Optimal Design Of Hydraulic Systemof The Lower Limb Power Assisted

Heavy-duty exoskeleton assistance system is a new concept of individual combat equipment.The Exoskeleton is a kind of complex control system,which is controlled by the human body and driven by the mechanical structure.In the heavy carrying state,in more complex terrain environments,it can support individual soldiers to march at normal speed and complete basic tactical actions.The purpose of the exoskeleton research is to enable t he wearer to use the machine to improve the human body's load capacity,exercise ability,and assist the exoskeleton's power system to provide the main assistance.The hydraulic power system is the source of strength for the exoskeleton to perform man-machine coordinated motion and achieve dynamic power.The level of performance directly determines the key technical indicators of the exoskeleton robot's weight-bearing capacity,endurance,and overall weight.With the emphasis placed on external bone research year by year,the technology of weight-bearing exoskeletons has developed rapidly.Some exoskeleton prototypes,including prototypes developed by this team,the hydraulic power system has basically satisfied the demand of weight-bearing exoskeletons in terms of output drive capability.However,due to limitations of some components and problems of the hydraulic system itself,the volumetric weight of the hydraulic power system seriously exceeds the standard,the exoskeleton hydraulic system has serious heat generation,the system consumes high energy,the pressure build-up process has a high delay,and the pressure build-up time is long.Bad issues are still outstanding.At present,there is still a big gap between advanced technological level and foreign countries.It is necessary to optimize the design and performance of the hydraulic power system of weight-bearing exoskeletons on the basis of existing research work in order to resolve the deficiencies.The specific work of the paper is as follows:(1)Based on biology and human skeletal analysis,the functions of the exoskeleton system and the human extracorporeal skeletal system are analyzed.Discussing the human body movements,and selecting upright walking conditions.The characteristics of erect walking are analyzed.Fit the regular curve to get the upright motion characteristic curve.(2)According to the gait movement characteristics and the exoskeleton's mechanical system,study the gait characteristics of the exoskeleton,establish a geometric model of the exoskeleton knee joint,optimize the design of the important parameters of the hydraulic cylinder,The swing phase and the wobble phase are analyzed in the upright walking of the exoskeleton by the human-machine coupled state,and according to the change trend and characteristics of the joint motion angles of the support phase and the wobble phase,the working state of the hydraulic cylinder is analyzed,and the volume speed-modulating system is optimized.(3)The exoskeleton volume speed-modulating system simulation system was built on the AMESim software platform.The volume governing system and the gravity load simulation test rig were designed based on the preliminary simulation results.The experiment of the volumetric speed regulation system under different load conditions was carried out.The purpose is to simulate the hydraulic power system under the load of the exoskeleton from the principle and effect.According to the insufficiency of the experimental results,the hydraulic system is optimized based on AMESim.When the volumetric speed control hydraulic system is applied to the exoskeleton,the improved design is optimized according to the simulation results,and the system pressure,the hydraulic cylinder movement speed,and the system pressure establishment response time meet the requirements of the exoskeleton research.Through the research of this paper,the simulation,experiment and optimization of the exoskeleton volume speed-modulating system hydraulic power unit have been carried out.Which provides an effective reference for the application of the system under exoskeleton conditions,and has certain practical value.