21-08-2014, 03:16 PM
DevelRSment of a Web Based Fault Diagnosis Instrument System Seminar Report
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Abstract—All running machines may deteriorate because of
abnormal mechanical wear, fatigue crack, poor lubrication
and so on. Physical parameters such as vibration, sound,
temperature, etc. may vary with its deterioration. In this paper
a web based instrument system which can collect data of
vibration, temperature, image, radio frequency identification,
meter indicator and observed variables was developed for
condition monitoring and fault diagnosis. Firstly, the structure
and principle of the instrument system was introduced; then
the portable instrument based on arm microprocessor and
embedded Linux operating system was designed; after that the
acquisition of vibration signal and the analysis of the vibration
data was discussed; finally the function of application was
presented. The developed instrument system provided an
effective method for device management, condition monitoring
and fault diagnosis. It has good practicability and can be easily
incorporated with the enterprise asset management system.
INTRODUCTION
Abnormity or fault may occur on running machines
because of mechanical wear, fatigue crack, poor lubrication
and so on. Fault symptom can be observed by such physical
parameters as vibration, temperature, sound and so on[1-4].
There exist some kinds of conventional instruments with the
aid of which these parameters can be collected. But these
traditional instruments can merely acquire signals in one
physical domain and lack functions of management on data
and devices. So in this paper, a web based instrument system
was developed to overcome these disadvantages. The
instrument system not only includes intelligent portable
instruments, but also contains a web based management
system. It has the following features: 1)The terminal is
highly integrated and can be used as an all-in-one
instrument[5]. It can collect data of vibration, temperature,
image, radio frequency identification, meter indicator and
observed variables. It can also be operated as an electric
torch; 2)The developed system overcomes the defects in
lacking of connection between the measurement instrument
and the management platform. The collected data can be
easily uploaded to the database server to construct the
equipment records by using of the network structure. 3)The
design of the instrument is human oriented and can be easily
operated; 4)The development of the instrument provide an
effective method for equipment measurement and fault
diagnosis. By using the instrument the automation level of
the device management can be improved to some extent.
SYSTEM STRUCTURE
As illustrated in Fig.1, the instrument system structure is
mainly composed of servers, measurement stations, browsers
and portable terminal instruments. Basic information about
the equipment, measurement plan and task, rules of work
shifts and collected data by terminal instruments are all
stored in the database server. Web server is used to publish
reports on test data, reports on machine fault diagnosis and
evaluation, analyzed charts and so on through internet or
intranet. The authorized users in the intranet/internet can
easily browse the check data so as to aware of the equipment
running conditions. And the repair schedules can be
scientifically arranged depending on the situation. The
servers including database server and web server are act as
central computer arranged in the information center of the
enterprise.
The application running on the client computer on one
hand is used to search measurement task from the database
server and download it to the terminal instrument. On the
other hand when a human operator finished the check in the
industry field, he can upload the data to the database by
using the application.
VIBRATION SIGNAL ACQUISITION
A. Structure of Vibration Channel
The integrated circuits piezoelectric acceleration
transducer was adopted in the instrument development. The
acceleration acquisition circuit diagram is shown in Fig.3.
The whole data acquisition process is under the control of
microprocessor. The circuit is composed of transducer
interface, amplifier, filter, analog to digital conversion and
other circuits. The gain factor can be adjusted under the
control of CPU automatically according to the amplitude of
the input acceleration. The filter is an eighth-order lowpass
Butterworth anti-aliasing filter. Its cutoff frequency
Performance Test of Vibration Measurement
Here a signal generator was used to generate the standard
sinusoidal signal for the performance test of vibration
acquisition channel. The noise level of the generator output
is 2mV. We assume the sensitivity of acceleration
transducer equals to 100g/mV. Some test data are shown in
table 2 and table 3.
In table 2, sinusoidal signals with 100mV and different
frequencies were transmitted to the instrument. In table 3,
signals with same frequency 80Hz but different amplitudes
were tested. The peak value of acceleration, root mean
square of velocity and peak to peak value of displacement
are indicated in the table. The calculation of theoretical
value of each dimension is as follows:
The peak value of acceleration is calculated by (1)
Example of the Instrument Applicationt
An example of application of the instrument as a
vibration collector is shown in Fig.4. The route mode is a
specialized user interface designed to be used in spot
inspection and machine vibration fault diagnosis. It includes
route setup, standard vibration data collection measurements
such as Ap, Vrms, Dpp and also waveform, spectrum
measurements.
The instrument receives one or multiple routes from the
server, which is an index file pointing to multiple pre-defined
machine points and measurement parameters
FUNCTIONS OF THE SOFTWARE
Application in the Iinstrument
The application running in the instrument are
programmed with C language, which is the most prevailing
language used in the design of embedded system. The source
code is compiled with arm-linux-gcc. The functions achieved
by the application are illustrated in Fig.5. Spot inspection
allows the operator to use the instrument as a route collector.
The instrument receives one or multiple routes from the
server, which is an index file pointing to multiple pre-defined
machine points and measurement parameters. The human
operator then carried the instrument and followed the
direction displayed in the screen to complete the field check.
The collected data type includes vibration, temperature,
image, RFID, meters indicators and observed variables. The
collected data are uploaded to the database server.
The functions of vibration test and temperature
measurement allow the
human operator to acquire
and analyze data on
undefined machine point in
the route. By using the shift
working arrangement
module, the human operator
can retrieve the shift and
spell information about the
routes stored in the
instrument.
Functions of the Software
The collected data are uploaded to the database server to
make further analysis, generate report and educe the
diagnosis conclusion. The database was designed using
database management oracle 10g. The software was
programmed with java language. As shown in Fig.6, the
software mainly composed of modules of device
management, spot inspection, fundamental information,
communication, reports, user management, signal analysis
and others. With the device management module, the device
and critical components are coded and stored in the database.
Thus the archives files of the devices were established. The
module of spot inspection can be divided into three major
management submodules: the management of criterion, the
management of duty period and the management of route.
The designed fundamental information included
management of department, management of position,
management of unit and management of position. With the
communication module, the checked data can be uploaded to
the server, and the route task can be downloaded to the
terminal instruments
CONCLUSIONS
In allusion to machine condition monitoring and fault
diagnosis, a network instrument system was developed. The
designed instrument system mainly composed of servers,
clients, browsers and terminal instruments. It provides a kind
of tools to assure the safe operation of the mechanical
equipment. The raw data for on-condition maintenance can
also be obtained by using of the system. The automation level of the device management was enhanced to some
extent. The highly integrated terminal instrument can gather
almost all physical parameters needed. Not only does the
instrument has features of high precision, high reliability;
portability, but it has functions of route inspection and can
easily be incorporated with the management system as well.
Besides, the modular structure of the instrument system
makes it can be easily transplanted to other relative fields.