Sensorless Load Torque Estimation and Passivity Based Control of Buck Converter Fed DC Motor

Passivity based control of DC motor in sensorless configuration is proposed in this paper. Exact tracking error dynamics passive output feedback control is used for stabilizing the speed of Buck converter fed DC motor under various load torques such as constant type, fan type, propeller type, and unknown load torques. Under load conditions, sensorless online algebraic approach is proposed, and it is compared with sensorless reduced order observer approach. The former produces better response in estimating the load torque. Sensitivity analysis is also performed to select the appropriate control variables. Simulation and experimental results fully confirm the superiority of the proposed approach suggested in this paper

Robotics rehabilitation of the elbow based on surface electromyography signals

Physical rehabilitation based on robotic systems has the potential to cover the patient’s need of improvement of upper extremity functionalities. In this article, the state of the art of resistant and assistive upper limb exoskeleton robots and their control are thoroughly investigated. Afterward, a single-degree-of-freedom exoskeleton matching the elbow–forearm has been advanced to grant a valid rehabilitation therapy for persons with physical disability of upper limb motion. The authors have focused on the control system based on the use of electromyography signals as an input to drive the joint movement and manage the robotics arm. The correlation analysis between surface electromyography signal and the force exerted by the subject was studied in objects’ grasping tests with the purpose of validating the methodology. The authors developed an innovative surface electromyography force–based active control that adjusts the force exerted by the device during rehabilitation. The control was validated by an experimental campaign on healthy subjects simulating disease on an arm, with positive results that confirm the proposed solution and that open the way to future researches

IDENTIFICACIÓN DE PARÁMETROS DE UN MOTOR DC PARA EL CONTROL DE PAR SIN SENSOR DE UNA INTERFAZ HÁPTICA (PARAMETER IDENTIFICATION OF A DC MOTOR FOR SENSOR-FREE TORQUE CONTROL OF A HAPTIC INTERFACE)

Resumen   Las interfaces hápticas han tenido impacto en aplicaciones que buscan la inmersión del usuario, tal es el caso de las áreas de entrenamiento, educación, medicina y entretenimiento. El impacto que tienen en dichas áreas recae en el hecho de que una interfaz háptica permite la interacción, entre el usuario y un ambiente remoto o virtual, por medio del sentido del tacto. En el presente artículo, se propone un método para la identificación experimental de los parámetros constante de par y momento de inercia de un motor de corriente directa. La identificación de ambos parámetros es indispensable para el diseño de un control de par sin sensor basado en un Observador de Perturbaciones (DOB, por sus siglas en inglés), cuando no se cuenta con la información del fabricante. Se implementó un control de par basado en DOB utilizando los parámetros experimentales de control de par y momento de inercia. Dicho control se implementó en un motor DC que a su vez fungió como interfaz háptica, permitiéndole ejercer un par de referencia. Los resultados obtenidos de la identificación de los parámetros permitieron obtener una respuesta del DOB similar a las de un sensor de par.Palabra(s) Clave: control de par, identificación de parámetros, interfaz háptica, motor DC. Abstract   Haptic interfaces have had an impact on applications that seek user immersion, such as training, education, medicine and entertainment. The impact they have on this type of applications lies in the fact that haptic interfaces allow an interaction, between the user and a remote or virtual environment, through the sense of touch. This article proposes a method for the experimental identification of the constant torque and moment of inertia parameters of a DC motor. The identification of these parameters is essential for the design of a sensorless torque control based on a Disturbance Observer (DOB), when the manufacturer's information is not available. The implementation of a torque control based on DOB was achieved using the experimental parameters of torque control and moment of inertia. This control was implemented in a DC motor which served as a haptic interface, allowing to display a reference torque. The parameter identification results allowed to obtain a DOB response corresponding to a torque sensor.Keywords: torque control, parameter identification, haptic interface, DC motor

Diseño y simulación de un control con compensador de los efectos dinámicos y de fricción para exoesqueletos de miembro superior

En el presente trabajo se desarrolló un sistema de control diseñado para exoesqueletos de miembro superior, el cual acompaña el movimiento de un usuario sin emplear sensores dedicados a determinar la intención de su movimiento. El sistema de control compensa los efectos dinámicos y de fricción generados por el peso de los componentes del exoesqueleto y las extremidades del usuario, y el movimiento de este último al usar el exoesqueleto. Además, estima la intención de movimiento del usuario empleando los sensores de los actuadores del exoesqueleto. A partir de esta estimación, el exoesqueleto acompaña los movimientos del usuario, reduciendo el esfuerzo que éste realiza al mover sus extremidades superiores. El sistema de control desarrollado es adaptado para trabajar con componentes comunes y de menor precisión. Las pruebas experimentales, realizadas sobre un modelo conceptual fabricado, demuestran que el sistema de control compensa los efectos dinámicos y de fricción del sistema, estima la intención de movimiento del usuario y acompaña sus movimientos, reduciendo en un 73.2% el esfuerzo realizado por el usuario al mover el modelo conceptual. A partir de los resultados se determina la posibilidad de desarrollar un exoesqueleto más económico pues solo se emplea sensores de corriente y posición, y actuadores de baja precisión.Tesi

パワーアシスト車椅子のモーションコントロールとその実用化 : 安全性・移動性・便宜性向上のための人間親和型制御システム

学位の種別: 課程博士審査委員会委員 : (主査)東京大学教授 堀 洋一, 東京大学教授 池内 克史, 東京大学教授 大崎 博之, 東京大学教授 古関 隆章, 東京大学准教授 馬場 旬平, 東京大学准教授 藤本 博志University of Tokyo(東京大学

Design and Control of a Knee Exoskeleton for Assistance and Power Augmentation

Thanks to the technological advancements, assistive lower limb exoskeletons are moving from laboratory settings to daily life scenarios. This dissertation makes a contribution toward the development of assistive/power augmentation knee exoskeletons with an improved wearability, ergonomics and intuitive use. In particular, the design and the control of a novel knee exoskeleton system, the iT-Knee Bipedal System, is presented. It is composed by: a novel mechanism to transmit the assistance generated by the exoskeleton to the knee joint in a more ergonomic manner; a novel method that requires limited information to estimate online the torques experienced by the ankles, knees and hips of a person wearing the exoskeleton; a novel sensor system for shoes able to track the feet orientation and monitor their full contact wrench with the ground. In particular, the iT-Knee exoskeleton, the main component of the aforementioned system, is introduced. It is a novel six degree of freedom knee exoskeleton module with under-actuated kinematics, able to assist the flexion/extension motion of the knee while all the other joint\u2019s movements are accommodated. Thanks to its mechanism, the system: solves the problem of the alignment between the joint of the user and the exoskeleton; it automatically adjusts to different users\u2019 size; reduces the undesired forces and torques exchanged between the attachment points of its structure and the user\u2019s skin. From a control point of view, a novel approach to address difficulties arising in real life scenarios (i.e. noncyclic locomotion activity, unexpected terrain or unpredicted interactions with the surroundings) is presented. It is based on a method that estimates online the torques experienced by a person at his ankles, knees and hips with the major advantage that does not rely on any information of the user\u2019s upper body (i.e. pose, weight and center of mass location) or on any interaction of the user\u2019s upper body with the environment (i.e. payload handling or pushing and pulling task). This is achieved v by monitoring the full contact wrench of the subject with the ground and applying an inverse dynamic approach to the lower body segments. To track the full contact wrench between the subject\u2019s feet and the ground, a novel add on system for shoes has been developed. The iT-Shoe is adjustable to different user\u2019s size and accommodates the plantar flexion of the foot. It tracks the interactions and the orientation of the foot thanks to two 6axis Force/Torque sensors, developed in-house, with dedicated embedded MEMS IMUs placed at the toe and heel area. Different tasks and ground conditions were tested to validate and highlight the potentiality of the proposed knee exoskeleton system. The experimental results obtained and the feedback collected confirm the validity of the research conducted toward the design of more ergonomic and intuitive to use exoskeletons

The design, validation, and performance evaluation of an untethered ankle exoskeleton

Individuals with neuromuscular impairment from conditions like cerebral palsy face reduced quality of life due to diminishing mobility and independence. Lower-limb exoskeletons, particularly ankle exoskeletons, have potential to aid mobility in impaired populations and augment performance in unimpaired populations and have been extensively researched for the past decade. Few untethered ankle exoskeletons exist due to the difficulty of providing enough mechanical power to offset the weight of the exoskeleton on top of improving human biomechanics and metabolic efficiency. Short battery life is also an obstacle to widespread adoption of untethered ankle exoskeletons in the clinic and at home. In this work, we assess the efficacy of our prototype devices during over-ground walking, design new exoskeleton controllers, develop a new ankle exoskeleton device from the ground up, and evaluate the potential for parallel elasticity to improve the performance of our refined exoskeleton platform. In the first study, we observed that our ankle exoskeleton prototype improved metabolic economy, increased walking speed, and lowered plantarflexor muscle activity in a small cohort of individuals with cerebral palsy during over-ground walking – a significant obstacle to the adoption of exoskeletons in free-living settings. In the second study, we presented a framework for developing adaptive, torque sensor-less open-loop controllers that were competitive with our standard closed-loop controllers in mechanical terms while reducing motor energy consumption and noise. The shortcomings of our prototypes in the first and second chapters inspired a third study to develop new lightweight and modular ankle exoskeleton design with a significantly higher torque and power output and joint-level sensing that improved metabolic economy in both unimpaired and impaired cohorts – our device is the second ever to improve metabolic economy in unimpaired adults. We also presented the first-ever lower-limb exoskeleton usability study. In the final study, we use our new hardware platform to design, validate, and demonstrate that a simple parallel elastic element can significantly improve the performance and battery life of our device. Together, these studies establish our untethered ankle exoskeletons as effective and versatile tools for rehabilitation and human augmentation and support the continued research of exoskeletons in clinical and at-home settings