Creating auto-grading exercises with MATLAB Grader for automatic control courses

[Resumen] Recientemente, el desarrollo de recursos interactivos está recibiendo gran atención en titulaciones de ingeniería para apoyar la enseñanza, especialmente tras la pandemia derivada por el coronavirus. Entre estos recursos, los que tienen la capacidad de corrección y/o calificación automática son los preferidos tanto por los estudiantes como el profesorado. Asimismo, la implementación de una evaluación formativa eficaz es uno de los principales retos de los docentes para mejorar realmente el proceso de enseñanza aprendizaje. Este trabajo presenta un ejemplo de aplicación de MATLAB® Grader , una herramienta de autor basada en web que permite a los instructores proporcionar una evaluación automática de diferentes tipos de problemas de ingeniería, no solo los clásicos ejercicios de programación, y, en consecuencia, informar a los estudiantes sobre su rendimiento de una manera rápida y eficaz. En concreto, se presentan una serie de problemas de diseño clásicos de control automático con fines ilustrativos.[Abstract] Recently, the development of interactive resources is receiving great attention in engineering degrees to support teaching, especially after coronavirus pandemic. Among such resources, those that have the ability of automatic correction and/or grading are preferred for both students and faculty. Likewise, the implementation of an e ective formative assessment is one of the main challenges for academy in order to actually improve the teaching-learning process. This paper presents an example of application of MATLAB® Grader , a web-based authoring tool that allows instructors to provide automatic evaluation of di erent kinds of engineering problems, not only classic coding exercises, and, consequently, inform students about their performance in a quick and e ective manner. Specifically, a series of classical design problems of automatic control are given for illustrative purposes

Digital twins of rotary motion and cart-pendulum platforms for education in automatic control

[Abstract] Modern educational systems, similarly to Industry 4.0, are focusing their efforts to the development of new digital resources that allow to understand, simulate, predict, and optimize real systems through virtual replicas. In this sense, digital twins (DTs), which are high-fidelity virtual or digital representations of a physical product or process, are turning into a disruptive trend in the education sector and its influence is expected to be significant on future of many degrees, especially in engineering. This paper presents the DTs of three educational platforms which are widely used in automatic control for educative purposes: rotary motion equipment developed by Quanser, and a cart-pendulum platform developed by Feedback Instruments. The DTs have been built in the MATLAB®/Simulink© environment thanks to the physical modeling toolbox SimscapeTM through blocks contained in its libraries rather than using mathematical models. A set of possible control exercises that can be performed by students of automatic control courses are proposed, which are supported by the use of these educative resources.Junta de Extremadura; GR2116

Modeling of the human vestibular system and integration in a simulator for the study of orientation and balance control

[Abstract] Biologically, the vestibular feedback is critical to the ability of human body to balance in different conditions. This paper presents a human-inspired orientation and balance control of a three degree- of-freedom (DOF) simulator that emulates a person sitting in a platform. In accordance with the role in humans, the control is essentially based on the vestibular system (VS), which regulates and stabilizes gaze during head motion, by means of modeling the behavior of the semicircular canals and otoliths in the presence of stimuli, i.e., linear and angular accelerations/velocities derived by the turns experienced by the robot head on the three Cartesian axes. The semicircular canal is used as the angular velocity sensor to perform the postural control of the robot. Simulation results in the MATLAB/Simulink environment are given to show that the orientation of the head in space (roll, pitch and yaw) can be successfully controlled by a proportional-integral-derivative (PID) with noise filter for each DOF.[Resumen] Biológicamente, la retroalimentación vestibular es crítica para la capacidad del cuerpo humano para equilibrarse en diferentes condiciones. Este artículo presenta una orientación inspirada por el hombre y el control de equilibrio de un simulador de tres grados de libertad (DOF) que emula a una persona sentada en una plataforma. De acuerdo con el papel en los humanos, el control se basa esencialmente en el sistema vestibular (VS), que regula y estabiliza la mirada durante el movimiento de la cabeza, mediante el modelado del comportamiento de los canales semicirculares y los otolitos en presencia de estímulos, es decir, aceleraciones / velocidades lineales y angulares derivadas de los giros experimentados por la cabeza del robot en los tres ejes cartesianos. El canal semicircular se utiliza como sensor de velocidad angular para realizar el control postural del robot. Los resultados de la simulación en el entorno de MATLAB / Simulink se proporcionan para mostrar que la orientación de la cabeza en el espacio (balanceo, inclinación y guiñada) se puede controlar con éxito mediante un derivado proporcional-integral (PID) con filtro de ruido para cada DOF

Introducción al movimiento en el robot nadador tipo Purcell de tres segmentos

En este trabajo se han introducido los principales inconvenientes de trabajar en el entorno microscópico, en el régimen de bajo número de Reynolds (Re), así como se ha estudiado la dinámica de un robot nadador tipo Purcell de tres segmentos implementando dos primitivas de movimiento: cuadrada y circular. A partir de la teoría de fuerza resistiva (RFT) se ha obtenido la ecuación que rige el desplazamiento del robot en estas condiciones, y se han comparado ambas primitivas en cuanto al desplazamiento que aportan al robot.In this work, the main drawbacks of working in the microscopic environment, in the low Reynolds number (Re) regime, have been introduced, and the dynamics of a three-segment Purcell-type swimming robot has been studied by implementing two motion primitives: square and circular. From the resistive force theory (RFT), the equation governing the robot's displacement under these conditions has been obtained, and both primitives have been compared in terms of the displacement they provide to the robot

Purcell’s Three-Link Swimmer: Assessment of Geometry and Gaits for Optimal Displacement and Efficiency

This paper studies the displacement and efficiency of a Purcell’s three-link microswimmer in low Reynolds number regime, capable of moving by the implementation of a motion primitive or gait. An optimization is accomplished attending to the geometry of the swimmer and the motion primitives, considering the shape of the gait and its amplitude. The objective is to find the geometry of the swimmer, amplitude and shape of the gaits which make optimal the displacement and efficiency, in both an individual way and combined (the last case will be referred to as multiobjective optimization). Three traditional gaits are compared with two primitives proposed by the authors and other three gaits recently defined in the literature. Results demonstrate that the highest displacement is obtained by the Tam and Hosoi optimal velocity gait, which also achieves the best efficiency in terms of energy consumption. The rectilinear and Tam and Hosoi optimal efficiency gaits are the second optimum primitives. Regarding the multiobjective optimization and considering the two criteria with the same weight, the optimum gaits turn out to be the rectilinear and Tam and Hosoi optimal efficiency gaits. Thus, the conclusions of this study can help designers to select, on the one hand, the best swimmer geometry for a desired motion primitive and, on the other, the optimal method of motion for trajectory tracking for such a kind of Purcell’s swimmers depending on the desired control objective

Back to Basics: Meaning of the Parameters of Fractional Order PID Controllers

The beauty of the proportional-integral-derivative (PID) algorithm for feedback control is its simplicity and efficiency. Those are the main reasons why PID controller is the most common form of feedback. PID combines the three natural ways of taking into account the error: the actual (proportional), the accumulated (integral), and the predicted (derivative) values; the three gains depend on the magnitude of the error, the time required to eliminate the accumulated error, and the prediction horizon of the error. This paper explores the new meaning of integral and derivative actions, and gains, derived by the consideration of non-integer integration and differentiation orders, i.e., for fractional order PID controllers. The integral term responds with selective memory to the error because of its non-integer order λ , and corresponds to the area of the projection of the error curve onto a plane (it is not the classical area under the error curve). Moreover, for a fractional proportional-integral (PI) controller scheme with automatic reset, both the velocity and the shape of reset can be modified with λ . For its part, the derivative action refers to the predicted future values of the error, but based on different prediction horizons (actually, linear and non-linear extrapolations) depending on the value of the differentiation order, μ . Likewise, in case of a proportional-derivative (PD) structure with a noise filter, the value of μ allows different filtering effects on the error signal to be attained. Similarities and differences between classical and fractional PIDs, as well as illustrative control examples, are given for a best understanding of new possibilities of control with the latter. Examples are given for illustration purposes

Modeling and Control of IPMC-Based Artificial Eukaryotic Flagellum Swimming Robot: Distributed Actuation

Ionic polymer-metal composites (IPMCs) are electrically driven materials that undergo bending deformations in the presence of relatively low external voltages, exhibiting a great potential as actuators in applications in soft robotics, microrobotics, and bioengineering, among others. This paper presents an artificial eukaryotic flagellum (AEF) swimming robot made up of IPMC segments for the study of planar wave generation for robot propulsion by single and distributed actuation, i.e., considering the first flagellum link as an actuator or all of them, respectively. The robot comprises three independent and electrically isolated actuators, manufactured over the same 10 mm long IPMC sheet. For control purposes, a dynamic model of the robot is firstly obtained through its frequency response, acquired by experimentally measuring the flagellum tip deflection thanks to an optical laser meter. In particular, two structures are considered for such a model, consisting of a non-integer order integrator in series with a resonant system of both non-integer and integer order. Secondly, the identified models are analyzed and it is concluded that the tip displacement of each actuator or any IPMC point is characterized by the same dynamics, which remains unchanged through the link with mere variations of the gain for low-frequency applications. Based on these results, a controller robust to gain variations is tuned to control link deflection regardless of link length and enabling the implementation of a distributed actuation with the same controller design. Finally, the deflection of each link is analyzed to determine whether an AEF swimming robot based on IPMC is capable of generating a planar wave motion by distributed actuation

Modeling and Control of IPMC-Based Artificial Eukaryotic Flagellum Swimming Robot: Distributed Actuation

Ionic polymer-metal composites (IPMCs) are electrically driven materials that undergo bending deformations in the presence of relatively low external voltages, exhibiting a great potential as actuators in applications in soft robotics, microrobotics, and bioengineering, among others. This paper presents an artificial eukaryotic flagellum (AEF) swimming robot made up of IPMC segments for the study of planar wave generation for robot propulsion by single and distributed actuation, i.e., considering the first flagellum link as an actuator or all of them, respectively. The robot comprises three independent and electrically isolated actuators, manufactured over the same 10 mm long IPMC sheet. For control purposes, a dynamic model of the robot is firstly obtained through its frequency response, acquired by experimentally measuring the flagellum tip deflection thanks to an optical laser meter. In particular, two structures are considered for such a model, consisting of a non-integer order integrator in series with a resonant system of both non-integer and integer order. Secondly, the identified models are analyzed and it is concluded that the tip displacement of each actuator or any IPMC point is characterized by the same dynamics, which remains unchanged through the link with mere variations of the gain for low-frequency applications. Based on these results, a controller robust to gain variations is tuned to control link deflection regardless of link length and enabling the implementation of a distributed actuation with the same controller design. Finally, the deflection of each link is analyzed to determine whether an AEF swimming robot based on IPMC is capable of generating a planar wave motion by distributed actuation

Swimming robot with flexible flagellum based on single actuation: Testing propulsion at low Reynolds number conditions

[Resumen] En entornos con bajo número de Reynolds (Re), los robots nadadores necesitan realizar movimientos no recíprocos para propulsarse. El método fundamental para lograr este tipo de movimiento es mediante la generación de ondas progresivas (también conocidas como ondas viajeras) que recorren el flagelo del robot desde la cabeza al extremo libre. Este trabajo se centra en una forma sencilla de generar ondas progresivas en condiciones de bajo Re que consiste en la oscilación periódica de un flagelo flexible pasivo. Para las pruebas de propulsión, se presenta un prototipo de robot nadador con actuación única basada en el mecanismo yugo escocés y palanca, que permite convertir el movimiento de rotación de un motor en una oscilación angular que viaja a lo largo del flagelo. Asimismo, se desarrolla en MATLAB un algoritmo basado en imágenes para identificar el movimiento realizado por el robot, es decir, para determinar las características del nadador en la propulsión. Los resultados experimentales demuestran que el robot es capaz de realizar un movimiento no recíproco en condiciones de bajo Re.[Abstract] Within low Reynolds number (Re) environments, swimming robots need to perform non-reciprocal motions to propel themselves. The fundamental method to achieve this type of motion is by generating progressive waves (also known as traveling waves) that travel along the robot flagellum from the head to the free end. This work focuses on a simple way to generate progressive waves under low Re conditions that consists of the periodic oscillation of a passive flexible flagellum. For propulsion testing, a prototype of single-acting swimming robot based on the scotch-yoke-lever mechanism is presented, which allows to convert the rotational motion of a motor into an angular oscillation traveling along the flagellum. Also, an image-based algorithm is developed in MATLAB to identify the motion performed by the robot, i.e., to determine the characteristics of the swimmer in propulsion. Experimental results show that the robot is able to perform a non-reciprocal motion under low Re conditions.Ministerio de Ciencia e Innovación; PID2019111278RB-22/AEI/10.13039/501100011033Junta de Extremadura; IB1810

Microrrobot Manufacturing: MEMSLAB at University of Extremadura

[Resumen] La microrrobótica es un campo emergente de investigación con innumerables aplicaciones en el ´ambito de la industria, la biología y la medicina. A pesar de los avances en el campo, todavía existen retos considerables entre los que se encuentra el de la fabricación de robots a escala micrométrica. La fabricación de microrrobots se beneficia de los avances en la fabricación de sistemas microelectromecánicos (MEMS). En este trabajo se presentan los equipos que forman el laboratorio de fabricación de MEMS de la Universidad de Extremadura (UEX), así como ejemplos de fabricación de microrrobots que se han realizado.[Abstract] Microrobotics is an emerging field of research with countless applications in industry, biology and medicine. Despite advances in the field, there are still considerable challenges including that of micrometer-scale robot manufacturing. The fabrication of microrobots benefits from advances in microelectromechanical systems (MEMS) manufacturing. This paper presents the equipment that forms the MEMS fabrication laboratory at Universidad de Extremadura (UEX), as well as examples of microrobot fabrication that have been carried out.Junta de Extremadura; IB18109Junta de Extremadura; GR18159Este artículo ha sido financiado por la Consejería de Economía, Ciencia y Agenda Digital de la Junta de Extremadura mediante el proyecto IB18109 y la “Ayuda a Grupos” GR18159, por la Agencia Estatal de Investigación mediante el proyecto PID2019-111278RB-C22 / AEI / 10.13039/501100011033, y por los Fondos Europeos de Desarrollo Regional “Una manera de hacer Europa”.https://doi.org/10.17979/spudc.978849749804