A modeling method for predicting human plantar pressure response

Abstract

A modeling method for predicting the pressure response of the human foot plantar, which first measures the biomechanical parameters of the human body; then, based on the assumption that the motion of the human body's center of mass is a periodic motion, according to the measured biomechanical parameters and empirical formulas of human kinematics, a kinematic equation is developed to describe the periodic motion of the center of mass in the vertical direction when the human body is walking forward; then, based on the d'Alembert principle, a dynamic equation is established to describe the kinematics of the center of mass; then, based on the empirical gait phase ratio, the vertical pressure response of the foot plantar in the single support phase and the double support phase of gait are solved respectively; then, the horizontal pressure response of the foot plantar that satisfies the horizontal speed and gait cycle is solved through iteration; finally, a drawing is drawn to describe the biomechanical characteristics of the human lower limbs. The present invention does not require complex optimization equations and boundary conditions, has clear physical meaning, and accurately corresponds to actual human biomechanical parameters, and has the advantages of practicality and accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of human body mechanics, and in particular to a modeling method for predicting pressure response of the human plantar surface. Background Art

[0002] With the continuous improvement of human living standards, human body mechanics has become an essential technology for improving human production and life. As a type of human body mechanics, plantar pressure response can be used as an evaluation indicator for wearable energy-harvesting devices and lower-limb motion-assisting exoskeletons, and can also provide a reference for diagnosing lower-limb diseases. Therefore, it is necessary to study the modeling method of human plantar pressure response to provide a technical basis for the design and optimization of wearable energy-harvesting devices and lower-limb motion-assisting exoskeletons, and to provide pathological support for the diagnosis of lower-limb diseases.

[0003] At present, domestic and foreign scholars have conducted in-depth research on the plantar pressure response technology of the human foot and proposed a variety of different modeling methods for predicting the plantar pressure response of the human foot, mainly including the optimization-based multi-rigid body modeling method for the lower limb and the inverted pendulum modeling method based on energy conservation. The optimization-based multi-rigid body modeling method for the lower limb (Yang JJ, Marler T, Rahmatalla S. Multi-objective optimization-based method for kinematic posture prediction: Development and validation [J]. Robotica, 2011, 29 (2): 245-253.) solves a series of lower limb motion equations through an optimization algorithm to obtain the motion characteristics of the human lower limb under different working conditions, including joint angles and swing speeds. However, the definition and boundary conditions of the lower limb motion equations are complex, making practical application difficult. The inverted pendulum modeling method based on energy conservation (Whittington BR, Thelen D G. ASimple Mass-Spring Model With Roller Feet Can Induce the Ground Reactions Observed in Human Walking[J]. Journal of Biomechanical Engineering, 2009, 131(1):8-0.) assumes the human lower limbs to be a pair of elastic inverted pendulums with linear stiffness. The human waist trajectory and plantar pressure are simulated by solving the stiffness and endpoint positions of the linear springs. However, in practical applications, it is necessary to solve complex nonlinear equations to obtain the initial values of the model, and the initial values of the model are difficult to correspond to the actual human biomechanical parameters. None of the above methods can meet the technical requirements for evaluating and guiding the design and optimization of wearable devices for the human body. Summary of the Invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a modeling method for predicting the plantar pressure response of the human body, which does not require complex optimization equations and boundary conditions, and realizes plantar pressure response modeling with clear physical meaning and accurate correspondence with actual human biomechanical parameters.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A modeling method for predicting plantar pressure response of a human body comprises the following steps:

[0007] The first step is to measure the biomechanical parameters of the human body;

[0008] The second step is to describe the periodic motion of the human center of mass: Assuming that the human center of mass moves in a periodic manner, the kinematic equation describing the periodic motion of the center of mass in the vertical direction when the human body is walking is developed based on the measured biomechanical parameters and empirical formulas of human kinematics.

[0009] The third step is to establish the dynamic equation of the human body's center of mass: Based on the d'Alembert principle and the vertical kinematic equation of the human body's center of mass when walking, the dynamic equation describing the kinematics of the center of mass is established.

[0010] Step 4: Solve the vertical pressure response of the plantar foot: Based on the empirical gait phase ratio, solve the vertical pressure response of the plantar foot in the single support phase and double support phase of gait respectively;

[0011] Step 5: Solve the horizontal pressure response of the plantar: Based on the biomechanical parameters measured in the first step and the vertical pressure response of the plantar solved in the fourth step, solve the horizontal pressure response of the plantar through iteration;

[0012] Step 6. Draw a biomechanical description of the human lower limbs: Based on the vertical pressure response and horizontal pressure response of the soles of the feet obtained in steps 4 and 5, draw a description of the biomechanical characteristics of the human lower limbs.

[0013] The empirical formula of human kinematics in the second step is expressed as:

[0014] Y=Y0cos(ωt)

[0015] Where: Y is the vertical displacement response of the human body's center of mass, in meters (m); Y0 is the vertical displacement response amplitude of the human body, in meters (m); ω is the walking frequency at the current speed;

[0016] The walking frequency ω at the current speed is:

[0017]

[0018] Where: va ——Current horizontal walking speed, in kilometers per hour (km / h); L0——Effective length of lower limbs, in meters (m);

[0019] The vertical displacement response amplitude Y0 of the human body is:

[0020]

[0021] The described modeling method for predicting plantar pressure response of the human body is not only applicable to gait analysis when walking with wearable devices, such as wearable energy capture backpacks or lower limb exoskeletons, but also to gait analysis when walking without wearable devices.

[0022] The beneficial effects of the present invention are:

[0023] 1) The present invention does not require solving complicated mathematical equations, but only requires basic mechanical knowledge, the D'Alembert principle, and empirical gait cognition to obtain the plantar pressure response during walking.

[0024] 2) The present invention avoids solving complex optimization algorithms, has clear physical meaning, and corresponds one-to-one with actual biomechanical parameters such as stride length, stride frequency, and stride speed, making it easy to apply in practice.

[0025] 3) The present invention has strong scalability and can accurately simulate different walking conditions, such as wearing an energy-capturing backpack, wearing a lower limb exoskeleton, and gait disorders, by changing the kinematic assumption of the reciprocating motion of the center of mass during the forward motion of the human body. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a flow chart of the present invention.

[0027] Figure 2 It is a comparison curve chart of the model prediction and database data of the embodiment of the present invention. DETAILED DESCRIPTION

[0028] The present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0029] Reference Figure 1 A modeling method for predicting plantar pressure response of a human body comprises the following steps:

[0030] The first step is to measure the biomechanical parameters of the human body: in this embodiment, the effective length of the lower limb L0 is 0.88m, the horizontal walking speed v a The modeling analysis is based on the horizontal walking of a healthy person without any weight and the walking speed is 5 km / h and the weight is 67 kg.

[0031] The second step is to describe the periodic motion of the human center of mass: Assuming that the human center of mass moves in a periodic manner, the kinematic equation describing the periodic motion of the center of mass in the vertical direction when the human body is walking is developed based on the measured biomechanical parameters and empirical formulas of human kinematics.

[0032] The empirical formula of human kinematics is expressed as:

[0033] Y=Y0cos(ωt)

[0034] Where: Y is the vertical displacement response of the human body's center of mass, in meters (m); Y0 is the vertical displacement response amplitude of the human body, in meters (m); ω is the walking frequency at the current speed;

[0035] The walking frequency ω is:

[0036]

[0037] The vertical displacement response amplitude Y0 of the human body is:

[0038]

[0039]

[0040] Y = 0.0209cos(12.2573t);

[0041] The third step is to establish the dynamic equation of the human body's center of mass: Based on the D'Alembert principle and the kinematic equation of the human body's center of mass in the vertical direction when walking, the dynamic equation describing the kinematics of the center of mass is established, which is expressed as:

[0042]

[0043] Where: M - body weight; g - acceleration due to gravity; ——vertical acceleration of the center of mass; f y1 ——Vertical component of force of leg 1; f y2 ——Vertical force component of leg 2; f x1 ——horizontal component of force of leg 1; f x2 ——horizontal force component of leg 2; ——horizontal acceleration of the center of mass; θ1——angle between leg 1 and the vertical direction; θ2——angle between leg 2 and the vertical direction;

[0044] The fourth step is to solve the vertical pressure response of the plantar foot: According to the empirical gait phase ratio, the vertical pressure response of the plantar foot in the single support phase and the double support phase of the gait is solved respectively. y1 and f y2 ;

[0045] Step 5: Calculate the horizontal plantar pressure response: Based on the biomechanical parameters measured in Step 1 and the vertical plantar pressure response calculated in Step 4, calculate the horizontal plantar pressure response through iteration. The horizontal plantar pressure response must satisfy both the horizontal average speed of 5 km / h obtained in Step 1 and the cadence of 12.2573 obtained in Step 2. The iterative results are scattered points and will be displayed in Step 6.

[0046] Step 6. Draw a biomechanical description of the human lower limbs: Based on the vertical pressure response and horizontal pressure response of the soles of the feet obtained in steps 4 and 5, draw a description of the biomechanical characteristics of the human lower limbs.

[0047] Reference Figure 2 , Figure 2 This figure compares the predicted results of this embodiment with the actual collected data. The modeling method predicts the vertical pressure response, while the experimentally measured results are represented by thick black lines and thin gray lines, respectively. The solid and dashed lines represent the vertical and horizontal pressure responses, respectively. The modeling method accurately predicts the vertical pressure response. While the horizontal pressure response has some error, the predicted trends are completely consistent.

[0048] In summary, the present invention only needs to rely on basic mechanical knowledge, the D'Alembert principle, and empirical gait cognition to obtain the plantar pressure response during walking. This is convenient for practical application and has strong scalability. By changing the kinematic assumption of the reciprocating motion of the center of mass during the forward motion of the human body, different walking conditions can be accurately simulated.

Claims

1. A modeling method for predicting plantar pressure response of a human body, characterized in that: The following steps are involved: The first step is to measure the biomechanical parameters of the human body; The second step is to describe the periodic motion of the human center of mass: Assuming that the human center of mass moves in a periodic manner, the kinematic equation describing the periodic motion of the center of mass in the vertical direction when the human body is walking is developed based on the measured biomechanical parameters and empirical formulas of human kinematics. The vertical displacement response amplitude Y0 of the human body is: Where: Y0 is the vertical displacement response amplitude of the human body, in meters; ω is the walking frequency at the current speed; v a ——Current horizontal walking speed, in kilometers per hour; L0——Effective length of lower limbs, in meters; The third step is to establish the dynamic equation of the human body's center of mass: Based on the d'Alembert principle and the vertical kinematic equation of the human body's center of mass when walking, the dynamic equation describing the kinematics of the center of mass is established. Step 4: Solve the vertical pressure response of the plantar foot: Based on the empirical gait phase ratio, solve the vertical pressure response of the plantar foot in the single support phase and double support phase of gait respectively; Step 5: Solve the horizontal pressure response of the plantar: Based on the biomechanical parameters measured in the first step and the vertical pressure response of the plantar solved in the fourth step, solve the horizontal pressure response of the plantar through iteration; Step 6. Draw a biomechanical description of the human lower limbs: Based on the vertical pressure response and horizontal pressure response of the soles of the feet obtained in steps 4 and 5, draw a description of the biomechanical characteristics of the human lower limbs.

2. The method according to claim 1, characterized in that The empirical formula of human kinematics in the second step is expressed as: Y=Y0cos(ωt) Where: Y - vertical displacement response of the human body center of mass, unit: meter; The walking frequency ω at the current speed is:

3. The method according to claim 1, wherein: It is not only applicable to gait analysis when walking with wearable devices, such as wearable energy capture backpacks or lower limb exoskeletons, but also to gait analysis when walking without wearable devices.

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