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This paper proposes several task space control approaches for complex on-orbit high degrees of freedom robots. These approaches include redundancy resolution and take the non-linear dynamic model of the on-orbit robotic systems into account. The suitability of the proposed task space control approaches is explored in several on-orbit servicing operations requiring visual servoing tasks of complex humanoid robots. A unified open-source framework for space-robotics simulations, called OnOrbitROS, is used to evaluate the proposed control systems and compare their behaviour with state-of-the-art existing ones. The adopted framework is based on ROS and includes and reproduces the principal environmental conditions that eventual space robots and manipulators could experience in an on-orbit servicing scenario. The architecture of the different software modules developed and their application on complex space robotic systems is presented. Efficient real-time implementations are achieved using the proposed OnOrbitROS framework. The proposed controllers are applied to perform the guidance of a humanoid robot. The robot dynamics are integrated into the definition of the controllers and an analysis of the results and practical properties are described in the results section.

The control problem of the rotary double inverted pendulum (double Furuta pendulum) is nontrivial because of underactuation and strong nonlinearities in the associated state-space model. The system has three degrees of freedom (one actuated and two unactuated joints) while receiving only one control input. In this article, a novel nonlinear optimal (H-infinity) control approach is developed for the dynamic model of the rotary double inverted pendulum. First, the dynamic model of the double pendulum undergoes approximate linearization with the use of first-order Taylor series expansion and through the computation of the associated Jacobian matrices. The linearization process takes place at each sampling instance around a temporary operating point which is defined by the present value of the system's state vector and by the last sampled value of the control inputs vector. At a next stage a stabilizing H-infinity feedback controller is designed. To compute the controller's feedback gains an algebraic Riccati equation has to be solved at each time-step of the control algorithm. The global stability properties of the control scheme are proven through Lyapunov analysis. To implement state estimation-based control without the need to measure the entire state vector of the rotary double-pendulum the H-infinity Kalman Filter is used as a robust state observer. The nonlinear optimal control method achieves fast and accurate tracking of setpoints by all state variables of the rotary double inverted pendulum under moderate variations of the control input.

Selective compliance articulated robot arms (SCARA) robotic manipulators find wide use in industry. A nonlinear optimal control approach is proposed for the dynamic model of the 4-degrees of freedom (DOF) SCARA robotic manipulator. The dynamic model of the SCARA robot undergoes approximate linearization around a temporary operating point that is recomputed at each time-step of the control method. The linearization relies on Taylor series expansion and on the associated Jacobian matrices. For the linearized state-space model of the system, a stabilizing optimal (H-infinity) feedback controller is designed. To compute the controller’s feedback gains, an algebraic Riccati equation is repetitively solved at each iteration of the control algorithm. The stability properties of the control method are proven through Lyapunov analysis. The proposed control method is advantageous because: (i) unlike the popular computed torque method for robotic manipulators, it is characterized by optimality and is also applicable when the number of control inputs is not equal to the robot’s number of DOFs and (ii) it achieves fast and accurate tracking of reference setpoints under minimal energy consumption by the robot’s actuators. The nonlinear optimal controller for the 4-DOF SCARA robot is finally compared against a flatness-based controller implemented in successive loops.

Editorial on the Research Topic Multi-robot systems for space applications

En este proyecto se ha investigado y analizado el impacto de diferentes gravedades en la planificación y seguimiento de trayectorias en un robot cuadrúpedo, en concreto, el robot Go1 de Unitree Robotics. Para ello se ha introducido el robot Go1 en el framework TOWR para planificar las trayectorias en tres distintas condiciones de gravedad: terrestre, marciana e intermedia. Una vez generadas, mediante los paquetes proporcionados por Unitree Robotics y los rosbag con las trayectorias generadas por TOWR, se ha realizado el seguimiento de dichas trayectorias en Gazebo. Tanto en la planificación como en el seguimiento se realiza una comparación entre las trayectorias y se observa cómo va afectando la reducción de la gravedad. Así mismo, también se comparan los resultados de la planificación con los del seguimiento. Además, se realizan diversas pruebas con el robot real en gravedad terrestre. Los pasos seguidos para realizar este proyecto son: 1. Estudio de TOWR e incluir el robot en dicho framework. 2. Estudio de la cinemática y dinámica del robot. 3. Generar las trayectorias. 4. Crear un archivo capaz de leer valores de un rosbag y realizar el seguimiento de la trayectoria. 5. Recopilar los datos tanto en simulación como en la realidad y comparar los resultandos

En este proyecto se ha realizado la simulación de un robot humanoide para su aplicación en tareas de mantenimiento de satélites en órbita. Para ello, se han seguido los siguientes pasos: 1. Diseño del robot. Se han estudiado las características cinemáticas y dinámicas de este tipo de robots. El robot ha de disponer de la suficiente capacidad de movimiento y manipulación para su aplicación a este tipo de tareas. Dispone de dos brazos con pinzas, así como un torso para asimilar su espacio de trabajo al de un humano. 2. Simulación del robot. Una vez diseñado el robot se han simulado las condiciones orbitales de ausencia de gravedad/gradiente orbital para asimilar su comportamiento al que dispondría en órbita. Además, se emplea Gazebo para simular el robot y un entorno de funcionamiento lo más realista posible. 3. Control del robot. En esta última fase del proyecto se evalúa el robot mediante distintos controladores. Se utiliza ROS Control para evaluar el comportamiento del robot utilizando controladores PID articulares clásicos así como otras estrategias de control. Esto permite evaluar y determinar el controlador más adecuado para este tipo de aplicaciones.

En este proyecto, se ha desarrollado el control de locomoción de un robot cuadrúpedo mediante el uso de técnicas de deep reinforcement learning. Para ello, se ha llevado a cabo un estudio del estado del arte para identificar los métodos más apropiados para la tarea de locomoción cuadrúpeda, y su posterior implementación en entornos simulados. Se han evaluado entornos y simulaciones basadas en MuJoCo como Cartpole y Ant hasta llegar a la locomoción de un robot cuadrúpedo.

En el campo de las prótesis se ha abierto una nueva rama de investigación que trata de emplear las técnicas y materiales propios de la robótica blanda. Éstos han demostrado tener potencial, entre otras aplicaciones, para el uso en el contacto físico entre hombre-robot como dispositivos de rehabilitación debido a las prestaciones que ofrecen como liviandad, baja dureza, contacto autoadaptativo, buena relación peso-potencia y bajo costo. El objetivo entonces es diseñar, construir y determinar la destreza de una prótesis biomimética de mano utilizando técnicas y materiales comunes dentro de la robótica blanda.

En este trabajo se ha diseñado un exoesqueleto de miembro inferior ajustable a la pierna de cualquier paciente, cuyo propósito es permitir y facilitar su movimiento. El diseño parte de una órtesis de rodilla sobre la que se ha diseñado la ubicación de las articulaciones. Esta órtesis ha sido ampliada, no sólo con los elementos necesarios para la actuación de la rodilla, sino también con las piezas que permiten la sujeción y movilidad de otras partes de la pierna como el tobillo y cadera. Así como el modelado de soportes de los motores encargados de mover dichas articulaciones. El exoesqueleto integra sensores EMG, necesarios para percibir la intención de movimiento del paciente y controlar el exoesqueleto durante la marcha. Para ello se ha realizado un estudio de la posición de los sensores EMG y las debidas rectificaciones de las señales detectadas para conseguir una lectura eficaz y eficiente de los músculos. Además de poder percibir el propósito de movimiento del paciente para que sea asistido por el exoesqueleto. Una vez realizado el estudio de los sensores EMG, se ha establecido una comunicación entre dichos sensores inalámbricos y la simulación del diseño en ROS.

In this work, we evaluate the relationship between human manipulability indices obtained from motion sensing cameras and a variety of muscular factors extracted from surface electromyography (sEMG) signals from the upper limb during specific movements that include the shoulder, elbow and wrist joints. The results show specific links between upper limb movements and manipulability, revealing that extreme poses show less manipulability, i.e., when the arms are fully extended or fully flexed. However, there is not a clear correlation between the sEMG signals’ average activity and manipulability factors, which suggests that muscular activity is, at least, only indirectly related to human pose singularities. A possible means to infer these correlations, if any, would be the use of advanced deep learning techniques. We also analyze a set of EMG metrics that give insights into how muscular effort is distributed during the exercises. This set of metrics could be used to obtain good indicators for the quantitative evaluation of sequences of movements according to the milestones of a rehabilitation therapy or to plan more ergonomic and bearable movement phases in a working task.

The control problem for the nonlinear dynamics of robotic and mechatronic systems with electropneumatic actuation is solved with the use of a flatness-based control approach which is implemented in successive loops. The state-space model of these systems is separated into a series of subsystems, which are connected between them in cascading loops. Each one of these subsystems can be viewed independently as a differentially flat system and control about it can be performed with inversion of its dynamics as in the case of input-output linearized flat systems. In this chain of i = 1, 2, · · · ,N subsystems, the state variables of the subsequent (i + 1-th) subsystem become virtual control inputs for the preceding (i-th) subsystem, and so on. In turn, exogenous control inputs are applied to the last subsystem and are computed by tracing backwards the virtual control inputs of the preceding N −1 subsystems. The whole control method is implemented in successive loops and its global stability properties are also proven through Lyapunov stability analysis. The validity of the control method is confirmed in two case studies: (a) control of an electropneumatic actuator, (ii) control of a multi-DOF robotic manipulator with electropneumatic actuators.

Purpose – A distinctive feature of tilt-rotor UAVs is that they can be fully actuated, whereas in fixed-angle rotor UAVs (e.g. common-type quadrotors, octorotors, etc.), the associated dynamic model is characterized by underactuation. Because of the existence of more control inputs, in tilt-rotor UAVs, there is more flexibility in the solution of the associated nonlinear control problem. On the other side, the dynamic model of the tilt-rotor UAVs remains nonlinear and multivariable and this imposes difficulty in the drone's controller design. This paper aims to achieve simultaneously precise tracking of trajectories and minimization of energy dissipation by the UAV's rotors. To this end elaborated control methods have to be developed. Design/methodology/approach – A solution of the nonlinear control problem of tilt-rotor UAVs is attempted using a novel nonlinear optimal control method. This method is characterized by computational simplicity, clear implementation stages and proven global stability properties. At the first stage, approximate linearization is performed on the dynamic model of the tilt-rotor UAV with the use of first-order Taylor series expansion and through the computation of the system's Jacobian matrices. This linearization process is carried out at each sampling instance, around a temporary operating point which is defined by the present value of the tilt-rotor UAV's state vector and by the last sampled value of the control inputs vector. At the second stage, an H-infinity stabilizing controller is designed for the approximately linearized model of the tilt-rotor UAV. To find the feedback gains of the controller, an algebraic Riccati equation is repetitively solved, at each time-step of the control method. Lyapunov stability analysis is used to prove the global stability properties of the control scheme. Moreover, the H-infinity Kalman filter is used as a robust observer so as to enable state estimation-based control. The paper's nonlinear optimal

Actualmente, la utilización de herramientas de simulación como ROS/Gazebo es una práctica habitual para la simulación y desarrollo de algoritmos de control para sistemas robóticos terrestres típicos. Sin embargo, en la actualidad aún no está comúnmente aceptado en la comunidad espacial. Numerosos estudios en el campo de la robótica espacial utilizan herramientas construidas ad-hoc, pero que no están estandarizadas, que no son de código abierto y que, además, no han sido verificadas, lo que complica el desarrollo y la simulación de sistemas robóticos versátiles y algoritmos para el control de sistemas robóticos espaciales. Este artículo propone una solución de código abierto para la simulación de robots espaciales en órbita denominada OnOrbitROS. Este trabajo presenta una descripción de la arquitectura, los diferentes módulos software y las posibilidades de simulación de OnOrbitROS. Se describen las características clave de la herramienta desarrollada, con especial atención a la personalización de las simulaciones y a las posibilidades de ampliación de la herramienta. Con el fin de mostrar estas capacidades, se describen los resultados obtenidos al aplicar OnOrbitROS para la simulación del robot ETS-VII., Currently, the use of simulation tools such as ROS/Gazebo is a common practice for the simulation and development of control algorithms for typical terrestrial robotic systems. Numerous studies in the field of space robotics use ad-hoc built tools, but they are not standardized, and are unverified, which complicates the development and simulation of versatile robotic systems. This paper proposes an open-source solution for the simulation of orbiting space robots called OnOrbitROS. This work presents a description of the architecture, the different software modules and the simulation possibilities of OnOrbitROS. The key features of the developed tool are described, with special attention to the customization of the simulations and the possibilities of extension of the tool. In order to show these capabilities, the results obtained in the simulation of the robot ETS-VII by using OnOrbitROS are described.

Nonlinear control for autonomous reentry space vehicles has been a topic of intensive research during the last years in the area of aerospace science and technology. The associated dynamic model is obtained by expressing position variables and orientation angles of the space vehicle in different coordinate frames, namely an earth-fixed, an earth rotating and a body fixed frame. In this article, a nonlinear optimal control approach is proposed for the dynamic model of reentry space vehicles. It is proven that the longitudinal motion dynamic model of reentry space vehicles is differentially flat and a flatness-based controller is designed about it. Next, in the nonlinear optimal control approach, the dynamic model of the reentry space vehicle undergoes approximate linearization around a temporary operating point that is recomputed at each time-step of the control method. The linearization relies on Taylor series expansion and on the associated Jacobian matrices. For the linearized state-space model of the reentry space vehicle a stabilizing optimal (H-infinity) feedback controller is designed. This controller stands for the solution to the nonlinear optimal control problem under model uncertainty and external perturbations. To compute the controller’s feedback gains an algebraic Riccati equation is repetitively solved at each iteration of the control algorithm. The stability properties of the control method are proven through Lyapunov analysis. The proposed nonlinear optimal control approach achieves fast and accurate tracking of reference setpoints under moderate variations of the control inputs and a minimum dispersion of energy.

Purpose – Permanent magnet synchronous spherical motors can have wide use in robotics and industrial automation. They enable three-DOF omnidirectional motion of their rotor. They are suitable for several applications, such as actuation in robotics, traction in electric vehicles and use in several automation systems. Unlike conventional synchronous motors, permanent magnet synchronous spherical motors consist of a fixed inner shell, which is the stator, and a rotating outer shell, which is the rotor. Their dynamic model is multivariable and strongly nonlinear. The treatment of the associated control problem is important. Design/methodology/approach – In this paper, the multivariable dynamic model of permanent magnet synchronous spherical motors is analysed, and a nonlinear optimal (H-infinity) control method is developed for it. Differential flatness properties are proven for the spherical motors’ state-space model. Next, the motors’ state-space description undergoes approximate linearization with the use of first-order Taylor series expansion and through the computation of the associated Jacobian matrices. The linearization process takes place at each sampling instance around a time-varying operating point, which is defined by the present value of the motors’ state vector and by the last sampled value of the control input vector. For the approximately linearized model of the permanent magnet synchronous spherical motors, a stabilizing H-infinity feedback controller is designed. To compute the controller’s gains, an algebraic Riccati equation has to be repetitively solved at each time-step of the control algorithm. The global stability properties of the control scheme are proven through Lyapunov analysis. Finally, the performance of the nonlinear optimal control method is compared against a flatness-based control approach implemented in successive loops. Findings – Due to the nonlinear and multivariable structure of the state-space model of spherical motors, the solu

En este proyecto se realizará el diseño de una misión multi-robot para su aplicación en tareas de mantenimiento de satélites en órbita. Para ello, se seguirán los siguientes pasos: 1. Diseño del robot. Se estudiarán las características cinemáticas y dinámicas de este tipo de robots. El robot habrá de disponer de la suficiente capacidad de movimiento y manipulación para su aplicación a este tipo de tareas. 2. Simulación del robot. Una vez diseñado el robot se habrán de simular las condiciones orbitales de ausencia de gravedad/gradiente orbital para asimilar su comportamiento al que dispondría en órbita. Además, se empleará gazebo para simular el robot y un entorno de funcionamiento lo más realista posible. 3. Control del robot. En esta última fase del proyecto se evaluará el robot realizando distinto tipo de tareas (alcance, manipulación, uso de herramientas, etc.). Para ello será necesario no sólo definir las posiciones a alcanzar sino también las trayectorias necesarias. Se utilizará ROS Control para evaluar el comportamiento del robot utilizando distinto tipo de controladores.

[Resumen] Actualmente, la utilización de herramientas de simulación como ROS/Gazebo es una práctica habitual para la simulación y desarrollo de algoritmos de control para sistemas robóticos terrestres típicos. Sin embargo, en la actualidad aún no está comúnmente aceptado en la comunidad espacial. Numerosos estudios en el campo de la robótica espacial utilizan herramientas construidas ad-hoc, pero que no están estandarizadas, que no son de código abierto y que, además, no han sido verificadas, lo que complica el desarrollo y la simulación de sistemas robóticos versátiles y algoritmos para el control de sistemas robóticos espaciales. Este artículo propone una solución de código abierto para la simulación de robots espaciales en órbita denominada OnOrbitROS. Este trabajo presenta una descripción de la arquitectura, los diferentes módulos software y las posibilidades de simulación de OnOrbitROS. Se describen las características clave de la herramienta desarrollada, con especial atención a la personalización de las simulaciones y a las posibilidades de ampliación de la herramienta. Con el fin de mostrar estas capacidades, se describen los resultados obtenidos al aplicar OnOrbitROS para la simulación del robot ETS-VII., [Abstract] Currently, the use of simulation tools such as ROS/Gazebo is a common practice for the simulation and development of control algorithms for typical terrestrial robotic systems. Numerous studies in the field of space robotics use ad-hoc built tools, but they are not standardized, and are unverified, which complicates the development and simulation of versatile robotic systems. This paper proposes an open-source solution for the simulation of orbiting space robots called OnOrbitROS. This work presents a description of the architecture, the different software modules and the simulation possibilities of OnOrbitROS. The key features of the developed tool are described, with special attention to the customization of the simulations and the possibilities of extension of the tool. In order to show these capabilities, the results obtained in the simulation of the robot ETS-VII by using OnOrbitROS are described.

En este proyecto se ha realizado la planificación de trayectorias de un exoesqueleto de miembro inferior. Se ha partido del diseño de un exoesqueleto de pierna y su modelo URDF y se han seguido los siguientes pasos: 1. Diseño del modelo del robot en xpp: http://wiki.ros.org/xpp. Se ha diseñado el exoesqueleto para que sea capaz de generar los movimientos necesarios en las piernas del usuario para alcanzar una determinada localización. Por lo tanto, no sólo permite el movimiento de sus articulaciones, sino también hacerlo de forma que permita guiar al usuario hasta que su cuerpo alcance la posición y orientación indicada. 2. Integración del exoesqueleto simulado en towr: https://github.com/ethz-adrl/towr. Este framework permite generar un problema de optimización para la generación automática de trayectorias de robots. En concreto, en este proyecto se ha evaluado el uso de este tipo de soluciones para la planificación de movimientos de exoesqueletos y la generación de patrones de marcha. Un aspecto fundamental en este caso es que los movimientos del robot se deben ajustar a la capacidad de movimiento del usuario. Por lo tanto, el espacio de búsqueda del problema de optimización deberá ser dinámico y ajustado en cada momento al estado del paciente. Esto ha permitido generar movimientos realistas y adaptados al paciente. 3. Uso de visión para el reconocimiento del terreno. Se ha utilizado una cámara Intel REALSENSE LiDAR L515 y procesado la nube de puntos para extraer las características que definen el terreno por el que ha de moverse el exoesqueleto. Más concretamente, se ha analizado su utilización para el reconocimiento de escaleras lo que ha permitido planificar movimientos del exoesqueleto para subir escaleras.

An optimization algorithm for planning the motion of a humanoid robot during extravehicular activities is presented in this paper. The algorithm can schedule and plan the movements of the two robotic arms to move the humanoid robot by using the handrails present outside the International Space Station. The optimization algorithm considers the eventual constraints imposed by the topology of the handrails and calculates the sequence of grasping and nongrasping phases needed to push and pull the robot along the handrails. A low-level controller is also developed and used to track the planned arms and end-effectors trajectories. Numerical simulations assess the applicability of the proposed strategy in three different typical operations that potentially can be performed in an extravehicular activity scenario.

The article proposes flatness-based control and a Kalman Filter-based disturbance observer for solving the control problem of a robotic exoskeleton under time-delayed exogenous disturbances. A two-link lower-limb robotic exoskeleton is used as a case study. It is proven that this robotic system is differentially flat. The robot is considered to be subject to unknown contact forces at its free-end which in turn generate unknown disturbance torques at its joints. It is shown that the dynamic model of the robotic exoskeleton can be transformed into the input-output linearized form and equivalently into the linear canonical Brunovsky form. This linearized description of the exoskeleton's dynamics is both controllable and observable. It allows for designing a stabilizing feedback controller with the use of the pole-placement (eigenvalues assignment) method. Moreover, it allows for solving the state estimation problem with the use of Kalman Filtering (the use of the Kalman Filter on the flatness-based linearized model of nonlinear dynamical systems is also known as Derivative-free nonlinear Kalman Filtering). Furthermore, (i) by extending the state vector of the exoskeleton after considering as additional state variables the additive disturbance torques which affect its joints and (ii) by redesigning the Kalman Filter as a disturbance observer, one can achieve the real-time estimation of the perturbations that affect this robotic system. Finally, by including in the controller of the exoskeleton additional terms that compensate for the estimated disturbance torques, the perturbations' effects can be eliminated and the precise tracking of reference trajectories by the joints of this robot can be ensured.

In this paper, we present ARMIA: a sensorized arm wearable that includes a combination of inertial and sEMG sensors to interact with serious games in telerehabilitation setups. This device reduces the cost of robotic assistance technologies to be affordable for end-users at home and at rehabilitation centers. Hardware and acquisition software specifications are described together with potential applications of ARMIA in real-life rehabilitation scenarios. A detailed comparison with similar medical technologies is provided, with a specific focus on wearable devices and virtual and augmented reality approaches. The potential advantages of the proposed device are also described showing that ARMIA could provide similar, if not better, the effectivity of physical therapy as well as giving the possibility of home-based rehabilitation.

En el presente trabajo se realizará una aproximación a la planificación de trayectorias para exoesqueletos de miembro inferior aplicados a rehabilitación, y en particular, para el exoesqueleto Exo-H3 de Technaid, el cual se empleará en simulación. La planificación de trayectorias consiste en la búsqueda de una sucesión de posiciones para un robot, que permitan llevarlo desde un estado inicial a uno final. Este proceso representa una etapa fundamental en la generación de movimiento y uso de instrumentos robóticos, tomando especial relevancia en el caso planteado pues se aplica a un dispositivo vestible que se debe ajustar a la mecánica del cuerpo y a la marcha humana. En primer lugar, se llevará a cabo un estudio de los diferentes marcos teóricos que conciernen a este trabajo. Realizando un estudio del estado del arte de la rehabilitación asistida por robots y las alternativas actuales, así como de las particularidades fisiológicas que afectan a la marcha, y de la propia generación de movimientos para robots. Seguidamente, se incluirá el exoesquelto Exo-H3 en la aplicación towr, un framework de generación de trayectorias para robots con patas. Complementariamente se desarrollará un sistema de obtención del ángulo de la rodilla a partir de señales electromiográficas de ciertos músculos de la pierna, para lo cual se generará una base de datos a partir de pruebas experimentales con un conjunto de sujetos y se aplicará un regresor lineal para obtener dicho sistema. Con esto, se planeta una generación de trayectorias que respete las características de la marcha humana gracias a la introducción de restricciones en el framework de towr, y que sea asistida por un sistema que tenga en cuenta las señales neuromecánicas del cuerpo asociadas al propio movimiento de la pierna.

El proyecto docente “Exoforge: Laboratorio docente interdisciplinar para desarrollo de proyectos en tecnologías asistivas” se plantea como una herramienta de formación complementaria para ingenieros e ingenieras en el ámbito de las tecnologías de la salud para cubrir esas necesidades desde una orientación multidisciplinar. Desde el punto de vista docente, este proyecto trata de abordar dos aspectos esenciales en la formación de futuros ingenieros que trabajen en el ámbito de las tecnologías asistivas: la multidisciplinariedad y la orientación laboral y el emprendimiento. Los resultados obtenidos han sido muy satisfactorios tanto desde el punto de vista cuantitativo como cualitativo.

Las misiones espaciales actuales y futuras no se entienden sin la utilización de robots. Es dentro de este ámbito general en el que se plantea la presente Tesis Doctoral, con el propósito de proponer tecnologías para el control y guiado de robots en órbita que les permita desarrollar las misiones en las que están actualmente implicados y en las que, sin duda, estarán en un futuro próximo. Para la implementación y simulación de los distintos algoritmos y controladores propuestos se ha implementado un framework basado en ROS denominado OnOrbitROS. Este entorno extiende las capacidades de ROS para permitir la simulación de sistemas robóticos espaciales en órbita. Tras definir y validar esta herramienta se han realizado distintas aportaciones tanto para la planificación como para el control de robots espaciales en órbita. Estas aportaciones se han aplicado tanto a sencillos manipuladores en libre flotación como a complejos robots humanoides guiados empleando realimentación sensorial procedente de cámaras y sensores de fuerza. Así, se ha propuesto un algoritmo de planificación para robots en órbita capaz de generar de forma automática los movimientos que ha de describir un robot para alcanzar un determinado objetivo. Este algoritmo, basado en optimización, definirá las trayectorias de las articulaciones o del efector final del robot. Tras proponer este algoritmo se ha trabajado en la propuesta de controladores con el propósito de realizar el seguimiento de las trayectorias definidas. Se han propuesto nuevos controladores con distintas propiedades, aplicaciones y características dinámicas cuyos resultados avalan su aplicación en robots de estas características. Cabe destacar, por ejemplo, la definición de ontroladores basados en optimización, controladores con realimentación visual y fuerza, controladores basados en velocidad, fuerza o aceleración, etc. A lo largo de la Tesis se exponen cada uno de estos controladores, se describen sus características y aplicaciones, y se

The use of simulation tools such as ROS/Gazebo is currently common practice for testing and developing control algorithms for typical ground-based robotic systems but still is not commonly accepted within the space community. Numerous studies in this field use ad-hoc built, but not standardized, not open-source, and, sometimes, not verified tools that complicate, rather than promote, the development and realization of versatile robotic systems and algorithms for space robotics. This paper proposes an open-source solution for space robotics simulations called OnOrbitROS. This paper presents a description of the architecture, the different software modules, and the simulation possibilities of OnOrbitROS. It shows the key features of the developed tool, with a particular focus on the customization of the simulations and eventual possibilities of further expansion of the tool. In order to show these capabilities, a computed torque-based controller for the guidance of a free-floating manipulator is proposed and simulated using the ROS/Gazebo-based framework described in the paper.

This paper proposes and investigates strategies that can be used to plan the motion and control of humanoid robots in some elementary tasks that characterize extravehicular activities. The humanoid robot taken into account is a torso with two arms and two grippers at their extremities. This study addresses the problem of robot motion on the complex system of handrails and handles that characterize the International Space Station. Such a complex task has been divided into two elementary sub-tasks: motion planning and tracking the planned trajectories. First, an optimization procedure is presented to plan and coordinate the robot's arms motions and graspers to achieve the desired location using handrails. Then, a low-level controller is used to guarantee that the robots' actuators can follow these previously generated trajectories. Simulation results assess the applicability of the proposed strategy in different typical operations that potentially can be performed in an extravehicular activity scenario.

Tower cranes find wide use in construction works, in ports and in several loading and unloading procedures met in industry. A nonlinear optimal control approach is proposed for the dynamic model of the 4-DOF underactuated tower crane. The dynamic model of the robotic crane undergoes approximate linearization around a temporary operating point that is recomputed at each time-step of the control method. The linearization relies on Taylor series expansion and on the associated Jacobian matrices. For the linearized state-space model of the system a stabilizing optimal (H-infinity) feedback controller is designed. To compute the controller’s feedback gains an algebraic Riccati equation is repetitively solved at each iteration of the control algorithm. The stability properties of the control method are proven through Lyapunov analysis. The proposed control approach is advantageous because: (i) unlike the popular computed torque method for robotic manipulators, the new control approach is characterized by optimality and is also applicable when the number of control inputs is not equal to the robot’s number of DOFs, (ii) it achieves fast and accurate tracking of reference setpoints under minimal energy consumption by the robot’s actuators, (iii) unlike the popular Nonlinear Model Predictive Control method, the article’s nonlinear optimal control scheme is of proven global stability and convergence to the optimum.

This paper proposes a nonlinear optimal control approach for mulitple degrees of freedom (DOF) brachiation robots, which are often used in inspection and maintenance tasks of the electric power grid. Because of the nonlinear and multivariable structure of the related state-space model, as well as because of underactuation, the control problem of these robots is nontrivial. The dynamic model of the brachiation robots undergoes first approximate linearization with the use of Taylor series expansion around a temporary operating point which is recomputed at each iteration of the control method. For the approximately linearized model, an H-infinity feedback controller is designed. The linearization procedure relies on the Jacobian matrices of the brachiation robots’ state-space model. The proposed control method stands for the solution of the optimal control problem for the nonlinear and multivariable dynamics of the brachiation robots, under model uncertainties and external perturbations. For the computation of the controller’s feedback gains an algebraic Riccati equation is solved at each time-step of the control method. The global stability properties of the control scheme are proven through Lyapunov analysis. The new nonlinear optimal control approach achieves fast and accurate tracking for all state variables of the brachiation robots, under moderate variations of the control inputs.

A direct visual-servoing algorithm for control of a space-based two-arm manipulator is proposed in this paper. The algorithm can be utilized in a two-arm manipulators configuration, where one of the arms performs the manipulation and the second arm is dedicated to the observation of the target zone of manipulation. The algorithm utilizes both visual features extracted from onboard cameras and force and torque measured at the manipulator's end-effector to control the movements of the manipulator during on-orbit servicing operations. The algorithm takes into account the relative dynamics of the bodies involved, it relies on images taken independently from de-localized cameras, e.g. at the end-effector of a second manipulator, and it integrates an impedance control for the compensation of eventual contact reactions when the end effector touches and operates the target body. The analytical derivations demonstrate the stability of the algorithm and incorporate an impedance compliance strategy into an optimal framework formulation. Simulations results in two different scenarios have been presented to show the adequate behavior of the presented approach in on-orbit-servicing operations.

El trabajo que aquí se propone intenta introducir una metodología de aprendizaje por proyectos para la asignatura Sistemas de Percepción del máster en Automatización y Robótica de la Universidad de Alicante. Las condiciones heterogéneas de los estudiantes y la combinación de requisitos de enseñanza presencial y online hicieron que los profesores cambiaran el modelo de enseñanza actual basado solo en clases teóricas y ejercicios prácticos individuales, a un horario más flexible siguiendo un esquema de aprendizaje activo basado en proyectos. Uno de los problemas que los docentes encontraron en esta asignatura y en el máster en general es la diferencia de conocimientos entre los alumnos en las distintas áreas que cubre la asignatura. Esto se debe a la heterogeneidad de estudiantes que provienen de diferentes titulaciones de diversas universidades e incluso países. El otro gran reto al que deben enfrentarse los docentes es la adaptación a las actuales clases de docencia combinada presencial y online. Para evaluar las ventajas y desventajas de esta propuesta se realizaron dos encuestas, una para los estudiantes y otra para los profesores actuales y anteriores de la asignatura. Los resultados muestran cómo esta estrategia obtuvo buenos resultados incluso para los estudiantes sin conocimientos previos del área temática.

The article proposes a nonlinear optimal (H-infinity) control approach for a type of underactuated power-line inspection robots. To implement this control scheme, the state-space model of the power-line inspection robots undergoes first approximate linearization around a temporary operating point, through first-order Taylor series expansion and through the computation of the associated Jacobian matrices. To select the feedback gains of the controller an algebraic Riccati equation is solved at each time step of the control method. The global stability properties of the control loop are proven through Lyapunov analysis. The significance of the article’s results is outlined in the following: (i) the proposed control method is suitable for treating underactuated robotic systems and in general nonlinear dynamical systems with control inputs gain matrices which are in a nonquadratic form, (ii) by achieving stabilization of the power-line inspection robots in underactuation conditions the proposed control method ensures the reliable functioning of these robotic systems in the case of actuators’ failures or enables the complete removal of certain actuators and the reduction of the weight of these robotic systems, (iii) the proposed control method offers a solution to the nonlinear optimal control problem which is of proven global stability while also remaining computationally tractable, (iv) the proposed nonlinear optimal control method retains the advantages of linear optimal control that is fast and accurate tracking of reference setpoints under moderate variations of the control inputs, and (v) by minimizing the amount of energy that is dispersed by the actuators of the power-line inspection robots the proposed control method improves the autonomy and operational capacity of such robotic systems.