Creation Problems of Control System of the Lower Limbs Exoskeleton with Hydraulic Cylinders

• Main Authors: E. K. Lavrovsky, E. V. Pismennaya, P. A. Komarov
• Format: Article
• Language: Russian
• Published: MGTU im. N.È. Baumana 2015-01-01
• Series: Nauka i Obrazovanie
• Subjects: passive and active exoskeleton; biomechanical model of human exoskeleton; exoskeleton control; desired torques
• Online Access: http://technomag.edu.ru/jour/article/view/229

<p>The paper considers a problem of bio-mechanism control i.e. control of integrated human - exoskeleton, with its walking on the level horizontal surface on the flat regular single support foot.</p><p>The exoskeleton is a metal rod structure having the same length as a human, but with different mass inertial characteristics. The exoskeleton is able to repeat the human-driven movement. There is a point load in the "backpack" behind human’s back. Elastic straps support the contact between the human body and the exoskeleton in eight points.</p><p>The article explores the behavior of the exoskeleton in two modes: passive and active. The passive mode characterizes the behavior of the exoskeleton only under the action of forces generated by the human movement in the "comfortable" walking gait. As to the active mode, a difference from the passive one is that in the knee joints of the exoskeleton there are locomotors (propulsions) capable of developing the desired torques.</p><p>Active mode investigation was based on the full dynamics equations. Exoskeleton control provided the desired movements in the knee joints with the required quality of transients. In the case of an ideal engine, simulation has shown the correctness of these algorithms and high accuracy of realization of defined gait (including also the angular position of the body exoskeleton) as well as has revealed a significant impact of damping coefficients and elastic straps. The study has demonstrated the possibility for selection factors to ensure a comfortable movement for the human - operator due to abrupt reduction of vibrations in the system. At the same time, decreasing human’s energy expenditures calculated by criteria of biomechanical functionality were observed. A model of the exoskeleton was also studied taking into account the dynamic properties of the hydraulic cylinders and the geometry of their position.</p><p>The numerical studies allow us to make a sound choice of material for fastening straps of exoskeleton for the human body, to obtain desired parameters for selection of engines for the active option as well as to synthesize a control law that satisfies requirements for quality parameters.</p>