JPH0252234A - Diagnosis method for machine equipment by moter current - Google Patents

Abstract

PURPOSE:To enable the sure diagnosis of a sudden abnormality of machine equipments and the abnormality like a long time function deterioration, etc., individually by analysing a time series variation of supplied current to a moter in driving the machine equipments. CONSTITUTION:A detection processing 11 for absolute comparison is performed to judge whether a current signal obtained by detecting 4 the supply current supplied to a moter 2 in driving machine equipments 1 is located within the limit of a fixed upper limit value and a fixed lower limit value which are set up in advance corresponding to the machine equipments 1 or not. In the case the value is out of the limit, it is diagnosed as the abnormality in the machine equipments 1. And, referring to the actual results of change in the lapse of time based on a latest shifting average value and deviation value of the current signal, a detection processing 12 for relative comparison is performed to judge whether the current signal is located within the limit of a variable setting upper limit value and variable setting lower limit value which are calculated and set up corresponding to the machine equipments 1 or not, and in the case of the value is out of the limit, it is diagnosed as that there is the abnormality in the machine equipments 1.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is a method for diagnosing mechanical equipment based on the current supplied to the electric motor, which is the driving source of the mechanical equipment, and detecting an abnormality in the equipment. It concerns a diagnostic method.

[Conventional technology]

Conventionally, the reality is that there has been no effective solution for diagnosing abnormalities in electric motors and the mechanical equipment that serves as their loads.

Regarding electric motors, thermal relays are used to detect and protect motors from the standpoint of motor capacity limitations, but it is not possible to detect abnormalities in mechanical equipment driven by these motors. Ta.

In addition, abnormality diagnosis of mechanical equipment is achieved by installing dedicated sensors for each failure that we want to detect.

For example, detected malfunctions of con-hair conveying equipment include bent shear pins and slips of apron feeders, breakage and slips of V-healds of crushers, breakages and slips of V-healds of screens, slips and deviations of con-hairs, etc. The failure details differ depending on the mechanical equipment, and it is necessary to combine the failure details to be detected for each mechanical equipment. To prevent the conveyor from shifting, large limit switches with rollers are placed facing each other on the belt ears.
Belt slippage is detected by means such as installing a speed switch on the pulley shaft on the non-drive side, and various other attempts have been made to detect belt breakage, shear pin breakage, etc.

As a new attempt at diagnosing abnormalities in mechanical equipment, there is a method of monitoring the electric current value or power value of the electric motor driving the mechanical equipment using upper and lower set values. A specific example of this method is JP-A-51-14385.
6 and Japanese Patent Application Laid-open No. 53-037566.

The method disclosed in Japanese Patent Application Laid-Open No. 52143856 diagnoses abnormalities in mechanical equipment by monitoring the current of the motor during no-load based on the rotation speed.
．． The method disclosed in Japanese Patent No. 1037566 diagnoses abnormalities in mechanical equipment by detecting the roll load and motor current of a hot rolling mill.

[Problem to be solved by the invention]

However, the method of diagnosing abnormalities in mechanical equipment using hardware sensors does not have perfect failure detection ability and is low in reliability, requiring a great deal of effort to maintain the dedicated hardware sensors, and the detection speed is low. There are problems in that the process is slow, it is difficult to prevent mechanical damage before it occurs, and the individual hard sensors are expensive.

Furthermore, the method disclosed in Japanese Patent Application Laid-Open No. 52-143856 can only detect abnormalities in the motor itself;
In addition, there is a problem that it is not possible to make a judgment including deterioration, and since it is not possible to determine abnormalities including diagnosis of mechanical equipment using this electric motor, there is a problem that it cannot be said to be a highly useful abnormality diagnosis method. Similarly, JP-A-51-0375
The method disclosed in Japanese Patent No. 66 does not detect abnormalities, including changes over time during use, and is therefore insufficient as a technique for diagnosing abnormalities over a long period of time.

That is, in the conventional technology, there is no effective solution for (1) abnormality diagnosis of the electric motor and the mechanical equipment that is its load.

■Some of the abnormality diagnosis of mechanical equipment is performed using specialized hardware and expensive sensors, but the detection ability is not perfect, the reliability is low, the responsiveness is low, and maintenance requires a lot of effort. It is. ■There is a method of determining the upper and lower limits of current and power values, but this method has problems such as being buried in large changes in the normal time constant of mechanical equipment and not being able to detect true mechanical abnormalities.

Therefore, the present invention was devised to solve the above-mentioned problems in the conventional technology.The present invention uses the supply current of the driving electric motor, which is the drive source of mechanical equipment, as an index, and analyzes changes in this supply current for each diagnosis target. By doing so, the aim is to independently and reliably diagnose sudden abnormalities in mechanical equipment and abnormalities such as long-term functional decline.

[Means and operations for solving the problem] As shown in FIG. 1, the means of the present invention for achieving the above object detects the current supplied to the electric motor 2 that is driving the mechanical equipment and generates a current signal. Determine whether or not this current signal is within the range of the fixed setting lower limit value and the fixed setting lower limit value that are preset corresponding to the mechanical equipment, and determine whether it is outside of this range. If the current signal is the most recent moving average value and the deviation value of the current signal, the absolute comparison detection process 11 is performed to diagnose that there is an abnormality in the mechanical equipment. Determine whether or not the value is within the range between the upper limit value of the fluctuation setting and the lower limit value of the fluctuation setting calculated for the equipment, and if it is outside this range, diagnose that there is an abnormality in the mechanical equipment. Performing relative comparison detection processing 12.

(See Fig. 2 below) The current signal to be subjected to the absolute comparison detection processing 11 and the relative comparison detection processing 12 includes detecting the supply current of the motor 2 to obtain a detection current signal, and obtaining an analog value of this detection current signal. is converted into a sampling current signal by temporal sampling processing 8, and then the integrated current signal obtained by simply performing integration processing 9 on this sampling current signal is used, or this integrated current signal is subjected to digital filter processing 10. A filtered current signal obtained by smoothing out momentary abnormal values and removing impulse noise is used.

In addition to the above means, it is preferable to perform a CRT display process that displays the instantaneous value of the current signal and also displays the results of the absolute comparison detection process 11 and the relative comparison detection process 12, and also temporarily stores the current signal. It is preferable to perform data tracing processing on the shifted current signal data, such as digital filter processing 10, absolute comparison detection processing 11, relative comparison detection processing 12, and CRT display processing. That is, the tuning level is improved by reproducing the stocked current signal data and verifying the validity with the current data when a failure is determined.

In addition, in order to obtain more accurate diagnostic results, absolute comparison detection processing 11, relative comparison detection processing 12, and supply/cutoff of current signals to be processed for CRT display are performed, and this current signal is converted into an integrated current signal and a filter current signal. It is advantageous to carry out a switching process to switch the setting to either one of the two.

That is, in the relative comparison detection process 12, the input current signal is subjected to a "variation setting" which is calculated and set corresponding to the mechanical equipment based on the actual change over time based on the most recent moving average value and deviation value of the current signal. Since it is determined whether the current signal is within the range between the limit value and the lower limit value of the fluctuation setting, changes in the current signal due to changes in the load amount that have a large time constant of the mechanical equipment itself are ignored, and the time constant of the time constant at the time of failure is ignored. Since it catches small differential current changes, it is more responsive and detects failures that suddenly occur in mechanical equipment, so it is mainly targeted at diagnosis of mechanical equipment. On the other hand, in the absolute comparison detection process 11, it is determined whether the current signal is within the range of a fixed setting upper limit value and a fixed setting lower limit value that are preset corresponding to the mechanical equipment, so the relative comparison detection process Since the developed fault which is an absolute abnormality with an amplitude larger than 12 is detected, the main target for diagnosis is to detect a functional decline in mechanical equipment, that is, a motor fault.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to FIG.

A current detection sensor for current detection 4 is installed in one of the power supply lines 3 to the electric motor 2 that drives the mechanical equipment 1. This current detection sensor detects a current supplied to the motor 2, that is, a detection current signal A that is an indicator of the state of the mechanical equipment 1.
(i) is obtained. The obtained detected current signal A(i) is subjected to AC-+DC conversion and constant ratio conversion by the converter 5, A-D conversion is performed by the I10 module 6, and is taken into the digital controller 7 and sent to the digital software. Processing is done. Detected current signals A(i) from other combinations of mechanical equipment 1 and electric motor 2 are similarly processed in parallel and taken into the I10 module 6, but the subsequent processing within the digital controller 7 is Multiple processes are performed for each division. In other words, each block configuration is a subroutine process.

Next, specific calculation contents in each block configuration within this digital controller 7 will be explained.

Sampling Process 8 The detected current signal (i) (i=1.2, . . . m, m=115 in the present invention) taken into the digital controller 7 is immediately subjected to sampling process 8. That is, each current signal of the detected current signal A(i) is temporally sampled by regular scanning (8T), and the raw information of the current is thinned out appropriately to obtain the sampled current signal A.
, (+) (i=1.2, . . . m).

○ Integration processing 9 The shaped sampling current signal A, (i) is subjected to integration processing 9 and becomes an integrated current signal A, (i) (i=1.2,...
m") (m'< m). This integration processing 9 is performed by calculating the sampling current signal A, (i ) is used as a simple integration process to obtain the current index for each mechanical equipment unit.

○Digital filter processing 10 Appropriate filter processing is performed on rapidly changing current changes according to the intended use and the mechanical equipment 1. As a result, momentary abnormal values are smoothed out and impulse noise is removed. As a digital filter, a -order lag filter is used, and the filter current signal Ar resulting from the digital filter processing of this integrated current signal As(i) is A r (i) k =ΔT' As (i) k /
(T + ΔT') + T A r (i) k-l/ (
T+ΔT'). Note that k and -1 are suffixes representing the sampling time series, T is the time constant, and ΔT"
is the sampling time.

The time constant T and sampling time ΔT' are each 0.
．． In the range of 0 to 5.0 sec, 0.0 to 2.0 sec,
The setting is made according to the intended use and the mechanical equipment 1.

In addition, the sampling time ΔT′ is the scheduled scan ΔT
be an integer multiple of

○Absolute comparison detection processing 11 In the absolute comparison detection processing 11, the obtained integrated current signal As
(i) or the fixed setting upper limit value AA)l which is a fixed setting value for the instantaneous change value of the filter current signal AF(i).
(i) and the fixed set lower limit value AAL(i), the upper and lower limits are checked, and if it deviates from this range, it is diagnosed as defective and a stop command A is output to the electric motor 2, and an alarm command is sent to the CRT display processing 13. Output B.

That is, As (+) > AA) l(i) or AP (i)
> AAo (i) for upper limit alarm, As (i) < AAL (i) or AF (i)
A lower limit alarm is output at <AAt(i) and a failure diagnosis is performed.

Fixed setting upper limit value AA) I (i) and fixed setting lower limit value A
AL(i) is set for each mechanical equipment 1 separately.

Note that a switching process 15, which is a switch function, is provided before the absolute comparison detection process 11, and converts the electric signal subjected to the absolute comparison detection process 11 into the integrated current signal As(i) and the filter current signal AF(i). is selected, and the corresponding mechanical equipment 1 is turned off while it is stopped and during the standby time j+ SeC after startup. This switching process 1
5, the fault diagnosis by the absolute comparison detection process 11 is stopped when the absolute comparison detection process 11 is stopped while the mechanical equipment 1 is stopped.
If you do this, a lower limit alarm will be output,
This is because if the absolute comparison detection process 11 is performed during the standby time tsec, a malfunction in which an upper limit alarm is output due to the starting current will occur, and this is to prevent this malfunction from occurring. Standby time t, SeC is each mechanical equipment 1
Set separately.

○Relative comparison detection processing 12 The relative comparison detection processing 12 calculates a fluctuation setting upper limit value A R+1 (i), which is a fluctuation setting value, with respect to the instantaneous change value of the integrated current signal As(i) or filter current signal AF(i). The upper and lower limits are checked based on the fluctuation setting lower limit value ARt(i), and if it deviates from this range, it is diagnosed that a failure has occurred, and a stop command C is output to the electric motor 2, and an alarm command B is sent to the CRT display processing 13. Output.

That is, As (i) > A++u(i) or AF (i)
>Ai, I(i) sets the upper limit alarm, A s (i) < ARt(i) or A F (i
) < A RL (i) outputs a lower limit alarm and performs failure diagnosis.

The calculation of this fluctuation setting upper limit value A, 1) I (i) and fluctuation setting lower limit value Ant (i) is A RH (i) - Edict 1) n-1 + a・λ (i) n-
1... (1) AiL(i) -■ "Shitanka go a-λ(i)n-1
... (2) As (i)n 1-(As (i)n 1
+As (i)n 2+・ ・ ・As (i
) n 1. ) / 12・ ・ ・ ・ ・ (3
) λ2(i)n -1=1/(12-1) ・Σ[As
(i) j■ "石m子]〕2 ・ ・ ・ ・ ・ ・ (4) Here, n is the suffix representing the time series of sampling, l is the number of samples (0 to 30), and ΔT" is the sampling time. (~6.0sec), a is 0.0~99
．． It is a coefficient up to 9. Also, the sampling time ΔT
” is an integer multiple of scheduled scan 8T, and the number of samples!
The sampling time ΔT'' and the coefficient a are set for each mechanical equipment 1, that is, for each i, according to the respective characteristics.

Equation (3) calculates the moving average value based on the most recent sample number β of current changes, and (4)
The formula calculates the standard deviation value of the current change in the same range as the formula (3).

(3) Based on the variables in equations (4) < Equations (1) and (2) mean that the upper and lower limits are is set, and failure diagnosis is performed by comparing with this set value. In other words, the calculated fluctuation setting upper limit value A*o(i) and fluctuation setting lower limit value A++t(+) are not fixed, but the quality of the current value is determined based on the own past current change performance. Relative abnormality detection is performed by capturing a sudden increase in the deviation value, that is, a differential current change. FIG. 4 shows an example of this relationship, with the integrated current signal As(
i), the upper and lower limit check range formed by the variable setting upper limit value AR11(i) and the variable setting lower limit values A and 1L(i) is the fixed setting upper limit value AAo.
It is narrower than the upper and lower limit check range formed by (i) and the fixed set lower limit value AAL(i), and changes in accordance with changes in the integrated current signal As(i).

In this FIG. 4, As(i)n is the integrated current signal A
It is a sampling current signal of s(i), and the fixed upper limit value AAH is set for each mechanical equipment as the rated current value x approximately 80%, and the fixed lower limit value AAL is similarly set as the rated current x approximately 20%.
It was set in %. In this FIG. 4, the integrated current signal As(
The current value As(i)n of i) is the fluctuation setting upper limit value A, 1lI
This shows a state in which more than (i) has been caught.

Scheduled scan ΔT1 Time constant T1 Sampling time ΔT
Regarding the settings of ゛, ΔT'', sampling number 15 coefficient a, fixed setting upper limit value AAll (i), and fixed setting lower limit value AAL (i), it is necessary to set the total value (as this is a world without theory, so experience and intuition are required for a long period of time). This is because the current behavior of the electric motor 2 varies greatly depending on the mechanical equipment 1, and it is necessary to set it individually.In this example, normally condition, the fixed setting upper limit value AaH (i), fixed setting lower limit value AAL (i), variable setting upper limit value ARH (i), and variable setting lower limit value ARL (i) are gradually adjusted over a long period of time to a level that does not cause a failure determination. The settings were narrowed down to:
Rather than making changes blindly, they were gradually set according to certain rules based on experience and intuition.

In short, the relative comparison detection process 12 ignores changes in the load amount of the mechanical equipment 1 itself, which has a large time constant, and catches daily current changes that are differential changes with a small time constant when a failure occurs. On the other hand, in the absolute comparison detection process 11, an absolute abnormal current change with a larger amplitude than in the relative comparison detection process 12, that is, the mechanical equipment 1
It catches current changes that occur due to changes in the load amount that have a large time constant. In this way, the integrated current signal As
The reason why (i) and filter current signal AF (i) are used depends on the load characteristics of the mechanical equipment 1, and it is wise to use the raw value (integrated current signal As(i)) as much as possible. Even in this state, the filter current signal AF(i) is used for the mechanical equipment 1 that undergoes severe current hunting, and malfunction is prevented particularly by the relative comparison detection processing 12.

Note that, similar to the absolute comparison detection process 11, a switching process 15 is also provided before the relative comparison detection process 12.

0CRT display processing 13 CR7 display processing 13 displays a bar graph of the instantaneous value of the integrated current signal A, (i) or filter current signal Ay(i),
Or perform trend display and absolute comparison detection processing 1
1 and relative comparison detection processing 12 are displayed as an alarm, thereby informing the operator of the operating status of the mechanical equipment 1 and the details of the failure that has occurred.

Note that the switching process 15 is also performed before the CR7 display process 13, as in the case of the absolute comparison detection process 11 and the relative comparison detection process 12.

○Data trace processing 14 The data trace processing 14 temporally converts the integrated current signal As(i) subjected to the integration processing 8 as data.
This stored data is swept out and sent back to digital filter processing 10, absolute comparison detection processing 11, and relative comparison detection processing 12 for processing.This data trace processing 14 allows mechanical equipment to be detected based on the time-series behavior of current. The state or operation of 1 is analyzed and detected.

As described above, the operating order of the illustrated embodiment in FIG. , this is detected as a change in the current of the motor 2 that drives it.

Part 2 In order to monitor a large number of mechanical equipment 1, the current of each electric motor 2 is sampled and detected at every predetermined cycle.

Part 3: In order to know the abnormality of the mechanical equipment 1, the detected current value of each electric motor 2 is judged for each mechanical equipment 1 unit.

Part 4 ■ The current values collected for each unit of mechanical equipment are used for abnormality judgment according to their absolute values or deviation amounts based on changes in absolute values.

(2) In the mechanical equipment 1, in order to eliminate changes (instantaneous changes) in the current due to non-abnormalities, the instantaneous abnormal values are smoothed out and the changes in the current value are monitored and used for abnormality determination. For example, in a crusher, the current value may rise momentarily due to the introduction of foreign matter, and this is not an abnormality in the mechanical equipment 1 (
Since this is a problem on the raw material side, the abnormal value is cut to cancel it.

Part 5 Diagnose using the data in part 4, but if the
Data for a certain period of time after startup is deleted.

Immediately after startup, each current value increases due to inertia torque, etc., so this is for the purpose of preventing erroneous detection, and the reason for stopping is because there is a period when there is no current value or the motor is rotating due to inertia.

Part 6 Diagnosis is performed by absolute comparative detection and relative comparative detection.

FIG. 5 shows an actual measurement example of a current chart according to the method of the present invention, in which a variable setting upper limit abnormality detection signal a is detected in the part A, a fixed setting upper limit and lower limit abnormality detection signal C is detected in the mouth and part, Part C shows a state in which the variation setting lower limit abnormality detection signal is detected.

An example of the object to be diagnosed according to the present invention is a conveyor transport device. Diagnosis targets and detected contents in this conveyor conveyance equipment include shear pin breakage and slipping of the apron feeder, V-belt breakage and slipping of the crusher, V-belt breakage and slipping of the screen, and slipping and deviation of the conveyor.

〔Effect of the invention〕

Since the present invention has the above-described configuration, it can exhibit the following effects.

Abnormalities in electric motors and mechanical equipment are diagnosed by analyzing time-series changes in the supply current of electric motors that are driving mechanical equipment, so it is possible to detect abnormalities due to sudden failures of not only electric motors but also mechanical equipment. Judgments including deterioration and functional decline can be made.

In this way, it is possible to determine the long-term deterioration and functional deterioration of mechanical equipment that combines electric motors, so maintenance management of mechanical equipment that combines electric motors becomes accurate and complete, thereby preventing sudden accidents. It is possible to significantly reduce the occurrence rate of , and also to allow mechanical equipment to be operated in good condition at all times.

Since abnormalities can be determined quickly, it is possible to prevent damage to machinery and equipment, and because the tendency of abnormalities to occur can be known in advance, the content of abnormalities can be quickly and accurately known. It is possible to accurately respond to failures that occur.

Since the supplied current of the electric motor during driving is used as an index, it is possible to obtain judgments with high reliability and high responsiveness.Also, since the supplied current of the electric motor is simply taken out, it was carried out. The equipment cost is low and maintainability is extremely good.

[Brief explanation of the drawing]

FIG. 1 is a flow diagram showing the basic operation of the method of the present invention. FIG. 2 is a flow diagram showing the operation of one embodiment of the method of the present invention. FIG. 3 is an explanatory diagram showing the overall block configuration of an embodiment in which the method of the present invention is implemented. FIG. 4 is a diagram for explaining an example of time-series analysis of current according to the method of the present invention. FIG. 5 shows an example of actual measurement of a current chart using the method of the present invention. Explanation of symbols 1; Mechanical equipment, 2; Electric motor, 3; Power line, 4; Current detection, 5; Converter, 6; I10 module, 7; Digital controller, 8; Sampling process, 9; Integration process, 10 Digital filter processing, 11; Absolute comparison detection processing, I2; Relative comparison detection processing, 13; CRT display processing, 14; Data trace processing, A(i); Detection current signal, As(i); Sampling current signal, As (i); Accumulated current signal, Ap(i); Filter current signal, Ano(
i); Fixed upper limit value, AAL(i); Fixed lower limit value, Aao(i); Fluctuation upper limit value, AR+, (i); Fluctuation lower limit value. Applicant: Kawasaki Steel Co., Ltd.

Claims (5)

[Claims] (1) The current signal obtained by detecting the supply current of the electric motor driving the mechanical equipment is located within the range of the fixed setting upper limit value and the fixed setting lower limit value that are preset corresponding to the mechanical equipment. Absolute comparison detection processing to determine whether
If it is out of the range, it is diagnosed that there is an abnormality in the mechanical equipment, and the current signal is determined based on the actual change over time based on the most recent moving average value and deviation value of the current signal. A relative comparison detection process is performed to determine whether or not the machine is located within the range of the fluctuation setting upper limit value and the fluctuation setting lower limit value that are calculated and set corresponding to the equipment. A method of diagnosing mechanical equipment using motor current to diagnose abnormalities in equipment. (2) Detecting the supply current of the electric motor driving the mechanical equipment,
The analog value of the detected current signal is converted into a sampled current signal by temporal sampling processing, the sampled current signal is simply integrated to obtain an integrated current signal, and the integrated current signal is digitally filtered to obtain an instantaneous value. 2. The method for diagnosing mechanical equipment using motor current according to claim 1, wherein a filtered current signal is obtained by smoothing abnormal values to remove impulse noise, and the filtered current signal and the integrated current signal are used as the current signal. (3) CRT that displays the instantaneous value of the current signal as well as the results of absolute comparison detection processing and relative comparison detection processing
A method for diagnosing mechanical equipment using motor current according to claim 1 or 2, wherein display processing is performed. (4) The current signal is temporarily stocked, and the stocked current signal data is subjected to digital filter processing, absolute comparison detection processing, relative comparison detection processing, and data tracing processing for performing CRT display processing. A method of diagnosing mechanical equipment using motor current. (5) Absolute comparison detection processing, relative comparison detection processing and CR
In addition to supplying and cutting off the current signal to be subjected to T display processing,
Claim 2 or 3, wherein a switching process is performed to switch and set the current signal to either an integrated current signal or a filtered current signal.
A method for diagnosing mechanical equipment using the motor current described above.