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El cambio climático se encuentra entre los factores de mayor interés a nivel mundial en los aspectos social y empresarial, la huella de carbono es un indicador que mide las emisiones de dióxido de carbono (CO2) que se realizan en la cadena de producción de bienes, desde la obtención de materias primas hasta el tratamiento de desperdicios. La huella ecológica es una medida real del impacto provocado por las actividades del ser humano en el medio ambiente y se determina según la cantidad de gases de efecto invernadero producidos. La propuesta es medir la huella ecológica de manera completa con la finalidad de considerar al carbono como la base y no únicamente al CO2, como es utilizado en las herramientas descritas. La presente investigación trabaja sobre el contexto internacional y metodologías para la medición del carbono, asimismo se efectúa un análisis comparativo entre la huella de carbono y la huella ecológica, sus alcances y diferencias, al igual que ilustrar su aplicación en la industria farmacéutica.

In general, family farming in Latin America is a precarious endeavor. The objective of this work was to recognize the business management elements of human, material and economic resources required by a peasant economy located in the Municipality of Tepotzotlan, State of Mexico in order to proceed with the necessary training that would allow it to move to an economy in transition and achieve the formation of an agricultural family microenterprise. The case study method was used, information obtained through structured interviews and direct observation was analyzed. The results show a peasant economy of self-consumption farming, limited economic resources, and low profits. There is also little knowledge to run an agricultural business, which causes the lack of sufficient permanent income to support a family, limiting the improvement in the living conditions of its members. We see the existence of sub-communities or “guilds” made up of family members, neighbors, and friends who establish solid relations of exchange of goods and services based more on trust than economic payment and who have little interaction with other members of the community. With this basis, strategies to improve the management of their resources are proposed as well as the topics to be considered in the future to carry out the internal training- professionalization of the rural family business.

"Innovación y gobernanza para el desarrollo sustentable en México" contribuye a los temas de la industria inteligente y tecnologías emergentes, transformaciones sociales y sustentables. En nuestra visión, el desarrollo sustentable de las sociedades se basa de manera crucial en la evaluación y mejora de la interacción entre los recursos naturales, sociales y técnicos. El desafío del desarrollo sustentable sólo puede ser manejado por su coevolución productiva. El presente libro busca investigar cómo dichos procesos pueden ser apoyados por enfoques de gobernanza, basados en una comprensión más profunda de cómo y cuándo ocurren las innovaciones sustentables y pueden conducir a las llamadas “transiciones”. En particular, el libro se centra en la investigación fundamental y aplicada sobre la gobernanza, la dinámica institucional y de gestión de los recursos naturales, sociales y técnicos, así como su interacción. Dentro de esta complejidad, nuestra investigación propone una relación estrecha con los Objetivos de Desarrollo Sostenible de la Agenda 2030 de las Naciones Unidas.

The creation of an emissions trading system in Mexico as response to international policy on climate change forces the government and corporations to create new activities and responsibilities to address this issue. It is also important to know who will be the decision-maker and who is in charge of the institutional work (representation and negotiation). The main objective of this chapter is to point out who the stakeholders involved in the design, implementation, evaluation and transparency of the system are, or should be, according to the national regulatory framework and international summons. We shall also analyze the mechanics and information provided by the system and how it helps to make environmental policy, which helps to reduce emissions. Finally, we will also analyze whether it also helps to establish strategic alliances and international agreements toward common objectives and priorities. The chapter approaches the topic based on capacity development theory, which focuses on improving governance among different levels and stakeholders: government, companies, civil organizations, and scientists. We emphasize the potential of training spaces as a place for transformation and developing a learning framework whose own relevance relies on the focus of emergent strategies, which ensure the environmental integrity and conditions for the country’s competence in the international context. This chapter contributes to existing literature about the understanding of executing such a system, the stakeholders involved at the national level, and their potential to create international networks.

By designing a robust control, for the first time in literature, the tracking task associated with the MIMO DC/DC Boost converter–inverter–DC motor system is solved. Such robustness is achieved through the exploitation of the differential flatness property related to the system and by a suitable design of auxiliary controls. With the aim of verifying the performance of the robust control, a platform of the system along with MATLAB-Simulink and a DS1104 board are used. The experimental results show the good performance of the system in closed-loop even when electrical abrupt changes are considered in some parameters of the Boost converter and when a mechanical load perturbation is applied.

Apoyar la continuidad de la empresa familiar rural, a través de estrategias empresariales, requiere entender las características de su contexto agrícola. Por lo que, el objetivo de este trabajo es proponer una categorización de la agricultura familiar para identificar su perfil y poder valorar su potencial y limitaciones de desarrollo en la pequeña empresa familiar. La metodología utilizada es del tipo descriptivo cualitativo, a través del trabajo de campo en la comunidad rural de San Antonio Portezuelo, en el estado de Puebla, México; se aplica el método de análisis para la categorización de la agricultura familiar, la cual es definida por siete variables: destino de la producción, conformación de la agricultura familiar (participación familiar), número de hectáreas, infraestructura, diversificación de actividades, cobertura de mercado y ciclo productivo. Los resultados proporcionan información a nivel local de un país en desarrollo, como México. Asimismo, permiten tener una plataforma para reconocer a la agricultura de subsistencia y en transición, y a partir de esto, plantear las bases para diseñar programas de intervención empresarial que ayuden a convertir el potencial de la pequeña empresa familiar en resultados reales.

This paper presents a proposal of the theoretical and contextual foundation of a human techno structural model (HTSM) of managerial competencies of dry cargo auto transportation (DPCAT) in Mexico. Firstly, the conceptualization of state of the art is shown through the analysis of the theoretical framework concerning management skills models and, as a second element, an analysis of the contextual framework of applied management skills certification models was shown currently in the DPCAT sector to integrate them into the decision making the process of managers in the metropolitan area of the state of Hidalgo, in 2016. This also shows the results obtained from the application of a questionnaire that relates the managerial competencies with the expected performances and the results of this, which was the base the techno structural approach and its relation to the individual needs of the manager, giving rise to a standardization proposal based on Leadership, Diagnostics of competencies, Installation of competencies, Development of competencies and Enhancement of competencies. This development establishes that personal changes (directive) and interference in group changes are accompanied by a cognitive and experiential process that ensures the self-sustaining of HTSM in the organization.

El propósito de este libro es estudiar y analizar la manera como se han desarrollado y fortalecido las capacidades y acciones, tanto sociales como institucionales, para el manejo de los problemas públicos de carácter social, económico y político. Es importante valorar si los gobiernos en sus diferentes ámbitos —locales, estatales o federal— cuentan con la capacidad para ejecutar políticas dedicadas a la solución de estos desafíos públicos. La construcción de capacidades se propone promover un “buen gobierno” y alcanzar un desarrollo sostenible a través de individuos, grupos, organizaciones, instituciones y sociedades que busquen mejorar sus habilidades para desempeñar funciones, resolver problemas, alcanzar objetivos, entre otras más actividades. Los artículos que se presentan abordan el tema desde lo teórico, lo social, político y económico en casos generales y específicos. Consideramos que éste es un tema que México requiere trabajar para llegar a ser resiliente ante las amenazas de los contextos internacionales y nacionales.

This paper is concerned with path-tracking control of a wheeled mobile robot. This robot is equipped with two permanent magnet brushed DC-motors which are fed by two inverter-DC/DC Buck power converter systems as power amplifiers. By taking into account the dynamics of all the subsystems we present, for the first time, a formal stability proof for this control problem. Our control scheme is simple, in the sense that it is composed by four internal classical proportional-integral loops and one external classical proportional-derivative loop for path-tracking purposes. This is the third paper of a series of papers devoted to control different nonlinear systems, which proves that the proposed methodology is a rather general approach for controlling electromechanical systems when actuated by power electronic converters.

Introducción: Las empresas familiares (EF), aportan significativamente a la economía y a la sociedad en muchos países. El estudio de la profesionalización de estas empresas resulta relevante, toda vez que permite alcanzar una gestión eficiente dentro de la organización y para aumentar ganancias. Esta investigación tiene como objetivo describir y analizar la evolución cuantitativa de la producción científica de la profesionalización en la EF familiar desde 1980 a 2019, lo cual, permite identificar aspectos claves como son el autor más citado, la revista de mayor impacto, la institución líder, a fin de analizar las principales características del tema y perfilar futuras líneas de investigación.Método: Los datos se obtuvieron de los artículos recuperados del portal Web of Science, de Clarivate Analytics y se llevó a cabo un método bibliométrico y análisis de contenido.Resultados: La búsqueda produjo 112 artículos, con picos de producción en 2013 y 2018. Se analizan las redes de coocurrencia, citación y coautoría. La revista “Family Business Review” es la de mayor publicación de artículos; no obstante, el “Journal of Finance” y “Quarterly Journal of Economics” tienen un factor de impacto mayor. Anderson y Reeb son los autores más citados. Estados Unidos concentran la mayor producción científica y la participación de América Latina y, en específico México, es casi nula.Discusión y Conclusión: El tema de profesionalización comenzó a ser estudiado como un factor implícito y de soporte para el crecimiento de la empresa familiar. En los últimos nueve años, aumentaron las publicaciones sobre la profesionalización ya que incide en la obtención de ganancias económicas, además, está en la base de la sucesión e institucionalización de la organización e interviene en la continuidad de la empresa y la armonía familiar. La mayoría de las investigaciones se enfocan en evaluar los resultados financieros comparando entre un CEO familiar o uno externo. Sin embargo, falta profundizar en el estudio de cómo realizar la planeación, ejecución y evaluación de la profesionalización. Las diferencias en la gestión aplicable a empresas familiares grandes, las microempresas, pequeños emprendimientos, y sus componentes culturales, son temas amplios que requieren más investigación. A nivel internacional sigue en debate el perfil de la persona para manejar eficientemente la EF, lo cual abre la oportunidad para investigar estos temas en el contexto mexicano.

Introducción: La pobreza perjudica a las personas al limitarles la posibilidad de cubrir sus necesidades básicas, y en la mayoría de las ocasiones el acceso a los sistemas formales de financiamiento. Esta situación lleva a que las personas se organicen en estructuras de autoayuda comunitaria para poder acceder a servicios de ahorro y crédito. En aras de comprender las dinámicas de operación de estas estructuras de autoayuda, esta investigación permite conocer a detalle la operatividad de una caja de ahorro informal, los beneficios económicos que se generan al interior de sus participantes y sus similitudes con los datos de la Encuesta Nacional de Inclusión Financiera (ENIG) del año 2015.Método: Estudio descriptivo con un método cualitativo de estudio de caso. El trabajo de campo se llevó in situ por 50 semanas. Análisis de documentos y registros internos, aplicación de entrevistas, cuestionarios y observación directa.Resultados: El 50% de los integrantes de la Caja de Ahorro Informal utilizan el dinero para el pago de deudas versus el 33% del nivel nacional. Las mujeres son quienes utilizan sus ahorros y ganancias para aumentar su masa de rendimiento a través de la inversión o creación de micronegocios. Las personas que obtuvieron una mayor tasa pasiva fueron del 32% y la menor del 21%. Entre los 22 miembros de la CAI se obtuvo un ahorro de $160,100.00 con un monto de préstamos de $255,500.00.Discusión o Conclusión: La demanda de servicios financieros de la población de bajos ingresos no atendida por la banca comercial propicia el surgimiento de entidades al margen de las estructuras formales del mercado financiero. Estos sistemas informales ofrecen servicios flexibles de ahorro y crédito acorde a las necesidades y expectativas de sus integrantes.

Esta obra se compone de ocho ensayos realizados por investigadores de varios centros de investigación del Instituto Politécnico Nacional y de la Universidad Autónoma de Baja California, cuya inquietud principal es indagar sobre las problemáticas en las que las acciones del Estado son importantes para su mejora o solución. Por esta razón, el gasto público es uno de los puntos más abordados a lo largo del libro en sus diversos aspectos: desde su efecto en la formación de capital para el crecimiento económico, pasando por el involucramiento ciudadano en su distribución a partir de determinadas necesidades sociales, hasta la inversión pública como parte de ese gasto público. Otro de los graves problemas a tratar es la cuestión de las pensiones, de ahí que se analice el riesgo, la volatilidad y el rendimiento de los mercados financieros que tienen las afores. En este sentido, se hacen propuestas para disminuir o, en su caso, resolver los problemas que este tema acarrea. De igual forma, como no podemos ser ajenos a lo que vive el país, se abordan las repercusiones que ha tenido la Covid-19 en el aumento del desempleo y en el incremento de la economía informal.

The implementation of a hierarchical controller for the trajectory tracking control of a wheeled mobile robot (WMR) is presented in this work. The experimental development of such a controller is performed with the low-cost embedded hardware Jetson TK1 from NVIDIA. In the programming of the controller, free license software with short learning curve is used. To validate the performance of the embedded hardware, a comparison between the results obtained from the WMR in closed-loop is presented when using: a) the embedded hardware Jetson TK1 and b) the fast prototyping DS1104 board from dSPACE. The experimental results show that the Jetson TK1 board could be suitable for the control of autonomous mechatronic systems.

This paper presents a passivity-based control for the DC/DC Buck-Boost converter–inverter–DC motor system. Such control exploits the energy structure associated with the system error dynamics. This in order to solve the trajectory tracking task for both the converter voltage and motor bidirectional angular velocity, without using electromechanical sensors. The successful experimental validation of the proposed control is performed in a built prototype of the system, using Matlab-Simulink and a DS1104 board.

A mathematical model of a new &ldquo, full-bridge Buck inverter&ndash, DC motor&rdquo, system is developed and experimentally validated. First, using circuit theory and the mathematical model of a DC motor, the dynamic behavior of the system under study is deduced. Later, the steady-state, stability, controllability, and flatness properties of the deduced model are described. The flatness property, associated with the mathematical model, is then exploited so that all system variables and the input can be differentially parameterized in terms of the flat output, which is determined by the angular velocity. Then, when a desired trajectory is proposed for the flat output, the input signal is calculated offline and is introduced into the system. In consequence, the validation of the mathematical model for constant and time-varying duty cycles is possible. Such a validation of this mathematical model is tackled from two directions: (1) by circuit simulation through the SimPowerSystems toolbox of Matlab-Simulink and (2) via a prototype of the system built by using Matlab-Simulink and a DS1104 board. The good similarities between the circuit simulation and the experimental results allow satisfactorily validating the mathematical model.

In this paper, a proposal for trajectory generation especially well-suited for wheeled mobile robots (WMRs) is presented. In this proposal (PVLAVPB) linear and angular velocities of the WMR are specified as Bezier polynomials. The PVLAVPB is able to generate smooth complex shapes, which would involve more complicated mathematical algorithms if other trajectory generation methods were used. Also, this proposal helps to avoid slipping and skidding of the WMR, since smooth starting and braking can be achieved proposing suitable linear and angular velocities. The generated trajectory is introduced in a hierarchical controller that solves the trajectory tracking task in a differential drive WMR. The experimental validation of the PVLAVPB is carried out via Matlab-Simulink along with a DS1104 board, obtaining satisfactory results.

In this work a three-level controller that carries out the trajectory tracking task for a differential drive wheeled mobile robot (WMR) is presented. Such a controller considers, for the first time in literature, the dynamics associated with the three subsystems that compose a WMR, i.e., mechanical structure, actuators, and power stage. The high level corresponds to an input-output linearization control for the mechanical structure; the medium level is based on two sensorless controls designed via differential flatness for the actuators; and the low level is related to two cascade controls based on sliding modes and PI control for the power stage. The performance and robustness of the controller is verified and shown via realistic simulations when parametric uncertainties associated with the subsystems that compose the WMR are considered.

El enfoque de los ecosistemas empresariales (EE) puede ser una alternativa sostenible de las actividades económicas. El objetivo fue desarrollar un estudio bibliométrico sobre EE a partir de la Web of Science. Se encontraron 272 documentos publicados entre 1991 y mayo 2019, con picos de producción en 2007 y 2017. Se construyeron las redes temáticas, registros y productividad por fuentes, países, instituciones, palabra clave, h-index, co-autoría y co-citas. Se encontraron 587 autores, de 53 países. Las revistas más productivas tienen altos niveles de impacto. China produce el mayor número de publicaciones, pero Estados Unidos y Reino Unido tienen el mayor número de citas. Innovación y estrategia son temas relacionados con EE. Aunque existen diferentes perspectivas y la base conceptual de los EE está todavía en discusión, algunos países orientales ya están en la implementación. Los EE tienen un alto potencial de aplicación para el desarrollo sostenible a gran escala.

By using the hierarchical controller approach, a new solution for the control problem related to trajectory tracking in a differential drive wheeled mobile robot (DDWMR) is presented in this paper. For this aim, the dynamics of the three subsystems composing a DDWMR, i.e., the mechanical structure (differential drive type), the actuators (DC motors), and the power stage (DC/DC Buck power converters), are taken into account. The proposed hierarchical switched controller has three levels: the high level corresponds to a kinematic control for the mechanical structure, the medium level includes two controls based on differential flatness for the actuators, and the low level is linked to two cascade switched controls based on sliding modes and PI control for the power stage. The hierarchical switched controller was experimentally implemented on a DDWMR prototype via MATLAB-Simulink along with a DS1104 board. With the intention of assessing the performance of the switched controller, experimental results associated with a hierarchical average controller recently reported in literature are also presented here. The experimental results show the robustness of both controllers when parametric uncertainties are applied. However, the performance achieved with the switched controller introduced in the present paper is better than, or at least similar to, performance achieved with the average controller reported in literature.

Two alternative mathematical models for the DC/DC Boost converter are presented. The development of the alternative models uses both the energy and the traditional model of the Boost converter. The similarity between the results obtained from the numerical and circuit simulations in Matlab-Simulink for time-varying duty cycles verifies the developed models.

This paper solves the voltage tracking of the DC/DC Buck-Boost power electronic converter via a robust direct control. The control design is based on an alternative model of the Buck-Boost converter and contains only voltage terms, thus achieving direct manipulation. The control performance is verified on a converter circuit built in the SimPowerSystem toolbox of Matlab-Simulink. The results show a good voltage tracking against parametric disturbances, as well as the viability of the experimental implementation of the control in a prototype.

This paper has two aims. The first is to develop a robust hierarchical tracking controller for the DC/DC Buck-Boost&ndash, inverter&ndash, DC motor system. This controller considers a high level control for the inverter&ndash, DC motor subsystems and a low level control for the DC/DC Buck-Boost converter subsystem. Such controls solve the tracking task associated with the angular velocity of the motor shaft and the output voltage of the converter, respectively, via the differential flatness approach. The second aim is to present a comparison of the robust hierarchical controller to a passive controller. This, with the purpose of showing that performance achieved with the hierarchical controller proposed in this paper, is better than the one achieved with the passive controller. Both controllers are experimentally implemented on a prototype of the DC/DC Buck-Boost&ndash, DC motor system by using Matlab-Simulink along with the DS1104 board from dSPACE. According to experimental results, the proposal in the present paper achieves a better performance than the passive controller.

Two differential flatness-based bidirectional tracking robust controls for a DC/DC Buck converter-DC motor system are designed. To achieve such a bidirectional tracking, an inverter is used in the system. First control considers the complete dynamics of the system, that is, it considers the DC/DC Buck converter-inverter-DC motor connection as a whole. Whereas the second separates the dynamics of the Buck converter from the one of the inverter-DC motor, so that a hierarchical controller is generated. The experimental implementation of both controls is performed via MATLAB-Simulink and a DS1104 board in a built prototype of the DC/DC Buck converter-inverter-DC motor connection. Controls show a good performance even when system parameters are subjected to abrupt uncertainties. Thus, robustness of such controls is verified.

The aim of this study is to show the design of an instrument that contextualises the intention to leave (IL) in terms of spaces and job content (SJC), the perceived supervisor support (PSS), the perceived peer support (PPS), the organisational extrinsic motivation (OEM), the available opportunities outside the organisation (AO) and family–work conflict (FWC) as a tool to make diagnostic evaluations of Mexican hotel companies. The method used for the design of this instrument included literature review, establishment of dimensions and items and items validation. The reliability of the instrument was evaluated through the technique of split halves, and eventually it was calculated using Cronbach’s alpha coefficient in the different components of the instrument, as an indicator of internal consistency. The correlation coefficients obtained were acceptable in 38 of the 40 and significant at 0.01 level with only two at the 0.05 level. The tool proved to be reliable as a whole and in all dimensions in the first scan. Thus, the results revealed that this instrument measures the following: the causal dimensions, intention to leave and its variables.

In this paper, alternative mathematical models for the DC/DC Buck-Boost converter are developed. In order to obtain the alternative models, the differential flatness property of the converter is exploited. The validation of such models is carried out via the comparison of simulations of the model commonly employed versus the ones of the herein presented alternative models and the circuit of the converter. The simulations show that the dynamic evolution of the proposed alternative models is very similar to that of the commonly employed model for the Buck-Boost converter.

In this paper, via a passive control, the regulation task of the DC/DC Buck-Boost converterinverterDC motor system is solved. Such a control, on the one hand, takes advantage of the energetic structure associated with the error dynamics of the system. On the other hand, it does not require the use of electromechanical sensors to control the angular velocity of the motor. The control performance is verified through numerical simulations, with Matlab-Simulink, in two directions: i) The control is introduced in the mathematical model associated with the system under study. ii) The control, implemented via PWM, is introduced in the corresponding electronic circuit. The results of simulation in closed-loop, in average, show much similarity to each other; which shows the viability of the control for its experimental implementation.

The modeling and simulation of the “full-bridge Buck inverterDC motor” system, is presented for the first time in this paper. The converter used in this arrangement allows a smooth start and bidirectional motion at the shaft of the DC motor. The Kirchhoff's laws and the DC motor model are used to obtain the mathematical model of the system. With the intention of validating the model of the system under study, the simulation results of the mathematical model are compared versus the ones of the corresponding electrical circuit. Both simulations are performed with Matlab-Simulink. The similar behavior between both results allow validating the mathematical model herein proposed.

The start up of a differential wheeled mobile robot is presented here via the use of embedded hardware with free software. The main function of such an embedded hardware is the data acquisition and processing. To this end, predetermined programs of the embedded hardware along with new ones also designed with free software are employed. With the above, in the future, a robot that allows the implementation of control strategies, in a quickly and easy way, using low cost hardware and software is intended to obtain. The operation of the robot with the embedded hardware is experimentally verified, obtaining satisfactory results. Since, the experiments are, in general, similar to the results obtained in simulation.

Desde finales de la década de 1950 aparecen movimientos de la sociedad civil y la academia que han cuestionado el modelo de industrialización y desarrollo. En el área de los negocios se observa una incorporación cada vez mayor de elementos de Desarrollo Sustentable. En este trabajo se siguió el método de estudio de caso; a partir de un proceso de incorporación con las familias de los productores rurales se buscó detectar sus necesidades y conocer la forma en la que impactan sus actividades en los aspectos económicos, sociales y ambientales. Con esta base, y considerando el contexto local, se identifican las bases teóricas y prácticas para proponer un modelo de gestión sustentable adecuado a las unidades familiares rurales. El modelo incorpora buenas prácticas, así como herramientas y estrategias viables. La implementación del desarrollo sustentable puede implicar cambios significativos en las estructuras mentales establecidas, principalmente en el nivel de los pequeños productores y del consumidor final.

This paper presents a two-stage control design for the “Buck power converter/DC motor” system, which allows to perform the sensorless angular velocity trajectory tracking task. The differential flatness property of the DC-motor model is exploited in order to propose a first-stage controller, which is designed to achieve the desired angular velocity trajectory. This controller provides the voltage profiles that must be tracked by the Buck converter. Then, a second-stage controller is meant to assure the aforementioned. This controller is based on flatness property of the Buck power converter model, which provides the input voltage to the DC motor. Due to the fact that the two-stage controller proposed uses the average model of the system, as a practical and effective implementation of this controller, aΣ − Δ-modulator is employed. Finally, in order to verify the control performance of this approach, numerical simulations are included.

This paper presents for the first time, the modeling and simulation of a bidirectional DC/DC Buck-Boost converter-DC motor system. This configuration allows the motor shaft to rotate in both directions. The mathematical model is obtained by applying the Kirchhoff's laws in each of the operating modes of the system, whereas the simulation results are obtained using Matlab-Simulink. The results show the validation of the mathematical model of the system under study.

This work presents the design of a wheeled mobile robot (WMR) using an Ackerman configuration. Its design uses the extruded aluminum profile widely used in industry, facilitating the assembly of new robotics projects. The design is carried out using CAD software and shows some of the various benefits of these tools. The environmental impact values for a bar of extruded aluminum profile throughout its lifecycle was calculated and, later, analyzed by using SolidWorks simulationXpress study to improve the sustainability of the WMR design. Additionally, images of both the 3D model and the real prototype are presented.

Robotics is a fast developing and exciting field with multiple applications which span from robot manipulators to mobile robots. This paper presents a literature review on wheeled mobile robots. We point out the main considerations to be taken into account when designing this class of robots. The main control problems are recalled as well as the corresponding solutions. Finally, we summarize the most important approaches used to render mobile robots autonomous.

We introduce a dc/dc boost power converter as a didactic prototype intended to support courses on electric circuit analysis experimentally. The corresponding mathematical model is obtained, the converter is designed and an experimental setup is described, constructed and tested. Simplicity of construction as well as low cost of components renders the feasible introduction of this equipment in undergraduate laboratories.

Desde 1995 la industria textil y del vestido ha presentado decrementos en la rentabilidad que reportaron sus empresas, las cuales no se recuperaron para el periodo de 2001 a 2005, siendo las del subsector de textil y confección las únicas que lograron una rentabilidad que no representó ni el 3%. Ante tales resultados, se buscó verificar si lo establecido en las últimas investigaciones que señalan que los factores propios de las empresas son los que en mayor medida generan y sustentan la rentabilidad de las empresas y, por lo tanto, tal situación corresponde a lo que sucede en las empresas del sector textil en México, o bien se debe a las políticas o acciones que realiza o deja de hacer el gobierno en un sector específico. Para ello, se realizó un estudio correlacional a través de un método deductivo de la rentabilidad reportada por las empresas representantes de la industria textil y de los años en que se obtuvieron los resultados. Se confirmó lo establecido por otras investigaciones en cuanto a que la rentabilidad es generada y sustentada por los factores propios de las empresas y posteriormente por las condiciones externas en las cuales operan.

The aim of this work is threefold: first we obtain analytical expressions for the wavefront train and the caustic associated with the refraction of a plane wavefront by an axicon lens, second we describe the structure of the ronchigram when the ronchiruling is placed at the flat surface of the axicon and the screen is placed at different relative positions to the caustic region, and third we describe in detail the structure of the null ronchigrating for this system; that is, we obtain the grating such that when it is placed at the flat surface of the axicon its associated pattern, at a given plane perpendicular to the optical axis, is a set of parallel fringes. We find that the caustic has only one branch, which is a segment of a line along the optical axis; the ronchigram exhibits self-intersecting fringes when the screen is placed at the caustic region, and the null ronchigrating exhibits closed loop rulings if we want to obtain its associated pattern at the caustic region.

Sliding mode control is a discontinuous control technique that is, by its nature, appropriate for controlling variable structure systems, such as the switch regulated systems employed in power electronics. However, when designing control laws based on the average models of these systems a modulator is necessary for their experimental implementation. Among the most widely used modulators in power electronics are the pulse width modulation (PWM) and, more recently, the sigma-delta-modulator (Σ-Δ-modulator). Based on the importance of achieving an appropriate implementation of average control laws and the relevance of the trajectory tracking task in DC/DC power converters, for the first time, this research presents the assessment of the experimental results obtained when one of these controllers is implemented through either a PWM or aΣ-Δ-modulator to perform such a task. A comparative assessment based on the integral square error (ISE) index shows that, at frequencies with similar efficiency, theΣ-Δ-modulator provides a better tracking performance for the DC/DC Buck converter. In this paper, an average control based on differential flatness was used to perform the experiments. It is worth mentioning that a different trajectory tracking controller could have been selected for this research.

This paper reports a solution for trajectory tracking control of a differential drive wheeled mobile robot (WMR) based on a hierarchical approach. The general design and construction of the WMR are described. The hierarchical controller proposed has two components: a high-level control and a low-level control. The high-level control law is based on an input-output linearization scheme for the robot kinematic model, which provides the desired angular velocity profiles that the WMR has to track in order to achieve the desired position(x*,y*)and orientation(φ*). Then, a low-level control law, based on a proportional integral (PI) approach, is designed to control the velocity of the WMR wheels to ensure those tracking features. Regarding the trajectories, this paper provides the solution or the following cases: (1) time-varying parametric trajectories such as straight lines and parabolas and (2) smooth curves fitted by cubic splines which are generated by the desired data pointsx1*,y1*,…,xn*,yn*. A straightforward algorithm is developed for constructing the cubic splines. Finally, this paper includes an experimental validation of the proposed technique by employing a DS1104 dSPACE electronic board along with MATLAB/Simulink software.