This paper proposes a control method for a power assist system which attenuates the load force. In the system, the question of how to select a power assist ratio is important. This ratio must be selected with consideration of the maximum torque of each actuator used in the system, otherwise the actuator saturation may occur and cause the lack of the manoeuvrability and instability. To avoid such saturation problems, we propose a new control method which, after dividing an operated load into gravity load and dynamic load, selects a power assist ratio for the dynamic by considering the remaining actuator torque after the ratio for the gravity load is determined basing on the operator’s capability. The control law is formulated for a single axis power assist system and the effectiveness of the method is confirmed by experiments

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To support an Oak Ridge National Laboratory programs exoskeleton project, a unique multi-axis foot force/torque sensor was constructed and tested that has biomedical application such as clinical gait analysis. The challenging aspect of this multi-axis force sensor is that it had to conform to the bending of the human foot, withstand high impact loads, have high force sensitivity, feel comfortable to the human wearer, be integrated into a military style boot, measure the forces on the human foot when either the ball or the heel of the foot is in contact with the ground, respond to both positive and negative loading and have a low overall height and weight. This paper describes the design and testing of this unique sensor.

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The skills of humans performing tasks can be evaluated using Fitts’ law, which is described by a straight line in the coordinate system of execution time and task difficulty index. The inverse of the slope of the straight line is called the execution capacity of a human. The aforementioned variables can be calculated from experimental data collected for a task. Experimental data were collected in the task in which a peg attached to the hand of an exoskeleton guided by a human arm was placed into a hole. Indeed, we have determined the mean and standard deviations for individual performances and also for the performances of a group of individuals. Thus, the numerical values calculated to describe the skills of an individual form a basis for comparison of the skills of the individuals. Our study introduces a novel probabilistic skill index to evaluate skills of operators performing tasks characterized by two or more variables. The probabilistic skill index provides a broader basis for the skill evaluations of the individuals. Moreover, the skills of the individuals performing tasks can be compared objectively by using the probabilistic skill index introduced

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A power assist walking leg is designed for enhancing strength and endurance during walking, it can be also applied to one whose legs are injured or who has difficulty in walking because of aging, paralysis and amputation. In this paper, we intend to introduce a concept of power assist walking support system and its fundamental control strategy using the information of human-robot interaction force. The whole system must be simple for user, i.e. the user can manipulate the walking support system easily. In order to make the system work smoothly, it must understand the user’s intent through human-robot interaction force and the joint angle. Therefore, we propose tentatively a strategy using human-robot interaction force between the assist walking exoskeletonand human legs. Correlative experimental results show the effectiveness of the control strategies.

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Two adaptively combined gyro and triaxial accelerometer arrays of commercial-grade Micro Electro-Mechanical Systems (MEMS) inertial sensors and a real-time embedded algorithm suite significantly enhance accuracy over that of single commercial-grade devices. Denoised sensor data is combined with a Kalman-filter bias compensation algorithm to achieve better than 0.1 degree/hour in-run gyro bias stability (standard deviation). One denoise-filtered triaxial accelerometer sensor array provides better than 30µg accelerometer bias stability. The hardware is embedded in an exoskeleton that maintains accurate fine alignment adjustments and provides protection when in rugged environments. Analysis of results measured from Allan variance computations of real-time data from several different IMU hardware units demonstrates that each of three orthogonally positioned precision gyro arrays, and their associated processing, achieve less than 0.03 deg integrated angle drift over 5 hours. New IMU hardware is now in fabrication for delivery in early 2010, when received, we expect to overcome the limits of the present hardware design to produce additional significant improvements. The size, weight, and power of these new IMU’s are suitable for man-portable, hand-held systems, UAVs, and munitions systems. Early work for this technology was first published at ION/PLANS 2008.

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