Design And Study On The Stair-climbing Mechanism Of Linkage

Population aging has become increasingly serious nowadays.There are 212.42 million elderly people aged over 60 years old in the whole country,accounting for 15.5 percent of the total population,and including 137.55 million elderly people aged 65,accounting for 10.1 percent.In addition,the second national handicapped person sampling survey shows that the total number of the disabled is 85.02 million.Furthermore,with the rapid development of urban construction,many people prefer living in the building.However,for the elderly,especially who can not move independently and freely,and the disabled,the stairs turn out to be their distress.Because ordinary wheelchair can not meet their needs of daily life,and in order to satisfy their demand,raise their living standard,and reduce nursing staff and family member's workload,it is quite necessary to design a type of stair-climbing wheelchair.From the perspective of mechanisms,combining with dynamics and numerical analysis,and summarizing the relevant technical data and literature about similar products at home and abroad,theoretical model based on connecting-rod type stair-climbing wheelchair is put forward,and double crank five-bar mechanism is determined in this thesis.The important section of the whole design is,through the locus curve formed by the coupler point of the five-bar linkage,to complete stair-climbing movement and to ensure locus curve formed by five-bar mechanism can climb stairs smoothly.The condition for existence of double crank of five-bar mechanism is determined in this design,and by the method of controlling variable,the effect of transmission ratio,bar length,the initial position and phase difference on locus curve is discussed.Objective function is set up according to Matlab optimization toolbox,meanwhile,on the basis of existence condition of crank and presence of track field,the constraint condition is sought,the bar length and the initial position of five-bar mechanism is optimized.Applying ergonomic theory,basing on physiological and psychological demand of the elderly and the disabled,and according to the standard size of all parts of adult body in our country,conforming to the mechanical characteristics,the main parts of stair-climbing five-bar is designed and three-dimensional model is set up by Creo2.0 software.Meanwhile,the mathematical model of dynamics of stair-climbing five-bar mechanism is build up,relevant mechanical parameter curve is obtained by dynamic analysis on stair-climbing device in Adams software.In the end,Abaqus software is applied for finite element analysis of integral structure and key parts of stair-climbing device.In this thesis,the basic model of connecting-rod type stair-climbing wheelchair is set up by the analysis of five-bar mechanism.The dynamic and static mechanics of stair-climbing device is verified through the Adams and Abaqus software.The dynamic curve shows that the device has relative stability in the process of movement and motor is chosen properly.Moreover,it provides foundation for the statics analysis.Meanwhile,the nephogram of statics analysis shows that the strength of the whole device conforms to the requirements.