Method and system for determining latent damage during long-term driving based on energy limiter

Abstract

The present invention discloses a method and system for determining hidden injuries from long-term driving based on an energy limiter. The method comprises an acquisition unit, a nonlinear hyperelastic model unit for human muscle tissue, a tangent elastic tensor unit, a strain energy density model unit for hidden injuries from long-term driving based on the energy limiter, a damage determination unit, and an output unit. The method determines the nonlinear hyperelastic model of human muscle tissue and the tangent elastic tensor; then establishes a strain energy density model for hidden injuries from long-term driving based on the energy limiter. Based on the driving posture and the strain energy density model for hidden injuries from long-term driving based on the energy limiter, the method determines whether the driver's muscle tissue has been damaged during long-term or prolonged driving. The present invention solves the problem of determining injuries to long-term or prolonged drivers, thereby preventing occupational diseases caused by long-term driving.

Description

Technical Field

[0001] The present invention relates to a method and system for determining hidden damage caused by long-time driving based on an energy limiter, and belongs to the field of automobile ergonomics. Background Art

[0002] As human tissue modeling technology begins to mature, a variety of models have been applied to the modeling of human muscle tissue. However, the existing models can only express complete materials and are not applicable to problems such as injuries. People who engage in driving work or professional driving for a long time will inevitably suffer certain injuries to their bodies during driving, which may seriously cause occupational diseases such as chronic muscle pain, lumbar muscle strain, lumbar disc herniation, and arthritis. Therefore, it is particularly important to establish a muscle damage model for long-term or long-term drivers. The existing nonlinear hyperelastic mechanics model can be applied to human muscle tissue, but the damage problem cannot be reflected in the model. Therefore, in order to better study the damage problems of long-term or long-term drivers and avoid occupational diseases caused by long-term driving, it is particularly important to improve the original human muscle tissue modeling to obtain a new model to characterize the damage. Summary of the Invention

[0003] Purpose of the invention: In order to solve the problem of long-term or long-time driving injuries, the present invention provides a long-time driving hidden injury determination system based on an energy limiter.

[0004] Technical solution: To achieve the above purpose, the technical solution adopted by the present invention is:

[0005] A system for determining hidden injuries caused by long-term driving based on an energy limiter comprises an acquisition unit, a nonlinear hyperelastic model unit of human muscle tissue, a tangent elastic tensor unit, a strain energy density model unit for hidden injuries caused by long-term driving based on an energy limiter, a damage determination unit, and an output unit, wherein:

[0006] The collecting unit is used to collect driving posture;

[0007] The human muscle tissue nonlinear hyperelastic model unit is used to determine the human muscle tissue nonlinear hyperelastic model according to the hyperelastic characteristics of the human muscle tissue;

[0008] The tangent elastic tensor unit is used to determine the tangent elastic tensor according to the nonlinear hyperelastic model of human muscle tissue;

[0009] The strain energy density model unit for hidden damage caused by long-term driving with an energy limiter is used to introduce an energy limiter based on the obtained tangent elastic tensor and establish a strain energy density model for hidden damage caused by long-term driving with an energy limiter on the basis of a traditional strain energy density function;

[0010] The damage judgment unit is used to determine whether the muscle tissue of the driver who drives the car for a long time or for a long period of time is damaged according to the driving posture and the strain energy density model of latent damage caused by long-term driving based on the energy limiter;

[0011] The output unit is used to output damage information.

[0012] Preferably, the strain energy density model of the latent damage caused by long-term driving based on the energy limiter is:

[0013]

[0014] Where, represents the new strain energy density function, Φ represents the energy limiter, represents the tangent elastic tensor, Eij 、E kl represents the Green strain tensor, i, j, k, l represent free indices, 0≤ε≤λ p ,λ p represents the total elongation of the sarcomere;

[0015] Optimum: The nonlinear hyperelastic model of human muscle tissue is:

[0016]

[0017] Where W is the strain energy function, C1 is the material constant one of human muscle tissue, C2 is the material constant two of human muscle tissue, and I1 is the first principal invariant of the strain tensor.

[0018] Preferably, the tangent elastic tensor is:

[0019]

[0020] in, represents the tangent elastic tensor, C1 is the material constant of human muscle tissue, C2 is the material constant of human muscle tissue, E 11 、E 22 、E 33 represents the Green strain tensor.

[0021] Preferred: Method for determining the tangent elastic tensor based on the nonlinear hyperelastic model of human muscle tissue:

[0022] Step 31: In a fixed three-dimensional space coordinate system, assume that the coordinates of a particle in the initial configuration are M0 = (X, Y, Z), and the coordinates of the configuration at time t are M t =(x, y, z), M t The partial derivative with respect to M0 is called the deformation gradient F of the object.

[0023] The deformation gradient of the object:

[0024]

[0025] Where F is the deformation gradient of the object, M t are the coordinates of the particle at time t, and M0 is the coordinates of the particle in the initial configuration.

[0026] In step 32, the right Cauchy-Green strain tensor C is obtained according to the deformation gradient of the object, and the Green strain tensor E is further obtained.

[0027] The relationship between the Green strain tensor E and the Cauchy-Green strain tensor C is:

[0028]

[0029] Step 33: Obtain the tangent elastic tensor with respect to the Green's strain tensor and the second-kind stress tensor according to the constitutive relationship between the Green's strain tensor and the second-kind stress tensor.

[0030] The second-order tensor form of Green's strain is as follows:

[0031]

[0032] The second-order tensor of Green's strain has nine components and is a symmetric tensor, so it can be expressed in the following first-order tensor form:

[0033] E=[E 11 E 22 E 33 2E 23 2E 13 2E 12 ] T ;

[0034] The first-order tensor form of the second-order stress tensor T, which is conjugate to the Green strain tensor, is as follows:

[0035] T=[T 11 T 22 T 33 T 23 T 13 T 12 ] T ;

[0036] The incremental form of the constitutive relation between the Green strain tensor and the second kind stress tensor T is:

[0037]

[0038] Where, dT ij represents the differential of the second kind stress tensor, T ij represents the stress tensor of the second kind, represents the tangent elastic tensor, dE kl represents the differential of the Green strain tensor, E kl represents the Green strain tensor, and i, j, k, and l represent free indices (ranging from 1 to 3).

[0039] From the energy perspective, according to the definition of the hyperelastic model, the Green strain tensor and the second-type stress tensor T also satisfy the following constitutive relations:

[0040]

[0041] Where W is the strain energy function.

[0042] Then we get the expression of the tangent elastic tensor:

[0043]

[0044] Step 34: Based on the nonlinear hyperelastic model of human muscle tissue, the relationship between the strain tensor, the first principal invariant, and the Green strain matrix is ​​obtained as follows:

[0045] I1=3+2(E 11 +E 22 +E 33 );

[0046] Substituting I1 into the nonlinear hyperelastic model of human muscle tissue yields:

[0047]

[0048] Step 35, the transformed nonlinear hyperelastic model of human muscle tissue is brought into the constitutive relation of Green's strain and the second-type stress tensor T to obtain the second-type stress tensor matrix:

[0049]

[0050] Since the second kind of stress tensor matrix is ​​a symmetric matrix, it can be written as follows:

[0051]

[0052] Step 36: According to the expression of the tangent elastic tensor, the tangent elastic tensor matrix of the following form is obtained:

[0053]

[0054] in, represents the tangent elastic tensor, C1 is the material constant of human muscle tissue, C2 is the material constant of human muscle tissue, E 11 、E 22 、E 33represents the Green strain tensor.

[0055] Preferred: Method for establishing a strain energy density model of latent damage caused by long-term driving based on an energy limiter:

[0056] Step 41: According to the energy limiter theory, a new strain energy density function is obtained:

[0057]

[0058] Where, represents the new strain energy density function, Φ represents the energy limiter, and W′ is the traditional strain energy density function.

[0059] Step 42: Substitute the traditional strain energy density function formula into the new strain energy density function:

[0060]

[0061] Where, represents the new strain energy density function, Φ represents the energy limiter, represents the tangent elastic tensor, E ij 、E kl represents the Green strain tensor, 0≤ε≤λ p ,λ p represents the total elongation of the sarcomere.

[0062] Preferably: a method for determining whether muscle tissue of a driver who drives a car for a long time or for a long period of time is damaged according to a strain energy density model of latent damage caused by long-term driving based on an energy limiter:

[0063] Step 51: Define damage variables based on the new strain energy density function.

[0064]

[0065] Where d represents the damage variable, Φ represents the energy limiter, and W′ is the traditional strain energy density function.

[0066] In step 52, the damage variable is driven by the reference strain energy density function, and the reference strain energy density function is decomposed into:

[0067]

[0068] Where W + (ε) represents the reference strain energy density function, λ and μ represent Poisson's ratio, A positive reference quantity representing the square of the trace of strain, represents the trace of the square of the positive reference strain, E1, E2, E3 represent the strains, represents the square of the positive reference strain, represents the square of the positive reference strain, represents the square of the positive reference strain;

[0069] Step 53, redefine the damage variable as:

[0070]

[0071] Where, is the local history quantity of the historical strain energy density function, where: W + represents the positive part of the complete strain energy density function,

[0072] In step 54, based on the historical strain energy density function and the local historical quantity of the historical strain energy density function, the inequality relationship satisfied by the loading function is:

[0073]

[0074] Where, Indicates the loading function, express The derivative of .

[0075] Step 55, transform the equation of motion into weak form:

[0076]

[0077] Where Ω represents the boundary condition, ρ represents the mass density, is the acceleration field, δu represents the displacement test function, u represents the displacement field, v represents the velocity field, σ represents the Cauchy stress tensor, : represents the double dot product, Represents the gradient.

[0078] Step 56: Use standard four-node quadrilateral elements to perform spatial discretization. The discretization formula is as follows:

[0079]

[0080] in:

[0081]

[0082] Where a represents the acceleration field, N u represents the shape function matrix, represents the node acceleration, v represents the acceleration field, represents the node velocity, u represents the displacement field, represents the node displacement, δu represents the displacement field test function, represents the node displacement test function, represents the displacement gradient, B u represents the gradient of the shape function, represents the node displacement, represents the node displacement test function gradient, Represents the node displacement test function, N I is the shape function of the Q4 element, I=1:4, is the gradient of the shape function in the x1(x2) direction.

[0083] Step 57, the discretized formula is brought into the weak form of the governing equation. The discretized form of the weak form is described at the element level, and we can obtain:

[0084]

[0085] Among them, Ω e represents the boundary conditions, ρ represents the mass density, b represents the object force vector, represents external tension, σ represents stress, {σ}=]σ 11 σ 22 σ 12 ] T ;

[0086] Transform the above formula into:

[0087]

[0088] Where, M, F int 、F ext are the consistent mass matrix, the internal force vector, and the time-varying external force vector, respectively. Their specific forms are as follows:

[0089]

[0090] Step 58: Discretize the equation of motion in time:

[0091]

[0092] Where M n+1 represents the consistent mass matrix of n+1 steps, represents the approximate value of the n+1 step acceleration, represents the internal force vector of n+1 steps, Represents the external force matrix with n+1 steps.

[0093] In step 59, by using the Newmark-Beta method, at a specific time increment t n -t n+1 and when Δt=t n -t n-1 When , the velocity and acceleration are approximately:

[0094]

[0095] Where, It represents the approximate value of n+1 step acceleration, a0 represents the technical parameters, represents the node displacement at time n, a2 represents the technical parameter, a3 represents the technical parameter, It represents the approximate value of n+1 step speed, a1 represents the technical parameter, a4 represents the technical parameter, and a5 represents the technical parameter.

[0096] Step 510: Substitute the approximate value of acceleration into the time-discretized motion equation to obtain:

[0097]

[0098] Step 511: directly estimate the time t by combining the interleaved format algorithm n+1 The displacement field at :

[0099]

[0100] Where, Represents the stiffness matrix at time n+1.

[0101] Preferably: it also includes a human-machine model unit, which establishes a "driver-seat-steering wheel-accelerator pedal" coupling simulation model based on a standing human body skeletal muscle model by modifying seat parameters, adding a steering wheel pedal model, and adjusting the connection points between the human body and the environment.

[0102] Preferably, the damage variable d is defined as follows: when the muscle tissue is in an undamaged state, d = 0. When the compression applied to the driver's neck, shoulder, and waist muscles exceeds the energy of the energy limiter during driving, the muscles in the relevant areas are damaged. As the strain increases, the muscle damage worsens, and d gradually increases until d = 1.

[0103] Another object of the present invention is to provide a method for determining hidden damage caused by long-term driving based on an energy limiter, which comprises the following steps:

[0104] Step 1: Collect driving posture;

[0105] Step 2, determining a nonlinear hyperelastic model of human muscle tissue according to the hyperelastic characteristics of human muscle tissue;

[0106] Step 3, determining the tangent elastic tensor based on the nonlinear hyperelastic model of human muscle tissue;

[0107] Step 4: Based on the obtained tangent elastic tensor and the traditional strain energy density function, an energy limiter is introduced to establish a strain energy density model of latent damage caused by long-term driving based on the energy limiter;

[0108] Step 5: determining whether the driver's muscle tissue is damaged due to long-term or long-term driving according to the driving posture and the strain energy density model of latent damage caused by long-term driving based on the energy limiter.

[0109] Compared with the prior art, the present invention has the following beneficial effects:

[0110] The present invention improves the original human muscle tissue model and introduces energy limitation theory to obtain a new latent injury model based on energy limiter, which solves the problem of injury determination for long-term or long-time drivers and can avoid occupational diseases caused by long-term driving. BRIEF DESCRIPTION OF THE DRAWINGS

[0111] Figure 1 This is a diagram of the driver's driving posture.

[0112] Figure 2 Detailed process for constructing implicit damage model based on energy limiter. DETAILED DESCRIPTION

[0113] The present invention is further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, modifications of various equivalent forms of the present invention made by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0114] A method for determining latent damage during long-term driving based on an energy limiter is proposed. The original human muscle tissue modeling is improved to obtain a new model to characterize damage, and a new strain energy density function is obtained. From this, the material constitutive law described by the new strain energy density function with an energy limiter can be derived. This method can better study the muscle damage state of drivers during driving, and can better study the damage problems of long-term or long-duration drivers, and avoid occupational diseases caused by long-term driving, such as Figure 2 As shown, the following steps are included:

[0115] Step 1: Collect driving posture.

[0116] Analyze the causes of muscle damage during driving, and further analyze the mechanism of muscle damage during driving based on the driving environment and driving posture. Figure 1As shown in the figure, the driver's limited driving space causes the left and right legs to perform different functions, leading to muscle imbalance. While driving, the waist, back, hip, and leg muscles must exert continuous force. This prolonged contraction leads to muscle oxygen deprivation, reduced blood supply, and tissue damage, which in turn causes muscle pain and spasms, creating a vicious cycle.

[0117] When driving a car, the driver maintains a fixed posture for a long time, and the muscles in the neck, shoulders and waist are in a state of static muscle tension. Harmful substances such as lactic acid and potassium ions produced by muscle metabolism cause chronic damage to local tissues, resulting in a decrease in muscle elasticity and causing symptoms such as soreness, swelling and pain in the neck, shoulders and waist.

[0118] Step 2: Determine the nonlinear hyperelastic model of human muscle tissue according to the hyperelastic characteristics of human muscle tissue.

[0119] Muscle tissue is composed of specially differentiated myocytes. Many myocytes gather together and are surrounded by connective tissue to form muscle bundles, which are rich in capillaries and fibers. Its main function is contraction, and it is used to perform various movements of the body and the activities of various organs in the body. When muscle is deformed by external loads under resting state, it does not satisfy Hooke's law. In simple terms, its stress-strain relationship is nonlinear, and there is almost no linear part in its stress-strain relationship. Therefore, the problem of material nonlinearity needs to be considered. According to the biomaterial properties of human soft tissue, it can be judged that human soft tissue belongs to the scope of hyperelastic materials. General hyperelastic materials have an elastic potential energy function W related to deformation, and the derivative of this function to the strain component is the corresponding stress component, and can restore to its original shape when unloaded. The present invention comprehensively considers the strain energy density function of different hyperelastic materials and selects the nonlinear hyperelastic model as an exponential form model according to the characteristics of human muscle tissue.

[0120] Then the nonlinear hyperelastic model of human muscle tissue is:

[0121]

[0122] Where W is the strain energy function, C1 is the material constant one of human muscle tissue, C2 is the material constant two of human muscle tissue, and I1 is the first principal invariant of the strain tensor.

[0123] Step 3: Determine the tangent elastic tensor based on the nonlinear hyperelastic model of human muscle tissue.

[0124] It is necessary to solve the linear elastic tensor matrix in the exponential form model selected above. When solving the nonlinear problem of human tissue materials, it is first necessary to select a suitable nonlinear hyperelastic model W based on the biomechanical characteristics of muscle tissue; then transform the muscle tissue strain energy function to obtain the relationship between the first and second principal invariants of the independent variable strain tensor of model W(I) and the Cauchy-Green strain tensor C, and then transform the strain energy density function to obtain model W(E); the stress matrix can be further derived based on the constitutive relationship satisfied by Green strain and the second type of Piola-Kirchhoff stress; finally, the Green strain tensor in the stress matrix is ​​differentiated to obtain the tangent elastic tensor

[0125] Since the stress and strain distribution of human soft tissue is related to the loading process, the incremental constitutive relationship needs to be adopted in actual engineering analysis. From the material perspective, the constitutive relationship of anisotropic nonlinear elastic materials is:

[0126]

[0127] In the formula Right now is the tangent elastic tensor, σ is the stress vector, ε is the strain vector, and i, j, k, and l represent free indices (ranging from 1 to 3).

[0128] If the formula is a function of the strain vector, it can be said that the material is nonlinear. is a constant matrix, then the material is linear.

[0129] After selecting the nonlinear hyperelastic model, the relationship between the stress vector and the strain energy density function can be derived as follows:

[0130]

[0131] According to the constitutive relationship of anisotropic nonlinear elastic materials, it can be concluded that:

[0132]

[0133] The tangent elastic tensor can be constructed based on the strain energy density function according to This can determine whether the model material is linear.

[0134] Therefore, the method for determining the tangent elastic tensor based on the nonlinear hyperelastic model of human muscle tissue includes the following steps:

[0135] Step 31: In a fixed three-dimensional space coordinate system, assume that the coordinates of a particle in the initial configuration are M0 = (X, Y, Z), and the coordinates of the configuration at time t are M t =(x, y, z), M t The partial derivative with respect to M0 is called the deformation gradient F of the object.

[0136] The deformation gradient of the object:

[0137]

[0138] Where F is the deformation gradient of the object, M t are the coordinates of the particle at time t, and M0 is the coordinates of the particle in the initial configuration.

[0139] Step 32: Obtain the right Cauchy-Green strain tensor C according to the deformation gradient of the object, and then obtain the Green strain tensor E.

[0140] The deformation gradient tensor is an asymmetric second-order tensor, defined according to the right Cauchy-Green strain tensor C:

[0141] C=F T F;

[0142] Define constants:

[0143] I = trance(C) = ∑C ii ;

[0144] Ⅱ=trance(C 2 )=∑C ij C ji ;

[0145] Ⅲ=trance(C 3 )=ΣC ij C jk C ki ;

[0146] Then order:

[0147] Ⅰ1=Ⅰ;

[0148]

[0149] For incompressible materials, we have:

[0150] det(F)=1;

[0151] The relationship between the Green strain tensor E and the Cauchy-Green strain tensor C is:

[0152]

[0153] Step 33: Obtain the tangent elastic tensor with respect to the Green's strain tensor and the second-kind stress tensor according to the constitutive relationship between the Green's strain tensor and the second-kind stress tensor.

[0154] The second-order tensor form of Green's strain is as follows:

[0155]

[0156] The second-order tensor of Green's strain has nine components and is a symmetric tensor, so it can be expressed in the following first-order tensor form:

[0157]

[0158] The first-order tensor form of the second-order stress tensor T, which is conjugate to the Green strain tensor, is as follows:

[0159] T=[T 11 T 22 T 33 T 23 T 13 T 12 ] T ;

[0160] The incremental form of the constitutive relation between the Green strain tensor and the second kind stress tensor T is:

[0161]

[0162] Where, dT ij represents the differential of the second kind stress tensor, T ij represents the stress tensor of the second kind, represents the tangent elastic tensor, dE kl represents the differential of the Green strain tensor, E kl represents the Green strain tensor, and i, j, k, and l represent free indices (range 1-3).

[0163] From the energy perspective, according to the definition of the hyperelastic model, the Green strain tensor and the second-type stress tensor T also satisfy the following constitutive relations:

[0164]

[0165] Where W is the strain energy function.

[0166] Then we get the expression of the tangent elastic tensor:

[0167]

[0168] Step 34, based on the nonlinear hyperelastic model of human muscle tissue, the muscle tissue strain energy density function is transformed to obtain the relationship between the strain tensor, the first principal invariant and the Green strain matrix:

[0169] I1=3+2(E 11 +E 22 +E 33 );

[0170] Substituting I1 into the nonlinear hyperelastic model of human muscle tissue yields:

[0171]

[0172] Step 35, the transformed nonlinear hyperelastic model of human muscle tissue is brought into the constitutive relation of Green's strain and the second-type stress tensor T to obtain the second-type stress tensor matrix:

[0173]

[0174] Since the second kind of stress tensor matrix is ​​a symmetric matrix, it can be written as follows:

[0175]

[0176] Step 36: According to the expression of the tangent elastic tensor, the tangent elastic tensor matrix of the following form is obtained:

[0177]

[0178] Step 4: Based on the obtained tangent elastic tensor and the traditional strain energy density function, an energy limiter is introduced to establish a strain energy density model of latent damage caused by long-term driving based on the energy limiter.

[0179] Methods for establishing strain energy density models for latent damage during long-term driving based on energy limiters, such as Figure 2 As shown, the following steps are included:

[0180] Step 41: When the car occupants are in continuous operation, their muscles are stretched, myofibrils are damaged, and muscle strength and endurance drop sharply. This process triggers an inflammatory response in the muscles, dissolves damaged muscle fibers, and produces soreness and stiffness. When myofibrils are on the verge of being damaged, the total elongation of the sarcomere is defined as λ p .

[0181] Since muscle stretching is not unlimited,

[0182] when

[0183] Where Φ is the energy limiter, which represents the specific energy released during the compression process of muscle tissue until it is completely damaged, and is equal to the area under the stress-strain curve.

[0184] According to the energy limiter theory, a new strain energy density function is obtained:

[0185]

[0186] Where, represents the new strain energy density function, Φ represents the energy limiter, and W′ is the traditional strain energy density function.

[0187] Step 42: Substitute the traditional strain energy density function formula into the new strain energy density function:

[0188]

[0189] Where, represents the new strain energy density function, Φ represents the energy limiter, represents the tangent elastic tensor, E ij 、E kl represents the Green strain tensor, 0≤ε≤λ p ,λ p represents the total elongation of the sarcomere.

[0190] The traditional strain energy density function is not suitable for the problem of damage. Therefore, the present invention introduces the energy limitation theory on the basis of the traditional strain energy density function to obtain an energy limiter, and integrates the energy limiter into the strain energy density function to obtain the strain energy density function for the hidden damage problem under strain conditions based on the energy limitation theory.

[0191] Step 5: determining whether the driver's muscle tissue is damaged due to long-term or long-term driving according to the driving posture and the strain energy density model of latent damage caused by long-term driving based on the energy limiter.

[0192] When a driver drives a car for a long time or during a long driving process, it is easy to cause damage to the cervical spine, waist and leg muscles, which may seriously cause occupational diseases. The present invention establishes a latent damage model based on an energy limiter to study the problem of muscle damage during driving. When the muscle load reaches the upper limit of the energy limiter, the muscle is in a damaged state. In the system, the standing model in the system model is secondary developed, and a three-dimensional seat model is imported. The developed human body model of the driving posture is connected with the pre-set body segments of the seat to obtain a "driver-car seat-steering wheel-accelerator pedal" simulation model. The deformation of the human muscle tissue in the nonlinear hyperelastic model is often related to its deformation history. Under this condition, we use the interleaved format algorithm to solve the control equation. In this case, the process of solving the motion equation is divided into two parts. The first step is to update the displacement u, velocity v and acceleration a, and then calculate the historical field variables and the damage field variables. When using the interleaved algorithm, the most convenient feature is that the final discrete form of the momentum is solved linearly without the need for any iterative process.

[0193] Method for determining whether muscle tissue of a driver who drives a car for a long time or for a long period of time is damaged according to the strain energy density model of latent damage caused by long-term driving based on an energy limiter:

[0194] When a driver drives a car for a long time, since the driver maintains a fixed posture for a long time, the muscles in his neck, shoulders and waist are in a state of static muscle tension. The harmful substances in muscle metabolism cause chronic damage to local tissues, resulting in a decrease in muscle elasticity and flexibility, causing pain and injury in related parts.

[0195] A human-machine model is established in the system, and the standing human body skeletal muscle model in the system model library is secondary developed. Based on this, the simulation model is made more consistent with the driver's actual driving posture by modifying seat parameters, adding steering wheel and pedal models, and adjusting the connection points between the human body and the environment.

[0196] Step 51, in the new strain energy density function, the constitutive law of the energy limitation theory is different from the traditional constitutive law because there is a new term in its formula, namely This additional exponential term plays an important role in capturing the softening of the material during loading. The damage variable is defined based on the new strain energy density function.

[0197]

[0198] Where d represents the damage variable, Φ represents the energy limiter, and W′ is the traditional strain energy density function.

[0199] The damage variable d is defined as follows: when the muscle tissue is in an undamaged state, d = 0; when the squeeze on the driver's neck, shoulder, and waist muscles exceeds the energy of the energy limiter while the car is driving, the muscles in the relevant parts are in a damaged state. As the strain increases, the muscle damage worsens, and d gradually increases until d = 1.

[0200] In step 52, the damage variable is driven by the reference strain energy density function, and the reference strain energy density function is decomposed into:

[0201]

[0202] Where W + (ε) represents the reference strain energy density function, λ and μ represent Poisson's ratio, A positive reference quantity representing the square of the trace of strain, represents the trace of the square of the positive reference strain, E1, E2, E3 represent the strains, represents the square of the positive reference strain, represents the square of the positive reference strain, represents the square of the positive reference strain;

[0203] Step 53, redefine the damage variable as:

[0204]

[0205] Where, is the local history quantity of the historical strain energy density function, where: W + represents the positive part of the complete strain energy density function,

[0206] In step 54, based on the historical strain energy density function and the local historical quantity of the historical strain energy density function, the inequality relationship satisfied by the loading function is:

[0207]

[0208] Where, Indicates the loading function, express The derivative of .

[0209] The final form of the damage variable is:

[0210]

[0211] Step 55, transform the equation of motion into weak form:

[0212]

[0213] Where Ω represents the boundary condition, ρ represents the mass density, is the acceleration field, δu represents the displacement test function, u represents the displacement field, v represents the velocity field, σ represents the Cauchy stress tensor, : represents the double dot product, Represents the gradient.

[0214] Step 56: Use standard four-node quadrilateral elements to perform spatial discretization. The discretization formula is as follows:

[0215]

[0216] in:

[0217]

[0218] Where a represents the acceleration field, N u represents the shape function matrix, represents the node acceleration, v represents the acceleration field, represents the node velocity, u represents the displacement field, represents the node displacement, δu represents the displacement field test function, represents the node displacement test function, represents the displacement gradient, B u represents the gradient of the shape function, represents the node displacement, represents the node displacement test function gradient, Represents the node displacement test function, N I is the shape function of the Q4 element, I=1:4, is the gradient of the shape function in the x1(x2) direction.

[0219] Step 57, the discretized formula is brought into the weak form of the governing equation. The discretized form of the weak form is described at the element level, and we can obtain:

[0220]

[0221] Among them, Ω e represents the boundary conditions, ρ represents the mass density, b represents the object force vector, represents external tension, σ represents stress, {σ}=[σ 11 σ 22 σ 12 ] T ;

[0222] Transform the above formula into:

[0223]

[0224] Where, M, F int、F ext are the consistent mass matrix, the internal force vector, and the time-varying external force vector, respectively. Their specific forms are as follows:

[0225]

[0226] Step 58: Discretize the equation of motion in time:

[0227]

[0228] Where M n+1 represents the consistent mass matrix of n+1 steps, represents the approximate value of the n+1 step acceleration, represents the internal force vector of n+1 steps, Represents the external force matrix with n+1 steps.

[0229] In step 59, by using the Newmark-Beta method, at a specific time increment t n -t n+1 and when Δt=t n -t n-1 When , the velocity and acceleration are approximately:

[0230]

[0231] Where, It represents the approximate value of n+1 step acceleration, a0 represents the technical parameters, represents the node displacement at time n, a2 represents the technical parameter, a3 represents the technical parameter, It represents the approximate value of n+1 step speed, a1 represents the technical parameter, a4 represents the technical parameter, and a5 represents the technical parameter.

[0232] Step 510: Substitute the approximate value of acceleration into the time-discretized motion equation to obtain:

[0233]

[0234] Step 511: directly estimate the time t by combining the interleaved format algorithm n+1 The displacement field at :

[0235]

[0236] Where, Represents the stiffness matrix at time n+1.

[0237] The staggered format is used to solve the governing equations. The process of solving the equations of motion is divided into two parts. First, the displacement u, velocity v and acceleration a are updated, and then the history and damage field variables are calculated. At a specific time increment t n -tn+1 (t n+1 >t n ). At time t n When the staggered solution assumes that all field variables include a n , v n ,u n , d n and The specific analysis methods and algorithms are shown in Tables 1 and 2.

[0238] Table 1 Damage methods based on energy limiters

[0239]

[0240]

[0241] Table 2 Finite element solution algorithm

[0242]

[0243]

[0244] In another embodiment, a system for determining hidden injuries caused by long-term driving based on an energy limiter is provided, comprising an acquisition unit, a nonlinear hyperelastic model unit for human muscle tissue, a tangent elastic tensor unit, a strain energy density model unit for hidden injuries caused by long-term driving based on an energy limiter, a damage determination unit, and an output unit, wherein:

[0245] The collecting unit is used to collect driving posture.

[0246] The human muscle tissue nonlinear hyperelastic model unit is used to determine the human muscle tissue nonlinear hyperelastic model according to the hyperelastic characteristics of the human muscle tissue.

[0247] The tangent elastic tensor unit is used to determine the tangent elastic tensor according to a nonlinear hyperelastic model of human muscle tissue.

[0248] The tangent elastic tensor is:

[0249]

[0250] in, represents the tangent elastic tensor, C1 is the material constant of human muscle tissue, C2 is the material constant of human muscle tissue, E 11 、E 22 、E 33 represents the Green strain tensor.

[0251] The strain energy density model unit for hidden damage caused by long-term driving with an energy limiter is used to introduce an energy limiter based on the obtained tangent elastic tensor and establish a strain energy density model for hidden damage caused by long-term driving with an energy limiter on the basis of a traditional strain energy density function.

[0252] The strain energy density model of hidden damage caused by long-term driving based on the energy limiter is:

[0253]

[0254] Where, represents the new strain energy density function, Φ represents the energy limiter, represents the tangent elastic tensor, E ij 、E kl Represents the Green strain tensor, i, j, k, l represent free indices (range 1-3), 0≤ε≤λ p ,λ p represents the total elongation of the sarcomere;

[0255] The damage judgment unit is used to determine whether the muscle tissue of the driver who drives the car for a long time or for a long period of time is damaged according to the driving posture and the strain energy density model of latent damage caused by long-term driving based on the energy limiter.

[0256] The nonlinear hyperelastic model of human muscle tissue is:

[0257]

[0258] Where W is the strain energy function, C1 is the material constant one of human muscle tissue, C2 is the material constant two of human muscle tissue, and I1 is the first principal invariant of the strain tensor.

[0259] The output unit is used to output damage information.

[0260] It also includes a human-machine model unit, which establishes a "driver-seat-steering wheel-accelerator pedal" coupled simulation model based on a standing human body skeletal muscle model by modifying seat parameters, adding a steering wheel pedal model, and adjusting the connection points between the human body and the environment.

[0261] This invention uses a staggered grid algorithm to solve the governing equations, further improving the model of latent damage to drivers during driving. Long-term or extended driving inevitably causes some damage to the driver's body. The latent damage model established by this invention can be used to correlate the existing human muscle tissue model with latent damage, resulting in an energy limiter-based latent damage model and analysis method.

[0262] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A long-time driving hidden damage determination system based on an energy limiter, characterized in that: It includes an acquisition unit, a nonlinear hyperelastic model unit of human muscle tissue, a tangent elastic tensor unit, a strain energy density model unit of latent damage caused by long-term driving based on an energy limiter, a damage judgment unit, and an output unit, wherein: The collecting unit is used to collect driving posture; The human muscle tissue nonlinear hyperelastic model unit is used to determine the human muscle tissue nonlinear hyperelastic model according to the hyperelastic characteristics of the human muscle tissue; The tangent elastic tensor unit is used to determine the tangent elastic tensor according to the nonlinear hyperelastic model of human muscle tissue; The strain energy density model unit for hidden damage caused by long-term driving with an energy limiter is used to introduce an energy limiter based on the obtained tangent elastic tensor and establish a strain energy density model for hidden damage caused by long-term driving with an energy limiter on the basis of a traditional strain energy density function; The damage judgment unit is used to determine whether the muscle tissue of the driver who drives the car for a long time or for a long period of time is damaged according to the driving posture and the strain energy density model of latent damage caused by long-term driving based on the energy limiter; The output unit is used to output damage information.

2. The long-term driving hidden damage determination system based on the energy limiter according to claim 1 is characterized by: The strain energy density model of hidden damage caused by long-term driving based on the energy limiter is: Where, represents the new strain energy density function, Φ represents the energy limiter, represents the tangent elastic tensor, E ij 、E kl represents the Green strain tensor, i, j, k, l represent free indices, 0≤ε≤λ p ,λ p represents the total elongation of the sarcomere.

3. The long-term driving hidden damage determination system based on the energy limiter according to claim 2 is characterized in that: The nonlinear hyperelastic model of human muscle tissue is: Where W is the strain energy function, C1 is the material constant one of human muscle tissue, C2 is the material constant two of human muscle tissue, and I1 is the first principal invariant of the strain tensor.

4. The long-term driving hidden damage determination system based on the energy limiter according to claim 3 is characterized by: The tangent elastic tensor is: in, represents the tangent elastic tensor, C1 is the material constant of human muscle tissue, C2 is the material constant of human muscle tissue, E 11 、E 22 、E 33 represents the Green strain tensor.

5. The long-time driving hidden damage determination system based on energy limiter according to claim 4 is characterized in that: Method for determining the tangent elastic tensor based on the nonlinear hyperelastic model of human muscle tissue: Step 31: In a fixed three-dimensional space coordinate system, assume that the coordinates of a particle in the initial configuration are M0 = (X, Y, Z), and the coordinates of the configuration at time t are M t =(x, y, z), M t The partial derivative about M0 is called the deformation gradient F of the object; The deformation gradient of the object: Where F is the deformation gradient of the object, M t is the coordinate of the particle at time t, M0 is the coordinate of the particle in the initial configuration; Step 32, obtaining the right Cauchy-Green strain tensor C according to the deformation gradient of the object, and then obtaining the Green strain tensor E; The relationship between the Green strain tensor E and the Cauchy-Green strain tensor C is: Step 33, obtaining the tangent elastic tensor with respect to the Green's strain tensor and the second kind of stress tensor according to the constitutive relationship between the Green's strain tensor and the second kind of stress tensor; The second-order tensor form of Green's strain is as follows: The second-order tensor of Green's strain has nine components and is a symmetric tensor, so it can be expressed in the following first-order tensor form: E = [E 11 E 22 E 33 2E 23 2E 13 2E 12 ] T ; The first-order tensor form of the second-order stress tensor T, which is conjugate to the Green strain tensor, is as follows: T=[T 11 T 22 T 33 T 23 T 13 T 12 ] T ; The incremental form of the constitutive relation between the Green strain tensor and the second kind stress tensor T is: Where, dT ij represents the differential of the second kind stress tensor, T ij represents the stress tensor of the second kind, represents the tangent elastic tensor, dE kl represents the differential of the Green strain tensor, E kl represents the Green strain tensor, i, j, k, l represent free indices; From the energy perspective, according to the definition of the hyperelastic model, the Green strain tensor and the second-type stress tensor T also satisfy the following constitutive relations: Where W is the strain energy function; Then we get the expression of the tangent elastic tensor: Step 34: Based on the nonlinear hyperelastic model of human muscle tissue, the relationship between the strain tensor, the first principal invariant, and the Green strain matrix is ​​obtained as follows: I1=3+2(E 11 +E 22 +E 33 ); Substituting I1 into the nonlinear hyperelastic model of human muscle tissue yields: Step 35, the transformed nonlinear hyperelastic model of human muscle tissue is brought into the constitutive relation of Green's strain and the second-type stress tensor T to obtain the second-type stress tensor matrix: Since the second kind of stress tensor matrix is ​​a symmetric matrix, it can be written as follows: Step 36: According to the expression of the tangent elastic tensor, the tangent elastic tensor matrix of the following form is obtained: in, represents the tangent elastic tensor, C1 is the material constant of human muscle tissue, C2 is the material constant of human muscle tissue, E 11 、E 22 、E 33 represents the Green strain tensor.

6. The long-time driving hidden damage determination system based on energy limiter according to claim 5 is characterized in that: Method for establishing a strain energy density model for latent damage during long-term driving based on an energy limiter: Step 41: According to the energy limiter theory, a new strain energy density function is obtained: Where, represents the new strain energy density function, Φ represents the energy limiter, and W′ is the traditional strain energy density function; Step 42: Substitute the traditional strain energy density function formula into the new strain energy density function: Where, represents the new strain energy density function, Φ represents the energy limiter, represents the tangent elastic tensor, E ij 、E kl represents the Green strain tensor, 0≤ε≤λ p ,λ p represents the total elongation of the sarcomere, Table tangent elastic tensor.

7. The long-time driving hidden damage determination system based on energy limiter according to claim 6 is characterized in that: Method for determining whether muscle tissue of a driver who drives a car for a long time or for a long period of time is damaged according to the strain energy density model of latent damage caused by long-term driving based on an energy limiter: Step 51, defining damage variables according to the new strain energy density function; Where d represents the damage variable, Φ represents the energy limiter, and W′ is the traditional strain energy density function; In step 52, the damage variable is driven by the reference strain energy density function, and the reference strain energy density function is decomposed into: Where W + (ε) represents the reference strain energy density function, λ and μ represent Poisson's ratio, A positive reference quantity representing the square of the trace of strain, represents the trace of the square of the positive reference strain, E1, E2, E3 represent the strains, represents the square of the positive reference strain, represents the square of the positive reference strain, represents the square of the positive reference strain; Step 53, redefine the damage variable as: Where, is the local history quantity of the historical strain energy density function, where: represents the positive part of the complete strain energy density function, In step 54, based on the historical strain energy density function and the local historical quantity of the historical strain energy density function, the inequality relationship satisfied by the loading function is: Where, Indicates the loading function, express The derivative of Step 55, transform the equation of motion into weak form: Where Ω represents the boundary condition, ρ represents the mass density, is the acceleration field, δu represents the displacement test function, u represents the displacement field, v represents the velocity field, σ represents the Cauchy stress tensor, : represents the double dot product, and ▽ represents the gradient; Step 56: Use standard four-node quadrilateral elements to perform spatial discretization. The discretization formula is as follows: in: Where a represents the acceleration field, N u represents the shape function matrix, represents the node acceleration, v represents the acceleration field, represents the node velocity, u represents the displacement field, represents the node displacement, δu represents the displacement field test function, represents the node displacement test function, represents the displacement gradient, B u represents the shape function gradient, represents the node displacement, represents the gradient of the node displacement test function, Represents the node displacement test function, N I is the shape function of the Q4 element, I=1:4, is the gradient of the shape function in the x1(x2) direction; Step 57, the discretized formula is brought into the weak form of the governing equation. The discretized form of the weak form is described at the element level, and we can obtain: Among them, Ω e represents the boundary conditions, ρ represents the mass density, b represents the object force vector, represents external tension, σ represents stress, {σ}=[σ 11 σ 22 σ 12 ] T ; Transform the above formula into: Where, M, F int 、F ext are the consistent mass matrix, the internal force vector, and the time-varying external force vector, respectively. Their specific forms are as follows: Step 58: Discretize the equation of motion in time: Where M n+1 represents the consistent mass matrix of n+1 steps, represents the approximate value of the n+1 step acceleration, represents the internal force vector of n+1 steps, represents the external force matrix of n+1 steps; In step 59, by using the Newmark-Beta method, at a specific time increment t n -t n+1 and when Δt=t n -t n-1 When , the velocity and acceleration are approximately: Where, It represents the approximate value of n+1 step acceleration, a0 represents the technical parameters, represents the node displacement at time n, a2 represents the technical parameter, a3 represents the technical parameter, It represents the approximate value of the n+1 step speed, a1 represents the technical parameter, a4 represents the technical parameter, and a5 represents the technical parameter; Step 510: Substitute the approximate value of acceleration into the time-discretized motion equation to obtain: Step 511: directly estimate the time t by combining the interleaved format algorithm n+1 The displacement field at : Where, Represents the stiffness matrix at time n+1.

8. The long-time driving hidden damage determination system based on energy limiter according to claim 7 is characterized in that: It also includes a human-machine model unit, which establishes a "driver-seat-steering wheel-accelerator pedal" coupled simulation model based on a standing human body skeletal muscle model by modifying seat parameters, adding a steering wheel and pedal model, and adjusting the connection points between the human body and the environment.

9. The long-time driving hidden damage determination system based on energy limiter according to claim 8, characterized in that: The damage variable d is defined as follows: when the muscle tissue is in an undamaged state, d = 0; when the squeeze on the driver's neck, shoulder, and waist muscles exceeds the energy of the energy limiter while the car is driving, the muscles in the relevant parts are in a damaged state. As the strain increases, the muscle damage worsens, and d gradually increases until d = 1.

10. A method for determining hidden damage during long-term driving based on an energy limiter, characterized by: The system for determining hidden damage during long-term driving based on an energy limiter according to any one of claims 1 to 8 comprises the following steps: Step 1: Collect driving posture; Step 2, determining a nonlinear hyperelastic model of human muscle tissue according to the hyperelastic characteristics of human muscle tissue; Step 3, determining the tangent elastic tensor based on the nonlinear hyperelastic model of human muscle tissue; Step 4: Based on the obtained tangent elastic tensor and the traditional strain energy density function, an energy limiter is introduced to establish a strain energy density model of latent damage caused by long-term driving based on the energy limiter; Step 5: determining whether the driver's muscle tissue is damaged due to long-term or long-term driving according to the driving posture and the strain energy density model of latent damage caused by long-term driving based on the energy limiter.

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