System for evaluating bearing degradation

Abstract

A system and method for assessing bearing degradation includes a first support, a shaft, and at least one vibration sensor. The first support is configured to hold the bearing. The shaft defines an axial direction along a length of the shaft and may be coupled to a ferrule of the bearing to apply an axial mechanical load on the bearing. The first inductive probe and the second inductive probe may be inductively coupled with the shaft at respective probe locations spaced apart along the shaft. The second current probe is arranged to measure the circulating current in response to the first inductive probe generating an induced current in the shaft. At least one vibration sensor is disposed at the first support. The at least one vibration sensor is arranged to provide a vibration signal in response to the measured circulating current while sensing vibration.

Description

[0001] Related applications

[0002] This application claims the benefit of priority to Singapore patent application No. 10202300062Y filed on January 9, 2023, the contents of which are hereby incorporated by reference in their entirety for all purposes. Technical Field

[0003] The present application relates to the testing of bearings, and more particularly to a system and method for testing bearing degradation. Background Art

[0004] Bearings play a vital role in nearly every machine with moving parts. In some applications, bearing failure can result in costly equipment downtime and repair costs. In other applications, bearing failure can even lead to safety issues. As part of predictive maintenance, it would be beneficial if the service life of any set of bearings (the period during which bearing failure is unlikely) could be predicted so that bearings can be replaced before catastrophic failure occurs. Unfortunately, with advances in power electronics and the electrification of engine drive systems, bearings are often subjected to electrical loads in addition to mechanical loads. The impact of electrical loads is more difficult to determine than mechanical loads. Some bearings fail after years of use in one application, while the same bearing in another application may fail within a month. It is believed that as many as 40% of all engine failures can be attributed to bearing failure. Summary of the Invention

[0005] In one aspect, the present application discloses a system comprising a first support, a shaft, a first inductive probe, a second inductive probe, and at least one vibration sensor. The first support is configured to retain a bearing. The shaft defines an axial direction along its length. The shaft is coupleable to a race of the bearing to apply an axial mechanical load to the bearing. The first and second inductive probes are inductively coupled to the shaft at corresponding probe locations. The corresponding probe locations are spaced apart along the shaft. The second current probe is configured to measure a circulating current in response to an induced current generated in the shaft by the first inductive probe. The at least one vibration sensor is disposed on the first support. The at least one vibration sensor is configured to provide a vibration signal in response to sensing vibration while measuring the circulating current.

[0006] On the other hand, the present application discloses a method comprising the following steps: (i) applying an axial mechanical load to a bearing held by a first support, the axial mechanical load being applied by a shaft coupled to a ring of the bearing, the shaft defining an axial direction along the length of the shaft; (ii) generating an induced current in the shaft using a first induction probe; (iii) measuring a circulating current using a second induction probe, the first induction probe and the second induction probe being inductively coupled to the shaft at corresponding probe positions, the corresponding probe positions being spaced apart along the shaft; and (iv) obtaining a vibration signal in response to sensing vibration while measuring the circulating current, wherein the vibration signal is provided by at least one vibration sensor disposed at the first support.

[0007] The method may include determining expected bearing degradation over a service life based on a health status of the bearing after an accelerated testing period, wherein the accelerated testing period is shorter than the service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Various embodiments of the present application will be described with reference to the following drawings:

[0009] Figure 1 is a schematic diagram of a system according to an embodiment of the present application;

[0010] Figure 2 It is a cross-sectional view of the various components of the bearing.

[0011] Figure 3 is a cross-sectional view of the mechanical load zone of the system;

[0012] Figure 4 is a schematic block diagram of the control subsystem of the system;

[0013] Figures 5A to 5C A conceptual diagram showing the system prototype is provided, and Figure 5D An image showing the built prototype;

[0014] Figure 6 is a schematic flow chart of a method according to an embodiment of the present application;

[0015] Figure 7A and Figure 7B Here is an image of a ball bearing and part of a new bearing ring before testing;

[0016] Figure 8A Show Figure 7A The image of the ball bearing shown after testing;

[0017] Figure 8B Show Figure 7B An image of a portion of the ferrule after testing is shown;

[0018] Figure 9 The vibration signals are measured after 60 hours of testing and 120 hours of testing using the prototype of the system;

[0019] Figure 10 is a side view image of another prototype of the system;

[0020] Figure 11 is the vibration signal measured along the x-axis of the system on day 1, day 15, and day 30 of the evaluation program;

[0021] Figure 12 yes Figure 11 The respective distribution diagrams of the measured vibration signals are shown;

[0022] Figure 13 is the vibration signal measured along the y-axis of the system on the 1st, 15th and 30th day of the evaluation program test;

[0023] Figure 14 yes Figure 13 The respective distribution diagrams of the measured vibration signals are shown;

[0024] Figure 15 is the vibration signal measured along the z-axis of the system on day 1, day 15, and day 30 of the evaluation program;

[0025] Figure 16 yes Figure 15 The respective distribution diagrams of the measured vibration signals are shown;

[0026] Figure 17 a graphical representation showing the average and maximum values of the vibration signal; and

[0027] Figure 18 Graph showing the standard deviation of a vibration signal. DETAILED DESCRIPTION

[0028] The following detailed description will be made with reference to the accompanying drawings, which show details and embodiments of the present application for illustrative purposes. Features described in the context of one embodiment may also apply to the same or similar features in other embodiments, even if not explicitly described in those other embodiments. Applications and / or combinations and / or substitutions described for features in the context of one embodiment may also apply to the same or similar features in other embodiments.

[0029] In the context of various embodiments, the articles “a,” “an,” and “the” used with respect to features or elements include reference to one or more features or elements.

[0030] In the context of various embodiments, the term "about" or "approximately" as applied to a numerical value encompasses the exact value and a reasonable difference as commonly understood in the relevant technical field, such as within 10% of the specified value.

[0031] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0032] The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any "exemplary" embodiment described herein is not necessarily to be construed as preferred or advantageous over other embodiments. As used herein, the singular "a" and "an" should be understood to include the plural "one or more" unless the context clearly dictates otherwise.

[0033] The terms "first" and "second" used in the description and claims are for brevity and clarity only and do not necessarily indicate priority or order unless the context requires otherwise. The terms "about" and "approximately" applied to numerical values encompass both the exact value and reasonable differences that would be understood by those skilled in the art, and the terms "generally" and "substantially" should be interpreted in a similar manner unless otherwise indicated.

[0034] Some methods may be described in terms of steps only to aid understanding and / or facilitate reference. In this application, the divisions between different steps may be used only for ease of reference. It will be understood that in actual implementation, there may not be a clear division or transition from one step to another subsequent step. There may be a certain degree of overlap between steps, and / or multiple steps may occur or be performed simultaneously, etc.

[0035] As used herein, the terms "simultaneous" or "concurrently" are used broadly to refer to two or more occurrences (or events) that at least partially overlap in time, wherein the occurrences may not start and / or end at the same time.

[0036] As used herein, the terms "load" and "force" are used interchangeably unless the context requires otherwise.

[0037] Motor drive systems incorporating high-speed switching devices generate high-amplitude common-mode (CM) voltages that vary over time, with relatively fast rates of voltage change. Common-mode voltages result in undesirable common-mode currents. Common-mode currents circulate in and through the engine drive system. It is expected that common-mode currents will vary with different engine drive system configurations and over time as engine drive system conditions change during use. Common-mode currents also flow through bearings (referred to as circulating bearing currents), and these can lead to various defects, such as frosting and fluting at the rings, and pitting on the rolling elements. In the event of lubricant wear, circulating bearing currents can result in sparks or discharges, which can cause bearing pitting.

[0038] Systems with electrical load areas

[0039] Figure 1 is a schematic diagram of a system 100 according to some embodiments of the present application. The system 100 can be used to provide a repeatable and quantifiable assessment of potential bearing degradation in various applications, including but not limited to applications where common mode currents may be present.

[0040] The system 100 can be used to evaluate different types of bearings. For ease of reference and without limitation, the system 100 can be used to evaluate the degradation characteristics of bearings 900 / 902, such as Figure 2 The bearing 900 / 902 is schematically shown in cross-section. The bearing 900 / 902 may include a plurality of balls 910 separated by a cage 940. The balls 910 and the cage 940 are disposed between an outer ring 920 and an inner ring 930.

[0041] Reference again Figure 1 System 100 includes an electrical load zone 102 integrated with a mechanical load zone 103. System 100 includes a first support 111, to which a bearing under test (BUT) 900 can be mounted. In the illustrated example, electrical load zone 102 and mechanical load zone 103 are located on opposite sides of first support 111. In other examples, electrical load zone 102 and mechanical load zone 103 can be located on the same side of first support 111.

[0042] A shaft 140 extends between a first support 111 and a second support 112. The second support 112 is spaced apart from the first support 111 along a reference axis or axial direction 101. The axial direction 101 can be defined by the shaft 140. A support bearing 902 (also referred to as a second bearing) is mounted at the second support 112. The support bearing 902 is preferably selected to have the same dimensions as the BUT 900 to facilitate alignment of the shaft 140.

[0043] Shaft 140 extends beyond the second support and to a drive end 141. Drive end 141 is operably coupled to a motor 200, such as an induction motor, so that motor 200 can drive rotation of drive end 141 and, thereby, shaft 140. In the illustrated example, drive end 141 is part of a belt and pulley sub-system. In other examples, drive end 141 may be coupled to motor 200 in a different manner, such as, but not limited to, a set of gears.

[0044] Two sensing probes 340 (e.g., a current input probe 342 and a current receiving probe 344) are disposed in the electrical load region 102 between the first support 111 and the second support 112. In this application, the terms "probe," "inductive coupling probe," and "sensing probe" are used interchangeably unless the context dictates otherwise. The sensing probes used (e.g., input probe, measurement probe, receiving probe, etc.) may be physically similar but have different names to better illustrate the functionality of the respective probes within the context of the embodiments. Each sensing probe 340 may be clamped to the shaft 140 or otherwise positioned to interface with the shaft at a probe location. During operation, the sensing probes 340 may be configured to generate an induced current in the shaft 140. When used in this mode, the sensing probes 340 may be described as input probes. Alternatively, during operation, an induced current may be generated in the sensing probes 340 and the induced current may be measured. When used in this mode, the sensing probes 340 may be described as measurement probes.

[0045] One or more vibration sensors 310 are provided at the first support 111. A discharge detector 350 is provided near the first support 111, and more specifically, near the BUT 900. Optionally, a temperature sensor 330 is coupled to measure the temperature of the BUT 900 / the temperature near the BUT 900.

[0046] Mechanical load area

[0047] The shaft 140 also extends between the first support 111 and the third support 113. In this example, the first support 111 is axially aligned with the second support 112 and the third support 113 and is disposed between the second support 112 and the third support 113.

[0048] The shaft 140 can engage the third support 113 in various ways. In this example, the shaft 140 extends beyond the third support 113 and to an axial load end 143, and the axial load end 143 is configured to apply a mechanical load in an axial direction to the BUT 900. A load cell 320 can be coupled to the shaft 140 between the second support 112 and the first support 111. The load cell 320 is configured to measure the axial mechanical load applied to the BUT 900.

[0049] Figure 3 A more detailed view of the mechanical load zone 103 according to an embodiment of the system 100 is provided. The axial load end 143 of the shaft 140 can be threadedly engaged with an adjustable fastener 153. For example, a larger mechanical load can be applied to the BUT 900 by driving the adjustable fastener 153 toward the third support 113, and a smaller mechanical load can be applied to the BUT 900 by moving the adjustable fastener 153 away from the third support 113. In the illustrated example, the adjustable fastener 153 and the axial load end 143 of the shaft 140 can form a nut-and-bolt pair. The adjustable fastener 153 can be manually or machine-actuated to "tighten" the threaded engagement and apply a larger, axially directed mechanical load to the BUT 900. The adjustable fastener 153 can also be manually or machine-actuated to "loosen" the threaded engagement and apply a smaller, axially directed mechanical load to the BUT 900.

[0050] The load meter 320 may be disposed in a load meter holder 322. The load meter holder 322 may be clamped around the shaft 140.

[0051] A tapered bearing 154 may be provided between the shaft 140 and the inner race 930 of the BUT 900 to transfer axial mechanical loads to the BUT 900. For example, the shaft 140 may have a tapered bearing to engage with the inner race of the BUT 900 and simultaneously push directly or indirectly against the inner race 930 of the BUT 900 in the axial direction 101.

[0052] The outer ring 920 of the BUT 900 is fixedly coupled to the first support 111 (the first support 111 also serves as a bearing retainer).

[0053] Control subsystem

[0054] In some embodiments, system 100 can be at least partially manually configured and / or operated to perform the method for assessing bearing degradation. In some other embodiments, system 100 can include a control subsystem 400 managed by a processor 410. Processor 410 can be in the form of one or more devices, such as, but not limited to, computing devices, programmable devices, integrated circuits, and the like.

[0055] Figure 4 FIG2 is a schematic block diagram of an example control subsystem 400 of system 100. System 100 may include a processor 410 in operable signal communication with a memory 412 and a user interface 414. Processor 410 may be configured to perform a method for assessing bearing degradation by executing computer-readable instructions, such as those stored in memory 412. Data collected by various sensors (collectively referred to as 300) may be stored in memory 412, output via user interface 414, and / or processed by processor 410.

[0056] Based on the measured and / or calculated parameters, the processor 410 can be in operable signal communication with the motor driver 420 to controllably rotate the shaft 140 at a selected speed during the evaluation procedure. The processor 410 can also be in operable signal communication with the axial force controller 430 to controllably apply the axial mechanical load at a selected load level. The processor 410 can be in operable signal communication with the pulse generator 440 to trigger the generation of a time series of high voltage pulses that are fed to a sensing probe, referred to as the current input probe 342. The processor 410 can be in operable signal communication with a heater 450 (e.g., a cartridge heater).

[0057] method

[0058] To assist understanding, in the following description of the proposed method 500, reference will be made to Figures 1 to 6 Specifically, Figures 5A to 5C A conceptual diagram showing a prototype of system 100 is shown, and Figure 5D An image showing a prototype system 100 that has been built and used for testing. Figure 6 is a schematic flow chart of a method 500 according to various embodiments.

[0059] Electrical load and axial mechanical load

[0060] The method 500 includes the steps of applying an electrical load (520) to the BUT 900 (also referred to as "electrical loading" 520) and applying an axially oriented mechanical load (530) to the BUT 900 (also referred to as "axial mechanical loading" 530), wherein the electrical loading 520 and the axial mechanical loading 530 are applied simultaneously.

[0061] The method 500 includes electrically loading (520) simultaneously with axial mechanical loading (530), wherein the axial mechanical loading (530) includes a mechanical load force having at least an axial component. The axial component of the mechanical load force is parallel or substantially parallel to the shaft 140, such as parallel to the axial direction 101. The shaft 140 can be supported by a support 110 (e.g., an end support, a bearing retainer, etc.).

[0062] In method 500, electrical loading (520) and axial mechanical loading (530) are performed simultaneously with the bearing 900 in a state of use (e.g., the bearing 900 in a rotating state 510). For simplicity, a rotating bearing refers to a state in which the outer race and inner race of the bearing are in relative rotational motion. In some examples, the bearing 900 may be further subjected to stress conditions (540), including, but not limited to, varying temperature conditions, varying mechanical load conditions (in addition to the axial mechanical loading 530), and the like.

[0063] In some examples, test data can be collected while the bearing is rotating (510) (data collection step 550). Method 500 can also include a step (560) of predicting the reliability or life (service life) of other bearings similar in design and / or manufacture to BUT 900.

[0064] The concurrent events do not all need to begin at the same time. In one example, an axial mechanical load 530 can be applied to the BUT 900 (at the mechanical load region 103) before the engine 200 begins to rotate the shaft 140. As the shaft 140 rotates, the BUT 900 rotates (510). For example, the outer ring 920 can be secured by the first support 111, and the inner ring 930 rotates with the shaft 140. While the BUT 900 rotates (510) and is subjected to the axial mechanical load (530), an electrical load (520) is then applied to the BUT 900. Test data is then collected in a data collection step (550).

[0065] In another example, upon completion of data acquisition (550), the BUT 900 may be de-energized (520) before rotation of the shaft 140 ceases. The BUT 900 may be in a stationary state before the axial mechanical load (530) is removed. In other words, concurrent events do not all need to cease at the same time.

[0066] Pulse electrical loading

[0067] In the present application, the electrical loading 520 may be a pulsed electrical loading 520. For example, the electrical loading 520 may include multiple instances of the step (522) of inputting voltage pulses to the shaft 140. In some examples, the electrical loading 520 applied over a period of time includes the step (522) of inputting a series of high voltage pulses at a pulse frequency over the period of time.

[0068] In some examples, a high-voltage pulse generator 440 can be electrically connected to the first sensing probe 340. The pulse generator 440 can be configured to feed a pulsed current to the rotating shaft 140 through the first sensing probe 340, so that the first sensing probe 340 functions as an input probe 342. This has been observed to generate a pulsed bearing circulating current or common-mode current (also referred to as a pulsed cyclic bearing current) flowing through the BUT 900. The pulsed current can be a pulsed current with a controllable and variable amplitude to simulate, for example, varying power rating conditions experienced in some engine drive systems.

[0069] Electrical loading 520 may also include a step of measuring induced bearing current (524). In some examples, a second sensing probe 340 is clamped to the same shaft 140. The first sensing probe and the second sensing probe are coupled at corresponding probe positions. The plurality of probe positions are spaced apart along the shaft 140. The second sensing probe 340 may be used as a measurement probe 344 to monitor the induced current (also referred to as the induced bearing current) flowing through the BUT 900.

[0070] Other measurements

[0071] Other probes 340 may also be included. For example, two spaced-apart shaft voltage probes may be used with their carbon fiber tips in contact with the shaft 140 to measure the induced end-to-end shaft voltage.

[0072] Data acquisition (550) may include acquiring signals from the measurement probe 344. Data acquisition (550) may include acquiring signals from the shaft voltage probe. Data acquisition (550) may include acquiring signals from the load meter 320. Data acquisition (550) may include measuring the temperature at / near the BUT 900 using, for example, the temperature sensor 330. Data acquisition may include recording the number of discharges using the discharge detector 350. Data acquisition (550) may include acquiring signals from at least one or more vibration sensors 310 disposed at / on the first support 111 or at / on the BUT 900, the vibration sensor 310 being, for example, an accelerometer.

[0073] The method 500 enables the acquisition of sufficient and relevant data to provide a practical and useful estimate of the useful life of the BUT 900. This capability was not available prior to the present application.

[0074] Example 1

[0075] Figure 7A and Figure 7B This is an image of a portion of ball 910 and ring 920 / 930 before a new bearing is used. The surface of ball 910 and the inner surface of ring 920 / 930 are smooth and have no visible defects. Figure 8A and Figure 8B Show Figure 7B Shown is an image of the same ball 910 and the same ring 920 / 930 after 120 hours of accelerated testing using a system prototype. Figure 8A The surface of the ball 910 shown after accelerated testing shows signs of wear and tear, including abrasion marks and scratches as well as visible pitting 602. Similarly, Figure 8B The surface of the ferrule 920 / 930 is shown to exhibit visible pitting 604 after accelerated testing.

[0076] Figure 9 Graphs of vibration signals obtained after 60 hours of accelerated testing and 120 hours of accelerated testing are shown. A vibration signal (also called a measured vibration signal) is a measurement result obtained from one or more vibration sensors. As can be seen, after 120 hours of accelerated testing, the acceleration measurement results corresponding to the vibration level exhibited by the bearing under test (BUT) are characterized by an amplitude range that exceeds acceptable / preset upper and lower limits. These upper and lower limits can be preset based on the vibration characteristics of a new bearing.

[0077] The bearings can experience degradation similar to that experienced during actual use of similar bearings. Notably, using the proposed system, degradation can be observed in as little as 120 hours. In contrast, similar levels of degradation in similar bearings during actual use can take weeks to months. Further testing verified that the measured vibration signal corresponds to the degree of degradation. In other words, the proposed system can be used to provide accelerated testing with meaningful and measurable outputs, such as a measurable vibration signal.

[0078] Example 2

[0079] Figure 10is a side view image of another system prototype for another bearing degradation assessment. In this example, the engine can be controlled by a variable frequency driver (VFD), and the axial mechanical load is a controllable axial force assisted by an axial force control panel. The temperature of the BUT is controllably increased using a heat gun. A temperature sensor is provided near the BUT. The current input probe and the current receiving probe are inductively coupled to multiple points spaced apart on the shaft to measure the current / voltage across the BUT (also referred to as bearing current / bearing voltage for simplicity). The vibration sensor is provided on the bearing support or the first support. The electrical load is provided by the current input probe and measured by the current receiving probe. The mechanical load zone includes a spring that is loaded (preloaded and axially oriented) to apply the required axial mechanical load. A discharge detector is provided to monitor the number of discharges.

[0080] The present system and method can be used in a variety of applications. For example, the system and method can be used as part of a product development process to evaluate a newly developed bearing intended for use in a motor drive system, such as an electric vehicle.

[0081] The test conditions can be selected or determined based in part on the actual operating conditions of the bearing in the engine-driven system. For example, the BUT can be tested within a temperature range of about 20°C to about 100°C. The axial mechanical load can be controllably applied within a range of zero (no load) to about 10 kN (kilonewtons). The shaft speed can be controlled by the engine within a range of zero (stationary) to about 2000 rpm (revolutions per minute).

[0082] The test conditions can be selected or determined based in part on the target lifespan (maximum expected lifespan) or target service life of the newly developed bearing. The applied electrical load can be set based on the amplitude (peak current) and frequency (pulse input frequency) of the input current pulse. The frequency of the input current pulse is preferably (and optionally) set to be relatively high to accelerate the test of the BUT.

[0083] Vibration signals can be used as health indicators. For example, the maximum and minimum values of the vibration signal of a new bearing (on day 1) can be selected as a baseline for comparison purposes. Vibration signals can be measured relative to any direction of interest. For ease of reference, some test results will be described relative to the x-, y-, and z-axes of an orthogonal reference system, where the y-axis is defined by the axis and the bearing is positioned in the xz plane.

[0084] Figure 11The vibration signal measured along the x-axis is shown for the 1st, 15th, and 30th day of testing under the evaluation procedure. It should be noted that the maximum positive and negative values of the vibration signal increase over time. Using the vibration signal on day 1 as a baseline, upper and lower limits can be set (e.g. Figure 11 On the 15th day, the vibration signal showed only a small deviation from the upper and lower limits. On the 30th day, the vibration signal showed a large deviation from the upper and lower limits.

[0085] The average and maximum values of the vibration signal are calculated based on the absolute value of the vibration signal. On day 1, the average value is 2.65 m / s 2 , and the maximum value is 24.6m / s 2 On the 15th day, the average value was 3.51m / s 2 , and the maximum value is 46.63m / s 2 On the first day, the average value was 5.23m / s 2 , and the maximum value is 75.26m / s 2 .

[0086] While average and maximum values are helpful, the present systems and methods advantageously provide the ability to further consider the distribution curve of the measured vibration signal. Figure 12 Show Figure 11 The corresponding distribution diagram of the measured vibration signal is shown. Figure 12 Provides a more objective way to determine upper and lower limits with reference to new bearings, and a more objective way to determine when the performance of a BUT has deteriorated to the point where bearing replacement is necessary.

[0087] Figure 13 The vibration signal measured along the y-axis of the system is shown, measured on day 1, day 15, and day 30 of the test. Figure 14 Show Figure 13 The corresponding distribution diagram of the measured vibration signal is shown.

[0088] Although the y-axis vibration shows an increasing trend with respect to time, the increase in the vibration signal value is smaller than that of the x-axis.

[0089] Figure 15 Shown are the vibration signals measured along the z-axis of the system, measured on days 1, 15, and 30 of the test. Figure 16 Show Figure 15 The corresponding distribution diagram of the measured vibration signal is shown in FIG. The vibration signal measured along the z-axis direction shows a similar trend to the vibration signal measured along the x-axis direction.

[0090] Figure 17 Show Figure 11 、 Figure 13 and Figure 15 A graphical representation of the average and maximum values of the vibration signal is shown. Figure 18 Shown based on Figure 12 、 Figure 14 and Figure 16 It is understood that determining the extent of bearing degradation solely through the average or maximum value may be affected by the measurement direction. In actual use, the path of the common-mode current may be complex, making it difficult to determine the more critical direction (for example, the direction where the vibration is greater and more indicative of ongoing bearing degradation). The standard deviation curve helps provide a clearer view of bearing degradation. Figure 18 It can be seen that the degradation rate increases (increasing standard deviation rate of change) after day 15. This could be used, for example, in a critical use application to indicate that the bearing should be replaced on day 15.

[0091] Example 3

[0092] In another exemplary test, the test conditions used included a shaft speed of 1500 rpm and room temperature, with no axial mechanical force applied. Common-mode currents (circulating bearing currents) were simulated in the BUT by inputting a peak current of 5 A at a pulse input frequency of 1000 Hz. After only 120 hours of test operation (equivalent to five days of continuous operation), the data collected was sufficient to predict the expected bearing life in actual use.

[0093] More Examples

[0094] System 100 can be used as a bearing testing system to evaluate bearings in various applications, including but not limited to robotics, automated guided vehicles, electric vehicles, electric aircraft, and electric boats. The table below provides a summary of the different test conditions used for these applications, demonstrating that a single unit of the proposed system 100 is capable of providing a comprehensive assessment of bearing performance in various operating scenarios.

[0095] In robotics applications, typical bearings may be subjected to operating conditions that vary significantly depending on the type of robot. For example, low-power robots may be expected to handle mechanical loads (axial mechanical loads) of up to 100N; medium-power robots may be expected to handle mechanical loads (axial mechanical loads) ranging from about 100N to about 500N; and high-power robots may be expected to handle mechanical loads (axial mechanical loads) of about 500N or more.

[0096] Table 1. Robot applications

[0097]

[0098] As described above, beneficial bearing performance test results should preferably include an assessment of the selected bearing's performance under both mechanical and electrical loads. Electrical loads are related to the common-mode voltage present in a running robotic device. Simulating electrical loads using only actual robots of each type would be prohibitively expensive. The proposed system 100 can be used to obtain beneficial bearing performance test results corresponding to testing the BUT 900 on different types of robots, without requiring the use of actual robotic devices.

[0099] In many applications, it's beneficial for bearing manufacturers or product developers to estimate the service life of selected bearings. This avoids unnecessary costs by not replacing bearings prematurely, while allowing for timely maintenance, repair, and / or replacement before catastrophic failures can occur. For products like AGVs (automated guided vehicles), it's understandable that a sudden failure mid-transit could potentially cause the AGV to crash and cause damage upon impact with the ground.

[0100] Table 2 shows different test conditions that can be set in a prototype of the system 100 for testing bearings and evaluating their service life in different categories of AGVs. In other examples, actual evaluation of bearing performance can help select bearings for different categories of AGVs.

[0101] Table 2. AGV applications

[0102]

[0103] Bearings are fundamental engineering components that play a vital role in a wide range of applications. With the increasing popularity of electric vehicles (on land, in the air, and at sea), there is a pressing need for informative and comparative bearing performance evaluations. Table 3 provides a non-exhaustive list of examples of electric vehicles operating under varying or diverse conditions. Table 3 also shows test conditions that can be used for accelerated testing of various operating conditions or application scenarios.

[0104] Table 3. Electric vehicle applications

[0105]

[0106]

[0107] In the examples shown in Tables 1 to 3, "Engine Rated Power" refers to the rated power at which the engine 200 of the system 100 was operated during the test, "Speed" refers to the shaft speed or velocity at which the shaft 140 rotated during the test, and "Axial Load" refers to the axial mechanical load 530. In various examples, "Bearing Operating Temperature" refers to the operating temperature of the BUT 900. For example, "Bearing Operating Temperature" can refer to the temperature to which the BUT 900 was heated using the system's heater 450. For example, "Bearing Operating Temperature" can refer to the temperature measured by the temperature sensor 330. In various examples, "Bearing Current" can refer to the current input by the sensing probe 340 at the probe location or the current measured by the sensing probe 340.

[0108] According to various embodiments of the present application, system 100 includes a first support 111, a shaft 140, a first sensing probe 340, a second sensing probe 340, and at least one vibration sensor 310. First support 111 is configured to hold a bearing 900 (e.g., BUT 900). Shaft 140 defines an axial direction 101 along its length. Shaft 140 can be coupled to a race 920 / 930 of bearing 900 to apply an axial mechanical load 530 to bearing 900. First sensing probe 340 and second sensing probe 340 can be inductively coupled to shaft 140 at corresponding probe locations. The corresponding probe locations are spaced apart along shaft 140. Second current probe 340 is configured to measure a circulating current in response to an induced current generated in shaft 140 by first sensing probe 340. At least one vibration sensor 310 is disposed at first support 111. At least one vibration sensor 310 is configured to provide a vibration signal in response to sensing vibration while measuring the circulating current.

[0109] System 100 may further include a motor 200 coupled to shaft 140 to enable shaft 140 to rotate at a selected shaft speed. System 100 may further include a pulse generator 440 coupled to first sensing probe 340 and configured to generate a pulsed current characterized by a pulse frequency. Shaft 140 may be coupled to an inner race 930 of bearing 900, wherein first support 111 is coupled to an outer race 920 of bearing 900. System 100 may further include a heater 450 configured to heat bearing 900 to a predetermined temperature. System 100 may further include a discharge detector 350 configured to monitor the number of discharges at bearing 900.

[0110] The system may further include a processor 410, wherein the processor 410 is configured to execute a method 500, which includes the following steps: (i) acquiring a vibration signal from at least one sensor 300; and (ii) determining a state of health of the bearing 900 based on a comparison of the vibration signals acquired over a time period. The processor 410 may also be configured to determine the state of health of the bearing 900 based on a change in a standard deviation of the vibration signal over the time period. The processor 410 may also be configured to determine an expected bearing degradation over a service life based on the health of the bearing 900 after an accelerated testing period, wherein the accelerated testing period is shorter than the service life.

[0111] According to different embodiments of the present application, the method 500 includes the following steps: (i) applying an axial mechanical load 530 to a bearing 900 held by a first support 111, the axial mechanical load 530 being applied by a shaft 140 coupled to a ring 920 / 930 of the bearing 900, the shaft 140 defining an axial direction 101 along the length of the shaft 140; (ii) generating an induced current in the shaft 140 using a first sensing probe 340; (iii) measuring a circulating current using a second sensing probe 340, the first sensing probe 340 and the second sensing probe 340 being inductively coupled to the shaft 140 at corresponding probe positions, the corresponding probe positions being spaced apart along the shaft 140; and (iv) acquiring a vibration signal in response to sensing vibration simultaneously with the measured circulating current, wherein the vibration signal is provided by at least one vibration sensor 310 disposed at the first support 111.

[0112] The method 500 may include a step performed simultaneously with the electrical loading 520, wherein the step includes rotating the shaft 140 at a selected shaft speed. Generating an induced current in the shaft 140 may include inputting a pulsed current characterized by a pulse frequency. The pulse frequency may be based on an estimated number of discharges at the bearing 900 under actual use conditions. An axial mechanical load 530 may be applied to an inner race 930 of the bearing 900, wherein the first support 111 is coupled to the outer race 920 of the bearing 900. The method 500 may also include heating the bearing 900 to a preset temperature. The method 500 may also include determining a health state of the bearing 900 based on a comparison of vibration signals acquired over a time period. The health state of the bearing 900 may be based on a change in the standard deviation of the vibration signal over the time period.

[0113] Method 500 may include determining expected bearing degradation over a service life based on a health status of bearing 900 after an accelerated testing period, wherein the accelerated testing period is shorter than the service life.

[0114] All examples described herein, whether devices, methods, materials or products, including the examples presented in Tables 1 to 3, are presented for illustrative purposes and to aid understanding, and are not intended to be limiting or exhaustive. Modifications may be made by one of ordinary skill in the art without departing from the scope of the claims of this application.

Claims

1. A system comprising: a first support configured to retain a bearing; a shaft defining an axial direction along a length of the shaft, the shaft being coupleable to a race of the bearing to apply an axial mechanical load on the bearing; First sensing probe; a second current probe, the first and second current probes being inductively coupled to the shaft at respective probe locations spaced apart along the shaft, the second current probe being configured to measure a circulating current in response to the first current being induced in the shaft by the first current probe; as well as At least one vibration sensor is disposed at the first support, the at least one vibration sensor being configured to provide a vibration signal in response to sensing vibration while measuring the circulating current.

2. The system according to claim 1, further comprising: A motor is coupled to the shaft to enable the shaft to rotate at a selected shaft speed.

3. The system according to claim 1 or 2, further comprising: A pulse generator is coupled to the first sensing probe and configured to generate a pulse current characterized by a pulse frequency.

4. The system of any one of claims 1 to 3, wherein the shaft is coupled to an inner race of the bearing, and wherein the first support is coupled to an outer race of the bearing.

5. The system according to any one of claims 1 to 4, further comprising a heater configured to heat the bearing to a preset temperature.

6. The system according to any one of claims 1 to 5, further comprising a discharge detector configured to monitor the number of discharges at the bearing.

7. The system according to any one of claims 1 to 5, further comprising a processor configured to perform a method comprising: acquiring the vibration signal from the at least one sensor; as well as The health status of the bearing is determined based on a comparison of the vibration signals acquired over a time period.

8. The system of claim 7, wherein the processor is further configured to determine the health state of the bearing based on a change in a standard deviation of the vibration signal over the time period.

9. The system of claim 7 or 8, wherein the processor is further configured to determine expected bearing degradation over a service life based on the health of the bearing after an accelerated testing period, and wherein the accelerated testing period is shorter than the service life.

10. A method comprising: applying an axial mechanical load to a bearing held by a first support, the axial mechanical load being applied by a shaft coupled to a race of the bearing, the shaft defining an axial direction along a length of the shaft; generating an induced current in the shaft using a first inductive probe; measuring the circulating current using a second inductive probe, the first and second inductive probes being inductively coupled to the shaft at respective probe locations, the respective probe locations being spaced apart along the shaft; and A vibration signal is acquired in response to sensing vibration while measuring the circulating current, wherein the vibration signal is provided by at least one vibration sensor disposed at the first support.

11. The method according to claim 10, comprising: The shaft is rotated at a selected shaft speed while the electrical load is on.

12. The method of claim 10 or 11, wherein generating an inducing current in the shaft comprises: The input is a pulse current characterized by a pulse frequency.

13. The method of claim 12, wherein the pulse frequency is based on an estimated number of discharges at the bearing under actual use conditions.

14. The method of any one of claims 10 to 13, wherein the axial mechanical load is applied to an inner ring of the bearing, and wherein the first support is coupled to an outer ring of the bearing.

15. The method according to any one of claims 10 to 14, further comprising heating the bearing to a predetermined temperature.

16. The method of any one of claims 10 to 15, further comprising determining a health state of the bearing based on a comparison of the vibration signals acquired over a period of time.

17. The method of claim 16, wherein the health status of the bearing is based on a change in a standard deviation of the vibration signal over the time period.

18. The method of claim 16 or 17, further comprising determining expected bearing degradation over a service life based on the health of the bearing after an accelerated testing period, and wherein the accelerated testing period is shorter than the service life.

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