| Exoskeleton has been among the global researching focus in the field of science and technology in recent years. The idea of exoskeleton was originally conceived from bionic skills of human beings. Things like helmets and armour are the simplest mode of exoskeleton for protection and defenses. As the technology improves, the dynamic system for exoskeleton can share external load that the body bears in different activities apart from protecting the human, technology of which has been achieved. Therefore modern notion of exoskeleton means stimulating human skeleton, muscles and joint systems and thus equipping them corresponding metal exoskeleton to pass the load to the ground through it. It also means a man-machine coupling system composed by body and exoskeleton work cooperatively with help of mechanical, dynamic and control systems to enhance loading ability and body endurance, which is defined as man-machine accompanying load system. This system can effectively solve the contradiction between the increasing load of the military and civil field and the limited human carrying capacity. At present, exoskeleton technology has been the important research content among the United States, Japan and Russia and other countries. In which the global famous Lockheed Martin Corporation is included.Focusing on key technologies of man-machine system in mode of exoskeleton, the paper studies theoretically on exoskeleton, the man-machine accompanying load system from aspects of dynamics analyses on exoskeleton, multi-DOF vibration response, human body nonlinear motive characteristic function, and multi-rigid-body system dynamics with holonomic constraints. Research has been mainly developed from the following several aspects.(1) Based on biomechanics and ergonomics, the notion of man-machine coupling is introduced in the paper in the field of exoskeleton research. Man-machine coupling is explored preliminarily from ergonomic parameters, and freedom degree of joints setting and constraints, dynamic system design. A mathematical model of exoskeleton in parameterized design is built using minimal dimension parameters under function. Meanwhile, on basis of functional requirements for vertical loading, the dynamic model of exoskeleton system is set up by taking hydraulic system patter as the dynamic system of exoskeleton.(2) The work patter of’man dominates, machine assists’of man-machine system has been set, and the idea of PRBA motion model is proposed for inherent characteristics of mechanical motion; In view of analysis theory of multi-rigid-body plane motion, motion equations of the following motion and relative motion of postures of’squat’、"single leg kneeling" and "walking" is built inside human vertical plane. A mathematical model of each component space motion is defined by point synthetic method.(3) For shocking and vibration phenomena occurred after movement speed increase of the man-machine accompanying load system, the paper proposes a new idea to put multi-DOF vibration analysis theories into exoskeleton studies. Two system models of secondary suspension elastic damping are designed in hips and ankles, and multi-DOF motion differential equations of each system are set up. Output response characteristics of additional harmonic excitation are acquired by MATLAB stimulation. Based on the rigid-flexible coupling theories, strength and stiffness of the bearing system are analyzed by ANS YS, finite element analysis software, as well as modal analysis of the whole exoskeleton structure.(4) Adopting MOCAP, a motion capture system, a motion model of typical postures when human body moves is rebuilt with angle variation of each joint as input parameters; Taking INVSPOLY function as primary function, and combined with finite element analysis theory together with regionalism and regional node looping calculation methods, the updated moving least-square method is applied into transferring nonlinear function of angle variation into linear function. Minimizing error sum of squares from each region to be data fitting error criterion, space motion function is built with angle variation as variables in typical motion postures.(5) Fitting into attachment model of exoskeleton to the body, this paper proposes establishing multi-rigid-body system model with holonomic constraints for the whole structure of exoskeleton with basis of man-machine coupling. According to D’Alembert-Lagrange dynamics analysis theory, Lagrange dynamics equations of exoskeleton system are established with joint angles as generalized coordinates and bearing power of hydraulic cylinder as generalized outputs. Selecting’squat’as simulation object, taking nonlinear curve fitting of this posture as generalized coordinates, characteristic curves of bending moment domain of each joint are gained though MATLAB programming for stimulation study, which is to provide a reliable and useful theoretical foundation for energy design of dynamical system, sensing and control systems.Through studies on key technologies of exoskeleton, man-machine coupling model is built with basis of man-machine coupling with vertical load as object and man-machine accompanying load as constraint condition. In addition, a mathematical model for PQBA motion of exoskeleton is built, though which the difficulties in exoskeleton modeling and man machine separation have solved. By multi-DOF vibration analysis theory and rigid-flexible coupling theory, the conflicts between exoskeleton structure lighting, dynamic system accurate design and high-frequency man-machine accompanying load and heavy load bearing have been solved by differential equations of multi-DOF motion derived and FEA (finite element analysis) motion model built. Kinetic analytical model of multi-rigid-body system with holomonic constraints for the whole exoskeleton structure is built; Through MOCAP, the motion capture system and nonlinear transformation obtained by updated moving least square method, space motion function relationship with angle variation of typical motion posture as variables is finally established in acquiring exact solution for driving movement of each joint, by which the vague cognition in dynamic output by dynamic system, lack of basis modeling knowledge in real-time and follow-up control strategies in control system, and lack of real-time dynamic load in local optimization of exoskeleton structure existing in previous studies.The research result presented by the paper has been partly applied into’experimental prototype of individual exoskeleton load assisting system’, a programme which is mainly undertaken by Southwest Jiaotong University. The programme has achieved breakthrough in heavy load bearing in man-machine accompanying load system, man-machine coordination, output characteristic of efficient dynamic system and other key technologies which has laid a beneficial, reliable and solid theoretical foundation for other key technology studies. |
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