Research On LIPM-based Human Balance Assessment Method And Exoskeleton Balance Recovery Control

The application of exoskeleton in rehabilitation and assistance field has become increasingly prominent.Reliance on exoskeleton has become a pressing need for helping aging and disabled people to recover posture balance when they encounter unexpected disturbances,which involves many key technologies.The study and organic fusion of the human balance assessment method and the exoskeleton balance recovery control are the assurance of balance recovery.However,currently there is still a lack of a human balance assessment method that is suitable for both standing and walking to detect human posture imbalances,and little research has been conducted on exoskeleton balance recovery control.Therefore,research on human balance assessment method based on linear inverted pendulum model(LIPM)and balance recovery control based on exoskeleton was developed in this article.First,the parameters were normalized according to the human Five-Link model,and the human body kinematics equation was deduced.A multi-sensor system was built using the inertial measurement unit(IMU)and the foot pressure insole.The kinematics values were integrated with the sensor information to realize the real-time estimation of the position and velocity of the body's center of mass(Co M)and the swinging foot.Then the multi-sensor system was used to carry out human body movement experiments,which verified the validity and accuracy of real-time human motion estimation,and laid the foundation for human balance assessment and balance recovery control.Secondly,the results of different LIPM predictions of the position and velocity of the human Co M were studied.It was found that LIPM with a finite size foot can accurately predict the position and velocity of Co M.Then based on the theory of the capture point,the concept of single-step balance of posture was proposed.Then the relationship between the position of swing foot and capture point is analyzed through the human movement experiments,in which the phenomenon of swing foot chasing capture point is summarized.Based on this phenomenon,a human balance assessment method that is suitable for both standing and walking is presentd,and the correctness of this balance assessment method is verified through experiments.Then,according to the Five-Link model,the human body dynamics equation was established and verified based on the results of the hip joint torque calculation.In order to obtain the hip assist torque based on dynamic compensation,the mapping relationship between the degree of balance of the huamn and the coefficient of hip assist is established by fuzzy logic controller.Combined with the human balance assessment method,a complete hip exoskeleton balance recovery control framework was formed and simulated in Matlab/Simulink,which initially verified the feasibility of the balance recovery control method.Finally,the hip exoskeleton prototype experimental platform was used to verify the effectiveness of the hip exoskeleton balance recovery control method.The transparency of the hip exoskeleton to wearer's normal movements was verified firstly.On this basis,by applying forward and backward disturbances to the wearer,contrast experiments were carried out to compare the posture imbalance between wearing and not wearing the exoskeleton in standing and walking state,and the experiments verified the effectiveness of the hip exoskeleton balance recovery method in helping the wearer restore the posture balance.