Electrical motors are reversible machines; they can function as motors or as generators. A motor receives electrical power from a battery and transforms it in torque developing a Counter Electromotive Force CEMF, which opposes the battery. A generator receives mechanical power from a mechanical actuator and transforms it in electrical power developing a Counter Torque, which opposes the actuator. A motor behaves as motor and as generator at the same time. In fact while a motor is ‘motoring’, that is doing mechanical work, it generates CEMF acting as generator, although the CEMF is lower than the battery voltage so the motor acts as a load and absorbs current. In certain situations the CEMF may overcome the battery, in which case the generator component becomes dominant; the motor acts as a generator inverting the direction of its current and forcing it into the battery. The typical situation is the one of a heavy vehicle rolling on a sharp downhill slope and forcing the motor to turn fast enough that the CEMF becomes larger than the battery voltage. As soon as the motor overcomes the battery it inverts the current direction and starts feeding current into the battery, while developing a counter torque that acts as a brake. This phase is called regeneration (recharging of the battery).

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We have developed a feedback controller for a walking simulator composed of a treadmill and a rear projection screen, that keeps the subject centered and visual extent consistent across subjects and time while allowing them to set their own walking pace.

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The gait-locomotor apparatus of the present invention is a device for overcoming impeded locomotion in humans and is aimed at enabling people with handicapped lower limbs to walk. The gait-locomotor apparatus that is wore on a disabled user comprises a brace having a plurality of jointed segments that are adapted to fit the lower body of the disabled user and propulsion means that is adapted to provide relative movement between the plurality of jointed segments. The gait-locomotor apparatus further comprises at least one sensor adapted to monitor the angular position of at least one of the plurality of jointed segments and a control unit that is adapted to supervise the propulsion means and to receive feedback information from the sensors so as to facilitate the brace to perform walking patterns. The disabled user that wears the gait-locomotor apparatus of the present invention is able to steadily stand in a stance position supported by the brace, and is able to walk in various walking patterns using the control unit while fully participating in the process.

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The study investigated the effects of using a lower body prototype exoskeleton (EXO) on static limits of stability and postural sway. Measurements were taken with participants, 10 US Army enlisted men, standing on a force platform. The men were tested with and without the EXO (15 kg) while carrying military loads of 20, 40 and 55 kg. Body lean to the left and right was significantly less and postural sway excursions and maximal range of movement were significantly reduced when the EXO was used. Hurst values indicated that body sway was less random over short-term time intervals and more random over long-term intervals with the EXO than without it. Feedback to the user’s balance control mechanisms most likely was changed with the EXO. The reduced sway and relatively small changes in sway with increasing load weights suggest that the EXO structure may have functioned to provide a bracing effect on the body.

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The Berkeley Lower Extremity Exoskeleton is the first functional ener-getically autonomous load carrying human exoskeleton and was demonstrated at U.C. Berkeley, walking at the average speed of 0.9 m/s (2 mph) while carrying a 34 kg (75 lb) payload. The original published control-ler, called the BLEEX Sensitivity Amplification Controller, was based on positive feedback and was designed to increase the closed loop system sensitivity to its wearer’s forces and torques without any direct measurement from the wearer. This controller was successful at allowing natural and unobstructed load support for the pilot. This article presents an improved control scheme we call “hybrid” BLEEX con-trol that adds robustness to changing BLEEX backpack payload. The walking gait cycle is divided into stance control and swing control phases. Position control is used for the BLEEX stance leg (including the torso and backpack) and a sensitivity amplification controller is used for the swing leg. The controller is also designed to smoothly transition between these two schemes as the pilot walks. With hybrid control, the controller does not require a good model of the BLEEX torso and payload, which is difficult to obtain and subject to change as payload is added and removed. As a tradeoff, the position control used in this method requires the human to wear seven inclinometers to measure human limb and torso angles. These addi-tional sensors require careful design to securely fasten them to the human and increase the time to don and doff BLEEX.

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