Method for testing service life of wire transmission system of minimally invasive surgical instrument

Abstract

The invention relates to the field of fatigue life evaluation of transmission steel wires, in particular to a method for testing the life of a wire transmission system of a minimally invasive surgical instrument (MISI), which is based on the characteristics that the cross sectional area of a to-be-tested transmission wire is reduced, the resistance is changed and the current in a loop is changed because the to-be-tested transmission wire is broken after being subjected to bending fatigue. The number of broken wires of a to-be-tested transmission wire is estimated by constructing a measuring loop about the to-be-tested transmission wire and detecting the cross sectional area of the to-be-tested transmission wire in the measuring loop, and the service life of the wire transmission system of the minimally invasive surgical instrument is tested. Compared with a traditional manual counting mode, the broken wire calculation process and the service life testing process are automatic, cost is lower, calculation accuracy is more accurate, and the method is suitable for bending fatigue service life testing of a rope wheel transmission system using a small-diameter (smaller than 1 mm) transmission wire in medical instruments.

Description

Technical Field

[0001] The present invention relates to the field of transmission wire fatigue life assessment, and in particular to a method for testing the life of a minimally invasive surgical instrument (MISI) wire transmission system. The method is suitable for bending fatigue life testing of a rope pulley transmission system using a small diameter (less than 1 mm) transmission wire in medical devices. Background Art

[0002] Transmission wire ropes have the advantages of good flexibility, high strength and low cost. They are widely used in machinery, aerospace, ocean, medical or other fields that require transmission over long distances and in small volumes. The MISI wire transmission system is a rope pulley structure composed of transmission wires and pulleys. The wire transmission drives the joints to rotate to complete shearing, suturing and other operations during minimally invasive surgery. During the use of MISI, the transmission wire will experience repeated stretching and bending to produce fatigue. The postoperative cleaning and disinfection process will also accelerate the wear and aging of the transmission wire. Once the transmission wire fails due to fatigue, it will cause major accidents such as equipment damage and casualties. Therefore, it is of great significance to conduct life tests on the transmission wire.

[0003] The national standard GB / T 12347-2008 steel wire rope bending fatigue test method requires the following test procedures: the test parameters should be selected according to the relevant product standards or technical requirements, and the tension can be applied to the sample by mechanical or load, and the allowable deviation of the tension is ±3%. The test is stopped when the number of broken wires within one twist of the sample reaches the specified value, and the test is over. In order to detect whether the life of the transmission wire of MISI meets the experimental requirements of the above national standards, it is also necessary to conduct a bending fatigue test on it.

[0004] The Chinese patent application number CN202022464294.7 discloses a small diameter wire transmission bending fatigue life test device, which uses a conversion ring and a conversion disc to change the test wheel wrap angle, and uses a counting device to detect the broken wire of the transmission wire. The test method used by the device has the following problems:

[0005] 1. No other parameters except the wrap angle value are introduced, and it is impossible to explore the impact of changes in other parameters in MISI on life;

[0006] 2. The actual working conditions of MISI cannot be restored during the test, resulting in a large gap between the test life and the actual life;

[0007] 3. The counting device is greatly affected by the test environment and the counting accuracy is low. Summary of the invention

[0008] In view of this, the present invention proposes a test method for the life of a wire transmission system of a minimally invasive surgical instrument to solve the problems that the existing test method cannot restore the actual working conditions of MISI, the test parameters are single, and the broken wire count is not stable enough and has low accuracy.

[0009] The present invention adopts the following technical solutions:

[0010] A method for testing the life of a wire transmission system of a minimally invasive surgical instrument is applicable to a life testing system having a bending fatigue generating device, a measuring device and a data analysis and processing unit; wherein the bending fatigue generating device is provided with a rope pulley structure and a transmission wire to be tested, and the data analysis and processing unit is composed of a counting unit and a computing unit, and the testing steps include:

[0011] Step 1: Set various parameter values ​​of the bending fatigue generating device according to the test requirements, and initialize the counter to zero; construct a measurement loop for the sensor wire to be tested;

[0012] Step 2, start the bending fatigue generating device to make the transmission wire to be tested perform periodic reciprocating motion between the test wheels to generate bending fatigue, and use a calculator to count the test cycles and broken wires;

[0013] Step 3, collecting current data flowing through the transmission wire to be tested when the bending fatigue generating device is running, the current data is the current data of the transmission wire to be tested in the measuring loop obtained by using the measuring device;

[0014] Step 4: The calculation unit calculates the cross-sectional area of ​​the transmission wire to be measured in the measurement loop according to the current data obtained in step 3 according to the following formula:

[0015]

[0016] Among them, S is the cross-sectional area of ​​the transmission wire to be measured in the measurement loop, U is the preset DC power supply voltage, ρ is the resistivity of the transmission wire to be measured, and L is the length of the transmission wire to be measured in the measurement loop. To measure the current data of the transmission wire to be tested in the circuit;

[0017] Step 5: When the cross-sectional area obtained in step 4 reaches the preset threshold, the counter stops counting and counts the test cycle and the number of broken wires, thus completing the life test of the wire transmission system of the minimally invasive surgical instrument.

[0018] Furthermore, the method for constructing the measurement loop in step 1 includes:

[0019] Install the wire clamp on the transmission wire to be tested. The installation position of the wire clamp should meet the following requirements: the contact area between the transmission to be tested and the rope sheave structure is placed inside the loop, and the distance from the test wheel is greater than or equal to 3cm;

[0020] A DC power supply is used as a voltage device, and the wire clamps are connected to the DC power supply and the measuring device respectively to form a loop.

[0021] Furthermore, the measuring device is a high-precision ammeter.

[0022] Furthermore, the test cycle of step 2 is set according to the demand, and each test cycle is 4 seconds long, including a dynamic cycle and a static cycle. The bending fatigue generating device works for 3 seconds in a dynamic cycle, and the bending fatigue generating device is static for 1 second after a dynamic cycle ends, and enters the dynamic cycle of the next test cycle; the measuring device collects the current value I of the ammeter every 0.2 seconds in the static cycle. i , i is the sampling number, calculate the average of five current values ​​in a static cycle It is used as the current data of the transmission wire to be tested in the measurement circuit during the test cycle.

[0023] Furthermore, the data analysis and processing unit is also provided with a data storage function, which is used to interrupt the test process and save the current parameter information and test data when a test failure occurs.

[0024] After adopting the above technical solution, the present invention has the following advantages:

[0025] 1. The transmission wire to be tested will break after bending fatigue occurs, which will cause the cross-sectional area of ​​the transmission wire to be tested to decrease, and the resistance will change, changing the current in the circuit. Based on this feature, the method of the present invention estimates the number of broken wires of the transmission wire to be tested by constructing a measurement circuit and detecting the cross-sectional area of ​​the transmission wire to be tested in the measurement circuit. Compared with manual counting, the cost is lower, the calculation result is more accurate and reliable, and the broken wire calculation process and the life test process are automated.

[0026] 2. The present invention restores the actual working conditions of MISI in the test, sets the parameter values ​​of the bending fatigue generating device according to the test requirements, and realizes the life test of the wire transmission under different working conditions. The method is simple, easy to operate, and has high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the overall structure of a bending fatigue generating device selected from the embodiment;

[0028] Figure 2 It is a test flow chart of a test method for life of a wire transmission system of a minimally invasive surgical instrument in an embodiment;

[0029] Reference numerals:

[0030] 1. Drive module; 2. Load module; 3. Parameter adjustment module; 4. Test platform. DETAILED DESCRIPTION

[0031] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings and embodiments.

[0032] The present embodiment provides a method for testing the life of a wire transmission system of a minimally invasive surgical instrument, which is applicable to a life testing system having a bending fatigue generating device, a measuring device, and a data processing unit.

[0033] The structure of the bending fatigue generating device selected in this embodiment is as follows Figure 1 As shown, it includes a driving module, a parameter adjustment module and a load module; the driving module is responsible for driving the transmission wire to be tested to perform periodic reciprocating motion; the parameter adjustment module is responsible for changing the parameter values ​​of the rope pulley angle, rope pulley inclination angle and slack length in the rope pulley structure within the product standard range; the load module is responsible for providing and adjusting the tension for the transmission wire to be tested. Before the test, the bending fatigue generating device is first fixedly installed on the test platform, and each end of the transmission wire to be tested is respectively fixed or wound in the designated area of ​​the bending fatigue generating device. Then follow the steps below to complete the test of the life of the wire transmission system of minimally invasive surgical instruments. The test implementation process is as follows: Figure 2 As shown, including:

[0034] Step 1: Set various parameter values ​​of the bending fatigue generating device according to the test requirements, such as the sheave angle, sheave inclination and slack length, and initialize the counter to zero; construct a measurement loop for the sensor wire to be tested. In this embodiment, the setting of various parameter values ​​of the bending fatigue generating device is completed by the parameter adjustment mode and the load. The construction method of the measurement loop is:

[0035] Install a wire clamp on the transmission wire to be tested. The installation position of the wire clamp should meet the following requirements: the contact area between the transmission to be tested and the rope pulley structure is placed inside the loop, and the distance from the test wheel is greater than or equal to 3 cm. Use a DC power supply as a voltage device, connect the wire clamp to the DC power supply and the measuring device respectively, and form a loop. This embodiment uses a high-precision ammeter as the measuring device.

[0036] Step 2: Start the bending fatigue generating device to make the transmission wire to be tested perform periodic reciprocating motion between the test wheels to generate bending fatigue, and use a calculator to count the test cycles and broken wires. The test cycle is set according to the needs. Each test cycle is 4 seconds long, including a dynamic cycle and a static cycle. The bending fatigue generating device works for 3 seconds in one motion cycle. After one motion cycle, the bending fatigue device is static for 1 second and enters the motion cycle of the next test cycle.

[0037] Step 3: Collect the current data flowing through the transmission wire to be tested when the bending fatigue generating device is running. The current data is the current data of the transmission wire to be tested in the measuring loop obtained by the measuring device. The measuring device collects the current value of the ammeter every 0.2 seconds during the static period, i is the sampling number, and calculates the average of the five current values ​​in one static period as the current data of the transmission wire to be tested in the measuring loop during the test period.

[0038] Step 4: The calculation unit calculates the cross-sectional area of ​​the transmission wire to be measured in the measurement loop according to the current data obtained in step 3 according to the following formula:

[0039]

[0040] Among them, S is the cross-sectional area of ​​the transmission wire to be measured in the measurement loop, U is the preset DC power supply voltage, ρ is the resistivity of the transmission wire to be measured, and L is the length of the transmission wire to be measured in the measurement loop. To measure the current data of the transmission wire to be tested in the circuit;

[0041] Step 5: When the cross-sectional area obtained in step 4 reaches the preset threshold, the counter stops counting and counts the test cycle and the number of broken wires, completing the life test of the wire transmission system of the minimally invasive surgical instrument. The solid arrows in the figure are the winding order of the transmission wire to be tested, the dotted arrows are the direction of the current in the loop, and the hollow arrows are the direction of control signal transmission.

[0042] During implementation, the life test system will inevitably fail. Therefore, in this embodiment, a data storage unit is also provided in the test data analysis and processing unit. The data storage unit is used to obtain parameter information and test data of the current test cycle, and save the current parameter information and test data when a test failure occurs or the test process is interrupted.

[0043] In summary, the test method for the life of the wire transmission system of minimally invasive surgical instruments provided in this embodiment restores the actual working conditions of MISI in the test, solves the problems of single test parameters, unstable counting and low precision, and can perform life tests of wire transmission under different working conditions.

[0044] The above description is only used to illustrate the technical solution of the present invention rather than to limit it. Other modifications or equivalent substitutions made to the technical solution of the present invention by ordinary technicians in this field should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for testing the life of a wire transmission system of a minimally invasive surgical instrument, which is applicable to a life testing system having a bending fatigue generating device, a measuring device and a data analysis and processing unit; the bending fatigue generating device is provided with a rope pulley structure and a transmission wire to be tested, and the data analysis and processing unit is composed of a counting unit and a computing unit, and is characterized in that: The test method includes the following steps: Step 1: Set various parameter values ​​of the bending fatigue generating device according to the test requirements, and initialize the counter to zero; construct a measurement loop for the sensor wire to be tested; Step 2, start the bending fatigue generating device to make the transmission wire to be tested perform periodic reciprocating motion between the test wheels to generate bending fatigue, and use a calculator to count the test cycles and broken wires; Step 3, collecting current data flowing through the transmission wire to be tested when the bending fatigue generating device is running, the current data is the current data of the transmission wire to be tested in the measuring loop obtained by using the measuring device; Step 4: The calculation unit calculates the cross-sectional area of ​​the transmission wire to be measured in the measurement loop according to the current data obtained in step 3 according to the following formula: Among them, S is the cross-sectional area of ​​the transmission wire to be measured in the measurement loop, U is the preset DC power supply voltage, ρ is the resistivity of the transmission wire to be measured, and L is the length of the transmission wire to be measured in the measurement loop. To measure the current data of the transmission wire to be tested in the circuit; Step 5: When the cross-sectional area obtained in step 4 reaches the preset threshold, the counter stops counting and counts the test cycle and the number of broken wires, thus completing the life test of the wire transmission system of the minimally invasive surgical instrument.

2. A method for testing the life of a wire transmission system of a minimally invasive surgical instrument according to claim 1, characterized in that: The method for constructing the measurement loop in step 1 includes: Install the wire clamp on the transmission wire to be tested. The installation position of the wire clamp should meet the following requirements: the contact area between the transmission to be tested and the rope pulley structure is placed inside the loop, and the distance from the test wheel is greater than or equal to 3cm; A DC power supply is used as a voltage device, and the wire clamps are connected to the DC power supply and the measuring device respectively to form a loop.

3. A method for testing the life of a wire transmission system of a minimally invasive surgical instrument according to claim 1, characterized in that: The measuring device is a high-precision ammeter.

4. A method for testing the life of a wire transmission system of a minimally invasive surgical instrument according to claim 1, characterized in that: The test cycle of step 2 is set according to the demand. Each test cycle is 4 seconds long, including a dynamic cycle and a static cycle. The bending fatigue generating device works for 3 seconds in a dynamic cycle. After a dynamic cycle, the bending fatigue generating device is static for 1 second and enters the dynamic cycle of the next test cycle. The measuring device collects the current value I of the ammeter every 0.2 seconds in the static cycle. i , i is the sampling number, calculate the average of five current values ​​in a static cycle It is used as the current data of the transmission wire to be tested in the measurement circuit during the test cycle.

5. A method for testing the life of a wire transmission system of a minimally invasive surgical instrument according to any one of claims 1 to 4, characterized in that: The data analysis and processing unit is also equipped with a data storage function, which is used to interrupt the test process and save the current parameter information and test data when a test failure occurs.

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