FIELD OF THE INVENTION
The present invention relates to a real-time virtual sensor system for virtually
measuring online wire size in each pass at wire drawing machines.
BACKGROUND OF THE INVENTION
Wire drawing process deals in production of wire of desired finish size and
properties. To achieve the target finish size and properties, it is necessary to
draw the wire such that in each pass the recommended wire size and draft is
achieved. In wire drawing, it is required to meet the target maintaining
maximum possible die life, so as to reduce the cost of operation and reduce
delays due to wire breakages and delays in changing dies. According to the prior
art, the operator feeds the measured actual size at each pass, once a day, in a
Programmable Logic Controller (PLC) through an operating panel (OP) and
accordingly the power is drawn to draw the wire at desired speed. During
drawing when the wire size changes in any pass, the dancer arm of the machine
corrects the wire speed and block speed accordingly. But after a certain limit, the
dancer fails to make proper corrections till fresh size measurement in each pass
is fed to the PLC by the operator. This calls for online monitoring of wire size in
each pass for a better process control. Also, online monitoring of wire size in

each pass allows monitoring the die wear and other wire drawing conditions in
each pass.
According to prior art, a system exists for online measurement and monitoring of
wire size in each pass. But the online computation of the wire size in each pass,
in the referred existing system depends on the online feedback of the finish size,
as measured by online diameter gage.
The prior art system resorted to only an auto-correction in speed for any change
in wire size in any pass, till a certain limit. When the mentioned limit is reached,
the operator needs to check the size in each pass and feed the same to the PLC.
If the same is not done on time, die wear rate may increase. Hence, online
monitoring of wire size in each pass is critical for an effective monitoring and
control of wire drawing process.
Level 1 automation systems do exist in the area in which the invented system
has been developed, but it works on operator's intermittent entry of size. The
system works on an assumption that the operator entered size in each pass
remains same till the next entry of size in each pass. Further, online computation
of the wire size in each pass depends on the online feedback of the finish size, as
measured by online diameter gage.

Though it is possible to measure the wire size using instruments like online
diameter gages, the price of one wire size measuring unit is as high as ~ 9-10
lakhs INR. So, installation of such expensive instruments for pass-wise
measurement of wire size may not be a feasible option. Moreover, these online
devices need frequent cleaning for measuring accurately. In addition to this , any
sort of repair required by the device is expensive enough (as high as 2-3 lakhs
INR).
OBJECT OF THE INVENTION
It is therefore an object of the invention to propose a real-time virtual sensor
system for virtually measuring online wire size in each pass at wire-drawing
machines.
Another object of the invention is to propose a real-time virtual sensor system
for virtually measuring online wire size in each pass at wire-drawing machines,
which is enabled to ensure that the wire size after each pass is within the
assigned tolerance band.
A still another object of the invention is to propose a real-time virtual sensor
system for virtually measuring online wire size in each pass at wire-drawing
machines, which allows maintenance of consistency in the wire properties across
the entire length of the wire.

Yet another object of the invention is to propose a real-time virtual sensor
system for virtually measuring online wire size in each pass at wire-drawing
machines, which is capable to reduce breakage and delays of the wire during the
drawing process in the machine thereby improve productivity.
A further object of the invention is to propose a real-time virtual sensor system
for virtually measuring online wire size in each pass at wire-drawing machines,
which makes it possible to monitor the wear of the die in each pass and
enhances overall die-life.
Summary of the Invention
According to the invention, the system is enabled to capture online motor speed
and one-time wire size (as measured and fed by operator, once in a shift) in
each pass from the PLC @ 1 minute interval. The captured data are used to
compute online the following:
- the size of the wire after each pass termed as "virtual size" using the
incremental change in motor speed and previous value of wire size in a
pass.

According to the invention, the system deals virtual measurement of the wire
size in each pass, without any dependency on the measurement by online
diameter gage in any pass/finish pass. The advantages of the invented
system are as under:
- The invented system of virtual sensors is maintenance free
- The invention does away with the botheration of high repair charges
- The invention provides a very cost-effective solution, as compared to
using expensive online diameter gages, for pass-wise wire size
measurement
- The invented system computes online wire size in each pass after
eliminating one variable (i.e. measurement by online diameter gage) and
also, one interface with an additional instrument (i.e. online diameter
gage). This ensures better accuracy in calculation.
The online virtual sensor system according to the system is enabled:
1. To ensure that the size of wire after each pass is within desired tolerance
band;
2. To ensure consistency in properties across the length of the wire;
3. To reduce breakages and hence, delays and improve productivity.
4. Monitor the die wear in each pass and take precautions when required, for
better die life.

5. Take precautions before die wear rate increases, for better die life.
The online system calls for at least one online diameter gage at wire drawing
machine e.g. for measuring wire size at finish pass at the drawing machine.
The invented system has an edge over the prior art system because the invented
system constitutes a low cost, maintenance free solution for the prior art
disadvantages. Moreover, the system uptime of the invented system is higher
than that of the prior art system because the possibility of the device (for
measuring wire size) going out of order is ruled out.
As compared to the prior art systems, the following additional feature has been
incorporated into the invented system:
Online computation of the wire size in each pass, depending on real-time motor
speed and one-time pass-wise wire size (dieset), as entered by the operator in
PLC.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURE
Figure 1- shows a flow-chart depicting the operation of the invented system in a
measuring mode of wire size in a wire-drawing machine according to the
invention.

DETAILED DESCRIPTION OF THE INVENTION
The online virtual sensor system for measuring the wire size in each pass at wire
drawing machine comprises virtual sensors integrated with online model.
The flow chart in Figure 1 clearly shows the operation of the online virtual sensor
system, in which the measurement is done @ lminute interval. Description of
the variables used in the flowchart are as follows:
finish_spdprev = previously captured value of finish speed (i.e. the value 1 minute
before)
finish_spd = real-time finish speed
Virtual_size i = virtually computed wire size in the ith pass
dieschedule i = last value of wire size in the ith pass, as measured and fed by an
operator in PLC
Virtual_size I,prev = previously computed virtual wire size in the ith pass, i.e the
last to last value existing in the system
dieschedule i ,prev = last to last value of wire size in the ith pass, as measured and
fed by operator in PLC
spd_diff i = motor_spd i - motor_spd i,prev
motor_sped i = Block motor speed in the ith pass
motor_spd i, prev = last to last value of block motor speed in the ith pass
coeff i = multiplicative model coefficient for ith pass

To arrive at the model coefficients for the virtual sensors, @ 1 minute interval,
change in wire size (as back calculated using the measured finish size and wire
speed in each pass) with corresponding change in motor speed in each pass was
captured online and multiplicative coefficient (coeff i ) was calculated for
computing the online change in wire size using the change in real-time motor
speed.
The wire size in each pass, as measured by the virtual sensors of the invented
system, are being validated against the wire size in that particular pass, as back
calculated using the measured finish size by diameter gage and wire speed in
each pass. The validation results with one week data shows that the
measurement accuracy of the invented virtual sensors is within ± 0.005mm. The
validation results against pass-wise operator's measurement alsoshow that the
measurement accuracy of the invented virtual sensors is within ± 0.005mm.

We Claim:
1. A real-time virtual sensor system for virtually measuring online wire size in
each pass at wire drawing machines, comprising a plurality of virtual
sensors each assigned to capture several technical parameters of the wire
drawing machine including real-time size and speed of movement of the
wire being drawn and die-wear in each pass; a memory means having
pre-stored data relating to said technical parameters, and a
programmable logic controller (PLC) to manipulate the real-time data
including validating the measured data, the virtual sensors being
integrated with an on line module, the system is configured to:
- determine the motor speed, finish speed, and die-schedule on real time at
an interval of every one minute;
- compare the pre-stored finish speed and the captured finish speed when
both are found to be greater than zero, and equal the motor sped is
determined and when > 1000 rpm, the pre-stored die-schedule and real-
time dieschedule at the ith pass is compared, and when determined to be
equal, the difference in motor speed at ith pass and pre-stored speed
upon comparison when found to be within ± 20 to 30, the virtual size of

the wire at ith pass is determined by adding the pre-stored virtual size at ith
pass and product of motor speed difference at ith pass, and multiplicative
model co-efficient for ith pass.
2. The system as claimed in claim 1, wherein the model co-efficient in each
pass is determined by back calculation using measured finish size and wire
speed.
3. The system as claimed in claim 1, wherein the virtual size of the wire in ith
pass is equal to dieschedule at ith pass when both the pre-stored finish
speed and the captured finish speed is not greater than zero.
4. The system as claimed in claim 1, wherein when the pre-stored finish
speed and the captured finish speed is not equal, the real time virtual size
of the wire at ith pass equals the pre-stored virtual size at ith pass.
5. The system as claimed in claim 1, wherein the difference in real-time
motor speed at ith pass and that pre-stored is not within the range of ±
20 to 30, the virtual size at ith pass captured on real time equals to that
previously stored.

6. The system as claimed in claim 1, wherein when the motor speed
difference at ith pass of the captured and pre-stored values is >20 or
< -20, the captured and pre-stored motor speeds at ith pass is equal.

ABSTRACT

The invention relates to a real-time virtual sensor system for virtually
measuring online wire size in each pass at wire drawing machines, comprising
a plurality of virtual sensors each assigned to capture several technical
parameters of the wire drawing machine including real-time size and speed of
movement of the wire being drawn and die-wear in each pass; a memory
means having pre-stored data relating to said technical parameters, and a
programmable logic controller (PLC) to manipulate the real-time data
including validating the measured data, the virtual sensors being integrated
with an on line module, the system is configured to determine the motor
speed, finish speed, and die-schedule on real time at an interval of every one
minute; compare the pre-stored finish speed and the captured finish speed
when both are found to be greater than zero, and equal the motor sped is
determined and when > 1000 rpm, the pre-stored die-schedule and real-time
dieschedule at the ith pass is compared, and when determined to be equal,
the difference in motor speed at ith pass and pre-stored speed upon
comparison when found to be within ± 20 to 30, the virtual size of the wire at
ith pass is determined by adding the pre-stored virtual size at ith pass and
product of motor speed difference at ith pass, and multiplicative model co-
efficient for ith pass.