JOANNA WILCZARSKA
University of Technology and Life Sciences
GENESIS OF THE TECHNICAL CONDITION OF EXPLOITATION MACHINES
Summary
Applying the optimal method of exploitation for the estimation of the techni-cal condition of machines is the basis of the automation process for condition identifi-cation. It requires many important undertakings, precise evaluation and reliability state forecasting, considering the genesis of technical condition of machines.
To issue genesis reliability, it requires an analysis of technical condition prior to conducting the identification of problems, recognizing machine condition and ways of solving these problems, as well as determining abilities of using operational research methods for solving the recognized problems.
Keywords: genesis of state of machines, diagnostic parameters, technical state 1. Recognizing machine condition
Process methodology requires the identification of machine condition, following test phases for notable evaluation (Fig. 1):
a) diagnosing – as the process of determining machine condition at Θb moment;
b) forecasting – as the process of determining future machine conditions, enabling e.g. the determination of the next date of operating a machine – Θd;
c) genesis – as the process of reconstructing the history machine conditions, e.g. with a view to estimating machine condition in the past;
Then, it enables:
a) determining the technical condition of the machine in real time on the basis of diagnostic findings. It enables condition control and the location of damage in case of machine dys-function;
b) predicting machine condition in the future on the basis of incomplete history of results of diagnostic tests. It enables operation to judge the time of reliable machine use or the value carried out by structure in the future;
c) determining machine condition in the past on the basis of incomplete history and the re-sults of diagnostic tests for the estimation of machine condition in the past.
The main tasks for formulating diagnostic technical problem solution, identifying the state of exploitation of machines, include:
a) formulation of the aim of the diagnosis, forecast and genesis of machine condition; b) transition of the machine during exploitation;
c) description of machine condition with the use of trademarks of condition and the relation between trademarks of condition and diagnostic parameters;
d) solving the task of condition diagnosis; e) solving the task of condition forecasting; f) solving problem genesis of condition.
Fig. 1. An outline of the completion of recognizing machine condition in support system The main problems that appear include:
• the choice of “the best” diagnostic parameters describing current condition and their change during the time machine operation;
• appointing a diagnostic test;
• appointing a forecast value of a diagnostic parameter for horizons of the forecast τ1,
sjp(Θb+τ1) with the help of “the best” methods of forecasting and setting the date of
the next diagnosing Θd;
• appointing value genesis of a diagnostic parameter for horizons of the genesis τ2,
yjG(Θb–τ2) with the help of “the best” genesis methods, and estimating machine
con-dition, values of the work performed in the past, or describing the reason for the lo-cated address, while inspecting machine damage.
The conception “the best” used above is coupled with adopting appropriate criteria and be-coming acquainted with these problems and categories optimum solutions. Due to many evalua-tion criteria, these problems have to be considered in categories of the poly-optimum soluevalua-tion, e.g. for individual tasks (local optimum), or for the task of identifying machine condition (global criterion).
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2. Genesis methods of machine technical condition
Improving the exploitation of machines, apart from diagnosing and forecasting, requires also appointing the genesis of machine condition, after which describing the reason for the undesired event during exploitation (damage, breakdown, disaster) most often requires an answer to two questions:
• how did it happened? – the description of the course of event and conditions of its occur-rence;
• why did it happen this way? – the description of the cause of the existing event.
With a view to answering to above-mentioned questions, one can take advantage of the following two approaches:
d) exploration, consisting in collecting knowledge in the area associated with the operation of a machine, on the basis of which causal analysis is possible – consecutive to undesired events;
e) standard, consisting in identifying assignments from the past and describing them. Considering the topic of genesis, it is not possible to demonstrate machine condition superiorities of reliable methods enabling genesis values of diagnostic parameters and estimating the technical condition of machines S(Θ1,Θb). It is possible, however, to apply criteria concerning connected
requirements:
a) the form of genesis (genesis value of diagnostic parameter, estimated machine condition in the past, the value of the work performed by it in the past, the cause of the condition of machine dysfunction or other form of genesis of machine condition);
b) the influence of the change of the level of service of machines and service activities on machine exploitation properties which one should take into account while choosing the genesis method;
c) the possibility of using genesis methods (e.g. quality methods, analytical methods or their appropriate compilation).
Amongst a small number of methods enabling genesis of machine condition, it is possible to single two groups out:
a) quality methods (situational genesis on the basis of information gathered from surround-ings and the expert method on the basis of the report of witnesses);
b) analytical (symptom methods on the basis of the value of diagnostic parameters from the time interval.
In case of situational genesis, the cause of the presence of dysfunction is determined on the basis of the inspection conducted directly after the occurrence of the event. The information collected in this way is used for the comparison with situational data incurred in the result model-ling of certain damage.
Expert genesis consists in describing the reason for the existing machine condition on the ba-sis of the event described by witnesses. Industrial cameras enabling the determination of the reason for the arising dysfunction are often used.
Assuming the possibility of the registration of the value of diagnostic parameters (symptom genesis) in time (e.g. in the process of passive – active experiment), a basis of information is received in the form of the motherland of information: the values of diagnostic parameters – states of the machine – operating time. There will probably be a possibility of the statement at the
mo-ment of loss through the machine of the state of the applicability, on the basis of collected data, as well as the inspection of the machine, which could to be the cause of the occurrence of the dys-function of the machine.
3. Optimization methods of machine condition genesis
Optimization of the genesis process of machine condition relies on the choice of “the best” so-lution according to appropriate criteria, for every stage of the genesis process of condition. In connection with the operational research tasks considered above, the choice of one criterion or many criteria is possible.
Multi-criterion optimization is the most natural conception of decision making. The fol-lowing can be distinguished:
a) appointing a set of acceptable solutions X, described stages of which are genesis ele-ments, which requires the formulation of an outline of a scheme of condition genesis; b) determining the criteria function F, for which elements are an exemplification of
require-ments of quality and structural operations of a machine, resulting from the appropriate-ness of the process (character of consuming teams, exploitation factors, structural-qualitative factors, character of outside coercions, demands resulting from formulated purpose genesis);
c) giving the operational research a multi-criterion optimization and “the best” genesis methods;
d) examining the quality of the optimum solution by determining the sensitivity of proce-dures to some factors resulting from the properties of the process of machine operation (which weren't taken into account as elements of the criteria function F);
e) validation of the methodology of appointing the optimum condition genesis with refer-ence to the possibility of using it for machines;
f) drawing up a conception using optimum condition genesis in machine operation.
With a view to solving the above-mentioned problems, it is believed that the most appropriate method of multi–criterion optimization for the construction of the optimum genesis procedure is Pareto method of optimization. In this method, the xo∈X element calls one another X with an optimum solution in the Pareto meaning if and only if in X such an x* element doesn't exist, so Fn (x*) > F (xo) for every n∈N and k ∈ N exists:
Fl (x*) > Fk (xo), (1)
Demands determine the practical application of the optimum xo solution:
• the xo solution should be the only one;
• the xo solution should be a not-dominated solution, provided the harvest of not-dominated
solutions isn't futile (so-called compromise solutions fulfil this demand).
It is carried out by narrowing the set of optimum elements in the Pareto meaning in two aspects: • the choice of the perfect a*∈ RN point which will be regarded as the most desirable score,
defined in case of presenting operational research ( X, F, ≥ ) as: a*
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• the choice of the norm form Ra*(a) of vector (a* – a) of F criterion, determining the
dis-tance of the point, but from the perfect a* point, e.g. under the figure standardized F(•) about standardized criteria of components:
F*
n (x) = (Fn (x))(a* – anmin ), n ∈ N, (3)
in addition, the value of relatively loopy behaviours of individual criteria should be standard-ized in the period (0,1):
0 < (a*
n – Fn (x))(a* – anmin ) < 1, x ∈ X, n ∈ N (4), (4)
or in the form of the norm R(•), with the parameter p ≥ 1 in addition when p=1 a weighed sum of fragmentary criteria is received,
p=2 an Euclidean norm is received.
Achieved result ao∈ A and is the closest to a* result in the meaning “of geometrical distance”
(e.g. point of contact with the circle, with possibly the greatest radius and meaning in a* with the set A).
The presented algorithm of genesis optimization process contains individual stages of ma-chine condition, being at the same time elements of formulating and solving operational research objective appropriately; in addition, one should determine the set of diagnostic parameters of machines and operational research setting for genesis methods of machine condition.
4. Conclusions
At present, we don't have functional genesis methods of machine condition which are possible to exploit in practice (particularly in the aspect of the description of the course and the cause of the existing condition of machine dysfunction), so application was considered situational, genesis expert genesis and symptom genesis.
The most useful symptom method of genesis was accepted, using variable values registered in the process of operation of a machine of diagnostic parameters.
Following the optimization of the genesis process, it is proposed to exploit condition tools of the multi–criterion optimization in the scope of:
• appointing the optimum harvest of diagnostic parameters;
• determining an optimum genesis method of machine condition for appointing the genesis value of a diagnostic parameter;
Bibliography
1. Tylicki, H., Koncepcja systemu rozpoznawania stanu maszyn. XII Konferencja „Wibrotech”, Kraków 2006.
2. Tylicki, H., Wilczarska, J., Bartol-Smardzewska, M., Metodyka diagnozowania stanu ma-szyn. Wydawnictwo Oddziału PAN w Lublinie, 2005.
3. ĩółtowski, B., Cempel, C., InĪynieria diagnostyki maszyn. Warszawa: Polskie Towarzystwo Diagnostyki Technicznej, Instytut Technologii Eksploatacji, 2004.
GENEZOWANIE STANU TECHNICZNEGO W PROCESIE EKSPLOATACJI MASZYN Streszczenie
Zastosowanie w procesie eksploatacji optymalnych metod oceny stanu technicz-nego maszyn jest podstawą automatyzacji procesu rozpoznawania stanu. Wymaga to wielu przedsiĊwziĊü, do których za jedno z waĪniejszych, obok oceny stanu i progno-zowania stanu, uwaĪa siĊ genezowanie stanu technicznego maszyn.
Problematyka genezowania stanu technicznego wymaga przeprowadzenia iden-tyfikacji problemów rozpoznawania stanu maszyny i sposobów ich rozwiązania, oraz okreĞlenie moĪliwoĞci wykorzystania metod optymalizacyjnych do rozwiązania zi-dentyfikowanych i sformułowanych problemów.
Słowa kluczowe: genezowanie stanu technicznego maszyn, parametry diagnostyczne, stan techniczny
*This paper is a part of WND-POIG.01.03.01-00-212/09 project.
Joanna Wilczarska
University of Technology and Life Sciences WIM POIG
