Article citation information:
Góra, W., Janusz, J., Kłosiński, J. Application of a plc to a laboratory
compressor workshop control system. Scientific
Journal of Silesian University of Technology. Series Transport. 2016, 91, 33-41. ISSN: 0209-3324. DOI: 10.20858/sjsutst.2016.91.3.
Wojciech GÓRA[1], Jarosław
JANUSZ[2], Jacek
KŁOSIŃSKI[3]
application
of a PLC to a laboratory compressor WORKSHOP control system
Summary. In this paper a control system of
air compressors in a university laboratory is presented. The control system,
which is built using the Astraada RCC972 and the GE 90-20 drivers, is an
extension of the two states’ inputs and outputs of Astraada. To visualize the
work stand, the PC computer class and the Proficy Machine Edition (ME) View software
were applied. Selected results from the tests of the built control system
are presented.
Keywords: control system, communication
protocol, visualization of industrial processes
1. INTRODUCTION
Due to the high level of noise emitted
during their exploitation, piston compressors are always placed in separate
rooms, known as compressor workshops [2]. To study this phenomenon, a room was
established within the laboratory of the Division of Mechatronics, in which two
piston compressors were placed. The aim in using these compressors is to deliver
the pressured air that is utilized during laboratory work and classes for
students. The system of controlling the compressor workshop was designed and
built to facilitate remote controlling and monitoring of performance, as well as
effective usage of both compressors.
In the present paper, we describe a system
for controlling an air compressor unit. The system mainly consists of the cooperation
of two air piston compressors. One compressor has the function of a basic device
supplying compressed air, while the second compressor is utilized as an additional
device, supporting the performance of the basic (main) compressor. The application
of an additional compressor in the discussed system ensures the delivery of
pressured air, which offers adequate pressure in case of a temporary increase
in the demand for pressured air. When designing the control system, we take
into account the well-known (standard) hybrid structures of control systems,
which control the process of delivering pressured air [1, 2].
2. CONTROL SYSTEM
The basic assumption, which is made
within the design process of the compressor stand’s control system,
relates to the possibility for the remote monitoring and controlling the air
compressor’s performance in situ,
i.e., in the compression workshop. The system was built utilizing automation
components, devices, subsystems etc. available from the Division of Mechatronics:
namely, an Astraada RCC972 controller, a GE 90-20 controller, thermostatic
gauges of temperature, a pressure converter equipped with a 4-20 mA analogy
connection, a 22A 690V 24VDC contactor, breaking electrovalves based on the
24VDC solenoid (the so-called solenoid valve) and Proficy ME software.
Fig. 1. Scheme of the pneumatic system - layout
in the building
At first, the software needed to control
the performance of the compressors and the visualization of the processes was
prepared. In the built system, the PACSystems RX3i modular controller was
utilized. Regarding the possibility of an application using an Astraada controller
and a GE 90-20 controller, an exchange of the controlling code, which was prepared
using the Proficy ME 8.60 software followed by Cscape-based software, was
performed. The Proficy ME software was utilized for the simulation phase of modelling
and testing. The Cscape programme, meanwhile, allowed for the programming of
the Astraada controller. Additionally, the Logicmaster 90 program was utilized for
programming the GE 90-20 controller in order to service the two-stage (binary,
bi-stated) inputs and outputs.
The simulation stand was built to
test the controlling software, as well as check the correctness in the performance
of controlling visualization possibilities. On the simulation stand, signals
from the pressure converter were replaced by signals from current adjusters, while
the signals from temperature bi-stated gauges corresponded to the signals from the
simulation of bi-stated inputs.
Fig. 2. The structure of the control system
An additional advantage of the
prepared control system is that it is advanced and, in turn, easy to use in
terms of visualization (i.e., the application for PC-type computers). It allows
for simple and intuitive control of the work involving compressor workshops
(compressor installation). Visualization allows users to monitor the work of
the system, as well as display the main parameters of the process. Users with a
higher level of authorization (after logging onto the software/computer
facility) have access to an advanced alarm subsystem, which provides information
about previous alarms, together with the possibility of editing data concerning
these previous alarms. Additionally, visualization delivers information for operators
about currently occurring inadmissible situations, which demand immediate action
of the part of the operator (neglecting an access/authorization level).
3. aSSUMPTIonS FoR AN apPliCaTiON CONTROLLING
AND ViSualiziNG pErFORMANCE OF A CompreSsor
An application for controlling and visualizing
the work modes of a system should have the following goals:
a) Services for users:
-
USER (monitoring
of process parameters, approval of communications/alarms, switching between the
screens)
-
ADMINISTRATOR (access
on a lever of a user USER, changes to ultimate (threshold) values of parameters
and versatile settings, approval of service actions related to the compressors, exchange of filters, oil etc.)
b) Service of
alarms: demand concerning exchange of filters, communication too high, low
temperature, error in communicating the vision gauge of the oil level, pressure
too high/low, improper level of oil
c) Working in
service mode: testing of binary outputs – release of the condensate, breaking
valve, checking fan performance, possibility of simulating pressure values,
temperatures and over-crossing of ultimate values aimed at testing the system
For the first phase, initialization
of the compressor work mode is needed, i.e., it should be launched and run until
the pressure level (in the compressor vessel) of p=600 kPa is reached. The value
CISN>600 kPa is the analogy measurement utilizing the pressure converter. After
this time, the motor of the compressor stops while waiting for the work
mode of AUTO to be switched on. The AUTO work mode can be switched off at any
moment (phase) in the current process by pressing the STOP button, which
is located in the upper part of the panel. To activate the second compressor, the
following activities must be carried out on the stand: the bi-stable button should
be switched on, then the AKTYWACJA option should be activated on the visualization
panel, such that the initialization of the first and second compressors are
activated simultaneously when the switch on the stand is in the ON position, i.e.,
when the needed pressure value (at the level of 600 kPa) is reached.
The second compressor is launched when
both the first compressor is in the AUTO work mode and the value of the
algorithm for the velocity of changes drops below the threshold value.
To realize an application of the Astraada
RCC972 controller, it is necessary to utilize an adequate communication
protocol, which allows for the exchange of data between the main controller and
the simulation subsystem by means of a Proficy ME View script. The Modicon
TCP/IP communication protocol was used, with the aim of facilitating binary
communication between the Astraada and GE90-20 controllers. Adequate time-shifting
was used to avoid conflicts in coding, i.e., simultaneous triggering of two or
more binary codes. The list of control variables is given in Table 1 [3].
Table 1. List of
variables controlling the layout of compressed air power
|
ASTRAASA RCC972 |
Description of variable |
|
%I00001 |
Switching on the stand |
|
%I00002 |
Temperature gauge of compressor no. 1 |
|
%I00003 |
Temperature gauge of compressor no. 2 |
|
%Q00001 |
Signal of binary coding 1 |
|
%Q00002 |
Signal of binary coding 2 |
|
%Q00003 |
Signal of binary coding 3 |
|
%Q00004 |
Signal of binary coding 4 |
|
GE 90-20 IC692MDR741 |
Description of variable |
|
%Q00002 |
Fan no. 1 |
|
%Q00003 |
Fan no. 2 |
|
%Q00005 |
Switching on motor of compressor no. 1 |
|
%Q00006 |
Switching on motor of compressor no. 2 |
|
%Q00007 |
Breaking valve of compressor no. 1 |
|
%Q00008 |
Breaking valve of compressor no. 2 |
4. ApPlicaTION for CONTROLLING aND ViSualizaTION
Due to the introductory assumption,
the controlling application has been written by means of the Proficy ME
software. However, due to some changes in the assumptions, we have converted
the controlling application into Cscape software. The latter is compatible with
Astraada RCC972 controllers. An exemplary fragment of the controlling code after
conversion is presented in Fig. 3.
The GE 90-20 controller, together
with Logicmaster 90 software, has been used in the control system. Its function
is to create an upgraded module of binary (bi-state) outputs for the Astraada
RCC972 controller.
Utilization of the GE 90-20 controller
caused us to remove the 230VAC 10A transmitters, equipped with a 24V solenoid, from
the final hardware configuration because the standard inputs of the
controllers allow them to work as transmitters (up to a current value equal to
2A). Upgrading the system consisted of incorporating additional binary (bi-state)
outputs, which was performed via adequate binary coding of the states on
outputs of the main controller.
An exemplary control program, which
controls the binary (bi-state) output %Q0005 in the GE 90-20 controller, is
presented in Fig. 4. It was prepared by means of Logicmaster 90.
In Fig. 5, the main screen for the
visualization of the working state and layout of the system is presented,
whereas the panel of time histories and current values of chosen parameters is
shown in Fig. 6. The software was prepared by means of Wonderware InTouch.
In Fig. 7, the view of the mounted
control system is presented.
|
|
|
Fig. 3. Control code fragment in Cscape
Fig. 4. Fragment of the programme controlling
the binary output
Fig. 5. The main screen of the
application
Fig. 6. View of the charts on screen
Fig. 7. View of the control system
5. test INVESTIGATIONS OF THE CONTROL SYSTEM
The prepared controlling system was
subjected to test investigations in order to check the correctness in the performance
of the application that allows for controlling as well as visualizing the work
of the system. In Figs. 8 and 9, the chosen time histories of pressure in the first
compressor, as registered during the test investigations, are presented.
Fig. 8. Process pressure changes of compressor no.
1 during the first test run
Fig. 9. Process pressure changes of compressor no.
2 during the second test run
Regarding the service working mode, in
cases where the motor of the compressor is switched off, the breaking valve (which
cuts the compressor vessel from the pneumatic installation) remains open. It
allows for the release of the pneumatic installation of pressured air.
6. FINAL REMARKS AND COnCLUSIoN
The system of control in air
compressors, as described in the present paper, is installed in the didactic
laboratory of the university. It has been built utilizing the Astraada RCC972
controller. The introductory tests and practical experiments confirmed that it
works properly and reliably, as well as allows for remote controlling and
monitoring of the work of the group of compressors delivering compressed air to
the installation mounted in the didactic laboratory. The performed test
investigations allowed for the formulation of additional conclusions appropriate
to the possible development of the system. Based on our detailed observations,
we can conclude that the system ought to be equipped with an additional
pressure sensor in the main container of the compression workshop. Besides, with
regard to the temperature sensors, which provide information about the
temperatures of particular blocks in the compression system, it is necessary to
mount additional air temperature gauges in the compression workshop. In order
to perform an analysis of power consumption in relation to the supply of the compressor
system, a measurement device should be incorporated into the system when performing
reports on consumed energy, e.g., by using the current instrument transformers.
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Scientific Journal of Silesian University of Technology. Series Transport
76: 19-24. ISSN: 0209-3324.
Received 25.11.2015;
accepted in revised form 04.04.2016
Scientific Journal of Silesian University of
Technology. Series Transport is licensed under a Creative Commons Attribution
4.0 International License
[1] Faculty of Mechanical Engineering and Computer
Science, University of Bielsko-Biała, 2 Willowa Street,
43-309 Bielsko-Biała, Poland. E-mail: wojciechgoora@gmail.com.
[2] Faculty of Mechanical Engineering and Computer
Science, University of Bielsko-Biała, 2 Willowa Street,
43-309 Bielsko-Biała, Poland. E-mail: jjanusz@ath.bielsko.pl.
[3] Faculty of Mechanical Engineering and Computer
Science, University of Bielsko-Biała, Willowa 2 Street,
43-309 Bielsko-Biała, Poland. E-mail: jklosinski@ath.bielsko.pl.