Exploitation Efficiency System of Crane based on Risk Management
Janusz Szpytko
a
and Yorlandys Salgado Duarte
b
AGH University of Science and Technology, Krakow, Poland
Keywords: Risk Management, Stochastic Optimization, Maintenance Process.
Abstract: The subject of the paper is the exploitation efficiency system of overhead type cranes operating in critical
systems, results implementation the control risk management and maintenance scheduling processes. The
study case of the paper is a hot rolling mills system of a steel plant with critical overhead cranes operating
with hazard conditions and continuous operation. The model output is an optimal overhead cranes
maintenance scheduling distribution minimizing the production line risk stopped and the model input is a
digital database structure with historical information related with the operation, maintenance, logistics and
management process of the overhead cranes in the hot rolling mills plant. The transfer function is a stochastic
non-linear optimization model with bounded constraint that assess a risk global-system indicator based on
Monte Carlo simulations.
1 INTRODUCTION
Today’s industry has high levels of automation and
complexity, therefore, decompound the Lego system
into critical pieces simplifies the problem and gives
us the opportunity to focus on a specific process.
The process of degradation is inherent in the
technical system; consequently, control risk
management and maintenance scheduling processes
are increasingly relevant, and the human decision-
making process behind is a target to improve.
Human decision-making process behind of the
control risk management and maintenance
scheduling processes is the coordination of
components maintenance and/or replacement that
make up the system but maintaining risk holistic
and/or clustering objectives defined by the decision
makers.
Coordination of larges combinations, meaning
larges systems, can be a complex problem and
humanly dreadful to find a faster optimal solution.
Mathematically speaking is a nondeterministic
polynomial time NP-complete problem.
As we know, for the search of optimal solutions,
it is needed first, to model the system and its possible
operational scenarios, to make a coherent
coordination. Reason why, software, tools, robots,
a
https://orcid.org/0000-0001-7064-0183
b
https://orcid.org/0000-0002-5085-3170
platforms are needed to perform this coordination
duties efficiently.
In the field of control risk management, we found
the closed-loop engineering (CLE) framework
introduced by (Barari et al., 2009) as a well-stablish
approach for robust and coherent coordination.
Strong references of CLE implementation are
(Gholizadeh et al. 2020) for operational and tactical
decision-making levels to configure a coordinated
supply chain network, (Jerome et al. 2020) for
integration of production scheduling decisions within
a dynamic real-time and (Rui et al. 2020) to assess the
dynamic reliability of repairable closed-loop systems
with the consideration of uncertainties. All of them
are examples of platforms to support robust and
coherent coordination duties.
Following the same research line, in this paper, we
study the control risk management and maintenance
scheduling processes for overhead cranes operating in
a steel plant. An innovated exploitation efficiency
system of crane based on risk management is
proposed to simulate the same process performed in
the time real, but in this case, an optimization
algorithm chooses the best maintenance schedule
given the historical degradation data of the previous
process as a result of machine learning analysis, and
provides the feedback to the entity manager as a
24
Szpytko, J. and Duarte, Y.
Exploitation Efficiency System of Crane based on Risk Management.
DOI: 10.5220/0010123200240031
In Proceedings of the International Conference on Innovative Intelligent Industrial Production and Logistics (IN4PL 2020), pages 24-31
ISBN: 978-989-758-476-3
Copyright
c
2020 by SCITEPRESS – Science and Technology Publications, Lda. All rights reserved
closed-loop control system. Among the cases cited,
the reference (Rui et al. 2020) maintenance decisions
oriented with a novel non-probabilistic reliability
assessment approach is an example close to the
proposal in this paper but in a different system.
Figure 1 describes the block diagram of the
engineering solution proposed, called in this paper as
Integrate Maintenance-e (IMe), e- referring to
electronic or digital.
Figure 1: Risk based Maintenance Management Efficiency
Control System.
In the presented model, the control risk
management effectivity depends on the maintenance
scheduling optimization. By nature, in the literature,
this process is an open problem because engineering
systems increase their complexity and variety every
single day and new researches are needed to fill the
gabs of the challenges.
Maintenance scheduling as a general problem,
can be decomposed essentially by hierarchical levels,
holistic objective (referring to global or integrated
strategies) or multi-objectives (referring to
decentralized strategies), and optimization criteria
cost, reliability, or hybrid approach. Examples are
cost-holistic (Akaria et al., 2019), cost-multi-
objectives sequential (Briskorn et al., 2019) and
holistic-reliability approach (Luo et al., 2019). For
any of the cases, the problem is to find the best
scheduled maintenance sequence of actions for each
component considered in the system.
Generally, the objectives and restrictions are not
well defined because depends on the individual
system requirements. However, as a consensus, the
optimization problem is defined as a multi-criteria
combinatorial problem of non-linear objective
functions with constrains (adding by us stochastics),
and the problem objective is to determine the timing
and sequence of the maintenance tasks periods of
each component analysed. Therefore, the variables x
in a maintenance scheduling problem is represented
by the start time of the maintenance tasks for all the
component considered.
Especially, the paper is focuses on defining the
exploitation efficiency system based on risk
management for overhead cranes under operation into
the steel plant, and in a specific scenario description
as an application example. The idea is to contribute
with an example of overhead cranes adaptation to the
digital industry and with a clear union of control risk
management with maintenance scheduling.
The motivation of the investigation starts with the
identification of organization issues in the dedicated
maintenance department of the steel plant, which is
focusing on cranes operation into the continuous
transportation process in the hot rolling mills system.
In this system, overhead cranes are critical devices,
because in case of failure or maintenance the
production line can stop.
The department have a risky situation also when a
scheduled maintenance of selected cranes (existing as
hot redundancy) is performed and at the same time an
unexpected fail of cranes in use in the system are
reported.
In practice, we consider a set of cranes in the
operation process of the plant. We learn about the
results of technical degradation of cranes under the
operation processes, implementation results of
dedicated to cranes maintenance focused procedures,
as well as the existing environmental conditions and
applied plant operation strategies.
The presented exploitation efficiency system
based on risk management for proper engineering
decision making and controls, considers the plant
operation strategies. The system platform helps also
to adapt crane maintenance processes to the existing
operation problems and events and available
resources, as well as unexpected critical events into
the hot mill system.
The IMe platform supports decision-making
processes aimed at minimizing the risk of the
operational safety of cranes and the risk of losing their
operational reliability, as a result of the degradation
of the structure and utility functions of devices and
the possibility of a combination and association of
events and failures resulting in a safety hazard under
operation processes.
In our case, maintenance-task distribution or
maintenance scheduling solution implemented is a
holistic-reliability approach.
The approach was selected holistic for an easy
interpretation of the maintenance impact on the
system by the entity manager (unique indicator), and
reliability, because overhead cranes in a steel plant
are critical devices working in a continuous process,
by construction, the system must be reliable.
In this paper, the approach selection is driven by
individual system requirements and the contribution
is strongly guided by the CLE framework (Barari et
al., 2009).
Conceptually, the proposed model considers two
layers (live and digital) guided by independent
Exploitation Efficiency System of Crane based on Risk Management
25
processes that are eventually are combined by the
platform.
Live layer presents manufacturing process in the
real time, representative by dedicated exploitation
data. Historical data from the crane operation process
is supplemented with current data obtained from the
transport process carried out by cranes, which are
available results with the use of sensors.
Digital layer based on Digital Twin (DT)
processes replaces human decisions making by risk
managements tools, incorporating optimization of the
decision making involved.
The first process concerns the registration of the
process of technical degradation of cranes
exploitation parameters and losses their functional
functions, because of the implementation of specific
transport processes.
The second process is oriented towards planning
service processes with the use of specific limited and
available resources, their correlation with planned
overhauls of a technological manufacture line and
their adaptation to the occurring unplanned events
and expectations. The process of planning service and
maintenance processes is accompanied by an
optimization process focused on the planned
efficiency of the production system and minimizing
possible production losses.
Such decision supporting model platform, based
on parallel real and digital processes, helps to design
optimal maintenance strategies dedicated to the
selected cranes, including type of the activities and
timetable, and needed resources. Is holistic, safety
and reliability oriented, includes quality and quantity
cranes representatives’ parameters for decision
making processes.
In practice, the input of the model is a database
structure created for maintenance purposes based on
historical degradation data of all the system
components, previous planned process, system
structure, etc., collected by SCADA (Supervisory
Control And Data Acquisition) and SAP (Systems,
Applications and Products in Data Processing)
systems, in fact, available historical information
related to the maintenance scheduling management
process.
The output of the model in our case is to provide
to the entity manager a faster and optimal online
decision-making process as a closed-loop control
system (CLCS).
Once the maintenance scheduling management
process is optimal (supporting by live and digital
layers), as a result, the holistic operational efficiency
in the plant increases. In the following sections, the
model is fully described using a specific scenario.
The document is organized as follows; firstly, the
mathematical formulation of the optimization
problem is presented with the constraint set and the
flow diagram, as well as all the equations and
assumptions of the proposed model organized in
subsections. Following the same idea, in next sections
the scenario (parametrization) and methods (solution)
are described, discussed, and validated. Finally, some
important conclusions are drawn to highlight
potential outcomes in this research area.
2 IME-PLATFORM:
MATHEMATICAL
MODELLING
The proposed model aim is to minimize the expected
value of the convolution function, between the
overhead cranes loading system capacity distribution
function of the steel plant impacted by maintenance
scheduling and the necessary load capacity
distribution function of the production line. The
model is defined below:
{
}
,1 , ,1
,1 ,1 , 1 ,
min [ ]
where :
(,)
(, , )
( , , , , ) with
subject to:
0 Simulation Window ( )
i
iikik i
i i ik ik
ER
RfXY
XftLC
LC f t TTM TDM x x TTM
TTM TTM TTM TDM
→=
<< + +
(1)
The stochastic non-linear optimization model
with bounded constraints proposed for the overhead
cranes’ maintenance scheduling problem solution in
the steel plant present only continuous variables x =
TTM
i,1
(time to maintenance) and is defined in the
model constraint intervals. The independent variable
of the objective function to be optimized x = x
1
, x
2
,
…, x
NMi
depends on the quantity of maintenance task
NM
i
to be coordinated for each overhead crane.
The optimization variables are only the start times
for the first maintenance of each overhead crane
TTM
i,1
. Once TTM
i,1
is established, the remaining
TTM
i,k1
are calculated adding the corresponding
maintenance intervals, which are invariable and
depends on the operation time between two
consecutive check-ups.
Figure 2 shows the conceptual flow diagram
implemented to solve the problem. The flow diagram
is linear and only has two conditioning moments, first
one to guarantee the simulations error criterion, and
IN4PL 2020 - International Conference on Innovative Intelligent Industrial Production and Logistics
26
second one to guarantee the best solution of all the
scheduling proposals evaluated.
Figure 2: Flow optimization model.
The problem is solved as follows: the
optimization algorithm proposes a set of TTM
i,1
and
N
s
Monte Carlo simulations are performed to
determine N
s
values of risk (r
1
, r
2
, …, r
Ns
). The Risk
mean E[R] and variance V[R] are determined from (r
1
,
r
2
, …, r
Ns
) and the error criterion is checked. If the
desired error is not achieved, N
s
is augmented and the
Monte Carlo simulations are repeated for the same set
of TTM
i,1
. When the desired error is achieved the
process is repeated for another set of TTM
i,1
. This is
done several times (1, 2, 3, …, N) determining
decreasing values of Risk mean E[R
1
], E[R
2
], …,
E[R
N
]. The set of TTM
i,1
leading to the lowest Risk
mean (E[R
N
]) is the solution.
The optimization model construction formalized
in this section is structured in two steps. First one, the
production-line-capacity and overhead-cranes-
capacity stochastic mathematical models for a steel
plant are defined. The model used for the overhead
cranes has two reliability states and considers random
faults intrinsic to these systems, faults repair times
and operation standards. Second one, the Monte Carlo
simulation model used to estimate the risk indicator
(Capacity Loss) is formalized.
2.1 Production Line Capacity
Modelling
In a continuous production process, always the
devices target function, at all the hierarchical levels is
to be available. Redundancies for critical devices are
crucial in continuous process to obtain high reliability
performance, therefore, as an example the steel plant
have more overhead cranes than needed.
In this paper based on a steel plant scenario, we
define the production line capacity dependent on the
total overhead cranes loading capacity of the system.
In the proposal model, we call this parameter η -
Production line efficiency because is an indicator
between [0, 1] and measures the relation between
minimum availability of overhead cranes required to
secure the production line and total overhead cranes
loading capacity of the system.
In addition, for maintenances purposes also, but
not related with the overhead cranes system, the steel
plant need to stop the production line N
SPL
times,
therefore two additional parameters STD
k
(stooped
time duration) and TBS
k
(time between stooped) are
introduced into the model. As a result, the production
line capacity is defined as follows:
1
111
1
11 11
if
()
0if
OC
N
mm
ikk
ikk
mm m m
kk kk
kk kk
LC t TBS STD
Yft
TBS STD t TBS STD
η
θ
===
== ==
<+
==
+≤<+

 
(2)
where t is time, θ is a set of parameters, in this
case θ = {η,
i
L
C
, TBS
k
, STD
k
} and m = 1, 2, 3, …,
N
SPL
.
2.2 Overhead Cranes Modelling
Overhead cranes operation is continuous, eventually
fails and is repairable. This random behavior can be
described from distribution functions fitted to
historical degradation data. Considering the operation
effectiveness of the overhead crane, in this paper, we
fix that the system and its components have two states
z = 0, 1 and between them transition rates are defined
depending of the distribution function selected in the
simulation approach. The probability of moving from
one state to another depends on the failure or repair
rate of each overhead crane.
In the two-state model, the overhead cranes are
considered fully available (z = 1) or totally
unavailable (z = 0). The stochastic loading capacity
LC
D
i
at the time instant t of an overhead cranes i is
determined by the TTF
i,k
(time to failure), TTR
i,k
(time
to repair) and
i
L
C
(nominal loading capacity). The
parameters allow to simulate with (3) the behavior of
LC
D
i
generating k-th independent random numbers
from distribution functions fitted to historical
degradation data. Therefore, the model proposed to
simulate the stochastics overhead cranes loading
capacity is defined below:
Exploitation Efficiency System of Crane based on Risk Management
27
1
,,
11
1
,, ,,
11 11
if
()
0if
mm
iikik
kk
D
i
mm m m
ik ik ik ik
kk kk
LC t TTF TTR
LC f t
TTF TTR t TTF TTR
θ
==
== ==
<+
==
+≤<+

 
(3)
where t is time, θ is a set of parameters, now θ =
{
i
L
C
, TTF
i
,
k
, TTR
i,k
} and m = 1, 2, 3, …, N
RNi
knowing that N
RNi
depends on the Simulation Window
used in the optimization model. The k-th independent
random numbers generated from distribution
functions fitted to historical degradation data
guarantees the follows restriction:
,,
11
Simulation Window
mm
ik ik
kk
TTF TTR
==
+≥

.
On the other hand, one of the factors that affects
the overhead crane loading capacity, is not stochastic
and is not considered a random phenomenon, it is
type maintenance process, and in this paper, we
assume independent from the previous one during the
simulation. The maintenance is contemplated within
the strategies of a steel plant because it guarantees
cranes life cycle. Maintenance is the activity designed
to prevent failures in the production process and in
this way reduce the risks of unexpected stops due to
system failures. In a steel plant, to perform some
maintenance tasks it is necessary that the overhead
crane does not work, and this causes Capacity Loss in
the steel plant. Due to this reason, it is advisable that
this maintenance task be carried out at the time of the
year where the least frequency of system potential
failure exists, so that equilibrium and adequate
environment are secured in the steel plant. To
consider this effect, in this paper the parameters
TTM
i,k
(start time to maintenance) and TDM
i,k
(time
duration maintenance) are introduced in the equation
(4), then we combine the equation (3) and (4) using
junction symbol & representing the AND logic, as we
show below:
1
,,
11
1
,, ,,
11 11
if
()
0if
nn
iikik
kk
M
i
nn n n
ik ik ik ik
kk kk
LC t TTM TDM
LC f t
TTM TDM t TTM TDM
θ
==
== ==
<+
==
+≤<+

 
(4)
where t is time, θ is a set of parameters, now θ =
{
i
L
C
, TTM
i,k
, TDM
i,k
} and n = 1, 2, 3, …, N
MTi
; and
as a combination consequence of both process LC
i
=
LC
D
i
& LC
M
i
knowing that the junction symbol & is
used for the AND logic. As a modelling result, the LC
i
variable consider both process, degradation (D) and
maintenance (M).
Once we know the LC
i
for each overhead crane,
we use reliability block diagrams to compose the
system loading capacity. A technical complex system
structure can be reduced in a series-parallel reliability
block diagram, and the steel company is not the
exception. Usually, the steel companies have huge
warehouses, and inside overhead cranes are installed,
therefore the series-parallel configuration of the
cranes follows the structure of the warehouse. Based
on the configuration of the warehouse is possible built
the system block diagram, and as a result, the system
simulation process is consequent with the relation
between cranes.
In order to consider the block diagram structure of
the system, we propose a simple rule in this paper.
Following the generic series-parallel structure, when
two or more overhead cranes are in series (Crane
1
&
Crane
2
& … Crane
N
) the junction symbol & is used
for the AND logic, while the symbol || is used for the
OR logic when the overhead cranes are in parallel
(Crane
1
|| Crane
2
|| … Crane
M
), therefore, during the
simulation process of the system when two or more
overhead cranes are in series, if one crane fail, all the
chain of cranes in series stop, overwise, when two or
more cranes are in parallel, if one crane fail, the
redundancy system is still working.
As a conclusion, we simulate independently the
LC
i
for each overhead crane i, then we combine all
the N-series cranes in each M-parallel chain of cranes
using the junction symbol &, and then we aggregate
all the equivalent M-parallel chain of cranes using the
junction symbol || to obtain the system loading
capacity X. Below, we define the general notation for
the overhead cranes system loading capacity:
()( )
,
11
|| &
MN
mn
mn
XLC
==
=
(5)
2.3 Risk Indicator Modelling
The risk function denoted as R can be generated with
the sum of X + Y random, independent, and non-
negative variables. By definition, the product of R(s)
= P(s)Q(s) is defined with the generating function
()
0
j
j
j
Ps ps
=
=
of X and the generating function
()
0
j
j
j
Qs qs
=
=
of Y. Consequently, the generating
function of R(s) is generally defined by the
convolution formula:
1
k
kjkj
j
rpq
=
=
(6)
where p
j
and q
j
are the generated sequence from
P(s) and Q(s) respectively.
In this investigation, X is the overhead cranes
system loading capacity distribution function affected
by the maintenance scheduling defined in (5), and Y
IN4PL 2020 - International Conference on Innovative Intelligent Industrial Production and Logistics
28
is the production line capacity defined in (2). The risk
function is denoted in this investigation as R and is
defined below as a convolution product between (5)
and (2):
1
if
0if
T
tt tt
t
tt
YX XY
R
X
Y
=
−<
=
(7)
where t = 1, 2, 3, …, T (Simulation Window).
The expected value of the risk function E[R] is
defined in this paper as Capacity Loss. In this work,
to estimate E[R] the Monte Carlo simulation method
is used. The convergence process is fluctuating in this
method. However, the error level decreases when the
number of samples increases, according to the law of
large numbers. In this method it is not practical to run
a simulation with many samples, because more
calculation time is required. Therefore, it is necessary
to balance the required precision and the calculation
time with a stop criterion. This criterion guarantees
that the simulation continues, until the risk indicator
has the precision specified for the simulation. The
parameter used as stopping criterion in the method is
the coefficient of variation β defined below.
[] []
[] [] [] [] []
[]
RR
CapacityLoss ER ER ER ER ER
ER N N
σσ
β
(8)
3 IME-PLATFORM:
MATHEMATICAL
PARAMETERIZING
The system analyzed have 33 overhead cranes with
loading capacity between 2-80. Depending on
operation time and loading capacity, each crane has
weekly, every two weeks or monthly inspection
frequency as we describe in the Table 1.
Table 1: Inspection frequency relation.
Capacity
(tons)
Inspection
frequency
TTM
(hours)
TDM
(hours)
50T – 120T Weekly 168 3
32/8T – 20T
Every 2
weeks
336 3
5T-8T Monthly 672 3
The inspection frequency are maintenance tasks,
therefore in the model are considered as TTM
i,k
and
TDM
i,k
,, where k-th is the number of inspections for
each overhead crane depending on the simulation
window. In the historical degradation data case, the
fitted distribution function for each crane is a result of
the fitting-selection decision making flow diagram
from previous work.
In order to parameterize the degradation process
of the system, the Table 2 summarize all the finals
distributions selected for each overhead crane.
Table 2: Degradation distribution parameters.
Crane
ID
Failure time
distribution
Repair time
distribution
807 Exponential
µ = 743.80
Lognormal
µ = 1.07; σ = 0.93
808 Weibull
a = 1796.93; b = 0.60
Generalized Pareto
k = -1.05; σ =
12.56;
θ = 0
809 Gamma
a = 0.54; b = 2607.04
Inverse Gaussian
µ = 6.82; λ = 4.70
810 Exponential
µ = 9184
Exponential
µ = 3.25
870 Birnbaum Saunders
β = 377.02; γ = 2.59
Loglogistic
µ = 0.98; σ = 0.48
871 Weibull
b = 0.64; a = 1060.19
Inverse Gaussian
μ = 2.30; λ = 4.43
1011 Exponential
µ = 3254.86
Exponential
µ = 8.60
1010 Inverse Gaussian
µ = 476.41; λ = 79.40
Inverse Gaussian
µ = 5.9; λ = 1.87
872 Exponential
µ = 2396
Exponential
µ = 6.63
873 Exponential
µ = 5571.4
Exponential
µ = 4.53
874 Exponential
µ = 1189.2
Exponential
µ = 72.5
879 NaN NaN
1001 Weibull
b = 0.82; a = 458.66
Lognormal
µ = 1.44; σ = 1.14
1000 Burr
α = 2318.3; c = 0.75; k =
3.15
Inverse Gaussian
µ = 10.44; λ = 4.59
1002 Exponential
µ = 3285.9
Exponential
µ = 12.95
1003 NaN NaN
1004 NaN NaN
1005 Weibull
b = 0.70; a = 429.64
Inverse Gaussian
µ = 65.65; λ = 2.93
1006 Exponential
µ = 2534.4
Exponential
µ = 5.07
1007 Exponential
µ = 1125.7
Exponential
µ = 2.6
1008 NaN NaN
1009 NaN NaN
1016 NaN NaN
1021 NaN NaN
502 Exponential
µ = 1478.2
Exponential
µ = 4.38
981 Birnbaum Saunders
β = 508.68; γ = 3.13
Inverse Gaussian
µ = 16.82; λ = 2.11
983 Weibull
b = 0.62; a = 611.51
Inverse Gaussian
µ = 8.52; λ = 3.53
Exploitation Efficiency System of Crane based on Risk Management
29
Table 2: Degradation distribution parameters (cont.).
Crane
ID
Failure time
distribution
Repair time
distribution
985 Generalized Extreme
Value
k = 0.8; σ = 1176.1; µ =
903.95
Inverse Gaussian
µ = 72.79; λ = 2.69
804 Exponential
µ = 4008.8
Exponential
µ = 3.59
813 Burr
α = 1027.3; c = 0.78; k =
2.92
Inverse Gaussian
µ = 22.66; λ = 2.73
815 Nakagami
µ = 0.28; = 2852.2
Inverse Gaussian
µ = 3.88; λ = 2.03
812 Exponential
µ = 8564.6
Exponential
µ = 6.44
811 Exponential
µ = 8803.5
Exponential
µ = 4.18
Note: NaN means non failures registered.
Once we know all the parameters related with the
overhead cranes system capacity, the next step is the
production line capacity. Two essentialise
information, the monthly STD is 12; 10; 16 and 12
hours every week respectively, therefore STB
between them are 168 hours; and the efficiency
indicator is 85% in the simulated scenario.
In the case of the simulation parameters, the
simulation window is one year (8760 hours) and we
assume robust expected value estimation (Capacity
Loss indicator) by Monte Carlo simulation when ε =
0.01.
4 IME-PLATFORM:
MATHEMATICAL SOLVING
The model is fully implemented in MATLAB
(R2019b), a multi-paradigm numerical computing
environment and proprietary programming language
developed by MathWorks and can be running in any
personal computer.
As we describe above, the model has a stochastic
non-linear objective function with bounded
constraints. In order to solve this specific problem,
PSO algorithmic was used because Capacity Loss risk
indicator (objective function value given the
maintenance scheduling) is the results of a
convolution by Monte Carlo simulation, therefore we
do not know the objective function derivate and
Newton's, Lagrange, quasi-Newton or Sequential
Quadratic Programming traditional methods cannot
be used.
Knowing the features of the objective function,
during the model implementation three possible well-
stablished algorithms to solve derivative free
problems were found and tested: GA (genetic
algorithm), PSO (particle swarm optimization), and
Nelder-Mead modified (NMm).
GA as a global searching algorithm, in large
search regions needs numerous evaluations in the
objective function to find the minimum.
NM, by definition is a searching algorithm
without restriction, but during the implementation
was possible bound the independent variables of the
objective function to adapt the algorithm to the
problem (NMm). NM has a limitation related with the
number of independent variables. Independently of
the objective function, when the number of
independent variables is more than ten, the algorithm
rarely finds the global optimum if the initialization of
the search is not accurate.
Given the previous statements, PSO a local
searching algorithm, is the option selected to be used
because behaves better in this particular problem,
finds the solution with less evaluations in the
objective function, and as a consequence, the time
needed to solve the problem is lower than GA. In
addition, the number of independent variables is not
a limitation for this algorithm.
PSO is fully applicable to this problem. PSO
algorithmic used in this investigation is based on the
algorithm described in (Kennedy et al., 1995), using
modifications suggested in (Mezura-Montes et al.,
2011) and in (Pedersen, 2010). PSO algorithm iterates
until it reaches a stopping criterion, in this case, when
the relative change in the best objective function
value is less than 1.0000e-06 (Function Tolerance
described in the diagram flow).
Once the optimization algorithm used on the
solution and the full parameterization are described,
the results of the proposed optimization model given
the steel plant scenario is shown in Figure 3.
Figure 3: Convergence process of the optimization
algorithm.
Figure 3 is the convergence process of the
optimization algorithm and shows how the Capacity
Loss decrease when the maintenance scheduling
change. Proper planned maintenance scheduling
IN4PL 2020 - International Conference on Innovative Intelligent Industrial Production and Logistics
30
process improve the operational efficiency in the steel
plant, and the CLCS guaranty the expected results.
The exploitation efficiency system based on risk
management is valuable for the entity manager
because he/she can decide according to standards risk
level, what would be the best moment in the year to
perform the maintenance process in the system.
Simulation-based approaches are powerful for
modeling stochastic processes with complex
functions, but the time to simulate these processes can
be a limitation with the current computing power. In
our case the average time duration of ten consecutive
simulations performed with an i5 5250U 1.6 GHz
CPU for the described parametrization is [(1.955813
± 0.072131)·Ns·E] seconds.
5 CONCLUSIONS
The paper describes with a parameterized scenario,
how the exploitation efficiency system based on risk
assessment find the optimal overhead cranes
maintenance scheduling in the steel plant.
Experimental results show that presented closed-loop
control model can help to organize the maintenance
scheduling strategy in the steel plant. The paper
solves the assessing risks problem of transportation
process in the steel plant through the simulation-
based approach which considers the relationship
between random factors (historical degradation data
fitted by machine learning framework) during the
production process and maintenance scheduling
process (planned process, making-decision
framework).
The presented model has the advantage of
minimum set of data needed for robust decision
making, but two fissures are in place, the model is a
local focused problem solution (unique), means, we
do not have any comparative reference to assess the
model, just validations by steps and study cases, and
the time because we use simulation-based approach.
The local solution is well accepted by the steel
plant and futures steps of the investigation will
recover the results of the application in practice, but
still remain open the generalization of the proposal in
others system with similar orientation problems.
The presented model opens the way to extensive
simulations under various scenarios and conditions,
with the possibility to be updated in real-time, to
detect anomalies, to control systems and to conduct
accurate diagnostics and prognostics of cranes into
selected scenarios.
ACKNOWLEDGEMENTS
The work has been financially supported by the
Polish Ministry of Science and Higher Education.
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