|Title of Invention||
AN AUTOMATIC ON-LINE PROFILE MEASUREMENT MACHINE FOR MEASURING THE PROFILES OF HOT ROLLED RINGS
|Abstract||An automatic on-line measurement machine (1) comprising a machine base (2) , a machine table (10) provided with a roller table (3), table cooling air supply (8) and air distributor (12), said machine provided with a bottom laser (4) and a top laser (6) provided at the bottom and top of a C-Arm (5) , a V-block (7) provided at one end of said machine table (10) with a V-block adjusting handle (13) and a bottom laser window (9) provided appropriate to the V-block along the central longitudinal axis of (X-X) of the machine table (10), a linear encloder (11) provided to read the portion of the C-Arm (5) on which laser ( 4,6)) are mounted and provided with two limit switches (not shown) and a servo motor (10) for control of the movement of C-Arm (5) for measurement of a ring.|
|Full Text||The invention relates to an automatic on-line profile measurement machine for measuring the profile of hot rings made In the ring rolling mill of iron and steel Industry.
There are disadvantages associated with the present system of measurement of ring. The main disadvantage is that the rings are usually measured manually using slide caliper which not only makes the procedure ardous but is also prone to inaccuracy because of high temperature of the object
Another disadvantage associated with the present system of measurement of ring is that the line production has to be interrupted during the process of manual measurement of ring resulting in loss of production.
SUMMARY OF THE INVENTION:
Therefore, the main object of the invention is to propose an
automatic on line profile measurement machine for measuring the
profile of hot rolled rings.
Another object of the present invention is to propose a measurement
machine for hot rings which Is very accurate.
Yet another object of the present invention Is to propose a
measurement machine for hot rings which has a very short cycle time
for measurement of rings.
Still another object of the present Invention Is to propose a measurement machine for hot rings which measures the various edges and heights to obtain on-line profile of a hot ring.
According to the present invention there is provided an automatic on line profile measurement machine for measuring the profiles of hot rolled rings, said machine comprising a V-block placed on a machine table or base plate for positioning said hot rolled ring, a C-arm movable between a home position and an end position defining a measurement range, a pair of laser sensors mounted on said C-arm for reading the Y-coordinates of the measurement points with respect to the machine table, a servo motor for actuating a linear movement of the ring in the X-direction and a linear encoder for reading the linear position of the C-arm and providing the X-coordinates of the measurement point with respect to home position of the laser sensors,
The nature of the invention, its objective and further advantages residing in the same will be apparent from the following description made with reference to non-limiting exemplary embodiments of the Invention represented In the accompanying drawings:
Figure 1 top view of a typical ring shown with the V-Block,
Figure 2 sectional view of the ring shown in Figure 1
Figure 3 shows the elevation of the automatic ring measurement
machine Figure 4 plan view of the automatic ring measurement machine of
Figure 5 shows line diagram of ring measurement system DETAILED DESCRIPTION OF THE INVENTION: The automatic ring measurement machine (1) consists of laser sensors (4,6), servo motor (10') and a micro PLC. Figures # 1 & 2 schematically shows the top and side views of a typical ring (14) to be measured by such a system. Here various edges (show as A,B,C,D,E,F,G,H,I,J,K,L in Figure # 2) and heights of the ring (14) are to be located accurately which is achieved by using linear encoder (11) and laser sensors (4,6). The X-coordinates are provided by the linear encoder (11) and the Y-coordinates are provided by the laser sensors (4,6). The arrangement of the system is shown in Figure # 3. -
A pair of laser sensors (4,6) mounted on the C-arm (5) which is moved linearly by the servo motor (10'), scan the top and bottom profile of the ring (14) positioned by the V-block (7) and placed on the base plate (10). The cycle time for measurement of ring (14) is 50 seconds (for a ring (14) of outer diameter 380-mm). To obtain on-line profile of a hot ring using such a system has not been ever done.
The machine comprises of the following important elements (schematically shown in Figure No. 5) and its functions. 1. SENSORS (4,6) are the top and bottom laser (6,4)respecti-vely.
Linear Encoder (11.). This reads the linear position of the C-arm (5) on which the lasers (4,6) are mounted, thus providing the X-Coordinate of the measurement point with respect to home position of the lasers (4,6). It generates a square wave pulse for every 5 microns of linear movement of C-arm (5). The pulses are refined by the Digital Read Out Unit.
Laser Sensors (4,6).These are used to read the Y-Coordinate of the measurement point with respect to the machine table base plate (10). The sensors (4,6) generate millivolt signal, which is proportional to the distance of the opaque reflecting object from the laser source.
Limit Switches (13). There are two limit switches (13), one to sense the Home position, and the other is to sense the End position of the laser's travel, thus confining the movement of C-arm (5) within measurement range.
Control Pendant (14). There are 8 input buttons on the pendant using which 'the operator sends the commands to the program (microPLC(15) which is SMART Input/Output PLC Programmable logic Control which comprises autio/digltal converter (ADC) card, Communication Card, digital/audio converter (DAC) Card, digital input card and digital output Card. The Communication Card is connected to Personal Computer (PC).
It receives inputs from the sensors (4,6) and MM1, and executes the logic to find the dimension of rings from the acquired data. It also controls the movement of the servo motor (10') by sending analog signal to the servo-drive .
It consists of the base unit (2) containing the microprocessor, the battery and a serial port. The serial port is used to communicate with the PC (MMl) through a utility (windows based software) called terminal. It has separate data acquisition cards for digital input (for receiving commands from buttons on pendant), digital output (for glowing the indication lamps on the pendant), analog input (for receiving voltage signals from the lasers) and analog output (for sending voltage signal to control ' the servomotor). It also contains a counter card (to receive signals from encoder and limit switches) and an RS-232 card (to
communicate with the MM!).
3. Actuator (15)
The program running in the microPLC, is responsible for controlling the motor speed. This is done by DAC(Digital to Analog Convertor) card, where the digital signals of the program are converted to analog voltage signal which inturn controls the movement of motor. The speed of the motor is directly proportional to the voltage applied, and the direction depends on the polarity of voltage.
4. The Man Machine Interface (16)
A Personal Computer (PC) is used as a MM1. A VC++ program has been developed as front end for communication between microPLC and the operator. The program is used to provide necessary details to the programs running in microPLC. It is also used for displaying and trending the results. DETAIL DESCRIPTION OF ITS OPERATION
1. Programs residing in microPLC:
The microPLC acts as a real time computer. 0S9 is the real time operating system in place. A set of three programs resides in microPLC
a) Logctrl: This program is responsible for control of servo
motor(10') movement and also for processing the laser read
ings to find the dimensions of ring (14). It is a C program
written using Hawk compiler for OS9. The voltage signals
are read from the sensors (4,6,11) (lasers and encoder).
The voltage signals are converted to distance units. The
distance is again recalculated to fit the frame of
reference. These values are checked for change of height
and change of slope, in the profile, locate the edges. Once the edges are got, they are filtered for true edges.
From these, refined edges, the diameters and heights are
b) PcSioCom: This program is responsible, for communication
between MM1 program running in PC, and logctrl program
running in microPLC, through serial port.
c) Creatlnk: . This program creates the global shared memory
in the microPLC for effective communication between the above mentioned two programs.
2. Programs residing in PC:
1. RARRM: This program is written in VC++(version 6.0), and it acts as an interface between the operator and the microPLC . It communicates with PcSioCom program through serial port (RS232 protocol). It is responsible for sending details of the ring and request, and receiving the results. It also displays the online information and results of the system.
ALGORITHM TO FIND THE DIMENSIONS OF RING:
The dimensions of a ring involves the determination of following two attributes:
Diameters and Heights 1. Identification and numbering of diameters: The diameters
are classified as TOP and BOTTOM diameters. All diameters visible from the top are called TOP diameters, and ones visible from bottom are called BOTTOM diameters. In both these classifications, the biggest diameter i.e. the one calculated between the outermost edges is numbered as one. The next biggest diameter is numbered as two,and so on. This helps in standardization of identification of diameters between the user and the system.
2. Identification and numbering of heights. As explained above the heights are also classified as TOP and BOTTOM. They are numbered in descending order of their magnitude. For calculating these attributes, the profile of the rings have to be sensed both from top and bottom, the edges have to be detected and false edges have to be removed. An Edge Detection Algorithm has been developed which is explained below. Assumptions:
1. The C-arm movement is along the X-Axis, with the zero
at the home position of C-Arm, identified by Home Limit
Switch. That is, the X-Value becomes zero each time the
C-Arm reaches the home position.
2. The heights of ring profile measured by lasers, is along
the Y-Axis,with zero along the top surface of the base
plate on which, rings are placed. The sign of Y-coordinates is positive above the base plate.
l. The least count of measurement along X-Axis is 0.005mm 2. The lasers can accurately sense a variation of 0.01mm.
3. To reduce the calculation cycle time, the lasers are
made to move faster, when both the lasers, ate not seeing the measurement surfaces. When it moves f ast» it is not required to execute the edge detection logic.
4. To ensure that lasers always traverse exactly along the diameter of rings, V-Block is used. This is achieved by placing rings, touching the V-Block, tangentially.
This also ensures repeatability of placement of rings at a predetermined location on the base plate.
1. The lasers and the encoder, sense the voltage signals.
2. These are converted to distance units.
3. These units are recalcualted to fit the frame of reference,
which is explained in the assumptions.
4. When the lasers scan the measurement surface, the edge
detection algorithm, should get activated 10mm before
the first edge.
5. A sample of N points (say 100), are maintained for edge
Each sample point "p" has 3 attributes, namely,
a. X(T)(p) value, read by the encoder,
b. Y(T)(p) sensed by the Top laser.
c. Y(B)(p) sensed by the Bottom laser.
From the above, the following 8 attributes of sample (4 for top and 4 for bottom) are derived.
a. S(B/T)(Bef), where Bef indicates Before Slope i.e. Slope of first half of the sample . It is calculated as explained below:
b. S(T/B)(Aft), where Aft indicates Aftr Slope i.e.Slope
of Second half of the sample. It is calculated as explained below:
An Edge /E(T/B)(n)/ is identified by the following attributes.
a. X value at which the edge is detected.
b. Y value of the edge.
c. Y(Bef), Height of the profile, just before the edge.
d. Y(Aft), Height of the profile, just after the edge.
e. S(Bef), Slope of the profile, just before the edge.
f. S(Aft), Slope of the profile, just after the edge.
g. Angle, difference in slope of the profiles, before and
after the edge.
6. To begin with, the samples are initialized, and the edge detection logic is not executed till all the sample points are real. In each calculation cycle, the new sample point is added as the N point, and the oldest or the first point is removed from the sample. Then the Sample attributes are recalculated. Now the check for the presence of an edge in the sample is done by the following logic.
a. If H(T/B)(Bef) is different from H(T/B)(Aft),then edge is present and edge attributes are calculated as follows:
Stop the detection of edge due to slope change, till all the sample points cross this edge, i.e. till the next N calculation cycles are over.
b. If S(T/B)(Bef) is different from S(T/B) (Aft) i.e., if the slope of first half of the sample is different from that of the second half, then edge is present and the edge attributes are calculated as,
This condition persists till all the sample points cross the edge. In such case recalculate the edge attributes as
7. With this logic (which is a microscopic view), even minute modulations on the profile are sensed as edges, as a result a number of false edges are found. In order to filter out these edges, the slopes before and after all te edtes are recalculated as follows:
All those edges with less angular difference between profiles before and after them, are ignored.
8. Once false edges are removed, the Centre and Diameters
are calculated separately for both top and bottom profiles as follows.
a. Center is calculated by averaging the X value of
the extreme edges.
b. Radial distances of all the edges from the center
c. Edges are sorted out on the basis of radial
d. For all the edges before the center,a corresponding
pair is found on the other side of the center
and the distance between them on X-axis, is calculated as a diameter.
e. In this way a number of diameters are calculated
and number in descending order of their sizes.
f. These diameters are then compared with the approxi
mate diameters sent by the MMl. The most matching
diameters are sent to the MMl.
9. Similarly, the heights before and after all the edges
are recorded, and the most matching ones with the MMl
values are sent to MMl.
10. With this the measurement cycle is over, and the system
is ready for the measurement of next ring.
1. Laser Calibration: The lasers generate mill-voits,
proportional to the distance of opaque object from its source.
The Y-coordinate of measurement point with respect to the frame
of reference (as discussed in assumptions), is also linearly-
proportional to the voits generated.
Y = M(milli-voits) + C
Thus for each laser there are two constants to be determined. This is done by performing two measurements with known heights, and solving the two corresponding simultaneous linear equations involving M and C.
2. V-Block Calibration: There are two constants to be known
about the V-Block. One, the location of vertex of V-Block with
respect to home position of laser i.e. H, and two the constant
K which is a function of Angle of V-Block.
Both these constants are linearly related to the location of rings when placed touching the V-Block. Thus to determine these constants, two set of readings are taken with rings of known diameters, and solving the two simultaneous linear equations involving H and K.
3. Non-Parallelism Calibration: By natural imperfection, the laser movement is never parallel with respect to the base plate. The movement is inclined at an angle. This non-parallelism, if not accounted for, will lead to errors in both height and diameter measurements. The diameters are reduced by a factor of Cos and the heights are changed by a factor of Sin, where is the angle with which the laser movement is inclined to the base plate. This angle is found by measuring known heigts at two different locations and solving the corresponding set of simultaneous linear equations.
The invention described hereinabove is in relation to non-limiting embodiments and as defined by the accompanying claims.
1. An automatic on-line profile measurement machine (i) for measuring the profiles of hot roiled rings (14), said machine (1) comprising :
a V-block (7) placed on a machine table or base plate (10) for positioning said hot rolled ring (14);
a C-arm movable between a home position and an end position defining a measurement range;
a pair of laser sensors (4,5) mounted on said C-arm (5) for reading the Y-coordinates of the measurement points with respect to the machine table (10);
a servo motor (10') for actuating a linear movement of the ring (14) In the X-direction; and
a linear encoder for reading the linear position of the C-arm (5) and providing the X-coordinates of the measurement point with respect to home position of the laser sensors.
2. The automatic on-line profile measurement machine as claimed
In claim 1, wherein said linear encoder (11) Is configured to
provide signals of linear position of said C-arm (5) on which the
lasers (4,6) are mounted providing the X-coordinates of the measurement point.
3. The automatic on-line profile measurement machine as claimed
In claim 1, wherein two limit switches (13) are provided for
confining the movement of said C-arm (5) between the home
position and the end position within the measurement range.
4. The automatic on-line profile measurement machine as claimed
in claim 1, wherein a programmable logic controller is provided
for receiving the acquired date and determining the ring
5. The automatic on-line profile measurement machine as claimed
in claim 1, wherein a man-machine interface MMI is provided for
running a program and communication between the operator
and the PLC.
6. The automatic on-line profile measurement machine as claimed in
claim 4 or claim 5, wherein a control pendant (14') is provided for
passing on commands from the operator to said PLC.
7. An automatic on-line profile measurement machine substantially
as herein described and Illustrated in the accompanying drawings.
An automatic on-line measurement machine (1) comprising a machine base (2) , a machine table (10) provided with a roller table (3), table cooling air supply (8) and air distributor (12), said machine provided with a bottom laser (4) and a top laser (6) provided at the bottom and top of a C-Arm (5) , a V-block (7) provided at one end of said machine table (10) with a V-block adjusting handle (13) and a bottom laser window (9) provided appropriate to the V-block along the central longitudinal axis of (X-X) of the machine table (10), a linear encloder (11) provided to read the portion of the C-Arm (5) on which laser ( 4,6)) are mounted and provided with two limit switches (not shown) and a servo motor (10) for control of the movement of C-Arm (5) for measurement of a ring.
|Indian Patent Application Number||176/CAL/2001|
|PG Journal Number||09/2007|
|Date of Filing||23-Mar-2001|
|Name of Patentee||ANUP KUMAR|
|Applicant Address||TATA STEEL LIMITED, INDIA, AUTOMATION DIVISION, JAMSHEDPUR 831 007,|
|PCT International Classification Number||G 01 B 15/00|
|PCT International Application Number||N/A|
|PCT International Filing date|