FIELD OF THE INVENTION
The present invention relates to a power and process plant using gravimetric belt
based solid flow system controllable based on plant demand rate including field
limit switches provided to determine the amount of material on belt, and to
monitor the bunker flow as well as the switches being discharge operable under
different modes of operation as remote, calibration and local control. More
particularly, the invention relates to a system to control the amount of solid flow
in to the control system of a process plant based on multiple operating
conditions for trip, alarm and annunciations.
BACKGROUND OF THE INVENTION
It is known that the process plants need a control system to control the amount
of the consumables in the plant. The consumable may be solid, liquid or gas
substance.
The control system for existing process plants are operated with a plurality of
cables each assigned for every field input signal which are terminated at the
remote controller cabinet. The plurality of cables includes a cable for load cell
sensor for computing the weight of the medium; a cable for tacho generator; a
cable for calibration pulse signal; a cable for belt motion sensor and multiple
cables for limit switches. According to cost and complexity of running multiple
cables from the field to the remote cabinets according to the prior art needs to
be reduced and/or eliminated.

In the prior art feeding devices, it is necessary that the weighing means be out
of balance in order that the feed can be maintained at either an increased or a
decreased amount from that which would exist when the weighing means is in a
balanced condition.
US Patent No.2,637,434 describes belt type gravimetric feeders, and more
particularly to means for controlling the operations of gravimetric feeding
devices.
US Patent No. 3,528,586 describes a gravimetric constant feed belt feeder for
continuously feeding and weighing dry granular material. A belt is supported by a
weighing table in the form of a plate which is pivoted at one end and supported
at its other end by a pneumatic weight transmitter. The transmitter generates a
signal indicative of load changes. The signal is used to control a gate valve which
controls discharge from an inlet hopper to the belt. The weight transmitter
senses load changes and provides a proportional pneumatic signal to a
controller. The output of the controller operates a cylinder for positioning the
valve member. The exact position of the valve member is constantly detected.
The feed rate is easily changed by adjusting a set point regulator. The belt
tension and the belt tracking are easily adjusted by means of pneumatic
cylinders. The pneumatic cylinders, set point regulator, and tare weight are
conveniently adjusted at a control panel.

US Patent No. 7055559 B2 describes a system comprising : a first dispensing
device; a second dispensing device for dispensing particulate matter, the second
dispensing device comprising: a container for holding particulate matter; a
conduit to transport a stream of liquid carrier and to receive particulate matter
from the container; a sensor to.monitor the amount of dry particulate matter
dispensed; and a local controller coupled to the sensor to generate a signal when
a predetermined quantity of particulate matter is dispensed and to modify the
flow of particulate matter into the conduit in response to said signal; and a
parent controller coupled to the first and second dispensing devices, wherein the
parent controller transmits to the second dispensing device remote signals
associated with a first set of dispensing device operations and the local controller
generates local signals associated with a second set of dispensing device
operations.
Thus, the prior art disclose multiple methods and systems for coal feeder control
but they still use the field inputs via individual wiring of signals up to the main
station.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a system to control the
amount of solid flow into the control system of a process plant based on multiple
operating conditions for trip, alarm and annunciations in which the rate of feed
can be closely and accurately controlled.

Another object of the invention is to propose a system to control the amount of
solid flow into the control system of a process plant based on multiple operating
conditions for trip, alarm and annunciations in which all the field input sensors
data are clubbed together as a single signal packet and transmitted to the
remote control station instantaneously.
SUMMARY OF THE INVENTION
Accordingly, there is provided a system to control the amount of solid flow into
the control system of a process plant based on multiple operating conditions for
trip, alarm and annunciations. The system inter alia includes an SIL-3
microcontroller. The microcontroller is the heart of the system which
communicates with the field inputs inclusive of all the digital, analog inputs.
Digital inputs are potential free contacts such as limit switches, analog inputs
vary from millivolt sensor inputs, current pulse inputs, proxy sensors, voltage
pulse inputs and tacho generator inputs. All these inputs are collated in the field
module and transmitted to the master controller using MODBUS over RS485 on
redundant communication lines.
By implementation of this invention, the number of cables laid from the field
module to the remote modules is reduced. The communication protocol simplifies
the data logging and usage purposes. The field data are interpreted with ease
and the trend and grouping of data can be visualized in single screen. The
signals thus acquired are processed by the master controller where the logical
checking an loop feedbacks are processed to match the demand and actual feed
rate.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 - shows a functional block diagram of the system of the invention.
Figure 2 - shows the sub modules of the field module of the system of Figure 1.
Figure 3 - shows the sub modules of the remote modules of the system of
Figure 1.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
As shown in Figure 1, the system consists of two major modules such as a field
module and a remote module. The field module is placed in the actual field near
the sensor inputs. The field modules collate the sensor inputs namely the load
cell weight signal, tacho generator RPM signal, belt monitor signal, calibration
pulse signal, digital input signals and process them into data packet and
transmits it to the remote module via RS485 cable.
The field module is placed close the field input sensors. The field module is
powered by a 24V DC supply, which is the only source of energy for the module
ICs in the PCB and the LCD, keyboard set mounted.

The firmware logic and the flow of the program for the Field Module of the
Electronic Field Control System are executed in TMS320F28069 processor. The
inputs to the system are 8 digital inputs, 2 tacho signals, 2 calibration probe
pulses and 1 BM pulse, FM is also communicating to the RM via RS485 through
Modbus protocol. The system is built with diagnostic module of operation to
ensure the system inputs are read correctly.
If the correct combination of the keys (LEFT + ENTER + RIGHT) are pressed the
Field module (FM) will act as a diagnostic mode. The main menu for the
diagnostics will be displayed to choose the diagnostic. To return from the
diagnostic mode ESC key is pressed.
Timing Diagnostics:
If the UP key is pressed, the timing diagnostics are shown, which consists of
Tacho diagnostics, Cal probe diagnostics and BM diagnostics. The calculated
timing for the Tacho, BM and Cal probe signals are shown on the display. If the
signals are not present the timings will be shown as 0.
ADC Diagnostics:
If the LEFT key is pressed, the ADC diagnostics starts and the ADC values are
read from both the channels and are displayed. If the ADC values are displayed
only after the last 10 ADC values are stored, the values are averaged and
filtered. The values shown on the left are the decimal ADC readings for both the
channels and the values shown on the right are the hexadecimal values. To go
back to the main menu, the ESC is pressed.

Keypad Diagnostics:
If the DOWN key is pressed, the keypad diagnostics commences and the keys
when pressed and released, the status is shown on the display screen.
Input Diagnostics:
If the RIGHT key is pressed the diagnostics for the digital inputs commences and
the status of the digital inputs is shown wherein the digital inputs of the
corresponding LEDs are glowing.
Application
If the diagnostics is not selected the FM operates in the application mode. The
feeder operates in four modes for example, Local, Remote, Calibration and Off.
The current mode of the FM is known from the RM control bits. The name of the
mode will be displayed on the LCD. The Check Model Input() returns the mode
of the feeder. The Feeder also have .four state of operation such as IDLE,
RUNNING, ON, OFF.
A) Local Mode:
If the feeder is operating in the Local mode, the menu for the Local mode is
displayed on the LCD.

Functions in the local mode are:
a) Manual mode:
In the local mode if the ENTER key is pressed the Feeder switches to the manual
mode in local. In the manual mode the motor can be turned on manually from
the keys on the keypad, the ENTER key is pressed to go back to the normal
mode again. Further, the Manual mode can be split into two modes.
At entry point, all the trip flag are cleared and PID loop is disabled LOCAL
MODE is set in FM control register, and all delay timers are disabled.
Depending on the current status of the feeder and the PID enable bit, all
the timer actions are initiated as under-
Check all the trips and alarm
In local Mode timer action checks.for RPM error.
If error occurred, then set BIT_RPM_DEVIATION. If error is within limit,
then clear BIT_RPM_DEVIATION bit
Inching mode

If the UP key is pressed the feeder switches to the inching manual mode. The
RIGHT and LEFT keys are used to determine the direction in which the motor
will run. The inching mode will run only if the RIGHT or LEFT key is pressed.
The motor stops if the key is released.
b) Continuous mode:
If the down key is pressed the feeder switches to a continuous manual mode.
The RIGHT and LEFT keys are used to determine the direction in which the
motor is running. In the continuous mode, when either of the RIGHT and
LEFT is pressed, the motor starts and continues to run even if the key is
released. The motor stops only when the ESC/ENT key if pressed/ OFF Key
pressed in Remote Module/Mode Change done from Remote module.
The other activities include:
i) ADC Reading:
The load cell signal is a strain gauge sensor providing 3mV per voltage of
excitation. The sensor signal is interfaced using a single chip IC namely,
ADS1232 which has 2 channels of input signal processing capacity. The
ADS1232 has an internal programmable gain amplifier, 24 bit ADC,
programmable sampling rate of 10 SPS or 80 SPS and the chip comprises of
3rd-order modulator and 4th-order digital filter data is provided as a serial data
out which is interfaced with the controller. The raw load call data thus
obtained is smoothened by moving average filter in the controller. The raw

data as well as the filtered data, both are provided to the remote module in the
RS485 link. The ADC provide the converted Load Cell weights. The ADCTick()
function will read, store, average and filter the latest 10 ADC samples and
communicate it to the RM through Modbus. The ADC filtered values will also be
displayed on the LCD.
ii) Tacho timing:
The timing of the two tacho signals are calculated. The tacho 1 signal timing is
calculated by HRCAP. The HRCAP interrupt occur when the tacho 1 signal is
detected and a long timer values are calculated between two high going pulses.
The timing of tach 2 signal is calculated by ECAP. The ECAP capture registers
capture the time difference between two high going pulses of tacho 1. The tacho
timing values are also displayed on the screen. If the tacho signals are not
detected for some period the values will be 0. The ratio generator signal
processing module takes in the raw sine wave signal from the tacho, converts
the sine to square wave by detecting the zero crossing and computes the
frequency of the input wave and directly the RPM of the motor since the motor
RPM and the sine wave frequency are proportional. The frequency thus
computed is sent to the remote module via the RS485 link as the tacho
feedback.
BM signal timing:
The belt motion monitoring module takes in either proxy sensor input or namur
sensor input which is based on the jumper settings on the PCB . The processing
of belt motion signal is done in the field module controller which computes the

frequency of the belt motion sensor and transmits the same to the remote
module for further processing.
The BM is detected using ECAP module and the timing between two high going
pulses is calculated and passed on to the RM.
Keypad and Digital input diagnostic:
The status of the keypad if any key is read, updated and passed on to the RM.
The status of the keypad inputs is also read continuously and updated to the RM.
The digital inputs to the field modules are potential free contacts which are
detected using the 24V return line of the limit switches. The field inputs are also
transmitted to the remote module in separate register along with the keyboard
input status bits. The LCD display is driven by the local controller at the field and
the keyboard input status is sent to the remote module to detect the key and do
the necessary action for the corresponding key.
B) Remote mode:
If the feeder is operating in the Remote mode the menu for the Remote mode is
displayed on the LCD. Functions in the remote mode are the housekeeping
activities. The housekeeping activities are the same as in the Local mode. There
is no provision for the manual operation in Remote mode. The housekeeping
results are communicated to the RM continuously. The feed rate feedback is
provided to the customer as 4-20mA current output.

At entry point, clear all the trip flag. Disable PID loop. Set REMOTE MODE
in FM control register. Disable all delay timers.
Depending on the current status of the feeder and the PID enable bit, do
all the timer actions.
Check all the trips and alarm
In remote mode timer action, depending on LC tracking error system
enters into two modes.
i) FEED_VOLUMETRIC mode
• If there is LC tracking error/ LC out of range/ LC out of range/ LC '
failure/Diconnected, system enters into FEED_VOLUMETRIC_ MODE
• Compute actual feed rate.
• Compute RPM. Compute actual feed rate knowing actual RPM.
• Do feed rate deviation check. If there is error, set error bit
BIT_FR_DEVIATION.
Otherwise clear error bit
• Does RPM deviation check. If there is error, set error bit
BIT_RPM_DEVIATION.
Otherwise clear error bit.

ii) FEED_QUASI_GRAVIMETRIC mode
• Compute the bulk density with each load cell when the LC tracking fails,
consider the load cell value which ever gives the closer value to the actual
calculated density and perform the weight computation using the
aforesaid Load cell.
• Compute actual feed rate.
• Compute RPM. Compute actual feed rate knowing actual RPM.
• Does RPM deviation check. If there is error, set error bit
BIT RPM DEVIATION.
Otherwise clear error bit.
• Do feed rate deviation check. If there is error, set error bit
BIT_FR_DEVIATION.
Otherwise clear error bit.
iii) FEED_GRAVIMETRIC mode
• If not Volumetric and Quasi_gravimetric and during initial loop, system
enters into FEED_GRAVIMETRIC_MODE
• Compute actual feed rate.
• Compute RRM, Computer actual feed rate knowing actual RPM
• Do feed rate deviation check. If there is error, set error bit
BIT_FR_DEVIATION.
Otherwise clear error bit.
• Does RPM deviation check. If there is error, set error bit
BIT_RPM_DEVIATION.
Otherwise clear error bit.

C) Calibration mode:
There are two modes in the calibration mode. The calibration process will be
completely controlled by the RM through the control bits. FM will give the
inputs to RM through Modbus and will display status of the calibration
process.
Tare Cal:
During tare cal there will be no coaj on the belt. The ADC will measure the
belt weight or the dead weight. Two cal probes will be placed on every four
tapes present on the belt. The tacho signals will give the timing to calculate
the RPM of the belt. When the UP key is pressed for tare cal the RM will send
the tare cal start bit and the Tare cal screen will be displayed. When the
motor stabilized bit is set by the RM the counting of the cal probe signals will
start. The counting will continue till 8 Cal-A and Cal-B will be detected.
During tare cal the FM will also do the housekeeping activity. But the tacho
timing values will not be communicated to the RM always but will be passed
after taking the average of all tacho timings calculated between Cal-A detect
and Cal-B detect. And the Load Cell values will be read and averaged
between the first Cal-A pass and the 8th Cal-B pass and then passed on the
RM. After the inputs are given to the RM the RM will pass on the calculated
results of the Tare Cal which will be displayed.
After receiving UP key from FM, system will enter into CALIB_TARE mode.
At entry point set RPM and enable PID loop. Start delay timer for RPM
stabilization.
Once motor is stabilized,

o Set motor stabilized bit in RM holding register, which will set FM motor
stabilized bit in PLC.
o Set TARE_BUSY bit in RM holding register, which will set FM TARE_BUSY
bit in PLC.
o Disable motor stabilized timer,
o Once TARE_BUSY is set, start polling data from FM for 8 cal pass
(TACHO values, LC values and Calib time)
After all 8 cal passes, analyse calibration result. If results are OK
o Set RM_TARE_RESULTS_DONE bit in RM holding register, which will set
FM_TARE_RESULTS_DON bit in PLC.
o Send calibration results to FM.
After sending results to FM
o Set RM_TARE_OVER bit
o Clear RM_TARE_BUSY bit, which will clear FM_TARE_BUSY bit in PLC.
o Set RM_ABORT_CALIB bit, which will switch off feeder and clear
FM_TARE_START and FM_DO_SPAN bit in PLC
If moor is not st6abilized or ESC key is received from FM or ABORT is
received from HMI,
o Switch OFF feeder,
o Clear FM_TARE_START and FM_DO_SPAN bit in PLC.
In analyse calibration results, check TACHO and LC values received from
FM
If results are NOT OK,
o Set RM_TARE_ERROR_STATUS bit, which will set
FM_TARE_ERROR_STATUS bit in PLC
o FM waits for ABORT.

Span Cal
Span cal operation is same as Tare Cal only difference is the text weight is
added. The display fro span cal will also differ from Tare Cal. When the motor
stabilized bit is set by the RM the counting of the cal probe signals will start. The
counting will continue till 8 Cal-A and Cal-B will be detected.
After receiving DOWN key from FM, system will enter into CALIB_SPAN
mode. At entry point set RPM and enable PID loop.
Wait for the SPAN weight,
o If weight is OK, clear RM_SPAN-ERROR_STATUS.
o Start delay timer for RPM stabilization
Once motor is stabilized
o Set motor stabilized bit in RM holding register, which will set FM motor
stabilized bit in PLC.
o Set SPAN_BUSY bit in RM holding register, which will set FM SPAN_BUSY
bit in PLC,
o Once SPAN_BUSY bit is set, start polling data from FM for 8 cal pass
(TACHO values, LC values and Calib time).
After all 8 cal passe3s, analyse calibration result. If results are OK.
o Set RM_SPAN_RESULTS_DONE bit in RM holding register, which will set
FM_SPAN_RESULTS_DON bit in PLC.
o Send calibration results to FM. After sending results to FM,
o Set RM_SPAM_OVER bit.
o Clear RM_SPAN_BUSY bit, which will clear FM_SPAM_BUSY bit in PLC.
o Set RM_ABORT_CALIB bit, which will switch off feeder and clear
FM_SPAN_START and FM_DO_SPAN bit in PLC.

If motor is not stabilized or ESC key is received from FM or ABORT is
received from HMI.
o Switch OFF feeder
o Clear FM_TARE_START and FM_DO_SPAN bit in PLC.
In analyse calibration results, check TACHO and LC values received from
FM. IF results are NOT OK.
o Set RM_SPAN_ERROR_STATUS bit, which will set
FM_SPAN_ERROR_STATUS bit in PLC.
o FM waits for ABORT. If weight is not available,
o Set RM_SPAN_ERROR_STATUS bit in PLC
During SPAN cal the FM will also do the housekeeping activity. But the tacho
pulse timing values will not be communicated to the RM always and will be
passed after taking the average of all tacho generator timings calculated
between Cal-A and Cal-B detect. And the load Cell values will be read and
averaged between the first Cal-A pass and the 8th Cal-B pass and then passed on
to the RM. After the inputs are given to the RM, the RM will pass on the
calculated results of the Span Cal which will be displayed.
The single board remote is the master controller which reads the data from the
field, demand from the DCS [Distributed Control System] and drives the
complete system. The remote module just in similar fashion as that of the field
module has analog input channels, digital input channels along with analog
outputs and digital outputs. The analog input channels are all isolated channels
to read the 4-20mA current inputs from the DCS corresponding to the demand
feedrate, the super-heater temperature, pressure, input feedwater temperature,
pressure. The potential free digital inputs for the remote module includes, the
mode selection rotary switch, emergency OFF, Phase failures contact, motor

overload contact, VFD fault contact, feeder start, feeder stop contacts from the
DCS, feeder running feedback toward and feeder running reverse feedback
contacts. The potential free digital output is provided to the relay board for
driving contacts and providing necessary feedback for the customers and DCS for
status indications. The analog outputs are for providing the current signal for the
set speed for Variable Frequency Drive and for providing the feedback for the
current feed rate to the Secondary Air Damper Control, Mill Air Control and other
related systems.
The difference between the remote and local modes is such that the demand for
the system in the former mode is from DCS and the latter is the speed set point
in the program parameter. During the remote mode operation the feeder needs
to cater material according to the demand feed rate, where as in local mode
operation is used for running or jog the feeder at set speed in either forward or
reverse direction. Along with the above, the controller also interfaces the F-RAM
for saving and reading back the data, drives RS485 Modbus link to the HMI for
configuring the system and to read the live data/status and DCS communication
via RS485 link for status indication of the system. All the above functionalities
are driven by the SIL-3 controller which controls the Modbus traffic, reads the
analog and digital inputs, process the data and controls the feed rate according
to the demand rate.

WE CLAIM :
1. A system to control the amount of solid flow into the control system of a
process plant based on multiple operating conditions for trip, alarm and
annunciations, comprising a single board, a master controller remote
module having a plurality of inbuilt isolated channels to read the input '
analog and digital signals, process and control the feed rate according to a
demand derived by driving the RS485 communication link between the
field module; a human machine interface (HMI); and a master control
system providing necessary digital and analog feedback to the users on
process parameters, wherein the system includes a field module which •
collates all the field input analog current, and voltage signals to process
the signals for digitizing according to time information, pulse information
and digital data information and transferring the processed signals to a
remote module controller via a redundant Modbus over RS485 link.
2. The system as claimed in claim 1, wherein the field module and the
remote module are tandemely operable to control the start, stop, inching,
throttling of the system according to the input data and wherein a
software logic loaded and run on the system monitors the alarm and trip
conditions based on the corresponding outputs.

3. The system as claimed in claim 1 or 2, wherein the field module
contains the terminations for the field sensors and a local display unit
with keys to control, monitor and diagnose the inputs and wherein the
local control keys are also used for operating the system on specific
mode of operation.
4. The system as claimed in claim 1 or 2, wherein the remote module and
the field module each contains Hot Swap controllers that all the
modules to be safely inserted and removed from powered terminal,
wherein the board supply voltage can be ramped up at programmable
rate and wherein the chips include a programmable analog fold back
current limit circuit which enable the modules to be hot pluggable.
5. The system as claimed in claim 1 wherein the remote module
comprises an external memory to log the events, changes made to the
live parameters and store the default parameters of the system.
6. The system as claimed in claim 1, wherein the system is operable
under three modes in remote operation namely, gravimetric, volume-
tric and quasi-gravimetric, the gravimetric mode being the mode of

operation where the load cells are functioning within acceptable deviation
and the weight of the medium is computed using both the load cells,
wherein the volumetric mode being the mode where the system operates
on the computed bulk density or set density operation upon the failure of
both the load cells, and wherein the quasi-gravimetric mode being the
mode where the system operates by computing the weight of the medium
using a single healthy load cell in the event of failure of single load cell
out of two.

ABSTRACT

The invention relates to a system to control the amount of solid flow into the
control system of a process plant based on multiple operating conditions for trip,
alarm and annunciations, comprising a single board, a master controller remote
module having a plurality of inbuilt isolated channels to read the input analog
and digital signals, process and control the feed rate according to a demand
derived by driving the RS485 communication link between the field module; a
human machine interface (HMI); and a master control system providing
necessary digital and analog feedback to the users on process parameters, .
wherein the system includes a field module which collates all the field input
analog current, and voltage signals to process the signals for digitizing according
to time information, pulse information and digital data information and
transferring the processed signals to a remote module controller via a redundant
Modbus over RS485 link.