE Control Systems Letters. - 2475-1456. ; 5:6, s. 2120-2125
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Tidskriftsartikel (refereegranskat)abstract
- Controlling infinite dimensional models remains a challenging task for many practitioners since they are not suitable for traditional control design techniques or will result in a high-order controller too complex for implementation. Therefore, the model or the controller need to be reduced to an acceptable dimension, which is time-consuming, requires some expertise and may introduce numerical error. This paper tackles the control of such a system, namely a continuous crystallizer, and compares two different data-driven strategies: the first one is a structured robust technique while the other one, called L-DDC, is based on the Loewner interpolatory framework.
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| 10. |
- Lindmark, Gustav, 1983-, et al.
(författare)
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Centrality Measures and the Role of Non-Normality for Network Control Energy Reduction
- 2021
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Ingår i: IEEE Control Systems Letters. - : IEEE. - 2475-1456. ; 5:3, s. 1013-1018
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Tidskriftsartikel (refereegranskat)abstract
- Combinations of Gramian-based centrality measures are used for driver node selection in complex networks in order to simultaneously take into account conflicting control energy requirements, like minimizing the average energy needed to steer the state in any direction and the energy needed for the worst direction. The selection strategies that we propose are based on a characterization of the network non-normality. We show that the concept is also related to the idea of balanced realization.
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