| 1. |
- Arnström, Daniel, et al.
(author)
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Complexity Certification of Proximal-Point Methods for Numerically Stable Quadratic Programming
- 2021
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In: 2021 AMERICAN CONTROL CONFERENCE (ACC). - : IEEE. - 9781665441971 ; , s. 947-952
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Conference paper (peer-reviewed)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 paper 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. |
- Greiff, Marcus, et al.
(author)
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Attitude Control on SU(2) : Stability, Robustness, and Similarities
- 2021
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In: 2021 American Control Conference, ACC 2021. - 0743-1619. - 9781665441971 ; 2021-May, s. 1693-1699
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Conference paper (peer-reviewed)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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| 3. |
- Greiff, Marcus, et al.
(author)
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Tuning and Analysis of Geometric Tracking Controllers on SO(3)
- 2021
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In: 2021 American Control Conference, ACC 2021. - 0743-1619. - 9781665441971 ; 2021-May, s. 1674-1680
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Conference paper (peer-reviewed)abstract
- This paper concerns the robustness of attitude controllers for dynamics configured on the SO(3) manifold and poses a set of bilinear matrix inequalities to find an optimal controller tuning with respect to (i) the ultimate bound of the error-state trajectories when perturbed by naturally arising disturbances, and (ii) the worst-case decay rate of the tracking errors. The presented optimization problem can be solved both to generate a robust tuning for experimental applications, and also to facilitate qualitative comparisons of different attitude controllers present in the literature. To solve the tuning problem, we propose an algorithm based on alternating semidefinite programming, with local linearizations of an upper bound of the associated cost function. The soundness of this approach is illustrated by comparison to an interior-point method. The algorithm is subsequently used to provide insights for the tuning of the considered controllers, and finally demonstrated by a closed-loop simulation example.
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| 4. |
- Jorques Moreno, Carlos, et al.
(author)
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Modular Design and Integration of In-Cycle Closed-Loop Combustion Controllers for a Wide-Range of Operating Conditions
- 2021
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In: 2021 American Control Conference, ACC 2021. - 0743-1619. - 9781665441971 ; 2021-May, s. 1875-1881
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Conference paper (peer-reviewed)abstract
- This paper investigates how multiple in-cycle closed-loop combustion controllers can be integrated for a seamless operation under a wide-range of operating conditions. The stochastic cyclic variations of the combustion can be successfully compensated by the adjustment of the fuel injection pulses within the same cycle. The feedback information and controllability obtained relies on the different operating conditions, emissions regulations and fuels. Various in-cycle closed-loop combustion controllers are found in the literature to overcome the numerous challenges of the combustion control. In this paper, the modularization for the controller design and their integration is investigated, and how the transition between the available information, control actions and control strategy affects the final combustion behaviour. The approach consists in the design of a finite-state machine that supervises the transition between virtual sensors and measurements, regulators and the possibility of additional fuel injections. The proposed approach was tested in a Scania D13 engine for a wide-range of operating conditions. The results confirm the improved controllability and reduced steady-state RMSE of the controlled parameters, with a smoother transition between set-points, regardless of operating conditions and fuel.
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| 5. |
- Kergus, Pauline
(author)
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Data-driven control of infinite dimensional systems : Application to a continuous crystallizer
- 2021
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In: 2021 American Control Conference, ACC 2021. - 0743-1619. - 9781665441971 ; 2021-May, s. 1438-1443
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Conference paper (peer-reviewed)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. Model/Controller reduction, Stability of linear systems, Control applications.
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| 6. |
- Martins, Alexandre, et al.
(author)
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Dynamic Management of Multiple Resources in Camera Surveillance Systems*
- 2021
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In: 2021 American Control Conference, ACC 2021. - 0743-1619. - 9781665441971 - 9781728197043 ; 2021-May, s. 2061-2068
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Conference paper (peer-reviewed)abstract
- Distributed camera surveillance systems typically consist of multiple cameras that need to store some fraction of their video streams in a central storage node. The disk space of this node as well as the network between the cameras and this central node constitute shared resources. In the paper the disk space allocation as well as the network bandwidth reservation are solved using techniques normally associated with process control. These include mid-range control and tracking-based control of global shared resources. The approach is evaluated by simulations.
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| 7. |
- Sahyoun, Samir, et al.
(author)
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Proper Orthogonal Decomposition Reduced Order Model for Tear Film Flows
- 2021
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In: 2021 American Control Conference (ACC). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781665441971 - 9781665441988 - 9781728197043 ; , s. 2763-2768
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Conference paper (peer-reviewed)abstract
- Tear film plays a key role in protecting the cornea surface against contaminations and dry eye syndrome which can lead to symptoms of discomfort, visual trouble, and tear film instability with the potential to damage the ocular surface. In this paper, coupled nonlinear partial differential equations of the fourth order proposed by Aydemir et al. to describe the evolution of tear film dynamics are considered. These equations are of Benney type and known to suffer from unbounded behavior and lack of a global attractor. The objective here is to identify a reduced order modeling framework with the potential to be used as a basis for control in future work using smart tears with a surfactant that can modify the surface tension to prevent tear film breakup. Since the dynamics are infinite dimensional and nonlinear, a reduced order model based on the proper orthogonal decomposition (POD) is developed, analyzed, and compared to the full order model. Numerical simulations illustrate that only a small number of POD modes are required to accurately capture the tear film dynamics allowing for the full partial differential model to be represented as a low-dimensional set of coupled ordinary differential equations.
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| 8. |
- Wang, Jie, et al.
(author)
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SparseJSR: A fast algorithm to compute joint spectral radius via sparse SOS decompositions
- 2021
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In: 2021 American Control Conference, ACC 2021. - 0743-1619. - 9781665441971 ; 2021-May, s. 2254-2259
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Conference paper (peer-reviewed)abstract
- This paper focuses on the computation of the joint spectral radius (JSR), when the involved matrices are sparse. We provide a sparse variant of the procedure proposed by Parrilo and Jadbabaie to compute upper bounds of the JSR by means of sum-of-squares (SOS) programming. Our resulting iterative algorithm, called SparseJSR, is based on the term sparsity SOS (TSSOS) framework developed by Wang, Magron and Lasserre, which yields SOS decompositions of polynomials with arbitrary sparse supports. SparseJSR exploits the sparsity of the input matrices to significantly reduce the computational burden associated with the JSR computation. Our algorithmic framework is then successfully applied to compute upper bounds for JSR on randomly generated benchmarks as well as on problems arising from stability proofs of controllers, in relation with possible hardware and software faults.
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