Article citation info:
Homišin,
J. Partial results of the grant project: „Research
and application of universal regulation system in order to master
the source of mechanical systems excitation”. Scientific Journal of Silesian University of Technology. Series
Transport. 2015, 89,
27-36. ISSN: 0209-3324. DOI: 10.20858/sjsutst.2015.89.3.
Jaroslav HOMIŠIN[1]
PARTIAL RESULTS OF THE GRANT PROJECT: „RESEARCH AND APPLICATION OF
UNIVERSAL REGULATION SYSTEM IN ORDER TO
MASTER THE SOURCE OF MECHANICAL SYSTEMS EXCITATION”
Summary. In general terms the mechanical systems (MS) means the
system of driving and driven machines arranged to perform the required work. We
divide them into MS operating with constant speed and MS working with a range
of speed. In terms of dynamics we understand MS as a system of masses connected
with flexible links, it means systems that are able to oscillate. Especially
piston machines bring heavy torsional excitation into the system, which causes
oscillation, vibration, and hence their noise. Governing of the torsional
vibration, as a source of MS excitation, on a basis of results of our
research, can be achieved by applying a pneumatic coupling tuned by the
proposed universal control system. On this basis, it can be concluded that with
given connection a new continuous tuning method in steady state a connection of MS is created.
Keywords: mechanical system, vibration
and noise of mechanical systems, governing the source of mechanical systems
excitation, control system, continuous tuning (tuning during the operation) of
mechanical systems
1. INTRODUCTION
Any
MS in terms of how we understand the dynamics of the system means masses
connected with flexible links between them, it means systems that are able to
oscillate. Piston machines, which are classified as either MS drivers or driven
units, bring to those systems extensive torsional vibration. This means that MS
with internal combustion engines, compressors and pumps can be characterized as
torsional oscillating mechanical systems (TOMS). In the range of operating
speed it can occur a very intensive resonance between the excitation
frequencies (reciprocating machines) and the natural frequency of the system.
Consequently, there comes to vibration and related over-stress in the whole MS.
Excessive dynamic stress often causes malfunction of various parts of the
system, such as:
o
shaft fatigue fractures,
o
gear-box failure,
o deformation
and failure of flexible couplings etc.
Therefore, applies the rightful need to control their dangerous
torsional vibration.
2. SCIENTIFIC
GOALS OF THE PROJECT
The overall objective of the presented project will be the research,
application and analysis of the universal control system function to ensure the
governing of the source of excitation in a different types of MS. Among
the primary source of MS excitation belongs torsional vibration. Governing the
source of MS excitation will be provided by a new way, which consists of
continuous tuning, it means tuning during operation in steady state conditions,
by patents [1], [2]. The essence of a patent [2] is that each MS must contain a
pneumatic coupling (2) controlled by control system (5) (Fig. 1). The pneumatic couplings control with
universal control system implemented by us, whose principle of operation result
from patents [11], [12], [13], will be provided on the basis of closed-loop
control (Fig. 2). Implementation of MS continuous tuning can continuously
adjust the properties of pneumatic coupling to the systems dynamics so that
torsional vibration doesn’t occur during its operation.
Fig. 1. Principle of
continuous tuning in MS
Fig. 2. Regulation circuit for continuous tuning of MS
On a basis of patents fundamental, the MS will be presented by a
laboratory mechanical system (LMS) by Fig. 3 and pneumatic connection will
be realised by pneumatic coupling developed by us. [3], [4], [5] (Fig. 4 and
5).
Fig.
3. Laboratory mechanical system
Fig. 4. Tangential
pneumatic tuner of torsional oscillations of type 4–1/–T–C
To reach the stated objective, it is necessary to focus on the resolution
of the following partial objectives:
1. Realization of the LMS for the
possibility to provide two operating modes, namely work at constant speed and
work with a range of speed;
2. Research and realization of an
universal control system to ensure the governing of the LMS excitation source
in its various working conditions;
3. Development of a control algorithm
to ensure the governing of the LMS excitation source with its continuous
tuning;
4. Realization of experimental
measurements on the LMS focused onto governing the LMS excitation source for
following cases:
4.1. fault-free operation of piston
device of the LMS running in its various working modes,
4.2. case of an accidental failure of
piston device in various working modes of the LMS.
Fig. 5.
Differential pneumatic tuner of torsional oscillations of type 3–2/–D–C
Research in field of the governing of dangerous torsional vibration as a
source of MS excitation, has high economic benefits, because its primary
function is to extend the life and performance of the different parts of the
system, and thereby ensuring their smooth operation without vibration and
noise.
It must be noted that the proposed project solves the control of dangerous
torsional vibration with direct optimization of MS, which is characterized by
continuous tuning of the system during their operation in steady state.
Therefore, the proposed method should be seen
as a way of governing the excitation source of MS, thereby governing the
vibration and noise of the entire plant themselves. In view of the scientific
field Elements of machines and mechanisms, we understand the proposed control
method as a new and very promising contribution to the area of the current
methods for solving the size of the torsional vibration of given systems. The
basic principle of the proposed control method consists in the continuous
tuning of MS with pneumatic couplings - pneumatic tuners of torsional vibration
regulated by the proposed universal control system [9], [10]. Continuous tuning
of MS during operation in steady state is characterized by an appropriate
adaptation of the basic dynamical properties, particularly the dynamic
torsional stiffness of pneumatic tuner to the dynamics of the system.
Adaptation will be provided by the proposed universal control system that forms
a closed-loop feedback control system (on Fig. 2).
Thereby we can continuously change, thus adjust the dynamic properties of
pneumatic tuner to the dynamics of MS, so that dangerous torsional vibration
doesn’t occur during the working mode. Control circuit according to Fig. 2
consists of regulated MS (1–LMS characterized on Fig. 3) and piezoelectric
mechanical vibration sensor (2), which transfers the electrical signal to the controller-microprocessor
(3), proportional to the size of the mechanical vibration ACH.
Microprocessor (3) based on embedded control algorithm will process the
electrical signal, with the intention of seeking the minimum ACHmin,
and control the actuator (4 – as an pneumatic distributor). Controlling the
actuator we regulate an Action variable pS, i.e. by the intake or
discharge of gaseous media we will increase or decrease the pressure in the
pneumatic tuner.
Construction and operation of the universal control system providing smooth
changes of the basic characteristics of pneumatic tuners will result from
granted patents [11], [12], [13].
Another benefit of the proposed project for the
economy, and for the scientific field Elements of machines and mechanisms as
well, is the application of new elements for the proposed way of governing the
MS. These new elements are the different types of air tuners of torsional
oscillations [3], [4], [5] (Fig. 4 and 5) developed and examined by us.
3. THE CONDITIONS FOR REALIZATING THE CONTINUOUS
TUNING OF TORSIONALLY OSCILLATING MECHANICAL SYSTEMS DURING OPERATION IN STEADY
STATE
Continuous tuning of TOMS during steady state operation is currently
not implemented in practice. This is mainly because of its possible
implementation have not been created the basic conditions. Presence of
pneumatic couplings, i.e. an element which during operation is able to change
its basic characteristic properties, especially dynamic torsional stiffness,
enabling the practical realization of continuous tuning of the given systems.
Realization of TOMS
continuous tuning requires to satisfy the following conditions:
§ TOMS must
meet the basic requirements of realization continuous tuning [15], i.e. tuning
the system during its operation in steady state,
§ by the
realization of TOMS continuous tuning it is not necessary to know in advance
its regulatory mathematical model, but it is necessary to know whether the
system objective function (a function of input and output variables) has an
extreme [10], [16], [17].
3.1. Continuous
tuning characteristics of torsionally oscillating mechanical systems
Based on the nature of the patent [15]
follows that the system (fig. 6)
must contain a pneumatic flexible shaft coupling [18] controlled by the
regulatory system [11], [19].
Fig. 6. Schematic representation of the
torsionally oscillating mechanical systems continuous tuning operation
Result of the activities of the
regulatory system is the fact that due to continuous pressure changes of the
gaseous medium in pneumatic couplings intends the change of its basic dynamic
properties, i.e. dynamic torsional stiffness. Changing the dynamic torsional
stiffness we are changing the frequency of natural the system Ω0, i.e. adapting it to
the frequency of the i-th harmonic component of load torque ω so that the system is within the
range of operating mode working not in resonance with any harmonic of exciting
torque, therefore, applied to the condition
Control system (1)
consists of a control (2) and actuating subsystem (3). Control
subsystem (2) is characterized by a microprocessor (5), which is
built into the electronic system ESLER under position 6 on fig. 7 and the piezoelectric sensor
of mechanical vibration acceleration (4) built-in the electronic system
ESLER under the position 9 on fig.
7. Sensor (4), which is located on the mechanical system sends an
electrical signal to the microprocessor (5) proportional to the
mechanical vibrations of the system. Actuating subsystem (3) consists of
an electromagnetic distributor (7 – presented with position 7 on Fig. 7), which is through the control
valve (6) connected to the
gaseous medium container (8 – presented with position 8 on
Fig. 7). Microprocessor (5),
which forms the basic control component of the whole regulatory system (1),
by closing the electromagnetic two-position distributor (7) causes its
shift, so the inlet branch P or the outlet branch T will increase
or decrease the pressure of gaseous medium in the compression volume of pneumatic
flexible shaft coupling.
Fig. 7. Realized torsionally
oscillating mechanical system
4. CHARACTERISTICS
OF THE REALIZED TORSIONALLY OSCILLATING MECHANICAL SYSTEM
Realized torsionally
oscillating mechanical system (Fig. 7)
consists of a driving part (1), a pneumatic flexible shaft coupling
(3) and the driven part (2). Driving part, formed by a DC
electric motor type SM
TOMS load by the compressor is adjusted
(regulated) by throttle valve (11) built into the outlet pipe from
the compressor. It means that system load will be controlled and its load value
will be characterized by the value of the pressure in the outlet pipe pk
obtained from the pressure
gauge (12). In the theoretical analysis and experimental measurements,
we assume pressure moving in the range pk=
20 ÷ 80 kPa, which will respond to a minimum or maximum load torque by
certain operating speeds of the system.
Measurement of the load torque were realized by
the torque transducer type MOM 7934
(10) and simultaneously excited mechanical vibration of the system was
measured by piezoelectric transducers (9), which are part of the
vibration monitoring system ADASH 3600
(5). The measured signals have been recorded and processed by the
electronic system ESLER (6)
developed by us.
Measurements were realized assuming equal
excitation of the compressor cylinders at a constant predetermined speeds n = 200 to 700 min-1. The
gaseous medium pressure in the pneumatic tuners was continuously changed
during the measurements in the range ps
= 100÷ 600 kPa.
5. THE
RESULTS OF THE CONTINUOUS TUNING OF THE TORSIONALLY OSCILLATING MECHANICAL
SYSTEM REALIZATION USING THE ESLER ELECTRONIC SYSTEM
Governing torsional vibration on realized TOMS
by continuous tuning using the ESLER electronic system (Fig. 8) was realized under these conditions:
· at steady state operating mode of
the given system,
· at constant operating speed n = 200 min-1 with
characterized course of dynamic component of the torque load Md,
depending on the gaseous medium pressure in compression volume of pneumatic
couplings in the range ps =
100 ÷ 600 kPa,
· at compressor load pk = 80 kPa,
· at the pre-defined regulating
conditions:
o
the
minimum working pressure of the pneumatic coupling pmin= 100 kPa,
o
maximum
working pressure of pneumatic coupling pmax = 600 kPa,
o
sensitivity
to changes of torque eM = 0,3 Nm,
o
sensitivity
to changes of vibrationeV =
o
the
number of samples to average calculation i = 10 . 103 samples,
o
stabilization
time between the pressure changes ts = 5s.
Based on fig. 4 it can be concluded that
TOMS continuous tuning was started by the gaseous medium pressure in pneumatic
coupling ps = 408 kPa with
current dynamic component of load torque value Md = 4,8 Nm.
Launching the continuous
tuning the process of recording and processing signals from the torque sensor
has begun (10). From the results of signal processing and results of
ESLER‘s control based on the flow diagram by sensitivity to changes of torque eM = 0,3 Nm at times
t = 0 to 30s with a
stabilization time t = 5s, we
achieved the following results by the system monitoring:
o t=0 s, ps=407
kPa, Md=4,8 Nm,
o t=5 s, ps=415
kPa, Md=4,9
Nm,
o t=10 s, ps=423
kPa, Md=5,0
Nm,
o t=15 s, ps=431
kPa, Md=5,0
Nm,
o t=20 s, ps=438
kPa, Md=5,1
Nm,
o t=25 s, ps=447
kPa, Md=5,0
Nm,
o t=30 s, ps=455
kPa, Md=5,3
Nm.
From presented values it can be said that the electronic
system based on specified control parameters for obvious reasons, increased the
pressure in the pneumatic coupling until value
ps = 455 kPa
reaching the value Md = 5,3
Nm. By comparing the previous value of Md = 5,0 Nm, and the next step value, ie, Md = 5,3 Nm based on the
sensitivity to the change of torque eM
= 0,3 Nm the ESLER electronic system had instructed to reduce the
gaseous medium pressure in pneumatic coupling. By reducing the pressure to ps = 440 kPa in time t = 35s the value of torsional
vibration Md = 5,1 Nm
was reached. Further system monitoring of electronic system in timeframe t = 35 ÷ 100s lowered the pressure in
pneumatic coupling still achieving a lower value of torsional vibration.
Searched local minimum was reached by the ESLER electronic system at time t = 85s with a value of pressure in
the pneumatic coupling ps =
340 kPa and dynamic component of torque load Md = 4,1 Nm. Value of
local minimum was confirmed by further measurements when at t = 90 ÷ 100s the previously achieved
values ps = 340 kPa
and Md = 4,1 Nm have
been confirmed. At time t = 100s
the continuous tuning by the ESLER electronic system was stopped.
b)
Fig. 8. Graphs
characterizing the continuous tuning of torsionally oscillating mechanical
system by the ESLER electronic system: a) time graph of the gaseous medium
pressure in pneumatic tuner; b) time graph of the torque load dynamic component
6. CONCLUSION
The sequence of steps to achieve the general
objective of the present project, which is: „Research, application and analysis of the universal control system
functioning for ensuring the governing the source of MS excitation, which
causes vibration and noise the entire installation”, apparent
from the following sub-objectives of the project:
1.
Realization of the MS in the laboratory with the
possibility of its continuous tuning with a pneumatic tuner of torsional
vibrations controlled by an universal control system and with the possibility
of providing its work at constant speed and in a range of operating speeds.
2.
Providing a proper air tuner of torsional
vibrations for the continuous tuning of the LMS.
3. Research, construction and realization of an universal control system for
ensuring the governing the excitation source of LMS in various operating
modes.
4.
Completion, practical modification and
verification of closed-loop system for the realization of continuous tuning of
the LMS in its various operating modes.
5.
Realization of experimental measurements on LMS
characterized by closed-loop control system at its various operating modes.
6.
Evaluation of measured data from LMS
characterized by closed-loop control system at its various operating modes.
Based on
the presented results, it can be concluded that reducing the size of torsional
vibration in any mechanical system is possible by realization of continuous
tuning, thus tuning of the given system during operation in steady state. For
the realization of TOMS‘s continuous tuning during operation at steady state it
was developed a tuning electronic system – ESLER at our institute.
The results
of experimental measurements on realized TOMS under laboratory conditions have
confirmed the fact that with the continuous tuning by using the electronic
system will serve to reduce dangerous torsional vibrations in any torsionally
oscillating mechanical system.
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This paper was written in the framework of Grant
Project VEGA: „1/0688/12 – Research and application of
universal regulation system in order to master the source of mechanical systems
excitation”.
Received 20.04.2015;
accepted in revised form 15.09.2015
Scientific Journal of Silesian University of
Technology. Series Transport is licensed under a Creative Commons Attribution
4.0 International License
[1]Technical
University of Košice, Faculty of Mechanical Engineering, Department of
Engineering for Machine Design, Automotive and Transport, Letná 9, 040 01
Košice, Slovakia, e-mail:jaroslav.homisin@tuke.sk