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Ivan Perez Avellaneda

Ivan Perez Avellaneda

I hold a Ph.D. degree in electrical engineering from the University of Vermont, M.Sc in economics and a B.Sc. and License degree in mathematics from the Pontificia Universidad Católica del Perú.

During my doctoral studies I worked on inifinite dimension real analysis, nonlinear control theory, noncommutative algebra and optimization. Specifically, my research lies in the field of reachability analysis of nonlinear systems which involves extending optimization methods to Chen-Fliess series. Prior to this, I worked on algebraic geometry in mathematics and debt-control in economics.

Knowledge is a conjecture susceptible of improvement - K.Popper

Projects


Reachability of Systems


A reachable set is the set of states of a system as a result of a set of inputs and initial conditions. Knowing the possible reachable sets ahead of the execution of the system is useful for the plannification and control of its outputs. Popular offline methodologies to compute these sets for nonlinear systems are the Hamilton-Jacobi approach, Mixed-Monotonicity and set-progration.

My contributions to this topic are the following: first, I provided a reachable set overestimation using interval arithmetics. Second, I extended the Mixed-Monotonicity approach to Chen-Fliess series to configure an Input-Output Mixed-Monotonicity (IOMM) framework. Third, I extended differential analysis tools to Chen-Flies series to improve the IOMM outcome.

Ivan Perez Avellaneda
Fig.1 - Reachable set overestimation by the Mixed-Monotonicity, Gradient Descent and Input-Output Mixed-Monotonicity approaches.

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Ivan Perez Avellaneda
Ivan Perez Avellaneda

Optimization of Chen-Fliess Series


The applications of optimization is pervasive over all scientific disciplines. In nonlinear optimization two techniques standout: line search and trust regions. These are related to first and second order derivatives, respectively. The advantage of the first approach is that it only uses the gradient while the second requires the computation of the Hessian matrix. The second approach is faster when the approximation to the second order of the Taylor polynomial is better.

My contributions to this topic are the following: first, I provided closed forms of real analysis tools such as the Fréchet, Gâteaux derivative, the gradient and Hessian of Chen-Fliess series. Second, I proved the first and second order Mean Value Theorem for Chen-Fliess series using the closed form of the Chen-Fliess series of the sum of two inputs rather than the classical approach by the chain rule. Third, I implemented the Gradient Descent and Newton-Raphson algorithm to optimize Chen-Fliess series.


$$\huge\hspace{-3cm}\min_{\hspace{3cm} u\in \hspace{-3.2cm}\underbrace{\mathcal{U}}_{\hspace{2.2cm} \text{compact set in } L_p^m[0,t]}}\hspace{-3.3cm} \overbrace{F_c[u](t)}^{{\Large\text{Chen-Fliess Series}}}$$
Fig.2 - The optimization problem.

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Ivan Perez Avellaneda
Ivan Perez Avellaneda

Differential monoids


I introduced the theory of differential monoids to the literature to formalize the concepts of differential analysis of Chen-Fliess series. This helps provide a closed-form of the Fréchet and Gâteaux derivative by building a bridge between noncommutative algebra and analysis and extends differential calculus to Chen-Fliess series.

Ivan Perez Avellaneda
Fig.3 - Commutative diagram between the Gâteaux derivative and the language derivative.

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Sponsors:

Ivan Perez Avellaneda
Ivan Perez Avellaneda

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Software


Ivan Perez Avellaneda

The Chen-Fliess Series Python (CFSpy) package is a set of functions used to simulate the output of control systems by means of Chen-Fliess series. CFSpy computes the list of coefficients of the Chen-Fliess series and the list of iterated integrals up to a truncation length. The package, also, provides functions that compute single iterated integrals and Lie derivatives. CFSpy is implemented in Python in the object-oriented paradigm.

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