Study On Stability Of Wheel-legged Climbing-building Wheelchairs Based On Behavior Diagram

In the modern society,more and more elderly and disabled people choose the electric wheelchair as common transportation tool,but ordinary electric wheelchairs are powerless when they encounter obstacles such as ravines and stairs.In order to overcome the shortcomings of the existing climbing-stair wheelchair,this subject has designed an electric wheelchair which can control the front and rear legs and seat mechanism to climb the stairs.But the universal property,stability and comfort of climbing wheelchair are different with different obstacles.In order to improve the capability mentioned above,this paper is mainly about the research of motion characteristics and stability.At the same time,the optimization design of stability and comfort is designed to find the step parameters that are most suitable for this climbing wheelchair.Firstly,the definition of generalized behavioral maps that are three kinds of motion models is introduced and the process of climbing a wheelchair is described.Then the trajectory of each wheel is planned.Aimed at different step parameters,a variety of judgment model are put forward to determine working situation of rear wheel,and further to know the whole climbing process and motion models’ type and number.Secondly,based on the closed vector method,a plane kinematics model of generalized behavior graph that quadrangle and hexagonal model of climbing wheelchair in climbing process is established.And based on the method of Homogeneous transformation,a forward and inverse kinematics model of climbing wheelchair is established,and the further to get the kinematics laws of the end of the wheelchair mechanism and centroid of the climbing wheelchair.The kinematics of the drive parameters of each mechanism are obtained by the inverse kinematics model,which providing the basis for the control system.An kinematics simulation and detailed analysis of the key parts of climbing wheelchair is made,which providing the basis for the comfort analysis.Finally,the static and dynamic stability pyramid of climbing wheelchair is established by static stability boundary method and the force-angle stability measure.Based on the D’Alembert’s principle,a wheelchair-driven wheel with stairs contact reaction force model is established.Based on the stable cone and force model,the stability index is defined to comprehensively evaluate the stability of the wheelchair upstairs process,which can get themost dangerous states.Then three methods are put forward to improve comfort.Based on the above,a genetic algorithm is used to optimize the stability and comfort of the stair-climbing wheelchair to find the stair parameters that are most suitable for wheelchair work.By comparing the stability and comfort before and after optimization,it is proved that the performance of the stair climbing wheelchair after optimization has been significantly improved.