Magnetic hydrogel soft body leg and foot friction contact finite element method based on COMSOL

Abstract

The invention discloses a finite element method in a magnetic hydrogel soft leg and foot friction contact process based on COMSOL. The method belongs to a practical analysis method in the field of frictional contact dynamics. The method is different from a traditional robot leg and foot multi-rigid-body algorithm, a novel finite element method is adopted for calculating the dynamic response in the friction contact process of legs and feet (such as robot legs and feet) made of magnetic hydrogel soft materials, and the problem that analysis and calculation precision and efficiency are low is solved. The invention provides a finite element method for magnetic hydrogel soft body leg and foot friction contact based on COMSOL. The method comprises the steps that fine design is conducted on a model, and interference check is conducted after design is completed; using a partial differential stress equilibrium equation (PDE) of the magnetic hydrogel material under the condition of magnetic-solid coupling as a constitutive model of the magnetic hydrogel material; carrying out encryption processing on the grid division of the local contact area of the frictional contact, and setting a transition grid; and performing finite element analysis on the frictional contact part of the model by adopting contact algorithms such as a penalty function method. The analysis method has the characteristics of high calculation efficiency and high calculation precision, and can be widely applied to engineering.

Description

Technical Field

[0001] The present invention relates to the technical field of friction contact dynamics analysis methods, and more particularly to a finite element method for friction contact of magnetic hydrogel soft legs and feet based on COMSOL. Background Art

[0002] Soft robots, as innovative products in the field of flexible robot technology, demonstrate extraordinary potential in numerous fields due to the lightness, high elasticity, and remarkable morphological plasticity of their materials. Hydrogel, as the main material of soft robots, has good biocompatibility. If the polymer network of the hydrogel consists of non-toxic polymers, it has biocompatibility and can thus be safely used in biomedical applications.

[0003] Among the numerous driving methods for hydrogel soft robots, magnetic driving is a popular and promising approach at present. Magnetic-driven hydrogel soft robots can be precisely programmed and controlled through an external magnetic field. By adjusting the intensity and direction of the magnetic field, precise control over the robot's motion trajectory, speed, and posture can be achieved. Moreover, this technology allows for wireless operation of the robot, avoiding the limitations and inconveniences brought by traditional wired driving methods. This makes the robot more flexible and practical in complex environments or hard-to-reach areas.

[0004] For robots, friction contact during the operation of their leg and foot structures is inevitable. Although Coulomb's friction law, as a classic description of dry friction phenomena, provides a basic framework for understanding friction forces, in actual situations, more refined friction models need to be considered. At the same time, the microscopic topography of the contact interface, the inherent properties of the material, and the lubrication conditions, etc., all have a significant impact on the generation of friction forces. The comprehensive consideration of these factors is crucial for accurately predicting friction behavior.

[0005] Therefore, an efficient friction contact algorithm is needed to conduct in-depth research on magnetic hydrogel soft robots with different constitutive models, and it is quite necessary to develop such finite element methods. Summary of the Invention

[0006] The content of the present invention is to propose a finite element method for friction contact of magnetic hydrogel soft legs and feet based on COMSOL. By establishing a new constitutive model through the PDE method, stable control of magnetic soft legs and feet can be achieved. By reducing the number of grids in the non-contact part and adopting advanced friction contact theory to deepen the research on tribology, and encrypting the number of grids in the contact area, not only is the calculation speed of the analysis process significantly improved, but also the accuracy of the analysis results is ensured.

[0007] To achieve the above effects, the technical solution of the present invention is as follows:

[0008] Refine the design of the model and perform interference checks after the design is completed; use the partial differential stress balance equation (PDE) under the magneto-solid coupling condition of the magnetic hydrogel material as its constitutive model; encrypt the mesh division of the local contact area of the frictional contact and set transition meshes; use contact algorithms such as the penalty function method for the frictional contact part of the model for finite element analysis.

[0009] As a preferred embodiment of the present invention, the method includes the following steps:

[0010] Step Step1, add the magnetic-solid coupling physical field, add research, and add components;

[0011] Step Step2, derive the partial differential stress balance equation (PDE) as its constitutive model, and use the function of COMSOL to customize the weak form partial differential to insert the derived constitutive model;

[0012] Step Step3, establish a geometric model in the COMSOL software and perform checks such as model interference;

[0013] Step Step4, perform a union operation on the model, finally assemble to form a union, and establish contact pairs;

[0014] Step Step5, perform domain division to facilitate independent mesh setting for different domains;

[0015] Step Step6, define the properties and material parameters of the model one by one, and set the material parameters for the remaining parts of the overall leg and foot;

[0016] Step Step7, perform load addition, constraint setting, and contact friction setting;

[0017] Step Step8, perform model mesh division;

[0018] Step Step9, finally select an appropriate output time step in the research for transient dynamics solution.

[0019] As a preferred embodiment of the present invention, the interference check of the model includes between the leg and foot and between the leg and foot and the contact surface;

[0020] As a preferred embodiment of the present invention, for the mesh encryption processing in the contact area of the finite element method, that is, use free tetrahedral meshes or hexahedral meshes, etc., fine-tune operations such as the minimum mesh size to make the mesh encrypted, and perform model mesh convergence analysis;

[0021] As a preferred embodiment of the present invention, the soft material is set as a soft material such as a hyperelastic body;

[0022] As a preferred solution of the present invention, in order to ensure the accuracy of the simulation, the software model adopts the material parameters in the actual engineering, and the same applies to the geometric parameters;

[0023] The finite element method of frictional contact of magnetic hydrogel soft body legs and feet based on COMSOL of the present invention performs fine design on the model and performs interference check after the design is completed; the partial differential stress equilibrium equation (PDE) of magnetic hydrogel material under the condition of magneto-solid coupling is used as its constitutive model; the mesh division of the contact area is encrypted and a transitional mesh is set; the frictional contact part of the model is analyzed by using efficient contact algorithms such as penalty function method, etc., and finite element analysis is performed. This method provides a new approach that is both efficient and accurate for solving the frictional contact problem of magnetic hydrogel soft body legs and feet. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a flow chart of the finite element method of frictional contact of magnetic hydrogel soft body legs and feet based on COMSOL provided in the preferred embodiment of the present invention; Figure 2 and Figure 3 It is a finite element model provided by the robot soft leg and foot structure provided by the preferred embodiment of the present invention. DETAILED DESCRIPTION

[0025] The specific implementation of the present invention is explained in detail below with reference to the accompanying drawings and embodiments.

[0026] Preferred Embodiments

[0027] This preferred embodiment discloses a finite element method for frictional contact of magnetic hydrogel soft body legs and feet based on COMSOL. Figure 2 As shown, the module of the robot soft leg and foot model includes a fixed block 1, a fixed hinge bolt 2, an upper rod leg and foot 3, a movable hinge bolt 4, a lower connecting rod leg and foot 5, and a slidable plate 6. The fixed block 1 is fixed on a certain rigid plane, the fixed hinge bolt 2 is fixed to the fixed block 1, one end of the upper connecting rod leg and foot 3 is connected to the fixed hinge bolt 2, and the other end is connected to one end of the lower connecting rod leg and foot 5 through the movable hinge bolt 4. The two ends can also rotate under the influence of friction contact, and the other end of the lower connecting rod leg and foot 5 is in friction contact with the sliding plate 6.

[0028] like Figure 1 As shown, the specific process includes the following steps:

[0029] Step 1, add magnetic-solid coupling physics, add research, add components;

[0030] Step 2, derive the partial differential stress equilibrium equation (PDE) as its constitutive model, and use the COMSOL custom weak form partial differential function to insert the derived constitutive model;

[0031] Step 3: Establish a geometric model in COMSOL software and perform checks such as model interference;

[0032] Step 4: Perform a union operation on the model, finally assemble to form a combined body, and establish contact pairs;

[0033] Step 5: Perform domain division to facilitate independent mesh setting for different domains;

[0034] Step 6: Define the properties and material parameters of the model one by one, and set the material parameters for the remaining parts of the overall leg;

[0035] Step 7: Apply loads, set constraints, and set contact friction;

[0036] Step 8: Perform mesh division of the model;

[0037] Step 9: Finally, select an appropriate output time step in the study to perform transient dynamics solution.

[0038] To ensure the accurate implementation of the above process, this embodiment uses hard magnetic particle hydrogel soft matter as the experimental material, combines experiments and numerical theoretical derivations, uses the balance equation in the weak contribution form for multi-physics field coupling, deals with nonlinear effects, finally obtains the above constitutive model, and substitutes it into COMSOL for numerical simulation calculation.

[0039] The above embodiments given in conjunction with the drawings are only the preferred solutions for implementing the present invention rather than limiting it. Any modification to the specific implementation manner of the present invention or mechanical equivalent replacement of some technical features, without departing from the spirit of the technical solution of the present invention, should be covered within the scope of the technical solution claimed by the present invention. The protection scope of the present invention also includes any alternative technical solutions that those skilled in the art can think of without creative efforts.

Claims

1. A finite element method for frictional contact of magnetic hydrogel soft body legs and feet based on COMSOL, characterized in that: The model is designed in a refined manner and an interference check is performed after the design is completed. The partial differential stress equilibrium equation (PDE) of magnetic hydrogel material under magneto-solid coupling is used as its constitutive model. The mesh division of the local contact area of ​​friction contact is encrypted and a transition mesh is set. Finite element analysis is performed on the friction contact part of the model using contact algorithms such as the penalty function method.

2. According to claim 1, a finite element method for friction contact between magnetic hydrogel soft body legs and feet based on COMSOL is characterized in that: The interference check of the model includes the interference between legs and feet, and between legs and feet and contact surfaces.

3. The simulation calculation process in the finite element method of soft leg-foot friction contact based on COMSOL according to claim 1 is characterized in that: The method comprises the following steps: Step 1, add magnetic-solid coupling physics, add research, add components; Step 2, derive the partial differential stress equilibrium equation (PDE) as its constitutive model, and use the COMSOL custom weak form partial differential function to insert the derived constitutive model; Step 3, establish a geometric model in COMSOL software, and perform model interference and other checks; Step 4, perform union processing on the models, finally assemble them into a union, and establish contact pairs; Step 5, divide the domain so that grids can be set independently in different domains; Step 6, define the properties and material parameters of the model one by one, and set the material parameters of the rest of the leg and foot; Step 7, add load, set constraints and contact friction; Step 8, model mesh division; Step 9, finally, select the appropriate output time step to perform transient dynamics solution in the study.

4. The contact area mesh encryption process in the finite element method according to claim 1, i.e., using a free tetrahedral mesh or a hexahedral mesh, etc., fine-tuning the minimum mesh size and other operations to encrypt the mesh, and performing a model mesh convergence analysis.

5. According to the finite element method of claim 3, the soft material is set to be a superelastic material.

6. According to the finite element method described in claim 3, in order to ensure the accuracy of simulation, the software model adopts material parameters in actual engineering, and the same applies to geometric parameters.

7. According to the finite element method of claim 3, after the constitutive model is derived, it needs to be transformed into a weak form partial differential equation in the form of a Galerkin variational equation, so as to describe the problem of movement and deformation of the magnetic hydrogel material under the stimulation of a magnetic field.

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