Impulse-Based Hybrid Motion Control

The impulse-based discrete feedback control has been proposed in previous work for the second-order motion systems with damping uncertainties. The sate-dependent discrete impulse action takes place at zero crossing of one of both states, either relative position or velocity. In this paper, the proposed control method is extended to a general hybrid motion control form. We are using the paradigm of hybrid system modeling while explicitly specifying the state trajectories each time the continuous system state hits the guards that triggers impulsive control actions. The conditions for a stable convergence to zero equilibrium are derived in relation to the control parameters, while requiring only the upper bound of damping uncertainties to be known. Numerical examples are shown for an underdamped closed-loop dynamics with oscillating transients, an upper bounded time-varying positive system damping, and system with an additional Coulomb friction damping.Comment: 6 pages, 4 figures, IEEE conferenc

Teaching, Analyzing, Designing and Interactively Simulating of Sliding Mode Control

This paper introduces an interactive methodology to analize, design, and simulate sliding model controllers for R2 linear systems. This paper reviews sliding mode basic concepts and design methodologies and describes an interactive tool which has been developed to support teaching in this field. The tool helps students by generating a nice graphical and interactive display of most relevant concepts. This fact can be used so that students build their own intuition about the role of different parameters in a sliding mode controller. Described application has been coded with Sysquake using an event-driven solver technique. The Sysquake allows using precise integration methods in real time and handling interactivity in a simple manner.Peer ReviewedPostprint (published version

Learning from Outside the Viability Kernel: Why we Should Build Robots that can Fall with Grace

Despite impressive results using reinforcement learning to solve complex problems from scratch, in robotics this has still been largely limited to model-based learning with very informative reward functions. One of the major challenges is that the reward landscape often has large patches with no gradient, making it difficult to sample gradients effectively. We show here that the robot state-initialization can have a more important effect on the reward landscape than is generally expected. In particular, we show the counter-intuitive benefit of including initializations that are unviable, in other words initializing in states that are doomed to fail.Comment: Proceedings of the 2018 IEEE International Conference on SImulation, Modeling and Programming for Autonomous Robots (SIMPAR), Brisbane, Australia, 16-19 201

Annular billiard dynamics in a circularly polarized strong laser field

We analyze the dynamics of a valence electron of the buckminsterfullerene molecule (C60) subjected to a circularly polarized laser field by modeling it with the motion of a classical particle in an annular billiard. We show that the phase space of the billiard model gives rise to three distinct trajectories: "Whispering gallery orbits", which only hit the outer billiard wall, "daisy orbits" which hit both billiard walls (while rotating solely clockwise or counterclockwise for all time), and orbits which only visit the downfield part of the billiard, as measured relative to the laser term. These trajectories, in general, maintain their distinct features, even as intensity is increased from 10^10 to 10^14 W*cm^-2. We attribute this robust separation of phase space to the existence of twistless tori

Foreign Banks and Credit Volatility: The Case of Latin American Countries

Foreign bank presence has substantially increased in Latin America during the second half of the 1990s, which has prompted an intense debate on its banking and macroeconomic consequences. In this paper, we apply ARCH techniques to jointly estimate the impact of foreign bank presence on the level and volatility of real credit in a panel of eight Latin American countries, using quarterly data over the period 1995:1-2001:4. Results show that, together with financial development, foreign bank presence has contributed to reduce real credit volatility, improving the buffer shock function of the banking sector. This finding is consistent with the fact that foreign banks are typically well diversified institutions holding higher quality assets and having access to a broad set of liquidity sources. Keywords: foreign banks; credit volatility; Latin America; panel data; ARCH techniquesForeign Banks; Credit Volatility; Latin America; Panel Data; ARCH techniques

Combining Model-Based and Model-Free Updates for Trajectory-Centric Reinforcement Learning

Reinforcement learning (RL) algorithms for real-world robotic applications need a data-efficient learning process and the ability to handle complex, unknown dynamical systems. These requirements are handled well by model-based and model-free RL approaches, respectively. In this work, we aim to combine the advantages of these two types of methods in a principled manner. By focusing on time-varying linear-Gaussian policies, we enable a model-based algorithm based on the linear quadratic regulator (LQR) that can be integrated into the model-free framework of path integral policy improvement (PI2). We can further combine our method with guided policy search (GPS) to train arbitrary parameterized policies such as deep neural networks. Our simulation and real-world experiments demonstrate that this method can solve challenging manipulation tasks with comparable or better performance than model-free methods while maintaining the sample efficiency of model-based methods. A video presenting our results is available at https://sites.google.com/site/icml17pilqrComment: Paper accepted to the International Conference on Machine Learning (ICML) 201

An examination of the keyboard technique of Bach, Haydn, Chopin, Scriabin and Prokofiev

Master's Project (M.Mu.) University of Alaska Fairbanks, 2016In this research paper, I will explore the keyboard technique of each composer presented in my recital: J.S. Bach, Franz Joseph Haydn, Frederic Chopin, Alexander Scriabin and Sergei Prokofiev. I hope to elucidate the physical approach used by each composer, and show in turn how that same approach influenced the music of each composer by analyzing the pieces performed in my recital. To understand the distinct technique of the composers, it is important to know some context. The instrument each composer wrote for necessarily influenced their technique and resulting composition. However, the instrument cannot explain every facet of technique, and it becomes necessary to understand the underlying aesthetics of technique. Moving chronologically from Bach to Prokofiev, a general trend of expansion in the use of the hand and arm will be seen throughout. Keyboards became louder and heavier in touch and the hand faced greater reaches in every generation. The technique of Bach and Haydn was largely focused on compact and relaxed hands with distinct finger movements, while Scriabin and Prokofiev at the other end require sweeping gestures that occupy the entire arm. However, it would be too easy to present this progression as a story that technique is only getting better and better, implying that the older composers were inferior to the later. That is simply false. Instead, extended study of each composer shows that many technical principles are universal. The baroque keyboardists were likely playing with more weight than popularly imagined and one cannot play Scriabin with mittens on the hands