Mechanical design and friction modelling of a cable-driven upper-limb exoskeleton

This paper presents a lightweight and low-inertia cable-driven upper-limb exoskeleton powerful enough to meet the requirements for activities of daily living. It presents the mechanical design, kinematic structure,the underlying actuation system, sensors, other electronic components as well as the controller of the exoskeleton. The extensive effect of friction on cable-driven designs, such as the one presented in this paper, requires proper mathematical modelling for controller design. Thus, we propose a current actuator model that describes the relationship between the motor current, velocity, and external load. The model relies on an underlying Stribeck+Coulomb friction representation and an additional parameter that modifies its Coulomb friction representation with an offset to represent adhesion between a cable and sheath. The model has been validated based on experimental data collected with the exoskeleton. The results show that the proposed model better captures the non-linear behaviour of the exoskeleton’s actuation system, increasing overall descriptive performance by 15%. However, adding the adhesion offset to extend the relation of static friction, does not improve the model

Mechanical Design and Kinematic Modeling of a Cable-Driven Arm Exoskeleton Incorporating Inaccurate Human Limb Anthropomorphic Parameters

Compared with conventional exoskeletons with rigid links, cable-driven upper-limb exoskeletons are light weight and have simple structures. However, cable-driven exoskeletons rely heavily on the human skeletal system for support. Kinematic modeling and control thus becomes very challenging due to inaccurate anthropomorphic parameters and flexible attachments. In this paper, the mechanical design of a cable-driven arm rehabilitation exoskeleton is proposed to accommodate human limbs of different sizes and shapes. A novel arm cuff able to adapt to the contours of human upper limbs is designed. This has given rise to an exoskeleton which reduces the uncertainties caused by instabilities between the exoskeleton and the human arm. A kinematic model of the exoskeleton is further developed by considering the inaccuracies of human-arm skeleton kinematics and attachment errors of the exoskeleton. A parameter identification method is used to improve the accuracy of the kinematic model. The developed kinematic model is finally tested with a primary experiment with an exoskeleton prototype

A Shoulder Mechanisms for Assisting Upper Arm Function With Distally Located Actuators

This thesis presents a new design for a shoulder assistive device based on a modified double parallelogram linkage (DPL). The DPL allows for active support of the arm motion in the sagittal plane, while enabling the use of a distally located motor that can be mounted around the user’s waist to improve the weight distribution. The development of the DPL provides an unobtrusive mechanism for assisting the movement of the shoulder joint through a wide range of motion. This design contains three degrees-of-freedom (DOFs) and a rigid structure for supporting the arm. The modified DPL uses a cable-driven system to transfer the torque of the motor mounted on the user’s back through the links to the arm. The proposed design assists with the flexion/extension of the arm, while allowing the adduction/abduction and internal/external rotations to be unconstrained. A kinematic analysis of the cable system and linkage interaction is presented, and a prototype is fabricated to verify the proposed concept

Diseño de un exoesqueleto para uso industrial de miembros superiores a base de materiales reciclados

En la industria colombiana, las labores se realizan de manera manual en la mayoría de los casos. Algunas de estas tareas pueden potencialmente causar trastornos músculo esqueléticos en los trabajadores generando costos para las empresas, asociados con el tratamiento de estos y el ausentismo laboral. A pesar de que la solución más eficiente a este problema es la automatización, su implementación puede representar altos costos que son difíciles de pagar por algunas empresas, especialmente por las PYMES. Debido a esta problemática, la solución puede estar enfocada en utilizar herramientas que mejoren las condiciones laborales, entre las cuales se encuentran los exoesqueletos, los cuales pueden disminuir la carga muscular en miembros superiores cuando se ejecutan tareas que requieren de posturas como las que se van a analizar en el presente proyecto. El análisis estará enfocado principalmente en el levantamiento de los brazos por encima de los hombros durante un tiempo prolongado dentro de la jornada laboral. Para la medición de esta carga muscular se plantea usar electromiografía (EMG) en la realización de una tarea por una persona en un puesto de trabajo simulado, y posteriormente hacer una comparación de esta con dicha actividad presentada utilizando un exoesqueleto de miembros superiores, adquirido por la Pontificia Universidad Javeriana y un prototipo del dispositivo de diseño propio. Se espera que genere una disminución de la carga muscular en comparación con la situación actual de trabajo, en la cual no se utiliza ningún dispositivo de asistencia.Ingeniero (a) IndustrialPregrad

Design, construction and control of an exo-suit for upper limb rehabilitation and assistance

This Final Master’s Thesis (FMT) is part of a wider project carried out at the University of Alicante (UA) which deals with the design, construction and control of an exo-suit for the rehabilitation and assistance of the upper limb. It is the continuation of the FMT carried out by Domingo Miguel Izquierdo Afonso which deals with the design and simulation of the drive system of an exo-suit for the assistance-rehabilitation of the upper limb. The main objective of the master’s final dissertation, as its title implies, is to design and build the first prototype of an exo-suit for the elbow. To this end, all the necessary parts such as the battery, the motor, types of cables for actuation, etc., will have to be chosen and assembled. In addition, this exoskeleton will be made on an originally passive orthosis to facilitate its construction. Robotics focused on the rehabilitation of patients is an innovative technology which is also used for exoskeletons for workers in industry in order to considerably reduce the number of industrial accidents, which without exoskeletons would require further rehabilitation. The exosuit that will be discussed throughout this project consists of a cable-pulley mechanism system to move the elbow without the need for excessive force, perfect for elbow rehabilitation, for workers who have to lift weights and make repetitive movements during the working day or for people who, due to various illnesses, need assistance in everyday life

Adaptive backlash compensation in upper limb soft wearable exoskeletons

A new frontier of assistive devices aims at designing exoskeletons based on fabric and flexible materials for applications where kinematic transparency is the primary requirement. Bowden-cable transmission is the widely employed solution in most of the aforementioned applications due to advantages in durability, lightweight, safety, and flexibility. The major advantages of soft assistive devices driven by bowden-cable transmissions can be identified in the superior ergonomics and wearability, allowing users to freely move and allocating the actuation stages far from the end-effector. However, control accuracy in bowden-cable transmission presents some intrinsic limitation due to nonlinearities such as static and dynamic friction, occurring between the cables and the bowden sheaths, and backlash hysteresis. Friction and backlash effects are known to be related to the curvature of the flexible sheath, which is not directly measurable and can vary during human motion. In this paper we describe our new wearable exosuit for upper limb assistance and in particular we introduce a mathematical model for backlash hysteresis compensation. The implementation of a nonlinear adaptive controller is described in detail and experimentally tested on the proposed design as a backlash compensation strategy: results report that the adaptive controller improves the accuracy in position tracking (i.e. RMSE in trajectory tracking ≈1∘) by compensating for time-varying backlash and continuously updating the model parameters. The backlash hysteresis model and the proposed control scheme are validated first on a custom-designed test bench and then applied to control the soft exoskeleton worn by a subject affected by bilateral brachial plexus injury

Kinematics and Robot Design IV, KaRD2021

This volume collects the papers published on the special issue “Kinematics and Robot Design IV, KaRD2021” (https://www.mdpi.com/journal/robotics/special_issues/KaRD2021), which is the forth edition of the KaRD special-issue series, hosted by the open-access journal “MDPI Robotics”. KaRD series is an open environment where researchers can present their works and discuss all the topics focused on the many aspects that involve kinematics in the design of robotic/automatic systems. Kinematics is so intimately related to the design of robotic/automatic systems that the admitted topics of the KaRD series practically cover all the subjects normally present in well-established international conferences on “mechanisms and robotics”. KaRD2021, after the peer-review process, accepted 12 papers. The accepted papers cover some theoretical and many design/applicative aspects

Bio-Inspired Soft Artificial Muscles for Robotic and Healthcare Applications

Soft robotics and soft artificial muscles have emerged as prolific research areas and have gained substantial traction over the last two decades. There is a large paradigm shift of research interests in soft artificial muscles for robotic and medical applications due to their soft, flexible and compliant characteristics compared to rigid actuators. Soft artificial muscles provide safe human-machine interaction, thus promoting their implementation in medical fields such as wearable assistive devices, haptic devices, soft surgical instruments and cardiac compression devices. Depending on the structure and material composition, soft artificial muscles can be controlled with various excitation sources, including electricity, magnetic fields, temperature and pressure. Pressure-driven artificial muscles are among the most popular soft actuators due to their fast response, high exertion force and energy efficiency. Although significant progress has been made, challenges remain for a new type of artificial muscle that is easy to manufacture, flexible, multifunctional and has a high length-to-diameter ratio. Inspired by human muscles, this thesis proposes a soft, scalable, flexible, multifunctional, responsive, and high aspect ratio hydraulic filament artificial muscle (HFAM) for robotic and medical applications. The HFAM consists of a silicone tube inserted inside a coil spring, which expands longitudinally when receiving positive hydraulic pressure. This simple fabrication method enables low-cost and mass production of a wide range of product sizes and materials. This thesis investigates the characteristics of the proposed HFAM and two implementations, as a wearable soft robotic glove to aid in grasping objects, and as a smart surgical suture for perforation closure. Multiple HFAMs are also combined by twisting and braiding techniques to enhance their performance. In addition, smart textiles are created from HFAMs using traditional knitting and weaving techniques for shape-programmable structures, shape-morphing soft robots and smart compression devices for massage therapy. Finally, a proof-of-concept robotic cardiac compression device is developed by arranging HFAMs in a special configuration to assist in heart failure treatment. Overall this fundamental work contributes to the development of soft artificial muscle technologies and paves the way for future comprehensive studies to develop HFAMs for specific medical and robotic requirements