10 research outputs found
emgr - The Empirical Gramian Framework
System Gramian matrices are a well-known encoding for properties of
input-output systems such as controllability, observability or minimality.
These so-called system Gramians were developed in linear system theory for
applications such as model order reduction of control systems. Empirical
Gramian are an extension to the system Gramians for parametric and nonlinear
systems as well as a data-driven method of computation. The empirical Gramian
framework - emgr - implements the empirical Gramians in a uniform and
configurable manner, with applications such as Gramian-based (nonlinear) model
reduction, decentralized control, sensitivity analysis, parameter
identification and combined state and parameter reduction
Custom optimization algorithms for efficient hardware implementation
The focus is on real-time optimal decision making with application in advanced control
systems. These computationally intensive schemes, which involve the repeated solution of
(convex) optimization problems within a sampling interval, require more efficient computational
methods than currently available for extending their application to highly dynamical
systems and setups with resource-constrained embedded computing platforms.
A range of techniques are proposed to exploit synergies between digital hardware, numerical
analysis and algorithm design. These techniques build on top of parameterisable
hardware code generation tools that generate VHDL code describing custom computing
architectures for interior-point methods and a range of first-order constrained optimization
methods. Since memory limitations are often important in embedded implementations we
develop a custom storage scheme for KKT matrices arising in interior-point methods for
control, which reduces memory requirements significantly and prevents I/O bandwidth
limitations from affecting the performance in our implementations. To take advantage of
the trend towards parallel computing architectures and to exploit the special characteristics
of our custom architectures we propose several high-level parallel optimal control
schemes that can reduce computation time. A novel optimization formulation was devised
for reducing the computational effort in solving certain problems independent of the computing
platform used. In order to be able to solve optimization problems in fixed-point
arithmetic, which is significantly more resource-efficient than floating-point, tailored linear
algebra algorithms were developed for solving the linear systems that form the computational
bottleneck in many optimization methods. These methods come with guarantees
for reliable operation. We also provide finite-precision error analysis for fixed-point implementations
of first-order methods that can be used to minimize the use of resources while
meeting accuracy specifications. The suggested techniques are demonstrated on several
practical examples, including a hardware-in-the-loop setup for optimization-based control
of a large airliner.Open Acces
Data based predictive control: Application to water distribution networks
In this thesis, the main goal is to propose novel data based predictive
controllers to cope with complex industrial infrastructures such as water
distribution networks. This sort of systems have several inputs and out-
puts, complicate nonlinear dynamics, binary actuators and they are usually
perturbed by disturbances and noise and require real-time control implemen-
tation. The proposed controllers have to deal successfully with these issues
while using the available information, such as past operation data of the
process, or system properties as fading dynamics.
To this end, the control strategies presented in this work follow a predic-
tive control approach. The control action computed by the proposed data-
driven strategies are obtained as the solution of an optimization problem
that is similar in essence to those used in model predictive control (MPC)
based on a cost function that determines the performance to be optimized.
In the proposed approach however, the prediction model is substituted by
an inference data based strategy, either to identify a model, an unknown
control law or estimate the future cost of a given decision. As in MPC, the
proposed strategies are based on a receding horizon implementation, which
implies that the optimization problems considered have to be solved online.
In order to obtain problems that can be solved e ciently, most of the
strategies proposed in this thesis are based on direct weight optimization
for ease of implementation and computational complexity reasons. Linear
convex combination is a simple and strong tool in continuous domain and
computational load associated with the constrained optimization problems
generated by linear convex combination are relatively soft. This fact makes
the proposed data based predictive approaches suitable to be used in real
time applications.
The proposed approaches selects the most adequate information (similar
to the current situation according to output, state, input, disturbances,etc.),
in particular, data which is close to the current state or situation of the
system. Using local data can be interpreted as an implicit local linearisation
of the system every time we solve the model-free data driven optimization
problem. This implies that even though, model free data driven approaches
presented in this thesis are based on linear theory, they can successfully deal
with nonlinear systems because of the implicit information available in the
database.
Finally, a learning-based approach for robust predictive control design for
multi-input multi-output (MIMO) linear systems is also presented, in which
the effect of the estimation and measuring errors or the effect of unknown
perturbations in large scale complex system is considered
Numerical methods for advection-diffusion-reaction equations and medical applications
The purpose of this thesis is twofold, firstly, the study of a relaxation procedure for numerically solving advection-diffusion-reaction equations, and secondly, a medical application. Concerning the first topic, we extend the applicability of the Cattaneo relaxation approach to reformulate time-dependent advection-diffusion-reaction equations, that may include stiff reactive terms, as hyperbolic balance laws with stiff source terms. The resulting systems of hyperbolic balance laws are solved by extending the applicability of existing high-order ADER schemes, including well-balanced and non-conservative schemes. Moreover, we also present a new locally implicit version of the ADER method to solve general hyperbolic balance laws with stiff source terms. The relaxation procedure depends on the choice of a relaxation parameter . Here we propose a criterion for selecting in an optimal manner, relating the order of accuracy of the numerical scheme used, the mesh size and the chosen . This results in considerably more efficient schemes than some methods with the parabolic restriction reported in the current literature. The resulting present methodology is validated by applying it to a blood flow model for a network of viscoelastic vessels, for which experimental and numerical results are available. Convergence-rates assessment for some selected second-order model equations, is carried out, which also validates the applicability of the criterion to choose the relaxation parameter. The second topic of this thesis concerns the numerical study of the haemodynamics impact of stenoses in the internal jugular veins. This is motivated by the recent discovery of a range of extra cranial venous anomalies, termed Chronic CerbroSpinal Venous Insufficiency (CCSVI) syndrome, and its potential link to neurodegenerative diseases, such as Multiple Sclerosis. The study considers patient specific anatomical configurations obtained from MRI data. Computational results are compared with measured data
Proceedings of the ECCOMAS Thematic Conference on Multibody Dynamics 2015
This volume contains the full papers accepted for presentation at the ECCOMAS Thematic Conference on Multibody Dynamics 2015 held in the Barcelona School of Industrial Engineering, Universitat Politècnica de Catalunya, on June 29 - July 2, 2015. The ECCOMAS Thematic Conference on Multibody Dynamics is an international meeting held once every two years in a European country. Continuing the very successful series of past conferences that have been organized in Lisbon (2003), Madrid (2005), Milan (2007), Warsaw (2009), Brussels (2011) and Zagreb (2013); this edition will once again serve as a meeting point for the international researchers, scientists and experts from academia, research laboratories and industry working in the area of multibody dynamics. Applications are related to many fields of contemporary engineering, such as vehicle and railway systems, aeronautical and space vehicles, robotic manipulators, mechatronic and autonomous systems, smart structures, biomechanical systems and nanotechnologies. The topics of the conference include, but are not restricted to: ● Formulations and Numerical Methods ● Efficient Methods and Real-Time Applications ● Flexible Multibody Dynamics ● Contact Dynamics and Constraints ● Multiphysics and Coupled Problems ● Control and Optimization ● Software Development and Computer Technology ● Aerospace and Maritime Applications ● Biomechanics ● Railroad Vehicle Dynamics ● Road Vehicle Dynamics ● Robotics ● Benchmark ProblemsPostprint (published version
Modelos Paralelos para la ResoluciĂłn de Problemas de IngenierĂa AgrĂcola
El presente trabajo se inscribe en el campo de la computaciĂłn paralela y,
más en concreto, en el desarrollo y utilización de modelos computacionales
en arquitecturas paralelas heterogéneas para la resolución de problemas
aplicados. En la tesis abordamos una serie de problemas que están relacionados
con la aplicaciĂłn de la tecnologĂa en el ámbito de las explotaciones
agrĂcolas y comprenden: la representaciĂłn del relieve, el manejo de informaciĂłn
climática como la temperatura, y la gestiĂłn de recursos hĂdricos. El
estudio y la solución a estos problemas en el área en la que se han estudiado
tienen un amplio impacto econĂłmico y medioambiental. Los problemas basan
su formulación en un modelo matemático cuya solución es costosa desde
el punto de vista computacional, siendo incluso a veces inviable. La tesis
consiste en implementar algoritmos paralelos rápidos y eficientes que resuelven
el problema matemático asociado a estos problemas en nodos multicore
y multi-GPU. También se estudia, propone y aplican técnicas que permiten
a las rutinas diseñadas adaptarse automáticamente a las caracterĂsticas
del sistema paralelo donde van a ser instaladas y ejecutadas con el objeto
de obtener la versión más cercana posible a la óptima a un bajo coste. El
objetivo es proporcionar un software a los usuarios que sea portable, pero
a la vez, capaz de ejecutarse eficientemente en la ordenador donde se esté
trabajando, independientemente de las caracterĂsticas de la arquitectura y
de los conocimientos que el usuario pueda tener sobre dicha arquitectura.Do Carmo Boratto, M. (2015). Modelos Paralelos para la ResoluciĂłn de Problemas de IngenierĂa AgrĂcola [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/48529TESI
Multibody dynamics 2015
This volume contains the full papers accepted for presentation at the ECCOMAS Thematic Conference on Multibody Dynamics 2015 held in the Barcelona School of Industrial Engineering, Universitat Politècnica de Catalunya, on June 29 - July 2, 2015. The ECCOMAS Thematic Conference on Multibody Dynamics is an international meeting held once every two years in a European country. Continuing the very successful series of past conferences that have been organized in Lisbon (2003), Madrid (2005), Milan (2007), Warsaw (2009), Brussels (2011) and Zagreb (2013); this edition will once again serve as a meeting point for the international researchers, scientists and experts from academia, research laboratories and industry working in the area of multibody dynamics. Applications are related to many fields of contemporary engineering, such as vehicle and railway systems, aeronautical and space vehicles, robotic manipulators, mechatronic and autonomous systems, smart structures, biomechanical systems and nanotechnologies. The topics of the conference include, but are not restricted to: Formulations and Numerical Methods, Efficient Methods and Real-Time Applications, Flexible Multibody Dynamics, Contact Dynamics and Constraints, Multiphysics and Coupled Problems, Control and Optimization, Software Development and Computer Technology, Aerospace and Maritime Applications, Biomechanics, Railroad Vehicle Dynamics, Road Vehicle Dynamics, Robotics, Benchmark Problems. The conference is organized by the Department of Mechanical Engineering of the Universitat Politècnica de Catalunya (UPC) in Barcelona. The organizers would like to thank the authors for submitting their contributions, the keynote lecturers for accepting the invitation and for the quality of their talks, the awards and scientific committees for their support to the organization of the conference, and finally the topic organizers for reviewing all extended abstracts and selecting the awards nominees.Postprint (published version
Solving time-invariant differential matrix Riccati equations using GPGPU computing
Differential matrix Riccati equations (DMREs) enable to model many physical systems appearing in different branches of science, in some cases, involving very large problem sizes. In this paper, we propose an adaptive algorithm for time-invariant DMREs that uses a piecewise-linearized approach based on the PadĂ© approximation of the matrix exponential. The algorithm designed is based upon intensive use of matrix products and linear system solutions so we can seize the large computational capability that modern graphics processing units (GPUs) have on these types of operations using CUBLAS and CULATOOLS libraries (general purpose GPU), which are efficient implementations of BLAS and LAPACK libraries, respectively, for NVIDIA © GPUs. A thorough analysis showed that some parts of the algorithm proposed can be carried out in parallel, thus allowing to leverage the two GPUs available in many current compute nodes. Besides, our algorithm can be used by any interested researcher through a friendly MATLAB © interface.Peinado Pinilla, J.; Alonso-Jordá, P.; Ibáñez González, JJ.; Hernández GarcĂa, V.; Do Carmo Boratto, M. (2014). Solving time-invariant differential matrix Riccati equations using GPGPU computing. Journal of Supercomputing. 70(2):623-636. doi:10.1007/s11227-014-1111-3623636702Anderson E et al (1994) LAPACK users’ guide. SIAM, PhiladelphiaArias E, Hernández V, Ibáñez J, Peinado J (2007) A fixed point-based BDF method for solving Riccati equations. Appl Math Comput 188(2):1319–1333Benner P, Mena H (2004) BDF methods for large-scale differential Riccati equations. In: 16th International symposium on mathematical theory of network and systems (MTNS2004), Katholieke Universiteit Leuven, BelgiumBenner P, Mena H (2013) Rosenbrock methods for solving Riccati differential equations. IEEE Trans Autom Control 58(11):2950–2956Chandrasekhar H (1976) Generalized Chandrasekhar algorithms: time-varying models. IEEE Trans Autom Control 21:728–732Chen B, Company R, Jdar L, Rosell MD (2007) Constructing accurate polynomial approximations for nonlinear differential initial value problems. Appl Math Comput 193:523–534Choi CH (1988) Efficient algorithms for solving stiff matrix-valued Riccati differential equations. PhD thesis, University of California, CaliforniaChoi CH (1992) Time-varying Riccati differential equations with known analytic solutions. IEEE Trans Autom Control 37:642–645Davison EJ, Maki MC (1973) The numerical solution of the matrix Riccati differential equation. IEEE Trans Autom Control 18(1):71–73Defez E, Hervs A, Soler L, Tung MM (2007) Numerical solutions of matrix differential models using cubic matrix splines II. Math Comput Model 46:657–669Dieci L (1992) Numerical integration of the differential Riccati equation and some related issues. SIAM J Numer Anal 29(3):781–815EM Photonics (2011) CULATOOLS, R12 ednHernández V, Ibáñez J, Arias E, Peinado J (2008) A GMRES-based BDF method for solving differential Riccati equations. Appl. Math. Comput. 196(2):613–626Horn RA, Johnson CR (1991) Topics in matrix analysis. Cambridge University Press, LondonIbáñez J, Hernández V (2010) Solving differential matrix Riccati equations by a piecewise-linearized method based on the conmutant equation. Comput Phys Commun 180:2103–2114Ibáñez J, Hernández V (2011) Solving differential matrix Riccati equations by a piecewise-linearized method based on diagonal PadĂ© approximants. Comput Phys Commun 182:669–678Ibáñez J, Hernández V, Arias E, Ruiz P (2009) Solving initial value problems for ordinary differential equations by two approaches: BDF and piecewise-linearized methods. Comput Phys Commun 180(5):712–723Kenney CS, Leipnik RB (1985) Numerical integration of the differential matrix Riccati equation. IEEE Trans Autom Control 30:962–970Li R-C (2000) Unconventional reflexive numerical methods for matrix differential Riccati. In: Technical report 2000-36, Department of Mathematics, University of Kentucky, LexingtonMathWorks (2013) MATLAB MEX files. http://www.mathworks.es/es/help/matlab/create-mex-files.html . Accessed June 2013MathWorks (2013) MATLAB parallel computing toolbox. http://www.mathworks.es/products/parallel-computing . Accessed June 2013Meyer GH (1973) Initial value methods for boundary value problems. Academic Press, New YorkNVIDIA Corporation (2013) CUBLAS library. http://docs.nvidia.com/cuda/cublas/ . Accessed June 2013NVIDIA Corporation (2013) CUDA C programming guide. http://docs.nvidia.com/cuda/cuda-c-programming-guide . Accessed June 2013Ramos JI, GarcĂa CM (1997) Piecewise-linearized methods for initial-value problems. Appl Math Comput 82:273–302Rand DW, Winternitz P (1984) Nonlinear superposition principles: a new numerical method for solving matrix Riccati equations. Comput Phys Commun 33:305–328Sanz-Serna JM (1992) Symplectic integrators for Hamiltonian problems: an overview. Acta Numer 1:243–286Sastre J, Ibez J, Defez E, Ruiz P (2011) Accurate matrix exponential computation to solve coupled differential models in engineering. Math Comput Model 54:1835–1840Sorine M, Winternitz P (1985) Superposition laws for the solution of differential Riccati equations. IEEE Trans Autom Control 30:266–272Vaughan DR (1969) A negative exponential solution for the matrix Riccati equation. IEEE Trans Autom Control 14(1):72–7