路面横倾角度对人体步进摩擦的影响

Influence of Road Heeling Angle on Human Stepping Friction

预防滑摔是步进摩擦研究的主要目的,但现有研究集中于水平路面和上下坡,对横倾路面研究较少.通过采用自制步进摩擦试验平台测试人体在横倾路面上行走时的摩擦力、足偏角和步态周期,计算必要摩擦系数.结果表明:随着横倾角度的增大,重力的侧向分量增大,导致侧向摩擦系数增大并起主要作用,侧滑风险升高,可调整重心向低侧偏移以减小必要摩擦系数,从而降低滑摔风险;低侧脚足偏角减小,高侧脚足偏角增加,可增加低侧脚足偏角的方法增加动态稳定域以提高行走时的稳定性;路面横倾增大了侧滑风险,人体自适应平衡机制随之减缓步速,并缩短较危险的单支撑期和延长较安全的双支撑期以防止滑摔.

Walking is the most common way of movement in human daily life,and slip and fall accidents frequently happen in the process of human walking.It not only seriously affects physical and mental health of the human body,but also causes huge economic losses to the society.At present,the prevention of slip and fall is the main research direction of human stepping friction.The existing researches mainly focus on the dynamics and kinematics of human body when walking on the horizontal and slope pavements,studies dealing with heeling pavement have been limited.In this paper,ten healthy male subjects(age 22.3±1.85 years,height 175.4±3.3 cm,weight 65.1±5.8 kg)were selected for this study.The outsole material was rubber with density 1.18 g/cm3,and the angle,interval and height of sole pattern were 95°,2.25 mm and 1.03 mm,respectively.A self-made stepping friction test platform,which was composed of a electromechanical motion platform with six degree of freedom,two force plates(Bertec FP4060-08-2000,size 0.6 m×0.4 m,sampling frequency 1 kHz,Bertec Corporation,U.S.),one plantar pressure plate(Podomed UP18,size 1.8 m×0.5 m,measurement error≤±1%,time lag≤0.1%,acquisition frequency 200 Hz,Sensor medica,Italy),and a motion capture system with six cameras(Miqus M3,displacement error≤0.1 mm,acquisition frequency 340 fps,system delay≤5 ms,Qualisys,Sweden),was used to test the mediolateral friction Fx,anterior-posterior friction Fy,normal pressure Fz,toe out angle and gait cycle of human body when walking on heeling pavement,and the required friction coefficient was calculated.The heeling angles ofαbetween the platform and horizontal plane were-20°,-15°,-10°,-5°,0°,5°,10°,15°and 20°,respectively.The results showed that the extreme values of mediolateral friction and required coefficient of friction increased with the increase of pavement heeling angle,while the extreme values of anterior-posterior friction force and required coefficient of friction did not change significantly.The anterior-posterior coefficient of friction was similar to the overall coefficient of friction,the anterior-posterior coefficient of friction played a major role in the overall coefficient of friction,and risk of sideslip increased.The human body could adjust the center of gravity to lower side to reduce the required coefficient of friction,so as to reduce the risk of sliding.With the increased of heeling angles,the toe out angle of lower foot decreased,and the toe out angle of higher foot increased.The human body could increase the dynamic stability region by increased the toe out angle of lower side foot to improve the stability of walking on heeling pavement.The adaptive balancing mechanism of human body slowed down the walking speed on heeling pavement,shorted the dangerous single support phase and prolonged safe double support phase to prevent slip and fall,because heeling angle increased the risk of sideslip.