Research On Design And Control Of Active-passive Combined Full-body Exoskeleton System

The exoskeleton is a perfect combination of advantages of the intelligence of humans and the power of robots,and it can be widely used in a variety of fields.In the military field,it can assist soldiers to walk,effectively reduce physical energy consumption and enhance combat capability;in the medical rehabilitation field,it can assist patients to improve walking gait,improve walking efficiency or assist health;in the industrial field,it can assist their work and reduce work intensity.The working principle of exoskeleton is similar to the mechanism of human movement,in which the bones play a bearing role,bones are connected by joints,and the contraction of muscles drives the bones to rotate around the joints.The study of working principle of huaman motion system is the foundation of designing exoskeletons.The movement of the lower limbs of the human body is more complicated.Therefore,the Vicon motion capture system is used to obtain the motion information of the human body during walking,and the human body model in the Any Body software is driven.Analyzing muscle activity,joint moment,and joint power in the study of inverse kinematics,which are used to provide information for designing exoskeleton.Considering the difference of human body characteristics and the diversity of movement,the exoskeleton is combined with active and passive exoskeleton,which is composed of upper limb assisted subsystem,lower limb assisted subsystem,and weight transfer subsystem.Each subsystem can work independently or be form a composite system through simple connectors to adapt to different scenarios.The upper limb assist subsystem is actively driven by motors,and the driving force is transmitted through the soft Bowden cable to assist the upper arm to lift heavy objects and reduce the fatigue of the upper arm muscles.The lower limb assist subsystem is also actively driven by motors,which is transmitted through the Bowden cable to assist the hip joint extension.The load transfer subsystem is designed to imitate the structure of the lower limbs of the human body.It can follow the lower limbs during the swing phase,and transfers the load to the ground through the rigid support rod to reduce the load on the shoulders of the human body in the supporting phase.The upper limb assisted subsystem and the lower limb assisted subsystem are powered by motors,so an excellent control strategy is an important condition for ensuring "humanmachine coordination".The upper limb assisting subsystem performs upper limb gesture recognition based on Inertial Measurement Unit data,and hierarchical control is adopted in the subsystem.The high-level control is used for intention recognition,and the lowlevel control is used to control motors.The lower limb assisting subsystem is used to assist the extension of the hip joint,generate a target torque curve according to the lower limb movement model,and use the admittance control strategy to control the system according to the predicted gait cycle.In order to evaluate the efficiency of the exoskeleton,the efficiency of each subsystem working individually is evaluated.The electromyographic signal of the upper arm muscles and the upper-arm stability are measured with the assistance of the upper-limb powerassisted subsystem;the electromyography signal measurement and net metabolic cost are measured with the assistance of the subsystem;the net metabolic cost and the plantar pressure are tested with the assistance of the weight transfer subsystem;when the lower limb assist subsystem and the weight transfer subsystem work together,flexibility tests are conducted when walking under different terrain.The result of experiment shows that the exoskeleton system can effectively reduce muscle fatigue without affecting the wearer’s movement and reduce the metabolic cost.