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ABSTRACT: A number of studies discuss the design and control of various exoskeleton mechanisms, yet relatively few address the effect on the energy expenditure of the user. In this paper we discuss the effect of a performance augmenting exoskeleton on the metabolic cost of an able-bodied user/pilot during periodic squatting. We investigated whether an exoskeleton device will significantly reduce the metabolic cost and what is the influence of the chosen device control strategy. By measuring oxygen consumption, minute ventilation, heart rate, blood oxygenation and muscle EMG during 5 minute squatting series, at one squat every 2 seconds, we show the effects of using a prototype robotic knee exoskeleton under three different noninvasive control approaches: gravity compensation approach, position based approach and a novel oscillator based approach. The latter proposes a novel control which ensures synchronization of the device and the user. Statistically significant decrease in physiological responses can be observed when using the robotic knee exoskeleton under gravity compensation and oscillator based control. On the other hand, the effects of position based control were not significant in all parameters although all approaches significantly reduced the energy expenditure during squatting.
IEEE transactions on bio-medical engineering 01/2013; · 2.15 Impact Factor
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ABSTRACT: We address the problem of extracting the fundamental frequency of an arbitrary periodic or quasi-periodic signal for application in robotic tasks. We focus on controlling periodic robotic movement by extracting the frequency of human movement by using surface electromyography (EMG), a technique by which muscle action potentials are gathered by electrodes placed on the skin. However, since the EMG signal is quasi-periodic with a lot of frequency components and noise, it is difficult to determine the frequency and phase of the measured limb motion. We propose to use nonlinear dynamical systems capable of extracting the frequency and the phase from an unknown periodic signal with an arbitrary waveform. The method uses a whole Fourier series representation in a feedback loop. It is capable of extracting the frequency and the phase of an unknown periodic signal in real-time, without any additional signal processing or preprocessing. Combining this method with an output dynamic system based on dynamic movement primitives, which generate the desired trajectory, allows synchronization between human muscles actions and some other system actions like robot motion or electrical neuromuscular stimulator activation.
Robotics and Automation (ICRA), 2011 IEEE International Conference on; 06/2011
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ABSTRACT: In this paper we describe the use of a standard game console joystick, namely the Nintendo WIIMOTE, for an active real-time 3D marker tracking. We show the ease of applicability of inexpensive and robust standard game controllers for 3D object tracking, e.g. to track an infrared source in 3D space. Recovering the 3D information using stereo vision is still one of the major research areas in computer vision and has given rise to a great deal of literature in the recent past. In this paper we present the method for calibrating a WIIMOTE stereo pair without knowing any parameters of the build-in infrared cameras in advance. The results are two matrices which includes both the intrinsic and extrinsic parameters for left and right cameras. The comparison between the stereo and the mono WIIMOTE tracking system is presented. Furthermore, to demonstrate the use of the WIIMOTE stereo system we considered the task of throwing a ball with robotic hand, to the target identified with an infrared source. The throwing task was divided into two separate parts: the tracking part and the throwing part.
Robotics in Alpe-Adria-Danube Region (RAAD), 2010 IEEE 19th International Workshop on; 07/2010
