Esta dissertação apresenta o projeto e a construção de atuadores elásticos em série para o acionamento das juntas de um exoesqueleto para membros inferiores, baseado em uma órtese comercial. Inicialmente, considerou-se como dispositivo de testes a parte do exoesqueleto referente à junta do tornozelo, ou seja, a construção de uma órtese tornozelo-pé ativa. Atuadores elásticos em série são considerados neste trabalho, pois tais dispositivos apresentam características ideais para a sua utilização em órteses ativas: controle de força, controle de impedância (possibilidade de impedância baixa), absorção de impactos, baixo atrito e largura de banda que se aproxima da movimentação muscular. Um primeiro protótipo do atuador elástico em série foi construído e resultados experimentais de controle de força, impedância e posição foram obtidos com sucesso, através de uma interface de acionamento e controle entre o atuador, os sensores (encoders e sensores de força) e o computador. Também foi construída uma órtese tornozelo-pé ativa acionada pelo atuador elástico em série construído, sendo apresentados os primeiros resultados experimentais obtidos com este dispositivo. / This dissertation deals with the design and construction of series elastic actuators for driving the joints of an exoskeleton for lower limbs, based on a commercial orthosis. Initially, it was considered the construction of the exoskeleton\'s ankle joint, that is, the construction of an active ankle-foot orthosis. Series elastic actuators are considered in this work since these devices have ideal characteristics for use in active orthoses: force control, impedance control (possibility of low impedance), impact absorption, low friction and bandwidth that approximates the muscle movement. A first prototype of the series elastic actuator was constructed and experimental results of force, impedance, and position control were successfully obtained trough of a control interface between the actuators, the sensors (encoders and force sensors) and the computer. Also, an active ankle-foot orthosis, driven by the series elastic actuator, was constructed and the first experimental results achieved with this device are presented.

"This thesis presents an extension of sensitive manipulation which transforms tactile sensors away from end effectors and closer to whole body sensory feedback. Sensitive manipulation is a robotics concept which more closely replicates nature by employing tactile sensing to interact with the world. While traditional robotic arms are specifically designed to avoid contact, biological systems actually embrace and intentionally contact the environment. This arm is inspired by these biological systems and therefore has compliant joints and a tactile shell surrounding the two primary links of the arm. The manipulator has also been designed to be capable of both industrial and humanoid style manipulation. There are an untold number of applications for an arm with increased tactile feedback primarily in dynamic environments such as in industrial, humanoid, and prosthetic applications. The arm developed for this thesis is intended to be a desktop research platform, however, one of the most influential applications for increased tactile feedback is in prosthetics which are operate in ever changing and contact ridden environments while continuously interacting with humans. This thesis details the simulation, design, analysis, and evaluation of a the first four degrees of freedom of a robotic arm with particular attention given to the design of modular series elastic actuators in each joint as well as the incorporation of a shell of tactile sensors. "

Esta dissertação apresenta o projeto e a construção de atuadores elásticos em série para o acionamento das juntas de um exoesqueleto para membros inferiores, baseado em uma órtese comercial. Inicialmente, considerou-se como dispositivo de testes a parte do exoesqueleto referente à junta do tornozelo, ou seja, a construção de uma órtese tornozelo-pé ativa. Atuadores elásticos em série são considerados neste trabalho, pois tais dispositivos apresentam características ideais para a sua utilização em órteses ativas: controle de força, controle de impedância (possibilidade de impedância baixa), absorção de impactos, baixo atrito e largura de banda que se aproxima da movimentação muscular. Um primeiro protótipo do atuador elástico em série foi construído e resultados experimentais de controle de força, impedância e posição foram obtidos com sucesso, através de uma interface de acionamento e controle entre o atuador, os sensores (encoders e sensores de força) e o computador. Também foi construída uma órtese tornozelo-pé ativa acionada pelo atuador elástico em série construído, sendo apresentados os primeiros resultados experimentais obtidos com este dispositivo. / This dissertation deals with the design and construction of series elastic actuators for driving the joints of an exoskeleton for lower limbs, based on a commercial orthosis. Initially, it was considered the construction of the exoskeleton\'s ankle joint, that is, the construction of an active ankle-foot orthosis. Series elastic actuators are considered in this work since these devices have ideal characteristics for use in active orthoses: force control, impedance control (possibility of low impedance), impact absorption, low friction and bandwidth that approximates the muscle movement. A first prototype of the series elastic actuator was constructed and experimental results of force, impedance, and position control were successfully obtained trough of a control interface between the actuators, the sensors (encoders and force sensors) and the computer. Also, an active ankle-foot orthosis, driven by the series elastic actuator, was constructed and the first experimental results achieved with this device are presented.

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This thesis focuses on making improvements to time-delayed teleoperation systems, with both direct and semi-autonomous haptic control, by addressing the challenges associated with force-position (F-P) predictive architectures. As the time delay from the communication channel increases, system stability and performance degrade. Previously, solutions focused on communication channel stability and environment force estimation methods that primarily rely on linearization of the Hunt-Crossley (HC) contact model. These result in a loss of transparency in the system and limiting use cases from linearization assumptions. Moreover, semi-autonomous solutions aimed at decreasing user effort and automating subtasks, such as obstacle avoidance and user guidance, require training or singularly focus on joint space tasks. This work addresses the shortcomings of the aforementioned methods by refocusing on system components to achieve more favorable dynamics during environment contact with the use of a series elastic actuator (SEA), investigating alternative HC parameter estimation techniques, and synthesizing an assistive semi-autonomous control framework that predicts user intention recognition and automates gross motion tasks. Experimental results with a remote SEA demonstrate improved performance with stiff environments in delays of up to two seconds round trip time. The coupling of the force and position through the actuator along with simultaneous sensing capabilities also show robustness for contact with soft environments. Further improvements with soft environment contact are achieved through HC parameter estimation, with smooth parameter update switching using a Sigmoid function. A novel application of Chebyshev polynomial approximation for adaptive parameter estimation of the HC model was also proposed. This approach provides control via backstepping with adaptive parameter estimation using Lyapunov methods. Additionally, this method reduces excitation requirements by using nonlinear swapping and the data accumulation concept to guarantee parameter convergence. A simulated teleoperation system demonstrates the effectiveness of this approach and initial results from experiment show promise for this approach in practice. Finally, a user study involving a pick and place task produced favorable results for the proposed semi-autonomous framework which significantly reduced task completion times. / Master of Science / Teleoperated systems are powerful solutions for remotely executing tasks in situations where autonomous solutions are not robust enough and/or user knowledge is desired for a task. However, teleoperation performance and stability is degraded by delays in the communication channel. A common way to deal with time delay is to use a predictive controller on the local side to cancel out the delay by knowing the remote side dynamics. Previous approaches have focused on stabilizing the communication channel or the use of estimators and observers to better capture the remote side dynamics. The drawback of these approaches is that they achieve stability at the expense of system transparency, leading to divergence in the force and position matching between the master and remote side. Many of the methods for environment force estimation involves linearizing contact models, creating limitations in their application. Moreover, semi-autonomous solutions aimed at decreasing user effort and automating subtasks such as obstacle avoidance and user guidance require training data sets for the algorithm or only focus individually on joint space tasks. This thesis addresses the shortcomings of the aforementioned methods by refocusing on system components to achieve more favorable dynamics using a series elastic actuator (SEA) while interacting with the environment, investigating nonlinear and linear contact model estimation methods for identifying parameters of the Hunt-Crossley (HC) model, and synthesising an assistive semi-autonomous control framework that predicts user intention for task execution. Experimental results for the use of an SEA demonstrate improved performance with stiff environments in delays of up to two seconds round trip time (RTT). The coupling of the force and position through the actuator along with simultaneous sensing capabilities also showed robustness for contact with soft environments. Various estimation methods for HC parameter identification was investigated to improve the local side model. A novel application of Chebyshev polynomial approximation of the HC model with adaptive parameter estimation was also proposed to provide control along with decreasing the excitation requirements by using backsteping control with nonlinear swapping and the data accumulation concept. A simulated teleoperation system demonstrated the effectiveness of this approach with a smooth paramater update transition. Initial results from experiment also show promise for this approach in practice. Finally, a user study involving a pick and place task produced favorable results for the proposed semi-autonomous framework which significantly reduced task completion times.

Recent advancements in actuator technologies, computation, and control have led to major leaps in capability and have brought humanoids ever closer to being feasible solutions for real-world applications. As the capabilities of humanoids increase, they will be called on to operate in unstructured real world environments. This realization has driven researchers to develop more dynamic, robust, and adaptable robots. Compared to state-of-the-art robots, biological systems demonstrate remarkably better efficiency, agility, adaptability, and robustness. Many recent studies suggest that a core principle behind these advantages is compliance, yet there are very few compliant humanoids that have demonstrated successful walking. The work presented in this dissertation is based on several years of developing novel actuators for two full-scale linearly actuated compliant humanoid robots, SAFFiR and THOR. Both are state-of-the-art robots intended to operate in the extremely challenging real world scenarios of shipboard firefighting and disaster response. The design, modeling, and control of actuators in robotics application is critical because the rest of the robot is often designed around the actuators. This dissertation seeks to address two goals: 1) advancing the design of compliant linear actuators that are well suited for humanoid applications, and 2) developing a better understanding of how to design and model compliant linear actuators for use in humanoids. Beyond just applications for compliant humanoids, this research tackles many of the same design and application challenges as biomechanics research so it has many potential applications in prosthetics, exoskeletons, and rehabilitation devices. / Ph. D.

Exoskeletons and humanoid robots require high-power, low-weight, and back-driveable actuators. This paper describes the design and analysis of a high-force linear series elastic actuator for a lower body exoskeleton. The actuator is powered by two motors and utilize a liquid cooling system to increase its maximum continuous torque. The actuator is capable of outputting a maximum continuous force of 4800N and a maximum speed of 0.267 m/s with a maximum continuous motor current of 18A. The Titanium leaf spring was used in the actuator to provide compliance. The spring has a median stiffness of 587 N/mm with standard deviation of 38 N/mm, validated by experiments. Dynamic model was created to analyze the normal modes and can be used for developing model-based controllers. / Master of Science / Compliant Linear actuators with ball screw have become popular for humanoids robots and exoskeleton. The use of ball screw lead to high efficiency, high gear ratio and high back-drivability. The compliance or the ''softness'' of the actuator comes from Titanium leaf spring, which can storage energy during gait cycle and protect motor and the ball screw from impacts of walking. The custom liquid cooling system improves the force density for the actuator. Beam theory analysis, heat transfer analysis, and dynamics analysis were performed to provides insights for the actuator system.

Com os avanços significativos no campo da medicina, cada vez mais a tecnologia robótica vem sendo empregada no tratamento de indivíduos que sofreram alguma deficiência física. Esta dissertação apresenta o desenvolvimento de um Atuador Elástico em Série Compacto, aqui denominado AESC, e suas possíveis utilizações no campo da reabilitação robótica. Os controles implementados foram: Controle de Posição, Controle de Força e Controle de Impedância. Atuadores elásticos em série são utilizados, pois tais dispositivos apresentam características ideais para a utilização em equipamentos voltados à reabilitação: impedância controlável possibilidade de impedância baixa), baixo atrito e largura de banda que se aproxima do padrão de movimento humano. Aplicações do AESC para reabilitação de indivíduos que tenham sofrido lesão cerebral ou lesões ortopédicas e traumatológicas são apresentadas. Elas se mostram como um recurso para incrementar a reabilitação relacionada ao ganho de força muscular do tornozelo, bem como aumento da amplitude de movimento. A Plataforma Robótica de Reabilitação de Tornozelo utiliza uma interface baseada em jogos para o auxílio da reabilitação, tornando o processo mais lúdico estimulando a aprendizagem. O Exoesqueleto para Membros Inferiores simula o caminhar humano, auxiliando pessoas que tenham sofrido Acidente Vascular Encefálico. / With significant advances in the medical field, more and more robotic technology has been used to treat individuals who have suffered a physical disability. This dissertation presents the development of a Compact Series Elastic Actuator, named here as AESC, and its possible uses on the field of robotic rehabilitation. The controls types implemented include: Position Control, Force Control and Impedance Control. Series elastic actuators are used because such devices have ideal characteristics for use in equipments for rehabilitation: controllable impedance (possibility of low impedance), low friction and bandwidth that approaches the human movement. Applications of the AESC for rehabilitation of individuals who have suffered brain or orthopedic damages are presented. They appear as a resource to enhance the rehabilitation related to gain in muscle strength of the ankle muscles, as well as to increase the range of motion. The Robotic Platform of Ankle Rehabilitation uses a game-based interface for rehabilitation, to make the rehabilitation process more playful. The Exoskeleton for Lower Limbs simulates human walking, helping people who have suffered stroke.

Com os avanços significativos no campo da medicina, cada vez mais a tecnologia robótica vem sendo empregada no tratamento de indivíduos que sofreram alguma deficiência física. Esta dissertação apresenta o desenvolvimento de um Atuador Elástico em Série Compacto, aqui denominado AESC, e suas possíveis utilizações no campo da reabilitação robótica. Os controles implementados foram: Controle de Posição, Controle de Força e Controle de Impedância. Atuadores elásticos em série são utilizados, pois tais dispositivos apresentam características ideais para a utilização em equipamentos voltados à reabilitação: impedância controlável possibilidade de impedância baixa), baixo atrito e largura de banda que se aproxima do padrão de movimento humano. Aplicações do AESC para reabilitação de indivíduos que tenham sofrido lesão cerebral ou lesões ortopédicas e traumatológicas são apresentadas. Elas se mostram como um recurso para incrementar a reabilitação relacionada ao ganho de força muscular do tornozelo, bem como aumento da amplitude de movimento. A Plataforma Robótica de Reabilitação de Tornozelo utiliza uma interface baseada em jogos para o auxílio da reabilitação, tornando o processo mais lúdico estimulando a aprendizagem. O Exoesqueleto para Membros Inferiores simula o caminhar humano, auxiliando pessoas que tenham sofrido Acidente Vascular Encefálico. / With significant advances in the medical field, more and more robotic technology has been used to treat individuals who have suffered a physical disability. This dissertation presents the development of a Compact Series Elastic Actuator, named here as AESC, and its possible uses on the field of robotic rehabilitation. The controls types implemented include: Position Control, Force Control and Impedance Control. Series elastic actuators are used because such devices have ideal characteristics for use in equipments for rehabilitation: controllable impedance (possibility of low impedance), low friction and bandwidth that approaches the human movement. Applications of the AESC for rehabilitation of individuals who have suffered brain or orthopedic damages are presented. They appear as a resource to enhance the rehabilitation related to gain in muscle strength of the ankle muscles, as well as to increase the range of motion. The Robotic Platform of Ankle Rehabilitation uses a game-based interface for rehabilitation, to make the rehabilitation process more playful. The Exoskeleton for Lower Limbs simulates human walking, helping people who have suffered stroke.

This thesis presents the design of uBot-7, the latest version of a dexterous mobile manipulator. This platform has been iteratively developed to realize a high performance-to-cost dexterous whole body manipulator with respect to mobile manipulation. The semi-anthropomorphic design of the uBot is a demonstrated and functional research platform for developing advanced autonomous perception, manipulation, and mobility tasks. The goal of this work is to improve the uBot’s ability to sense and interact with its environment in order to increase the platforms capability to operate dexterously, through the incorporation of joint torque feedback, and safely, through the implementation of passive and active compliance. This is accomplished through incorporating series elastic actuators in its arms and torso joints, improving the mechanical design to reduce backlash, and incorporating impedance controllers in the robot. The focus of this thesis is the development of the mechanical, sensor, and controller design for the uBot-7 platform. An impedance controller is developed and evaluated on a bench top prototype series elastic actuator.