Design, modeling and implementation of a soft robotic neck for humanoid robots

Mención Internacional en el título de doctorSoft humanoid robotics is an emerging field that combines the flexibility and safety of soft robotics with the form and functionality of humanoid robotics. This thesis explores the potential for collaboration between these two fields with a focus on the development of soft joints for the humanoid robot TEO. The aim is to improve the robot’s adaptability and movement, which are essential for an efficient interaction with its environment. The research described in this thesis involves the development of a simple and easily transportable soft robotic neck for the robot, based on a 2 Degree of Freedom (DOF) Cable Driven Parallel Mechanism (CDPM). For its final integration into TEO, the proposed design is later refined, resulting in an efficiently scaled prototype able to face significant payloads. The nonlinear behaviour of the joints, due mainly to the elastic nature of their soft links, makes their modeling a challenging issue, which is addressed in this thesis from two perspectives: first, the direct and inverse kinematic models of the soft joints are analytically studied, based on CDPM mathematical models; second, a data-driven system identification is performed based on machine learning techniques. Both approaches are deeply studied and compared, both in simulation and experimentally. In addition to the soft neck, this thesis also addresses the design and prototyping of a soft arm capable of handling external loads. The proposed design is also tendon-driven and has a morphology with two main bending configurations, which provides more versatility compared to the soft neck. In summary, this work contributes to the growing field of soft humanoid robotics through the development of soft joints and their application to the humanoid robot TEO, showcasing the potential of soft robotics to improve the adaptability, flexibility, and safety of humanoid robots. The development of these soft joints is a significant achievement and the research presented in this thesis paves the way for further exploration and development in this field.La robótica humanoide blanda es un campo emergente que combina la flexibilidad y seguridad de la robótica blanda con la forma y funcionalidad de la robótica humanoide. Esta tesis explora el potencial de colaboración entre estos dos campos centrándose en el desarrollo de una articulación blanda para el cuello del robot humanoide TEO. El objetivo es mejorar la adaptabilidad y el movimiento del robot, esenciales para una interacción eficaz con su entorno. La investigación descrita en esta tesis consiste en el desarrollo de un prototipo sencillo y fácilmente transportable de cuello blando para el robot, basado en un mecanismo paralelo actuado por cable de 2 grados de libertad. Para su integración final en TEO, el diseño propuesto es posteriormente refinado, resultando en un prototipo eficientemente escalado capaz de manejar cargas significativas. El comportamiemto no lineal de estas articulaciones, debido fundamentalmente a la naturaleza elástica de sus eslabones blandos, hacen de su modelado un gran reto, que en esta tesis se aborda desde dos perspectivas diferentes: primero, los modelos cinemáticos directo e inverso de las articulaciones blandas se estudian analíticamente, basándose en modelos matemáticos de mecanismos paralelos actuados por cable; segundo, se aborda el problema de la identificación del sistema mediante técnicas basadas en machine learning. Ambas propuestas se estudian y comparan en profundidad, tanto en simulación como experimentalmente. Además del cuello blando, esta tesis también aborda el diseño de un brazo robótico blando capaz de manejar cargas externas. El diseño propuesto está igualmente basado en accionamiento por tendones y tiene una morfología con dos configuraciones principales de flexión, lo que proporciona una mayor versatilidad en comparación con el cuello robótico blando. En resumen, este trabajo contribuye al creciente campo de la robótica humanoide blanda mediante el desarrollo de articulaciones blandas y su aplicación al robot humanoide TEO, mostrando el potencial de la robótica blanda para mejorar la adaptabilidad, flexibilidad y seguridad de los robots humanoides. El desarrollo de estas articulaciones es una contribución significativa y la investigación presentada en esta tesis allana el camino hacia nuevos desarrollos y retos en este campo.Programa de Doctorado en Ingeniería Eléctrica, Electrónica y Automática por la Universidad Carlos III de MadridPresidenta: Cecilia Elisabet García Cena.- Secretario: Dorin Sabin Copaci.- Vocal: Martin Fodstad Stole

Design and performance validation of a cable-driven soft robotic neck

This paper has been presented at Jornadas Nacionales de Robótica 2018The purpose of this paper is to design a soft robotic neck prototype with two Degrees of Freedom (DOF). It is mainly aimed to investigate, study and design a mechanism that allows to simulate the movements of a human neck, concretely the movements of flexion, extension and lateral bending. To archieve these movements, the design is made based on a cable-driven mechanism, validating the design of spring, through which it will be possible to obtain the sketch of the components that make up the soft neck and then its manufacture in a 3D printer. Another important aspect for the development of the project is the load weight that the soft neck can support, in order to size the motors that are needed for the operation of the parallel mechanism. In addition, the analysis of its mathematical model for the control system that will be implemented in future work is carried out.The research leading to these results has received funding from the HUMASOFT project, with reference DPI2016-75330-P, funded by the Spanish Ministry of Economy and Competitiveness

A New Approach of Soft Joint Based on a Cable-Driven Parallel Mechanism for robotic Applications

A soft joint has been designed and modeled to perform as a robotic joint with 2 Degrees of Freedom (DOF) (inclination and orientation). The joint actuation is based on a Cable-Driven Parallel Mechanism (CDPM). To study its performance in more detail, a test platform has been developed using components that can be manufactured in a 3D printer using a flexible polymer. The mathematical model of the kinematics of the soft joint is developed, which includes a blocking mechanism and the morphology workspace. The model is validated using Finite Element Analysis (FEA) (CAD software). Experimental tests are performed to validate the inverse kinematic model and to show the potential use of the prototype in robotic platforms such as manipulators and humanoid robots.The research leading to these results has received funding from the project Desarrollo de articulaciones blandas para aplicaciones robóticas, with reference IND2020/IND-1739, funded by the Comunidad Autónoma de Madrid (CAM) (Department of Education and Research), and from RoboCity2030-DIH-CM, Madrid Robotics Digital Innovation Hub (Robótica aplicada a la mejora de la calidad de vida de los ciudadanos, FaseIV; S2018/NMT-4331), funded by Programas de Actividades I+D en la Comunidad de Madrid and cofunded by Structural Funds of the EU

A graphical tuning method for fractional order controllers based on iso-slope phase curves

Fractional order controllers are widely used in the robust control field. As a generalization of the ubiquitous PID controllers, fractional order controllers are able to reach design specifications their integer counterparts cannot, and as a result they outperform them at particular situations. Their main drawback is that generalization of the design tools is not always evident, and therefore tuning this kind of controller is always a new and different challenge. Existing methods often use numerical computation to find the controller parameters that fit the specifications. This paper describes a graphical solution for fractional order controllers, which avoids the solution by nonlinear equations and helps designer to solve the control problem in a very intuitive way. This approach is tested in the servomotors of a real bio-inspired soft neck and results are compared with those obtained from other control strategies. The experiments show that the controller tuned by this method works as expected from a robust controller and that this approach is very competitive compared to other state of the art methods, while offering a more simplified and direct tuning process.Research leading to these results has received funding from HUMASOFT project, with reference DPI2016-75330-P, funded by the Spanish Ministry of Economy and Competitiveness, and from RoboCity2030-DIH-CM Madrid Robotics Digital Innovation Hub, S2018/NMT-4331, funded by "Programas de Actividades I+D en la Comunidad de Madrid" and cofunded by Structural Funds of the EU

Modeling of a soft robotic neck using machine learning techniques

[ES] En este trabajo se aborda el problema del modelado de un cuello robótico blando mediante el uso de diferentes arquitecturas de redes neuronales, estudiando la influencia en los resultados del número de capas de cada red y de su correspondiente función de activación. Se emplearan las funciones de activación Tangente Hiperbólica (TANH) y Unidad Lineal Exponencial (ELU). Los modelos obtenidos se compararan con un modelo basado en Perceptron Multicapa (MLP) de parámetros optimizados, así comocon el modelo cinemático analítico del cuello. Los resultados experimentales obtenidos demostraran la ventaja del empleo de las técnicas de aprendizaje automático para el modelado de sistemas altamente no lineales como el del cuello robótico blando, cuya característica elástica dificulta la formulación de un modelo analítico robusto.[EN] In this paper we address the problem of modeling a soft robotic neck by using different neural network architectures, studying the influence on the results of the number of layers of each network and its corresponding activation function. The Tangent Hyperbolic Tangent (TANH) and Exponential Linear Unit (ELU) activation functions are used. The obtained models are compared with a Multi-Layer Perceptron (MLP) with optimized parameters, as well as with the kinematic model of the neck. The experimental results demonstrate the advantage of using machine learning techniques for modeling highly nonlinear systems such as this soft robotic neck, whose elastic characteristics make it difficult to formulate a robust analytical model. Esta investigación ha recibido financiación del proyecto SOFIA: Articulación blanda inteligente con capacidades de re-configuración y modularidad para plataformas robóticas, con referencia PID2020-13194GB-I00, financiado por el Ministerio de Economía, Industria y Competitividad.Continelli, NA.; Nagua Cuenca, LF.; Monje, CA.; Balaguer, C. (2023). Modelado de un cuello robótico blando mediante aprendizaje automático. Revista Iberoamericana de Automática e Informática industrial. 20(3):282-292. https://doi.org/10.4995/riai.2023.1875228229220

A First Approach to a Proposal of a Soft Robotic Link Acting as a Neck

This paper has been presented at XXXIX Jornadas de Automática.The purpose of this paper is to design a soft robotic neck prototype with two Degrees of Freedom (DOF) and propose a control system based on a fractional order PD controller (FPD). The neck will be able to perform movements of flexion, extension and lateral bending. To achieve these movements, the design is made based on a cable-driven mechanism, with components easy to manufacture in a 3D printer. Simulations are performed to validate the feasibility of the developed parallel robot prototype and the robustness of the proposed control scheme to mass changes at the tip.The research leading to these results has received funding from the HUMASOFT project, with reference DPI2016-75330-P, funded by the Spanish Ministry of Economy and Competitiveness

Test bench for evaluation of a soft robotic link

In this paper we describe the control approaches tested in the improved version of an existing soft robotic neck with two Degrees Of Freedom (DOF), able to achieve flexion, extension and lateral bending movements similar to those of a human neck. The design is based on a cable-driven mechanism consisting of a spring acting as a cervical spine and three servomotor actuated tendons that let the neck to reach all desired postures. The prototype was manufactured using a 3D printer. Two control approaches are proposed and tested experimentally: a motor position approach using encoder feedback and a tip position approach using Inertial Measurement Unit (IMU) feedback, both applying fractional-order controllers. The platform operation is tested for different load configurations so that the robustness of the system can be checked.The research leading to these results has received funding from the HUMASOFT project, with reference DPI2016-75330-P, funded by the Spanish Ministry of Economy and Competitiveness, and from the RoboCity2030-DIH-CM Madrid Robotics Digital Innovation Hub (Robótica aplicada a la mejora de la calidad de vida de los ciudadanos, Fase IV; S2018/NMT-4331), funded by Programas de Actividades I+D en la Comunidad de Madrid and cofunded by Structural Funds of the EU