Sofa ergonomics evaluation method and device based on musculoskeletal model flexible simulation

Abstract

The application discloses a sofa ergonomics evaluation method and device based on a flexible simulation of a musculoskeletal model, and the method comprises the following steps: establishing a human simplified model, and setting size parameters of the human simplified model; placing the human simplified model on a sofa finite element model with a real sitting posture of a human body as an initial posture, and calculating postures, forces and force points of each limb of the human simplified model in a static state; importing the size parameters, the postures, the forces and the force points of each limb into a human musculoskeletal model, and obtaining muscle forces required by each muscle of the human musculoskeletal model in a posture stable condition; performing ergonomics evaluation of sofa design on the sofa finite element model according to the muscle forces of the human musculoskeletal model, and outputting an evaluation result. The application solves the problems that interaction between a deformable body and a human body is difficult to measure and calculate, and that an ergonomics effect in a sofa design stage cannot be evaluated in advance.

Description

Technical Field

[0001] This invention belongs to the field of ergonomic simulation analysis technology, specifically relating to a sofa ergonomic evaluation method and device based on musculoskeletal model flexible simulation. Background Technology

[0002] Ergonomics research methods and evaluation systems were first used in automotive seat evaluation and have gradually been extended to furniture evaluation. Ergonomics studies various anatomical, physiological, and psychological factors of humans in a certain work environment; it studies the interaction between humans, machines, and the environment; and it studies how to comprehensively consider work efficiency, human health, safety, and comfort in work, family life, and vacation. Furniture comfort evaluation falls entirely within the scope of ergonomics; however, how to conduct such evaluations remains a challenge.

[0003] Traditional evaluation methods include user surveys, experimental measurement evaluation, and virtual environment simulation analysis. User surveys require extensive user experience and feedback, offering the advantage of directly and effectively understanding customers' real feelings and operational shortcomings. However, they are unsuitable for small-batch, customized products and cannot be improved in advance during the design phase. Experimental measurement evaluation involves building a test environment filled with sensors based on a real-world environment. Various parameters of the tested tools and human operation methods are tested in this potentially adjustable environment. The user experience is analyzed based on the measured sensor signals and human body models. However, this method requires significant investment in funding and technology. Virtual environment simulation analysis includes multibody dynamics simulation analysis, finite element simulation analysis, rigid body simulation analysis, and musculoskeletal model simulation analysis. Musculoskeletal model simulation can effectively and intuitively understand the activation state of human muscles during dynamic processes and is often used in professional biomechanical research. However, this type of simulator lacks technical support for soft body simulation and currently does not support interactive simulation analysis of the human body and deformable objects. Summary of the Invention

[0004] One of the objectives of this invention is to provide a sofa ergonomics evaluation method based on musculoskeletal model flexible simulation, which solves the problem of difficulty in measuring and calculating the interaction between deformable bodies and the human body, and solves the problem of the inability to pre-evaluate the ergonomic effects during the sofa design stage.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for evaluating sofa ergonomics based on musculoskeletal model flexibility simulation, the method comprising:

[0007] Create a simplified human body model and set its dimensional parameters;

[0008] Using the actual sitting posture of the human body as the initial posture, a simplified human body model is placed on a sofa finite element model, and the posture, force and force application point of each limb of the simplified human body model in a static state are calculated.

[0009] The size parameters, postures of each limb, forces, and points of force application are imported into the human musculoskeletal model to obtain the muscle forces required by each muscle in the whole body under the condition of stable posture of the human musculoskeletal model.

[0010] Based on the muscle forces of the human musculoskeletal model, an ergonomic evaluation of the sofa design is performed on the finite element model of the sofa, and the evaluation results are output.

[0011] Several alternative methods are provided below, but they are not intended as additional limitations on the overall solution above. They are merely further additions or optimizations. Provided there are no technical or logical contradictions, each alternative method can be combined individually with respect to the overall solution above, or multiple alternative methods can be combined with each other.

[0012] Preferably, setting the size parameters of the simplified human body model includes:

[0013] Obtain actual human anatomical parameters and apply them to simplified human models;

[0014] The weight and center of gravity of each limb of the simplified human model are calculated and set according to the actual human anatomical structure parameters.

[0015] Preferably, the actual human sitting posture includes the posture of each limb and the joint angle of each joint when a person is sitting on a sofa.

[0016] Preferably, placing the simplified human body model onto the sofa finite element model with the actual human sitting posture as the initial posture includes:

[0017] Set the sofa finite element model as a finite element type soft body, and set the material deformation properties of the sofa finite element model according to the actual sofa material type;

[0018] Set the simplified human body model to the rigid body Articulation type, and apply the real human sitting posture to the simplified human body model;

[0019] Modify the joint angle constraints of the simplified human body model to limit the joint angle constraints between adjacent limbs to hinge joints that rotate with a single degree of freedom in the sagittal plane of the human body. Then place the simplified human body model on the sofa finite element model.

[0020] Preferably, the calculation of the posture, forces, and points of force application of each limb in the static state of the simplified human body model includes:

[0021] The posture of each limb in a simplified human body model at rest was calculated using a flexible simulator;

[0022] Calculate the resultant force and the point of application of the resultant force on each limb of the simplified human body model after the sofa finite element model has deformed, including:

[0023] For each finite element in the sofa finite element model, the normal stress σ in the xyz direction is solved based on the equilibrium equation. x σ y σ z and tangential stress τ xy τ xz τ yz Query all finite element cells i If it comes into contact with a specified limb j of a simplified human model, it is placed into set S. j ;

[0024] 1) The resultant force F exerted by the sofa finite element model on limb j j for:

[0025]

[0026]

[0027] In the formula, For finite element cell i The force exerted on limb j, sign(i x ), sign(i y ), sign(i z The x, y, and z axes are sign functions, respectively, and their values ​​depend on the finite element cell. i The value of the contact surface normal of limb j is 1 when it is aligned with the contact surface normal, and 0 otherwise.

[0028] 2) The point of application of the resultant force of the sofa finite element model on limb j is:

[0029]

[0030] In the formula, p j o is the point of application of the resultant force of the sofa finite element model on limb j. j Let M be the coordinates of the centroid of limb j. j1 M j2 Let J represent the torques of the proximal and distal joints on limb j, respectively. The calculation formula is as follows:

[0031] M j1 =F j1 ·|p j1 -o j |·sinθ1

[0032] M j2 =Fj2 ·|p j2 -o j |·sinθ2

[0033] In the formula, F j1 F j2 The forces exerted by the proximal and distal joints on limb j are respectively, p j1 p j2 These are the coordinates of the proximal and distal joints, respectively, where θ1 and θ2 are the coordinates of F. j1 With p j1 -o j The included angle and F j2 With p j2 -o j The included angle.

[0034] The sofa ergonomics evaluation method based on musculoskeletal model flexibility simulation provided by this invention has the following advantages compared with the prior art:

[0035] 1. The simulation starts with a sitting posture based on the tester's actual measurement posture, which can effectively preserve the tester's sitting habits and manner in the simulation, making the simulation highly realistic and credible;

[0036] 2. It integrates soft body simulation and musculoskeletal simulation technologies. The force connection of soft body simulation is applied to the next step of musculoskeletal simulation, which solves the problem that musculoskeletal simulation cannot support soft body simulation.

[0037] 3. The sofa flexible finite element simulation supports the adjustment of the size and material parameters of the simulated sofa model. That is, the simulation can use design data, and the final result can guide the design in advance and then carry out production and processing, reducing the trial and error costs of enterprises.

[0038] 4. The muscle force and muscle group coordination obtained by musculoskeletal simulation calculation are used to assess comfort. The quantitative indicators are scientifically evaluated from a biomechanical perspective, and the results are intuitive and reliable.

[0039] 5. In the process of sofa soft body finite element simulation, the human body posture is further adaptively adjusted with the deformation of the sofa. The premise is that the muscles relax and adjust with the deformation of the sofa and the human body will not make flipping or swaying movements. This is consistent with the goal of ergonomic evaluation that muscles should save effort. This step can make up for the error between simulation and real environment.

[0040] The second objective of this invention is to provide a sofa ergonomics evaluation device based on flexible simulation of a musculoskeletal model, which solves the problem of difficulty in measuring and calculating the interaction between deformable bodies and the human body, and solves the problem of the inability to pre-evaluate the ergonomic effects during the sofa design stage.

[0041] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0042] A sofa ergonomics evaluation device based on musculoskeletal model flexible simulation, the sofa ergonomics evaluation device based on musculoskeletal model flexible simulation includes:

[0043] The model building module is used to create a simplified human body model and set the size parameters of the simplified human body model;

[0044] The limb force analysis module is used to place a simplified human body model on a sofa finite element model with the human body's actual sitting posture as the initial posture, and to calculate the posture, force, and force application point of each limb of the simplified human body model in a static state.

[0045] The muscle force acquisition module is used to import the size parameters, postures of each limb, forces and force application points into the human musculoskeletal model to obtain the muscle force required by each muscle in the whole body under the condition of stable posture of the human musculoskeletal model.

[0046] The evaluation module is used to perform an ergonomic evaluation of the sofa design based on the muscle forces of the human musculoskeletal model and output the evaluation results.

[0047] Preferably, the model building module sets the size parameters of the simplified human body model and performs the following operations:

[0048] Obtain actual human anatomical parameters and apply them to simplified human models;

[0049] The weight and center of gravity of each limb of the simplified human model are calculated and set according to the actual human anatomical structure parameters.

[0050] Preferably, the actual human sitting posture includes the posture of each limb and the joint angle of each joint when a person is sitting on a sofa.

[0051] Preferably, the limb force analysis module places a simplified human body model onto a sofa finite element model with the actual human sitting posture as the initial posture, and performs the following operations:

[0052] Set the sofa finite element model as a finite element type soft body, and set the material deformation properties of the sofa finite element model according to the actual sofa material type;

[0053] Set the simplified human body model to the rigid body Articulation type, and apply the real human sitting posture to the simplified human body model;

[0054] Modify the joint angle constraints of the simplified human body model to limit the joint angle constraints between adjacent limbs to hinge joints that rotate with a single degree of freedom in the sagittal plane of the human body. Then place the simplified human body model on the sofa finite element model.

[0055] Preferably, the limb force analysis module calculates the posture, force, and point of force application of each limb in a static state of the simplified human body model, and performs the following operations:

[0056] The posture of each limb in a simplified human body model at rest was calculated using a flexible simulator;

[0057] Calculate the resultant force and the point of application of the resultant force on each limb of the simplified human body model after the sofa finite element model has deformed, including:

[0058] For each finite element in the sofa finite element model, the normal stress σ in the xyz direction is solved based on the equilibrium equation. x σ y σ z and tangential stress τ xy τ xz τ yz Query all finite element cells i If it comes into contact with a specified limb j of a simplified human model, it is placed into set S. j ;

[0059] 1) The resultant force F exerted by the sofa finite element model on limb j j for:

[0060]

[0061]

[0062] In the formula, For finite element cell i The force exerted on limb j, sign(i x ), sign(i y ), sign(i z The x, y, and z axes are sign functions, respectively, and their values ​​depend on the finite element cell. i The value of the contact surface normal of limb j is 1 when it is aligned with the contact surface normal, and 0 otherwise.

[0063] 2) The point of application of the resultant force of the sofa finite element model on limb j is:

[0064]

[0065] In the formula, p j o is the point of application of the resultant force of the sofa finite element model on limb j. j Let M be the coordinates of the centroid of limb j. j1 M j2 Let J represent the torques of the proximal and distal joints on limb j, respectively. The calculation formula is as follows:

[0066] Mj1 =F j1 ·|p j1 -o j |·sinθ1

[0067] M j2 =F j2 ·|p j2 -o j |·sinθ2

[0068] In the formula, F j1 F j2 The forces exerted by the proximal and distal joints on limb j are respectively, p j1 p j2 These are the coordinates of the proximal and distal joints, respectively, where θ1 and θ2 are the coordinates of F. j1 With p j1 -o j The included angle and F j2 With p j2 -o j The included angle. Attached Figure Description

[0069] Figure 1 This is a flowchart of the sofa ergonomics evaluation method based on musculoskeletal model flexible simulation of the present invention.

[0070] Figure 2 A schematic diagram of the simplified human body model constructed for this invention. Detailed Implementation

[0071] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0072] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to limit the invention.

[0073] To address the ergonomic evaluation issues of existing sofa technologies, this invention integrates soft-body finite element simulation and musculoskeletal simulation technologies into the sofa ergonomic evaluation process. First, the finite element simulation analysis of the sofa is used to obtain the posture of the human body when in contact with the soft body and the interaction force after posture adjustment. This method can also be applied to new soft-body models after adjustments to the size and material parameters of the sofa model. Then, based on the human-computer interaction force calculated by the soft-body finite element analysis, the human musculoskeletal model is simulated to obtain the activation state of muscles and muscle groups. The comfort of the sofa design is quantitatively evaluated based on the muscle force and the degree of muscle group coordination.

[0074] like Figure 1 As shown in this embodiment, the sofa ergonomics evaluation method based on musculoskeletal model flexibility simulation includes the following steps:

[0075] (1) Establish a simplified human body model: such as Figure 2 As shown, the simplified human body model established in this embodiment includes a head (1), torso (2), upper arms (4, 5), forearms (6, 7), hands (8, 9), hips (3), thighs (10, 11), calves (12, 13), and feet (14, 15). The head and hands are modeled using spheres, the upper arms, forearms, thighs, calves, and feet are modeled using frustums of cones, and the torso and hips are modeled using cylinders. Adjacent limbs are connected by ball joints. Each limb can have parameters such as length, diameter, center of gravity position, and weight set.

[0076] (2) Measurement and calculation of model parameters: In this embodiment, when setting the size parameters of the simplified human body model, the human anatomy parameters of the test subject are measured, including height, weight, length of each limb, and diameter of the distal and proximal ends of each limb (ends at different distances from the trunk). The size parameters are applied to the simplified human body model, and the weight of each limb is calculated based on empirical parameters, which are the ratio of limb weight to body weight, including head: 0.081; hand: 0.006; forearm: 0.016; upper arm: 0.028; trunk: 0.355; hip: 0.142; thigh: 0.1; calf: 0.0465; foot: 0.0145. The weight and center of gravity of each limb of the simplified human body model are calculated and set based on the actual human anatomy parameters.

[0077] It should be noted that the process of setting the center of gravity position in this embodiment is based on existing technology, such as the center of gravity position column in Chapter 3, Table 3.2 of the literature "Research Methods in Biomechanics" by D. Gordon Robertson. This will not be elaborated upon further in this embodiment.

[0078] (3) Measuring Human Sofa Sitting Posture: A motion capture system is used to collect the actual sitting posture of the test subject while sitting on a real sofa, including the posture of each limb and the joint angles of each joint, including the posture of the head, torso, upper arm, forearm, palm, hip, thigh, calf, and foot, as well as the joint angles of their constituent joints. The motion capture system can be an optical motion capture system such as Vicon or OptiTrack, or an IMU sensing system such as Xsene or Rokoko's SmartSuit Pro. The joint angles are determined by the posture of the two adjacent limbs connected by the joint, and the joint angles of each joint can be obtained based on the limb posture.

[0079] (4) Setting up the sofa finite element model: In this embodiment, a simplified human body model is placed on the sofa finite element model, using the actual sitting posture of the human body as the initial posture. The sofa finite element model is imported into the soft body simulator. Since the shape may differ from the actual sofa shape in the experiment, the sofa finite element model is set as a finite element type soft body. Based on the actual sofa material type, material deformation properties of the sofa finite element model, such as elastic modulus, strain, and Poisson's ratio, are added to the soft body simulator. The soft body simulator is a simulator that supports finite element simulation, such as Isaac SIM.

[0080] (5) Import and set up the simplified human body model: Import the simplified human body model into the soft body simulator. Set the simplified human body model to the rigid body Articulation type and apply the real sitting posture of the human body to the simplified human body model: Set the length, distal and proximal diameter (frustum) / diameter (cylinder, sphere), weight, and center of gravity position for each limb (including head, torso, upper arm, forearm, palm, hip, thigh, calf, and foot). Apply the test subject's sofa sitting posture to the simplified human body model, that is, set the posture of the head, torso, upper arm, forearm, palm, hip, thigh, calf, and foot and the joint angles of their constituent joints according to the collected test subject posture.

[0081] At the same time, the joint angle constraints of the simplified human body model were modified, and each joint was changed from a ball joint to a hinge joint that can only rotate with a single degree of freedom in the sagittal plane of the human body (facing the human body, it can only swing back and forth, but cannot swing left and right or rotate axially). The set, applied and modified simplified human body model was placed on the sofa finite element model.

[0082] (6) Flexible simulation calculation of human body model posture and force: calculate the posture, force and force application point of each limb of the simplified human body model in a static state.

[0083] Motion simulation is initiated. A simplified human body model, falling due to gravity, exerts pressure on a finite element sofa model, causing deformation. The elastic reaction force generated by the sofa's deformation acts on the simplified human body model. The joints of the simplified human body model can move freely in the sagittal plane. This interaction continues until the joints cease movement and the sofa deformation stops. A flexible simulator records the posture of each limb and the joint angles of each joint of the simplified human body model at this point. The resultant force and point of application of the resultant force applied to each limb of the simplified human body model after sofa deformation are calculated and recorded. The reaction force and point of application of the feet to the ground are also recorded. Rigid body forces, such as the ground reaction force and point of application of the feet, can be directly obtained from the simulator. The forces and points of application of the finite element flexible body on the rigid body can generally be obtained directly from the simulator or calculated. The basic calculation process is as follows:

[0084] Flexible body finite element calculations adhere to three major equation sets: equilibrium equations, geometric equations, and physical equations. The calculations are iterative and unified, with the equilibrium equations used to solve for the normal stress σ. x σ y σ z and tangential stress τ xy τ xz τ yz The geometric equations are used to solve for the displacement components u, v, and w in the x, y, and z directions, while the physical equations are used to solve for the normal strain ε. x ε y ε z and tangential strain γ yz γ zx γ xy Query all finite element cells i If it comes into contact with a specified limb j of a simplified human model, it is placed into set S. j .

[0085] 1) The resultant force F exerted by the sofa finite element model on limb j j for:

[0086]

[0087]

[0088] In the formula, sign(i x ), sign(i y ), sign(i z () is the sign function for the x, y, and z axes, and its value depends on the cell. i The value of the contact surface normal of limb j is 1 when it is aligned with the contact surface normal, and 0 otherwise.

[0089] 2) The point of application of the force exerted by the flexible body on limb j satisfies the condition that the net torque of limb j is equal to zero M. j1 +Mj2 +F j ·(p j -o j ) = 0, meaning the point of application of the resultant force of the sofa finite element model on limb j is:

[0090]

[0091] In the formula, p j o is the point of application of the resultant force of the sofa finite element model on limb j. j Let M be the coordinates of the center of mass (center of gravity position) of limb j. j1 M j2 Let J represent the torques of the proximal and distal joints on limb j, respectively. The calculation formula is as follows:

[0092] M j1 =F j1 ·|p j1 -o j |·sinθ1

[0093] M j2 =F j2 ·|p j2 -o j |·sinθ2

[0094] In the formula, F j1 F j2 The forces exerted by the proximal and distal joints on limb j are respectively, p j1 p j2 θ1 and θ2 are the coordinates of the proximal and distal joints, respectively, which can be obtained from the simulation engine. θ1 and θ2 represent the forces F applied. j1 With p j1 -o j The angle between the two forces and the force F j2 With p j2 -o j The included angle. p j1 -o j That is, the proximal joint coordinate p j1 With the centroid coordinate o j The connection, p j2 -o j That is, the distal joint coordinate p j2 With the centroid coordinates o j The connection.

[0095] (7) Import and set up the human musculoskeletal model: Import the size parameters, postures of each limb, forces and force application points of the simplified human model into the human musculoskeletal model.

[0096] Import a complete human musculoskeletal model into a musculoskeletal simulation software. Set the length, weight, and center of gravity position for each limb / bone (including head, torso, upper arm, forearm, hand, hip, thigh, calf, and foot). Apply the postures or joint angles of each limb of the simplified human model recorded after soft-body simulation to each limb or joint of the musculoskeletal model. Apply the forces exerted by the sofa on each limb calculated by soft-body simulation to the corresponding force application points of each limb of the musculoskeletal model. Apply the ground reaction forces recorded by soft-body simulation to the force application points of the foot of the musculoskeletal model. The human musculoskeletal simulation software can be Anybody or OpenSIM.

[0097] (8) Musculoskeletal model simulation and calculation: In the human musculoskeletal simulation software, start the musculoskeletal model simulation and calculate the muscle force required by each muscle in the whole body to maintain the stability of the musculoskeletal model posture under the above external force conditions.

[0098] (9) Ergonomic Assessment: The ergonomic assessment of the sofa design is based on muscle forces calculated using musculoskeletal simulation, including the magnitude of muscle force and the degree of muscle group coordination. The total muscle force is calculated by summing the individual muscle force values; a smaller total value indicates less work done by the muscles, resulting in a more comfortable sitting posture. The assessment also checks whether any muscle or muscle group has significantly greater force than surrounding muscles and calculates the variance of the muscle force. A smaller variance indicates more uniform muscle force distribution and a higher degree of coordination. The sofa's design rationality is reflected in its support and whether it conforms to the natural, relaxed posture of human joints, thereby reducing muscle exertion.

[0099] It should be noted that the ergonomic evaluation performed in this embodiment can be done manually or by simulation software. For example, human musculoskeletal simulation software does not support soft body simulation, but it is good at ergonomic analysis. Therefore, finite element simulation is used for interaction, and musculoskeletal simulation only performs ergonomic analysis on the interaction results.

[0100] This invention uses musculoskeletal model flexible simulation technology to conduct ergonomic evaluation of deformable furniture such as sofas. The core simulation process includes finite element analysis of the sofa under soft body simulation and adaptive adjustment of human posture, and ergonomic evaluation of the sofa under musculoskeletal model simulation. It solves the problem of difficulty in measuring and calculating the interaction between deformable bodies and the human body, and solves the problem of the inability to pre-evaluate the ergonomic effects during the sofa design stage.

[0101] This embodiment primarily uses a musculoskeletal model to obtain muscle forces, which are then used for sofa ergonomics evaluation. This provides reliable and intuitive basic data for sofa ergonomics evaluation, overcoming the limitation of existing musculoskeletal model simulations that cannot support soft-body simulation. This embodiment does not impose any restrictions on the specific methods used for sofa ergonomics evaluation.

[0102] In other words, based on the sofa ergonomic evaluation method based on musculoskeletal model flexible simulation provided in this application, a musculoskeletal model flexible simulation method can be extended to overcome the limitation that existing musculoskeletal model simulation cannot support soft body simulation. The specific simulation steps may include: establishing a simplified human body model and setting the dimensional parameters of the simplified human body model; placing the simplified human body model on the sofa finite element model with the actual sitting posture as the initial posture, and calculating the posture, force, and force application point of each limb in the static state of the simplified human body model; importing the dimensional parameters, the posture, force, and force application point of each limb into the human musculoskeletal model to obtain the muscle force required by each muscle in the whole body under the stable posture condition of the human musculoskeletal model.

[0103] The aforementioned flexible simulation method based on a musculoskeletal model achieves flexible simulation to obtain muscle forces, which can be used for sofa ergonomics evaluation research or other applications. When used for sofa ergonomics evaluation research, a neural network can also be introduced as an evaluation carrier. The neural network can be pre-trained using a muscle force dataset, and the muscle forces of the human musculoskeletal model can be input into the pre-trained neural network, which will then output the evaluation results.

[0104] In another embodiment, this application also provides a sofa ergonomics evaluation device based on musculoskeletal model flexibility simulation, comprising:

[0105] The model building module is used to create a simplified human body model and set the size parameters of the simplified human body model;

[0106] The limb force analysis module is used to place a simplified human body model on a sofa finite element model with the human body's actual sitting posture as the initial posture, and to calculate the posture, force, and force application point of each limb of the simplified human body model in a static state.

[0107] The muscle force acquisition module is used to import the size parameters, postures of each limb, forces and force application points into the human musculoskeletal model to obtain the muscle force required by each muscle in the whole body under the condition of stable posture of the human musculoskeletal model.

[0108] The evaluation module is used to perform an ergonomic evaluation of the sofa design based on the muscle forces of the human musculoskeletal model and output the evaluation results.

[0109] For specific limitations regarding the sofa ergonomics evaluation device based on musculoskeletal model flexible simulation, please refer to the limitations of the sofa ergonomics evaluation method based on musculoskeletal model flexible simulation mentioned above, which will not be repeated here.

[0110] In one specific embodiment, the model building module sets the size parameters of the simplified human body model and performs the following operations:

[0111] Obtain actual human anatomical parameters and apply them to simplified human models;

[0112] The weight and center of gravity of each limb of the simplified human model are calculated and set according to the actual human anatomical structure parameters.

[0113] In one specific embodiment, the actual sitting posture of a human body includes the posture of each limb and the joint angle of each joint when a human body is sitting on a sofa.

[0114] In one specific embodiment, the limb force analysis module places a simplified human body model onto a sofa finite element model with the actual human sitting posture as the initial posture, and performs the following operations:

[0115] Set the sofa finite element model as a finite element type soft body, and set the material deformation properties of the sofa finite element model according to the actual sofa material type;

[0116] Set the simplified human body model to the rigid body Articulation type, and apply the real human sitting posture to the simplified human body model;

[0117] Modify the joint angle constraints of the simplified human body model to limit the joint angle constraints between adjacent limbs to hinge joints that rotate with a single degree of freedom in the sagittal plane of the human body. Then place the simplified human body model on the sofa finite element model.

[0118] In one specific embodiment, the limb force analysis module calculates the posture, force, and point of force application of each limb in a static state of a simplified human body model, and performs the following operations:

[0119] The posture of each limb in a simplified human body model at rest was calculated using a flexible simulator;

[0120] Calculate the resultant force and the point of application of the resultant force on each limb of the simplified human body model after the sofa finite element model has deformed, including:

[0121] For each finite element in the sofa finite element model, the equilibrium equations are used to solve for the normal stress σ. x σ y σ z and tangential stress τ xy τ xz τ yz The geometric equations are used to solve for the displacement components u, v, and w in the x, y, and z directions, while the physical equations are used to solve for the normal strain ε. x ε y ε z and tangential strain γ yz γ zx γ xy Query all finite element cells iIf it comes into contact with a specified limb j of a simplified human model, it is placed into set S. j ;

[0122] 1) The resultant force F exerted by the sofa finite element model on limb j j for:

[0123]

[0124]

[0125] In the formula, sign(i x ), sign(i y ), sign(i z () is the sign function for the x, y, and z axes, and its value depends on the cell. i The value of the contact surface normal of limb j is 1 when it is aligned with the contact surface normal, and 0 otherwise.

[0126] 2) The point of application of the resultant force of the sofa finite element model on limb j is:

[0127]

[0128] In the formula, p j o is the point of application of the resultant force of the sofa finite element model on limb j. j Let M be the coordinates of the centroid of limb j. j1 M j2 Let J represent the torques of the proximal and distal joints on limb j, respectively. The calculation formula is as follows:

[0129] M j1 =F j1 ·|p j1 -o j ·|sinθ1

[0130] M j2 =F j2 ·|p j2 -o j |·sinθ2

[0131] In the formula, F j1 F j2 The forces exerted by the proximal and distal joints on limb j are respectively, p j1 p j2 These are the coordinates of the proximal and distal joints, respectively, where θ1 and θ2 are the coordinates of F. j1 With p j1 -o j The included angle and F j2 With p j2 -o j The included angle.

[0132] The modules in the aforementioned sofa ergonomics evaluation device based on musculoskeletal model flexibility simulation can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in or independent of the processor in a computer device, or stored in the computer device's memory as software, so that the processor can call and execute the corresponding operations of each module.

[0133] The memory may be, but is not limited to, Random Access Memory (RAM), Read Only Memory (ROM), Programmable Read-Only Memory (PROM), Erasable Programmable Read-Only Memory (EPROM), Electrically Erasable Programmable Read-Only Memory (EEPROM), etc. The memory stores the program, and the processor executes the program upon receiving an execution instruction.

[0134] The processor may be an integrated circuit chip with data processing capabilities. The aforementioned processor can be a general-purpose processor, including a Central Processing Unit (CPU), a Network Processor (NP), etc. It can implement or execute the methods, steps, and logic block diagrams disclosed in the embodiments of this invention. The general-purpose processor can be a microprocessor or any conventional processor.

[0135] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0136] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A method for evaluating sofa ergonomics based on musculoskeletal model flexibility simulation, characterized in that, The sofa ergonomics evaluation method based on musculoskeletal model flexibility simulation includes: Create a simplified human body model and set its dimensional parameters; Using the actual sitting posture of the human body as the initial posture, a simplified human body model is placed on a sofa finite element model, and the posture, force and force application point of each limb of the simplified human body model in a static state are calculated. The size parameters, postures of each limb, forces, and points of force application are imported into the human musculoskeletal model to obtain the muscle forces required by each muscle in the whole body under the condition of stable posture of the human musculoskeletal model. Based on the muscle forces of the human musculoskeletal model, an ergonomic evaluation of the sofa design is performed on the finite element model of the sofa, and the evaluation results are output. The step of placing a simplified human body model onto a sofa finite element model using the actual human sitting posture as the initial posture includes: Set the sofa finite element model as a finite element type soft body, and set the material deformation properties of the sofa finite element model according to the actual sofa material type; Set the simplified human body model to the rigid body Articulation type, and apply the real human sitting posture to the simplified human body model; Modify the joint angle constraints of the simplified human body model to limit the joint angle constraints between adjacent limbs to hinge joints that rotate with a single degree of freedom in the sagittal plane of the human body, and then place the simplified human body model on the sofa finite element model. The calculation of the posture, forces, and points of application of each limb in a simplified human body model at rest includes: Motion simulation is initiated. The simplified human body model falls under gravity, exerting pressure on the sofa finite element model, causing the sofa finite element model to deform. The elastic reaction force generated by the deformation of the sofa finite element model acts on the simplified human body model. The joints of the simplified human body model move freely in the sagittal plane. The interaction continues until the joints stop moving and the deformation of the sofa finite element model no longer changes. Based on the flexible simulator, the posture of each limb of the simplified human body model and the joint angle of each joint are recorded at this time. The resultant force and the point of application of the resultant force applied to each limb of the simplified human body model after the deformation of the sofa finite element model are calculated and recorded. The reaction force and the point of application of the force on the sole of the foot are also recorded.

2. The sofa ergonomics evaluation method based on musculoskeletal model flexibility simulation as described in claim 1, characterized in that, Setting the size parameters of the simplified human body model includes: Obtain actual human anatomical parameters and apply them to simplified human models; The weight and center of gravity of each limb of the simplified human model are calculated and set according to the actual human anatomical structure parameters.

3. The sofa ergonomics evaluation method based on musculoskeletal model flexibility simulation as described in claim 1, characterized in that, The actual human sitting posture includes the posture of each limb and the joint angle of each joint when a person is sitting on a sofa.

4. The sofa ergonomics evaluation method based on musculoskeletal model flexibility simulation as described in claim 1, characterized in that, The calculation of the posture, forces, and points of application of each limb in a static state of a simplified human body model includes: The posture of each limb in a simplified human body model at rest was calculated using a flexible simulator; Calculate the resultant force and the point of application of the resultant force on each limb of the simplified human body model after the sofa finite element model has deformed, including: For each finite element in the sofa finite element model, the normal stress in the xyz direction is solved based on the equilibrium equation. , , and tangential stress , , Query all finite element elements If it comes into contact with a specified limb j of a simplified human model, it is placed into the set. ; 1) The resultant force exerted by the sofa finite element model on limb j for: In the formula, Finite element The force exerted on limb j , , These are the sign functions for the x, y, and z axes, respectively, and their values ​​depend on the finite element elements. The value of the contact surface normal of limb j is 1 when it is aligned with the contact surface normal, and 0 otherwise. 2) The point of application of the resultant force of the sofa finite element model on limb j is: In the formula, Let J be the point of application of the resultant force of the sofa finite element model on limb j. Let J be the coordinates of the centroid of limb j. , Let J represent the torques of the proximal and distal joints on limb j, respectively. The calculation formula is as follows: In the formula, , These represent the forces exerted on limb j by the proximal and distal joints, respectively. , These are the coordinates of the proximal and distal joints, respectively. , They are respectively and The included angle, and and The included angle.

5. A sofa ergonomics evaluation device based on musculoskeletal model flexibility simulation, characterized in that, The sofa ergonomics evaluation device based on musculoskeletal model flexibility simulation includes: The model building module is used to create a simplified human body model and set the size parameters of the simplified human body model; The limb force analysis module is used to place a simplified human body model on a sofa finite element model with the human body's actual sitting posture as the initial posture, and to calculate the posture, force, and force application point of each limb of the simplified human body model in a static state. In this process, a simplified human body model is placed on a sofa finite element model with the actual human sitting posture as the initial position, and the following operations are performed: Set the sofa finite element model as a finite element type soft body, and set the material deformation properties of the sofa finite element model according to the actual sofa material type; Set the simplified human body model to the rigid body Articulation type, and apply the real human sitting posture to the simplified human body model; Modify the joint angle constraints of the simplified human body model to limit the joint angle constraints between adjacent limbs to hinge joints that rotate with a single degree of freedom in the sagittal plane of the human body, and then place the simplified human body model on the sofa finite element model. The calculation of the posture, forces, and points of application of each limb in a simplified human body model at rest includes: Motion simulation is initiated. The simplified human body model, falling due to gravity, exerts pressure on the sofa finite element model, causing the sofa finite element model to deform. The elastic reaction force generated by the sofa finite element model's deformation acts on the simplified human body model. The joints of the simplified human body model move freely in the sagittal plane. This interaction continues until the joints cease movement and the sofa finite element model's deformation stops. A flexible simulator records the posture of each limb and the joint angles of each joint in the simplified human body model at this point. The system calculates and records the resultant force and point of application of the force applied to each limb of the simplified human body model after the sofa finite element model's deformation. It also records the reaction force and point of application of the force on the soles of the feet from the ground. A muscle force acquisition module is used to import the aforementioned dimensional parameters, the posture of each limb, the applied forces, and the point of application of the forces into the human musculoskeletal model, obtaining the required muscle force for each muscle in the entire body under stable posture conditions. The evaluation module is used to perform an ergonomic evaluation of the sofa design based on the muscle forces of the human musculoskeletal model and output the evaluation results.

6. The sofa ergonomics evaluation device based on musculoskeletal model flexibility simulation as described in claim 5, characterized in that, The model building module sets the size parameters of the simplified human body model and performs the following operations: Obtain actual human anatomical parameters and apply them to simplified human models; The weight and center of gravity of each limb of the simplified human model are calculated and set according to the actual human anatomical structure parameters.

7. The sofa ergonomic evaluation device based on musculoskeletal model flexible simulation as described in claim 5, characterized in that, The actual human sitting posture includes the posture of each limb and the joint angle of each joint when a person is sitting on a sofa.

8. The sofa ergonomic evaluation device based on musculoskeletal model flexible simulation as described in claim 5, characterized in that, The limb force analysis module calculates the posture, forces, and points of application of each limb in a static state of the simplified human body model, and performs the following operations: The posture of each limb in a simplified human body model at rest was calculated using a flexible simulator; Calculate the resultant force and the point of application of the resultant force on each limb of the simplified human body model after the sofa finite element model has deformed, including: For each finite element in the sofa finite element model, the normal stress in the xyz direction is solved based on the equilibrium equation. , , and tangential stress , , Query all finite element elements If it comes into contact with a specified limb j of a simplified human model, it is placed into the set. ; 1) The resultant force exerted by the sofa finite element model on limb j for: In the formula, Finite element The force exerted on limb j , , These are the sign functions for the x, y, and z axes, respectively, and their values ​​depend on the finite element elements. The value of the contact surface normal of limb j is 1 when it is aligned with the contact surface normal, and 0 otherwise. 2) The point of application of the resultant force of the sofa finite element model on limb j is: In the formula, Let J be the point of application of the resultant force of the sofa finite element model on limb j. Let J be the coordinates of the centroid of limb j. , Let J represent the torques of the proximal and distal joints on limb j, respectively. The calculation formula is as follows: In the formula, , These represent the forces exerted on limb j by the proximal and distal joints, respectively. , These are the coordinates of the proximal and distal joints, respectively. , They are respectively and The included angle, and and The included angle.

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