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BIONIC
For many years, the idea of a human with bionic mus-cles immediately conjures up science fiction images of a TV series superhuman character that was implanted with bionic muscles and portrayed with strength and speed far superior to any normal human. As fantastic as this idea may seem, recent developments in electroactive polymers (EAP) may one day make such bionics possible. Polymers that exhibit large displacement in response to stimulation that is other than elec-trical signal were known for many years. Initially, EAP received relatively little attention due to their limited actuation capability. However, in the recent years, the view of the EAP materials has changed due to the introduction of effective new materials that significantly surpassed the capability of the widely used piezoelectric polymer, PVDF. As this technology continues to evolve, novel mechanisms that are biolo-gically inspired are expected to emerge. EAP materials can potentially provide actuation with lifelike res-ponse and more flexible configurations. While further improvements in performance and robustness are still needed, there already have been several reported successes. In recognition of the need for cooperation in this multidisciplinary field, the author initiated and organized a series of international forums that are leading to a growing number of research and development projects and to great advances in the field. In 1999, he challenged the worldwide science and engineering community of EAP experts to develop a robotic arm that is actuated by artificial muscles to win a wrestling match against a human opponent. In this pa-per, the field of EAP as artificial muscles will be reviewed covering the state of the art, the challenges and the vision for the progress in future years.

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The first load-bearing and energetically autonomous exoskeleton, called the Berkeley Lower Extremity Exoskeleton (BLEEX) walks at the average speed of two miles per hour while carrying 75 pounds of load. The project, funded in 2000 by the Defense Advanced Research Project Agency (DARPA) tackled four fundamental technologies: the exoskeleton architectural design, a control algorithm, a body LAN to host the control algorithm, and an on-board power unit to power the actuators, sensors and the computers. This article gives an overview of the BLEEX project.

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The first energetically autonomous lower extremity exoskeleton capable of carrying a payload has been demonstrated at U.C. Berkeley. This paper summarizes the mechanical design of the Berkeley Lower Extremity Exoskeleton (BLEEX). The anthropomorphically-based BLEEX has seven degrees of freedom per leg, four of which are powered by linear hydraulic actuators. The selection of the degrees of freedom and their ranges of motion are described. Additionally, the significant design aspects of the major BLEEX components are covered.

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In this paper, we present a method to calculate the intended motion of joints in the human body by analysing EMG signals. Those signals are emitted by the muscles attached to the adjoining bones during their activation. With the resulting intended motion, a leg orthosis can be controlled in realtime to support disabled people while walking or climbing stairs and help patients suffering from the effects of a stroke in their rehabilitation efforts. To allow a variety of different motions, a human body model with physical properties is developed and synchronized with data recorded from the pose sensors. Computing the intended motion is performed by converting calibrated EMG signals to muscle forces which animate the model. The algorithm was evaluated with experiments showing the calculated intended motion while climbing one step of a stair. The algorithm and the experimental results are both shown.

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Energetic autonomy of a hydraulic-based mobile field robot requires a power source capable of both electrical and hydraulic power generation. While the hydraulic power is used for locomotion, the electric power is used for the computer, sensors and other peripherals. An internal combustion engine was used as the prime mover due to the high energy density of gasoline. The primary specification for this hybrid hydraulic-electric power unit (HEPU) is that it must output constant pressure hydraulic power and constant voltage electric power. An on-board computer uses a pressure sensor and a speed sensor to regulate the pressure and voltage by modulating a hydraulic solenoid valve and an engine throttle. The speed regulation also results in a system noise with predictable frequency band which allows for optimal muffler design. A novel characteristic of this power source is its cooling system in which hydraulic fluid is used to cool the engine cylinders. Several hydraulic-electric power units were built and successfully demonstrated on the Berkeley Lower Extremity Exoskeleton (BLEEX) shown on bleex.me.berkeley.edu/bleex.htm. A prototype power unit weighs 27 Kg, outputs 2.3 kW (3.0 hp) hydraulic power at 6.9 MPa (1000 psi), and 220 W of electric power at 15 VDC.

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