Joint reducer failure data preprocessing method for industrial robot

Abstract

The present application relates to the technical field of industrial robot fault diagnosis, and particularly relates to a joint reducer fault data preprocessing method for industrial robots, which searches for reducer fault characteristic information modulated by rotating speed in the frequency domain distribution of current signals, extracts the reducer fault characteristic information based on the difference between the reducer fault characteristic frequency and the rotating speed frequency and the amplitude relationship before and after modulation, and obtains the time domain waveform of the reducer fault current signal without rotating speed modulation interference, which eliminates the interference of the rotating speed signal and provides data support and technical support for subsequent accurate extraction of reducer fault characteristics based on current signals.

Description

Technical Field

[0001] This invention relates to the field of industrial robot fault diagnosis technology, and in particular to a method for preprocessing fault data of joint reducers for industrial robots. Background Technology

[0002] Fault diagnosis of joint reducers for industrial robots based on current signals can be completed simply by having Hall sensors directly collect the input current of the drive motor. Compared with other signal types (such as torque, vibration, strain, etc.), no additional sensor installation space is required. In addition, besides being low-cost and requiring no complex equipment, current data is usually used as a data backup for industrial robot users and is uploaded to the cloud for industrial robot equipment status monitoring and fault diagnosis.

[0003] Current methods for diagnosing reducer faults based on current signals mainly involve three steps. First, the current signal is preprocessed, including filtering and data alignment. Second, fault features of the reducer are extracted from the current signal. Generally, the extracted features are mainly derived from time-domain waveform features and frequency distribution characteristics. Finally, machine learning methods are used to train and test the reducer fault identification model.

[0004] While current signals contain characteristic information about reducer faults, this information is modulated by rotational speed. Typically, the fault frequency of a reducer is much higher than its rotational speed, and due to the difficulty in fine-grained modeling of reducers, this fault frequency is often unknown. This makes it difficult to accurately demodulate the fault characteristic frequency using traditional demodulation methods combined with low-pass and band-pass filters. Furthermore, under the influence of rotational speed modulation interference, the current signal waveform for the same reducer fault type differs under different operating speeds, severely impacting the accurate extraction of fault characteristics. This is a key reason why current data-driven technologies struggle to achieve accurate reducer fault identification. Summary of the Invention

[0005] In view of this, the purpose of this invention is to propose a method for preprocessing fault data of joint reducers for industrial robots, so as to solve the problem of insufficient accuracy in extracting fault features of reducers.

[0006] To achieve the above objectives, the present invention provides a method for preprocessing fault data of a joint reducer for industrial robots, comprising:

[0007] S1. Perform spectral analysis on the current signal, extract the position of the frequency corresponding to the maximum amplitude in the spectrum, and obtain the current frequency modulation frequency.

[0008] S2. Set a certain range of allowable error. The relevant parameters are assigned values ​​u=2, v=1, w=1, i=1. The maximum value i of the cyclic parameter that meets the allowable error is calculated based on the allowable error and the current frequency modulation frequency. max w is used to accumulate the number of original fault features, i is the search parameter, and based on the modulation and demodulation relationship, it is assumed that u is the multiple relationship between the modulated feature and the feature amplitude of the original signal, and v is the difference between a pair of modulation feature frequencies and the feature frequency of the original signal and the current modulation frequency. The multiple relationship between them makes:

[0009]

[0010]

[0011] f n f is the characteristic frequency of the reducer fault. * The frequency after the characteristic frequency of the reducer fault is modulated;

[0012] S3. Determine the modulation frequency f i * Corresponding amplitude Does it meet the requirements? If the condition is met, the frequency is considered to be caused by noise interference, and the process proceeds to step S10. If the condition is not met, the process proceeds to step S4. i * With another modulation frequency All are the original characteristic frequency f of the reducer n1 The corresponding modulation frequency pair;

[0013] S4. According to the modulation frequency f i * and current frequency f c * calculate Determine f i * and Corresponding amplitude and If the following conditions are met, proceed to step S5; otherwise, proceed to step S6.

[0014]

[0015] S5. Calculate the characteristic frequency f n_w and the corresponding amplitude A n_w Let w = w + 1, then jump to step S10;

[0016] S6. Calculate the modulation frequency Determine f i * , and Does the corresponding amplitude satisfy the conditions of the following formula? If it does, proceed to step S7; otherwise, jump to step S8. and It is the original characteristic frequency f of the reducer n2 Corresponding modulation frequency pairs:

[0017]

[0018] S7. Calculate the characteristic frequency f n_w and f n_w+1 and the corresponding amplitude A n_w and A n_w+1 Let w = w + 2, then go to step 10;

[0019] S8, Calculate f l * And determine the modulation frequency f i * , f l * And whether the corresponding amplitude satisfies the conditions of the following formula. If it does, proceed to step S9; otherwise, proceed to step S10, where... and f l * The original characteristic frequency f of the reducer n3 The corresponding modulation frequency pair;

[0020] S9. Calculate the characteristic frequency f n_w f n_w+1 and f n_w+2 and the corresponding amplitude A n_w A n_w+1 and A n_w+2 After executing w = w + 3, proceed to step S10;

[0021] S10. Determine if the search parameter i has reached its maximum value. max If yes, then let i = i + 1 and return to step S3; otherwise, go to step S11.

[0022] S11. Determine if the current signal is demodulated based on whether v equals 1. If yes, proceed to step S12; otherwise, demodulate the current signal to obtain the demodulated signal y*, and perform spectrum analysis on it. Then, determine the demodulation frequency and the current modulation frequency f in the demodulated signal. c * Based on the relationship, adjust parameters u and v to twice their original values ​​respectively, and return to step S3 to extract the original characteristic frequency of the reducer under the modulation signal;

[0023] S12, Determine f n_p and f n_q and amplitude A n_p and An_q If the following formula condition is met, then it is considered that there is a pair of common characteristic frequencies f between the modulating signal and the demodulated signal. n_t Proceed to step S13 for calculation; otherwise, proceed to step S14.

[0024] f n_p =f n_q

[0025] |A n_p -A n_q |≤A th ;

[0026] The original characteristic frequencies of the reducer extracted from the current signal and the demodulated signal are stored in arrays P and Q, respectively. n_p and f n_q These are the p-th and q-th characteristic frequencies in P and Q, respectively, with corresponding amplitudes of A. n_p and A n_q ;

[0027] S13. Calculate the common characteristic frequency f n_t The corresponding amplitude is A n_t , where t is used to accumulate f w_t The number of characteristic frequencies with the same internal frequency and very similar amplitude is determined by setting t = t + 1, and proceeding to step S14.

[0028] S14. Determine if q is equal to w. If yes, proceed to step S15. Otherwise, perform q = q + 1 and return to step S12.

[0029] S15. Execute p = p + 1, and determine f. n_p and f n_p-1 Does it satisfy the following relationship?

[0030] f n_p <f n_p-1

[0031]

[0032] If yes, proceed to the next step; otherwise, return to step S13.

[0033] S16, filter the f n_t and A n_t Perform an inverse Fourier transform to obtain a current signal that is unaffected by speed modulation.

[0034] Preferably, in step S4, the calculation is performed. The formula is:

[0035]

[0036] Preferably, in step S5, the characteristic frequency f is calculated.n_w and amplitude A n_w The formula is:

[0037]

[0038]

[0039] Preferably, in step S6, f is calculated. k * The formula is:

[0040]

[0041] Preferably, in step S7, the characteristic frequency f is calculated. n_w and f n_w+1 and amplitude A n_w and A n_w+1 The formula is:

[0042]

[0043]

[0044]

[0045]

[0046] Preferably, in step S8, f is calculated. l * The formula is:

[0047]

[0048] Preferably, in step S9, the characteristic frequency f is calculated. n_w f n_w+1 and f n_w+2 and amplitude A n_w A n_w+1 and A n_w+2 The formula is:

[0049] f n1 =f i * +v·f c *

[0050]

[0051]

[0052]

[0053]

[0054]

[0055] Preferably, in step S11, the formula for calculating the demodulated signal y* is:

[0056]

[0057] Preferably, in step S13, the common characteristic frequency f is calculated. n_t and corresponding amplitude A n_t The formula is:

[0058] f n_t =f n_p

[0059]

[0060] The beneficial effects of this invention are as follows: To solve the problem of accurately extracting fault feature information of reducers and eliminate the influence of speed modulation interference, this invention proposes a preprocessing method for fault data of joint reducers used in industrial robots. By searching for reducer fault feature information modulated by speed in the frequency domain distribution of current signals, and based on the relationship between the reducer fault feature frequency and the speed frequency difference, as well as the amplitude relationship before and after modulation, the reducer fault feature information is extracted, and the time-domain waveform of the reducer fault current signal without speed modulation interference is obtained. This current time-domain waveform eliminates the interference of speed signals, providing data support and technical support for the subsequent accurate extraction of reducer fault features based on current signals. Attached Figure Description

[0061] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only for this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0062] Figure 1 This is a schematic diagram of the gearbox fault data preprocessing process according to an embodiment of the present invention. Detailed Implementation

[0063] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0064] It should be noted that, unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0065] Data-driven methods are currently the mainstream approach for fault diagnosis of joint reducers in industrial robots. However, in current signals, the characteristic frequencies of reducer faults are modulated by rotational speed, severely impacting the fault feature extraction process based on data-driven methods. This invention proposes a data preprocessing method for faults in joint reducers of industrial robots. Based on the relationship between reducer fault information and rotational speed modulation, it restores the fault characteristic signals of the reducer, eliminates rotational speed interference, and provides data support and technical assistance for accurate extraction of reducer fault features based on current signals.

[0066] During the preprocessing of reducer fault data, at the data sampling frequency f s Given a fixed data length, the data frequency resolution is determined. Furthermore, considering that the reducer rotates in a circular motion, the occurrence period of different fault types is directly related to the reducer's rotation angle. Based on the reducer mechanism, assuming the reducer input has a rotational speed n and a reduction ratio r, the number of sampling points N when the reducer output rotates through an angle θ can be calculated using the following formula, which is also the primary basis for selecting the data preprocessing window width.

[0067]

[0068] Although the current signal contains fault characteristic information of the reducer, it is modulated by the speed. Assume the fault characteristic frequency of the reducer is f. n In the current signal, the frequency used to drive the motor speed is f. c * The frequency of the reducer fault characteristic frequency after modulation is f. * Then the three have the following relationship:

[0069] f * =f n ±v·f c * (2)

[0070]

[0071] Among them, A * For frequency f * The corresponding amplitude, A n For frequency f n The corresponding amplitudes, u and v, take the values ​​of 2 and 1 for all formulas before demodulation.

[0072] Typically, the main energy in a current signal is used for speed modulation. Therefore, in the frequency domain of the current signal, the frequency component corresponding to the maximum amplitude is the current modulation frequency f. c * Therefore, based on the energy distribution in the frequency domain of the current signal, the rotational speed frequency in the current signal can be obtained first. and amplitude

[0073] Assume f i * , It is the original characteristic frequency f of the reducer n1 If a pair of characteristic modulation frequencies are given, then the frequency and amplitude should simultaneously satisfy the following conditions:

[0074]

[0075]

[0076] in, To account for the allowable error due to noise.

[0077] To further reduce noise interference, the present invention uses and The weighted average value is used as the original characteristic frequency f of the reducer. n1 Amplitude A n1 ,

[0078]

[0079]

[0080] Considering that the reducer has multiple original characteristic frequencies, the amplitudes of the original characteristic frequencies modulated by the speed may be superimposed. Assume f i * and It is the original characteristic frequency f of the reducer n1 A pair of characteristic modulation frequencies, and and It is the original characteristic frequency f of the reducer n2 A pair of characteristic modulation frequencies, then The common frequency of the two, its amplitude If an overlapping relationship exists, then in addition to satisfying formula (4), the following conditions must also be met:

[0081]

[0082]

[0083] in, for The corresponding amplitude.

[0084] In this case, the original characteristic frequency and amplitude (f) of the reducer n1 The calculation is performed according to formula (6) as follows:

[0085]

[0086] Considering the superposition of amplitudes after the three original characteristic frequencies of the reducer are modulated, assume f i * and and and and f l * These are the original characteristic frequencies f of the reducer. n1 f n2 and f n3 The corresponding modulation frequency pair, f n1 and f n2 The modulated signal has a common frequency characteristic. f n2 and f n3 The modulated signal has a common frequency characteristic. and The corresponding amplitudes at each point are superimposed, and should simultaneously satisfy formulas (4), (8), and the following condition.

[0087]

[0088]

[0089] in, f l * The corresponding amplitude.

[0090] At this point, the original characteristic frequency and amplitude (f) of the reducer n1 and f n2 The calculations are performed according to equations (6) and (10) respectively, as follows:

[0091]

[0092]

[0093]

[0094]

[0095] The superposition of amplitudes after modulation of the original characteristic frequency of the reducer is rare in actual engineering and will not be considered in this invention.

[0096] To avoid the problem of incorrect or missing extraction of the original characteristic frequency of the reducer in the above extraction method, the present invention will demodulate the original acquired signal according to formula (19), and extract the original characteristic frequency and amplitude of the reducer for the second time according to the above method. At this time, u and v involved in the above-mentioned method should be set to 4 and 2 respectively. By comparing whether there is an equivalent relationship between the original characteristic frequency and amplitude of the reducer extracted before and after demodulation, the final original characteristic frequency and amplitude of the reducer can be determined.

[0097]

[0098] Assuming the original characteristic frequencies of the reducer extracted from the current signal and demodulated signal are stored in arrays P and Q respectively, f n_p and f n_q These are the p-th and q-th characteristic frequencies in P and Q, respectively, with corresponding amplitudes of A. n_p and A n_q If the following conditions are met, then the characteristic frequencies extracted from the current signal and the demodulated signal are considered to have a common frequency.

[0099] f n_p =f n_q (20)

[0100] |A n_p -A n_q |≤A th (twenty one)

[0101] The final characteristic frequency f of the reducer n and amplitude A n Determined according to the following formula,

[0102] f n_t =f n_p (twenty two)

[0103]

[0104] After determining the original characteristic frequency and amplitude of the reducer, an inverse Fourier transform is applied to the original characteristic frequency and amplitude to obtain the time-domain waveform of the reducer fault current signal that eliminates speed modulation interference.

[0105] The specific process is as follows: Figure 1 As shown.

[0106] Based on this, the preprocessing method for fault data of joint reducers for industrial robots proposed in this invention is carried out according to the following steps.

[0107] Step 1,

[0108] Perform spectral analysis on the current signal y, and extract the frequency corresponding to the maximum amplitude within the spectrum. This frequency is the current frequency modulation frequency f. c * .

[0109] Step 2,

[0110] Set a certain range of allowable error The relevant parameters are assigned values ​​u=2, v=1, w=1, i=1, and the maximum value i of the loop parameter is calculated. max =N, w is used to accumulate the number of original fault features, i is the search parameter, and based on the modulation and demodulation relationship, it is assumed that u is the multiple relationship between the modulated feature and the feature amplitude of the original signal, and v is the difference between a pair of modulation feature frequencies and the feature frequency of the original signal and the current modulation frequency f. c * The multiple relationship between them.

[0111] Step 3,

[0112] Determine the modulation frequency f i * Corresponding amplitude Does it meet the requirements? If yes, then it is considered to be a frequency formed by noise interference, and proceed directly to step 10; otherwise, proceed to step 4.

[0113] Step 4,

[0114] Calculate according to formula (4) And determine f i * , Does the corresponding amplitude satisfy the condition of formula (5)? ​​If yes, go to step 5; otherwise, go to step 6.

[0115] Step 5,

[0116] The characteristic frequency f is calculated using formulas (6) and (7). n_w and amplitude A n_w Let w = w + 1, then proceed to step 10.

[0117] Step 6,

[0118] Calculate according to formula (8) And determine f i * , and If the corresponding amplitude satisfies the condition of formula (9), proceed to step 7; otherwise, proceed to step 8.

[0119] Step 7,

[0120] The characteristic frequency f is calculated using formulas (6) and (10) to (12). n_w and f n_w+1 and amplitude A n_w and A n_w+1 Let w = w + 2, then go to step 10.

[0121] Step 8,

[0122] Calculate f according to formula (13) l * And determine the modulation frequency f i * , f l * And whether the corresponding amplitude satisfies the condition of formula (14). If yes, go to step 9; otherwise, go to step 10.

[0123] Step 9,

[0124] The characteristic frequency f is calculated using formulas (6), (8), and (15) to (18). n_w f n_w+1 and f n_w+2 and amplitude A n_w A n_w+1 and A n_w+2 After executing w = w + 3, proceed to step 10.

[0125] Step 10,

[0126] Determine if the search parameter i has reached its maximum value. max If yes, then let i = i + 1 and return to step 3; otherwise, go to step 11.

[0127] Step 11,

[0128] Determine whether the current signal is demodulated based on whether v equals 1. If yes, proceed to step 12; otherwise, demodulate the current signal according to formula (19) to obtain the demodulated signal y*, and perform spectrum analysis on it. Based on the demodulation frequency and the current modulation frequency in the demodulated signal... Based on the relationship, adjust parameters u and v to twice their original values ​​respectively, and return to step 3 to extract the original characteristic frequency of the reducer under the modulation signal.

[0129] Step 12,

[0130] Determine f n_p and f n_q and amplitude A n_p and A n_q If both conditions of formula (20) and formula (21) are met, then it is considered that a pair of common characteristic frequencies f exist between the modulating signal and the demodulated signal. n_t If not, proceed to step 13 for calculation; otherwise, proceed to step 14.

[0131] Step 13,

[0132] The common characteristic frequency f is calculated using formulas (22) and (23). n_t The corresponding amplitude is A n_t , where t is used to accumulate f w_t The number of characteristic frequencies with the same internal frequency and very similar amplitude is determined by setting t = t + 1, and then proceeding to step 14.

[0133] Fault features were found in both the modulated and demodulated signals. However, both signals possessed common and unique characteristics, which were stored in f. n_w In the context of f, as long as the common features are present... n_w There are two identical values ​​in f. Suppose 5 features are extracted from the modulated signal and 4 features are extracted from the demodulated signal. These extracted features will be stored in f. n_w In the middle, therefore f n_w There will be 9 characteristic frequencies, but some of these 9 characteristic frequencies are repeated and need to be further compared. Therefore, the f-value described in this embodiment was generated. n_p and f n_q f n_p and f n_q They represent f respectively n_w Two different frequencies were compared and filtered one by one, and the repetition frequency found was counted in f. n_t That is the frequency that is ultimately needed. Therefore, f n_t and f n_w The necessary relationship is f n_t <= f n_w / 2, so the maximum number of t in the above example will not exceed 4.

[0134] Step 14,

[0135] Determine if q is equal to w. If yes, proceed to step 15. If no, perform q = q + 1 and then return to step 12.

[0136] Step 15,

[0137] To prevent the shared characteristic frequency f from being executed, p = p + 1 is performed. n_t Perform secondary filtering at the same frequency to determine fn_p and f n_p-1 Does it satisfy the following relationship?

[0138] f n_p <f n_p-1 (twenty four)

[0139]

[0140] If yes, proceed to the next step; otherwise, return to step 13.

[0141] Step 16,

[0142] Filter the f n_t and A n_t Perform an inverse Fourier transform to obtain a current signal that is unaffected by speed modulation.

[0143] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity. Any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A method for preprocessing fault data of a joint reducer for an industrial robot, characterized in that, The method includes: S1. Perform spectral analysis on the current signal, extract the position of the frequency corresponding to the maximum amplitude in the spectrum, and obtain the current frequency modulation frequency. S2. Set a certain range of allowable error. The relevant parameters are assigned values ​​u=2, v=1, w=1, i=1. The maximum value i of the cyclic parameter that meets the allowable error is calculated based on the allowable error and the current frequency modulation frequency. max Where w is used to accumulate the number of original fault features, i is the search parameter, and based on the modulation and demodulation relationship, it is assumed that u is the multiple relationship between the modulated feature and the feature amplitude of the original signal, and v is the difference between a pair of modulation feature frequencies and the feature frequency of the original signal and the current modulation frequency. The multiple relationship between them makes: f n f is the characteristic frequency of the reducer fault. * The frequency after the characteristic frequency of the reducer fault is modulated; S3. Determine the modulation frequency f i * Corresponding amplitude Does it meet the requirements? If the condition is met, the frequency is considered to be caused by noise interference, and the process proceeds to step S10. If the condition is not met, the process proceeds to step S4. i * With another modulation frequency All are the original characteristic frequency f of the reducer n1 The corresponding modulation frequency pair; S4. According to the modulation frequency f i * and current frequency modulation calculate Determine f i * and Corresponding amplitude and If the following conditions are met, proceed to step S5; otherwise, proceed to step S6. S5. Calculate the characteristic frequency f n_w and the corresponding amplitude A n_w Let w = w + 1, then jump to step S10; S6. Calculate the modulation frequency Determine f i * , and Does the corresponding amplitude satisfy the conditions of the following formula? If it does, proceed to step S7; otherwise, jump to step S8. and It is the original characteristic frequency f of the reducer n2 Corresponding modulation frequency pairs: S7. Calculate the characteristic frequency f n_w and f n_w+1 and the corresponding amplitude A n_w and A n_w+1 Let w = w + 2, then go to step 10; S8, Calculate f l * And determine the modulation frequency f i * , f l * And whether the corresponding amplitude satisfies the following formula If the condition is met, proceed to step S9; otherwise, proceed to step S10. and f l * The original characteristic frequency f of the reducer n3 The corresponding modulation frequency pair; S9. Calculate the characteristic frequency f n_w f n_w+1 and f n_w+2 and the corresponding amplitude A n_w A n_w+1 and A n_w+2 After executing w = w + 3, proceed to step S10; S10. Determine if the search parameter i has reached its maximum value. max If yes, then let i = i + 1 and return to step S3; otherwise, go to step S11. S11. Determine if the current signal is demodulated based on whether v equals 1. If yes, proceed to step S12; otherwise, demodulate the current signal to obtain the demodulated signal y*, and perform spectrum analysis on it. Then, determine the demodulation frequency and the current modulation frequency based on the demodulation frequency in the demodulated signal. Based on the relationship, the parameters u and v are adjusted to twice their original values, and the process returns to step S3 to extract the original characteristic frequency of the reducer under the modulation signal. S12, Determine f n_p and f n_q and amplitude A n_p and A n_q If the following formula condition is met, then it is considered that there is a pair of common characteristic frequencies f between the modulating signal and the demodulated signal. n_t Proceed to step S13 for calculation; otherwise, proceed to step S14. f n_p =f n_q |A n_p -A n_q |≤A th ; The original characteristic frequencies of the reducer extracted from the current signal and the demodulated signal are stored in arrays P and Q, respectively. n_p and f n_q These are the p-th and q-th characteristic frequencies in P and Q, respectively, with corresponding amplitudes of A. n_p and A n_q ; S13. Calculate the common characteristic frequency f n_t The corresponding amplitude is A n_t t is used to accumulate f w_t The number of characteristic frequencies with the same internal frequency and very similar amplitude is determined by setting t = t + 1, and proceeding to step S14. S14. Determine if q is equal to w. If yes, proceed to step S15. Otherwise, perform q = q + 1 and return to step S12. S15. Execute p = p + 1, and determine f. n_p and f n_p-1 Does it satisfy the following relationship? f n_p <f n_p-1 If yes, proceed to the next step; otherwise, return to step S13. S16, filter the f n_t and A n_t Perform an inverse Fourier transform to obtain a current signal that is unaffected by speed modulation.

2. The method for preprocessing fault data of joint reducers for industrial robots according to claim 1, characterized in that, In step S4, calculate The formula is:

3. The method for preprocessing fault data of joint reducers for industrial robots according to claim 1, characterized in that, In step S5, the characteristic frequency f is calculated. n_w and amplitude A n_w The formula is:

4. The method for preprocessing fault data of joint reducers for industrial robots according to claim 1, characterized in that, In step S6, calculate The formula is:

5. The method for preprocessing fault data of joint reducers for industrial robots according to claim 1, characterized in that, In step S7, the characteristic frequency f is calculated. n_w and f n_w+1 and amplitude A n_w and A n_w+1 The formula is:

6. The method for preprocessing fault data of joint reducers for industrial robots according to claim 1, characterized in that, In step S8, calculate f l * The formula is:

7. The method for preprocessing fault data of joint reducers for industrial robots according to claim 1, characterized in that, In step S9, the characteristic frequency f is calculated. n_w f n_w+1 and f n_w+2 and amplitude A n_w A n_w+1 and A n_w+2 The formula is:

8. The method for preprocessing fault data of joint reducers for industrial robots according to claim 1, characterized in that, In step S11, the formula for calculating the demodulated signal y* is: Where n is the number of sampling points, y is the modulation signal, and f s The sampling rate.

9. The method for preprocessing fault data of joint reducers for industrial robots according to claim 1, characterized in that, In step S13, the common characteristic frequency f is calculated. n_t and corresponding amplitude A n_t The formula is: f n_t =f n_p

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