CN102254100A - Proportional hazard rate model method for estimating operation reliability of tool - Google Patents

Abstract

The invention relates to a proportional hazard rate model method for estimating operation reliability of a tool. Defects of difficulty in obtaining burn-out life data, incomplete matching with actual operation conditions of equipment and incapability of timely prevention and maintenance exist in the prior art. According to the technical scheme provided by the invention, the proportional hazard rate model method for estimating operation reliability of the tool comprises the following operation steps of: 1, using an effective value (RMS (Root Mean Square)) and a peak value (P) in a characteristic signal as covariates in a proportional hazard rate model; 2, calculating model parameters according to a nonlinear equation described in the specification; and 3, obtaining parameter results of maximum likelihood estimation of the tool working in different regressive states by applying a maximum likelihood estimation method of the proportional hazard rate model, and solving a current hazard rate according to state signals of the processing system tool working in different regressive states and finally obtaining the reliability. The method has the advantages of good instantaneity and reliable estimation result.

Description

The ratio failure rate model method of cutter operational reliability assessment

Technical field

The invention belongs to electromechanical equipment monitoring running state and reliability engineering field, be specifically related to the ratio failure rate model reliability estimation method of digitizing manufacturing equipment running status, further relate to the ratio failure rate model method of cutter operational reliability assessment.

Background technology

Traditional reliability modeling, analysis, appraisal procedure generally are to be based upon on the classical probability statistics basis, need carry out the large sample durability test to equipment, the life-span distributed data of statistics equipment, this way not only wastes time and energy, less economical, what what is more important tradition analysis method for reliability obtained is the global reliability of equipment, these statisticss have little significance for separate unit that is moving or short run equipment, and what people more were concerned about is the life-span nargin and the safe reliability of currently used equipment.Traditional reliability estimation method based on probability statistics generally depends on the burn-out life data, and adopt this method for the equipment of a large amount of real-time workings is unfavorable, because it is relatively more difficult usually to obtain the burn-out life data, need obtain by durability test and accelerated life test, and do not conform to very much with the operation conditions of equipment reality.

Summary of the invention

The object of the present invention is to provide the ratio failure rate model method of a kind of cutter operational reliability assessment, obtain burn-out life data relatively difficulty, the shortcoming that do not conform to very much, can not give timely preventive maintenance with the operation conditions of equipment reality with what overcome that prior art exists.

For overcoming the problem that prior art exists, technical scheme of the present invention is:

A kind of ratio failure rate model method of cutter operational reliability assessment, its operation steps is as follows:

1) with the effective value in the characteristic signal (RMS), peak value (P) as the covariant in the ratio failure rate model;

2) carry out the calculating of model parameter according to one group of following nonlinear equation:

Symbol definition wherein is as follows:

	Likelihood function
		Z 1V	The covariant of effective value
Z 2P	The covariant of peak value
		1	The regression parameter of effective value
2	The regression parameter of peak value
		t	Wear-out life
	The logarithm average of wearing and tearing
			The logarithm standard deviation of wearing and tearing

3) the maximum likelihood appraisal procedure of application percentage failure rate model obtains the cutter parameter result that maximum likelihood is assessed when difference degeneration shape state.According to the status signal of system of processing cutter under different degenerate state work

Try to achieve current failure rate

For

Finally obtain fiduciary level For

Structure principle of the present invention is as follows:

The equipment dependability model can not constitute with existing modeling method simply, must consider the characteristic parameter of equipment running status and the rule trend of life-span distribution, on the basis of abundant research equipment running status failure mechanism, comprehensively apply in a flexible way and analyzed and solve with the reliability statistics theory based on the fault signature extraction of monitoring information.Compared with prior art, advantage of the present invention is:

1, the present invention is by the reliability modeling based on active monitoring mechanism, the overall reliability of equipment is by the data of utilizing the automatic monitoring record device of state to provide of off-line, count the accumulated time and the number of times of work in every kind of equipment regular period, standby, maintenance, and parameter such as mean time between failures, count the reliability properties value of prior distribution.The individual operational reliability of equipment is by online active monitoring, utilize physical quantitys such as vibration, power (moment), acoustic emission, handle through some feature extracting methods, obtain the real-time degradation information of equipment state feature, these running state information can reflect the operational reliability of equipment.The comprehensive passing ratio failure rate model of the key components and parts overall reliability of equipment and current operational reliability organically connects, and the reliability assessment of Shi Xianing is more near actual state like this, and real-time is good, and assessment result is reliable.

2, this method distributes the overall life of similar cutter and combines with the monitoring running state information of cutter individuality, and passing ratio failure rate model is got in touch setting up between covariant such as the effective value of cutter running status vibration signal signal characteristic, peak value and reliability statistics.Have the advantage of state covariant (Covariates) performance of dependence time according to ratio failure rate model, use the maximum likelihood method of estimation to obtain one group of nonlinear equation Model parameter is found the solution.Finally can try to achieve current failure rate according to cutter working time and status signal, thereby obtain the indexs such as fiduciary level of cutter operation, Tool Reliability assessment can be upgraded on the basis based on the status monitoring data timely, for the preventive maintenance based on state of manufacturing industry digitizing system of processing provides support.

3, method real-time of the present invention is good, assessment result is reliable, be a kind of new method that has developed traditional reliability estimation method, be applicable to the real-time reliability assessment of cutter operational process, have future in engineering applications widely at equipment manufacture digitizing manufacture field.

Description of drawings:

Fig. 1 is cutter 1 time domain waveform and frequency spectrum thereof:

Fig. 2 is cutter 1 time domain effective value, peak value, kurtosis, peak value index;

Fig. 3 is cutter 2 time domain waveforms and frequency spectrum thereof;

Fig. 4 is cutter 2 time domain effective values, peak value, kurtosis, peak value index;

Fig. 5 is the fiduciary level curve of cutter 1;

Fig. 6 is the fiduciary level curve of cutter 2.

Embodiment:

Below in conjunction with realizing that principle, example and accompanying drawing describe in detail the present invention.

The realization principle of technical solution of the present invention is:

1) uses the characteristic signal of reflection cutter running status, at first select suitable index in the characteristic signal as the covariant in the ratio failure rate model , selection course specifically may further comprise the steps:

An if burst

,

Be signal length, then effective value, peak value, kurtosis, peak value index definition are as follows.

(1) effective value:

(2) peak value:

In the formula,

Be meant mathematical expectation.

(3) kurtosis:

In the formula,

The average of expression signal,

The standard deviation of expression signal,

(4) peak value index:

2) Comparative Examples failure rate Model parameter is carried out the estimation of dependability parameter, uses the maximum likelihood method of estimation to find the solution, and obtains current failure rate, realizes the assessment to indexs such as fiduciary levels, and is concrete May further comprise the steps:

(1) it is as follows to set up the form of ratio failure rate model:

In the formula,

Be failure rate, not only relevant with the time, also depend on the value of adjoint variable and regression coefficient;

It is only relevant basic failure rate with the time; Z is a covariant, the reflection equipment running status;

Be regression parameter, expression covariant Z is to the influence of equipment failure rate.

As if the failure rate substitution ratio failure rate model that benchmark is distributed as lognormal distribution, then ratio failure rate modular form just becomes Weibull ratio failure rate model, is provided by following formula:

Failure rate function

And Reliability Function

Between the pass be

The Reliability Function of lognormal distribution then Be expressed as

(2) utilize the likelihood function of following formula

In the formula,

Be Reliability Function,

Be failure rate function, F, CBe failure set and truncation collection.

With the ratio probability density of failure function and the Reliability Function substitution formula likelihood function of lognormal distribution, the likelihood function that obtains lognormal distribution is

Taken the logarithm simultaneously in these formula both sides, corresponding log-likelihood function is

According to the maximum likelihood appraisal procedure, with lnL to parameter to be assessed

Ask local derviation, and make that each equation is 0, it is as follows to obtain one group of nonlinear equation

3) for the parameter to be assessed in this group nonlinear equation that obtains by likelihood function, the maximum likelihood appraisal procedure of application percentage failure rate model, different degenerate states according to cutter give majorized function fminsearch certain optimization searching initial value, can obtain the result of cutter in the maximum likelihood assessment in 1,2 o'clock of difference degeneration shape state.After the ratio failure rate model parameter that gets lognormal distribution, just can be according to the status signal of system of processing cutter under different degenerate state work

Try to achieve current failure rate

Thereby, can obtain fiduciary level

Etc. index.

Example:

Numerical control device, tool type and cutting material, data acquisition equipment and parameter etc. used in the Tool Reliability analytical test see Table 1.

Table 1 Tool Reliability testing equipment and parameter

Vibration signal and frequency spectrum thereof when Fig. 1 is cutter 1 processing work during from t=84min to t=104min, the energy of signal mainly concentrates between 3000～9000Hz frequency band as can be seen from Figure.Fig. 2 is cutter 1 a time domain index variation diagram, can observe and can observe in cutter is degenerated process time, and effective value (RMS), peak value (P) variation tendency are more obvious, and kurtosis (K), peak value index (CF) variation tendency are not clearly.

Vibration signal and frequency spectrum thereof when Fig. 3 is cutter 2 processing works during from t=75min to t=100min, the energy of signal mainly concentrates between 3000～9000Hz frequency band as can be seen from Figure.Fig. 4 is cutter 2 time domain index variation diagrams, can observe in cutter is degenerated process time, and effective value (RMS), peak value (P) variation tendency are more obvious, and kurtosis (K), peak value index (CF) variation tendency are not clearly.

Choose two representative time domain indexes of vibration cutting signal time domain index effective value and peak value in this method example as covariant, and be incorporated into ratio failure rate model, carry out the assessment of Tool Reliability as reflection cutter degenerate state.

Table 2 is depicted as cutter 1 and 2 degeneration logouts and logarithm average, the logarithm standard deviation degraded data of the tool abrasion that calculates.Use the maximum likelihood appraisal procedure of the ratio failure rate model parameter estimation of lognormal distribution, different running statuses according to cutter give majorized function fminsearch certain optimization searching initial value, find the solution regression vector when obtaining cutter 1 and 2 degeneration running statuses by programming

The maximum likelihood results estimated is as shown in table 3.

 

The result of parameter estimation when table 3 cutter 1 and 2 degeneration running statuses

Find the solution the regression vector when obtaining degenerating running status

,

After, according to the Reliability Function of lognormal distribution

Obtain the reliability assessment curve of cutter 1,2 when different running statuses and degree of degeneration at last shown in Fig. 5,6, reflected size and the variation tendency of different cutters in actual degeneration running status fiduciary level when losing efficacy.This shows that the difference of the individual fiduciary level of different cutters under the degeneration machining state is apparent in view, this has just in time illustrated the otherness of cutter overall life and individual life span, and the actual motion fiduciary level of different cutters is that difference is bigger.Grasped the fiduciary level Changing Pattern of cutter individuality, in time changed cutter and keep in repair significant for the residual life of analyzing cutter and enforcement.

Claims (1)

1. the ratio failure rate model method of cutter operational reliability assessment, its operation steps is as follows:

1) with the effective value in the characteristic signal (RMS), peak value (P) as the covariant in the ratio failure rate model;

2) carry out the calculating of model parameter according to one group of following nonlinear equation:

Symbol definition wherein is as follows:

Likelihood function Z _1V The covariant of effective value Z _2P The covariant of peak value

1 The regression parameter of effective value

2 The regression parameter of peak value t Wear-out life

The logarithm average of wearing and tearing

The logarithm standard deviation of wearing and tearing

3) the maximum likelihood appraisal procedure of application percentage failure rate model obtains the cutter parameter result that maximum likelihood is assessed when difference degeneration shape state, according to the status signal of system of processing cutter under different degenerate state work

Try to achieve current failure rate

For

Finally obtain fiduciary level

For

。

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