Fatigue degree calculation system

Abstract

To provide a fatigue degree calculation system capable of calculating fatigue degree more properly.SOLUTION: The fatigue degree calculation system calculates the degree of fatigue as the degree of fatigue caused by stress repeatedly applied with changes in the rotational speed of rotating equipment. The fatigue degree calculation system sets the stress amplitude and the average stress based on time series data of rotation speed and calculates the degree of fatigue using the frequency distribution of the post-movement amplitude as the stress component consisting of the set stress amplitude and average stress in the fatigue limit diagram is moved parallel to the specified fatigue limit line and on the complete oscillating line and the stress component after movement. As a result, the degree of fatigue can be calculated more appropriately.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a fatigue level calculation system, and more particularly to a fatigue level calculation system that calculates a fatigue level as a degree of fatigue caused by stress accompanying changes in the rotation speed of a rotating device. [Background technology]

[0002] Conventionally, as a fatigue degree calculation system for calculating the fatigue degree of this type of rotating equipment, one has been proposed that calculates the fatigue degree (fatigue level) of a driving force transmission device that transmits driving force from an engine to driving wheels (see, for example, Patent Document 1). In this system, the fatigue degree of the driving force transmission device is calculated according to Miner's law using the actual input torque to the driving force transmission device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-128149 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, in rotating equipment such as motors, it is recognized that calculating the degree of fatigue caused by repeated stresses as the rotation speed of the rotating equipment changes is an important issue. It is conceivable to apply the above-mentioned fatigue degree calculation system to calculate the degree of fatigue of such rotating equipment. However, the above-mentioned fatigue degree calculation system does not take into account the effect of the mean stress on the degree of fatigue, and therefore cannot calculate the degree of fatigue appropriately. On the other hand, if the degree of fatigue is calculated using the stress amplitude and the mean stress, the calculation of the degree of fatigue becomes complicated.

[0005] A main object of the fatigue level calculation system of the present invention is to more appropriately calculate a fatigue level. [Means for solving the problem]

[0006] The fatigue level calculation system of the present invention employs the following means to achieve the above-mentioned main object.

[0007] The fatigue level calculation system of the present invention comprises: A fatigue degree calculation system that calculates a fatigue degree as a degree of fatigue caused by a stress repeatedly applied in accordance with a change in the rotation speed of a rotating device, comprising: A stress amplitude and an average stress are set based on the time series data of the rotation speed, and the fatigue degree is calculated using a frequency distribution of a post-movement amplitude as a stress amplitude in a post-movement stress component obtained by moving a stress component consisting of the stress amplitude and the average stress set in a fatigue limit diagram parallel to a predetermined fatigue limit line and on a perfect single-sided line. The gist of the present invention is as follows.

[0008] In the fatigue degree calculation system of the present invention, the stress amplitude and the mean stress are set based on the time series data of the rotation speed of the rotating equipment. Then, the fatigue degree is calculated using the frequency distribution of the post-shift amplitude as the stress amplitude in the post-shift stress component obtained by moving the stress component consisting of the stress amplitude and the mean stress set in the fatigue limit diagram parallel to the predetermined fatigue limit line and onto the complete single-sided line. The reason for moving the stress component onto the complete single-sided line is that the force generated with the change in rotation of the rotating equipment is mainly centrifugal force, so that the stress becomes a positive value. Then, since the stress component is moved parallel to the predetermined fatigue limit line, the influence of fatigue due to the mean stress can be added to the post-shift amplitude. Since the fatigue degree is calculated using the post-shift amplitude that takes into account the influence of fatigue due to the mean stress in this way, the fatigue degree can be calculated more appropriately.

[0009] The fatigue degree calculation system of the present invention may include a voice output unit that outputs a voice, and may calculate, for each category of the post-movement amplitude, a frequency ratio as a ratio of the frequency of the post-movement amplitude of the category to the number of repetitions until the rotating equipment is damaged, and may calculate the remaining life as a value obtained by subtracting the sum of the frequency ratios for each category from a value of 1 as the fatigue degree, and may issue an alarm from the voice output unit when the remaining life falls below a predetermined value. In this way, the user can be made aware that the remaining life is less than the predetermined value. Here, the "predetermined value" may be a threshold value for determining whether the life of the rotating equipment is shortening or not.

[0010] In the fatigue degree calculation system of the present invention, the predetermined fatigue limit line may be a modified Goodman line. [Brief description of the drawings]

[0011] [Figure 1] 1 is a diagram showing an outline of the configuration of an electric vehicle 20 equipped with a fatigue level calculation system according to an embodiment of the present invention. [Diagram 2] 2 is a schematic cross-sectional view showing an outline of a cross section of a main part of a rotor of a motor 32. FIG. [Diagram 3] 4 is a flowchart showing an example of a first processing routine executed by a vehicle ECU 60. [Figure 4] 6 is a flowchart showing an example of a second processing routine executed by a vehicle ECU 60. [Diagram 5] 1 shows an example of time-series data of square values ​​Sqrω for a predetermined time tref stored in a RAM. [Figure 6] 6 is an explanatory diagram showing an example of a waveform having peaks at the maximum and minimum values ​​of the time-series data illustrated in FIG. 5. [Figure 7] FIG. 2 is an explanatory diagram showing an example of a stress amplitude Sai, a mean stress Smi, and a number of cycles Nci. [Figure 8] FIG. 2 is an explanatory diagram showing an example of a state in which a stress component Pi is moved in a fatigue limit diagram. [Figure 9]FIG. 11 is an explanatory diagram showing an example of a post-movement amplitude Shi. [Figure 10] FIG. 11 is an explanatory diagram showing an example of a change in stress over time before and after a stress component Pi is moved onto a completely single-sided line. [Figure 11] 13 is an explanatory diagram for explaining an outline of a force F acting on an electromagnetic steel plate 320 from a magnet M of a rotor as a motor 32 rotates. FIG. [Figure 12] FIG. 13 is an explanatory diagram showing an example of a frequency distribution of a post-movement amplitude Shi. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Next, a mode for carrying out the present invention will be described using examples. EXAMPLES

[0013] 1 is a schematic diagram showing the configuration of an electric vehicle 20 equipped with a fatigue level calculation system according to an embodiment of the present invention. As shown in the figure, the electric vehicle 20 of the embodiment includes a motor 32 for driving, an inverter 34, a battery 40, and a vehicle electronic control unit (hereinafter referred to as "vehicle ECU") 60. The vehicle ECU 60 mainly corresponds to the fatigue level calculation system of the embodiment.

[0014] The motor 32 is configured as, for example, a synchronous generator motor, and a rotor of the motor 32 is connected to a drive shaft 26 which is connected to the drive wheels 22 via a differential gear 24. Fig. 2 is a schematic cross-sectional view showing an outline of a cross section of a main part of the rotor of the motor 32. The rotor of the motor 32 is made by laminating a plurality of electromagnetic steel plates 320, and magnets M are inserted into a plurality of slots S as gaps formed inside.

[0015] The inverter 34 is connected to the motor 32 and also to a power line 36. The motor 32 is rotationally driven by the vehicle ECU 60 controlling the switching of a plurality of switching elements (not shown) of the inverter 34.

[0016] The battery 40 is configured as, for example, a lithium ion secondary battery, and is connected to the power line 36 .

[0017] Although not shown, the vehicle ECU 60 includes a microprocessor having a CPU, ROM, RAM, flash memory, input / output ports, and communication ports.

[0018] Signals from various sensors are input to the vehicle ECU 60 via input ports. Examples of signals input to the vehicle ECU 60 include the rotational position θm of the rotor of the motor 32 from a rotational position sensor (e.g., resolver) 32a that detects the rotational position of the rotor of the motor 32, the voltage Vb of the battery 40 from a voltage sensor 40a attached between the terminals of the battery 40, and the current Ib of the battery 40 from a current sensor 40b attached to the output terminal of the battery 40. Note that since the vehicle ECU 60 also functions as a drive control device for the vehicle, the vehicle ECU 60 can also receive the shift position from a shift position sensor that detects the operation position of a shift lever, the accelerator opening from an accelerator pedal position sensor that detects the amount of depression of the accelerator pedal, the brake pedal position BP from a brake pedal position sensor that detects the amount of depression of the brake pedal, and the vehicle speed from a vehicle speed sensor.

[0019] Various control signals are output via the output port from the vehicle ECU 60. Examples of the signals output from the vehicle ECU 60 include control signals to a plurality of switching elements of the inverter 34 and control signals to a speaker 62 that outputs sound.

[0020] In the electric vehicle 20 of this embodiment configured as described above, the inverter 34 is controlled so that the electric vehicle 20 runs on power from the motor 32 .

[0021] Next, the operation of the electric vehicle 20 of the embodiment thus configured, particularly the operation when calculating the remaining life (fatigue level) of the motor 32, will be described. FIG. 3 is a flowchart showing an example of a first processing routine executed by the vehicle ECU 60. The first processing routine is executed every predetermined time titr (e.g., every few msec) when the motor 32 is driven. FIG. 4 is a flowchart showing an example of a second processing routine executed by the vehicle ECU 60. The second processing routine is executed in parallel with the first processing routine every predetermined time titr when the motor 32 is driven. In the embodiment, the first processing routine will be described first, followed by the second processing routine.

[0022] First, the first processing routine will be described. When the first processing routine is executed, the CPU of the vehicle ECU 60 executes a process of inputting the rotational position θm of the rotor of the motor 32 from the rotational position sensor 32a (step S100). Then, using the input rotational position θm, a square value Sqrω (=ω 2 ), and stores the calculated square value Sqrω in the RAM (step S110), and ends the first processing routine. In formula (1), "previous θm" is the rotational position θm input in step S100 when the first processing routine was executed the previous time. When the electric vehicle 20 is started up and the first processing is executed for the first time, the previous θm is set to a value of 0. In step S110, if the square value Sqrω has already been stored in the RAM, the square value Sqrω already stored in the RAM is not overwritten, and the square value Sqrω calculated this time is stored in the RAM. Therefore, time-series data of the square value Sqrω is accumulated in the RAM until it is cleared in the second processing routine, as described below.

[0023] Sqrω=[(θm-previous θm) / tref ] 2 (1)

[0024] Next, the second processing routine will be described. When the second processing routine is executed, the CPU of the vehicle ECU 60 judges whether the number Nω of data of the square value Sqrω stored in the RAM is equal to or greater than a threshold value Nth (step S200). The threshold value Nth is a threshold value for judging whether data of the square value Sqrω for a predetermined time tref is stored in the RAM. The predetermined time tref is set based on a predetermined time titr as a repetition time of the first processing routine, as a time at which the ratio of the storage capacity used for storing the square value Sqrω to the total storage capacity of the RAM becomes large (for example, the time at which the ratio of the storage capacity used for storing the rotation speed ω to the total storage capacity of the RAM becomes 0.01, 0.1, etc.).

[0025] Next, the stress amplitude Sai (i=1, 2, . . . , n), the average stress Smi (i=1, 2, . . . , n), and the number of cycles Nci (i=1, 2, . . . , n) for each peak are set by rainflow processing from the time series data of the square value Sqrω of the rotation speed ω for the predetermined time tref stored in the RAM (step S210). FIG. 5 shows an example of the time series data of the square value Sqrω for the predetermined time tref stored in the RAM. In step S210, first, a waveform is generated whose peaks are the maximum and minimum values ​​of the time series data exemplified in FIG. 5. FIG. 6 shows an example of a waveform whose peaks are the maximum and minimum values ​​of the time series data exemplified in FIG. 5. Then, the stress amplitude Sai, the average stress Smi, and the number of cycles Nci (corresponding to the number of occurrences (frequency) for each stress amplitude Sai) are set for the waveform shown in FIG. 6 by rainflow processing. Here, "i" is an integer equal to or greater than 1 and equal to or less than the number n of the stress amplitude Sai, the mean stress Smi, and the number of cycles Nci set by the rainflow processing. Fig. 7 shows an example of the stress amplitude Sai, the mean stress Smi, and the number of cycles Nci.

[0026] Next, using the following formula (2), in the fatigue limit diagram, the stress component Pi (i=1, 2, . . . , n) consisting of the stress amplitude Sai and the average stress Smi is moved parallel to the modified Goodman line and onto the complete single-sided line, and the post-movement amplitude Shi (i=1, 2, . . . , n) is calculated as the stress amplitude at the post-movement stress component Pit (step S220). In formula (2), "SB" is the tensile strength and is a constant determined by the material of the electromagnetic steel sheet 320 of the rotor of the motor 32. "Swb" is the double-sided fatigue limit and is a constant determined by the material of the electromagnetic steel sheet 320. FIG. 8 is an explanatory diagram showing an example of the state in which the stress component Pi is moved in the fatigue limit diagram. In the figure, the white circle is the stress component Pi, and the arrow extending from the white circle is an example of the direction in which the stress component Pi moves. FIG. 9 shows an example of the post-movement amplitude Shi.

[0027]

number

[0028] Here, the reason for moving the stress component Pi (i=1, 2, . . . , n) parallel to the modified Goodman line and onto the perfect one-way swing line will be explained. The reason for moving the stress component Pi parallel to the modified Goodman line is to add the effect of fatigue due to the mean stress Smi to the post-movement amplitude Shi in order to calculate the remaining life Rl from only the post-movement amplitude Shi, as will be described later.

[0029] The reason for moving the stress component Pi onto the complete single-sided swing line is as follows. FIG. 10 is an explanatory diagram showing an example of the time change of stress before and after moving the stress component Pi onto the complete single-sided swing line. The solid line shows an example of the time change of stress before moving the stress component Pi onto the complete single-sided swing line. The dashed line shows an example of the time change of stress after moving the stress component Pi onto the complete single-sided swing line. By moving the stress component Pi onto the complete single-sided swing line, the minimum value of the average stress becomes 0, and the remaining life Rl can be calculated only from the stress amplitude as described later. FIG. 11 is an explanatory diagram for explaining an outline of the force F acting from the magnet M of the rotor to the electromagnetic steel sheet 320 as the motor 32 rotates. In the figure, the black arrow shows an example of the rotation direction of the motor 32. The white arrow shows an example of the direction of the force F. The force F is mainly a centrifugal force acting on the magnet M due to the rotation of the magnet M of the rotor together with the motor 32. This centrifugal force generates stress in the electromagnetic steel sheet 320, and this stress accumulates fatigue in the electromagnetic steel sheet 320, i.e., the motor 32. This centrifugal force is the product of the mass of the magnet M, the distance from the rotation center of the rotor to the center of gravity of the magnet M, and the square of the rotation speed of the magnet M (the square value Sqrω of the rotation speed ω of the motor 32), and is a positive value. Therefore, the reason why the stress component Pi is moved onto the perfect single-sided swing line is to make it possible to calculate the remaining life Rl only from the post-movement amplitude Shi while taking into account the mechanism of such stress generation. In this way, by moving the stress component Pi (i=1, 2, . . . , n) parallel to the modified Goodman line and onto the perfect single-sided swing line, it becomes possible to more appropriately calculate the remaining life Rl only from the post-movement amplitude Shi.

[0030] Once the post-movement amplitude Shi is calculated in this manner, a frequency distribution of the post-movement amplitude Shi is created (step S230). Fig. 12 is an explanatory diagram showing an example of the frequency distribution of the post-movement amplitude Shi. In the frequency distribution, the post-movement amplitude Shi is divided into a plurality of sections Tj (j = 1, 2,..., m) of a predetermined width ΔSh, and the sum of the number of cycles Nci corresponding to the post-movement amplitude Shi included in each section Tj is set as the frequency Nj. In the figure, "Nfi" is a value determined in advance by experiment, analysis, etc. as the number of repetitions (limit frequency) at which the motor 32 will break when the motor 32 is repeatedly subjected to stress of the stress amplitude included in each section Tj.

[0031] Then, for each division of the post-movement amplitude Shi, a frequency ratio (Nj / Nfj) is calculated as a ratio of the frequency Nj ​​in the section Tj to the limit frequency Nfj as the number of repetitions until the motor 32 breaks, and the remaining life Rl of the motor 32 is calculated as a fatigue degree by subtracting the sum of the frequency ratios (Nj / Nfj) for each section Tj from the value 1 using the following formula (3) (step S240), and the data that has been subjected to rainflow processing among the square value Sqrω of the rotation speed ω stored in the RAM is cleared from the RAM (step S250), and the second processing routine is terminated. In this way, the remaining life Rl is calculated as a fatigue degree using the post-movement amplitude Shi that takes into account the influence of fatigue due to the average stress, so that the remaining life Rl can be calculated more appropriately. Also, since the remaining life Rl of the motor 32 can be calculated from the frequency Nj ​​and the limit frequency Nfj, the remaining life Rl can be calculated more simply than when the remaining life is calculated using the stress amplitude Sai and the average stress Smi.

[0032] Rl=1-(N1 / Nf1+N2 / Nf2+N3 / Nf3+ +Nj / Nfj) (3)

[0033] When the remaining life Rl is calculated in this manner, the vehicle ECU 60 compares the remaining life Rl with the judgment value Rj, and when the remaining life Rl falls below the judgment value Rj, an alarm is issued from the speaker 62 indicating that the remaining life Rl of the motor 32 is short and urging the user to have the motor 32 inspected. This makes it possible to inform the user of the electric vehicle 20 that the remaining life Rl of the motor 32 is short and urge the user to have the motor inspected.

[0034] According to the electric vehicle 20 equipped with the fatigue degree calculation system of the embodiment described above, the stress amplitude Sai and the mean stress Smi are set based on the time-series data of the rotational speed ω of the motor 32, and the remaining life Rl is calculated using the frequency distribution of the post-movement amplitude Shi, which is the stress amplitude at the post-movement stress component Pit that has been moved parallel to the modified Goodman line and onto the perfect single-sided line, after the stress component Pi, consisting of the stress amplitude Sai and the mean stress Smi set in the fatigue limit diagram, has been moved. This makes it possible to calculate the remaining life Rl more appropriately.

[0035] In addition, for each division of the post-movement amplitude Shi, a frequency ratio (Nj / Nfj) is calculated as the ratio of the frequency Nj ​​in the section Tj to the limit frequency Nfj, which is the number of repetitions at which the motor 32 is damaged. The remaining life Rl is calculated as the value obtained by subtracting the sum of the frequency ratios (Nj / Nfj) for each section Tj from the value 1, and is used as the degree of fatigue. When the remaining life Rl falls below the judgment value Rj, an alarm is sounded from the speaker 62 to notify the user of the electric vehicle 20 that the remaining life Rl of the motor 32 is short, and to encourage the user to have the motor 32 inspected.

[0036] In the electric vehicle 20 equipped with the fatigue degree calculation system of the embodiment, the stress component Pi, which is composed of the stress amplitude Sai and the mean stress Smi set in the fatigue limit diagram, is moved parallel to the modified Goodman line. However, the stress component Pi may be moved parallel to a fatigue limit line other than the modified Goodman line, such as the Goodman line, the Gerber line, or the Soderberg line.

[0037] In the electric vehicle 20 equipped with the fatigue degree calculation system of the embodiment, the remaining life span Rl is calculated as the fatigue degree. However, instead of the remaining life span Rl, the damage degree D, which can be calculated by the following formula (4), may be calculated as the fatigue degree. In this case, when the damage degree D becomes equal to or greater than a predetermined judgment value Dj, a sound to notify that effect may be output from the speaker 62.

[0038] D=N1 / Nf1+N2 / Nf2+N3 / Nf3+···+Nj / Nfj···(4)

[0039] In the electric vehicle 20 equipped with the fatigue degree calculation system of the embodiment, when the remaining lifespan Rl is equal to or less than the judgment value Rj, a sound is output from the speaker 62 stating that the remaining lifespan Rl of the motor 32 is short and urging inspection. However, if the electric vehicle 20 is equipped with a display, a message to the effect that the remaining lifespan Rl of the motor 32 is short may be displayed on the display. Also, such sound output or message display may not be required.

[0040] In the electric vehicle 20 equipped with the fatigue degree calculation system of the embodiment, the vehicle ECU 60 as a single device calculates the remaining life Rl. However, if the electric vehicle 20 is equipped with multiple calculation devices, the multiple calculation devices may cooperate to calculate the remaining life Rl. Also, if the vehicle ECU 60 of the electric vehicle 20 is capable of exchanging data with a server, part of the processing of the first processing routine and the second processing routine may be performed by the server.

[0041] In the embodiment, the fatigue degree calculation system of the present invention is illustrated as being applied to an electric vehicle 20. However, the present invention may also be applied to other devices equipped with a motor, such as an electric drill, a cyclone type vacuum cleaner, or a washing machine. Also, the present invention may be applied to rotating equipment other than a motor that does not have a motor but rotates when operated.

[0042] The relationship between the main elements of the embodiment and the main elements of the invention described in the Summary of the Invention will be described below. In the embodiment, the vehicle ECU 60 corresponds to the "fatigue level calculation system."

[0043] The correspondence between the main elements of the Examples and the main elements of the invention described in the Summary of the Problem column does not limit the elements of the invention described in the Summary of the Problem column, since the Examples are examples for specifically explaining the mode for implementing the invention described in the Summary of the Problem column. In other words, the interpretation of the invention described in the Summary of the Problem column should be based on the description in that column, and the Examples are merely a specific example of the invention described in the Summary of the Problem column.

[0044] Although the form for carrying out the present invention has been described above using examples, the present invention is not limited to these examples in any way, and it goes without saying that the present invention can be carried out in various forms without departing from the scope of the gist of the present invention. [Industrial Applicability]

[0045] The present invention can be used in the manufacturing industry of fatigue degree calculation systems. [Explanation of symbols]

[0046] 20 electric vehicle, 22 drive wheel, 24 differential gear, 26 drive shaft, 32 motor, 34 inverter, 36 power line, 40 battery, 40a voltage sensor, 40b current sensor, 60 vehicle ECU, 62 speaker, 320 electromagnetic steel sheet, M magnet, S slot.

Claims

1. A fatigue degree calculation system that calculates a fatigue degree as a degree of fatigue caused by a stress repeatedly applied in accordance with a change in the rotation speed of a rotating device, comprising: A stress amplitude and an average stress are set based on the time series data of the rotation speed, and the fatigue degree is calculated using a frequency distribution of a post-movement amplitude as a stress amplitude in a post-movement stress component obtained by moving a stress component consisting of the stress amplitude and the average stress set in a fatigue limit diagram parallel to a predetermined fatigue limit line and on a perfect single-sided line. Fatigue level calculation system.

2. The fatigue degree calculation system according to claim 1, Audio output section for outputting audio Equipped with calculating a frequency ratio for each category of the post-movement amplitude as a ratio of a frequency of the post-movement amplitude for the category to a number of repetitions until the rotating device is damaged; A remaining life is calculated as the fatigue degree by subtracting the sum of the frequency ratios for each of the categories from a value of 1; When the remaining life falls below a predetermined value, an alarm is issued from the audio output unit. Fatigue level calculation system.

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