Method for testing the number of bending cycles and dimensional stability of a tendon

Abstract

The present application relates to the transmission control technical field of robot dexterous hand, including: step S1: clamping sample and initial positioning.Control test machine to return to zero to initial position, the head end of the sample to be tested is fixed and the initial position a is marked, the sample bypasses two pulley groups, and the intersection occurs when winding around one group of pulleys; the weight is loaded at the tail end of the sample, the corresponding reading L0 of the tail end b on the scale in the initial state is marked and recorded; step S2: setting the loading frequency of the motor, setting the target loading times; step S3: executing reciprocating fatigue test; step S4: if the sample does not reach the target loading times and fracture occurs, the fatigue number when the fracture occurs is recorded; step S5: if the sample reaches the target loading times and does not fracture, the corresponding reading L1 of the tail end b on the scale after loading is completed is measured and recorded.The working condition proposed by the present application is strong in simulation reality, convenient in actual operation, and multiple in test indexes.

Description

Technical Field

[0001] This invention relates to the field of robot dexterous hand transmission control technology, and in particular to a method for simulating the reciprocating bending condition of tendon ropes around a pulley to test its bending fatigue number and dimensional stability. Background Technology

[0002] Existing chord fatigue testing methods mostly employ yarn-to-yarn friction fatigue testing, similar to ASTM D 6611-16, which tests the durability of yarns rubbing against each other at a specific angle. However, this method requires the sample to be wound three times (3*360°), which deviates significantly from the actual working conditions of chords. In actual operation, the chords of robotic dexterity hands not only experience wear but also endure fatigue loads from reciprocating bending around pulleys. Furthermore, existing yarn-to-yarn friction testing methods cannot effectively characterize the dimensional changes (such as creep and elongation) of chords during stress. The dimensional stability of chords is crucial for constructing accurate algorithm models and ensuring the precision of control systems. Therefore, there is an urgent need for a testing method that can accurately simulate actual working conditions and simultaneously monitor chord wear, bending fatigue life, and dimensional stability.

[0003] The present invention aims to overcome the shortcomings of the prior art in that it cannot accurately simulate the bending condition of tendon cords around pulleys and cannot characterize dimensional changes, and provides a test method for the bending fatigue number and dimensional stability of tendon cords, which can truly reflect the fatigue life and deformation characteristics of tendon cords in actual applications. Summary of the Invention

[0004] To achieve the above objectives, the present invention provides a method for testing the bending fatigue cycles and dimensional stability of tendon chords, comprising the following steps:

[0005] Step S1: Clamp the sample and position it initially. Control the testing machine to return to the zero position and fix the head end of the sample to be tested and mark the initial position a. The sample passes around two pulley sets and crosses when passing around one of the pulley sets. Load a weight at the tail end of the sample, mark and record the reading L0 of the tail end b on the scale in the initial state.

[0006] Step S2: Set the motor's loading frequency and the target number of loading cycles;

[0007] Step S3: Perform a reciprocating fatigue test;

[0008] Step S4: If the specimen fractures before reaching the target loading number, record the fatigue number at the time of fracture.

[0009] Step S5: If the sample does not fracture after reaching the target number of loading cycles, measure and record the reading L1 on the scale corresponding to the tail end b after loading is completed.

[0010] Furthermore, the pulley system described in step S1 shall have at least one set, and each set of pulleys shall consist of at least two pulleys.

[0011] Furthermore, in step S1, at least one set of samples crosses within the pulley group.

[0012] Furthermore, the cross-section of the samples can be achieved by rotating a pulley, and the rotation angle of the pulley must be greater than or equal to 180°; preferably between 180° and 360°.

[0013] Furthermore, the weight of the weight mentioned in step S1 is within the range that the testing equipment can bear, preferably between 0.1 kg and 10 kg.

[0014] Furthermore, the position change of end b mentioned in steps S1 and S5 can be measured by a ruler, or it can be achieved by image acquisition or laser ranging.

[0015] Furthermore, the recording of the number of fatigue cycles at the time of fracture in step S4 can be achieved by setting a trigger device below the weight, triggering the recording of the signal when the weight falls after the sample fractures, or by using image acquisition or other methods.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. Highly realistic simulation of working conditions: It adopts the motion mode of tendon rope contact wear and reciprocating bending around the pulley, replacing the traditional friction mode of deep winding between yarns, which is more in line with the actual force state of tendon rope transmission of robot dexterity hand.

[0018] 2. Precise size monitoring: The displacement of the tail end b is monitored in real time by a scale, which can quantify the plastic deformation and creep performance of the tendon chord during fatigue, providing data support for the control algorithm.

[0019] 3. Multidimensional testing indicators: Simultaneously obtain two key data points, fatigue cycles (fracture cycles) and dimensional stability (elongation), to comprehensively evaluate tendon chord performance. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the apparatus structure for the testing method of the present invention.

[0021] Explanation of icon numbers:

[0022] ①-Motor, ②-Weights, ③-Scale, ④-Upper pulley, ⑤-Lower pulley

[0023] a - Initial position, b - Tail end fixing point. Detailed Implementation

[0024] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0025] The illustrations provided in this embodiment are only intended to illustrate the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0026] It should be noted that existing chord fatigue tests mostly employ methods similar to ASTM D 6611-16, such as yarn-to-yarn friction fatigue testing, which tests the durability of mutual friction under deep yarn winding. However, this type of method deviates significantly from actual working conditions. In practical work, the chords of robot dexterity hands mainly bear fatigue loads from contact wear and reciprocating bending around pulleys. Furthermore, existing yarn-to-yarn friction testing methods cannot effectively characterize the dimensional changes (such as creep and elongation) of the chords during stress. The dimensional stability of the chords is crucial for constructing accurate algorithm models and ensuring the precision of the control system. Therefore, there is an urgent need for a testing method that can accurately simulate actual working conditions and simultaneously monitor the bending fatigue life and dimensional stability of the chords. This paper proposes a testing method for the bending fatigue cycles and dimensional stability of chords, which can truly reflect the fatigue life and deformation characteristics of chords in practical applications, including:

[0027] Step S1: Clamping the sample and initial positioning. Control the testing machine to return to the zero position and fix the head end of the sample to be tested and mark the initial position a. The sample passes around two pulley sets and crosses when passing around one of the pulley sets. Load a weight at the tail end of the sample, mark and record the reading L0 of the tail end b on the scale in the initial state.

[0028] Step S2: Set the motor's loading frequency and the target number of loading cycles;

[0029] Step S3: Perform a reciprocating fatigue test;

[0030] Step S4: If the specimen fractures before reaching the target loading number, record the fatigue number at the time of fracture.

[0031] Step S5: If the sample does not fracture after reaching the target number of loading cycles, measure and record the reading L1 on the scale corresponding to the tail end b after loading is completed.

[0032] The test equipment must have at least one pulley system, with each system consisting of at least two pulleys. A pulley system can be constructed between a fixed point, a lower pulley, and an upper pulley. Referring to ASTM D 6611-16, the crossing of the specimen can be achieved by rotating the pulleys, with a rotation angle greater than or equal to 180°; preferably between 180° and 360°. The weight of the weight mentioned in step S1 is within the load-bearing range of the testing equipment, preferably between 0.1 kg and 10 kg. The position change of end b mentioned in steps S1 and S5 can be measured by a scale, or by image acquisition or laser ranging. Recording the fatigue number at the time of fracture in step S4 can be achieved by placing a trigger device below the weight; after the specimen fractures, the weight falls and triggers the recording signal, or by image acquisition.

[0033] Example 1:

[0034] A tendon rope made of ultra-high molecular weight polyethylene with a diameter of 0.9 mm and a linear density of 0.55 g / m was selected and subjected to bending fatigue test around a pulley under a certain load and frequency.

[0035] Step S1: Sample clamping and initial positioning. Control the testing machine to return to the initial position, fix the head end of the sample to be tested and mark the initial position a, such as... Figure 1 The sample shown is passed around two pulley sets with an inner diameter of 34 mm. The pulleys cross each other when passing around one of the pulley sets. A weight of 2 kg is loaded at the tail end of the sample. The initial reading of the tail end b on the scale is marked and recorded as 12 mm.

[0036] Step S2: Set the motor loading frequency to 60 times / min and the target loading count to 100,000 times;

[0037] Step S3: Perform a reciprocating fatigue test;

[0038] Step S4: If the specimen fractures before reaching the target loading number, record the fatigue number at the time of fracture.

[0039] Step S5: If the sample does not break after reaching the target number of loading cycles, measure and record the reading of the tail end b on the scale after loading is completed, which is 14 mm.

[0040] Test results:

[0041] Lower wheel rotation angle 180° 360° 540° 720° 900° 1080° Load (kg) 2 2 2 2 2 2 Frequency (Hz) 60 60 60 60 60 60 Number of pulleys 6 6 6 6 6 6 Number of fractures Unbroken 5372 3827 530 92 67 The elongation of b after 100,000 times 2mm

[0042] Test Result Analysis:

[0043] According to ASTM D 6611-16, the yarn-to-yarn friction fatigue test method is used to test the durability of yarns rubbing against each other at a depth of 1080°. The tendon chord wore down quickly and broke after 67 cycles under these conditions. In actual operation, the tendon chords of a robotic dexterous hand mainly experience slight contact wear and do not involve deep winding. The same sample did not break after 100,000 cycles under a light winding of 180°, but it elongated by 2 mm. Existing test methods have not yet been able to measure and characterize this fatigue elongation.

[0044] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0045] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for testing the bending fatigue cycles and dimensional stability of chordae tendons, characterized in that, Includes the following steps: Step S1: Clamp the sample and position it initially. Control the testing machine to return to the zero position and fix the head end of the sample to be tested and mark the initial position a. The sample passes around two pulley sets and crosses when passing around one of the pulley sets. Load a weight at the tail end of the sample, mark and record the reading L0 of the tail end b on the scale in the initial state. Step S2: Set the motor's loading frequency and the target number of loading cycles; Step S3: Perform a reciprocating fatigue test; Step S4: If the specimen fractures before reaching the target loading number, record the fatigue number at the time of fracture. Step S5: If the sample does not fracture after reaching the target number of loading cycles, measure and record the reading L1 on the scale corresponding to the tail end b after loading is completed.

2. The method according to claim 1, characterized in that, The pulley system described in step S1 shall have at least one set, and each set of pulleys shall consist of at least two pulleys.

3. The method according to claim 1, characterized in that, In step S1, at least one set of samples crosses in the pulley group.

4. The method according to claim 3, characterized in that, The cross-section of the samples can be achieved by rotating a pulley, and the rotation angle of the pulley must be greater than or equal to 180°; preferably between 180° and 360°.

5. The method according to claim 1, characterized in that, The weight of the weight mentioned in step S1 is within the range that the testing equipment can bear, preferably between 0.1 kg and 10 kg.

6. The method according to claim 1, characterized in that, The positional change of end b mentioned in steps S1 and S5 can be measured by a ruler, or it can be achieved by image acquisition or laser ranging.

7. The method according to claim 1, characterized in that, The recording of fatigue counts at the time of fracture in step S4 can be achieved by setting a trigger device below the weight, triggering the recording of the signal when the weight falls after the sample fractures, or by using image acquisition or other methods.

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