Kinetic Walking Energy Harvester Design for a Wearable Bowden Cable-Actuated Exoskeleton Robot
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Over the past few decades, wearable exoskeletons of various forms have been developed to assist human activities or for rehabilitation of movement disorders. However, sustainable exoskeletons with efficient energy harvesting devices still have not been fully explored. In this paper, we propose the design of a lightweight wearable Bowden-cable-actuated soft exoskeleton robot with energy harvesting capability. Unlike previous wearable exoskeletons, the presented exoskeleton uses an electromagnetic generator to both harvest biomechanical energy and to output mechanical torque by controlling an operation mode relay switch based on a human's gait. Moreover, the energy-harvesting module also acts as a knee impact absorber for the human, where the effective damping level can be modulated in a controlled manner. The harvested energy is regulated and stored in super capacitors for powering wireless sensory devices when needed. The experimental results show an average of a 7.91% reduction in thigh muscle activity, with a maximum of 3.2 W of electric power being generated during movement downstairs. The proposed design offers important prospects for the realization of lightweight wearable exoskeletons with improved efficiency and long-term sustainability.Exoskeletons have been widely used as walking assistive devices for military and rehabilitation purposes. Many exoskeleton control systems detect users' intention by directly sensing their biological signals such as EMG, EEG, force, etc. Therefore, additional sensors are required, resulting in high cost and inconvenience of putting on and taking off the exoskeleton. In this paper, the user's intention is detected by estimating the torque exerted by the user based on exoskeleton dynamics as well as the current and angle of each joint motor; hence, requirements of sensors are diminished. Moreover, we conduct compliance control by modifying joint velocity commands according to the estimated torque and predefined mechanical admittance of each joint. Experiments are carried out to demonstrate that satisfactory estimation of the user's torque can be achieved by the proposed method.
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Lower limb exoskeleton is a human-machine-electric system that is worn on the outside of the human body and incorporates advanced control, information and communication technologies. It can provide protection, support, and certain auxiliary power for the wearer. In this paper, the mechanical structure of a lower limb exoskeleton is designed and coupled with the human body model for simulation. it verifies the effect of the exoskeleton in reducing human metabolic consumption. First of all, this paper introduces the overall structural design of a lower limb exoskeleton. Secondly, the forward and inverse kinematics of the exoskeleton leg are analyzed, and the working space and Jacobian matrix of the exoskeleton are solved. Finally, the human-machine coupled simulation of the exoskeleton is carried out to analyze the metabolic consumption of the human body under different conditions and verify the power-assisting effect of the exoskeleton on human walking.
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Lower-limb exoskeletons are external mechanical structures that support and assist human users during locomotion. The earliest studies on exoskeletons date back to the 1960s, whereas, over the previous decade, research on powered lower-limb exoskeletons has substantially expanded [1]. Exoskeletons with different architectures have been developed to achieve various goals. Typically, lower-limb exoskeletons can be classified into two broad categories based on their intended use: assisting people who have pathological gaits and augmenting able-bodied users. The first type of exoskeleton is designed to aid individuals with neurological conditions, for example, stroke or spinal cord injury (SCI). With the help of an exoskeleton, these people can complete different tasks that they cannot complete without assistance. For example, the bilateral hip-knee exoskeletons ReWalk [2] and Ekso Bionics [3] enforce predefined reference trajectories determined by a finite-state-machine structure to assist individuals with SCI. The bilateral Wandercraft exoskeleton adopts a hybrid dynamicsbased controller to stabilize dynamically feasible periodic gaits for users with SCI, while allowing them to actively control the exoskeleton speed through upper-body posture.
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Although there have been many lower limb robotic exoskeletons that have been tested for human walking, few devices have been tested for assisting running. It is possible that a pseudo-passive elastic exoskeleton could benefit human running without the addition of electrical motors due to the spring-like behavior of the human leg. We developed an elastic lower limb exoskeleton that added stiffness in parallel with the entire lower limb. Six healthy, young subjects ran on a treadmill at 2.3 m/s with and without the exoskeleton. Although the exoskeleton was designed to provide ~50% of normal leg stiffness during running, it only provided 24% of leg stiffness during testing. The difference in added leg stiffness was primarily due to soft tissue compression and harness compliance decreasing exoskeleton displacement during stance. As a result, the exoskeleton only supported about 7% of the peak vertical ground reaction force. There was a significant increase in metabolic cost when running with the exoskeleton compared with running without the exoskeleton (ANOVA, P < .01). We conclude that 2 major roadblocks to designing successful lower limb robotic exoskeletons for human running are human-machine interface compliance and the extra lower limb inertia from the exoskeleton.
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In recent years, most countries have experienced a shift toward aging population, leading to a decline in the working population; thus, an increased physical burden on workers results. The use of powered exoskeletons is one approach to reduce physical stresses on the bodies of workers and elderly people. However, conventional powered exoskeletons have many sensors and actuators mounted on them, resulting in problems associated with their high price, high weight, etc. In this paper, we introduce a new high-efficiency reduction gearbox, which is being researched and developed in our laboratory as a substitute for conventional actuators, and present the results of its attempted assist control without a torque sensor. It was found that the user's torque can be estimated with high accuracy without using a torque sensor by using a highly efficient gearbox with 1/102.14 reduction ratio. In addition, we performed motion identification using a nonlinear support vector machine with the aim of assist control with reduced discomfort on the body by suppressing vibrations.
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Exoskeleton is a new intelligent wearable robot developed in recent years. Users work with exoskeleton, which can provide assistant support and power as real human bones. In this paper, an integrative joint structure used for lower limb exoskeleton is proposed. By using of this integrative joint, a lower limb exoskeleton structure is designed. In order to judge walking intention of uses, some exoskeleton sensors are designed for the lower limb exoskeleton. This paper sets up electrical system and control system. One lower limb exoskeleton prototype is manufactured. For the purpose of testifying the performance of the lower limb exoskeleton, some experiments have been done.
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