A method for reliability prediction of a device comprising a link motion mechanism

Abstract

The application discloses a kind of for containing connecting rod motion mechanism Equipment reliability prediction method, belong to equipment quality control technical field.The existing technology is not considered when the equipment reliability research is about, component aging leads to equipment performance decline, cannot effectively predict the problem of the reliability of equipment containing connecting rod motion mechanism.It includes the analysis of the motion principle of the connecting rod motion mechanism of equipment, the functional failure analysis of the connecting rod motion mechanism of equipment and the establishment of multi-body dynamics model, the dynamic representation of the wear and clearance size of the pair, the establishment of functional failure model, reliability analysis and calculation and other steps.This method not only considers the dynamics characteristics of connecting rod motion mechanism, but also considers the wear damage law of the pair, can effectively predict the service life of the equipment containing connecting rod motion mechanism, and can guide the maintenance and detection of the equipment containing connecting rod motion mechanism in the use process.

Description

Technical Field

[0001] This invention belongs to the field of equipment quality control technology, specifically relating to a method for predicting the reliability of equipment containing linkage mechanisms. Background Technology

[0002] In medical device manufacturing, equipment incorporating linkage mechanisms is widely used, such as robotic arms, wearable exoskeletons, and operating tables. Linkage mechanisms, through mechanical connections, achieve precise motion control, force transmission, and structural support, thereby fulfilling the equipment's functions. However, due to unavoidable wear, corrosion, and aging during actual use, the kinematic pairs of these linkage mechanisms typically experience wear and degradation. Furthermore, the application of such equipment rarely involves detailed maintenance of these kinematic pairs, further exacerbating the wear and deteriorating the linkage mechanism's motion function, even affecting the equipment's overall performance. Therefore, accurately identifying the parameters characterizing the motion function of linkage mechanisms, establishing a functional relationship between kinematic pair wear and these parameters, and seeking a method to accurately predict the evolution of equipment reliability are crucial for the refined design and long-term use of equipment containing linkage mechanisms.

[0003] Existing equipment reliability studies largely focus on incoming quality inspection, usage management systems, or macroscopic failure statistics, generally assuming that the mechanical system's performance is stable throughout its lifespan, neglecting the gradual functional degradation process caused by microscopic wear. Although some patents involve wear detection or lifespan prediction, their methods are mainly based on static threshold judgments or empirical curve fitting, failing to establish a dynamic mapping relationship between the wear evolution of kinematic pairs and the overall machine's functional output. Especially for complex mechanisms with multiple links and kinematic pairs, where the force transmission path is long and error coupling is strong, traditional methods struggle to quantify the impact of clearance changes on end-effector accuracy, let alone achieve dynamic evolution prediction of reliability over usage time or cycle count.

[0004] Based on this, the present invention proposes a reliability prediction method for equipment containing linkage motion mechanisms to solve the problems existing in the prior art. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for predicting the reliability of equipment containing linkage mechanisms. This method solves the problem that existing technologies, when studying equipment reliability, do not consider the performance degradation caused by component aging, and therefore cannot effectively predict the reliability of equipment containing linkage mechanisms.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for predicting the reliability of equipment containing a linkage mechanism includes: Step 1: Analyze the motion principle of the linkage mechanism of the equipment; Step 2: Perform functional failure analysis on the linkage mechanism of the equipment and establish a multibody dynamics model; Step 3: Dynamic characterization of wear and clearance dimensions of moving parts; Based on the Arcard wear model, a functional relationship between the wear depth of the kinematic pair and the contact stress and relative slip distance is established, and the wear depth is compensated in real time to the kinematic pair clearance parameters in the multibody dynamics model in step two, so as to realize the dynamic update of the clearance size. Step 4: Based on the functional characterization quantities and their thresholds from Step 3, establish a functional failure model; Step 5: Reliability Analysis and Calculation; Based on the analysis in steps three and four, and combined with the equipment's working requirements for the linkage mechanism, the Monte Carlo method was used to conduct reliability analysis, and the equipment reliability evolution curve and failure rate evolution curve were obtained.

[0007] In a preferred embodiment of the present invention, step 1, which analyzes the motion principle of the linkage mechanism, includes: analyzing the motion principle of the linkage mechanism based on mechanical theory and operating conditions, and clarifying the geometric and positional relationships of the power source, actuating parts, connecting parts, and force transmission parts of the linkage mechanism.

[0008] In a preferred embodiment of the present invention, step 2, which involves performing functional failure analysis on the linkage mechanism of the equipment, includes: using dynamic simulation software to construct a multibody dynamics model of the linkage mechanism of the equipment, and extracting functional failure characterization quantities based on the multibody dynamics model.

[0009] In a preferred embodiment of the present invention, the process of constructing the multibody dynamics model includes: Step 2.1: Model Import; Import the geometric data of the linkage mechanism into the multibody dynamics simulation environment; Step 2.2: Establishment of kinematic pairs; Topological modeling of fixed joints, revolute joints, and translational joints of linkage mechanisms is performed using virtual constraint components in the simulation environment; Step 2.3: Model the clearance of the rotating joint; The initial clearance of the rotating pair is corrected and modeled based on the wear depth calculated by the Archard wear model; Step 2.4: Apply load; Based on the actual working conditions of the equipment, an equivalent distributed load is applied to the actuator of the multibody dynamics model to simulate the external force interference in actual operation. Step 2.5: Setting up motor function representation parameters.

[0010] In a preferred embodiment of the present invention, when setting the motion function characterization parameters, the angle deviation Δθ = θ0 is used. - θ1 represents the angle between the axis of the actuating part and the ideal position. If the deviation Δθ exceeds the allowable range, the mechanism will fail. Where θ1 is the angle between the axis of the actuator and the horizontal line after wear, and θ0 is the angle between the axis of the actuator and the horizontal line initially.

[0011] In a preferred embodiment of the present invention, step three, performing dynamic characterization of wear on the moving pair, includes: The wear of moving parts is modeled using the Archard wear model, and the calculation formula is expressed as follows: ; Where: Δ h Δ represents the wear depth. s The relative sliding distance. k The wear coefficient is dimensionless. H The hardness of a softer material, p Contact stress; Contact stress p The formula is obtained from calculations based on Hertzian contact theory: ; in: F For load per unit length, R 1 represents the initial radius of the bushing in the linkage mechanism. ，R 2 represents the initial radius of the journal of the linkage mechanism. E 1 represents the Young's modulus of the bushing material. E 2 represents the Young's modulus of the journal material. υ 1 represents the Poisson's ratio of the bushing material. υ 2 represents the Poisson's ratio of the journal material; If we only consider the relative rotation between the elements of the linkage kinematic pair, the relative sliding distance is: ; in: The relative rotation angle of the kinematic pair elements during a motion cycle. r The radius of motion of the kinematic pair element in one motion cycle. n The number of cycles of the motion; The cumulative wear depth is expressed as: ; in: p ( t )and ω ( t ) are functions of contact stress and rotation angle over time, respectively. b This refers to the journal width.

[0012] In a preferred embodiment of the present invention, the dynamic characterization of the gap size in step three is as follows: ; in: C 0 is the initial value of the gap. h This represents the cumulative wear depth.

[0013] In a preferred embodiment of the present invention, step four, which establishes a functional failure model based on the functional characterization quantities and their thresholds from step three, includes: Take the angle between the axis of the moving part and the horizontal line. θ As a functional characteristic of the linkage mechanism, this functional characteristic is a function of each clearance and is expressed as: ; in: C i The serial number represents the rotating pair. i The gap, The length vector of each link; The probability of functional failure is: ; in: θ 0 For the ideal value of the functional characterization quantity, θ TH The failure threshold for functional characterization. P f This represents the probability of functional failure.

[0014] In a preferred embodiment of the present invention, step five, which uses the Monte Carlo method to perform reliability analysis and obtain the equipment reliability evolution curve and failure rate evolution curve, includes: Based on the parameter value table, the Latin hypercube method is used to perform initial sampling of each input parameter; Substitute the input data sample into the functional representation function and calculate the output value; Based on the failure probability calculation formula, the initial failure probability is calculated. Based on the wear formula, calculate the parameter characteristics at the next statistical time point, and repeat the above steps based on the new parameter characteristics to obtain the failure probability at the corresponding time point; The results were compiled and the corresponding failure probability values ​​at different statistical moments were recorded to obtain the equipment reliability evolution curve and failure rate evolution curve.

[0015] Compared with the prior art, the present invention provides a method for predicting the reliability of equipment containing linkage mechanisms, which has the following advantages: This method is the first to deeply integrate the Archard wear model with multibody dynamics simulation, dynamically updating the clearance parameters of kinematic pairs to realistically reflect the impact of wear accumulation on the motion accuracy of linkage mechanisms. Compared to existing technologies that rely solely on static thresholds or empirical life curves, this method can quantitatively describe the functional relationship between the wear state of each kinematic pair and the positional deviation of the actuator at any given moment of use. It achieves a precise mapping from "component damage" to "system failure," solving the reliability assessment challenge caused by the long force transmission path and strong error coupling of complex linkage mechanisms.

[0016] This method, by introducing Monte Carlo random simulation and Latin hypercube sampling, fully considers uncertainties such as manufacturing tolerances, material properties, and load fluctuations. The generated reliability and failure rate curves can realistically reflect the performance degradation trend of equipment throughout its entire life cycle. Experimental results show that, considering clearance wear, equipment reliability decreases significantly in the early stages of use, while the failure rate increases sharply. This finding provides a scientific basis for equipment maintenance strategy formulation and life management, overcoming the limitations of traditional methods that assume constant mechanical system performance.

[0017] This method focuses on functional failure characterization metrics, is independent of specific equipment structures, and can be adapted to various devices with linkage mechanisms, such as medical beds and robotic arms, simply by adjusting the load model and geometric parameters. Verification through physical wear tests shows a high degree of agreement between the model's calculated values ​​and measured data, proving its engineering feasibility. This method can be directly integrated into the product design phase to guide the selection of materials, lubrication, and tolerance allocation for key kinematic pairs. It can also be used for health monitoring and remaining service life prediction during service, significantly improving the reliability and safety of high-end equipment. Attached Figure Description

[0018] Figure 1 This is a flowchart of the equipment reliability prediction method of the present invention.

[0019] Figure 2 This is a structural and working principle diagram of the medical bed linkage device of the present invention.

[0020] Figure 3 This is a simplified diagram illustrating the failure of the medical bed linkage device of the present invention.

[0021] Figure 4 This is an import interface diagram of the medical bed model of the present invention.

[0022] Figure 5 This is a diagram showing the property settings of the kinematic pairs of the medical bed of the present invention.

[0023] Figure 6 This is a load setting diagram for the medical bed of the present invention.

[0024] Figure 7This is a schematic diagram showing the wear depth of the key moving parts of the medical bed of the present invention.

[0025] Figure 8 This is a diagram illustrating the physical test platform for wear and tear of the medical bed according to the present invention.

[0026] Figure 9 This is a schematic diagram comparing the calculated wear depth data of the medical bed of the present invention with the actual test measurement data.

[0027] Figure 10 This is a schematic diagram showing the reliability variation curves of the linkage device under different working cycles of the medical bed of the present invention.

[0028] Figure 11 This is a schematic diagram showing the change in failure rate of the linkage device under different working cycles of the medical bed of the present invention.

[0029] Figure 12 This is a schematic diagram of the structure of the robotic arm of the present invention.

[0030] Figure 13 This is a schematic diagram of the structure and working principle of the robotic arm of this invention.

[0031] Figure 14 This is a simplified diagram illustrating the failure of the loading robotic arm in this invention.

[0032] Figure 15 This is the reliability evolution curve of the loading robotic arm of this invention.

[0033] Figure 16 The failure probability evolution curve of the loading robotic arm in this invention is shown.

[0034] Among them: Figure 2 In the linkage mechanism, ① is the actuator, used to complete the function of the linkage mechanism, such as the lifting and rotation of the bed board in a medical device; ② is the power source component (hydraulic actuator) of the linkage mechanism, used to provide power; ③, ④, ⑤, and ⑥ are all motion link components of the linkage mechanism, used to connect the power source and the actuator, and transmit the motion trajectory and force. The components of the linkage mechanism are connected through kinematic pairs.

[0035] exist Figure 3 middle, Figure 3 (a) is the initial state, with all components in their original positions; Figure 3 (b) for in Figure 3 Based on (a), the extension of the hydraulic actuator cylinder drives the moving rod and the actuator to the target position.

[0036] exist Figure 5 middle, Figure 5 (a) Graph showing the settings for rotational sub-attributes; Figure 5 (b) is a diagram showing the settings for translation sub-attributes.

[0037] exist Figure 7 middle, Figure 7 (a) is a schematic diagram of the initial clearance and target rotation angle; Figure 7 (b) is a schematic diagram of the gap and target rotation angle after wear.

[0038] exist Figure 9 middle, Figure 9 (a) is a comparison curve of the first clearance wear result; Figure 9 (b) is a comparison curve of the second clearance wear result; Figure 9 (c) is a comparison curve of the third gap wear result; Figure 9 (d) is a comparison curve of the fourth gap wear result; Figure 9 (e) is a comparison curve of the wear results of the 5th gap.

[0039] exist Figure 13 In the diagram, l1~l5 are 5 links, and ①~⑥ are 6 gaps. Driven by the power source, the links move the cargo from the initial position to the target position.

[0040] exist Figure 14 middle, Figure 14 (a) is a diagram of the robot arm bending at the target position; Figure 14 (b) Bending diagram of the robotic arm in its initial position. Detailed Implementation

[0041] 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.

[0042] As per the instruction manual Figure 1 - Appendix Figure 16 As shown, this invention proposes a reliability prediction method for equipment containing a linkage mechanism. In practical applications, long-term use will cause wear on the kinematic pairs of the linkage mechanism, affecting the actuation effect of the linkage mechanism, which may lead to the execution component failing to move to the designed position, resulting in functional failure of the motion mechanism, or even making the equipment unusable.

[0043] As per the instruction manual Figure 1 - Appendix Figure 11 As shown, to solve the above problems, this embodiment takes a certain model of medical bed containing a linkage mechanism as an example, according to the attached... Figure 1The process shown analyzes and establishes a reliability prediction model. This method can not only predict the reliability of equipment containing linkage mechanisms, but also be extended to other products with similar characteristics. The detailed steps of this method are as follows: Step 1: Analyze the motion principle of the linkage mechanism of the equipment; Based on mechanical theory and medical operating conditions, the motion principle of the linkage mechanism is analyzed to clarify the geometric and positional relationships of the power source, actuating parts, connecting pairs, and force transmission parts of the equipment linkage mechanism.

[0044] The medical bed in this embodiment uses a power hydraulic assembly (attached) Figure 2 The actuator of component ②) extends, driving the connecting rod assembly (attached) Figure 2 Components ③④⑤⑥) move, ultimately driving the actuator (attached) Figure 2 Component ①) moves to the predetermined position, as shown in the attached diagram. Figure 3 As shown, this enables the device to perform its functions. For devices such as medical beds that include linkage mechanisms, accurately and stably moving the actuators to their designated positions is a powerful guarantee for ensuring the conduct of treatment activities and ensuring good patient care and recovery.

[0045] Step 2: Perform functional failure analysis on the linkage mechanism of the equipment and establish a multibody dynamics model; Using dynamic simulation software, a multibody dynamic model is constructed, covering load application, model parameterization, constraint establishment, kinematic pair modeling, and input / output parameter extraction. Based on the multibody dynamic model, functional failure characterization quantities are extracted.

[0046] The construction process of the multibody dynamics model includes: Step 2.1: Model Import; Import the geometric data of the linkage mechanism into the multibody dynamics simulation environment; Specifically, import typical data formats (.stp, .CAT, etc.) into the LMS Virtual LAB multibody dynamics simulation platform. The interface after import is shown in the attached image. Figure 4 As shown, the interface includes a model display area, a function menu bar, a structure analysis tree, a file editing bar, a toolbar, etc., and the relevant functions of modeling can be realized by selecting the corresponding tools.

[0047] Step 2.2: Establishment of kinematic pairs; Topological modeling of fixed joints, revolute joints, and translational joints of linkage mechanisms is performed using virtual constraint components in the simulation environment; Specifically, kinematic pairs are crucial for constraining the motion relationships of various components and realizing the designed motion functions. Based on mechanical design principles and mechanism kinematics theory, the LMS Virtual LAB multibody dynamics simulation platform is used to model kinematic pairs using functional modules such as virtual fixed pairs, virtual revolute pairs, and virtual translational pairs. (Appendix) Figure 5 (a) and (b) are the attribute settings diagrams for revolute joints and translational joints, respectively.

[0048] Step 2.3: Model the clearance of the rotating joint; The initial clearance of the rotating pair is corrected and modeled based on the wear depth calculated by the Archard wear model; Specifically: Appendix Figure 3 C1, C2, C3, C4, and C5 shown are the clearances corresponding to the rotating joints. The software platform supports directly assigning values ​​to the clearances, and the specific values ​​are obtained based on the Archard wear model (see step three for details).

[0049] It should be noted that the Archard wear model is the most classic and widely used quantitative prediction model for adhesive sliding wear in the field of mechanical engineering. It was proposed by JF Archard in 1953. Its core principle is that the wear volume is directly proportional to the normal load and the sliding distance, and inversely proportional to the material hardness. It is an existing technology known to those skilled in the art.

[0050] Step 2.4: Apply load; Based on the actual working conditions of the equipment, an equivalent distributed load is applied to the actuator of the multibody dynamics model to simulate the external force interference in actual operation. Specifically, it simulates real-world loads by distributing forces, with the load application locations shown in the attached figure. Figure 6 As shown, the load is applied using the three-point force distribution method of the simulation software platform. The load application location, load name, and load size need to be defined.

[0051] It should be noted that the equivalent distributed load is determined according to the equipment type: for medical beds, the patient's weight is equivalent to a vertically downward concentrated force acting on the center of gravity of the bed board, or simplified as a three-point support force according to the human body distribution; for loading robotic arms, the inertial force generated by the weight of the cargo and the maximum acceleration is combined and equivalent to a concentrated force acting on the end effector. The specific values ​​are determined based on the rated load and safety factor of the equipment, and are applied to the corresponding nodes in the simulation software through the 'Force' module.

[0052] Step 2.5: Setting up motor function representation parameters; Due to manufacturing errors, randomness in material parameters, and other reasons, the clearance values ​​between the kinematic pairs formed by the various links are not constant, but rather follow a random variable that conforms to a certain distribution. Due to unavoidable friction and wear, the clearance values ​​of each kinematic pair will evolve with use, further preventing the moving parts from moving to their designed positions.

[0053] As attached Figure 7 As shown, attached Figure 7 (a) The state without considering clearance wear, the clearances of each moving pair are as follows: Figure 7 (a) As shown in ①, the angle between the axis of the actuating part and the horizontal line is θ0, indicating that the actuating part can move to the predetermined position according to the design goal. After the motion mechanism has been used for a period of time, the kinematic pairs wear, which leads to an increase in the clearance between the kinematic pairs (as shown in the attached diagram). Figure 7 (b) As shown in ②), the angle between the axis of the moving part and the horizontal line is θ1, which deviates from the ideal position angle by Δθ=θ0. - If the deviation Δθ exceeds the allowable range, the mechanism will fail.

[0054] Step 3: Dynamic characterization of wear and clearance dimensions of moving parts; Based on the Arcard wear model, a functional relationship is established between the wear depth h of the kinematic pair and the contact stress p and the relative slip distance s. The wear depth h is then compensated in real time to the kinematic pair clearance parameter C in the multibody dynamics model described in step two, thereby realizing the dynamic updating of the clearance size.

[0055] The wear of moving parts is modeled using the Archard wear model, and the calculation formula is expressed as follows: ; Where: Δ h For wear depth, Δ is the wear depth when uniform wear is considered. h Equivalent to gap C The change in Δ s The relative sliding distance. k The wear coefficient is dimensionless. H The hardness of a softer material, p For contact stress, E Let be the Young's modulus of the material.

[0056] Contact stress can be calculated using Hertzian contact theory, with the following formula: ; in: F For load per unit length, R 1 represents the initial radius of the bushing in the linkage mechanism. ，R 2 represents the initial radius of the journal of the linkage mechanism. E1 represents the Young's modulus of the bushing material. E 2 represents the Young's modulus of the journal material. υ Poisson's ratio for materials with kinematic pair elements. υ 1 represents the Poisson's ratio of the bushing material. υ 2 represents the Poisson's ratio of the journal material.

[0057] If we only consider the relative rotation between the elements of the linkage kinematic pair, its relative slip distance is expressed as: ; in: The relative rotation angle of the kinematic pair elements during a motion cycle. r The radius of motion of the kinematic pair element in one motion cycle. n This represents the number of cycles of the motion.

[0058] The cumulative wear depth is expressed as: ; in: p ( t )and ω ( t ) are functions of contact stress and rotation angle over time, respectively, and b is the journal width, which can be obtained from the mechanism dynamics model constructed in step two.

[0059] To verify the accuracy of the wear depth values ​​calculated by the above method, this embodiment designs a physical test bench as shown in the attached figure. Figure 8 As shown, the physical test bench includes a drive motor, coupling assembly, speed sensor, and wear bushing. By applying a certain speed and load to the rotating shaft, the wear depth is measured after a certain period of time. A comparison is made between the wear depth calculated using this method and the wear depth measured through physical testing (to verify the wear patterns of the hinge pin and bushing under different loads, and to conduct subsequent research based on this). See attached figure. Figure 9 As shown, from the appendix Figure 9 As can be seen, the calculation and experimental errors are small, which effectively proves the applicability of this method.

[0060] The equivalent length of a link involved in the motion transmission of a mechanism is equal to the actual length of the link plus (minus) the clearance length, expressed as: l’ ± C = l ±( R 1- R 2) The actual geometric length of the connecting rod, the l 'The effective length of the link involved in motion transmission' C The size of the gap is a quantity that varies with generalized time (time, number of uses, number of cycles, etc.), and can also be expressed as... C ( tThe method for calculating the gap size is as follows: ; in: C 0 This is the initial value of the gap. h The cumulative wear depth is obtained from the above calculation.

[0061] Step 4: Based on the functional characterization quantities and their thresholds from Step 3, establish a functional failure model; The angle θ between the axis of the actuating component and the horizontal line is selected as the kinematic failure characteristic of the linkage mechanism. This functional characteristic is a function of each clearance and is expressed as: ; in: C i Indicates that the serial number is a revolute pair. i ( i The gaps are 1, 2, 3, 4, 5. Let be the length vector of each link.

[0062] If the functional characteristic (the angle θ between the axis of the actuating part and the horizontal line) deviates too far from the ideal value, functional failure will occur. Therefore, the failure probability of functional failure is expressed as: ; in: θ 0 This represents the ideal value of the functional characterization quantity. θ TH The failure threshold representing the functional characteristic quantity. P f This indicates the probability of functional failure.

[0063] Step 5: Reliability Analysis and Calculation; Based on the analysis in steps three and four, and combined with the equipment's working requirements for the linkage mechanism, the Monte Carlo method was used to conduct reliability analysis, and the equipment reliability evolution curve and failure rate evolution curve were obtained.

[0064] In this embodiment, the implementation process of the Monte Carlo method includes: (1) Based on Table 1: Parameter Value Table, the Latin hypercube method is used to perform initial sampling of each input parameter, with a sampling size of 10. 6 That is, to obtain 10 6 Group input data samples; (2) Substitute the input data sample into the functional representation function to calculate and obtain 10 6 The output value is the angle between the axis of the moving part and the horizontal line. θ ; (3) Calculate the initial failure probability according to the failure probability calculation formula; (4) Calculate the parameter characteristics at the next statistical moment based on the wear formula, and repeat steps (1), (2) and (3) above based on the new parameter characteristics to obtain the failure probability at the corresponding moment; (5) Results compilation: Record the failure probability values ​​corresponding to different statistical times, and obtain the equipment reliability evolution curve and failure rate evolution curve.

[0065] This embodiment utilizes the analysis model and calculation formula obtained in steps one through five above, substitutes relevant parameters, and obtains the reliability analysis results of the device containing the linkage mechanism, as shown in the appendix. Figure 10 and attached Figure 11 As shown. Among them, the appendix Figure 10 The reliability evolution curve of this equipment is attached. Figure 11 Its failure rate evolution curve. From the appendix Figure 10 and attached Figure 11 As can be seen from the curves, considering clearance wear, the reliability of the equipment decreases rapidly after a period of use, and the failure rate increases dramatically, proving that equipment containing linkage mechanisms requires attention to the issue of reduced reliability. The parameter values ​​involved in the above calculations are shown in Tables 1 and 2.

[0066] Table 1: Calculation Parameter Values ​​Table

[0067] Table 2: Data from the Bushing Wear Test

[0068] As per the instruction manual Figure 12 - Appendix Figure 16 As shown in the figure, the reliability prediction method for equipment containing linkage mechanisms described in this embodiment is applied to a certain type of loading robot arm as follows: The structural composition diagram of a certain type of loading robotic arm is attached. Figure 12 As shown, it includes a power source, base, linkage mechanism, and loading cargo, etc. Its motion transmission is accomplished by a set of linkage mechanisms. The sectional diagram of the linkage mechanism is attached. Figure 13 As shown, l1~l5 are 5 links, and ①~⑥ are 6 gaps. Driven by the power source, the links move the cargo from the initial position to the target position (as shown in the attached diagram). Figure 14 As shown in the figure, it moves back and forth between the initial position and the target position to complete the repetitive cargo handling work.

[0069] Similarly, due to the initial clearance between each linkage kinematic pair, wear may cause the clearance to increase, resulting in a deviation between the actual achievable target position and the ideal target position required by the design.

[0070] The reliability analysis of the loading robot arm can be performed using the analysis steps of the reliability prediction method for equipment containing a linkage mechanism described in this invention. The values ​​of the relevant parameters are shown in Table 3. Substituting the relevant parameters into the formula yields the reliability and failure probability evolution curves of the loading robot arm, as shown in the attached figure. Figure 15 and attached Figure 16 As shown. (Through the attached...) Figure 15 and attached Figure 16 As can be seen from the curve, the reliability prediction method for equipment containing linkage mechanisms described in this invention can effectively predict the reliability of equipment containing linkage mechanisms.

[0071] Table 3: Calculation Parameter Values ​​Table

[0072] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for predicting the reliability of equipment containing a linkage mechanism, characterized in that, include: Step 1: Analyze the motion principle of the linkage mechanism of the equipment; Step 2: Perform functional failure analysis on the linkage mechanism of the equipment and establish a multibody dynamics model; Step 3: Dynamic characterization of wear and clearance dimensions of moving parts; Based on the Archard model, a functional relationship between the wear depth of the kinematic pair and the contact stress and relative slip distance is established, and the wear depth is compensated in real time to the kinematic pair clearance parameters in the multibody dynamics model in step two, so as to realize the dynamic update of the clearance size. Step 4: Based on the functional characterization quantities and their thresholds from Step 3, establish a functional failure model; Step 5: Reliability Analysis and Calculation; Step 2, the process of performing functional failure analysis on the linkage mechanism of the equipment, includes: using dynamic simulation software to construct a multibody dynamics model of the linkage mechanism, and extracting functional failure characterization quantities based on the multibody dynamics model; the construction process of the multibody dynamics model includes: Step 2.1: Model Import; Import the geometric data of the linkage mechanism into the multibody dynamics simulation environment; Step 2.2: Establishment of kinematic pairs; Topological modeling of fixed joints, revolute joints, and translational joints of linkage mechanisms is performed using virtual constraint components in the simulation environment; Step 2.3: Model the clearance of the rotating joint; The initial clearance of the rotating pair is corrected and modeled based on the wear depth calculated by the Archard wear model; Step 2.4: Apply load; Based on the actual working conditions of the equipment, an equivalent distributed load is applied to the actuator of the multibody dynamics model to simulate the external force interference in actual operation. Step 2.5: Setting up motor function representation parameters; When setting the parameters representing motor function, use the angle deviation Δθ=θ0. - θ1 represents the angle between the axis of the actuating part and the ideal position. If the deviation Δθ exceeds the allowable range, the mechanism will fail. Where θ1 is the angle between the axis of the moving part after wear and the horizontal line, and θ0 is the angle between the axis of the moving part and the horizontal line at the beginning; In step two, during the functional failure analysis of the linkage mechanism of the equipment and the establishment of a multibody dynamics model, the equivalent distributed load is determined according to the equipment type: for medical beds, the patient's weight is equivalent to a vertically downward concentrated force acting on the center of gravity of the bed board, or simplified to a three-point support force according to the human body distribution; for loading robotic arms, the inertial force generated by the weight of the cargo and the maximum acceleration is combined and equivalent to a concentrated force acting on the end effector. Based on the analysis in steps three and four, and combined with the equipment's working requirements for the linkage mechanism, the Monte Carlo method was used to conduct reliability analysis and obtain the equipment reliability evolution curve and failure rate evolution curve. In step two, during the functional failure analysis of the linkage mechanism of the equipment and the establishment of a multibody dynamics model, the equivalent distributed load is determined according to the equipment type: for medical beds, the patient's weight is equivalent to a vertically downward concentrated force acting on the center of gravity of the bed board, or simplified to a three-point support force according to the human body distribution; for loading robotic arms, the inertial force generated by the weight of the cargo and the maximum acceleration is combined and equivalent to a concentrated force acting on the end effector. Step three involves performing dynamic characterization of wear on the kinematic pairs, which includes: The wear of moving parts is modeled using the Archard wear model, and the calculation formula is expressed as follows: ； Where: Δ h Δ represents the wear depth. s The relative sliding distance. k The wear coefficient is dimensionless. H The hardness of a softer material, p Contact stress; Contact stress p The formula is obtained from calculations based on Hertzian contact theory: ； in: F For load per unit length, R 1 represents the initial radius of the bushing in the linkage mechanism. ，R 2 represents the initial radius of the journal of the linkage mechanism. E 1 represents the Young's modulus of the bushing material. E 2 represents the Young's modulus of the journal material. υ 1 represents the Poisson's ratio of the bushing material. υ 2 represents the Poisson's ratio of the journal material; If we only consider the relative rotation between the elements of the linkage kinematic pair, the relative sliding distance is: ； in: The relative rotation angle of the kinematic pair elements during a motion cycle. r The radius of motion of the kinematic pair element in one motion cycle. n The number of cycles of the motion; The cumulative wear depth is expressed as: ； in: p ( t )and ω ( t ) are functions of contact stress and rotation angle over time, respectively. b This refers to the journal width; Step three, the dynamic characterization of the gap size, is as follows: ； in: C 0 is the initial value of the gap. h This represents the cumulative wear depth. Step four, based on the functional representation quantities and their thresholds from step three, involves establishing a functional failure model, which includes: Take the angle between the axis of the moving part and the horizontal line. θ As a functional characteristic of the linkage mechanism, this functional characteristic is a function of each clearance and is expressed as: ； in: C i The serial number represents the rotating pair. i The gap, The length vector of each link; The probability of functional failure is: ； in: θ 0 For the ideal value of the functional characterization quantity, θ TH The failure threshold for functional characterization. P f This represents the probability of functional failure. Step five involves using the Monte Carlo method to perform reliability analysis and obtain the equipment reliability evolution curve and failure rate evolution curve. Based on the parameter value table, the Latin hypercube method is used to perform initial sampling of each input parameter; Substitute the input data sample into the functional representation function and calculate the output value; Based on the failure probability calculation formula, the initial failure probability is calculated. Based on the wear formula, calculate the parameter characteristics at the next statistical time point, and repeat the above steps based on the new parameter characteristics to obtain the failure probability at the corresponding time point; The results were compiled and the corresponding failure probability values ​​at different statistical moments were recorded to obtain the equipment reliability evolution curve and failure rate evolution curve.

2. The reliability prediction method for equipment including a linkage mechanism as described in claim 1, characterized in that, Step 1, the process of analyzing the motion principle of the linkage mechanism of the equipment, includes: analyzing the motion principle of the linkage mechanism based on mechanical theory and operating conditions, and clarifying the geometric and positional relationships of the power source, actuating parts, connecting pairs, and force transmission parts of the linkage mechanism of the equipment.

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