Design And Research Of Self-Adaptive Cam-Linkage Mechanism For Exoskeleton Center Of Gravity

The emergence of heavy-duty exoskeleton robot solves the problem of difficult transportation and transportation of materials under special circumstances,but the shift of the center of gravity of the human-machine system after loading is one of the main reasons for the torso of the human body.The early heavy-duty exoskeleton is designed to have humanoid ankle-knee-hip three joints with hydraulic drive unit,which can provide power for the work,while the hydraulic unit at the hip joint can adjust the angle of the back of exoskeleton.Taking into account the weight,life,energy efficiency and other aspects,most of the current use of knee drive,resulting in the weight-bearing exoskeleton torso backward tilt and the human body weight-bearing forward inclination does not match,resulting in an increase in the force of the human torso.It causes great disturbance and discomfort to the stability and comfort of human body walking under load.When a heavy load is too large,it can lead to imbalance or fall back and cause damage.Based on the two aspects of the actual space posture of the torso and the stability of the human body when the body is loaded,a cam linkage mechanism is proposed as the hip-back mechanism and used to coordinate the angular relationship between the torso and the load.On the basis of establishing the exoskeleton model with the standard height and the length of each body segment with Solid Works,the structural strength and the coordination between the structure strength and the position between the model and the human body model are analyzed.Through the analysis of gait movement of lower limbs in one cycle,the movement process of lower limbs and the spatial position of legs and thighs on one side of the body are obtained.The dynamic analysis of human lower limbs is carried out by Kane method,and the dynamic simulation is carried out in Adams.According to the national standard,the displacement of the center of gravity in the sagittal plane of the man-machine system is obtained by simulation.The results show that the new designed hip-back structure instead of the hydraulic drive unit at the hip joint,meet the requirement of personification in structure and does not hinder the normal movement of the lower limbs of the human body.Due to the use of a single drive(knee joint),the endurance ability is longer than the multi-drive.Hip-back mechanism is a connector and regulator for human torso and external load,on the one hand,it can ensure that the external load and the human body maintain a certain fixed connection,so that there is a certain feedback relationship between the human body and the exoskeleton.On the other hand,it can adjust the relationship between the load and the forward angle of human body,and it can meet the demand of increasing the forward inclination angle of the human body and has a certain relationship.1?The new mechanism correlates the load with the torso,and there exists a certain functional relationship between the load and the forward inclination angle of the torso.The larger the load,the greater the fore rake angle of the torso,which satisfies the trend of increasing the load and the forward inclination of the human torso.2?Between 0 and 12%BW(body weight),the human body bears less stress.After surpassing 12%BW,the increase of forward angle of torso increases sharply,which makes the center of gravity of torso move forward,counteracts the anti-reactance moment of body and exoskeleton,and improves the walking stability of human body and exoskeleton.3?The seven-bar model of human body is established by means of Kane method,which takes into account the indispensable foot in the walking process,which is more consistent with the actual walking condition of the human body.Compared with Newton law,Euler equation and Lagrange equation,Kane method does not require kinetic energy and potential energy,and is more suitable to be solved by computer.4?The system corresponds to different torso fore rake angles under different loads,and the force transmitted from the hip-back mechanism to the back can be satisfied within the 20%BW and adjusted by the exoskeleton trunk itself.This is a stable control range for walking stability.The center of gravity position is closer to the center of gravity position when standing upright,and the distance between the center of gravity is reduced by 9% compared before.