Evolution Law Of Slips And Falls Mechanism Of Human Body Under The Disturbed Force System While Walking

Slip and fall accidents are common among people in daily work and life,which not only cause physical and psychological injury to people in some degrees,but also lead to great economic losses.Especially when people walk on moving objects such as ships,trains,airplanes and automobiles,the non-uniform movement and turbulence of these objects will change the inclination of the walking surface,and people will be impacted by the external forces,which making human body easier to slip and fall,and the slipping mechanism become more complex.Therefore,it is of great theoretical and practical significance to study the influence of external environment on human slipping.In this paper,six degree of freedom step-by-step friction test platform is used to study the influence of external environment interference on the force of human body,the rick of human slipping and the slipping mechanism.The specific research contents and results are as follows.The effect of the friction direction on the force of human body,the tendency and the mechanism of slipping are studied by changing the angle between platform of the step friction test and the horizontal ground to change the direction of friction.The results show that the anteroposterior contact forces increase with the increasing of the angle between the friction and the ground,while the supporting force will decrease,so the peak value of the required friction coefficient will increase,and the risk of human slipping will increase.The effect of horizontal external force on human body and the mechanism of slipping and falling is discussed,which the horizontal external force acting on human body is caused by the horizontal non-uniform movement of the test platform.The results show that the support force of the sole is not affected by the horizontal external force,and the positive coupling of the horizontal external force and the horizontal inertia force of the gravity center makes the anteroposterior contact force increase,so as to improve the required coefficient of friction and increase the risk of human slipping and falling,and the greater the external force is,the higher the risk of slipping and falling is.The up and down reciprocating motion of the test platform can form the external force acting on the human body in the vertical direction.The results show that the anteroposterior contact force is not affected by the vertical external forces.When the vertical external force and the inertia force in the vertical direction of the gravity center are coupled positively and the direction is opposite to the gravity direction,the superposed result will reduce the support force of the foot,and the required coefficient of friction and the risk of slipping will be increased.The larger the external force,the greater the tendency of slipping.The statistical analysis results of the test data show that the actual friction and friction coefficient remain basically unchanged when walking on the horizontal static ground and the ground in different external environments;The external force interference can change the gait phase during walking,and change the time ratio of braking period and propulsive period.Among the three kinds of external disturbance conditions,the slope angle has the greatest influence on the tendency of slipping,the horizontal force is the second,and the vertical force is the least.The slipping and falling mechanism of human body under the disturbance of external environment is analyzed by using the simplified physical and mathematical model of trajectory gravity center.The results show that the human body must meet the dynamic balance of force and moment when walking in order to avoid slipping and falling,while the disturbance of external conditions destroys the original dynamic balance system of human body,so the human body must establish a new dynamic balance system of force and moment by adjusting the contact force,body posture and other measures.When the external disturbance condition is too large and the adjustment of the human body itself is not enough to establish a new dynamic balance system,the slipping will occur.A comprehensive fuzzy judgment mathematical model of slipping is established to judge the weight of multiple single factors such as step speed,step length,ground horizontal acceleration,ground slope and age on slipping based upon the theory of fuzzy mathematics and information entropy.Based on the response surface method,a slip prediction model is established to predict the slip risk coefficient of each factor under the joint action of multiple factors.The result of fuzzy judgment shows that the slope and the motion acceleration of the ground have a great effect on the human body's slip in many single factors.According to the analysis results of the prediction model,the horizontal acceleration has the most significant influence on slip and the walking speed has the least influence on slip when people walking under the horizontal external force,step length,and walking speed work simultaneously.The establishment of this mathematical model provides a new way to judge and predict the impact of various factors on the risk of sliding and falling.The establishment of the mathematical models provide a new idea and method for judging and predicting the impact of each factor on the risk of slipping and falling.In this paper,the theoretical system of slips and falls mechanism is improved in the process of human walking,which provides an important theoretical basis for the anti-skid of human body in the vehicle,especially when the Navy moves on the warship.