CN111975784B - Joint robot fault diagnosis method based on current and vibration signals - Google Patents
Joint robot fault diagnosis method based on current and vibration signals Download PDFInfo
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- CN111975784B CN111975784B CN202010918331.9A CN202010918331A CN111975784B CN 111975784 B CN111975784 B CN 111975784B CN 202010918331 A CN202010918331 A CN 202010918331A CN 111975784 B CN111975784 B CN 111975784B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
- B25J19/00—Accessories fitted to manipulators, e.g. for monitoring, for viewing; Safety devices combined with or specially adapted for use in connection with manipulators
- B25J19/0095—Means or methods for testing manipulators
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
- B25J9/00—Programme-controlled manipulators
- B25J9/16—Programme controls
- B25J9/1674—Programme controls characterised by safety, monitoring, diagnostic
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Abstract
The invention discloses a joint robot fault diagnosis method based on current and vibration signals, which comprises the steps of firstly picking up a motor current signal and a joint vibration signal of a joint to be researched of a robot; filtering the motor current signal to extract the instantaneous frequency of the joint motor current signal; calculating a real-time rotation angle of a joint motor shaft by using the instantaneous frequency extracted from the joint motor current signal; carrying out low-pass filtering processing on the vibration signal; determining the maximum order ratio range and equally dividing the rotation angle to obtain an equal-angle sampling time sequence and carrying out equal-angle sampling on the filtered vibration signal; finally, fourier transformation is carried out on the equal-angle sampling sequence of the vibration signals to obtain a robot joint vibration signal order spectrum and the robot joint vibration signal order spectrum is analyzed to realize robot joint fault diagnosis; the first-order frequency required by vibration order ratio analysis is extracted very conveniently and quickly, and vibration signal stabilization processing can be completed only by ensuring synchronous acquisition of vibration and current, so that robot joint fault diagnosis and state detection are completed.
Description
Technical Field
The invention relates to a joint robot fault diagnosis method based on current and vibration signals, and belongs to the technical field of state monitoring and fault diagnosis of industrial robots.
Background
The six-degree-of-freedom serial industrial robot has very wide application in industrial automation production, and parts abrasion caused by long-time operation and the occurrence of some emergencies can cause the robot to stop operating suddenly, so that the operation of a production line is damaged, and loss is caused to enterprises. The main devices of the robot joint are a servo motor and a reducer, and the monitoring of the robot and the traditional motor and reducer state monitoring method can be used for reference. The traditional motor state monitoring adopts the vibration signal spectrum analysis; for a six-degree-of-freedom series robot, a vibration signal is a typical non-stationary signal, and is generally firstly subjected to stationary processing, and the stationary processing mode generally adopts order ratio tracking. However, for the robot, the key phase pulse is difficult to obtain, the joint reducer has a complex structure, and the time-frequency instantaneous frequency extraction difficulty is high, so that the order ratio analysis from the two aspects has a plurality of problems, and the instantaneous frequency extracted by the current signals acquired synchronously replaces the time-frequency analysis to obtain the instantaneous conversion frequency relatively easily.
When the robot operates, the rotating speed of the robot is always in a changing state, and joint vibration signals of the robot are typical non-stationary signals; the robot joint structure is complex, so it is not practical to realize order tracking through hardware. Meanwhile, the joint servo motor encoder feedback pulse acquisition difficulty is high, and the cost is high. In addition, because the robot joint comprises a motor, a speed reducer and other parts, and all joints are in a connected state, the motor shaft frequency conversion in a frequency spectrum is not obvious when the robot joint vibrates signals, the extraction difficulty is high, an equiangular sampling sequence is difficult to obtain, and the order ratio analysis of the vibration signals is difficult. The robot joint motor current signal acquisition cost is low, the acquisition is convenient, and the order analysis by extracting the instantaneous frequency through the current signal has great significance.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a joint robot fault diagnosis method based on current and vibration signals, which does not need key phase signals and extraction of instantaneous frequency of the vibration signals, and can complete the order analysis of the vibration signals only by synchronously acquiring the current and the vibration signals and extracting the instantaneous frequency of the current signals.
The vibration signal order ratio analysis method based on the current comprises the following specific steps:
(1) Synchronously acquiring a motor current signal I (t) and a vibration signal S (t) of an ith joint of the robot in the process of rotating at any angle, wherein t is sampling time;
acquiring a motor current signal I (t) of an ith joint of the robot through a current sensor, and acquiring a vibration signal S (t) of the ith joint of the robot through an acceleration sensor;
the arbitrary angle refers to an arbitrary value within an angle range allowed by a joint, and the angle range is described on a robot specification or a robot demonstrator;
(2) Filtering and deburring the current signal I (t) by adopting a method of combining zero-phase filtering with singular value denoising to obtain a filtered current signal I 1 (t)；
(3) By the formula
Calculating the current signal I 1 (t) phase phi (t) by the formula
Calculating the current signal I 1 (t) instantaneous frequency f (t);
(4) By the formula
Wherein p is the number of pole pairs of the motor, the instantaneous rotating speed n (t) of the motor shaft is obtained by calculation, and the instantaneous rotating speed n (t) is obtained by a formula
Calculating to obtain an instantaneous rotation angle theta (t) of the motor shaft;
(5) By the formula
Calculating an equal-angle sampling interval delta theta; maximum order ratio v max Is an integer greater than or equal to 1;
(6) Sampling the instantaneous rotation angle theta (t) according to the equal-angle sampling interval delta theta obtained by calculation in the step (5) to obtain an equal-angle instantaneous rotation angle sequence theta 1 (t)；
(7) Cubic spline interpolation is carried out on the instantaneous corner theta (t) to obtain an equal-angle instantaneous corner sequence theta 1 (T) time series T;
(8) Carrying out low-pass filtering on the vibration signal S (t) acquired in the step (1) to obtain a filtered signal S 1 (t) for S 1 (t) intoPerforming cubic spline interpolation to obtain a vibration sequence S of the time sequence T 2 (t)；
(9) By the formula
Maximum order ratio v max Is an integer greater than or equal to 1; calculating a sequence of order ratios L, where n is the vibration sequence S 2 (t) length;
(10) For vibration sequence S 2 (t) performing Fast Fourier Transform (FFT) to obtain a ratio spectrum sequence S 3 (t)；
Taking the order ratio sequence L as an abscissa, and taking the order ratio spectrum sequence S 3 (t) drawing a scale spectrum with the first m values as vertical coordinates, wherein the m value is half of the length of the scale sequence L, and if L is an odd number, rounding the half of the length of the scale sequence L downwards;
and observing whether fault characteristic order ratios of all parts of the robot joint exist in order ratio components in the order ratio spectrum, if so, indicating that the parts have faults, and if not, indicating that the joints have no faults, thereby completing vibration signal order ratio analysis and realizing robot joint fault diagnosis and state detection.
The invention has the beneficial effects that:
1. the current signal instantaneous frequency extraction approach is superior to that of key phase pulse calculation and extraction from vibration signal time frequency spectrum;
2. the method can conveniently and quickly realize the order ratio analysis of the vibration signals;
3. the first-order frequency required by vibration order ratio analysis is extracted very conveniently and quickly, and vibration signal stabilization processing can be completed only by ensuring synchronous acquisition of vibration and current, so that joint state detection and fault diagnosis of the robot are realized.
Drawings
FIG. 1 is a schematic view of a robot configuration;
FIG. 2 is a schematic diagram showing the original waveform of the current signal I (t) in the state of 60 ° of articulation at 2 nd position;
FIG. 3 is a schematic diagram of the original waveform of the vibration signal S (t) in the state of 60 degrees of joint movement of FIG. 2;
FIG. 4 is a current signal I filtered from the current signal I (t) at 60 deg. of articulation 2 1 (t) a waveform schematic;
FIG. 5 is a current signal I after filtering of the current signal I (t) for the 60 deg. state of articulation 2 1 (t) a waveform diagram of the instantaneous frequency f (t);
fig. 6 is a waveform diagram of an instantaneous rotation angle θ (t) calculated by the instantaneous frequency f (t);
FIG. 7 is a sequence S after resampling of the vibration signal 2 (t) a waveform schematic;
FIG. 8 is a schematic diagram of a vibration signal scale spectrum;
in fig. 1: the system comprises a 1-1 st joint, a 2-2 nd joint, a 3-connecting arm I, a 4-3 rd joint, a 5-4 th joint, a 6-connecting arm II, a 7-5 th joint, an 8-6 th joint, a 9-electric cabinet, a 10-current sensor and an 11-acceleration sensor.
Detailed Description
The present invention is further illustrated by the following examples, but the scope of the invention is not limited to the above-described examples.
Example 1: the vibration signal order ratio analysis method based on the current comprises the following steps:
the robot is welded by adopting a Qianjiang QJR-1, and fig. 1 is a schematic structural diagram of the robot, which comprises a joint I1, a joint II 2, a connecting arm I3, a joint III 4, a joint IV 5, a connecting arm II 6, a joint V7, a joint VI 8, an electric cabinet 9, a current sensor 10 and an acceleration sensor 11; the implementation object is a joint II, the motion angle is 60 degrees, and the specific operation flow is as follows:
1. in the state that the second joint moves by 60 degrees, a current sensor is adopted to obtain a motor current signal I (t) of the second joint of the robot, as shown in fig. 2, an acceleration sensor 11 is adopted to obtain a vibration signal S (t) of the second joint, as shown in fig. 3, t is sampling time, an acquisition card is NI9234, acquisition software is SignalExpress, and sampling frequency is 25600Hz;
2. method for realizing zero-phase filtering and singular value denoising by utilizing matlab software to filter and dehaire current signal I (t)Performing thorn processing to obtain a filtered current signal I 1 (t); wherein the zero phase filter parameters are as follows: chebyshev type 1, 5-order, 0.2 cutoff low pass, 0.1 equal ripple; a time-frequency matrix used in the singular value denoising process is obtained through short-time Fourier transform, the length of a short-time Fourier transform window is 1024, and the step length is 128; the results are shown in FIG. 4;
the following calculation processes and output results are all completed in matlab software;
3. by the formula
Calculating the current signal I 1 (t) phase phi (t) by the formula
Calculating the current signal I 1 (t) instantaneous frequency f (t), the results are shown in FIG. 5;
4. by the formula
Wherein the number p of pole pairs of the motor is equal to 5, the instantaneous rotating speed n (t) of the motor shaft is obtained through calculation, and the instantaneous rotating speed n (t) is calculated through a formula
Calculating to obtain an instantaneous rotation angle theta (t), and the result is shown in fig. 6;
5. taking the maximum order ratio v max Equal to 30, by formula
Calculating equal-angle sampling interval delta theta to be equal to 6; sampling the instantaneous rotation angle theta (t) according to the equal-angle sampling interval of 6 degrees to obtain an equal-angle instantaneous rotation angle sequence theta 1 (t); cubic spline interpolation is carried out on the instantaneous turning angle theta (t) by utilizing matlab software to obtain the equal-angle instantaneous turning angle theta 1 A time series T at (T);
6. calculating the frequency f corresponding to the highest rotation speed of the motor 1 Namely: converting the unit r/min of the rotating speed into degree/s, and realizing the cutoff frequency f by utilizing matlab software 1 The low-pass filter filters the vibration signal S (t) to obtain a filtered vibration signal S 1 (t); realization of S pair by utilizing matlab software 1 (T) carrying out cubic spline interpolation to obtain a vibration sequence S at the time sequence T 2 (t), as shown in FIG. 7;
7. by the formula
Calculating a sequence of order ratios L, where n is the vibration sequence S 2 (t) has a length equal to 817;
8. vibration sequence S by utilizing matlab software 2 (t) performing Fast Fourier Transform (FFT) to obtain a ratio spectrum sequence S 3 (t); taking the order ratio sequence L as an abscissa, and taking the order ratio spectrum sequence S 3 And (t) drawing a ratio spectrum by taking the first m values of (m is half of the length of the sequence L equal to 408.5, and is 408)) as a vertical coordinate, and performing spectrum analysis by using the extracted ratio spectrum as shown in FIG. 8, wherein the ratio components of 1, 2, 3, 4 and 16 in the ratio spectrum are respectively corresponding to the order corresponding to the frequency conversion of the motor shaft of the second joint, the order corresponding to the frequency conversion of 2, 3 and 4 multiplied frequencies and the order corresponding to the meshing frequency of the sun wheel and the planet wheel, and other obvious orders are not present, so that the second joint is judged to be free of faults. The method is used for carrying out order ratio analysis on different joints to realize state monitoring and early fault diagnosis on each joint arm of the robot, and the condition that the robot is suddenly stopped due to the expiration of the service life of parts or some emergencies to damage a production line and influence production is prevented.
Claims (3)
1. A joint robot fault diagnosis method based on current and vibration signals is characterized by comprising the following specific steps:
(1) Synchronously acquiring a motor current signal I (t) and a vibration signal S (t) of an ith joint of the robot in the process of rotating at any angle, wherein t is sampling time;
(2) Filtering and deburring the current signal I (t) by adopting a method of combining zero-phase filtering with singular value denoising to obtain a filtered current signal I 1 (t)；
(3) By the formula
Calculating the current signal I 1 (t) phase phi (t) by the formula
Calculating the current signal I 1 (t) instantaneous frequency f (t);
(4) By the formula
Wherein p is the number of pole pairs of the motor, the instantaneous rotating speed n (t) of the motor shaft is obtained by calculation, and the instantaneous rotating speed n (t) is obtained by a formula
Calculating to obtain an instantaneous rotation angle theta (t) of the motor shaft;
(5) By the formula
Calculating an equal-angle sampling interval delta theta; maximum order ratio v max Is an integer greater than or equal to 1;
(6) Sampling the instantaneous rotation angle theta (t) according to the equal-angle sampling interval delta theta obtained by calculation in the step (5) to obtain an equal-angle instantaneous rotation angle sequence theta 1 (t)；
(7) Cubic spline interpolation is carried out on the instantaneous corner theta (t) to obtain an equal-angle instantaneous corner sequence theta 1 (T) time series T;
(8) Carrying out low-pass filtering on the vibration signal S (t) acquired in the step (1) to obtain a filtered signal S 1 (t) for S 1 (T) performing cubic spline interpolation to obtain a vibration sequence S of the time sequence T 2 (t)；
(9) By the formula
Wherein N =0, 1, 2, 3,.. N.1, maximum order ratio v max Is greater thanOr an integer equal to 1, calculating a sequence of order ratios L, where n is the vibration sequence S 2 (t) length;
(10) For vibration sequence S 2 (t) performing fast Fourier transform to obtain a ratio spectrum sequence S 3 (t)；
Taking the order ratio sequence L as an abscissa, and taking the order ratio spectrum sequence S 3 (t) drawing a scale spectrum with the first m values as vertical coordinates, wherein the m value is half of the length of the scale sequence L, and if L is an odd number, rounding the half of the length of the scale sequence L downwards;
and observing whether the order ratio of fault characteristics of each part of the robot joint exists in order ratio components in the order ratio spectrum, if so, indicating that the part has a fault, and if not, indicating that the joint has no fault, thereby completing the order ratio analysis of the vibration signals and realizing the fault diagnosis and state detection of the robot joint.
2. The joint robot fault diagnosis method based on current and vibration signals according to claim 1, characterized in that: and acquiring a motor current signal I (t) of the ith joint of the robot through a current sensor.
3. The joint robot fault diagnosis method based on current and vibration signals according to claim 1, characterized in that: and acquiring a vibration signal S (t) of the ith joint of the robot through an acceleration sensor.
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| CN113405795B (en) * | 2021-06-22 | 2023-12-12 | 昆明理工大学 | Method for identifying weak faults of joint RV reducer |
| CN113985276B (en) * | 2021-10-18 | 2024-02-27 | 上海电气风电集团股份有限公司 | Fault diagnosis method and device for wind generating set |
| CN114970227B (en) * | 2021-11-10 | 2024-01-05 | 昆明理工大学 | Joint vibration solving method of industrial robot based on joint current and modal analysis |
| CN114441125B (en) * | 2021-12-24 | 2022-10-28 | 北京化工大学 | Non-contact type turbine machinery high-rotating-speed blade vibration multi-mode decomposition method |
| CN114454213B (en) * | 2022-01-26 | 2023-12-12 | 东华大学 | Industrial robot joint current signal abnormality detection method based on EEMD-HT-kurtosis analysis |
| CN114608821A (en) * | 2022-03-01 | 2022-06-10 | 北京辰宇航康科技有限公司 | Method and device for determining order spectrum of vibration signal of rotating machine |
| CN114700988B (en) * | 2022-05-09 | 2023-10-24 | 西安交通大学 | Joint motion dividing method for health monitoring of industrial robot transmission part |
| CN116533253B (en) * | 2023-07-03 | 2023-09-19 | 佛山智能装备技术研究院 | Industrial robot fault diagnosis method based on feedback current spectrum analysis |
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| CN103868694B (en) * | 2014-03-26 | 2016-01-20 | 东南大学 | A kind of embedded variable speed bearing fault diagnosing apparatus |
| CN106124197B (en) * | 2016-06-14 | 2018-10-02 | 昆明理工大学 | A kind of epicyclic gearbox sun gear partial fault detection method and system |
| CN108120598B (en) * | 2017-12-19 | 2019-09-13 | 胡文扬 | Square phase-couple and the bearing incipient fault detection method for improving bispectrum algorithm |
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