individual parts of the system can be
allocated clearly.
An ANTM03/3 antenna,
developed by Funke & Huster
Bergbautechnik, is used as shortened
λ/4 antenna. The outstanding feature
of this is its antenna gain optimised
for both transmission bands
(27/35 MHz). A perfect level is
thereby ensured for transmitting and
receiving direction.
Depending on the local conditions
and the received signal level values
established in several test runs, the
antennae are mounted on suitable
supports on the conveyor (cage
antenna: Figure 3) and in the shaft
(shaft antenna: Figure 4).
The corresponding mounting
devices are designed in a way to
ensure quick and easy replacement of
the antennae.
Basic operating
mode and monitoring
mechanisms
Electromagnetic waves in the shaft are
transmitted by antennae: one antenna
is connected to the fixed station and
installed below the pithead and the
second is connected to the conveyor
station (mobile station/cage station) in
a place that enables perfect and
uniform transmission quality.
The MR90 mine radio system is a
duplex system, which uses the 27 MHz
band for transmission from conveyor to
fixed station (up-link) and the 35 MHz
band for down-link transmission. These
frequency ranges were selected and
defined for the transmission bands to
improve interference immunity, for
example, regarding electromagnetic
interferences generated by the
frequency converters of the hoisting
drives.
One high-frequency carrier is used
for transmission of voice from the
conveyor to the fixed station and back.
The other high-frequency carrier is
used for bi-directional (duplex)
transmission of data between the
conveyor station and the fixed station.
In order to avoid ambiguity of
bi-directional data transmission
between the fixed station and the
conveyor station, achieve a fixed
coupling between the partner stations
within a conveyor system and ensure
separation from other radio systems
operated in the same shaft or adjacent
shafts; the main transmission
parameters (station address, telegram
length, addressing and arrangement of
I/O modules) are adjusted to have only
one defined point-to-point coupling
during operation, i.e. one master station
is allocated to one secondary station.
Conditioning (serial-parallel
conversion) of binary and analogue
signals is effected by the MOD02 data
radio modem. The binary data stream is
frequency-modulated and/or
-demodulated according to the FFSK
procedure, as well as transmitted and
received via the 27 and 35 MHz band.
The corresponding transmitters and
receivers operate in a frequency range of
26.5 – 27.5 MHz and/or 34.5 – 35.5 MHz.
The input circuits of the input
modules used are monitored for short
circuit or break of conductor to prevent
errors in feed lines from causing
incorrect information. Errors are
visualised using a diagnostic unit and
transmitted to the respective remote
station as well.
The MOD02 data radio modem,
featuring parameter setting (firmware),
is designed for multi-task operation
with up to five tasks. If monitoring
functions respond and/or alarm
messages occur, rapidly responding
change of task levels with short cycle
times is effected to avoid accumulation
of errors and to give diagnostic
messages. Data transmission from the
fixed station to a master computer or
PLC system is effected by serial data
transmission according to Specification
Mining Sheet BB22444 or Coupling
Procedure RK512.
Transmission of data using digital
or analogue input and output
modules, operating in parallel, can be
effected alternatively or additionally.
Monitoring of radio data
transmission
The MOD02 data radio modem used
as the master (conveyor station)
transmits data telegrams periodically.
Depending on the number of user data
bytes to be transferred, the cycle time
is about 100 – 200 msec. If the
secondary station receives a valid
telegram from the master allocated to
it, the secondary station itself starts
Figure 1. Cubicle MR90 system (fixed
station).
Figure 2. Cubicle MR90 system (cage station).
46
|
World Coal
|
March 2016
