This paper presents an advisory expert system to assist the process of constructing the hydrodynamic torque converter. The system has been constructed using program Delphi 7 Enterprise in Object Pascal. The system includes three types of means of transport, a car, a rail bus and a working machine

Kęsy, Andrzej

Migus, Marcin

Osowski, Karol

Portal Czasopism Naukowych (E-Journals)

 * MSc. Karol Osowski, prof. PhD. Eng. Andrzej Kęsy Institute of Applied Mechanics and Energetics, 
Faculty of  Mechanical Engineering , Kazimierz Pulaski University of  Technology and Humanities 
in Radom.
** PhD. Eng. Marcin Migus, The State School of Higher Education in Sandomierz.
KAROL OSOWSKI*, MARCIN MIGUS**, ANDRZEJ KĘSY*
EXPERT SYSTEM FOR SUPPORTING THE 
PROCESS OF HYDRODYNAMIC TORQUE 
CONVERTER CONSTRUCTION
SYSTEM EKSPERTOWY WSPOMAGAJĄCY PROCES 
KONSTRUOWANIA PRZEKŁADNI HYDROKINETYCZNEJ
A b s t r a c t
This paper presents an advisory expert system to assist the process of constructing the 
hydrodynamic torque converter. The system has been constructed using program Delphi 7 
Enterprise in Object Pascal. The system includes three types of means of transport, a car, a rail 
bus and a working machine.
Keywords: expert systems, computer aided design, hydrodynamic torque converter 
S t r e s z c z e n i e
W artykule przedstawiono doradczy system ekspertowy wspomagający proces konstruowania 
przekładni hydrokinetycznej. System zbudowano z użyciem programu Delphi 7 Enterprise w 
języku Object Pascal. W systemie tym uwzględniono trzy rodzaje środków transportu,  w któ-
rym przekładnia hydrokinetyczna pracuje: samochód osobowy, autobus szynowy i maszynę 
roboczą. 
Słowa kluczowe: systemy ekspertowe, komputerowe wspomaganie konstrukcji,  przekładnia 
hydrokinetyczna
TECHNICAL TRANSACTIONS
MECHANICS
1-M/2013
CZASOPISMO TECHNICZNE
MECHANIKA
286
Symbols
h
75
 – economic range of operation
h* – maximum efficiency
cp – computational durability
λM,i – moment coefficient 
α1, α2 – damping factor for pump and turbine impellers
S – execution cost
g – metal consumption factor
id0 – dynamic transmission ratio
np – idle gear loss coefficient
iM – coefficient of torque limit
λA,i – coefficient of axial force
iw – coefficient of speed reduction
p – permeability
X – coefficient of stiffness performance
β11 – blade angle at the entrance of the pump impeller
β12 – blade angle at the exit of the pump impeller
β21 – blade angle at the entrance of the turbine impeller
β22  – blade angle at the exit of the turbine impeller
β
31 
– blade angle at the entrance of the stator impeller
β
32
  – blade angle at the exit of the stator impeller
r12 – radius of the average line at the exit to the pump impeller
r21 – radius of the average line at the entrance to the turbine impeller
r22 – radius of the average line at the exit to the turbine impeller
J1, J2 – moments of inertia of the input shaft
c1, c2 – stiffness of the input shaft
l2 – length of the average line
1. Introduction
A hydrodynamic transmission system (HTS) is a part of the propulsion system in 
the ground transportation using the kinetic energy of the working fluid. No permanent 
connection between the input shaft and the output shaft causes no shock loads transferred 
from the working tool to the propulsion system. The main advantage of the HTS is shifting 
in relation to the applied load. Furthermore, it effectively reduces the dynamic load and 
damping vibration, thus highly increasing the durability of the propulsion system [1]. One 
of the major disadvantages of the HTS is low maximum efficiency and narrow range of 
high efficiency as a function of the speed ratio. The basic element of a HTS consists of an 
hydrodynamic sub-assembly which includes: torque converters, clutch or brake. The most 
complicated component in the design is the hydrodynamic torque converter (HTC) which is 
composed of three impellers:  pump, turbine and the stator as it is shown in Figure 1.
287
The impellers consist of blades that with together the housing create the work area for the 
working fluid.
The introduction of modern low-speed engines using alternative fuels, the requirement 
of exhaust emissions reduction and the increase of the efficiency of the propulsion system 
reducing fuel consumption means that the torque converter design process is very current and 
important. Too low accuracy of existing mathematical models results in a large discrepancy 
between the requirements and the resulting characteristics of the HTC. The failure to comply 
with the prescribed requirements results in the deterioration of the characteristics of the 
propulsion system and forms of economic losses.
The development of the methodology supporting the process of constructing the HTC 
by using expert system can resolve the existing problems of the construction. The benefits 
of using this solution can include not only economic aspects in the form of increasing the 
efficiency, but also the optimal choice of torque converter for a given mode of transport.
Expert systems are complex computer programs that use knowledge derived from subject 
matter experts sources. They consist of three main components: the interface, inference 
engine and a knowledge base. Such systems are increasingly being used in the design and 
operation of machines and equipment. They can be divided into advisory, diagnostic and 
decision-making systems. Are widely used in supporting the construction process advisory 
systems [3], their main task is to solve a problem using the knowledge contained within the 
database.
This paper presents an advisory system for supporting the process of design the HTC.
Fig. 1. Construction of the hydrodynamic torque converter [2]: P – pump impeller, T – turbine 
impeller, K – stator impeller
Rys. 1. Budowa przekładni hydrokinetycznej [2]: P – koło łopatkowe pompy, T – koło łopatkowe 
turbiny, K – koło łopatkowe kierownicy
288
2. Advisory expert system to assist in the process of designing 
a hydrodynamic torque converter
The presented system in the paper the which support the design of a HTC is an advisory 
expert system software based on the collected data [4]. The system has been developed using 
Delphi 7 Enerprise software with the help of object-oriented programming language ‒ Object 
Pascal. The result of the working system is the choice of the optimum design solution for the 
design of a HTC. Solving the decision-making problems in the system is done by selecting:
– optimal torque converter evaluation index for the predefined means of transport,
– optimal design parameters having an impact on the rate of the highest evaluation,
– field variation of the optimal design parameters.
The diagram of the system in the form of a decision tree is shown in Figure 2.
The selection of the optimal values  of the assessment indicators, construction parameters 
and their ranges of variation have been implemented for a passenger car, a rail bus and 
a working machine.
A knowledge base of the advisory expert system to support the process of designing the 
hydrodynamic torque converter has been developed on the basis of domain subject matter 
experts opinions and professional literature in the field of HTS such as: scholarly articles, 
books, standards, patents. The knowledge base includes:
– assessment indicator impact on a means of transport,
– the impact of construction parameters on the assessment indicators,
– ranges of the construction parameters variability.
The knowledge base has been divided into various sources of data provenance. The data 
obtained during the point assessment method as well as the data from books, articles, JCR 
and standards [5] has been implemented. The data coming from various literature sources 
has been divided into experimental and theoretical ones. In addition, arbitrary coefficients 
of confidence have been introduced for all the data. A division of the knowledge base 
fragment is shown in Figure 3.
Fig. 2. A decision tree system supporting the process of designing a hydrodynamic torque converter
Rys. 2. Drzewo decyzyjne systemu wspomagającego proces konstruowania 
przekładni hydrokinetycznej
289
The inference engine retrieves data from a knowledge base with some weights. The value 
of “1” is assigned to the data coming from the books, the value of “0.8” to the articles of the 
JCR and the value of “0.5” to other literature sources.
3. Indicators assessment and design parameters
Completely different working conditions of ground transportation cause that the 
propulsion system is subjected to different types of resistance, and hence there are various 
types of loads. The HTC design requires the determination of the requirements for a given 
means of transport, including the expected load, or cooperation with the propulsion system. 
To ensure the optimal design the following requirements kinematic, dynamic, productive, 
economical and exploitation ones should be taken into account in order to ensure the optimal 
design. Assessment indicators have been introduced to check if HTC meets the requirements 
and to assess the impact of design parameters on the design process [2, 5]. When selecting 
a HTC for a given means of transport which operates in very specific conditions, the 
assessment indicator is to achieve its optimal value.
Assessment indicators chosen for the HTC which have been subjected to the expert 
point assessment method [5–7] have been selected they are affected by a large number of 
construction parameters:  h
75
, h*, cp, λM,i, α1, α2, S, g, id0, np, iM, λA,i, iw, p, X. Next the 
indicators have been evaluated by subject – matter experts. The level of validity of the 
assessment indicators for a given means of transport using the point assessment method [5] 
has been evaluated by experts. The indicators have been assessed on the scale 0 to 180. 
The results are shown in Table 1.
For each means of transport three assessment indicators with most points have been 
selected and they have been implemented to the knowledge base of the advisory expert 
system.
Fig. 3. A division of the knowledge base fragment
Rys. 3. Podział fragmentu bazy wiedzy
290
In order to obtain optimum values of the HTC assessment indicators is the structural 
parameters directly affecting the assessment indicators must be changed. Design parameters 
with greatest impact on the assessment indicators evaluated by means of the assessed using 
point assessment expert method [4, 6], have been selected. They are: β22, β32, β12, r12, J1, r21, 
r22, J2, β21, β11, c1, c2, β31, l2.
T a b l e  1
Assessment indicator impact on a selected means of transport
Passenger car Rail bus Working machine
h
75
148 176 164
h* 158 158 174
cp 134 98 78
λM,i 88 122 112
α1, α2 111 95 100
S 82 68 75
g 123 114 102
id0 172 148 56
np 48 68 126
iM 92 75 93
λA,i 116 46 69
iw 77 123 112
p 58 88 148
X 66 48 96
The parameters were subjected to subject matter experts evaluation. The experts assessed 
the impact of various design parameters on the indicators [5] by using the point assessment 
method. The parameters were assessed on 0 to 180 points scale. The results are shown 
in Table 2.
Three design parameters with the highest score have been selected and implemented 
to the knowledge base of the advisory expert system.
The ranges of design indicator variability have been selected on the base of current 
HTC construction and they have been evaluated by subject matter experts on 0 to 180 scale. 
The results are shown in Table 3.
291
T a b l e  2
Design parameters impact on the indicators  
of the hydrodynamic torque converter
h
75
h* id0 p
β22 168 162 128 118
β
32
172 143 166 122
β12 162 140 149 136
r12 112 98 85 75
J1 88 48 102 98
r21 78 66 59 66
r22 67 104 100 88
J2 74 62 84 60
β21 166 122 116 162
β11 168 138 141 144
c1 112 110 66 78
c2 88 90 110 94
β
31
175 144 170 128
l2 66 50 65 70
T a b l e  3
Ranges of design of parameter variability
Range I Range II Range III Range I Range II Range III
β22 129–139 139–148 148–160 β21 30–45 45–50 50–75
Rating 122 164 125 Rating 149 88 138
β
32
20–30 30–40 40–50 β11 90–102 102–114 114–130
Rating 158 98 48 Rating 111 166 102
β12 75–100 100–125 125–150 β31 70–92 92–114 114–140
Rating 74 148 134 Rating 66 165 78
4. The result of the system performance
The optimal design solution suggested by the described expert system for the HTC 
is following:
– for a passenger car – assessment index p and the construction parameter β12 (75º – 100º),
– for rail bus assessment index id0 and the construction parameter β12 (125º – 150º),
– for a working machine – evaluation index h* and the construction parameter β32 (20º – 30º).
292
5. Conclusions
1. The expert system for each means of transport chooses the assessment indicator which is 
to achieve the max. The process is carried out by choosing the design parameter and the 
variability range of this parameter.
2. Inference system is based on the data contained in the knowledge base.
3. The knowledge base is separated from the rest of the program, which allows for continuous 
modification and the data completion.
R e f e r e n c e s
[1] Kęsy A., Kęsy Z., Damping  Characteristics  of  a  Transmission  System  with  a  Hydrodynamic 
Torque Converter, J. of Sound and Vibration, 16/3, 1993.
[2] Kęsy A., Modele  bryłowe  w  konstrukcji  podzespołów  hydrokinetycznych, Wydawnictwo 
Politechniki Radomskiej, Radom 2012.
[3] Pokojski J., Systemy doradcze w projektowaniu maszyn, WNT, Warszawa 2005.
[4] Osowski K., Migus M., Kęsy A., Assumptions for Expert System Creation to Assess Durability 
of Hydrodynamic Transmission System, The XIIth International Scientific IFToMM Conference 
”Tribology and Reliability”, Sankt Petersburg 24–26 October 2012, CD, 2012.
[5] Stesin S.P., Optymalizacja  parametrów  hydrodynamicznych  przewodów  maszyn  budowlanych 
i drogowych, Budowa maszyn, Moskwa 1996 (tłum. autor z cyrylicy).
[6] Kęsy A., Numeryczna  identyfikacja  i  optymalizacja  napędów  hydrokinetycznych  środków 
transportu, Wydawnictwo Politechniki Radomskiej, Radom 2004.
[7] Kęsy Z., Kęsy A., Madeja J., Identyfication of Hydrodynamic Torque Converter Controlled  by 
Physical Properties of Working Fluid, Int. Conference „Modern Practice In Stress and Vibration 
Analysis”, Dublin 1997.


Expert system for supporting the process of hydrodynamic torque converter construction

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Expert system for supporting the process of hydrodynamic torque converter construction

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