Many of the current implementations of exoskeletons for the lower extremities are conceived to either augment the user’s load-carrying capabilities or reduce muscle activation during walking. Comparatively little research has been conducted on enabling an exoskeleton to increase the agility of lower-limb movements. One obstacle in this regard is the inertia of the exoskeleton’s mechanism, which tends to reduce the natural frequency of the human limbs. A control method is presented that produces an approximate compensation of the inertia of an exoskeleton’s mechanism. The controller was tested on a statically mounted, single-degree-of-freedom (DOF) exoskeleton that assists knee flexion and extension. Test subjects performed multiple series of leg-swing movements in the context of a computer-based, sprint-like task. A large initial acceleration of the leg was needed for the subjects to track a virtual target on a computer screen. The uncompensated inertia of the exoskeleton mechanism slowed down the transient response of the subjects’ limb, in comparison with trials performed without the exoskeleton. The subsequent use of emulated inertia compensation on the exoskeleton allowed the subjects to improve their transient response for the same task.

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An upper limb exoskeleton is a wearable robotic system that is physically linked to the arm of the human operators and its seven actuated degrees of freedom (DOF) match the seven DOF of the human arm. The stability of such a system is critical given the proximity of its human operator. A new PID controller is developed which guarantee asymptotic stability for this class of robotic manipulators. A simulation was used to assess the system performance given the theoretical results of the controller’s parameters with a unique exoskeleton system (EXO-UL7). The simulation also verify the semi-global asymptotic stability of the system. The proposed methodology eliminates the need of the system’s dynamics model for the purpose of designing the controller. It provides an analytical tool for the controller design that is traditionally preformed experimentally (parameter tuning).

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This paper introduces an approach to performance animation that employs a small number of motion sensors to create an easy-to-use system for an interactive control of a full-body human character. Our key idea is to construct a series of online local dynamic models from a prerecorded motion database and utilize them to construct full-body human motion in a maximum a posteriori framework (MAP). We have demonstrated the effectiveness of our system by controlling a variety of human actions, such as boxing, golf swinging, and table tennis, in real time. Given an appropriate motion capture database, the results are comparable in quality to those obtained from a commercial motion capture system with a full set of motion sensors (e.g., XSens [2009]); however, our performance animation system is far less intrusive and expensive because it requires a small of motion sensors for full body control. We have also evaluated the performance of our system by leave-one-out-experiments and by comparing with two baseline algorithms.

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The resistance compensation, especially the friction compensation in the Bowden cable transmission is a difficult issue to be handled. Aimed to the resistance reduction requirement in the active rehabilitative motion, a resistance compensation control method is proposed. Based on the simplified transmission model, the resistance, including the cable friction as well as the mechanical moment of inertial, is formulated. To realize the compensation, force sensors are used to measure the force exerted by the human fingertip. With the proposed algorithm, the maximum finger-exerted force is reduced to less than one third of before. The experimental result demonstrates the validity of the proposed method.

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Currently, full body exoskeletons still lack movabili-ty in their back and shoulder parts, resulting in limited applicability in, e.g., nursing care. An exoske-letal spine and shoulder mechanism called “exo-spine” has therefore been developed with the purpose of allowing 3 degree of freedom (DOF) spinal motion and 2 DOF shoulder girdle abduction. It consists of a mechanism of vertebras, shoulder blades, and two cables for actuation such that only one motor is requir-ed. Control equations were obtained through measurements and friction analysis. Experiments were performed with a subject wearing the exo-spine in a simplified full body exoskeleton. The wearer was able to lift up to 40 kg using all DOF of the system. From this we confirmed the exo-spine’s 5 DOF movability and lifting performance. Next, the exo-spine will be installed in HAL exoskeletons in order to increase their usabili-ty in health care settings.

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