Design and Verification of a Compact Variable Stiffness Actuator With a Very Large Range of Stiffness

Current conventional robots require high stiffness joints to provide absolute positioning accuracy in free space which also causes problems when operating in constrained space. To circumvent these problems, Variable Stiffness Actuators (VSAs) can be used to vary their stiffness to suit the task being performed. A new VSA was designed to provide a very large range of stiffness in a compact size. The Arched Flexure VSA uses a cantilevered beam acting as the flexure with a variable point of contact. It allows the joint to have continuous variable stiffness, have zero stiffness for a small range of motion, and rapid stiffness change. Finite element analysis was used to evaluate flexture stiffness. The flexure geometry was optimized for two different objectives. In the first case, the flexture was optimized for maximum stiffness range. This optimization resulted in a stiffness ratio of 1200. In the second case, the flexture was optimized for both maximum stiffness range and constant relative sensitivity. This optimization resulted in a stiffness ratio of 100. A small proof-of-concept VSA actuator based on the constant relative sensitivity alternative was designed, built, and tested. The VSA provided a stiffness ratio of 55, a little more than half of that expected for the flexure alone. The VSA weighed 1.45 pounds and fits within a 4.5 inch by 2 inch by 5 inch volume. The VSA provides the anticipated free joint range for zero stiffness and provides 360 degrees of rotation. It changes from minimum to maximum stiffness in 0.12 seconds

The Effects of Pre-Trial Event Stimulus Properties on Timing in the Peak Interval Procedure

In the peak interval procedure, intruded conditioned stimuli produce shifts in peak/middle time towards later values, regardless of whether these stimuli are presented prior to or during the timing signal. Although the effects of during-trial stimulus properties—temporal location, duration, and salience—have been previously reported, no research exists on how before-trial stimulus properties influence the extent of shifts in middle time. In the present study, we manipulated within subjects both the temporal location and type (i.e., cue alone, response-independent reinforcer alone, or cue and response-contingent reinforcer together) of the pre-trial event. An individual-trial analysis suggested that the type of stimulus event governs the extent of the shifts in middle time, with larger shifts observed on trials preceded by a reinforcer, either alone or in conjunction with a conditioned cue, than on trials that were preceded by the conditioned cue alone. These results indicate that reinforcers can disrupt timing by means other than a reset of working memory—an account that is common in prior investigations of reinforcers in timing tasks. In addition, we found a time-dependent effect of the event, with larger shifts in middle time engendered by events more contiguous to the timing signal, suggesting that the postcue effect dissipates following the offset of the event

The Arched Flexure VSA: A Compact Variable Stiffness Actuator with Large Stiffness Range

The high stiffness of conventional robots is beneficial in attaining highly accurate positioning in free space. High stiffness, however, limits a robot\u27s ability to perform constrained manipulation. Because of the high stiffness, geometric conflict between the robot and task constraints during constrained manipulation can lead to excessive forces and task failure. Variable stiffness actuators can be used to adjust the stiffness of robot joints to allow high stiffness in unconstrained directions and low stiffness in constrained directions. Two important design criteria for variable stiffness actuation are a large range of stiffness and a compact size. A new design, the Arched Flexure VSA, uses a cantilevered beam flexure of variable cross-section and a controllable load location. It allows the joint to have continuously variable stiffness within a finite stiffness range, have zero stiffness for a small range of joint motion, and allow rapid adjustment of stiffness. Using finite element analysis, flexure geometry was optimized to achieve high stiffness in a compact size. A proof-of-concept prototype demonstrated continuously variable stiffness with a ratio of high stiffness to low stiffness of 55

Multiagent Reinforcement Learning for Autonomous Routing and Pickup Problem with Adaptation to Variable Demand

We derive a learning framework to generate routing/pickup policies for a fleet of vehicles tasked with servicing stochastically appearing requests on a city map. We focus on policies that 1) give rise to coordination amongst the vehicles, thereby reducing wait times for servicing requests, 2) are non-myopic, considering a-priori unknown potential future requests, and 3) can adapt to changes in the underlying demand distribution. Specifically, we are interested in adapting to fluctuations of actual demand conditions in urban environments, such as on-peak vs. off-peak hours. We achieve this through a combination of (i) online play, a lookahead optimization method that improves the performance of rollout methods via an approximate policy iteration step, and (ii) an offline approximation scheme that allows for adapting to changes in the underlying demand model. In particular, we achieve adaptivity of our learned policy to different demand distributions by quantifying a region of validity using the q-valid radius of a Wasserstein Ambiguity Set. We propose a mechanism for switching the originally trained offline approximation when the current demand is outside the original validity region. In this case, we propose to use an offline architecture, trained on a historical demand model that is closer to the current demand in terms of Wasserstein distance. We learn routing and pickup policies over real taxicab requests in downtown San Francisco with high variability between on-peak and off-peak hours, demonstrating the ability of our method to adapt to real fluctuation in demand distributions. Our numerical results demonstrate that our method outperforms rollout-based reinforcement learning, as well as several benchmarks based on classical methods from the field of operations research.Comment: 7 pages, 6 figures, 3 tables, submitted to ICR

Approximate Multiagent Reinforcement Learning for On-Demand Urban Mobility Problem on a Large Map (extended version)

In this paper, we focus on the autonomous multiagent taxi routing problem for a large urban environment where the location and number of future ride requests are unknown a-priori, but follow an estimated empirical distribution. Recent theory has shown that if a base policy is stable then a rollout-based algorithm with such a base policy produces a near-optimal stable policy. Although, rollout-based approaches are well-suited for learning cooperative multiagent policies with considerations for future demand, applying such methods to a large urban environment can be computationally expensive. Large environments tend to have a large volume of requests, and hence require a large fleet of taxis to guarantee stability. In this paper, we aim to address the computational bottleneck of multiagent (one-at-a-time) rollout, where the computational complexity grows linearly in the number of agents. We propose an approximate one-at-a-time rollout-based two-phase algorithm that reduces the computational cost, while still achieving a stable near-optimal policy. Our approach partitions the graph into sectors based on the predicted demand and an user-defined maximum number of agents that can be planned for using the one-at-a-time rollout approach. The algorithm then applies instantaneous assignment (IA) for re-balancing taxis across sectors and a sector-wide one-at-a-time rollout algorithm that is executed in parallel for each sector. We characterize the number of taxis $m$ that is sufficient for IA base policy to be stable, and derive a necessary condition on $m$ as time goes to infinity. Our numerical results show that our approach achieves stability for an $m$ that satisfies the theoretical conditions. We also empirically demonstrate that our proposed two-phase algorithm has comparable performance to the one-at-a-time rollout over the entire map, but with significantly lower runtimes.Comment: 11 pages, 5 figures, 1 lemma, and 2 theorem

"Instalación y puesta en marcha de una estación de servicio de gas natural de 2000 MCH. empresa de transporte terrestre Villa El Salvador SAC"

La instalación y puesta en marcha de la estación de servicio de gas natural, nace de la necesidad de buscar alternativas económicas para satisfacer la demanda de combustible requerida por las unidades de la también lograr reducir los efectos nocivos de los gases de escape al medio ambiente, para lograr lo dicho se realizó el proyecto de una estación de gas natural en dicha empresa. En la actualidad el gas natural tiene propiedades que lo convierten en un Combustible limpio de corrosión acida en superficies metálicas y refractarias, no genera producción de cenizas produciéndose una opción de regularizar "Comercio de Emisiones" promoviendo el "mecanismo para un desarrollo limpio", siendo económicamente rentable debido a su precio en el mercado nacional. Por tal razón, la empresa que realizo el diseño y la construcción fue "BUILMEP SAC", dándose inicio con la presentación de la documentación requerida por OSINERGMIN para la supervisión de la construcción y la acreditación del consumidor directo para su distribución oficial de gas natural.Trabajo de suficiencia profesiona

Cálculo de impedancia equivalente para la localización de fallas en sistemas transmisión HVDC mediante el control de conversores de potencia

Debido al avance de la tecnología en los componentes semiconductores y electrónica de potencia, los sistemas de transmisión HVDC son una alternativa confiable para los sistemas eléctricos. Al igual que los sistemas en AC, estos son propensos a fallas atmosféricas o una mala coordinación de protecciones, tanto la detección y localización de las mismas es de suma importancia para garantizar la continuidad en el transporte de energía. La investigación propone desarrollar un método para la localización de fallas en los sistemas de transmisión HVDC en base a la onda viajera con la obtención de voltajes y corrientes en las líneas afectadas a través de la simulación consiguiendo de esta manera una diferencia o fluctuación en el valor de la impedancia equivalente cuando la misma se encuentra en funcionamiento y cuando está en falla. La importancia de este método de detección de fallas en DC es no basarse en telecomunicaciones para redes HVDC. Adicionalmente el método propone la medición en caso de fallas de la corriente a tierra. Mediante la evaluación de estos tres factores se localizará la falla y se identificará el tipo de la misma. Para el modelado y la simulación se utilizó Simulink / MatLab.Due to the advancement of technology in semiconductor components and power electronics, HVDC transmission systems are a reliable alternative to electrical systems. Like AC systems, these are prone to atmospheric failures or poor coordination of protections, both the detection and location of them is of utmost importance to ensure continuity in the transport of energy. The research proposes to develop a method for locating faults in HVDC transmission systems based on the traveling wave with the obtaining of voltages and currents in the affected lines through simulation, thus achieving a difference or fluctuation in value of the equivalent impedance when it is in operation and when it is in failure. The importance of this method of detecting failures in DC is not to rely on telecommunications for HVDC networks. Additionally, the method proposes the measurement in case of ground current failures. By evaluating these three factors the fault will be located and its type will be identified. For modeling and simulation Simulink / MatLab was used

Volcanes del Ecuador

DESCRIPCION DE LOS VOLCANES DEL ECUADORDESCRIPCION DE LOS VOLCANES DEL ECUADO

Análisis de susceptibilidad por flujo de detritos en la zona de descarga de la quebrada San Carlos – Cañete – Lima – Perú

La presente investigación tiene como objeto principal evitar los problemas de pérdidas tanto en el ámbito social, económico y ambiental en la población de la Asociación de Vivienda Popular San Carlos Alto en épocas de avenidas y en casos excepcionales como el fenómeno del niño, como resultado de las inundaciones y huaycos, todo esto mediante un análisis de susceptibilidad adecuado para la zona en estudio. La investigación fue de tipo cuantitativo, teniendo como raíz a los problemas de pérdidas tanto en el ámbito social, económico y ambiental observado en los primeros meses del año por el fenómeno El Niño, el cual es común que genere precipitaciones extremas, trayendo como consecuencia inundaciones, desbordes y flujos de detritos. Este fue en el caso de San Carlos en enero del año 2015, sufriendo grandes estragos por ser la primera vez en los 40 años de existencia del sector que experimentaba este tipo de fenómeno, lo cual se simuló mediante el software suizo RAMMS Debris flow bajo los resultados obtenidos para un tiempo de retorno de 50 años debido a la baja probabilidad de ocurrencia del evento, usando como datos los resultados de los estudios geotécnicos propios realizados en puntos clave de la zona (como la huella de flujos de detritos de eventos anteriores), estudio hidrológico (con datos proporcionados por el SENAMHI) e imágenes pancromáticas y multiespectrales del satélite peruano PeruSat -1, el cual permitió la generación de la topografía mediante el procesamiento de 3 imágenes con distintos ángulos de toma brindadas por la CONIDA, dichos productos también sirvieron para la identificación y posterior mapeo geológico – geomorfológico de la zona, siendo contrastado y verificado con las visitas, también con el levantamiento de información mediante las plataforma SIGRID, GEOCATMIN, ASF DATA VERTEX, etc. Además, se calcularon los niveles de riesgo mediante la metodología Saaty, propuesta por el CENEPRED y la ley N°22664, realizando encuestas a los pobladores de la zona para conocer las condiciones actuales y su conocimiento acerca del riesgo al que están expuestos, del cual se obtiene que la asociación de vivienda popular San Carlos Alto tiene un total de 27 lotes en un riesgo medio y 79 bajo riesgo alto. Con el resultado de la simulación en RAMMS y la evaluación de riesgos (data demográfica) se pudieron proponer soluciones adecuadas para la zona de estudio, tanto medidas estructurales y no estructurales

Sliding-mode controller for a photovoltaic system based on a Cuk converter

The wide range of step-up and step-down input-output voltage characteristic of the Cuk converter makes it a good candidate to interface photovoltaic arrays in both classical and distributed maximum power point tracking systems. Because its two inductor structure, Cuk converters have continuous input and output currents, which reduce the additional filtering elements usually required for interfacing dc/dc converter topologies. However, PV systems based on Cuk converters usually do not provide formal proofs of global stability under realistic conditions, which makes impossible to ensure a safe operation of the PV installation. Therefore, this paper proposes a high performance sliding-mode controller for PV systems based on Cuk converters, which regulates the PV voltage in agreement with the commands imposed by a MPPT algorithm, rejecting both load and environmental perturbations, and ensuring global stability for real operation conditions. Finally, the performance of the regulated PV system is tested using both simulations and experiments