Structural Design And Motion Research Of Forward Crawler Ladder Wheelchair

The process of urbanization and population aging in China is accelerating,the existing public facilities for the elderly and the disabled are seriously lacking,and the travel of the elderly and the disabled is very difficult.In order to alleviate this problem,researchers have developed a ladder wheelchair by combining the obstacle crossing mechanism with the ordinary wheelchair.However,the existing stair climbing wheelchair mainly adopts the backward climbing posture,which has the disadvantages of high psychological panic of users and the need to adjust the posture before climbing the stairs.In response to these problems,this paper designs and develops a crawler-type stair-climbing wheelchair with a forward-type stairclimbing posture.(1)The overall scheme and mechanical structure design of the forward climbing wheelchair are carried out.Based on the correlation matrix method and the weighted sum method,the overall design scheme of the forward climbing wheelchair is determined.The structure design of single joint crawler ladder mechanism and seat leveling mechanism is carried out,and the virtual prototype of forward ladder wheelchair is established in Solid Works.(2)The mechanical and kinematic analysis of the forward ladder wheelchair is carried out.Through the analysis of the movement process of the ladder wheelchair,three key stages in the movement process are summarized,and the mechanical mathematical model of the ladder wheelchair in the key process is established.Based on the kinematics method of spatial homogeneous coordinate transformation,the kinematics model of the forward climbing wheelchair is established,and the position and speed of the center of gravity during the movement of the forward climbing wheelchair are obtained.(3)Modeling and analyzing the stability of the moving process of the forward stair climbing wheelchair.Based on the quantitative analysis method of tipping stability,the tipping stability index is introduced to quantitatively analyze the stability of the moving process of the forward stair climbing wheelchair,and the mathematical model of the stability of the forward stair climbing wheelchair at different stages is established.(4)Simulation experiments are carried out based on the forward ladder wheelchair model.Based on MATLAB,the stability model of the forward stair climbing wheelchair is simulated,and the change curve of the stability index of the forward stair climbing wheelchair is obtained.The stability of the climbing process with different climbing postures and the stability of the forward climbing wheelchair up and down the stairs were compared and analyzed.Based on ADAMS,the kinematics simulation of the climbing process of the forward climbing wheelchair is carried out,and the center of gravity displacement curve and acceleration curve during the climbing process of the forward climbing wheelchair are obtained.(5)The finite element analysis of the key components of the forward climbing wheelchair is carried out,and the prototype of the climbing wheelchair is built for related experiments.The finite element analysis of the key components on the forward ladder wheelchair is carried out,and the equivalent stress and deformation cloud diagram of the transmission shaft and chassis are obtained by static analysis.The first six natural frequencies and modal vibration nephograms of the transmission shaft and chassis are obtained by modal analysis.On this basis,a physical prototype of the forward climbing wheelchair was made and manned experiments were carried out.Under the load of 55 kg and 65 kg,the average speed of the prototype is 1.075m/s and 0.938 m/s respectively.Under the condition of no-load and load 55 kg,the average adjustment speed of the prototype is 3.7627 °/s and 2.7674 °/s;under the load of 55 kg and 65 kg,the average climbing speed of the prototype is 0.1346 m/s and 0.126 m/s.