Research On Lower Limbs Powered Exoskeleton Robot

According to the aggravating trend of aging population,medical rehabilitation and frequent global geological disasters,a large number of in-depth and urgent researcheshave been done about the powered exoskeleton robot.Lower extremity exoskeleton robot is a wearable man-machine integration device for human muscle power augmentation,the elder and disabledservice,and heavy manual work assisting.It can also be applied to a variety of fields as a subsystem,such as the earthquake rescue system,individual soldier combat system and the polar expedition system.C hina is one of the most serious earthquake victimsover the world.The transportation of rescue equipments and materials might be seriously hindered by the great deal of damaged bridges,roads and buildings.It has important value and practical significance to develop a wearable lower limb exoskeleton robot to help the rescue workers' long distance walking with heavy loadsin complex road environment.Although numerous lower limb s powered exoskeleton robot prototypes have been designed,almost none of them have suffic ient load-carrying capacity and the adaptability to complex terrainin the fie ld.And all of the exoskeleton design method,human-machineinteractivemethod and the human-machine coordinated motion control method need to be deep studied and probed.In this paper,a lower limbs powered exoskeleton robot HIT-LEX,is proposed for load carrying augmentation in the complex terrain.For thesuitableexoskeleton configurationdesign coordinating with the lower limb movement of human body,the anthropomorphic concept is chosen.By the analysis of the physiological structure,human walking mechanism and the CGA data,both the degrees of freedom distribution and active jointsselection are preliminarily determined.Then the detection of human walking gait and joint movement limits are conducted by a specially designed portablelower limb s exoskeleton.According tothese studies,the reasonable joints rotational ranges are determined.Variety anthropomorphic configurationsareproposed and the relatively optimal design schemes are selected for the exoskeletonstructure design.Based on the bionic structure design,two concrete structures are designed respectively for the "quasi anthropomorphic" and "completely anthropomorphic" schemes.And the former is chosen for its lighter weight and compact size.The total weight is 43 kg with a power module of 4.5kg.It can also be foldedinto a size of 86.5×50×36.5cm.The main components include the trunk part,two legs and two sensing shoes.The Human-machineinteractive force detection is proposed at the back and feet.Amodular active joint drive unit is designed for the hip and knee joints with largeoutput torque.The electrical system consists of the hierarchical control hardware system,the communication system and the energy system.HIT-LEX has a time-varying topology and a large number of passive redundant joints,which bring great challenges to the kinematics and dynamics analysis.In this paper simplifiedkinematic models in the sagittal and frontal planes are established based on the summary of the human lower limb movement characteristics.Then five basic kinds of kinematics morphology and the corresponding Lagrange dynamics equations are established and studied for the robot control,including the single leg support phasein the sagittal plane,the doublelegs support phasein the sagittal plane,the single leg support phasein the frontal plane,the doublelegs support phasein the frontal plane,and the doublelegs swing phase.For the diversity and randomness of human lower limb s motion in complex terrain,aspecial human movement intention recognition method is proposed which can accurately identify the exoskeleton robot' kinematic topology configuration and the human movement intentionunder current configuration.Then the force control method is adopted based on the interaction force feedback at the back and feet.the zero force tracking control of the end of the kinematics is carried out to realize the stable andcontinuous power-assisted walking.A diversified evaluation system for HIT-LEX is established by the wearer 's subjective feeling and some objective indicators.Firstly,the adaptability and flexibility of exoskeleton to the human body's multiple movement styles and different ground conditions are tested.The walking gait influences by the exoskeleton are also analysed.Secondly,the tests of objective evaluating indicators inc lude the maximum payload test,the human actual bearing test,the energy consumption and endurance ability test.The results showthat the force applied to human back is far smaller than the load weight,which indicates that the exoskeleton has good power assisting effect.In addition,the exoskeleton meets the designing requirements of the maximum payload of 50 kg,the maximum speed of 5km/h,the endurance ability of 5km and 2h.